4000 watt Inverter on 12 V?

Devin82m said:

700 watts or less for now. The BMS 120 Amp continuous, with 200 amp surge I believe. The cells are 200 amp with a 600 amp pulse.

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GXMnow said:

1) 1,500 watts on a 12 volt system is about 150 amps. How long will the wire run be? I would not go smaller than about 2/0 at that current. Windy Nation rates their 2/0 at 325 amps, but that is 105C temp rated, the NEC lists 75C 2/0 cable at 175 amps. But you also need to take the length in account. Losses at 12 volts add up fast. Lose 1.2 volt, and that is 10%.

2) I do not know that Victron unit. Are the voltage settings able to be dialed down for 12 volt? 15 amps will charge slow, as that is under 200 watts, but it will charge.

3) I am happy using the app in my JK BMS, the Overkill looks similar.

4) Setting the charge controller to 3.4 volts per cell on LFP will get you about 95% charged. The discharge side is a bit tougher. LFP cells near 50% do not change voltage much at all. Even after doing a full cycle to know your full capacity, you would need to watch the battery SOC to see when you get close to 50%. Most inverters etc. only go by voltage, and with LFP, you wont se a drop in voltage until down more like to 20%. Are you doing this for the storage of the cells? You could run a heater on a timer, once you know what your capacity is. Dial it in from the SOC on the BMS.

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Devin82m said:

As for cable length, I don't know, 1ft to 2ft, just enough to mount it on a board directly above the pack. I assume once I convert to 24v the cable will be overkill for that system and totally reusable?

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Devin82m said:

Hey guys, since my BMS is on a 30 day back order, what should I do with my cells that are at such a high state of charge? They have already sat for a week.

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smoothJoey said:

What SOC are they at?

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Devin82m said:

3 tested as 3.28 and one as 3.25


"3 tested as 3.28 and one as 3.25"

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smoothJoey said:

I'm guess that they are at the same voltage as they were shipped to you.
That is not a high state of charge and requires no action.
If they were above 3.45 volts per then I would maybe do something about it.
Do you have a capacity tester?

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Devin82m said:

No, no capacity tester, do you suggest a specific one?

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smoothJoey said:

I have this one.

USB Adjustable Constant Current Electronic Load, LCD Screen, Configuration of CPU Fan, Battery Capacity Tester, Module 150W 200V 20A Over Voltage, Over Current, and Overpressure Alarm : Amazon.ca: Tools & Home Improvement

USB Adjustable Constant Current Electronic Load, LCD Screen, Configuration of CPU Fan, Battery Capacity Tester, Module 150W 200V 20A Over Voltage, Over Current, and Overpressure Alarm : Amazon.ca: Tools & Home Improvement

www.amazon.ca

Works as expected.
You could do individual capacity tests on your cells.
I assume you have a bench psu to charge them.

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