6 Volt Battery Bank in Series/Parallel Charging

[Risenterror]

We have a campsite at a campground with permanently assigned sites. The campground has no power so I setup a bank of 4 6v Costco(interstate batteries) batteries in series parallel to run an inverter and some 12v led lighting.  I have a 3amp/15amp Schumacher charger that I can plug in to my campers generator.  I also have an 80w solarpanel 15amp charger and controller that I can use while not there but the amount of direct sun the the trees is not great, so there will be a lot of indirect light.

My questions are, is my charger good enough to charge the batteries up fully during the day when generators are allowed and how accurate is the % display of the chargers using a battery bank?  This weekend I ran it all day and it said it gained about 7% charge and was at 72%.  An hour later it reported 100% charge. 

Second is during the week while I am gone the only draw on the batteries will be a Norcold Propane fridge that requires 12v for the board and sensors.  Will the solar panel be enough to keep up with the fridge?

There isn't a period of time that I am not drawing on the batteries to let them sit 12 hours to get a reading with a volt meter so I am not sure what to do to figure out what charge they have if the charger isn't accurate.

[oldjohnt]

Great questions, lets work through the math just a bit for starters but I have to make a few guesses and approximations absent any detailed specs so don't anyone have a calf now or pick this too hard ITS ONLY AN APPROXIMATION....but I think this exercise may help the poster figure things out

1) My best guess is the four 6 volt batteries can provide somewhere 400 Amp Hours of energy storage (My 4 Trojans are 450) and you don't want to discharge more then 200 Amp Hours out of them. I don't like to draw down much over 30% or 20% even better

2) SOLAR under ideal bright direct overhead sun (which is nowhere near what you get over an average day) the best charge rate you can get from an 80 watt solar panel into 12 volt batteries is around  6 amps and EVEN IF you harvested say 6 amps for say 6 hours THATS ONLY 36 AMP HOURS and in reality subject to sun and time and since you mention trees, YOU MAY BE LUCKY TO HARVEST 20 to 25 AMP HOURS MAXXXXXXXXXXX

3) 15 Amp Charger: Lets say you ran that 15 amp charger 8 hours, that's 120 Amp Hours of energy you could theoretically pump into the batteries BUT subject to the charger and its controls and charging algorithm IE it likely will NOT deliver 15 amps into the batteries for 8 hours.

4) OKAY if BOTH the solar and charger ran 8 hours per day, I don't envision harvesting much over 140 Amp Hours or less subject to how much sun for how long and the charger controls.

5) Of course batteries and chargers aren't 100% efficient, IE it requires MORE input energy to replenish them versus what you draw down overnight.

6) THEREFORE as long as you don't consume more then 140 amp hours of battery energy storage on a given day you can replenish them by running your charger 8 hours and harvesting solar all day.

7) How much is 140 Amp Hours ?? If all the lights (assuming LED) and fridge drew lets use say 5 amps for 10 hours, there's 50 Amp Hours, but how much power do you draw from the Inverter???? A relatively small 120 watt 1 amp at 120 VAC load requires a bit over 10 amps from the batteries, so one hour of operating such a load requires 10 Amp Hours per hour IE 4 hours requires 40 amp hours from the batteries. IFFFFFF that was all the inverter powered ???? you're up to 90 amp hours total with lights and fridge and Inverter use.

That generator may consume 2 to 3 quarts per hour of gasoline, subject to load and its size and efficiency, factor that into your equation!!

FYI A full charged battery at rest stabilized at 77 degrees would read around 12.63 volts full charged, 12.30 volts at 75% charged, 12.00 volts at 50 % charged AND I WOULD T LIKE TO DRAW DOWN MUCH MORE

Can 80 watts of solar keep up with the fridge you ask?? If the fridge consumes not much over 20 amp hours per day YES it might subject to sun and fridges current draw. If it requires say 1 amp for 24 hours, you're getting close, but if it draws 2 amps the 80 solar watts cant keep up subject to sunlight and hours of it.  

YOU NEED AN ENERGY AUDIT to see what your daily energy requirements are and ONLY then can you calculate if your charger and solar can keep up, but this exercise should help you figure it all out.

SUGGESTIONS: Things I might consider are 1) Invests in at least a 20 amp better yet a 40 amp Smart 3/4 Stage quality charger and 2) Bump that solar up to at least 100 better 200 watts and then you have a god chance of keeping up PLUS your batteries will thank you and repay you with more hours of life.

