That would be difficult. that cahrger pulse the current to the batt and the circuitboard is not built to hold more current than 3A. You can cahrge many pack with one and having only one of the pack with the BMS, but the time to cahrge them will be proportional to the number of pack.rf wrote:Has anyone looked into cranking up the current on the Dewalt charger to charge a couple packs simultaneously at a faster rate?
Yep, that obviously works, so adding the diodes is probably a good thing. I'm just curious if it is really necessary.OneEye wrote:The neodymics schematic is a good jumping off point for a serial/parallel 72V system. You should be able to add more parallel branches based with the same basic philosophy.
The resistor network is the more important part in my opinion. It allows you to use the BMS to shut off battery output when voltage of any cell drops below minimum -- thus keeping the battery from damaging itself.GGoodrum wrote:Yep, that obviously works, so adding the diodes is probably a good thing. I'm just curious if it is really necessary.OneEye wrote:The neodymics schematic is a good jumping off point for a serial/parallel 72V system. You should be able to add more parallel branches based with the same basic philosophy.
GGoodrum wrote:Okay, this helps, thanks. I'll try the 5k resistor/10k pot idea first. Hopefully I can come up with a couple of readily available fixed values that work.
I'm also going to skip the schottky diode isolators for now as well. With the protection the BMS provides, even if one series pair ends up with a bad cell the worst that will happen is that the other series pair(s) will have to work a little harder, and will discharge faster.
GGoodrum wrote:I have another question. I assume you can use two BMS-enabled packs in series, as each LVC function in each BMS will work independently to protect each pack. What about if these series connected BMS-enabled DeWalt pairs are paralleled, in 2p, and/or 4p configurations? Would it matter? If it is a problem, would using the Schottky diode isolators help?
Normally, when you parallel two packs, the voltage ends up being the average of the two. I always assumed this would be roughly analogous to having the level of water in two containers equalizing, if they are connected. To make that happen, some water has to flow from the higher level container to the lower level one. I would think the same sort of thing happens with two paralleled batteries. Is this the case, what happens if you parallel two BMS-enabled DeWalt packs? I guess another way of asking the question, can you recharge the cells through the switched connections? I would think not, but what happens if you try?
OneEye wrote:Turns out not to be a parallel charging setup as I had originally thought, so sorry this wound up in the wrong thread. Hopefully it proves useful all the same.
Running through the BMS, the neodymics setup isn't drawing more than about 12A from the pack at any time (2s2p), and I don't know if they confirmed the BMS will provide a cutout for a pack at low voltage or a cell that is below the recommended cutoff voltage. If it does that would be great.
Essentially this could be a warranty-proof way to use the packs. You are not discharging them more than spec, and are interfacing with them the same way a power tool does.
GGoodrum wrote:Old posts, old info. A lot of us are a lot smarter now. Trying to use the DeWalt packs as is, along with the internal crap BMS module, will not yield a very satisfying experience, in my opinion. Feel free to prove me wrong.