I need educated about my inverter/charger

[Ray,IN]

I have a Xantrex RS 2000 inverter/charger owners manual.

here are its specifications.

I've read here and on other RVing forums, the float charge rate should be 13.3 V. The specifications for my unit state the float charge voltage is 13.5, which is the boiling point for electrolyte. My Exide 31MDC batteries failed after 14 months. At that time the float voltage was 13.6 and an alarm sounded because the batteries were at 130*F.

Exide/Camping World just warrantied my failed batteries at no charge.

Now to my questions, is there any way to adjust the float voltage in the RS 2000? The owners manual gives no indication it is adjustable.

Next question, the RS 2000 has a 3-stage charge and a 2-stage charge. The 3-stage has a float charge, the 2-stage does not, as explained on page B5. Should I change to the 2-stage setting?

Next question, which shows my ignorance about this subject. When setting the battery amperage, should it be set for total of all 3 batteries or only one? They each have a 200AH rating.

Next is charge rate. The RS 2000 has a bulk charge rate of 100A, is this too much for this battery size? It has the capability to reduce this by a percentage. Right now I have it reduced to 50%, because I remember reading charge rate should be a max. of 10% of battery capacity.

[hemsteadc]

Set the ah charge rating to the sum of all 3 batteries. 3 batteries in parallel is just one big battery in 3 pieces. Usually the charge amps can be 30% of capacity.

[Ray,IN]

Here is the Exide PDF where I got the 10% charge rate: http://www.exide.com/Media/files/Downloads/TransAmer/Battery%20Care%20and%20Maintenance/Battery%20Charging%20%26%20Storage%20Guidelines%20%205_9_13.pdf

Have I understood correctly? Set total amps to 600, 30% of which is 180A. The charger max. output is 100A, so I set it to 100% charge rate. I have 3, Exide 12V batteries @ 200AH ea., new today. If I have that right, what about the float charge rate of 13.6VDC, it is too high? What can be done to lower it to 13.3VDC if it is too high? The Xantrex owners manual only states "float charge of 13.5VDC. Then it talks about the 2-stage charge which goes from bulk to absorption charge to monitor battery condition; going further to say some battery mfgrs. do not recommend float charge for their batteries.

I just re-read that Exide PDF and noticed it recommends a float charge of 13.5-13.8VDC. Now I'm more confused about float charge rate, since the most commonly posted(on forum) float charge rate seems to be 13.3VDC.

[skp51443]

13.5 isn't an unreasonable float, it is going to use more water than a lower float voltage but shouldn't damage the batteries unless the water gets low.

 

It looks like you can adjust the voltages, see Appendix B o your manual, also you can also choose two or three stage charging. You may need to call the factory for the settings to get to the Custom charge menu.

 

When faced with an iffy inverter I've often reset it to the defaults and then gone through menu by menu setting the various options and noting what I set and why, on a printed copy of the manual.

[oldjohnt]

Hey neighbor (I'm Southwest of Bloomington, Indiana) I will offer my thoughts on your questions below:

 

1) Next question, the RS 2000 has a 3-stage charge and a 2-stage charge. The 3-stage has a float charge, the 2-stage does not, as explained on page B5. Should I change to the 2-stage setting?

 

NO I would use 3 Stage if available (preferably at settings of 14.2 to 14.4 BULK, 13.6 ABSORPTION, 13.2 to 13.3 FLOAT IF POSSIBLE???)

 

2) Next question, which shows my ignorance about this subject. When setting the battery amperage, should it be set for total of all 3 batteries or only one? They each have a 200AH rating.

 

SET IT FOR THE TOTAL OF ALL 3 BATTERIES If you have 3 Batteries in parallel, the available charging amps would (ideally if all was perfect and all batteries the same) be split 3 ways among the three batteries For example, if the charger can pump 100 amps, if all was perfect and balanced, each battery would draw 33 1/3 amps. The total Amp Hours of energy storage with three batteries in parallel each of 200 AH would be 600 AH. See http://www.smartgauge.co.uk/batt_con.html

 

 

3) Next is charge rate. The RS 2000 has a bulk charge rate of 100A, is this too much for this battery size?

 

NO in my opinion, since three batteries in parallel (if all balanced and perfect) would only draw 33 1/3 amps each AND THATS NOT TOO HIGH IN MY OPINION

 

 

4) Right now I have it reduced to 50%, because I remember reading charge rate should be a max. of 10% of battery capacity.

 

While it may need reduced for only 1 battery, you have three in parallel, so I would NOT reduce the 100 amp max bulk charge rate (only 33 1/3 each)

 

 

5) The charger max. output is 100A, so I set it to 100% charge rate. I have 3, Exide 12V batteries @ 200AH ea., new today. If I have that right, what about the float charge rate of 13.6VDC, it is too high? What can be done to lower it to 13.3VDC if it is too high

 

IN MY OPINION even though yes it will still "work" I SEE 13.6 VDC AS TOO HIGH. I prefer 13.2 to 13.3 Float Voltage. In many years of selling used RV's I saw too many batteries that sat for days at 13.5 to 13.6 volts CONSTANTLY and boiled over and lost water and were overcharged and cooked and ruined. HOWEVER that was with the older humming buzzing constant voltage source converter/chargers NOT higher tech smart chargers. Sure 13.6 works HOWEVER I would keep a close eye on water levels if your charger floats at 13.6 volts, unlike a 13.2 float which is less prone to overcharge and less risk of using too much water.

