question

dixonge avatar image
dixonge asked

Lost all confidence in my settings

Here are my basics:

4 100W panels in series/parallel

4 Duracell EGC2 (Deka GC-15) in series/parallel

BMV-712

SmartSolar MPPT 100/30

This is in an RV - no grid. We live in it.

After I rearranged where things were mounted my SOC on the BMV-712 was reset to --

I've been waiting to sync the SOC back to 100% but I am unable to disconnect everything for 12 hours to verify the actual battery voltage. In the meantime, my system has never left the bulk state of charging, in spite of multiple mostly sunny days.

Current BMV-712 settings are as follows:

Capacity: 460Ah

Charged voltage: 14.3V

Discharge floor: 50%

Tail current: 4%

Peukert: 1.27

Charge efficiency: 85%

Current threshold: 0.10A


Current MPPT 100/30 settings are as follows:

Absorption: 14.6v

Float: 13.9v

Temp compensation: -18mV/C


Do any of these settings look off?

MPPT SmartSolarBMV Battery Monitor
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4 Answers
seb71 avatar image
seb71 answered ·

That is a big battery (460Ah/12V). From your post it appears that you also have some loads drawing energy. So your 400W PV array might not be big enough for your energy needs.

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pwfarnell avatar image
pwfarnell answered ·

The settings look OK. The question I believe is more about what charge you are getting in fro m the solar compared to your usage if you are permanently in bulk. What charge condition were the batteries in when you installed the system. What voltage, current and power are you getting from the panels into the MPPT, and what voltage and current out of the MPPT and what current into the batteries. Do you have a bad connection on one of the parallel solar panel strings. How much power are you using.

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rickp avatar image
rickp answered ·

I have 4 panels running, and tried various schemes to see which worked best. A full series arrangement worked best for me. I purchased a large solar charge controller, the SmartSolar 250 | 100, so voltage or amperage wouldn’t be a concern in any configuration, and to allow for expansion.

If your panels will not overload your SCC, experiment to see what wiring arrangement gives you the best performance.

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dixonge avatar image
dixonge answered ·

follow-up:

1 - underpaneling (or at least under-configuration) is probably a major culprit here - most charge rates I have seen indicate 10% is a good target, so 46amps in my case. I typically see no more than 20-25. All good in the summer, not so much when the sun starts to drift south.

2 - maintenance - I let the water get low. A few cells may have had the top edge of the plates get exposed. Not much, but close enough that the SG is *bad* on all cells. I've been trying to equalize but the panels struggle to get to full charge, much less an EQ cycle on top of that. This is true even when I split the bank up into two pairs and charged them separately.

3 - settings - best I can tell, my charge controller settings are fine

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