a123 developer packs

you can buy them here http://www.a123racing.com/

there's more info on their forum aswell

masonsteele,

15 cells at 3.3v nominal will get you there. Check http://www.a123systems.com/html/products/buyKit.html

Depending on the discharge rate, the voltage might sag too low however, and you might want to add an additional cell or two provided the voltage isn't too high for the controller after charge.

---
Avatar taken from http://www.electricmotorbike.org/
Anyone got one they might want to sell?

Get the DeWalt packs on eBay. They are cheaper.

got website where you can read up the specs on the DeWalt??

I have a couple dewalt packs.

They are built out of 10 a123systems cells. They're (if I remember right) put together with tabs spot welded to the cells to form the pack. The unit includes a BMS which handles charge and discharge. The BMS has wired connections to the postive-most and negative-most terminal, as well as to each cell individually.

For my bicycle (a WE 36 brushed system) what I did was open the pack and wire leads to the postive-most and negative-most terminals that then go to a standard sort of connector. When riding the bike I have two of these packs in parallel discharging through those leads and not discharging through the BMS.

To charge the packs I disconnect the leads and charge each one in a normal dewalt charger.

The when fully charged, the voltage of the dewalt pack is 36v. This makes the nominal voltage of the pack to be around 33 volts. That means dewalt is misadvertising the pack voltage. So far as I can tell each pack holds about 2.5 AH.

- David Heron, http://davidherron.com/

A great information site for a123: http://hybrids-plus.com/pmwiki/index.php?n=Ext.A123Cells

I have been using 4 A123 pack in parallel for about 8 months now and absolutely love them. They have great current handling and no capacity drop off under high current conditions. I am running around 135 amps peaks and have seen no capacity degration yet either.

Hi David,

I have 4 packs and 4 chargers and had planned to use the batteries in the chargers in situ -- wiring the charger terminals in parallel using diodes to protect the BMS -- but it makes more sense to bypass the BMS entirely.

Do you have any pictures of your connections?

P.S. Yes, the packs are 10 X 3.3V cells, so you're right, they are 33V (and they are advertised at 2.2aH). Given the level of safety, however, plus the 1 hour recharge time and the thousands of recharge cycles -- I can live with a few less volts.

Cheers,

Burners

Burners,

I orginally posted this on the visforvoltage.com page but I feel it important enough to what you want to do. I too currently am running 4 dewalt batteries with 2 stock chargers. Here is a little write up them:

I finally did it: I spent 200 dollars and got 2 Dewalt 36 volt batteries and a charger. I received my package on Friday and have started to make the packs work for my application. I am hoping to eventually buy two more Dewalt batteries to have total of around 8.5 ah of capacity at 33 volts. The packs weighs 2.5 pounds according to a postal scale so my 8.5 ah pack is going to be 10 lbs and will definitely out range my current 21 lbs 10 ah lead acid pack. If you were to pull out the BMS and case with all the balancing probes you probably could shed off a half pound maybe more.

I decided to go ahead and use the stock charger so that I can get the benefit of cell balancing hopefully keep the life of the batteries nice and long. Plus it a pretty fast charger bringing a battery to full in 1 hour (as tested). When I buy the two more batteries I going to get a second charger so I can refill my whole pack in 2 hours. The picture below is the charger and then :

So I am going to parallel all my packs so I had to by pass the BMS for my output to my scooter. All I did was solder directly to the two output tabs of the cells and left the BMS in. You can see below my okay solder job, but it doesn't warm up at all even at 15 amps.

The wire is 12 gauge Dean's "wet noodle" and then I put a 45 amp Powerpole connector on the end. I soldered the Powerpole on too:

So now I had the pack ready for high current so I did some testing. First I ran the pack though on my CBA. Below is the chart with a discharge rate of 3.5 amps down to 28.5 volts. It pretty amazingly flat right up the end around 2.1 ah. This was the first cycle and I'm not sure if it will improve over time. In addition I grabbed the pack almost immediately after it said it was done and I'm not sure if it continues to float in that other 200 ma. UPDATE: I just ran another cycle after it sat on the charger for a while and it put out another 120 mah. I’ll do another test in a month or so and post those up.