 

I see 3 stage charge levels (Both my charger and solar control use these three voltages) of 14.2 to 14.4 BULK,,,,,,,,13.6 ABSORPTION,,,,,,,,13.2 to 13.3 FLOAT what's wrong with those values??????????????? To me 13.6 is too high BUT THATS JUST MY OPINION

 

IMPORTANT NOTE for connecting batteries in parallel, it can make a HUGE difference as to how they are connected. If not balanced the three can draw different charging amps and not be balanced as far as supplying loads and charging and one might work say twice as hard as the others resulting in reduced battery life.

 

READ THIS BEFORE YOU CONNECT YOUR BATTERIES IS MY ADVICE: http://www.smartgauge.co.uk/batt_con.html

 

Im NOT a battery or charging expert, so go with manufacturer specs or other smarter gents here, but the above is still how I would do it.

 

John T Proud resident of Kirksville, Indiana

[Ray,IN]

After sitting all day with battery size set to 600 amp. hrs., the display shows voltage @ 13.6 and charge rate @ 2A. I didn't get a chance to phone Xantrex today. DW had me busy all day prepping for a garage sale the next 2 weekends. I think I'll go to the MH in a few minutes and re-set the entire system to default settings. After re-reading the owners manual, it's possible someone previously created a different profile, which altered the float voltage. It saves two settings, default and present, but that 13.6 is IMO, too high for my sealed wet batteries, and is likely the cause of my 14 month-old failed house batteries. I was elated when Camping World warranted them at NC to me.

Well, default settings is the same as my present settings except default is for 440 AH battery bank. I did read in the manual the charge rate is for all 5 batteries, 2 coach, 3 house. This means the maximum- 100A charge rate- is divided by 5, well within each batteries charge recommendations.

That made me realize my battery bank total AH rating is more than the 600 for the 3 house batteries, I need to add-in the coach batteries, right?

 

JohnT, if you get bored this weekend just head for Yoho's grocery store, you'll see our garage sale signs at the chapel, more signs and MH sitting in the drive way at bottom of hill. Apparently we'll be full-timing next year after property sells. We'll take our time buying a place in FL.

[Ray,IN]

Stan, I can't add water to my new batteries, they are sealed lead-acid. That's the main reason I'm so concerned about float voltage of 13.6. I just changed to 2-stage charging mode, bulk and absorption, the charger then monitors battery voltage until it discharges enough for bulk charge to engage again. When the charger shut off, battery voltage began dropping 1/10 V every 2 seconds, was at 12.8 when I came back in house. I'm going to check it again after posting this. I wonder if this 2-stage will be better than the float of 13.6?

Update: battery voltage just changed to 12.5 as I turned on the display. That's a drop from 13.6 @ 7:30PM in 3 hours.

[skp51443]

I should have googled your battery, I never even considered it might be a sealed type.

 

Normally your inverter/charger will not be connected to the chassis batteries and they are not considered as part of the calculations for the settings of the inverter charger.

 

This data sheet for the 31MDC doesn't show them as sealed though. You really need to confirm that as it makes a big difference!

 

Considering them as normal flooded batteries this section applies:

 

I'd also use the 20 hour amp hour rating of 115 instead of 200 for calculating the charge rate. The sheet below suggests this for charging For C20=115Ahr, the max charge current is 11.5x5A or 57.5A each so for your three it would be 172.5 Amps. Over your maximum charging ability so leaving it at max won't damage things although it will use more water than a lower setting like C10 or 86 Amps which is also good for battery life even if it does add a bit to the charging cycle's time. Your maximum charge rate makes this a bit moot since you can't go past 100 Amps in any case.

 

They are showing a Float voltage of 13.5 – 13.8 V on the data sheet so your current setting sounds reasonable.

 

http://www.showmetheparts.com/BIN/documents/EXIDE/Battery%20Specification%20Sheet%2031MDC.PDF

 

Min Ref. Ah Capacity 20HR 115 Ah

Float voltage (27°C / 80°F) 13.5 – 13.8 V

Cycling voltage (27°C / 80°F) 14.5 – 14.9 V

Battery type Flooded

Positive grid alloy Lead Antimony

 

From the sheet here and the line above that says the plates are Lead Antimony I'd use the middle row of settings.

