We have a bicycle with a Crystalyte hub motor and a Crystalyte CT3640 controller. It works fine with NiMH batteries, so we got some Dewalt DC9360 "36 volt" batteries, charged them up with a Dewalt charger, and tried them out. As soon as the controller was turned on, the battery went dead. The charger also indicates that it is a dead battery, and won't charge it again. Thought it might be just the particular battery, so tried another. Same thing. Tried the NiMH pack again--everything works fine.
So, it works okay with the NiMH batteries, but it kills a DC9360 battery as soon as it is turned on. The clamp-on ammeter says it draws a tenth of an amp or so at that point, when the switch is turned on, no throttle.
Any ideas?? Any help, suggestions, or ideas will be greatly appreciated!
Jim, in Western Wisconsin
Sounds like you might have blown the BMS. Did you open the pack and measure the cell voltage before and after the BMS?
Measuring the cell voltage will give you a better idea of what is happening.
Any ideas why just connecting the battery would blow the BMS? Anyone else have this problem?
I hear the bms is only good for 15 amps, you need to bypass the bms on discharge.
But--the battery went dead just hooking it up and turning on the controller, not even trying to run it. The good friend who encouraged us to try the Dewalt batteries is running his hub motor on a trike with no modifications, straight connected to his Crystalyte controller, with no problems at all.
Whats the pack voltage? Does sound like a dead bms/loose connection. I guess its either open it up and fix it or send it back. There's a quite a few threads here's on these packs now, might be worth a read. let us know if you get stuck
Pack voltage is 33 volts, so the BMS may be dead--but my question is, what would wipe out the BMS just by connecting the battery to the controller, and turning on the controller (measured current 0.2 amps or less)--didn't run the motor at all.??
Thanks!! (and I did search for other threads discussing the DC9360 battery, but so far didn't find anything that was helpful)
The fuse is probably blown. Your friend may have pedaled first and then engaged the motor, thus not blowing his... If you are not into opening the pack, take the battery back to DeWalt. They will probably replace it since it is not opened. If you want to open it up, you can test the problem and make the charging work again (ie. turn off the bad batt indication). To do this, the black wire must be jumpered to the negative contact of the BMS. This will charge and balance the pack. From now on you could get your 33 volts from the red and black wires of the pack by soldering in. I have blown some BMS's were this will not work. You can also do the fuse bypass (search forum for this). Hope this helps.
Jeff K. "Bike to the Future"
I am not sure if I made point that the motor was not operated at all--the battery was connected and the controller turned on, max current 0.2 amps or less--no throttle, no motor running, just connected the battery to the circuit and POOF! it died. Due to disbelief, we tried it with a 2nd battery and Poof! same result. Everything works fine with NiMH battery, before and after.
Jim, Which connectors did you connect to on the pack? How did you make the connection? Maybe, internally, you hit the middle connector which is a BMS used connector. Did you charge the pack and see all three LEDs on before this problem? If the battery pack is drained below about 28 volts. the bad batt flashing will be on and tyhe charger will refuse to charge it (which is kind of stupid).
Jeff K. "Bike to the Future"
We made a wiring harness that had tabs to connect to the outside (+) and (-) terminals only. The pack was fully charge minutes before using it, and the charger indicated full charge. The cells themselves read 33 volts after the failure when we opened up the battery case.
Thanks for the response to my questions.
Yeah, that stinks. Looks like BMS barfed... Infant mortality.
So, what kills the BMS???? I didn't short any other connectors, battery was fully charged before, everything works with the NiMH battery before and after using the Dewalt batteries.
What kills the BMS just by turning on the controller on the bike?
As I've mentioned on another thread here I've been playing with a Crystalyte 408 motor, 36v-48v/20amp controller and ebikes.ca CycleAnalyst controller/meter with Dewalt 36-volt batteries for a couple weeks now. I've had a number of instances in my experimentation when the Dewalt charger has rejected a battery as bad. Each time I've resurrected the battery by taking it apart and manually charging the lowest cell with a couple of AA rechargeables. The batteries seem to be settling down and staying more balanced over time.
In my experience, single cell voltage balance is more important than overall pack voltage. I've had the charger work without complaint with a battery reading 17.5 volts.
I regularly draw 20+amps and haven't blown a battery fuse yet. Seems easy enough to bypass though. Can't imagine why a Dewalt battery showing 33 volts wouldn't work where an NIMH would. Did you try a single Dewalt by itself? What is the cutoff voltage on your controller?
I'm amazed at the power I get out of just two batteries in series. Climbs very steep hills with just a little help on the pedals.
I just scanned through this thread again. All these references to killing the BMS ...
If you're connecting Dewalt batteries to some other device (like a Crystalyte motor) you shouldn't be using the BMS, except for charging.
