FLA converter charging a LiFePO4 why does everyone say 80%?

I am cornfused. My system is all set up for LiFePO4 charging and I rarely ever see more than 13.6V charging. I think I have seen 14.2V once in the last three years, although I don't watch the voltage 100% of the time. So why do folks have to replace their stock FLA (non LiFePO4) converters when dropping in a LiFePO4? I hear a lot of folks parroting the FLA converter will get them to 80%. Really? My 13.6V gets me to 100%. I'm asking so I can make good recommendations to folks that just want a drop in replacement and can upgrade over time.

corn18 said:

I am cornfused. My system is all set up for LiFePO4 charging and I rarely ever see more than 13.6V charging. I think I have seen 14.2V once in the last three years, although I don't watch the voltage 100% of the time. So why do folks have to replace their stock FLA (non LiFePO4) converters when dropping in a LiFePO4? I hear a lot of folks parroting the FLA converter will get them to 80%. Really? My 13.6V gets me to 100%. I'm asking so I can make good recommendations to folks that just want a drop in replacement and can upgrade over time.

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The higher operating voltage of LFP means converters will rarely trigger re-bulk. You can typically force this with a power cycle - either by breaker flip or unplug/plug-in converter.

I like using wifi plugs I can control remotely if the unit simply plugs into an outlet.

RV wiring between converter and battery is typically so shitty, the voltage drop is substantial, so the converter "sees" its bulk voltage, and most don't stay there for longer than about 30 minutes. This means you don't get near full during bulk, but only during the very long 13.6V "absorption" phase.

Most work fine when slow charging on shore and get you to full/nearly full. Where they REALLY suck is generator charging.

If battery and converter are near each other (rare) with negligible voltage drop, performance is notably improved.

I'm a big fan of the Powermax PM3-XXXLK line. You can set your own bulk voltage with 13.6V absorption and 13.2V float. They can also be configured to work as a constant current power supply.

sunshine_eggo said:

The higher operating voltage of LFP means converters will rarely trigger re-bulk. You can typically force this with a power cycle - either by breaker flip or unplug/plug-in converter.

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Yep

sunshine_eggo said:

I like using wifi plugs I can control remotely if the unit simply plugs into an outlet.

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Great idea but I use mine to command "coffee" in the morning so I don't have to get out of bed until coffee is ready.

sunshine_eggo said:

RV wiring between converter and battery is typically so shitty, the voltage drop is substantial, so the converter "sees" its bulk voltage, and most don't stay there for longer than about 30 minutes. This means you don't get near full during bulk, but only during the very long 13.6V "absorption" phase.

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A true statement.

sunshine_eggo said:

Most work fine when slow charging on shore and get you to full/nearly full. Where they REALLY suck is generator charging.

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Yep

sunshine_eggo said:

If battery and converter are near each other (rare) with negligible voltage drop, performance is notably improved.

Click to expand...

Yep

sunshine_eggo said:

I'm a big fan of the Powermax PM3-XXXLK line. You can set your own bulk voltage with 13.6V absorption and 13.2V float. They can also be configured to work as a constant current power supply.

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As am I, before I went "blue" I ran a LK unit that the ElectroDacus controlled through the use of a SSR on the 120 side. I set it up as a power supply for fast charging set to 14.2. ( But if I was going to run a generator I would go to 14.4- 14.6 )

So would it be fair to recommend a drop in LiFePO4 and then upgrade parts as able? I look back on my three previous trailers I had with two group 27 FLA batteries. They might last two nights if we ran the furnace. Might. If I asked someone what the best upgrade would be they might say 2x6V golf cart batteries. I would say 1x100Ah LiFePO4 with no changes to your system. Price is close enough nowadays as long as I don't have to swap out parts. Then let them upgrade bits of kit to optimize the LiFePO4 install.

corn18 said:

I am cornfused. My system is all set up for LiFePO4 charging and I rarely ever see more than 13.6V charging. I think I have seen 14.2V once in the last three years, although I don't watch the voltage 100% of the time. So why do folks have to replace their stock FLA (non LiFePO4) converters when dropping in a LiFePO4? I hear a lot of folks parroting the FLA converter will get them to 80%. Really? My 13.6V gets me to 100%. I'm asking so I can make good recommendations to folks that just want a drop in replacement and can upgrade over time.

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Actually you will not hear that stuff around here. You are very much correct.

And in some cases the lithium converters are a worse option. All a bunch of marketing and electrical mystery.

corn18 said:

So would it be fair to recommend a drop in LiFePO4 and then upgrade parts as able? I look back on my three previous trailers I had with two group 27 FLA batteries. They might last two nights if we ran the furnace. Might. If I asked someone what the best upgrade would be they might say 2x6V golf cart batteries. I would say 1x100Ah LiFePO4 with no changes to your system. Price is close enough nowadays as long as I don't have to swap out parts. Then let them upgrade bits of kit to optimize the LiFePO4 install.

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I agree with one caveat, Install a battery monitor that tracks volts/amps. This way you will know where you stand then add your "bits" as you can.