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darren-maddox avatar image
darren-maddox asked

Battery dropping immediately to between 12 and 12.2 at 9pm. Are my readings normal?

db69032d-3271-4ec4-ba97-88b81215375f.pnghello I am completely new to all of this and currently learning. I have Carbon Lead batteries x 2 connected to an MPPT.


Throughout the day my battery is on float at 13.6v, at 9pm every night my charger turns off and my battery readings immediately drops to 12v - 12.2v.


Is this normal? Also overnight the battery level drops to below 12. Is this ok / normal as I’ve been told not to let it go below 12.2 but seem to have no control over it?

Last question, can I not view the the 2 c 12v batteries separately or can they only be displayed as one reading on the connect app?


battery charging
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2 Answers
kevgermany avatar image
kevgermany answered ·

You have the batteries in parallel. They look like a single battery to the system. So no individual values can be shown.

12.2 post float is rather low, unless there's a significant load on them. 12.6 to 12.7 is more what you would be expecting.

You might increase absorption voltage to 14.4V if it's not there already.

But what is the temperature there?

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darren-maddox avatar image darren-maddox commented ·

we are in a heat wave it’s between 28c degrees and 38c next week. Will this have a significant effect?

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kevgermany avatar image kevgermany ♦♦ darren-maddox commented ·
Yes, the MPPT has a temp sensor and will lower voltages quite a bit at 38C. However your voltage drop seems to be excessive.

Could be that they're not charging fully, please post a screen shot of the battery settings in the MPPT.


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christern avatar image
christern answered ·

I would guess that your batteries are old and needs replacing. To my knowledge old batteries seem to accept charging but when not connected to a charging source (eg solar panels) their voltage drops after a few hours. Could that be the case?

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darren-maddox avatar image darren-maddox commented ·
This is a a brand new system
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christern avatar image christern darren-maddox commented ·

Try to connect each battery at a time to a charger connected to grid and see if that 1) gives some indication of the problem and 2) what happens when you put them back within your system. Sometimes also brand new batteries are faulty.

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