In addition to the CBA I also test the battery at higher currents with my Watts up. After removing 1.4 ah from the pack I exposed it to a 13 amp load and it still wasn’t dropping below 31 volts. For my purpose I need it to be above 30 volts to be usable since my controller shuts down at 30.4 volts. I have not exposed my pack to more than 15 amps but it seem to hold it voltage very well. During my test I was sucking almost 500 watts out of the pack but it should be able to handle more since Dewalt claims the drill can out put 750 watts peak. Finished pack photo:

UPDATE: well as you might have seen it has took me a while to get this posted to the forums and I couldn’t resist to try the scooter today. I don’t have my parallel setup wired so I did just a single pack. The results were as expected for a single pack. With a 30.4 amp load a fresh pack drooped down to 29.21 volt. This is a normal drop according to the cell spec sheets for 30 amps. But I was able to ride around and try it out at full speed. I notice the top speed loss but I’ll live with it, and it should only get faster as I add more paralleled packs. My scoot did shut down from low voltage. With 20 pounds removed from the scooter it was easy to get out of my garage. I keep you up to date when I get the paralleled stuff set up.

ADDITION SINCE ORIGINAL POST:

This is my completed pack inside the scooter. All four are paralleled together using powerpoles connectors and 12 gauge wire. They all run through my watt's up (which is way overloaded) then into the controller.

If you have any questions about the set up let me know.

Thanks, magudaman. BEAUTIFUL installation. Exactly what I needed to see.

The RC guys have posted pictures of the inside of the pack in their disassembly tutorials [http://www.rcgroups.com/forums/showthread.php?t=587606], but they are generally not concerned with bypassing the BMS because they plan to throw it away and use their own chargers.

I just ordered the Torx T-10 security bit from Harbor Freight -- and will post pictures when my installation is complete.

Once again, thanks very much!

Burners

:jawdrop: looking nice guys. how do you think it will go with no BMS though, and if you are bypassing it, why not remove it completely???

In my case the BMS gets used for charging. The way the BMS is wired, so that it has a connection to each cell, it probably has an ability to make sure the cells are properly balanced etc. I'd hope/expect that dewalt spent some engineering time to make sure they had reliable packs able to be taken in the field by construction workers, and I want to reuse that engineering as much as possible.

- David Herron, http://davidherron.com/

Hi skooled,

I can't speak for anyone else, but I want to leave the BMS/pack intact so that I can use the original DeWalt charger. This is important for me, because I plan to use the packs while they are mounted in their individual chargers. This allows me to do several things:

1. Use the chargers as my battery mounts
2. Keep the overall vehicle recharge time at less than an hour
3. Charge the batteries while they are mounted on the vehicle (and perhaps while the vehicle is in motion using solar panels and an inverter)
4. Scale the approach for larger vehicles by incrementally adding more pack/charger combos (I'm not a rich guy, this is the only way I can afford to do it).

With 4 packs and chargers (33V/8.8aH -- about $580 at current eBay prices), I have a safe (although bulky), rechargeable pack that can drive a heavy bike on a long commute.

With 32 packs and chargers in the back of a small truck or van (132V/17.6aH -- about $4060 more at current eBay prices), one should get enough range and recharge cycles to make it a practical option for all-electric commuting.

Cheers,

Burners

The bypass is so I can run high current directly through the cells and then charge up through the bms. The BMS does do balancing and cell monitoring so it will keep the cells healthy when charging. I purchased my packs in the dewalt drill combos and then sold the drills(kl900). Making my final cost come to about 420 with 4 batts and 2 charger.

thats what i thought guys, thanks.
so with bypassing for output, gaining higher current draw, is there not a problem with unbalancing an individual cell still, or more even shorting one??? i would hate to be sitting on it if you had a cell "vent with flame"

During discharge unblancing is less critical and less likely. The worst that would happen is you over discharge a cell but you would have to drop the pack volatge pretty darn low to cause any serious damage. The a123 cells are also fairly safe, they don't burst or flame, under even the harshest conditions. The most dangerious part of lithium chemistry batterier is durring charge. As long as they are getting balanced every once in a while they shouldn't become unbalanced under discharge either.

