Easy solar charge controller question

[Pyscokev]

I bought a cheap solar kit that came with two 100 watt panels and a 30 amp windy nation p30l charge controller. I have four of the costco 6 volt golf cart batteries. It seems to me that this controller isn't right for my setup. I think it will charge my batteries until they reach a certain voltage that I punch in. It came set to 13.8. Will this kill my batteries from overcharging or not charge them well enough? My goal is to not need to plug in my trailer while I'm not using it or on 3-4 day trips. Any suggestions would be helpful. Thanks. 

[Ed ke6bnl]

far from being an expert but seem like what you have would be closer to the maintainer end of the spectrum with about 5.5 amp charging to the battery.  that will definately help and keep the batteries up to charge, and my understanging is that the charge controller will prevent over charging.  I went with 250 watts still no overcharging and a bit more for the usage during the camping days. so depends on if the sun is up and if 5.5 amp is enough to take care of the amount of draw used on the batterie during the day. Let see what the experts have to say.

[mptjelgin]

Two 100 watt panels will supply around 15 amps on a good sunny day, so this is well beyond a "maintainer".

To answer the OP question, most "good quality" solar chargers have at least three stages. The bulk charging stage will generally put as much current as possible into the batteries until they reach 14.4 volts. Then it changes to the absorption stage, where it holds the 14.4 volts for a period of time. And finally it will drop to the float stage which is 13.8 volts for a typical flooded acid battery.   

Note that these voltages may be higher or lower based on the temperature of the battery. Good solar controllers will have a temperature probe that attaches to the batteries as part of the system. 

And some controllers have a forth stage which will take the voltage even lower if the battery has been at 13.8 volts for a long period of time. 

I looked up the manual for your controller and it looks like the float voltage can be adjusted from 12.8 to 15.0 volts, with the default at 13.7 volts. 13.7 volts is just fine, though some folks prefer it a bit higher to keep their batteries "up" a bit more.  And I see where your unit does offer an optional  temperature probe to provide compensation so I would get that as well. 

[Pyscokev]

Thanks for the responses. I do have the temp probe which is nice when it's freezing out. So maybe it charges at 14.5 volts until the battery is full then it goes in to float mode? That sound correct? Appreciate the help

[pjstough]

The absorption  voltage for your batteries is probably 14.8 volts.

[mptjelgin]

That is correct. It will charge to higher voltages when the batteries are cold, and lower when the batteries are hot. But expect to see it charging at 14.4 (ish) volts for several hours (assuming the panels can get it there) before dropping down to float voltage. 

ON EDIT - I guess not!  As Yarome pointed out this is not a multi-stage controller, so it will just cut off upon reaching the set voltage. So it may not ever get your batteries to a fully charges state, but should be fine for 3-4 days. If you plan to stay with solar for longer periods of time you may want to consider a multi-stage controller. 

[Yarome]

3 hours ago, Pyscokev said:

I think it will charge my batteries until they reach a certain voltage that I punch in. It came set to 13.8.

Will this kill my batteries from overcharging or not charge them well enough?

My goal is to not need to plug in my trailer while I'm not using it or on 3-4 day trips.

Just a clarification. That particular solar controller is a PWM and is not a multi stage. You'll have only one charge voltage setting to contend with. 4-6v'ers... 13.8v is a decent middle ground. 13.6 would be better at certain SOC (state of charge) levels, and 14.4v better for bulk, but it's really a moot point. 14.4v isn't needed to "push"  10-15amps of current into your battery bank. Heck... if your wiring is properly sized so resistance is minimal... 13.6v would push 15amps just fine and would make for a gentler charge as your batteries get closer to capacity, but I would leave it at 13.8v. A little extra "umph" during the highest solar production hours of the day can't hurt it a bank that size.

Overcharging will not be an issue. Charging them well enough? That's a relative question. 2-100watt panels in parallel are only going to push a theoretical 50-70ah's of juice on the very BEST of days in the most idealic conditions. This time of year.. you might only see 35-40ah's of production.

If you have a 440ah battery bank (220ah's "available". 50%SOC) and use all of it... it would take several days to replace that much juice. 

