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Hi All:

I'm looking around for ideas on how to charge a 20S pack of Molicel P42A's. I'd like a bit of adjustability as overall pack voltage would be 82-84 V. I'm considering a couple of power supplies in series but would appreciate any ideas or suggestions. The project is presently using a PbA charger for a 72V nominal system but I don't want to rely on the BMS to cut off the charge. This charger says it goes up to 88 VDC but I haven't actually done a 100% charge yet to see where it starts cutting off. I'd be looking for 5-10 Amp charge rate.

TIA
 

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If you like DIY, both of these work well.

Depending on the amperage you need, Meanwell makes a variety of PSU's that work well in series. I've been using the SE-600 24v PSU's in series since 2016 as my main 82v charger. I'm in progress building a much larger charger from 8 of them. This will get me increments of 12S, 16S, 20S, 24S, 28S, 32S and 36S. These PSU's lack current limiting. When you load them too heavily, they shut off. I've been using a bank of resistors as my current limiter. This does make some heat, but it's simple and cheap and easy to implement. This is 16S/66v and 20S/82v chargers made from these PSU's. You'll notice that they both have a resistor bank on them for current limiting. At about $75 per SE-600 PSU, this does get expensive, but then you'll also get about 25 amps charge current too! At $300, there's not a lot of good options for a single charger that delivers 25 amps and 82v. This is about the cost of an SE-600 PSU based 82v charger.




If you can forego adjustability, Lenovo 190w laptop PSU's are super cheap. Get on ebay and look for them. You should have little problem finding them for $16-18 each. I've built probably 8 chargers from these PSU's for myself or friends. Not one has ever stopped working after many years of use. Right now I have 1 of them and it sees regular use. Since they are 20v PSU's, you will get a little more than 80v from them. Mine makes 82.3v...which is close enough to 82v that I don't care. HP makes a 230w PSU. I have bought several of them and they are just a little more cost than the 190w Lenovo PSU's. The big advantages they have is easy access to the circuit board and more amperage. Getting to the circuit board in a Lenovo PSU is a giant PITA! The HP PSU's are much easier to take apart. I'll be looking at them closer to determine the components that set the output voltage. I'm pretty sure I already know what needs to be adjusted to set the output voltage. I'd like to adjust them to suit charging a bit better. I'm pretty sure they will adjsut down to about 18v and up to about 22v. This is enough range to get dead nuts at 82v or some other total voltage. The first picture is one that I made in 2016 and sold to a friend in 2018. The second picture is my current charger which I built to replace the one I sold. The PSU's are spaced apart a little so air can get in between them. Add a fan and they never get warm, but they are fine if they do.


 
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