 

http://www.exide.com/Media/files/Downloads/TransAmer/Battery%20Care%20and%20Maintenance/Battery%20Charging%20%26%20Storage%20Guidelines%20%205_9_13.pdf

 

Flooded/Wet Deep Cycle & Marine (Antimony) Exide Marine Deep Cycle Exide Special Heavy Duty and Floor Scrubber

 

Charge at a constant current rate of no more than 10 times I20 to a voltage of 14.7V (example; For C20=100Ahr, the max charge current is 10x5A or 50A). Charge with 14.7V - 14.9V limit for 12 to 24 hrs or when current drops below 1% of the C20 rating (example; C20=100Ahr, the low current shut off is 1%x 100 or 1A). 13.2v - 13.4v

 

Charge voltage on point - 12.60v Charge voltage off point - 13.2v

 

Limit current to 0.4 times I20

 

Charging Temperature Compensation: All the listed charging voltages are appropriate for a temperature range of 15-25ºC (68-77ºF). For average operating temperatures below this range (colder than) the maximum voltage set point should be compensated with an increase at a rate of 0.063 Volts Per Cell (0.38 Volts for a 12 v battery) for every 10ºC (18º F.) For average operating temperatures above this range (warmer than) the maximum voltage set point should be compensated with a decrease at a rate of 0.063 Volts Per Cell (0.38 Volts for a 12v battery) for every 10ºC (18º F.) Example: at 95ºF and 14.2 volt set point Corrected Voltage = 14.2 + (((95- 77)/18) x (0.38)) = 14.58 volts

 

--------------------------

 

If they are really sealed then this applies:

Sealed flooded batteries in an RV system with an inverter doesn't usually go well, water use and early death is something I'd expect. I'd drop the charging amps WAY down on them, C5 or so as they are not going to deal well with gassing while charging. I'd also think you'd want to drop the voltage set points below what you have and the data sheet recommends to limit water use but the data sheet numbers really leads me to suspect they aren't actually sealed or there is a confusion issue about just which batteries they are.

[oldjohnt]

Ray, The good Stanely man has you well covered complete with specs it sounds like. I may wander over to Yohos and say howdy. I'm sure you know some of the Sullivans I play music with sometimes. We winter around Sebring Florida but attend three antique tractor shows (Flywheelers and Zolfo Springs) plus attend 3 Bluegrass festivals so were on the go quite a bit.

 

Don't let me buy anything lol, were trying to get rid of "stuff" and downsize to do more RV travel ourselves >>>>>>>>>>>>>>

 

PS 12.6 volts is a full charged battery, if you're dropping down to 12.5 that fast, sure there isn't some sort of a bleed or phantom load, 12.5 (if readings are accurate) is a bit discharged.

 

My chargers have adjustable settings for Flooded lead Acid or Sealed or AGM, does yours have such??????

 

Sure your Inverter/Charger charges your engine battery as well as house batteries?????????

 

John T

[Ray,IN]

Thanks Stan for your research and advice, it'll take me a while to understand everything you said, including the links. I just checked house battery voltage and it was back to 12.6V @ 86 deg. with charger off, it's merely monitoring presently, according to the manual. I think the V drop to 12.5 was due to ambient temperature drop into the 50's. The house batteres are Exide 200AH, and chassis batteries are 195AH Interstates, all 5 are sealed lead/acid.

I haven't had a chance to phone Xantrex yet about adjusting float voltage, the manual does not indicate it is user-adjustable.

 

Smitty it does charge/maintain the chassis batteries through the BIRD relay, IF I read the electrical schematic correctly. Anyway, chassis batteries have never been low or discharged since we've owned the MH. I'll be glad to meet you. I won't have much talking time though. DW fell off a ladder last evening, and this morning her knee was swollen and stiff. Took her to Dr. this morning and nothing is broken, she is wearing a knee brace for a few weeks, which is helping her get around.

 

Guys,

I'm still grasping how the 2-stage charger works in reality, compared to what the manual says. My understanding is, it bulk charges to a set point, then goes to absorption mode until batteries reach fully-charged, then charger switches off and monitors battery voltage. The manual does not state what it monitors for, low voltage I assume, but at what point does it become active again?

I think I should switch back to 3-stage charging for the float, despite the 12.6 rate; as I feel allowing batteries to sit at less than fully-charged may be more harmful in the end.

[oldjohnt]

Ray, to your statement above "I think I should switch back to 3-stage charging for the float, despite the 12.6 rate; as I feel allowing batteries to sit at less than fully-charged may be more harmful in the end".

 

Did you mean 13.6 volts instead of 12.6????????????

 

I would agree allowing a battery to sit for long periods in a discharge state may be worse then floating them at 13.6 volts PROVIDED YOU KEEP THE WATER LEVELS FROM FALLING BELOW THE PLATES. I still prefer 13.2 or 13.4 volts float (versus 13.6) as theres less chance of water getting too low!!!!!!!!!!!!!! But if you cant set it for a lower float so be it, just keep an eye on water level (But I forgot you have sealed batteries, OOPS my bad)

 

John T

[Ray,IN]

Good catch! Yes, I meant to type 13.6V. Sure fat-fingered that one. Monday I'll phone Xantrex (in Canada) and ask about lowering float voltage to 13.3.

Since Exide states float voltage is 13.5 - 13.8, perhaps I'm overthinking this, but everything I've read from knowledgeable folks here and other RVing forums says 13.3. Then there is the "ripple wave-form" as described in the above link, that should not exceed +/- 5% of charging voltage; this somewhat fits my battery situation. I have replaced house batteries at the 14 month mark ever since we bought the MH. Thankfully, this time it was at NC to us.

The first batteries were Interstate, sealed, 195AH, second were Exide 115AH with normal cell caps. Current are as described previously, and I don't want to kill them.

I'm going to cut the charge rate to 50%, which is 50A max. as Stan wrote. It can't hurt anything, can it?

[oldjohnt]

"It can't hurt anything, can it?"