A short is a much more crititical problem that you may want to adress by adding an in line fuse as close to each pack as possible.

I'm sure everyone has seen the nail penitration test from a123: http://www.a123systems.com/html/tech/safety.html#

Can 2 packs wired in parallel be safely charged using 1 charger? thank you, jo

Yes. A fellow over on the "Ready to Ride" bike forum has done just that. See this post:

http://readytoride.biz/?p=105#comment-5332

Cheers,

Bill ("Burners")

I'm the guy who has run Dewalt Packs in Parallel. They work great, and the stock charger charges them very handily!

I've tied up to 5 of them together for a 11.5 AH 36 V pack, and charged them all at once using the Dewalt charger. It takes 5 hours to do the charging on 5 packs. The charger does not overheat at all.

I also tie the parallel balancing ports of the Dewalt packs together, so that the charger also can balance all the packs at once.

Regards,

Brian (mn_aerorider1)

Brian, I just read the thread on the ready to ride forum. Very interesting. And I have some questions to ask for clarification.

You mentioned finding special purpose connectors ... are these ones which the dewalt pack is meant to dock with? Does this mean you do not open the packs and solder connections into the tabs on the pack itself?

- David Herron, http://davidherron.com/

Hi David,

The connectors I mentioned in my pack setup have been a source of confusion to others, as well. They are not the large pack connectors used to plug the Dewalt battery pack to the charger. (I guess others are looking to find a source for these large custom connectors for their pack systems) The ones I am referring to in the Ready-to-Ride forum are the small 5-pin connectors inside the Dewalt pack that are used to tie the Electronic Module built in to the yellow top of the battery pack to the two sets of parallel ports on the top of the black plastic enclosure surrounding the batteries themselves. See the following link for a good picture of the inside of the pack and these five pin connectors:

http://www.slkelectronics.com/DeWalt/packs.htm

Unlike the RC guys, I only partially disassemble the packs to remove the unnecessary electronic modules and the yellow-plastic tops. I then tie the black battery packs of 4 Dewalt packs together using the main power line tabs and the two 5-pin ports built-into the top of the plastic surrounding the battery packs. I then tie a 5th pack (kept almost whole - except for some dremmelled slots for wires), in parallel with these 4 packs. I plug this fifth pack into the stock charger for charging all five packs in parallel. Works like a charm! If one wanted to charge them all faster than 5 hours, one could just use more electronic modules and more chargers and split up the pack lines during charging, but then tie them all together during use, possibly with a nice Molex plug system. I like the idea of tying all the cells in parallel (recommended by an A123 rep http://www.rcuniverse.com/forum/m_4667844/mpage_5/key_/tm.htm) during use, since it self-balances the cells, and I believe will allow you to get more energy out of the whole pack system before tripping the low voltage cutoff.

Let me know if you have any more questions.

Regards,

Brian

thank you for the info guys!

Hi Brian, I just got 2 chargers and 6 dewalt packs and going to wire them to make it 66v 7.5Ah. What is the right way to wire this batteries, series and parallel, or parallel first? And how do I charge them using 2 chargers?

I will also add 4 more packs for a total of 10. Can my X5 controller(72 volt 35A) handle this power?

Jojo

Hi Jojo,

Because of the numbers of packs you've purchased you must already be thinking about 2 pack systems at 33V each, to put in series. I don't see anything wrong with this approach, except to be careful when discharging the series combination to below 54 volts. At 27 volts/pack, you are at the start of the sharp slope of the discharge curve, and if you went much below 54 volts, you might discharge one of the packs below it's minimum of 20 volts, which is where A123 specs recommend as a minimum for 10 series packs. My Dewalt Drill only discharges the battery pack to 27 volts before it shuts down.