 

ONLY TO PROVIDE A ROADMAP

 

John T

     

[Yarome]

Let's hit the 80 watt panel first and talk ah's (amp hours). Your 4-6V cells likely have a total capacity of 440ah's. Your 80 watt solar panel can produce, under the very best of circumstances and at 100% efficiency, 6.6 amps. If you were to use.. say.. 200ah's of your batteries capacity during a weekend trip, it would require, under the best of circumstances, 30.3 hours of solar generation. Approximating 4 hours max of solar generation per day (which isn't likely), it would require approximately 8 days of 100% solar generation to refill those 200ah's used. In real life, that number could very well be at least double to quadruple or more.

For all intents and purposed, it is sufficient to maintain battery levels (with a battery disconnect), and will help suplements your energy usage while camping, but not very practical as an actual charging source.

Get one thing straight though... "any" free energy is a good thing and having the ability to maintain your batteries charge levels when absent for long periods is a massive plus.

Your Schumacher. Now the AH primer is over... your Schumacher "can" recharge your batteries... to an adequate level, but it's going to take awhile. Using the same example as above, it would require your Schumacher 13.3 hours (@15amps) to replace 200ah's of usage. That being said... your Schumacher doesn't ouput 15amps until full. As your battery bank refills, the input amps will gradually decrease. It does have an automatic shut-off, so there isn't much risk in doing any harm to your batteries, but it's a VERY slow process (requiring extended generator use) and in the end, will only provide approx. a 85-90%~ish charge to your battery bank. To be aware, that type of charger is intending for single battery charging so it's easily confused by the capacities and residual charges over your 4-6V cells.

I'm not sure which battery meter you are referring to. The one on the Schumacher or do you have another battery meter connected to your bank? The main issue that can lead to poor readings when connecting a charger like that directly to your battery bank is the residual charge your batteries take on during the charge process. 

You've got a very decent battery bank there. You mentioned a "camper"? Is it equipped with a converter? The size of your generator?

You would be served better (faster more complete charges) with a seperate staged, temp compensated "smart" charger, but without knowing more about your rig it's difficult to know what to recommend, but I would enclined to think that a Progressive Dynamics converter/charger, might be a good direction to start looking.

The end run? What you have is doable, but not ideal. The main downside is extremely long generator run times, not having the full capacity of your battery bank available and a shortened battery lifespan.

For your specific question. The Norcold. If that is all that was running, then yes. You're 80watt would be fine. HOWEVER, all rigs have some amount of a "phantom load". Depending on what rig you have, that can run into a 1amp load (with everything turned off, but the battery connected).. or in other words.. 24ah's/day. Even at 100% production and efficiency... the theoretical max of your 80watt would only produce 24ah's on the very best of days.

You would have to use an amp clamp to determine what the "phantom load" is on your rig to determine if your panel would be able to keep up. You also have to remember that you are battling a normal self-discharge rate of approximately 10-15%/30 days of your batteries.

Reliable meters are available, but they do cost. The Trimetric is an excellent and proven meter with a "decent" price tag (I use one myself). In addition to giving you an accurate reading "on the fly", it will also monitor the amps in and amps out of your batteries. Ideal for measuring phantom loads and others as they on/off.

[Yarome]

10 minutes ago, oldjohnt said:

YOU NEED AN ENERGY AUDIT to see what your daily energy requirements are and ONLY then can you calculate if your charger and solar can keep up     

John... you BEAT me! 

[oldjohnt]

Yarome, you snooze you loose lol  I accidentally hit the post button before I was finished and had to go back and edit so I have no idea how much my initial post said?? At first glance it appears you and I are on the same approximate page in our answers, might that be because great minds think alike orrrrrrrrrrr even a blind squirrel finds a nut now n then lol

 

John T

[Yarome]

10 hours ago, oldjohnt said:

Yarome, you snooze you loose lol 

...even a blind squirrel finds a nut now n then lol

Let's go with that. LOL 

The only real difference being the Norcold. It shouldn't drink that much and he wouldn't need to power the inverter if he's not present and on 12V and LP for his reefer.  Depending on the model... the control board will pull around .25/24/7 and .5amps (providing he doesn't have any fan's installed) for a 10cf when cooling. So call it 12amps max if it runs non-stop. His 80 watt "could" likely keep up... most days... but then there are the other control boards, radio memory (if installed), dectectors, self discharge, ground leakage etc. etc. to consider.

[Yarome]

1 hour ago, oldjohnt said:

Invests in at least a 20 amp better yet a 40 amp Smart 3/4 Stage quality charger.     