 

TRUE, however if the charger can deliver max 100 amps to three batteries in parallel, if all is matched and balanced (see my Smart Gauge Parallel Connection page linked above) that's only 33 1/3 amps per battery. (if it also connects to engine batteries, that's even less amps per battery) The 50% rate wont hurt, just that it takes longer to charge the batteries but that might not matter in your situation.

 

The first wife has me doing chores today so I may not catch you at Solsberry.

 

Your neighbor, John T

[Ray,IN]

The battery bank has been floating at 13.6/7 for 2 days now, the temperature on the center battery appears to be staying a few degrees above ambient temperature. DW is beginning to think I'm a bit off, since I go check on them 3 or 4 times a day. (she may be right_) I haven't found time to phone Xantrex yet, this garage sale thing is killing me, sure be glad when this 3-day weekend is over. The upside is, DW made $1,000 last weekend.

[oldjohnt]

Ray, subject to battery charge state and loads, my four Six Volt Flooded Lead Acid Batteries (series parallel for 460 Amp Hours) may set at my chargers 13.6 volt ABSORPTION level (PD 60 Amp Smart 4 State Charger) for a few days BEFORE the charger backs off to 13.2 FLOAT, therefore, the 2 days you report AT 13.6 DOES NOT SCARE OR SURPRISE ME ONE BIT.

 

Again, with a 100 amp max charger divided (if approx. equal) among 3 or 4 batteries in parallel (say 33 1/3 amps each), I see no problems using its 100% rate, BUT THATS YOUR CALL NOT OURS. 50% rate WONT HURT, it just takes longer to fully charge if that matters????

 

Again, I still prefer a FLOAT charge rate of around 13.2 volts (especially for flooded lead acid so they don't use so much water), and view 13.6 volts as a bit high to float, but that's your call after you talk to Xantrex. I prefer around 14.4+ for BULK. 13.6 for ABSORPTION, 13.2 for FLOAT but that's just me for flooded lead acid. DO AS YOU PLEASE.

 

Hope to meet up someday since were so close

 

John T Kirksville, Indiana

[Jack Mayer]

A flooded cell battery should be charged at 14.8 volts (temp corrected) unless the manufacturer says otherwise.

[Rif]

And, when Jack says charged at 14.8, he means both the bulk and the absorb stages. Absorb voltage of 13.6 will never fully charge the battery.

[oldjohnt]

Rif, I agree with your statement " Absorb voltage of 13.6 will never fully charge the battery."

THATS WHY all the so called "Smart" 3 or 4 Stage Chargers start out at an initial BULK CHARGE voltage of 14+ BEFORE they slow down to the ABSORPTION CHARGE in the 13.6 + or - volt range. The Initial higher voltage BULK CHARGE first brings the battery up to a certain state of charge before it backs off to the lower ABSORPTION and FLOAT charging voltages. A Smart Charger does NOT sit there INDEFINITELY on and on and on (subject to load and battery and and charge state) at 14+ volts once a certain state of charge is achieved. They utilize 3 or 4 stages.

 

OF COURSE if you just let a flooded lead acid battery set there indefinitely at 14+ charging volts, water would eventually have to be replenished which is "one" reason the Smart Chargers use the three progressively lower stages of charging. That way the battery gets fully and properly charged prior to the lower maintenance charge cycles. I would NEVER go back to the old style "Dumb" more like constant voltage chargers. Others are free to do so as they are indeed cheaper to purchase.

 

PS just as UNDER charging can be harmful to a battery, so can OVER Charging. I have seen many batteries cooked and boiled and ruined by being kept on high volt high amp charges for much too long time periods. They can bubble out their water and perhaps plates even becoming warped if placed constantly under excessive high amp charging............Ive even seen that happen on old tractors with relatively low energy generators (maybe 20 to 30 maps max) let alone 100 amp high energy chargers. Charge YES but OVER charge NO...........

 

John T

[Rif]

John, With all due respect, while there may be some chargers that work like you describe, your description about how a quality battery charger works is not accurate. You say that Smart Chargers use three progressively lower stages of charging. That is not correct. At least it is not correct as far as any of the good quality chargers I am aware of. For example, my Magnum 2800 Inverter/Charger has two voltage settings for charging, plus a voltage setting for equalizing. The two charging voltages are Absorb and Float. There is no setting for Bulk because it is the same as Absorb. In fact, during the bulk charging cycle, the voltage will be something less than the absorb voltage. My Outback solar controller has the exact same settings. The Bulk and Absorb voltages are one and the same.

 

Here is a description of how it works, copied from the user manual for my inverter:

 

Bulk Charging: This is the initial stage of charging. While Bulk Charging, the charger supplies
the battery with controlled constant current. The charger will remain in Bulk charge until the
Absorption charge voltage (determined by the Battery Type selection*) is achieved. The inverter’s
green LED stays ON (solid) to indicate Bulk charging.
Absorb Charging: This is the second charging stage and begins after the absorb voltage has
been reached. Absorb Charging provides the batteries with a constant voltage and reduces the
DC charging current in order to maintain the absorb voltage setting. The inverter’s green LED
flashes once every second (fast flash) to indicate absorption charging for 2 hours (determined by
the Battery AmpHrs selection*), then switches to Float Charging.

