Question on switching to LiFePO4 batteries.
I'm going to replace my 2 lead acid batteries in my Bigfoot truck camper with two 100ah LiFePO4 batteries. I've previously installed a 4 way battery selector switch to allow me to keep one of my batt...
Forum Discussion
With LFP’s you’d be better off to just leave them in continuous parallel, no longer a need to isolate one…
Charge them both to 100% before putting them in parallel…
I will add here what I’d penned in another thread awhile back, but take note of item #2, because determining state of charge (SOC) with LFP is problematic due to it’s relatively FLAT discharge curve (meaning relatively near-stable voltage):
*************
Well, since (your camper) spends much of it’s life plugged in, you might then consider doing what I and many others with LFP’s do…
1) Simply add an automotive ‘side-post’ battery knife style disconnect switch to the LFP’s two terminals (the most accessible), so that the battery can hibernate isolated when not in use…Once isolated, the self-discharge rate for LFP’s is practically non-existent, say over a 6 month period. Hibernation should be done with the battery at about 50-60’ish% state of charge (SOC), this to keep LFP ions in appropriate equilibrium…
2) To best determine ‘accurate’ SOC’s with LFP’s (otherwise somewhat problematic), you’ll want a good LFP compatible, shunt based SOC meter, like Victron’s ‘smart-shunt’ with Bluetooth (simply installs in NEG battery cable)…Reads like a gas gauge and provides SOC, volts, amps and history…
3) With battery disconnect during these periods of ‘non-use’, your existing on-board converter-charger (via shore power) will take over and continue to supply 12v power to the camper…
4) When restoring your batteries back to a full charge, most any OEM charger that’ll output 14.X volts (not to exceed 14.6v) will do - however, the key here is, once the batteries are fully charged and *balanced (say, another 15-20 mins after achieving 100% SOC…), discontinue charging (this, in the interest of battery longevity), by shutting off your generator (or if shore power, via on-board converter-charger’s breaker), thereafter running off battery power…
* Note, the cell balancing cycle can be observed via Bluetooth per the slight cycling of amps and volts until such cycling stops (see item 2).
5) Unlike wet-cells, there’s no need to ‘routinely’ restore LFP’s back to a 100% FULL charge…85-95% is quite sufficient thanks to LFP’s far deeper DOD (depth of discharge) - But to aid with battery longevity, you’ll only want to do a FULL charge occasionally, and for just two reasons:
a) Periodic cell re-balancing (this process begins after achieving 100% FULL Charge).
b) Meter resync (concurrent with a full charge) - to resolve cumulative SOC meter drift which naturally develops over a time…
6) At this point you might sense (as with other type batteries) that solar harvest will help minimize the frequency for having to run your generator, as does LFP’s deeper DOD…
3 tons
Charge them both to 100% before putting them in parallel…
I will add here what I’d penned in another thread awhile back, but take note of item #2, because determining state of charge (SOC) with LFP is problematic due to it’s relatively FLAT discharge curve (meaning relatively near-stable voltage):
*************
Well, since (your camper) spends much of it’s life plugged in, you might then consider doing what I and many others with LFP’s do…
1) Simply add an automotive ‘side-post’ battery knife style disconnect switch to the LFP’s two terminals (the most accessible), so that the battery can hibernate isolated when not in use…Once isolated, the self-discharge rate for LFP’s is practically non-existent, say over a 6 month period. Hibernation should be done with the battery at about 50-60’ish% state of charge (SOC), this to keep LFP ions in appropriate equilibrium…
2) To best determine ‘accurate’ SOC’s with LFP’s (otherwise somewhat problematic), you’ll want a good LFP compatible, shunt based SOC meter, like Victron’s ‘smart-shunt’ with Bluetooth (simply installs in NEG battery cable)…Reads like a gas gauge and provides SOC, volts, amps and history…
3) With battery disconnect during these periods of ‘non-use’, your existing on-board converter-charger (via shore power) will take over and continue to supply 12v power to the camper…
4) When restoring your batteries back to a full charge, most any OEM charger that’ll output 14.X volts (not to exceed 14.6v) will do - however, the key here is, once the batteries are fully charged and *balanced (say, another 15-20 mins after achieving 100% SOC…), discontinue charging (this, in the interest of battery longevity), by shutting off your generator (or if shore power, via on-board converter-charger’s breaker), thereafter running off battery power…
* Note, the cell balancing cycle can be observed via Bluetooth per the slight cycling of amps and volts until such cycling stops (see item 2).
5) Unlike wet-cells, there’s no need to ‘routinely’ restore LFP’s back to a 100% FULL charge…85-95% is quite sufficient thanks to LFP’s far deeper DOD (depth of discharge) - But to aid with battery longevity, you’ll only want to do a FULL charge occasionally, and for just two reasons:
a) Periodic cell re-balancing (this process begins after achieving 100% FULL Charge).
b) Meter resync (concurrent with a full charge) - to resolve cumulative SOC meter drift which naturally develops over a time…
6) At this point you might sense (as with other type batteries) that solar harvest will help minimize the frequency for having to run your generator, as does LFP’s deeper DOD…
3 tons
