Dewalt A123 BMS battery interface solution

[kfong]

Yes, I have plenty. I just did a new run, since they have been popular. The pricing is found on the first page of this thread. Just PM, or email me at kinf@embeddedtronics.com

Hi, do you have any interfaces available, and if so, how much are you charging for them. Please feel free to PM me. Many thanks indeed.

[Mike B]

Kfong, great solution! Looked at this thread a few times.

Question, will the interface allow regenerative charging? Lots of hill here, up and down. The 4011 motor on a previous bike would hit 20 amps of regen going downhill (had two Watts Up meters wired head to head to read this once I figured out why the one meter's voltage was going high on downhills). But your board has a diode. So I think not....

[kfong]

Your right the diode would prevent it. I think the BMS might have problems with it as well. Not much info on the Dewalt circuitry to know. The amount you get back from what I've read isn't enough to be very practical. It does seem to make a good electric brake, something I want to try on my 10x6 motor I've acquired recently.

Kfong, great solution! Looked at this thread a few times.

Question, will the interface allow regenerative charging? Lots of hill here, up and down. The 4011 motor on a previous bike would hit 20 amps of regen going downhill (had two Watts Up meters wired head to head to read this once I figured out why the one meter's voltage was going high on downhills). But your board has a diode. So I think not....

[eBikeStore]

Hello,

There may already be a thread on this, but I haven't been able to find it.

Does anyone know a safe testing process to determine the health of a dewalt battery? I am looking for a process that would not involve using kfong's adapter (to start). I am trying to determine if my batteries have enough life in them to make buying kfong's adapter worthwhile.

Thanks!

Wake

[kfong]

If you keep it under 15 amps and have an RC charger that can cycle your batteries like the 1010B, you can test the capacity. Most RC chargers don't have much of a current load so the 15 amps isn't really much of an issue. You will be able to just tap into the two outer terminals.

[jag]

Update, looking for a suitable inductor. The one I found, I wasn't happy with the wire gauge, so I looked around and found a ferrite toroid, and started wrapping wire around it. I ran out of wire, but felt it would be good enough for the test. Worked better than I expected. It just goes in between the battery and the speed controller. No bms shutting down from the capacitive discharge coming back from the controller.

Like some other people in this thread I had problems that the DeWalt BMS would cut when connecting to my controller. The current peak to charge the controller input caps was too high. I started winding an inductor (had bought the toroid from Kin just in case). Then it occurred to me why not use an NTC resistor as inrush current limiter of the type used on many switched power supplies. I had used these on the input side of my own controller project (http://endless-sphere.com/forums/viewtopic.php?f=7&t=19993&start=15#p292906) just for this purpose (They are the two black discs in the bottom left corner of the PCB from the previous link), but commercial controller manufacturers seem to not be so careful.

Here how it looks on a kfong board. Note the much smaller footprint of the NTC resistor compared to the inductor.

DSCF9555_sm.jpg (82.05 KiB) Viewed 885 times

The NTC I used is rated for 15A. Gets warm (as it is supposed to do) running near the rated current. Tried it both with the controller from the cellman 350W geared kit and a crystallyte 20A. Works great to prevent startup BMS tripping (and sparks on connecting the wires) for both.

I was looking to try this on some higher amp controllers, but had a hard time finding a suitable part number on digikey. Instead I was thinking of using higher ohm, but low current NTC for startup only, like this one:
http://parts.digikey.com/1/parts/1521264-cur-limiter-inrush-50-ohm-1-6a-sl10-50002.html
Then when caps are charged just short the NTC out of the circuit. I'm curious if you think this would work on the Castle HV160? The HV160 does some "motor twiddles" on bootup that are probably pretty high current. Can those be turned off in the programming somewhere? Or the NTC has to survive that?

Question, will the interface allow regenerative charging? Lots of hill here, up and down. The 4011 motor on a previous bike would hit 20 amps of regen going downhill (had two Watts Up meters wired head to head to read this once I figured out why the one meter's voltage was going high on downhills). But your board has a diode. So I think not....

I run w/o the diode. I haven't purposively used regen, but my 9C often puts 100-200W backwards when backing off the throttle, and the DeWalts seem to survive that.

Another "feature" (not sure if accidental or not) is that on a 2s pack, when the BMS triggers at the end of capacity of one it seems to allow current though, so I can keep riding on half the voltage on the remaining pack without any reconfiguration. B.t.w. I get about 2Ah of the rated 2.3Ah from my 2007 toolking 24V packs.

[kfong]

Jag that looks like a nice solution, but the current output from the FET driver is usually 20-25amps. Need to find one with a higher rating to make full use of the current. I've never used these, but isn't the resistance a little high? The 25 amp version has a 5 ohm value at 25'C. I think the Toroid still works out to be better.

The diode is to protect batteries with different capacities. If you plugged a fully charged pack and left an empty pack plugged in as well. You end up with one pack tying to fast charge the other. Not a good situation. If you keep the packs together all the time, then the diode can be omitted.

