SOC Chart for Lifepo4

Had a good SOC Chart for my sealed setup hanging on the wall next to the battery monitor for reference. Been looking for something similar to it but haven't been able to find one. I know it's not the same due to the fast drop towards the end but is there something you use that works?

The voltage curve for LiFePO4 is not linear and the voltage settles a lot when they are done charging. Highly recommend using a shunt to figure SOC for LiFePO4.

Voltage to determine SOC alone, even when loads are disconnected, is difficult.

Will Prowse said:

The voltage curve for LiFePO4 is not linear and the voltage settles a lot when they are done charging. Highly recommend using a shunt to figure SOC for LiFePO4.

Voltage to determine SOC alone, even when loads are disconnected, is difficult.

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Figured as much Will. Have a blue sea 500a 50mv shunt and a powermon BT monitor in place. Waiting on a full charge to sync it at 100%. Not sure I want (or easily can) take it to bottom state for more accurate reading. Was looking to have a ref hanging for the wife. Better off making one based on my own observations though as chemestries/manufacturing can also be a big factor. Doesn't hurt to ask though!

I work on the principle if it starts with 13 then it’s good, 12 not so good, 11 very bad, 10 light a candle, 9 u gone darn f’d up

I use these as a general reference but mainly rely on coulometer to tell me SOC

According to the log from the Valance Software, my battery hit 20% SOC at 12.6 volts. That was during a defrost cycle on the fridge, so had a 35 amp load during that time as well.

Power4life said:

I use these as a general reference but mainly rely on coulometer to tell me SOC

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Your charts do explain why Ian recommended to raise the low V disconnect from default of 10.5 to 12.

erik.calco said:

Your charts do explain why Ian recommended to raise the low V disconnect from default of 10.5 to 12.

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I keep my LVD set to 11.85V because my cells start to drift out of balance below this point. Probably set it lower once I get some active balancers installed. I dont intend to continually go this low but I like to know that I can if need be. Still getting 125 amp hours from a 120 ah pack at this setting though

Active balancers won't stop that. I have the qbnnm active balancer thing and it doesn't stop them going out of balance, it just brings them back much quicker, but still a few hours. Under 12v the gain is so minimal it isn't worth it, same as above 14v.

ScoTTyBEEE said:

Active balancers won't stop that. I have the qbnnm active balancer thing and it doesn't stop them going out of balance, it just brings them back much quicker, but still a few hours. Under 12v the gain is so minimal it isn't worth it, same as above 14v.

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Oh man, thank you so much for telling me this. I was looking at getting that exact active balancer and I was curious if it was worth going to the trouble of installing them just to squeeze an unknown amount of energy out of the pack. If it only took a few minutes to balance I would be all for it but hours seems to not warrant the installation for minimal gain. Would there be any other reason I should look in to getting the balancer? I am happy with my current capacity but it never hurts to get more. What's your experience with the qbnnm?

Makes a high pitch noise which is annoying, but works well as far as keeping everything balanced. I would say just keep your cells in the voltage range that they don't go out of balance though as it's just healthier in the long run to stay within 12-14v. You already have 5ah bonus so just forego that and you'll have 120ah batteries in safe range, which is how these things are supposed to work really.

I'm of the opinion there isn't a decent bms out there yet that does everything we want but there will be within a year or so, so don't go spunking money up the wall on all this additional stuff and just wait for something that has active balancing, bluetooth, low temp disconnect, fully customisable etc all in one package and get that. In the meantime use a victron battery connect to protect the batteries as it's always good to have a last resort device regardless and use a cheap daly bms and wait for something better.

ScoTTyBEEE said:

Makes a high pitch noise which is annoying, but works well as far as keeping everything balanced. I would say just keep your cells in the voltage range that they don't go out of balance though as it's just healthier in the long run to stay within 12-14v. You already have 5ah bonus so just forego that and you'll have 120ah batteries in safe range, which is how these things are supposed to work really.

I'm of the opinion there isn't a decent bms out there yet that does everything we want but there will be within a year or so, so don't go spunking money up the wall on all this additional stuff and just wait for something that has active balancing, bluetooth, fully customisable etc all in one package and get that. In the meantime use a victron battery connect to protect the batteries as it's always good to have a last resort device regardless and use a cheap daly bms and wait for something better.

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Thanks again. The info is much appreciated