The internal fuse is separate from the BMS circuitry and is easily bypassable. If you have voltage between the two outer spade-lug connectors then your fuse is fine. You probably shouldn't be touching anything on the battery's external connector besides those two outer contacts.
Sounds like you are using the unswitched negative terminal on the pack. This bypasses the BMS during discharge. The Crystalyte controller has a capacitor which appears as a large initial load when the pack is connected or turned on. This can blow a fuse or cause the BMS to open. My solution was to add a small inductance in series with the controller. This inductor does not waste much power in actual use, since it never seems to warm up. Inductor was ten turns of #14 wire around a ferrite toroid Mcmaster-Carr #8495K57. For pack pinout and other details, please see my other post regarding Dewalt Hack, or the link below:
Best of Luck in your endeavor!
I agree with the Cyclemotor Engineer's comment about the unswitched terminal. The spark of the controller is substantial. Even if not, the BMS "brain" may get a spike and die. When I first got a pack, I hooked up to the two outer lugs and used the battery. It blew. I was somewhat upset but realized my overloading it. I decided then I would connect the wires below the BMS directly. But the bad battery indicator was still blinking. I found that by simply connecting a jumper wire (looped around lug on charger, under battery) to the metal case of the BMS, it completed the circuit and charged again. That is one option for you. By bypassing the BMS for output, you gain more amps. Now I soon learned the next problem. Since part of the BMS is for charging/discharging/balancing the cells, there is another part that cuts output power when the pack is getting low. If you go too low, you can destroy cells or loose capacity (AH).
So if you do the bypass, just make sure you don't go too low.
Jeff K. "Bike to the Future"
Thanks for the info. We will try the inductance and see if that helps. There are 2 things that bothered us--First, it is strictly the controller being turned on, no load to the motor (load is less than 2 amps max surge, which I mistakenly wrote as 0.2 amps above), that is damaging the batteries or the BMS. Second, a friend is using the same kind of motor and same batteries on 2 recumbents with good luck, and we are hooking things up the same as he did, using just the outer 2 terminals.
By the way, if you are interested, here is our friend's site with info on his bikes:
Thanks for the interest in our problem. I'll keep asking and posting if we continue having questions, and let the group know how things work, if we overcome our glitches.
It appears that your friend is using four packs in parallel, so the load is divided amongst the four fuses in the packs. Also, he may have more resistance in the leads and connectors between the controller and batteries.
Even if you get one pack going with the inductor, you may have problems driving a the motor at high power without blowing the fuse. You may want to try several in parallel. Parallel Schottky diodes on the outputs can prevent a weaker pack from discharging a stronger one. International Rectifier part # 40CPQ100, available from Digi-Key.
I believe that using the unswitched terminal can result in a decrease of battery cycle life. Using the BMS during discharge will prevent overdischarge and reverse-bias of a weak cell.
Why are you fooling around with breaking apart a power tool battery in the first place ?
Sounds like a lot of trouble.
If you want a Lithium battery, just buy one...?
The LiFepo4 BattMan www.falconev.com
While I cannot speak for the others, my interest stems from the amazing cycle life of the DC9360. 2000 cycles, with discharge at up to 350W/pack, and 1 hour recharge. This will mean 30,000 miles between battery replacements. DeWalt is behind the transferable specs, with their solid reputation in the power tool industry. A sophisticated BMS is built in (which monitors individual cells) so the hard part is done if one uses the hack described in my recent thread.
...And by purchasing the DeWalt packs using lowest-price E-bay opportunity, you will get a great power source at a reasonable cost. It is amazing to see the power one pack can achieve. On two packs I rode a 150+ lb. motorcycle to 20+ MPH uphill!
Jeff K. Burbank, CA
"Bike to the Future"
A couple of comments to clarify things:
First (in reply to Proton) we aren't aking apart or modifying the batteries in any way--just using them to power something other than a power tool by Dewalt.
Second, when we rode my friend's trike with the Chrystalyte motor, shown on his website with 4 Dewalt batteries, it was set up with a different battery holder, and we rode it with only one battery.
Still no reason that I can find for our battery BMS to go flooey on us.
Upon reflection, I am not absolutely certain that the BMS speed control is pulse modulated. I assumed that it was voltage proportional, since the drill motor only had two leads. Motors can be PWM controlled without hall effect sensors. In any case, the brushless Crystalyte motors require hall effect sensors to tell when the pulses are to transition. This capability is not built into the BMS speed control. I did not open the battery up, but contents of the black box were revealed by ruddman430 on this thread: http://www.rcgroups.com/forums/showthread.php?t=587041&highlight=a123+dewalt+circuit+fuse
Output is switched by a FET, which is not apparently part of speed control. A 15 Amp fuse is in series with the unswitched negative lead. I suspect that this fuse is being blown often. Thin power leads, small connectors, or a low power motor may limit discharge current to less than 15 Amps.