It's more than a "maintainer" system but would most likely not be able to keep up with energy demands. Can it stretch a fully filled 440ah battery bank out to 3-4 days? Hightly likely! With some careful energy budgeting. Ie., you start out with 220 available. You use 60, you replace 30. You're only down to 190. 3-4 days before you burn off all 220... it's "doable".

[Yarome]

4 minutes ago, pjstough said:

The absorption  voltage for your batteries is probably 14.8 volts.

 

3 minutes ago, mptjelgin said:

 But expect to see it charging at 14.4 (ish) volts for several hours (assuming the panels can get it there) before dropping down to float voltage. 

Unless I'm missing something... the controller he referenced is not a multi stage controller. A "float" controller is a single stage. You can "simulate" a multi manually, but unless you have the panels to back up the max rated output it's a moot point. 

[mptjelgin]

1 minute ago, Yarome said:

Unless I'm missing something... the controller he referenced is not a multi stage controller. A "float" controller is a single stage. You can "simulate" a multi manually, but unless you have the panels to back up the max rated output it's a moot point. 

You're right. I went back and edited my last post. I didn't realize that it was a single-stage controller. 

[OldMan]

You guys must be talking about lead-acid batteries. I'll use Li-ion.

Despite Ray's explanation, I'm an MPPT guy. It's worth the money to me.

[Sehc]

I just want to clarify something for my satisfaction. Yes this is a PWM with single stage charging. I'm not even sure the set point voltage can be reset by operator. But, some PWM controllers are fully adjustable and have multiple stages. I have a Morningstar PWM and can't fault my 400W system.

[Yarome]

5 hours ago, OldMan said:

You guys must be talking about lead-acid batteries. I'll use Li-ion.

Despite Ray's explanation, I'm an MPPT guy. It's worth the money to me.

An MPPT controller does have it's advantages... input permitting. With a 200watt system there is no advantage and lead-acid vs. Li-ion is...  dunno how that entered into the thread.  It's moot.

1 hour ago, Sehc said:

I just want to clarify something for my satisfaction. Yes this is a PWM with single stage charging. I'm not even sure the set point voltage can be reset by operator. But, some PWM controllers are fully adjustable and have multiple stages. I have a Morningstar PWM and can't fault my 400W system.

The voltage is user adjustable with your current converter/charger. And yes.. there "are" multi stage "smart" chargers that are PWM's. The cost difference is becoming more negligible, but not every system is able to take advantage of an MPPT. After all... a $'s a $.

[Al F]

On 1/21/2018 at 9:17 AM, Pyscokev said:

I bought a cheap solar kit that came with two 100 watt panels and a 30 amp windy nation p30l charge controller. I have four of the costco 6 volt golf cart batteries. It seems to me that this controller isn't right for my setup. I think it will charge my batteries until they reach a certain voltage that I punch in. It came set to 13.8. Will this kill my batteries from overcharging or not charge them well enough? My goal is to not need to plug in my trailer while I'm not using it or on 3-4 day trips. Any suggestions would be helpful. Thanks. 

On thing that has been left out of this whole conversation:  The ability to monitor the number of AH's (Amp Hours) used and the number of AH's put back in the batteries.  

You need a battery monitor, such as a Trimetric which displays how many AH's has been used by your RV, also shows the percent of charge and other nice things to know, such as how many amps are being used at any moment in time and your battery voltage. 

With a battery monitor you know, not guess, how many of your approximately 400AH of battery has been used.  You will also know if your solar panels has charged your batteries to 100% and you need to disconnect the solar controller so as to not to over charge the batteries.   Or you could lower the voltage parameter on the controller to a 13.4V float level. 

The bottom line is, w/o a monitor you are flying blind as to the state of charge (SOC) of your battery.  This makes it far to easy to over discharge your battery to the point of greatly reducing the life of your batteries.  On the other side, overcharging, and with a constant charge voltage of 13.8V, on fully charged battery, will boil off the water, thereby exposing the plates inside the battery to the air, which pretty much destroys the battery.

 

[GlennWest]

On 1/24/2018 at 8:01 AM, Yarome said:

An MPPT controller does have it's advantages... input permitting. With a 200watt system there is no advantage and lead-acid vs. Li-ion is...  dunno how that entered into the thread.  It's moot.

The voltage is user adjustable with your current converter/charger. And yes.. there "are" multi stage "smart" chargers that are PWM's. The cost difference is becoming more negligible, but not every system is able to take advantage of an MPPT. After all... a $'s a $.

