Martin,
Thank you. You have answered a lot of my questions. Regarding my AGM charger, it may be even worse than "sub-optimal". That charger finishes its charging cycle with a desulfation process that would be of no use to LiFePo4 batteries. In addition, that charger is known to shut down when the battery doesn't act as expected. It might just assume the new battery is a bad AGM battery once the internal BMS stops accepting a charge.
On 4/28/2020 7:58 AM, martin Thacker wrote:
I've been working on a team in Germany developing some lithium batteries and BMS for outdoor and marine usage. There are huge differences in BMS quality and feature sets but what almost every Lithium BMS would do for you is to cut off charging to the batteries when they reach a pre determined 100% charge level to prevent you from overcharging the pack. For LiFePO4 this will be about 3.65v for a single cell or for a 4 Series 12.8V pack that would be 14.6V.
I don't have so much experience with AGM but your AGM charger is probably putting out 14.4 - 14.8V which is so close to the 14.6V that it would not be a big problem for you I would think, not dangerous in any case. Your BMS will shut off the charge to your batteries so that they don't go above that 14.6 level once it has been reached so there is no risk of over charging the battery. Your AGM charger will probably try to taper the charge according to a profile set for AGM so it would be sub optimal for LiFePO4.
On Tue, Apr 28, 2020 at 12:31 PM greenpjs04 <forums@greensdomain.com> wrote:
Wow! Thank you for all the responses. I will investigate all your
suggestions further. One topic that came up but has me confused is the
BMS needed for LiFePo4 batteries. From past research, I know that some
cells offered for sale are just that - cells without any BMS. To use
those, I would have to add a BMS designed for LiFePo4 chemistry.
DualPro's website says their chargers "can" be programmed for LiFePo4
but I doubt that applies to my 10 year old AGM charger.
So, moving on to the LiFePo4 battery packs with built in BMS's, how does
one charge those? I found very little detail mentioned. Just things
like "Includes BMS!" and similar claims. Can any charger with a voltage
above the battery voltage be used to charge these batteries? In other
words, does the internal BMS fully protect the batteries by handling
charge rate and monitoring state of charge to avoid over-charging?
Pat
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