LifePo4 Charge Performance
Thinking seriously about replacing our two GC2's with a pair of 100ah LifePo4's. Hearing a lot of chatter about how lithiums accept a charge much quicker than lead cells. Very familiar with how ou...
Forum Discussion
With FLA and AGM, the SOC reached when Absorb starts depends on the "charging rate", where higher amps will raise the battery voltage sooner at a lower SOC (but you still get it all done faster because the Absorb tapering amps are still higher)
A lower charging rate makes the time it takes to get the battery to the high set point (Vabs) longer and the SOC higher before amps taper.
It is easy to show this on graphs with a charger on 120v supply, but not so easy with solar where the input is changing all day as the sun goes up and then down. A 20 amp controller might be at 20 amps at noon, but 10 amps later in the day with the sun lower.
So you can invent a scenario for when the batts get full enough and what the amps are by then for when to say amps are tapering from being in Absorb or just from the fact the sun is getting lower.
If the situation is two GC2s and 200w of solar, mid-summer, nice day, you can expect the battery bank that was low at sunrise, to reach Vabs in the afternoon when solar amps are lower than back at high-noon, so the SOC will be in the 90s % zone before Absorb starts from the battery having reached Vabs. Could be at 97%, whatever. It could be some of each effect making the amps taper later in the day.
Amps tapering later in the day from the sun getting lower also happens with LFPs!
So----if that is typical (what I see with my solar anyway), then there will not be much difference if you swap out your FLAs and put in the same AH size bank of LFPs and leave your solar the same. Just a little "faster" near the end of the daylight period.
You can make the scenario look better for the LFP side if you get the batts near full before lunch and the sun and solar amps are still rising!
So it is necessary to pin down just what the actual scenario is with the whole story so you can make comparisons with actual numbers. "Arm-wavy answers" are for salesmen ("drummers")
LFPs have their place, such as for weight savings, but this "faster charging" business is too much smoke and mirrors the way it is so often presented. You want to see some numbers and get your calculator working.
It can come out better for the LFPs by some amount. The next question is whether that amount is worth the Money for your own situation.
The OP knows now he can get 135 - 115 = 20 more AH in his 3 hours of gen time if he swaps over to LFP. He might think that is worth whatever 200AH of LFP costs or not . ($1,500 ? Yipes!) Only he knows that.
A lower charging rate makes the time it takes to get the battery to the high set point (Vabs) longer and the SOC higher before amps taper.
It is easy to show this on graphs with a charger on 120v supply, but not so easy with solar where the input is changing all day as the sun goes up and then down. A 20 amp controller might be at 20 amps at noon, but 10 amps later in the day with the sun lower.
So you can invent a scenario for when the batts get full enough and what the amps are by then for when to say amps are tapering from being in Absorb or just from the fact the sun is getting lower.
If the situation is two GC2s and 200w of solar, mid-summer, nice day, you can expect the battery bank that was low at sunrise, to reach Vabs in the afternoon when solar amps are lower than back at high-noon, so the SOC will be in the 90s % zone before Absorb starts from the battery having reached Vabs. Could be at 97%, whatever. It could be some of each effect making the amps taper later in the day.
Amps tapering later in the day from the sun getting lower also happens with LFPs!
So----if that is typical (what I see with my solar anyway), then there will not be much difference if you swap out your FLAs and put in the same AH size bank of LFPs and leave your solar the same. Just a little "faster" near the end of the daylight period.
You can make the scenario look better for the LFP side if you get the batts near full before lunch and the sun and solar amps are still rising!
So it is necessary to pin down just what the actual scenario is with the whole story so you can make comparisons with actual numbers. "Arm-wavy answers" are for salesmen ("drummers")
LFPs have their place, such as for weight savings, but this "faster charging" business is too much smoke and mirrors the way it is so often presented. You want to see some numbers and get your calculator working.
It can come out better for the LFPs by some amount. The next question is whether that amount is worth the Money for your own situation.
The OP knows now he can get 135 - 115 = 20 more AH in his 3 hours of gen time if he swaps over to LFP. He might think that is worth whatever 200AH of LFP costs or not . ($1,500 ? Yipes!) Only he knows that.