The key is that during the bulk charge portion of the cycle, the voltage will be less than the absorb voltage because the batteries are accepting all the current the charger can supply. Once the batteries reach a point at which they cannot accept all the current, the voltage will begin to rise. When it reaches the absorb set point, the charger enters the absorb cycle and holds the voltage constant by reducing the amperage to the maximum the batteries will accept at that voltage. The amperage will continue to drop as more charge is forced into the batteries until they become fully charged. That is the point at which the charger drops the voltage to its Float setting. Float is not really charging. It is merely a voltage that will keep a battery from discharging. Very little if any current actually flows during float.

 

I didn't say to hold the voltage at 14.8 indefinitely, but it should be held there through the entire absorb cycle. Once the battery will accept only approximately 2 percent of its rated capacity, it is fully charged and the voltage should then be lowered to the float value. For example, if a battery bank is rated at 400 amp hours, it should be charged at 14.8 until it will accept no more than 8 amps at 14.8 volts. Then the voltage should be lowered to 13.2 or so for float. Of course, to do this you need a meter that shows the amps flowing into and out of a battery, something like a Tri-Metric, or a very good charger that allow the setting of an End Amps value for ending the absorb cycle. My Outback solar charge controller has this capability. Chargers that do not have an End Amps setting usually use time or some other internal algorithm to determine when to lower the voltage to the float setting. As you can see from the Magnum manual, they use an absorb cycle of 2 hours instead of an End Amps value. Depending on the beginning charge level of the battery bank, this may be too long or too short, but it's a reasonable approximation and will work OK in most cases.

[skp51443]

Might be some confusion here on voltages, the voltages that you set in the charger are not charging voltages, instead they are set-point voltages. A set-point voltage is where when the charger detects the battery bank is at that voltage it changes to the next charging mode.

 

So in bulk charge you may see the charger putting out 10.5 volts, seems strange but if that is all the voltage needed to take the charging current to the limits you have set in the charger's computer that is all you'll see. As the batteries charge they will require more voltage to force the allowed level of current into the battery so you'll see the voltage rise. If there were no set-point the battery would stay in bulk charge until it melted! Instead when the charger sees the battery voltage rise to equal the set-point voltage the charger switches from bulk to absorption mode. Same happens in absorption mode, charger watches battery voltage and when it reaches the set-point the charger switches to the next mode and floats the battery.

[Rif]

Stan, I agree with everything except the last sentence. Educate me. During the absorb stage, the voltage is held constant. The only thing that changes is the current. It is held for a pre-determined length of time, or until the current flow drops to a pre-determined level, depending on the capabilities of the charger. How can the charger use voltage to determine when to end the absorb stage when the voltage is held constant. No matter where you measure it in the circuit, it is the same. I see no way that the charger could determine the battery voltage.

[oldjohnt]

Rif, Meaning no disrespect, I'm here to HELP people NOT argue lol I must take issue with your statement regarding my post above:

 

"your description about how a quality battery charger works is not accurate. You say that Smart Chargers use three progressively lower stages of charging. That is not correct."

 

NOTE, Yes I realize you indeed said " while there may be some chargers that work like you describe" Thank you, and I have described those "some" below. It appears your TWO STAGE Inverter/Charger functions different then the many other quality Three Stage Chargers out there, so hopefully our friendly discussion will help educate some of the other good gents who visit the site!!!!!!!!!!!!!!!!

 

I maintain I AM CORRECT and offer the following as evidence in support of my claim. NOTE I consider brands such as Xantrex and Progressive Dynamics as a "quality battery charger" I own both of those chargers and for the past years the digital voltmeter on my house battery bank registers EXACTLY what I described for Smart Three Stage Charging, namely Initially 14.4+ BULK,,,,,,,,Later it slows down to 13.6 ABSORPTION,,,,,,,,,,,,,Later it slows down further to 13.2 FLOAT. Those actual real time voltage readings correspond EXACTLY as I described (which you say is not correct for "some" at least lol) and EXACTLY as Smart Three Stage Charging works as described by Progressive Dynamics and Xantrex or independent sources below:

 

NOTE I think a more accurate statement from you would have been "I am CORRECT regarding Xantrex, Progressive Dynamics and other Three Stage Chargers, while you are correct regarding your only Two Stage Magnum Inverter Charger"

 

 

MY EVIDENCE TO SUPPORT MY CLAIM THAT I WAS INDEED CORRECT

 

Lets see what three different sources have to say about three stage charging BULK ABSORPTION AND FLOAT and how they indeed "use three progressively lower stages of charging" as I stated (which you say is not correct)

 

1) Taken form Battery Stuff Website:

 

"You may have heard it said "you need a 3 stage charger". We've said it, and we'll say it again. The best kind of charger to use on your battery is a 3 stage charger. They are also called "smart chargers" or "micro processor controlled chargers". Basically, these types of chargers are safe, easy to use, and will not overcharge your battery. Almost all of the chargers we sell are 3 stage chargers."

Okay, so it's hard to deny that 3 stage chargers work and they work well. But here's the million dollar question: What are the 3 stages? What makes these chargers so different and efficient? Is it really worth it? Lets find out by going through each stage, one by one.