A 70-80amp smart (~10amps of 120V) on a 440ah bank would be preferrable. Depending on his genny.. it may not support the full charge rate, but if he is running at least a 1500 watt (1250 watt sustained) he could be back up off of 75% SOC in ~2hrs.

A Honda or Yamaha 2000 in ECO can pull that off for about 1qt of fuel. 

[Al F]

Risenterror,  you have received some excellent detailed information in the replies above.

To help simplify things, you mentioned you are going to power "an inverter and some LED lights" with your 4  6V Costco batteries.  Just what are you planning on powering with the inverter and what is the wattage of the inverter?

If you have a 300 watt inverter and will just charge your smart phone, power a laptop and watch a LED TV for a couple of hours, that is a whole lot different than using a 2000 watt inverter to run your microwave, a toaster, a coffee pot and perhaps a satellite TV for 4-5 hours a day. 

About running the generator to recharge your batteries, you want a 3 or 4 stage charger which will provide up to 100 amps of 12V (12V nominal) current to your 400 amp hours of battery.  The 100amp number is based on charging at the 25% rate, which is pretty much the standard charge rate for lead acid batteries.  With the 100 amp charger you will only need to run the generator for 1-3 hours to charge your batteries to the 85% to 90% of capacity.  Also you want to do that charging before you leave so the solar panel will hopefully finish the charging while you are gone for 4 or 5 days. 

[oldjohnt]

Yo Al, believe it or not for my four Trojans 450 AH I went with a PD 9280 80 amp charger, and sure bigger is better and that 25% factor is relevant and all that, but if I had it to do over I might have selected the 60 amp unit. One wonders WHY ???????? The thing is the 80 draws fairly high current and even came factory equipped with a 20 amp versus a 15 amp male plug. The issue I have is if the batteries are  discharged and at the same time I need to run my 4KW Generator PLUS my rooftop AC, it really labors my genset. It still runs and works, but boy you should hear the difference when I temporarily turn the charger off lol.

Fortunately its a rare situation when I find my batteries ran down (have to max out charger)  while at the same time I require roof AC when dry camping and I have to run the genset, so no need to change anything or spend any bucks on it, just saying how the 80 amp charger and AC at same time makes the genset bear down.

My last RV with four batteries and only a 60 amp PD9260 charger and another 4KW Genset just performed better under those high dual loads BUT AS YOU INDICATE it takes longer to charge using a small charger WELL DUH.  Regardless he needs MORE then that little 15 amp unit.

Fun chattin with you, take care n God Bless

 

 John T

[Risenterror]

Well I got a ton more information then I expected, thank you all.  My camper was gutted so it only runs off my generator which is a new 2000w Yamaha.  We only use it for sleeping as the campsite has a covered deck where we spend our time and where the fridge is at also.  I have a 1200w inverter which brews a pot or 2 of coffee in the morning and runs a couple strings of led lights(not xmas style). We charge phones and run a water pump that has a manual switch to increase pressure when needed.   Our other lighting is 12v led lights similar to interior rv lighting that I have wired to switches.   

I don't know what my energy output is right now obviously.  Sounds like I for sure need to invest in a better charger.  I don't run anything off my generator other than lighting in the camper and charging the battery bank.  

With what I have said could you guys recommend a couple specific chargers I could look at?

Thank you all again for the great replies!

[Yarome]

1 hour ago, Risenterror said:

With what I have said could you guys recommend a couple specific chargers I could look at?

Of course, it depends on what you'll be powering on genset while charging, but your Yamaha has a 1600 watt continuous output (13.3amps) so you're pretty wide open. I would still be looking at a Progressive Dynamics converter/charger. but it would be a balancing act as to what size of charger you would want to go with. Larger means quicker charge times, but less available for additional loads.

With the converter/charger... the converter side would provide 12v for lighting and such while the charger refills your battery bank (vs. running your lights off battery while charging). That being said... if your camper is completely gutted and has no power distribution panel, that's a bit of a different story, however, a simple 12v fuse panel could be installed fairly inexpensively.

Depending on what size of charger you choose... power requirements would range from 6 amps (45amp charger) up to 11 amps (80amp charger) of your 13.3 amps available. 

As Al pointed out, "ideally" you want to shoot for a charger with capacities in the 20-40% range of your battery bank. A 100.. or even a 125amp charger would be a great spot to be in for your bank, however, your generator wouldn't support that much juice and still have anything much left to give for any other 12v loads without "surging" up to 2000watts (capable for 30mins). That equates to more wear and tear on your genny and much higher fuel consumption. Although... it's certainly within it's capability.