I don't know anything about an X5 controller, but if you are nervous about all the available power from these pack systems, you might want to put in an in-line fuse at 35 to 50A. When you parallel up these Dewalt packs, they can supply a lot of current - If memory serves me right, they are only fused internally at around 20-25A each by one narrowed strip of metal in the series connection of 10 A123 M1 cells. Put them in parallel sets of 5 packs and they can easily supply 100A+.

To use the stock chargers to charge the packs, I would recommend building two 33 V pack systems just like I built. See my 5-pack 33 Volt system:

Also shown is a 4"x6" copper stripboard that I use to tie pairs of packs together and to connect the balancing ports in parallel. (I managed to find the exact 5 pin balancing port connector I need to match the balancing ports of the Dewalt battery pack - I'd gladly sell some to you - I have a bunch and I'd like to recoup my costs). My 5-pack system charges in 5 hours. Your 3-pack 33 volt systems will each charge in 3 hours. If you wanted to charge any faster, you could split your pack up during charging and use more chargers.

First remove the yellow covers and electronic modules and all connections from the individual Dewalt packs. Then you want to tie your 3 parallel Dewalt packs together by tying all of the matching balancing ports together and the power lines together. Make sure they are fully charged and balanced before tying them together. You can use one yellow battery top with it's built-in electronic module and connector to charge all 3 packs in parallel through your stock Dewalt charger.

In my case, I kept one Dewalt pack intact and made slots in the sides of the pack to bring out the balancing ports and the power to the other packs. I plug this intact pack into the charger. (I am also using this one pack separately with my Dewalt Drill). If I didn't need this intact Dewalt pack for my drill I would create a connector to tie the pack to the electronic module only when I wanted to charge the pack. Remember when attaching this electronic module to your pack, to tie the main power and ground first, then the parallel ports or you will fry the electronic module.

Later when you get your 4 batteries, just split them among your two 33-volt pack systems. If you build your connections right, in a modular fashion, all you'll have to do is tie in the new ones. The only downside is the charging time increases.

Sorry about the long answer, for your short question....

Regards,

Brian

Wow! complex but undeniably brilliant setup you have there Brian. Here are my assumptions, please correct me if I'm wrong....

1. Remove electronics module for each pack and add connectors to the +/- power & balancer wires.
2. Wire packs in parallel and plug to electronics module. A single Electronics module is used to charge the 4 packs.
3. The copper stripboard is made to simplify the wiring of balancer wires for each pack. Power wires are then wired separately.

Questions:
1. What do you mean by "tie the main power and ground first, then the parallel ports", is this 1st pluging the intact Dewalt pack and then connecting the parallel wiring of the 4 packs?
2. Why will it fry the electronic module, if you do the opposite?
3. I'm not familiar with the copper stripboard, does it have copper lines where you solder your wires to form a parallel connection?

I'm sorry for the barrage of questions. I'm interested in buying your 5 pin balancing port connectors and sent you a PM message...

Thank you again,

Jojo

Hi Jojo,

You are correct in all of your assumptions, except that in my setup I am actually charging 5 packs in parallel, you forgot about the charging pack that I am using as well.

To answer your remaining questions:

1. What do you mean by "tie the main power and ground first, then the parallel ports", is this 1st pluging the intact Dewalt pack and then connecting the parallel wiring of the 4 packs?

I am referring to when you have a completely disconnected electronics module and you are attaching it to any battery for the first time.

I believe once it has some main power wired to the electronics module, that you don't need to worry so much about the order when adding additional batteries, as long as they are matched in voltage and well balanced. Just to be careful, however, I always try to add the main power lines first when attaching a new battery in parallel with the others - I'd rather get a lot of juice through the main connectors, then through the small balancing connectors.