 

Stage 1 | Bulk Charge

The primary purpose of a battery charger is to recharge a battery. This first stage is typically where the highest voltage and amperage the charger is rated for will actually be used. The level of charge that can be applied without overheating the battery is known as the battery's natural absorption rate. For a typical 12 volt AGM battery, the charging voltage going into a battery will reach 14.6-14.8 volts, while flooded batteries can be even higher. For the gel battery, the voltage should be no more than 14.2-14.3 volts. If the charger is a 10 amp charger, and if the battery resistance allows for it, the charger will put out a full 10 amps. This stage will recharge batteries that are severely drained. There is no risk of overcharging in this stage because the battery hasn't even reached full yet.

 

Stage 2 | Absorption Charge

Smart chargers will detect voltage and resistance from the battery prior to charging. After reading the battery the charger determines which stage to properly charge at. Once the battery has reached 80%* state of charge, the charger will enter the absorption stage. At this point most chargers will maintain a steady voltage, while the amperage declines. The lower current going into the battery safely brings up the charge on the battery without overheating it......................The current continuously declines until the battery almost reaches full capacity.

 

Stage 3 | Float Charge

Some chargers enter float mode as early as 85% state of charge but others begin closer to 95%. Either way, the float stage brings the battery all the way through and maintains the 100% state of charge. The voltage will taper down and maintain at a steady 13.2-13.4 volts, which is the maximum voltage a 12 volt battery can hold. The current will also decrease to a point where it's considered a trickle. That's where the term "trickle charger" comes from. It's essentially the float stage where there is charge going into the battery at all times, but only at a safe rate to ensure a full state of charge and nothing more. Most smart chargers do not turn off at this point, yet it is completely safe to leave a battery in float mode for months to even years at a time.

 

SOURCE: http://www.batterystuff.com/blog/3-stages-of-smart-chargers.html

 

LOOKS LIKE I WAS CORRECT

 

2) RV Doctor 3 Stage Charger Description (talks about Xantrex Truchharge2 Chargers)

 

"Another key to proper battery optimization is multi-stage charging. The three charging stages produced by the Truecharge2 are:

 

· Bulk stage

· Absorption stage

· Float stage

 

A fourth available process, Equalization, is applicable to liquid-filled batteries only (flooded lead-acid and lead-calcium). Another nice function of the Truecharge2 is the ability of the user to choose between three-stage charging and two-stage charging (eliminating the Float stage).

 

During the Bulk stage, the charger delivers its maximum current output in a constant fashion; full amps flowing into the battery bank. All batteries store current, measured in amps. Once the battery voltage reaches a pre-set point (remember, it’s a different requirement for each of the battery types), it switches to the Absorption stage.

 

In the Absorption stage, the Truecharge2 holds the voltage steady at a set rate as the current flow lessens. Once the battery reaches its gassing threshold, (again, a different voltage level for each type of battery), the charger switches to the Float stage.

 

During the Float stage, the Truecharge2 delivers a lesser amount of voltage to maintain the battery bank in a charged condition until the bank voltage drops below 12.5 volts for about fifteen minutes. Then it awakens and enters the Bulk stage and the process continues.

 

SOURCE: http://www.rvdoctor.com/2011/03/product-spotlight-xantrex-truecharge2.html

 

 

LOOKS LIKE I WAS CORRECT

 

 

3) Progressive Dynamics Four Stage Smart Charger

 

“Our patented Charge Wizard…….constantly monitors battery voltage and battery usage then selects one of the following four operating modes to properly charge and maintain the battery.”

BOOST Mode 14.4 Volts - Rapidly brings the RV battery up to 90% of full charge.

NORMAL Mode 13.6 Volts - Safely completes the charge.

STORAGE Mode 13.2 Volts - Maintains charge with minimal gassing or water loss.

EQUALIZATION Mode 14.4 Volts - Every 21 hours for a period of 15 minutes prevents battery stratification & sulfation - the leading cause of battery failure.

 

The Battery Recharge Curves chart (below) shows the amount of time it took a PD9155 (55-amp) converter set to three different output voltages to recharge a 125 AH (Amp Hour) battery after it was fully discharged to 10.5-volts.

• 14.4-VOLTS (Boost Mode) – Returned the battery to 90% of full charge in approximately 3-hours. The battery reached full charge in approximately 11 hours.
• 13.6-VOLTS (Normal Mode) – Required 40-hours to return the battery to 90% of full charge and 78-hours to reach full charge.
• 13.2-VOLTS (Storage Mode) – Required 60-hours to return the battery to 90% of full charge and 100-hours to reach full charge.

