Here is a simple way to use multiple Dewalt nanophosphate packs with the existing BMS and chargers.
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I can't seem to find those Schottky diodes anywhere. What's a good replacement?
Thanks
I don't know if this is the exact part:
SCHOTTKY-BARRIER-RECTIFER
I bought some, but I haven't tried them out yet...
Matt20
If this link isn't working:
the part (I haven't used this yet):
RCA 10053-009 CF SCHOTTKY BARRIER RECTIFER 40A 500V
at:
http://stores.ebay.com/Electronics-EZ-Find
Matt20
Wow, 500volts and $40 seems like overkill.
Mouser has some 250volt (still overkill) units for around $2.
Can't find specs on the RCA part. Is it's voltage drop number really impressive or something?
Richard
Digi-Key has the Schottkys.
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=40CPQ100PBF-ND
Best of Luck in your endeavor!
Cyclemotor Engineer
http://www.neodymics.com
Cyclemotor Engineer
http://www.neodymics.com
Thanks.
What exactly does the magic resistor network do on the undocumented Dewalt battery terminals? And which battery power terminals are you connecting to your switching circuit?
The Dewalt system deals with the A123 cells quite conservatively -- appropriate for hand tools but seemingly less so for powered vehicles. Doesn't it make sense to use the BMS for charging and ignore it otherwise?
Thanks
Richard
Hi Richard,
Resistor network looks like a Dewalt drill with the trigger pulled in fully. It tells the pack to supply as much current as allowed. Battery terminal labeled positive output in Fig 1 is labeled + in Fig 2. Battery terminal labeled negative output in Fig 1 is labeled - in Fig 2.
With four packs, I can get 1.4 kW out, and that is plenty for my ride. I wanted to use the BMS during discharge to prevent damage to cells from overdischarge. A weak cell will be reverse biased at some point if pack is discharged deeply enough. Even the A123 cells are damaged by this condition, as evidenced by reports of others. The BMS monitors each cell voltage, and would be relatively difficult to replicate.
Cyclemotor Engineer
http://www.neodymics.com
Cyclemotor Engineer
http://www.neodymics.com
Thanks, CE!
The explanation, schematic and BMS information are most appreciated.
Instead of the additional high power switching, wouldn't it be reasonable to have the BMS turn things on? Since you're already using it?
Rather than hardwiring the BMS 'speed' to full, use it as the power switch between the batteries and external motor controller.
Any idea how to adjust the resistor network to set the requested `speed' to zero?
Any other interesting insights into the functionality of the Dewalt BMS?
Thanks!
Richard
p.s. You sacrificed four whole $60+ Dewalt floodlights just for connectors?
Hi Richard,
Each pack requires its own resistor network for the internal BMS speed control. The speed control of the hub motor is pulse width modulated, unlike the BMS speed control. I did not look into using the BMS speed control directly, since it would be redundant in this application.
Paid $35 on eBay for the flashlights. A bandsaw was used to slice the holder section. This was simple and quick and cheap compared to building four connector assemblies from scratch. New, specialized connectors are relatively expensive.
Best Regards,
Cyclemotor Engineer
http://www.neodymics.com
Cyclemotor Engineer
http://www.neodymics.com
CE's post contains an important revelation about the Dewalt batteries. Use of the on-board electronics for a safe end-of-discharge shutoff signal.
http://visforvoltage.org/comment/reply/1699
http://www.neodymics.com/Images/V24ProtoSwitch070818E.pdf
The circuit uses the controlled (MOSFET) output from the battery as the source of safe power. It mimics a tool set to full speed to force the output to be always on -- until the first internal cell drops below Dewalt's preset cutoff voltage. Then the battery's circuitry shuts off power signaling a recharge is required.
This appears to be the answer to getting lots of cycles out of these batteries safely.
The A123 cells within the Dewalt batteries are no-doubt capable of much greater output (70amps continuous) than the Dewalt circuitry will withstand. It seems reasonable that this scheme could be used as a shut off signal for a more capable controller drawing power directly from the cells -- thus not overloading the Dewalt circuitry.
I haven't tested any of this myself, but hope to soon.
Many thanks to CE and all the other folks for figuring out how these batteries work.
If anyone has reverse-engineered the charger I'm sure many would like to hear about it. Several have succeeded in charging multiple packs simultaneously, at slower rates. It would be nice if the output current could be increased somewhat.
The charger's use of the battery's `other' contacts is also of interest. Especially to those wanting to tie batteries and charger(s) into a more permanent package.
Next we'll be tying the charger into the amp-hour meter -- so even with a partial charge we'll know how far we can go.
Richard
Hey Everyone,
Can I charge multiple DC9360 with one charger? Can't we just parallel multiple batteries to one charger? I don't mind if it takes longer. I've read that several have succeeded in doing so. Who are those people and where can I get some more info.? I tried Google and it came up with nothing. BTW, thanks to the CE guy for that kool hack.
moonfresh
Can I charge multiple DC9360 with one charger?
Yes you can and I have.
Can't we just parallel multiple batteries to one charger?
You will have to parallel all the cells using the bms module outputs and the main +/- lines and run them through one BMS control modules.
I have done 5 in parallel. You can probably put as many as you want in parallel... Put N in parallel and it takes N times longer to charge.
Who are those people and where can I get some more info.?
See the following links at this very forum:
http://visforvoltage.org/forum-topic/batteries-and-chargers/578-a123-developer-packs
http://visforvoltage.org/forum/batteries-and-chargers/1444
Brian
Hello,
This is what I want to do:
1. I want to be able to turn a switch on and have 6 DC9360 connect in series to obtain 216 volts.
2. I want to be able to turn the switch off and have the batteries disconnect so I can parallel charge the 6 DC9360 with 1 charger.
First off, do you think it is possible? If I parallel all the cells using the BMS module outputs and the main +/- lines and run them through one BMS control modules, as stated by mn_aerorider1, would I not have a problem when the batteries are in series, ready for discharge? Thanks everyone and have a Happy Thanksgiving!
moonfresh
Hi Moonfresh,
You are correct - if you wish to charge all of the packs using one charger, you will need to put the BMS lines all in parallel, otherwise you won't be able to balance the packs.
Then when you switch them to series, you'll need to disconnect all the parallel BMS lines and power and ground lines, and then reconnect the power and ground lines in series.
This will not be easy, and could be done using either large banks of relays or FETS, or hand-connected connector plugs to make this switch from parallel to series.
Brian