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How to charge a LifePo4 battery

There are a lot of people out on the internet happy to tell everyone that you can charge a Lithium battery (12V, or more accurately 13.7V) with a FLA (Flooded Lead Acid) Charger, no problems.

I would like to say PROBLEM and perhaps the readers of these comments could do with some actual facts to help out.

This includes “Drop in” 12V batteries as these do not do anything particularly special to overcome the Lithium charging conflict with FLA chargers, not to mention alternators.

If you’d like to know more read Lithium Battery Banks – what you need to know and or Lithium Battery Charging requirements – What you need to know.

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2 Responses

  1. Well… I’m going to say “it depends”…

    It depends on the chemistry of the battery.
    You are totally right concerning all 12V batteries or cells using LiFePo4 chemistry, on the other hand, for LiYFePo4 chemistry – containing a pinch of yttrium – thus the only batteries or cells in the world (because of patents) produced by the Winston (or Thunder Sky) brand, there is no problem to use a 12V “Drop in” battery as a replacement for a lead battery, for example in a car or a boat as a starter battery because this chemistry has a maximum charge voltage of 16 volts. Far from the 14.4-14.6 volts which is the normal voltage of an alternator under load.
    Likewise, if we assemble cells (from 40 to 1000 Ah each) to make a 12 or 24 volt battery, the resulting voltage will be lower than the nominal voltage of an alternator. There is not even (in our specific case of nautical use, without the huge consumption found in electric vehicles (EV)), virtually any need for a BMS, a biennial check of the balancing is enough. You can still use a good BMS (REC BMS, TAO BMS, some Deligreen) to sleep easy is in the case of very high consumption or load regime (1C, 2C)
    I have a few that work on cars or vans and on my home made electric inflatable kayak without problems, some are over 10 years old, the SOC is 99% after full controls.
    But as mentioned, they are Winston. They are special.

    And you are absolutely right about the warning given in this article, only those who really know how this kind of battery works and what its characteristics are can safely replace an FLA or AGM with an LFP.
    We can add that a LFP (LiFePo4) is a very safe technology, that it does not catch fire, does not explode, has no dangerous chemistry or acids and that you can even shoot it without any damage other than killing a cell and even withstands overloads by destroying itself without exploding or catching fire…
    Best Regards from France

    1. Well I have certainly learnt something there, I was not aware that Winston cells used yttrium. That is very interesting.

      Does that affect the way a charger should work with them if their nominal voltage is that much higher? Over nominal voltage is of course required for charging and most LFP chargers don’t go that high. Issues?

      Would you still have the possible issues with over-stressing the alternator and possible fire? (Too high a C rating accepted in the cells at low RPM) and current cutoff (presuming you do have a BMS involved) causing shorts in the alternator wrapping?.

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