Equalizing Batteries in a Solar Array

[ird13]

Hi guys,

Recently my boyfriend and I finally got all of our solar hooked up an running. We have two 245w mono solar panels connected to a Renogy MPPT 40CC charge controller and two batteries in our bank. One battery has 122AH, and we went to purchase an identical battery (EverStart brand) and unfortunately they have stopped selling this exact battery. So our second one is the same brand and type, but with 100AH. They are connected in parallel. When using a volt meter, our charge reads around 14v for each battery, but when using a float hydrometer the read is only 3/4 full. Because the exact voltage reads fully charged, our charge controller has shut off power to the batteries so they are no longer taking in power, even though they are definitely not fully charged.

We are looking into the possibility of having to equalize them, but we aren't even sure if equalization is the problem. Does anyone have any input as to why our controller would shut off power before the batteries are actually full?

Thanks,
Dani

[family wagon]

Handy Bob's opinion (look for "VOLTAGE:" in bold; it doesn't have an anchor to link the exact spot) is that the charge controller limit voltage is too low. Maybe also the cables are too long (or undersized), or connections may not be clean. He cites battery manufacturer specs as high as 14.8 or even 15.0 volts.

EverStart is the O'Reilly house brand, isn't it? Good luck getting specs on that... but since you have a hydrometer, I vote that you tweak the charge controller limit upward until the hydrometer says the batteries are charged. If the controller doesn't automatically back the voltage down after letting the batteries absorb for a while, then you might have to do that manually...?

[ird13]

According to a worker for Renogy, this charge controller is rated up to 500w so we should be within the limits of power. I've seen reviews of other people using exactly 500w with the same controller. I will certainly look into raising the voltage limit, although I was under the impression it is automatically adjusted using it's own sensor system. Thanks for your help

[bubb, the real one]

most wet lead acid batteries need to receive a charge of up to 14.8v and held their for a while to fully charge the battery, if your charge controller never charges above 14v then it is not fully charging the battery,

it would be helpful if you could check the charge on the batteries first thing in the morning before the sun comes up so we can get a good voltage on it, fully charged and then sitting overnight it should read 12.6 or 12.7

[jazty]

Ah, I just looked up what a Renogy 40a charge controller is. It's actually a re-branded Tracer 4210rn 40a MPPT charge controller; the exact same one I have.

The controller definitely has the ability to equalize the batteries, but I don't know of any way to force it. The documentation says that it will run an equalization charge after the batteries have been depleted too low and - if I'm remembering correctly - on some sort of schedule.

If you had an older car charger (not digital) you could probably equalize them using it. We have one of those big chargers on wheels in the garage and it's upper voltage is a bit above 15v (yikes). That will have the batteries off-gassing, but since an equalization charge is around 14.8 - 15v it would probably work . Charge the batteries normally, then use the high voltage charge for an hour or two.
That's what the Tracer charge controller does anyway. 120 minutes at 14.8v for equalization charge.

[jazty]

Also, make sure you have the temperature compensation set up correctly. Maybe the default setting is screwed up and this is why you're only getting 14.0v when charging.
If you had only one make and model of battery then the setting would be easy. The battery datasheet will provide the voltage compensation per degree. With two different batteries the compensation voltage may vary.. But you may be lucky since both batteries are the same brand.

Here's the manual for your charge controller in case you don't already have it:
http://solarlab.se/solpanel/datablad/Tracer-4210RN.pdf

Do you have one of these?

http://www.amazon.com/RENOGY%C2%AE-Tracer-Meter-Charge-Controller/dp/B00GHY270Y/ref=sr_1_5?ie=UTF8&qid=1436203779&sr=8-5&keywords=tracer+charge+controller

I think you need it to alter the controller's default parameters. It provides some interesting information, too. Worth having, in my opinion.

[ird13]

Amazon.com: Renogy® Tracer 4210 40 Amp MPPT Charge Controller 12/24V 100VDC Input: Patio, Lawn & Garden

This is the exact charge controller we have. We have read the same bit of info in the manual saying it has a 120 minute equalization boost, however, our batteries have yet to be at the same charge for the entire few days we have had this set up. Right now they are at 1/2 and 1/4 full

We have a big battery charger like you mentioned and thats what we have been using in the mean time, but tomorrow morning we leave for a week long trip where we will not be connected to power. Of course, if necessary, we have a generator where we can plug in the battery charger but it just seems like such a waste when we have all this power coming from the sun, ya know?

We may have found an in-person connection who can help us sort things out, so wish us luck! And thanks for your input guys.

[luap928]

Hi everyone, I am the boyfriend that's trying to get this all set up. Thank you all for you help.

It's not the battery cable gauge; I used 4ga wire running a total of about 7 feet from the solar panels to the charger controller, and an additional 4 feet of 4ga wire going from the controller to the batteries.

Our batteries are reading 15.1 volts after I disconnect the solar charger and let it sit for an hour.

I am running a 4 amp load off the battery right now to try to discharge the surface voltage and I am going to go re-check the voltage.

I have been on the phone with Renogy tech support and they don't use a hydrometer to test the batteries when they set up systems, they only use volt meters so after talking to 3 techs (who were truly as helpful as they had the knowledge to be) I am still stuck not knowing what to do.

We don't have the add-on LCD screen for the unit so we can not adjust any of the factory settings. (if that is how you adjust them). We are going to a festival tomorrow morning for a week, when i get home I will order the lcd screen and see if that helps with the problem.

I am starting to lean toward the fact that we bought crap batteries and shouldn't have. I mean we spent nearly $1000 for the system and then went cheap on the batteries. In hindsight that was probably a poor decision.

[jazty]

Originally Posted by luap928

Our batteries are reading 15.1 volts after I disconnect the solar charger and let it sit for an hour.

Oh yeah, that should equalize them. That's pretty high.

Originally Posted by luap928

We don't have the add-on LCD screen for the unit so we can not adjust any of the factory settings. (if that is how you adjust them).

It is. Using the LCD you can enter the battery bank size in Ah, the battery type (flooded acid I'm guessing?), the temperature compensation amount and a couple other things. It also shows how many amps are going into the batteries. I'm not sure the controller settings can be altered in any other way. The LCD should actually come with the controller. It seems silly that it doesn't.

Originally Posted by luap928

I am starting to lean toward the fact that we bought crap batteries and shouldn't have.

This could be the case. Maybe there's something wrong with the more recent battery you purchased. Any chance you could return it and get another? Or have them test it?

I picked up a battery with a manufacturers defect not long ago. The stupid thing had the polarity reversed! The store took it back with no hassle, but I never got the $80 for the little inverter it fried..

Mixing batteries can be problematic. It's possible that your problems stem entirely from the mixing, but I don't know enough about it to be certain.
Google: mixing batteries solar system in parallel

Of course ideally you want to have a couple batteries of the exact same age and type, but I know you didn't have much choice since the earlier battery was discontinued. You could try charging them both completely separately and see how they hold up. If they both function properly then you may need to install a battery selection switch. You might be able to use a battery isolator instead, but that comes with a voltage drop.