Hi guys I have been researching a lifepo4 setup for my 4x4 and all roads seem to lead to this forum so I'm here asking for some help as I am a little out of my depth.
My old 4x4 has a single 250ah deep cycle AGM which runs a fridge, camp lights and the radio for a few days at a time with plenty of reserve for starting the engine.
New 4x4 has no room for dual batteries, or such a big single unit. It comes factory with a H9 AGM under the driver's seat. 190a (smart?) alternator, gasoline V8 turbo, 1.7kw starter motor.
I am from Australia. The coldest we see is around 0°C in winter. So no drastically high or lows temps for the battery to deal with.
I would like to replace the under seat battery with 4 x 200-280ah lishen or eve lifepo4 cells but choosing a BMS has me going around in circles.
Starter should draw 1700/12 =140 amps for let's say 5 seconds on average, or 30 seconds at a time during a no-start scenario.
Winch (not yet fitted) will anecdotally draw 200-400 amps when loaded up. Only used for 30 seconds, then allowed to cool.
Inrush current for both should be 2-3 times the above for <1 second?
Most prismatic cells seem to be good for 1C continuous or 2C for upto 30 seconds. Seems like 200ah cells would be on the limit but the 280ah would give me some headroom while stretching the budget.
1) do I just slap a 250a Daly on it and not worry? Best option looks like a 600a Chargery setup, but spendy. Or the 300a Chargery, maybe borderline. Any other options I've missed?
2) how come none of the 200-300a 12v pre-built lifepo4 batteries for sale are rated for cranking? Seems like they would have enough C rating and borderline enough BMS.
3) convince me I need a BMS at all. Why not spend the money on the bigger cells instead. At 190amp and Max 14.6v output from the alternator, I can never overcharge 280ah cells, right? And as long as I never run the winch or starter motor for 10 mins straight I can't see over discharge being a problem. No sub zero or +50°c temps to deal with. If we take care of cell balancing some other way, what else is the BMS doing for me? I will probably have a separate volts/current/temp display somewhere, and a manual isolator switch in easy reach in case things go pear shaped.
3.1) I also can't see how the BMS cutting the battery in/out with the engine running and potentially high current loads would be doing any good for to electrical system. This car has a million computers all talking to each other and are quite complicated to work on. Maybe this isn't relevant. Clearly I'm no electronics engineer.
Thanks for reading
My old 4x4 has a single 250ah deep cycle AGM which runs a fridge, camp lights and the radio for a few days at a time with plenty of reserve for starting the engine.
New 4x4 has no room for dual batteries, or such a big single unit. It comes factory with a H9 AGM under the driver's seat. 190a (smart?) alternator, gasoline V8 turbo, 1.7kw starter motor.
I am from Australia. The coldest we see is around 0°C in winter. So no drastically high or lows temps for the battery to deal with.
I would like to replace the under seat battery with 4 x 200-280ah lishen or eve lifepo4 cells but choosing a BMS has me going around in circles.
Starter should draw 1700/12 =140 amps for let's say 5 seconds on average, or 30 seconds at a time during a no-start scenario.
Winch (not yet fitted) will anecdotally draw 200-400 amps when loaded up. Only used for 30 seconds, then allowed to cool.
Inrush current for both should be 2-3 times the above for <1 second?
Most prismatic cells seem to be good for 1C continuous or 2C for upto 30 seconds. Seems like 200ah cells would be on the limit but the 280ah would give me some headroom while stretching the budget.
1) do I just slap a 250a Daly on it and not worry? Best option looks like a 600a Chargery setup, but spendy. Or the 300a Chargery, maybe borderline. Any other options I've missed?
2) how come none of the 200-300a 12v pre-built lifepo4 batteries for sale are rated for cranking? Seems like they would have enough C rating and borderline enough BMS.
3) convince me I need a BMS at all. Why not spend the money on the bigger cells instead. At 190amp and Max 14.6v output from the alternator, I can never overcharge 280ah cells, right? And as long as I never run the winch or starter motor for 10 mins straight I can't see over discharge being a problem. No sub zero or +50°c temps to deal with. If we take care of cell balancing some other way, what else is the BMS doing for me? I will probably have a separate volts/current/temp display somewhere, and a manual isolator switch in easy reach in case things go pear shaped.
3.1) I also can't see how the BMS cutting the battery in/out with the engine running and potentially high current loads would be doing any good for to electrical system. This car has a million computers all talking to each other and are quite complicated to work on. Maybe this isn't relevant. Clearly I'm no electronics engineer.
Thanks for reading