jbradtke93 avatar image
jbradtke93 asked

SOC % when entering absorption/float slowly dropping

After having my rig plugged in and ensuring batteries are charged and resyncing SOC to 100%, I notice that over time the SOC percentage at which the system goes into absorption/float slowly drops, about 1% every couple of days. For example, I left a campground on April 26th where I had been plugged in. Left the campground at 100% SOC. My bus has sat since then in direct sunlight with very minimal draw on the system as I have only kept the fridge/freezer running. I have plenty of sun and panel power to be keeping the batteries topped off. Now a little over two months later, the system is going into absorption/float around 70%.

However, The voltages at which it's entering absorption/float seem appropriate. What's causing the drop in SOC percentage and what is the fix? I've noticed it happening for about a year now but would occasionally be in a situation where I could plug in, resync SOC to 100% and restart the cycle all over again.

I have 4x200 watt Renogy panels connected to two 100/30 Victron MPPT charge controllers and Victron 3000 watt inverter/charger along with Victron BMV. Batteries are two 206aH SOK LifeP04 batteries.

Thanks in advance.

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Alexandra avatar image Alexandra ♦ commented ·

You would need to share the settings on the battery monitor for us to help you tweak them.

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jbradtke93 avatar image jbradtke93 Alexandra ♦ commented ·


Here are the battery monitor settings

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img-9792.png (266.9 KiB)
pwfarnell avatar image pwfarnell jbradtke93 commented ·

Ideally the solar controller should be dropping into float after the battery is full. It may be a mismatch between your solar charger settings and your battery monitor settings. We also need your solar charger settings. The charged voltage in the battery monitor should be 0.1 to 0.2V below your absorption voltage.

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1 Answer
derrick thomas avatar image
derrick thomas answered ·

Settings are all wrong for lifepo4. Tail current should be lower maybe half or less of what you have. Peukert should be 1.01 to 1.04 and charge efficiency should be about 99%. That should get you close to accurate.

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seb71 avatar image seb71 commented ·

"Charged voltage" (for the BMV) at 14.6V is also too high.

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