Anyone completed a DIY Li-ion battery charger?
I have some small 6ah-7ah 12v batteries that I need a charger for.
Any pointers to a source of schematic etc would be a great help.
I have the lead-acid type charger that offers a well regulated charge but not sure if I could use this for Li-ion?

 

I think there are such batteries (for automative use) that have circuitry to enable using a Lead Acid charger, but I would verify that before trying it. If it is not so equipped, it could explode.

 

This is battery type in question.

 

Hey, @MaxHeadRoom. The basic strategy for Lithium Ion charging is CC/CV (Constant Current/Constant Voltage). You are probably already familiar with this but briefly:

Constant Current of ~500mA to ~1A per cell is applied to the battery up to 4.2V per cell;
Constant Voltage of 4.2V per cell is maintained until the current drops to ~0A.

There are other things that must be managed, though, that complicate things.

Pre-charging of cells that are below a safe threshold for full charging (typically 2.5V)
Thermal monitoring to shut down charging if the temperature gets too high.
Balancing of cells to keep them very close to the same voltage to avoid reversing which is very hazardous.

But, since that battery doesn’t have a balancing connector it leads me to… hrm…

INLINE UPDATE
I tracked down the information about that battery:

It’s LiFePO₄ which is special.
It’s a drop in replacement for SLA batteries!

That means it can be charged as if it was an SLA.

It said this the battery has:

Circuitry designed to prevent the battery from operating outside its safe operating levels. Includes: over-current & over-voltage protection, regulates operation during high & low temperatures, balanced charging, and short circuit protection.

So, basically a built in BMS. Just give it 13.8V at a couple of amps and have a beer.

 

So, basically a built in BMS. Just give it 13.8V at a couple of amps and have a beer.

Yes, that is what I was referring to in post #2.

 

I tracked down the information about that battery:
It’s LiFePO₄ which is special.
It’s a drop in replacement for SLA batteries!
That means it can be charged as if it was an SLA.
It said this the battery has:
Circuitry designed to prevent the battery from operating outside its safe operating levels. Includes: over-current & over-voltage protection, regulates operation during high & low temperatures, balanced charging, and short circuit protection.
So, basically a built in BMS. Just give it 13.8V at a couple of amps and have a beer.

Thanks.
I haven't really delved in to Li-Po charge requirements.
I also need a few extra and looking to use these SLA types as a sub, There is not much difference in size. And a little cheaper.
There are others like the LiFePo that have a few tabs other than the +ve & -ve . I assume these would use the individual cell connection charger.
I can use my regulated lead acid automotive battery charger then for both .!

 

Thanks.
I haven't really delved in to Li-Po charge requirements.
I also need a few extra and looking to use these SLA types as a sub, There is not much difference in size. And a little cheaper.
There are others like the LiFePo that have a few tabs other than the +ve & -ve . I assume these would use the individual cell connection charger.
I can use my regulated lead acid automotive battery charger then for both .!
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LiFePO₄ is a great technology. Unlike other Li-based cells, LiFePO₄ has a non-flammable electrolyte. This means no electric blowtorches, which is a big plus. A little less power density which is why you don’t see them in phones but a lot more safety which is why you see them all sorts of other places. They also weigh a lot less than PbSO₄.

Also, come on—it’s obvious why you want “Mighty Max” batteries…

 

Also, come on—it’s obvious why you want “Mighty Max” batteries…

Har Har