[jag]

Jag that looks like a nice solution, but the current output from the FET driver is usually 20-25amps. Need to find one with a higher rating to make full use of the current. I've never used these, but isn't the resistance a little high? The 25 amp version has a 5 ohm value at 25'C. I think the Toroid still works out to be better.

You mean for instance this 25A one:
http://www.digikey.com/es/en/products/M ... -ND/749869

Before connecting the controller it is 5Ohm. This helps limit the inrush current when connecting the battery to the controller.

The point is that when connected and in use it will heat up from the current in just milliseconds. Since it is an NTC the resistance goes down when temp increases. At full current, 25A, the resistance is only 0.03 Ohm, so it adds negligible resistance compared to the DeWalt pack itself.

[kfong]

Yep that's the one. I'll have to give it a try. Neat solution.

[CyclemotorEngineer]

Kfong et. al.,

Nice work with the hack circuit. My circa 2006 packs are still going strong, after over 1000 charge cycles. I've attempted to start a discussion of what to do about the change to our beloved DC9360 packs. (They no longer contain A123 or equivalent cells!!) Title was Open-source alternative to DeWalt DC9360 since Stanley shaft. I would think this to be of interest to all who built this hack. Details repeated below:

Short, semi-chronological background to the shaft: A123 develops the best all-around battery, which is cycle-life-cost-competitive with lead-acid, and has best power density along with very good energy density. DeWalt incorporates these into their DC9360 packs. This poster designs simple hack to unleash the DC9360 for alternative uses. Kfong expertly develops and sells hardware to implement this hack. Stanley buys B&D/DeWalt. Short-sighted Stanley surreptitiously substitutes Samsung cells for A123. Hackers and more legitimate customers lose out.
http://www.youtube.com/watch?v=ZqPX46RX3gY

Meanwhile, A123 develops 7Ahr 32157 cells more appropriate for e-bike use. Also, back at Endless-Sphere, open-source BMS and chargers are developed.
http://www.a123rc.com/goods-474-LiFePO4 ... 57%29.html

I haven't scoured the hundreds of pages on this forum for details about the open source electronics, but am wondering: Has there been a discussion of developing charging and discharging hardware specifically for the 7Ahr 32157 A123 cells, in 10 to 20 cell series packs? Could this hardware be made available to all of us as SEEED project?
http://www.seeedstudio.com/propagate/

(moderator edit: fixed your second link; it didn't copy/paste from your other post correctly due to phpbb shortening displayed text of long links)

[PeteCress]

My circa 2006 packs are still going strong, after over 1000 charge cycles.

How many Ah do you get out of a pack now?

I'm down to about 2 from 2.2 - but more like 100 than 1,000 charge cycles - and wondering if that is normal wear-and-tear.

[CyclemotorEngineer]

I'm getting about 15% less capacity on the 2s2p DC9360 setup. Probably being shut down by the worst pack, and I haven't bothered to test individually on a dummy load.

How old are your packs? There is a stamped date code next to the recycle tag which is six numbers corresponding to a year and week. Mine are all between 200618 and 200637.

Also, as kfong noted, it is important to pull packs from discharge circuit when not in use.

[PeteCress]

How old are your packs? There is a stamped date code next to the recycle tag which is six numbers corresponding to a year and week. Mine are all between 200618 and 200637.

I only have 2 packs and they are stamped "2009 09-U0" and "2009 12-U0".

[CyclemotorEngineer]

Pete,

It may be that your packs have degraded with age. I don't recall seeing specs for shelf life. Some chemistries, like NiMH, are not tolerant of disuse. It may not matter for A123s, but just to be conservative, I try to cycle mine at least once a month in winter.

So, pertinent questions include: Are you charging/discharging regularly? Did you buy these new? Are you keeping them out of the discharge circuit when not in use?

[biohazardman]

I'm getting about 15% less capacity on the 2s2p DC9360 setup. Probably being shut down by the worst pack, and I haven't bothered to test individually on a dummy load.

How old are your packs? There is a stamped date code next to the recycle tag which is six numbers corresponding to a year and week. Mine are all between 200618 and 200637.

Also, as kfong noted, it is important to pull packs from discharge circuit when not in use.

It is known that the DeWalt packs with their BMS and charging suffer with some problems when used together. They do not charge evenly and over time some cells become weak and eventually the pack will not charge at all. It would be good if you could test the cells individually. I have purchased such packs and after removing a faulty cell or two, always the same cells, all other cells were healthy and are still serving me well two plus years later. Although I have not checked the tag you speak of I have a bag of the cases and did not to mark the info on my packs. Thanks for the thought that even these my favorite cells will eventually die it brings much remorse to my otherwise miserable existence.

[PeteCress]

Some chemistries, like NiMH, are not tolerant of disuse. It may not matter for A123s, but just to be conservative, I try to cycle mine at least once a month in winter.

