Jeremy Harris
100 MW
I'm putting together a small LiPo pack for a non-technically minded person, so was looking for a plug-in-and-go charging solution, one that didn't involve pressing buttons or looking at displays. The pack is a modest 7S one, and there isn't a need for fast charging, 10 to 12 hours would be fine, as it could be charged overnight. As others have found, there isn't an easy solution to this particular conundrum. Add in that I didn't want to spend more than the equivalent of around $50 on it, or weeks of time building something that was custom made, and the problem gets even harder.
HK sell these little balance chargers: http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=7637 that will deliver around 0.8A, need no button pressing or whatever and which are dirt cheap at $4.49 each. They only charge up to 3S though and still need a 12V power supply.
A quick hunt around on ebay found some small 12V 1A isolated power supplies from this ebay seller: http://myworld.ebay.co.uk/bestvaluezone/ for just under $7 each, including shipping.
The plan is to fit three power supplies and three of the small chargers (minus their cases) in a small box, with an 8 way cable and connector that plugs in to the battery pack to charge the individual cells via the balance taps. The chargers will be hooked up with their top outputs in series, which should work fine with the isolated inputs. The charge current is nice and low , so the balance leads will take it just fine, and the chargers have a couple of LEDs on that I can extend out to the case. Charging should be as simple as plug it in, switch on the power and wait for the "charged" indication on all three LEDs. Pretty foolproof.
With three supplies and three chargers this unit will charge from 1S to 9S. Add more and you can build as big a balance charger as you need. The only things to watch is that the outputs are kept in the right sequence and that the charger outputs are kept isolated. This latter point needs checking carefully, as the negative output track can *just* touch the case clip - easily fixed by adding a sliver of tape and a little bit of bending of the case tab.
I'll post pictures of the finished unit, but here is a shot of one of these tiny power supplies and a charger:
One thing that may be of interest is that these power supplies have a rated input voltage range of 86V to 230V +/-20%. They may well work OK on a DC input from as low as 70V or so. Might be handy for anyone looking for a cheap 1A, 12V DC DC converter. I'm reasonably sure one of these would make a 12V supply for the "simple BLDC controller" for anyone running at 70V or more.
Jeremy
HK sell these little balance chargers: http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=7637 that will deliver around 0.8A, need no button pressing or whatever and which are dirt cheap at $4.49 each. They only charge up to 3S though and still need a 12V power supply.
A quick hunt around on ebay found some small 12V 1A isolated power supplies from this ebay seller: http://myworld.ebay.co.uk/bestvaluezone/ for just under $7 each, including shipping.
The plan is to fit three power supplies and three of the small chargers (minus their cases) in a small box, with an 8 way cable and connector that plugs in to the battery pack to charge the individual cells via the balance taps. The chargers will be hooked up with their top outputs in series, which should work fine with the isolated inputs. The charge current is nice and low , so the balance leads will take it just fine, and the chargers have a couple of LEDs on that I can extend out to the case. Charging should be as simple as plug it in, switch on the power and wait for the "charged" indication on all three LEDs. Pretty foolproof.
With three supplies and three chargers this unit will charge from 1S to 9S. Add more and you can build as big a balance charger as you need. The only things to watch is that the outputs are kept in the right sequence and that the charger outputs are kept isolated. This latter point needs checking carefully, as the negative output track can *just* touch the case clip - easily fixed by adding a sliver of tape and a little bit of bending of the case tab.
I'll post pictures of the finished unit, but here is a shot of one of these tiny power supplies and a charger:
One thing that may be of interest is that these power supplies have a rated input voltage range of 86V to 230V +/-20%. They may well work OK on a DC input from as low as 70V or so. Might be handy for anyone looking for a cheap 1A, 12V DC DC converter. I'm reasonably sure one of these would make a 12V supply for the "simple BLDC controller" for anyone running at 70V or more.
Jeremy