 

LOOKS LIKE I WAS CORRECT

 

SOURCE: See http://progressivedyn.com/charge_wizard.html

 

4) MY ACTUAL EXPERIENCE WITH THE XANTREX AND PROGRESSIVE DYNAMCIS CHARGERS HAS BEEN (I have a digital voltmeter on my house battery bank and over the past 3 years here is what it has read: Initially 14.2 to 14.4+Volts,,,,,,,,,,,Later 13.6 volts,,,,,,,,,,,Later 13.2 volts)

 

 

 

I REST MY CASE LOL

 

Thanks Rif, fun discussion, you may be right about how your Two Stage Inverter/Charger works BUT I AM RIGHT AS ESTABLISHED ABOVE about how my Smart Three Stage Chargers (Progressive Dynamics & Xantrex)

 

Best wishes and God Bless, take care now

 

John T BSEE, JD Retired Electrical Engineer and Attorney at Law

[skp51443]

Stan, I agree with everything except the last sentence. Educate me. During the absorb stage, the voltage is held constant. The only thing that changes is the current. It is held for a pre-determined length of time, or until the current flow drops to a pre-determined level, depending on the capabilities of the charger. How can the charger use voltage to determine when to end the absorb stage when the voltage is held constant. No matter where you measure it in the circuit, it is the same. I see no way that the charger could determine the battery voltage.

 

I went back and re-read a couple charger manuals and I think I did get the last bit wrong, from what I see in current charging systems they either use a timer of some sort or monitor the amps for the absorption / float transition, not the voltage.

[Rif]

John, Indeed this will make for a fun discussion. Perhaps we will all learn something from it, however, if we are going to determine who is right or wrong based on the number of words in the post, I cede to you. There's no way I am going to compete with an attorney in that regard. ON EDIT: Hey, maybe I did beat you there. I kind of got carried away.

 

That said, perhaps you misunderstood or are not familiar with the chargers I mentioned. I am very familiar with the two you refer to because too because I owned a good Xantrex (Freedom 458) inverter/charger for many years, and I still own a Progressive Dynamics 60 amp converter with Charge Wizzard (same as yours). The Xantrex was a very good 4 stage charger, and the PD with Charge Wizzard is a decent, though unsophisticated and somewhat lacking charger when compared with the Xantrex or with either of the other charges I have. You seem to be under the impression that the Magnum inverter/charger and Outback solar controller I have are some inferior 2 stage chargers. They are not. I never said they were 2 stage chargers. I said that there are only two settable voltages for the charge cycle. In fact, both are state of the art 4 stage chargers.

 

The Magnum is one of, if not the best, pure sine wave inverter/chargers on the market today for RV use. It is by far the most frequently recommended inverter/charger by the experts on this forum and others. My Outback solar controller is also a highly sophisticated 4 stage charger. When I purchased it about 8 years ago it was the best one available. Today most experts recommend the Midnight Solar brand or the Outback for larger solar systems like mine (800 watts). Both of these chargers have very sophisticated micro processors and an incredible array of configuration options. Both have temperature correction sensors. IMHO, both are superior to either the Xantrex I had, or the PD I still have.

 

My disagreement with your original post was regarding absorb voltage. You said it should be 13.6. I said it should be 14.8. Ignoring your 3rd citation from PD for a moment, because the PD is a completely different animal, both the first and the second quotes do not support your statement. They both say that during the absorb stage, the voltage is held constant and the current is reduced. They do not specify what that voltage is, but it is implied. I think the RV Dr. (Gary Bunzer) does a decent job of explaining when he says that during the Bulk stage, the maximum current the charger is capable of is applied. (This is not technically correct because the current should be limited to C/5 or less, but that's for another discussion.) He then says that once the voltage reaches a pre-set point, the charger enters the absorb stage. That point is the absorb voltage. It is the maximum voltage that should be applied to the battery during normal charging. When it reaches that voltage, the current is reduced, but the voltage is not. It is held constant throughout the absorb stage.

 

Read what I quoted from the manual for the Magnum inverter, which does a better job of explaining it than either of us or the quotes you cited.

 

Bulk Charging: This is the initial stage of charging. While Bulk Charging, the charger supplies
the battery with controlled constant current. The charger will remain in Bulk charge until the
Absorption charge voltage is achieved.

Absorb Charging: This is the second charging stage and begins after the absorb voltage has
been reached. Absorb Charging provides the batteries with a constant voltage and reduces the
DC charging current in order to maintain the absorb voltage setting.

 

This description is much clearer than any of your citations because it clearly shows that during the bulk charge, the voltage will be below the absorb set point. It also clearly states that once the voltage rises to the absorb set point, it is held there throughout the absorb stage, and the current is reduced.

 

As I said in my previous post, both my chargers have only 2 voltages that can be set for a normal charge profile. (In fact, because they are so sophisticated they have many others that are not germane to this discussion at this point.) The two voltages are the Absorb voltage, and the Float voltage. As both your citation 1 and 2 describe, during the bulk stage maximum current is applied until the voltage reaches the absorb voltage. At that point the absorb voltage is held and the current is reduced. It is held until the battery reaches full (again definable in my chargers) and then it drops the voltage to the float value. Although it is a 4 stage charger, there are only two setable voltages for a normal charge cycle, and a third for the equalize cycle (which is another discussion altogether.)

 

I think what may be confusing the issue here is including the PD converter with Charge Wizzard in the discussion. Frankly, it is not a great charger, but is is much better than a regular converter. It does a decent job of charging batteries, though not nearly as good as your Xantrex or either of my true 4 stage chargers. I say this for several reasons. First, the voltage settings are not adjustable. Second, the "Boost" voltage is not high enough. Third, the "Normal" voltage is too high. In addition, it just does some funny things that are not at all the way most high quality chargers work. Again, having a Charge Wizzard on your PD converter is far better than having one without, but it is a far cry from a quality 4 stage charger. Consider that they do not even describe their three modes as stages, nor ever use the term bulk, absorb or float. They call it "Boost", "Normal", and "Storage", and if you read what these modes are, how they select them, and how they determine the length of each, you will see what I mean. They don't really have bulk, absorb or float functions. Essentially what I am saying is, don't include a PD with Charge Wizzard in a discussion of quality 4 stage chargers.