That sounds like a promising explaination. My use is even more abusive: I only use them during winter months and they have been sitting untouched for probably 9 months of every year.

At the end of this winter, maybe I will leave the boards attached, see how long it takes them to bleed down to about 1/4 charge and - if the time is long enough, maybe use that as my recycle means. Just put a repeating entry in my calendar to charge them up every interval.

[kfong]

It would be good to know the current drain of the internal Dewalt BMS. I would not trust my cyclone controller with the Dewalts for more than a week or two. So don't forget to account for the drain from the controller.

I notice they become unbalanced from being used with high current loads. They seem fine when not pushed as hard. A minimum of 3 packs is best for longer life. Even though the cells have a high C rate. The battery build and internal wiring is poor, creating heat on the wire and weld tabs. They use a wimpy wire gauge. The whole setup is meant for 20amps or less. When used this way, they should last a very long time. My packs using the Dewalt chargers are still going strong. I'm sure they have lost some capacity, but I don't think the loss is linear over time, so I expect them to be useful for many years.

[PeteCress]

It would be good to know the current drain of the internal Dewalt BMS. I would not trust my cyclone controller with the Dewalts for more than a week or two. So don't forget to account for the drain from the controller.

I notice they become unbalanced from being used with high current loads.

Well, there's another promising explaination. For awhile, I was using just one battery at a time. Eventually I read somebody's comment and changed over to always using 2.

RE/"Cyclone controller": Is that to say that you are running your Dewalt cells outside of DeWalt's BMS- as BioHazardMan seems tb doing?

[therm_batt]

I have a Yamaha PAS pedalec.
It had NiMH batttery, I replaced when it died with homemade Li-ion usning recycled laptops and batt controller. These old cells have very high internal resistant so voltage drops below 22 V (from 29V fully charged) and BMS trips out.
Want to build new battery.
One poster stated 7 Amp-hr 32113 A123 LiPo cells are acailble for about $20/ea AND that Dewalt 9360 no longer use A123s.
If these A123 cells are real, why buy dewalt back now ?

[kfong]

The form factor still make them useful. The flat packs can be a bit cumbersome to use. If you can still get them, the cycle life is a lot better than lipo's. I'm hanging on to mine for various projects not always ebike related. Still my favorite tool battery.

[csm]

The interace boards have a protection diode so you can easily parallel packs, even if they have different voltages.

What happens when one of the batteries is low. Do you just have less capacity. Or do you notice by how the bike performs?

Seems like the 36v lithium packs are being phased out by most cordless power tool companies. I have notiec that 18-20 volt lithium packs are becoming a standard in cordless tools. Costco sells a cordless craftsman drill that comes with 2 20volt lithium batteries, for about $129 on sale right now (normally $199 for the kit http://www.costco.com/Browse/Product.as ... d=11682299 ). I don't know how many amp hours or watt hours are in each pack or what chemistry the packs are using. They seem to have 4 screws with a star type hex pattern on thier heads. Seems like it would take a long neck, thin, tool to get the screws unscrewed, and remove the cover and see what is inside. I am guess there are probably 6 - 3.2v cells?? (amp hours??). I suppose they have a BMS in them and probably could string 2 together in series for 40 volts and then string another 2 in parallell for more capacity? I can not see these packs being sold at Sears.. not sure if these packs will continue to be made. They are square in shape, similar to the 36v DeWalt battery packs. I am gessing, by weight, they may be 4 amp hour cells??

[kfong]

You just get less capacity, the discharge curve is very flat. You will only notice it if only 2 or less packs are doing the bulk of the work or are drawing more current than the 20-25amp limit of each pack.

Unfortunately, A123 is having financial problems and I suspect these batteries will be hard to find soon. Already reports of Dewalt substituting other cell chemistry in its place that are not as good.

The interace boards have a protection diode so you can easily parallel packs, even if they have different voltages.

What happens when one of the batteries is low. Do you just have less capacity. Or do you notice by how the bike performs?

Seems like the 36v lithium packs are being phased out by most cordless power tool companies. I have notiec that 18-20 volt lithium packs are becoming a standard in cordless tools. Costco sells a cordless craftsman drill that comes with 2 20volt lithium batteries, for about $129 on sale right now (normally $199 for the kit http://www.costco.com/Browse/Product.as ... d=11682299 ). I don't know how many amp hours or watt hours are in each pack or what chemistry the packs are using. They seem to have 4 screws with a star type hex pattern on thier heads. Seems like it would take a long neck, thin, tool to get the screws unscrewed, and remove the cover and see what is inside. I am guess there are probably 6 - 3.2v cells?? (amp hours??). I suppose they have a BMS in them and probably could string 2 together in series for 40 volts and then string another 2 in parallell for more capacity? I can not see these packs being sold at Sears.. not sure if these packs will continue to be made. They are square in shape, similar to the 36v DeWalt battery packs. I am gessing, by weight, they may be 4 amp hour cells??