Actually you get twice the energy from lithium. That 200 will be like 400.

[Yarome]

3 hours ago, Al F said:

On thing that has been left out of this whole conversation:  The ability to monitor the number of AH's (Amp Hours) used and the number of AH's put back in the batteries.  

The bottom line is, w/o a monitor you are flying blind

X2

50 minutes ago, GlennWest said:

Actually you get twice the energy from lithium. That 200 will be like 400.

Hmm. My math doesn't work that way, but I understand your point. 200 would get you 160 = ~$2K. 400 would get you 200 = ~$360. 200 is more than 160  But either way... it isn't germane to the solar elements being discussed. The only "real" benefit lithium's add, as a solar system element in regard to production, is their ability to more readily accept whatever solar energy is actually being produced. When you're talking a 200watt array w/PWM controller... it's not going to make a whole hill of difference that would justify the additional expense. Kinda like stick'en a Ferrari engine in a Kia.

From a storage/living off your bank for 3-4 days you would need to increase the lithium capability to ~300ah's to get in the same approximate available AH's of a 440ah wet cell bank. $3K vs. $360?

Usage? An AH's an AH and a $'s a $. If your intention is to use strictly solar while dry camping for 3-4 days... lithium or wet cell will make little to no difference in how long you are able to sustain your bank.

[ALLOY]

The numbers are something like this.....

Charge efficiency (input) of FLA is 100% at 60% SOC and drops to 50% at 80% SOC

Charge efficiency  (input) of Lion remains at 97% from 60% to 98% SOC....best not to go above 98% on Lion...better yet is 90%

 

 

[GlennWest]

9 hours ago, Yarome said:

X2

Hmm. My math doesn't work that way, but I understand your point. 200 would get you 160 = ~$2K. 400 would get you 200 = ~$360. 200 is more than 160  But either way... it isn't germane to the solar elements being discussed. The only "real" benefit lithium's add, as a solar system element in regard to production, is their ability to more readily accept whatever solar energy is actually being produced. When you're talking a 200watt array w/PWM controller... it's not going to make a whole hill of difference that would justify the additional expense. Kinda like stick'en a Ferrari engine in a Kia.

From a storage/living off your bank for 3-4 days you would need to increase the lithium capability to ~300ah's to get in the same approximate available AH's of a 440ah wet cell bank. $3K vs. $360?

Usage? An AH's an AH and a $'s a $. If your intention is to use strictly solar while dry camping for 3-4 days... lithium or wet cell will make little to no difference in how long you are able to sustain your bank.

It has been posted on here where RV had 1000 of battery agm and replaced with 500 lithium and had more energy output. The fact that you can run them down more before charging decrease the amount of battery needed.

[Yarome]

19 minutes ago, GlennWest said:

It has been posted on here where RV had 1000 of battery agm and replaced with 500 lithium and had more energy output. The fact that you can run them down more before charging decrease the amount of battery needed.

I knew he was speshkal, but he must be "magic"! 

1000ah of wet cells at the recommended 50%SOC=500ah's "available". 500ah's of lithium at the recommended 20%SOC=400ah's "available". Last time I checked... an amp was an amp and 500 is more bigger than 400.  Can't fight physics. Running a 500ah lithium bank dead would still only be equal to the available current of a 1000ah wet cell bank @ 50% discharge.

You may have misinterpreted what he might have posted. He may have said he had an increase in the level of output but that doesn't equate to "more energy" in a 500ah lithium bank over a 1000ah wet cell bank.

At any rate... it as little to nothing to do with the OP.

[ALLOY]

Taking FLA to 50% SOC is tried and tested

Taking Lion to 20% SOC is under debate

[Al F]

I am always amused when so many times I see references or mentions of running your lead acid batteries (AGM included) down to 50% SOC. 

Don't ignore the fact that if you only discharge your lead acid batteries to 75% SOC (use only 25% of capacity) you get twice the life from the battery than if you discharge it to 50%. 

Trojan batteries life cycle charts show about 3000 cycles when discharged to 75% SOC, however the number of cycles drops to about 1500 when discharged to 50% SOC and around 750 when discharged to 80% SOC.

