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Forum Index : Electronics : Lithium Battery Management

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shallowal
Regular Member

Joined: 26/07/2018
Location: Australia
Posts: 42
Posted: 06:52am 23 May 2020
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A question for the battery guru's if I may?.
I'm looking at replacing my AGM caravan battery with a Lithium variety. The particular one I am looking at has an inbuilt BMS including cell balancing (Solarking).
What I am considering is that the solar charger on the van is quite old and not designed for Lithium batteries, however, if the battery has built in BMS, then cant it manage the charge (& discharge) itself?.
So from a charging POV all I need is to supply it with sufficient volts from the solar array and let it sort itself out.

All comments welcome.
Allan
 
ryanm
Senior Member

Joined: 25/09/2015
Location: Australia
Posts: 147
Posted: 08:17am 23 May 2020
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The inbuilt BMS would be (assuming it's pretty standard) for cell balancing, under voltage lockout, over voltage lockout and overcurrent protection.

This isn't going to stop the charger from trying to float the battery at a lower voltage and Lithium doesn't like being trickle charged. Even if the BMS could detect this it's only method to stop it would be to isolate the terminals cutting connection not only to the charger, but the load as well.

There are some really cheap lithium compatible chargers on the market now. You can get a PWM 30A domestically for $90.

https://www.roadtechmarine.com.au/12v-24v-30a-pwm-solar-charge-controller-with-lcd-display-for-lead-acid-and-lithium-batteries/p/MP3755

There's also MPPT around for not much more, expecially if you're willing to shop on Aliexpress.
 
ryanm
Senior Member

Joined: 25/09/2015
Location: Australia
Posts: 147
Posted: 08:22am 23 May 2020
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Same company has 20A DC-DC chargers which have a solar input as well so you can charge from the car while driving. Mate has one and it works well. Super cheap, think they're sub $200.
 
shallowal
Regular Member

Joined: 26/07/2018
Location: Australia
Posts: 42
Posted: 01:52am 27 May 2020
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Thanks Ryan,
After much research I discovered that same point as you made, that the end float charge is the problem and can cause permanent damage to the cells. That option you linked too looks pretty good, so I'll have a look for something compatible with the caravan.
I already have a DC-DC lithium compatible charger yet to be installed, but unfortunately it doesnt have a solar capability.
Allan
 
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