It all comes down to need vs. capability vs. budget.

To be fair... Powermax would be another, less expensive, option. Personally, I wouldn't recommend them, but if you want something to compare against. You're dime.. your decision. 

[oldjohnt]

Risen, thanks for the feedback and added info, it helps us help you.

 My last two chargers have been Progressive Dynamics (Smart 4 stage charging) and I'm so satisfied with both of them that would be my choice. I had a top of the line Xantrex but it crapped out in less then a year grrrrrrrrrrrrrrrrr. Just like asking what brand of oil one should use, I'm sure there are plenty of other quality charger recommendations out there. Research and do your homework and make your decision. There are plenty of opinions out there, mine included.

 As far as what size, you obviously need A LOT MORE then you current 15 amp and sure bigger is better in a lot of ways. HOWEVER as I posted above a huge honkin charger like an 80 amp or more (that I have with four Trojan batteries)  may draw more current and tax your generator if others loads are on line at the same time IE too big is something to think about subject to loads and generator capacity as you need room left for other non charger loads.

That being said and based on the latest info, its my opinion absent any energy audit (so my best guess) you still want AT LEAST 40 AMPS but I fear 80 might possibly be a bit too much (current requirements) so how's about a happy medium OF A 60 AMP CHARGER???? I think that's a PD 9260 (or used to be) but don't quote me on that

SURE either a 40 or 60 or 80 can "WORK" (subject to loads and genny capacity) and an energy audit can provide a better answer, but for now based on the info currently available and since you asked for recommendations  MINE IS NOW UPDATED TO AT LEAST A  40 PROBABLY A 60 AMP as I fear an 80 may (cant say for sure from here not knowing all your loads) crowd your generator, but again, SUBJECT TO genny capacity and other non charger loads. NEED MORE INFO FOR A BETTER DECISION 

PS Id also consider upping that solar to at least 100 watts or better yet 200 +. I recently bought a single 245 watt panel for 90 cents per watt which measures 39 x 64 works great. 

Ya know if you robbed $500 or even less so from the wife's piggy bank and added say a 100 or 125 watt panel to your existing 80 watt array and sprung for say a 60 amp Smart 3/4 Stage Charger and used your existing Genset YOU OUGHT TO BE IN HOG HEAVEN. Gee its fun to spend other peoples money, Id make a good politician lol 

Great questions fun discussion, I'm NOT a solar expert so do as the true experts say NOT me

John T

 

[Yarome]

Got more than you bargained for did'ya? 

This is where opinions come in to play. If you only ever plan to run LED lights, a water pump, your reefer (on LP) and your charger... My recommend would be no less than a 60amp, 80amp would be the "happy medium" (IMHO) and you could easily get away with a 100amp if you don't mind your genny possibly surging up periodically when you need to run your water pump.

An 80amp (11amp AC draw) would leave you with ~25amps of 12v available (~275 watts or 2.3amps of AC) for lights and such. You certainly wouldn't be able to run a coffee maker or want to run your inverter while charging, but you could charge your phones using a 12v USB adapter, have lights, watch a bit of TV and run your water pump as needed... etc.

To note: With an 80amp the "~25 amps of 12v" is at the continuous output rating (1600 watts), however, surging up to the full 2000 watts would allow you ~63amps of 12v (~685 watts or 5.7amps of AC). That's fairly substancial

Solar... that should probably be started in a new thread if you decide you want to go in that direction. However, keeping it simple (inexpensive) you might consider just throwing on another matching 80 watt. Your 15amp controller could handle that without issue. 

[Lou Schneider]

18 hours ago, Risenterror said:

I also have an 80w solarpanel 15amp charger and controller that I can use while not there but the amount of direct sun through the trees is not great, so there will be a lot of indirect light.

I think this quote from the original post pretty much eliminates solar contributing anything more than a maintenance charge between visits.

Solar panels need to be in full sunlight to produce power and won't while they're in indirect light, i.e. in the shade. Even partial shading of a panel will cut its output to zero, the full panel needs to be in direct sunlight to work.

[Yarome]

6 hours ago, Lou Schneider said:

...pretty much eliminates solar contributing anything more than a maintenance charge between visits.

Even partial shading of a panel will cut its output...

Very true. Truck campers also have a VERY limited amount of effective real estate. Unless you're going with portable arrays (which take up quite a lot of critical storage space) it's very difficult to assemble a system that will meet any significant portion of persons energy requirments in a dry camping situation.