Lithium batteries don't have that steep of a life cycle reduction if you limit your discharge to about 25% SOC (use about 75% of capacity). 

Additional one other thing everyone should keep in mind.  A lithium battery will be just as happy operating for weeks on end between 40%  and 80% SOC as it is operating between 40% and 98%.  (actually longer life if you only go to 93-95% SOC) The key here is you don't need to get it charged to 100% on at least a weekly basis like you do your lead acid batteries.  Getting lead acid batteries to 100% is not that easy when not on shore power.

None of this matters unless you plan on dry camping for long periods of time.  If all you will be doing is dry camping for 2-7 days and then back on shore power, the cheapest golf cart batteries will work just fine.

 

[noteven]

I read somewhere that a Bogart Trimetric monitor and a Bogart controller work well together.

[Yarome]

9 hours ago, Al F said:

I am always amused when......

What blows ME away is how it ever came to be that people started believing that you get twice the life out of a battery bank if you only discharge to 75%SOC vs. 50%SOC.

400ah bank. 100ah=25% discharge. 3000 life/charge cycles = 300,000ah's used over the life of the battery bank.
400ah bank. 200ah=50% discharge. 1500 life/charge cycles = 300,000ah's used over the life of the battery bank.

I don't know about anyone else's math, but 300,000 sure looks like 300,000 to me. When the life cycles begin to decrease exponentially is the only important factor.

~ That's kind of like saying you get twice as much food if you only eat half and leave the other half until tomorrow. 

 

[Note: I have never once ever made the "double life" claim.]

[Al F]

10 hours ago, Yarome said:

What blows ME away is how it ever came to be that people started believing that you get twice the life out of a battery bank if you only discharge to 75%SOC vs. 50%SOC.

400ah bank. 100ah=25% discharge. 3000 life/charge cycles = 300,000ah's used over the life of the battery bank.
400ah bank. 200ah=50% discharge. 1500 life/charge cycles = 300,000ah's used over the life of the battery bank.

I don't know about anyone else's math, but 300,000 sure looks like 300,000 to me. When the life cycles begin to decrease exponentially is the only important factor.

~ That's kind of like saying you get twice as much food if you only eat half and leave the other half until tomorrow. 

 

[Note: I have never once ever made the "double life" claim.]

That is a way I have never thought to look at the battery life cycle issue.  It certainly has its merits.

Some additional thoughts:

--  At 300 charge cycles a year the life of the battery at 25% discharge would be 10 years, while the one discharged to 50% would be 5 years.  That is twice as long, double the life perhaps????  Not double the number of AH's though.

-- If we design our battery usage for a 50% discharge, there will be quite a few times we WILL exceed the 50% figure, which is pretty stressful for the life of the battery.  There by reducing the life of the battery even more.

--  Planning on the 25% figure and going to 35% or even 40% quite a few times is less stressful on the battery.

If a battery/solar system is 400AH of battery and 600AH of solar, a typical well designed system in my estimation, we are much more likely to consistenty get the battery to 100% charge with the 25% discharge number.  That is, getting 100AH back into the battery versus 200AH.  Lots of days are a bit hazy or light clouds reducing the ability to charge the batteries to 100%.

Having written all that, there is no reason we can't discharge to 50%.  Just as long as we realize there are trade offs for doing that.

Just like we don't do jack rabbit starts and slamming on the brakes on our vehicles and wonder while the vehicle doesn't last as many years.  There is not reason why we can't do that.  It is, we should not expect as long a life. 

BTW, I would be still be getting the same total number of RPM's from the engine with jack rabbit starts.  I just would not use the vehicle as many years.

[Al F]

12 hours ago, noteven said:

I read somewhere that a Bogart Trimetric monitor and a Bogart controller work well together.

As in communicate with each other?  I don't know.  There may be information on the Bogart website, you could check out.

My use of the Trimetric monitor is so I can see at a glance, exactly what the status of my battery AH's are, the battery voltage and the momentary number of amps going in or out of the battery.  I have the monitor mounted in the living area where it is easily visible.

[ALLOY]

12 hours ago, noteven said:

I read somewhere that a Bogart Trimetric monitor and a Bogart controller work well together.

 I've never used one but I've I read a few positive (never a neg) posts from people that have the monitor and 1 or 2 of the controllers.