2. Why will it fry the electronic module, if you do the opposite?

I am not sure why, I don't know enough about the internal electronics of this module. Some sensitive internal component needs to be properly biased, I guess. I just know it has happened to me and to others on an R/C forum that have warned everybody about this .... I have a link somewhere if you want it. Fortunately, I have quite a few extra modules, since I am only using one of 5 for charging.

3. I'm not familiar with the copper stripboard, does it have copper lines where you solder your wires to form a parallel connection?

The bottom of the copper stripboard is in the middle of my images (note it is tin-plated for easier soldering) , and the top view of the stripboard is on the bottom. They have strips of .1' spaced copper running full-length and are riddled with .1" spaced holes throughout and are made of a pretty tough plastic/epoxy material and only cost a $1 to $3 each, and make for easy soldering. (People use them all the time for electronics projects and many electrical connectors and electrical components come in .1" spacing)

I like the stripboards for this application, because besides being great for creating a lot of parallel low current connections between the battery port connections, I can drill offset holes in them and use them to tie the two facing Dewalt packs together using the screws that come with the packs. (Note that to keep the stripboard level with the top of a battery pack I had to add a 3/8th" thick standoff/washer under each screw hole of the stripboard. I made these standoffs by cutting off some cheap gray plastic tubing sold in the plumbing section of Home Depot - I believe it was 3/8" tubing).

Instead of using a stripboard, one could easily just twist and solder the correct paralleled wires together, and wrap them in electrical tape. Wouldn't look quite as nice, however, :)

Note that this battery pack I show here isn't quite done, yet. I am also still planning on tying my 4 packs together using some long thin pieces of aluminum angle stock (also sold at HD), wrapped around the pack, or running through the middle - I haven't decided yet where. I will seal the 4-pack in plastic/tape, and will attach the main removeable charger/drill pack to the top of the 4 others using velcro strips and straps.

Several missing pieces of helpful information:

- In my picture where the balancing port wires come out the small slots of both sides of the charging pack, I have two very small stripboard pieces that adapt and tie the short balancing wires of the electronic module to parallel connected balancing lines going back into the charging pack and parallel connected balancing lines going out to the end stripboard of the external 4 packs.

- It is a good idea to use the temperature monitoring sensor of the pack to monitor the batteries during charging, to take advantage of this safety feature, which cuts off charging if the temperature of the battery gets too high. In my current setup, I only monitor the temperature of the charging pack. If you did a separated electronic module for charging, and wanted to monitor the temperature of your packs during charging, you could splice in longer wires for this sensor and slip it into the center of your 4 packs during charging.

Best Regards,

Brian

`mn_aerorider1,
We hope it was ok to post your pictures, rather than just the links.
If you need any help we suggest you either see our Help Tutorials or contact help [at] visforvoltage.org

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Are 10awg booster cables, used to jumpstart cars, good enough to use for parallel and series wiring of these batteries? They are quite flexible and may handle the high currents...

Hi Jojo,

No reason why 10 gauge jumper cable won't work, especially the flexible kind. Since it is 10 gauge, it probably will not fit in the soldering holes within the Dewalt pack, so you may need some kind of adaptor between the 10 gauge cable and the soldering holes. I have used a small piece of solid 14 gauge copper wire from old pieces of home wiring cable to construct an adaptor when I needed to tie two 14 gauge wires into one of these soldering holes... It worked pretty well, especially if I pinched it around the wire prior to soldering.

Best Regards,

Brian

By the way - If anyone reading this post is thinking about tying stock Dewalt 36V battery packs in parallel as shown above, I still have a bunch of the 5-pin BMS connectors that match the connector holes inside the Dewalt packs - See my pictures above. I bought them in volume from the following manufacturer in Taiwan:

http://www.jswire.com/CH2503electroni-connector.htm

The shipping costs were a killer, and I'd like to recoup my costs.
I'll sell them in groups of 20 5-pin connectors plus 100 crimping pins for $10 + shipping costs.

Thanks,

Brian