question

stephanv9 avatar image

Smart Solar 100/30 over voltage every day

I have a MP100/30 charger. It's set up to charge a LifePO4 battery and despite my charge profile settings (absorption 14.2, float 13.5, absorption duration fixed at zero minutes), I'm seeing 15 volts plus in the history screen every day. Even when the trailer is sitting in the rain on an overcast day. The only thing running is a small 130l compressor fridge. Worried about damaging my 200ah new battery. Any ideas would be appreciated. Images of the settings and history below. Cheers. Stephan

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MPPT - Solar Charge Controllermppt smart solarovervoltageovercharging
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3 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

What battery do you have exactly?

Maybe the BMS is cutting off the charge current due to a high cell voltage. In that moment the output voltage of the MPPT can rise for a few seconds.

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Hi @Matthias Lange - DE I am using a lithium valley Chinese 200ah battery. https://www.lithiumvalley.com/battery/12v-200ah-lifepo4-battery/. Over charge voltage is 14.65 so with my controller set at 14.2 it would be unlikely to be the problem. . Keen to know any other thoughts on this. Cheers Stephan

14.65V for the whole battery but the BMS should also cut off charge if only one cell gets to high.

Do the battery have some kind of smartphone app or interface to check the cell voltages?

JohnC avatar image
JohnC answered ·

Hi @Stephanv9

It may be just 'spikes', possibly caused when your fridge switches in or out.

Try setting up the Trends graph with battery V and Current. That may indicate something that you can relate to the cause of a spike above the set V level.

The mppt can overshoot, but shouldn't worry your battery.

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Hi @JohnC, Thanks for the quick reply. I tried setting up the trend for a while this morning. Interestingly, the voltage seems to jump up to 15 or sometimes even 16.28 volts for a second or two every once in a while. I just caught it three times in the space of 5 minutes. The fridge cutting in and out doesn't seem to have any bearing on it. It happened a bit before the status changed to float. There's nothing else in our camper other than some LED lights, which were not on. I'm a bit confused over it to be honest.

I see some other suggestions that recommend turning the absorption voltage down to 13.95 instead of 14.2, but I think that was to counteract "spikes" when load goes on and off when the battery is fully charged. Do you have any other suggestions? Cheers Stephan

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@Stephanv9

I agree that it appears to be a battery/bms issue. Perhaps try lowering the charge V(s) to where it will accept current without tripping. Maybe then it can sort out itself any unbalanced cells, but that might take time too.

I hope it has good warranty cover.. :(

Hi @JohnC, thanks for your input so far. The battery (on paper) has a 2 year replacement warranty and a further 4 years pro rata warranty. I’ve only had it for a few months and bought it from a NZ store. The big question is how do I start a conversation and prove that the battery is the issue? I can imagine the guy saying it’s fine as it’s holding charge and working. If it wasn’t for the blips on the controller I’d never know it was doing anything untoward. Is there anything you suggest to prove this out categorically before I touch base with the supplier? Thanks again.

@Stephanv9

When I say 'issue', I really mean the cause of the spikes. It may be how that kit is supposed to perform, may be caused by your charge settings?

Do your homework and whatever testing you can manage. Save your screenshots and ask the batt/bms supplier to comment. Even link them here.. they can sign in and respond here too.

I very much doubt this is caused by the mppt, and it may be doing no real harm. But you won't know unless you ask, and at least register a 'complaint' as honestly and helpfully as you can.

Tis beyond my experience, but I'd love to hear how you go..

seb71 avatar image
seb71 answered ·

Is the temperature compensation disabled?

That setting is missing from your screenshots.

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Hi @seb71 , Temp compensation is disabled. Cheers. Stephan