That being said... any solar is good solar. 

[Risenterror]

Thank you all again.

I ordered up a PD9270V today and will install this weekend and let you know how it goes.  I should be able to get an idea if my solar panel was able to at least maintain the batteries with the fridge running this week.

Again thank you!!

[Al F]

If you have full sun on the panels for an hour or more each day you solar panel will maintain your batteries just fine.  The fridge, on propane, only takes about 0.2A when not cooling and about 0.1A more when it picks the solenoid to let the gas flow to the burner. 

If you have shade with spotty sunlight, you will get some small amount of power from your solar panels.  

We were camping under broad leaf trees last weekend.  There was some sun coming through the leaves. We were getting about 2-3 amps from our 650watts of solar panels.  In full sun at midday we are getting 40+ amps.  We are pretty far north. On the coastline near Portland, OR.

[Yarome]

34 minutes ago, Risenterror said:

I ordered up a PD9270V today..

Guarantee you'll be a happy camper. PD's customer support and service is pretty much the best in their industry and they do a real decent job of keeping their charge algorithms current.

Don't forget to run an in-line fuse or switchable breaker to your batteries.

[Yarome]

28 minutes ago, Al F said:

  We are pretty far north. On the coastline near Portland, OR.

Where abouts? I forget the name of the place, but sounds like (broadleaf trees on the Northern coastline) you folks were up at the "cellular black hole" camp. Am I close? 

[Al F]

2 hours ago, Yarome said:

Where abouts? I forget the name of the place, but sounds like (broadleaf trees on the Northern coastline) you folks were up at the "cellular black hole" camp. Am I close? 

Kilchis county park, just NE of Tillamook, OR.  Actually there are lots of places in the area where cell coverage is minimal to non existent.

[oldjohnt]

Yo Al, Regarding your post " If you have shade with spotty sunlight, you will get some small amount of power from your solar panels"

   I agree and can testify and verify I still harvest solar energy even when parked in full shade. In fact, even when parked under a pole barn roof IE no direct sun whatsoever, I STILL HARVEST SOLAR ENERGY. I have 715 watts of rooftop solar panels and an MPPT Solar Charge Controller, which is a lot for a small 29 ft Class C with modest energy requirements, but the reason I wanted so much is because when its hot I like to park under full shade and be able to run two power ceiling vent fans plus an inverter operated 20 inch fan plus the ordinary water pump and LED light use etc. and still achieve and maintain at or near 100% SOC in my four battery bank WORKS GREAT.

 John T 

[oldjohnt]

3 hours ago, Risenterror said:

I ordered up a PD9270V today and will install this weekend and let you know how it goes.  I should be able to get an idea if my solar panel was able to at least maintain the batteries with the fridge running this week.

Again thank you!!

 Yo Risen CONGRATULATIONS

 That's a 70 amp Smart charger right?? You should do well with that. As far as an 80 amp solar panel harvesting sufficient energy to maintain the batteries THAT DEPENDS ON THE AMOUNT OF SUNLIGHT AND ACTUAL LOAD and none of us can answer that from here. If so great but if not, maybe hang an additional panel with it ?? That's a fairly cheap n easy addition and you may or may not need a higher rated charge controller subject to its rating and your total solar watts.

 You're doin great

 John T

  

[Yarome]

31 minutes ago, Al F said:

Kilchis county park, just NE of Tillamook, OR.  Actually there are lots of places in the area where cell coverage is minimal to non existent.

Ooohhh... Garabaldi! Great diving and crabbing, that. Wasn't were I was thinking of, but nice area. Can't ever go through there without picking up some "squeeky cheese" and meat sticks.  Seems I heard rumors awhile back that the factory was tearing down the vistor's center.. any truth to that?

[Yarome]

1 hour ago, oldjohnt said:

I agree and can testify and verify I still harvest solar energy

John... I dunno, brother. You sure your meter isn't just picking up your personal residual discharge from grabbing too many hot lines during your career? As you walk closer.. does your meters "in" amps increase? 

[Al F]

12 hours ago, Yarome said:

Ooohhh... Garabaldi! Great diving and crabbing, that. Wasn't were I was thinking of, but nice area. Can't ever go through there without picking up some "squeeky cheese" and meat sticks.  Seems I heard rumors awhile back that the factory was tearing down the vistor's center.. any truth to that?

The cheese factory put up a metal building to house the gift shop and ice cream sales, while a new visitor center is being built.  So, yes, the old visitor center was torn down.