 

If you are postulating that 13.6 is a proper absorb voltage based on what you see with the PD, then that explains it. IMO, the PD with Charge Wizzard is not even a 3 stage charger. It's something else altogether. I would, however, like to know which Xantrex inverter/charger you have. I have never seen one that acted like the PD. My Xantrex worked exactly like my Magnum. Still, I have never seen a Xantrex that used an absorb voltage of 13.6, and certainly I never saw one that dropped to that value once the bulk charge voltage reached the absorb set point. Every one I have ever seen held the absorb voltage for some period of time before lowering it to float. If yours is doing that, it need to be fixed because you will never get your batteries fully charged unless you are plugged into power most of the time. Could that be true in your case? Do you ever spend time off grid? If you are plugged into power all the time, float is probably the only voltage you would ever see.

 

I certainly do not mean any disrespect, John. I and everyone else on the forum appreciates your expertise and your credentials as listed in your signature. However, I'm not without my own area of expertise, and that is RV systems. I have been a full timer for 16 years now, and an active participant in the forum for most of that time. I installed my first solar system in 2006 and have installed several since then. I've installed converters, transfer switches, generators, inverters, battery monitors, electrical management systems, and many more electrical devices. I've been an active boondocker for a good part of every year, and relied on my solar charger, inverter and battery systems very heavily. I've been involved in hundreds of technical discussions on this forum and others regarding solar systems, batteries, inverters, and charging systems to name a few. While I'm not an electrical engineer, I know RV electrical systems, batteries and chargers, and an absorb voltage of 13.6 is just wrong for lead acid batteries.

 

Jack was a lot more succinct that I was. He simply said "A flooded cell battery should be charged at 14.8 volts (temp corrected) unless the manufacturer says otherwise."

 

 

ON EDIT: Read how Xantrex describes multi stage charging. They do a good job of explaining it clearly.

 

http://www.xantrex.com/documents/tech-doctor/universal/tech7-universal_v2.pdf

-----------------

 

One thing I need to point out is that the voltages mentioned here refer only to regular lead acid batteries. AGM and Gel batteries have different charging characteristics and concerns.

[oldjohnt]

^{Rif, indeed its been a fun and friendly discussion and hopefully we have helped others learn (or bored them to death lol) Hey you are as wordy as me lol. I have done more then my share of BOTH technical and legal writing and can get wordy also..................}

 

 

^{BOTTOM LINE 1) Your description describes how your Magnum Inverter Charger works.}

^{2) My description described how Smart Three Stage Chargers work and was "correct" in}

^{regards to my original posting regarding their basic operation as established by the three}

^{sources I included.}

^{3) I would say we were BOTH correct, you about Magnum Inverter/Charger, me about Three}

^{Stage Chargers (UNLESS the manufacturers information I posted is incorrect, what I posted}

^{is THEIR THEORY NOT MINE, take that up or argue with them, but I doubt they will change}

^{their engineering design based on what you or I have to say, regardless if we were}

^{electrical engineers or not).}

 

^{Tell you what, in my many years of electrical engineering and legal practice I learned to NEVER SAY NEVER AND NEVER SAY ALWAYS OR MAKE A BLANKET STATEMENT SOMEONE IS INCORRECT because it will come back to bite you everytime lol}

 

^{As I recall Trojan Battery is one among other battery manufacturers who recommend an initial charge rate of 14.8 volts, and Trojan and the other battery manufacturers likely know a wholeeeeeeee lot more about batteries then you or I or anyone here.}

 

^{NOTE, speaking of Trojan, Id consider them experts well above and beyond me or anyone here, and here's what Trojan has to say about battery charging, this was taken from their website, its their words NOT mine, take or leave it at your own peril:}

^{"Trojan recommends using a 3-stage charger. Also called “automatic”, “smart” or “IEI” chargers, which prolong battery life with their programmed charging profile. These chargers usually have three distinct charging stages: bulk, acceptance, and float."}

^{See: http://www.trojanbattery.com/tech-support/battery-maintenance/}

 

 

 

 

^{Like you I have owned, bought and sold, RV's for over forty years plus worked on them myself using my electrical engineers expertise, and for sure the modern Three Stage so called "Smart" progressive rate chargers SURE BEAT THE OLD NOISY HOT BUZZING NEAR CONSTANT VOLTAGE SOURCE CONVERTER/CHARGERS.}

 

^{Take care yall, best wishes and God Bless, I appreciate your and others help and expertise here}

 

^{John T (counting the days before we head out in the RV to Monument Valley, Grand Canyon, Zion, Yosemite, Kings Canyon and Sequoia woooooooooooo hoooooooooooo) YES I do a ton of extended off grid dry camping and put my Batteries, Solar Panels and Smart 3/4 Stage Solar Charge Controller plus (when plugged in) my Smart Three Stage Charger to good use.}