brent_co

I am thinking of making a battery pack similar to what has been done with the DeWalt A123 batteries.

Currently I have an electric trimmer that I purchased a couple of weeks ago with 2 batteries. These batteries are Black and Decker XR360 @ 2.4 ah. I can get 2 more of these for $100 each and then make a special case where I could add the batteries needed for my specific journey. Short trip to the grocery store - take 2 batteries. Travel to the office take 4 (or more).

Would I be better off just to buy a single battery dedicated for my e-bike? The big advantage I see to using these is the dual purpose - use for my bike during the week and my lawn equipment on the weekend.

BTW - I will be using this to drive a Wilderness BL-36 hub @36v for a 15 mile journey most days

Thanks

wernmax

Biggest downside would probably be one charger for 4 batteries. And rigging up the plug-in's for the bike.

misslexi

What chased me away from the Dewalt A123 units is the degree of difficulty required to harness them, as you probably know they are not just a plus and minus 36V interface. And they use a proprietary physical interface which really complicates things. Then there's the BMS built in to the charger.

I don't know anything about the B&D packs but if they are anything like the Dewalt, it could be a big challenge.

I like the concept though, as you described, grab as much as you need and no more than you need.

In any event, I wasn't willing to consider the A123 as my first battery pack for the above reasons but I did promise myself once I had a working machine to ride that I'd revisit it. To date it's been an empty promise

brent_co

Great input, thanks. I have been tinkering today with the B&D pack but have come to realize the batteries might work well, but creating a decent carry system without modifying the battery would be more trouble that it's worth.

I am looking at starting with 3 x 12v in series 20ah batteries for a 26v system. This will give me a range of 16 miles based on usage of 1ah / mile. My plan is to buy a Wilderness BL-36 kit.

Once I have 6 months of e-bike commuting under my belt I think I will tackle building my own battery pack using NiMH batteries.

lyen

Go with your current B&D packs. It should work fine. All you need to know is to discharge them properly & evenly. I am currently using the Dewalt DC9360 packs for over a year for 20 miles a day and it is still a beast. The is no better & safer batteries out there.

brent_co

Thanks for sharing your experience. If I connect them in parallel, won't they discharge evenly? Do I need to build a BMS of some type?

How many DC9360 packs are you using for 20 miles a day? How did you wire them?

misslexi

The Dewalt DC9360 is a 2.4AH pack, how many do you use to go 20 miles? how do you plug them into your bike (any mods, would they still be covered by warranty)? Any special circuits to enable them to produce power? What was your acquisition cost per pack?

I agree A123 (Dewalt) packs are without peer, accordingly they are premium packs.

For those seeking tremendous performance in terms of discharge/recharge, I think they are worth pursuing. For everyone else, they are a solution in search of a problem.

wernmax

I bought 10 36V DeWalt packs for the A123 batteries in them, a couple years ago.

I opened them up, threw away the BMS's, recut the factory 10 cell packs into 4-cell bundles, soldered on 10 guage insulated wires to the cut tabs, and reassembled them into the cases...2 - 4 cell packs and a 2-cell pack for the origional 10 cells in each pack, then wired the 8 - packs (several cells in the origional 10 packs were DOA) into a 12 series - 5 parallel , 48V11amp 16lb battery.

Then I bought four - LiFePo4 12V Smart chargers from....

https://www.batteryspace.com/index.as...OD&ProdID=4908

and wired them into the pack at 12V junctions.

Since resting voltage on a 48V - A123 pack is about 54V, and discharged is about 48V, I watch pack voltage with a voltmeter as I ride so it doesn't slip under 48V no-load.

I was powering a Chrysalite X-5 motor through a 4840 controler to run my prototype trike that probably weighed about 400lbs with me onboard, and it still accelerated up some pretty steep hills and had a top speed of right at 35mph. Love those batteries.

Now you can get a 48V10A pack with Battery Management System for about $700 from the same people as the chargers. They seem to keep getting cheaper, but I'm sure they're not the A123's.

https://www.batteryspace.com/index.as...OD&ProdID=4986

While building the battery pack, I managed to short out one of the 2-cell 6V packs while moving the trike. A tea kettle sound started almost immediatly, and the ends of the batteries popped off releasing a whole lot of noxious smoke. The whole thing was over in about a minute leaving melted wires and almost red-hot batteries sizzling in the battery compartment.

I'm sure you could open up the B&D packs to run power wires and Anderson plug connectors out, bypassing the BMS and making paralleling the packs much easier.

lyen

I am using only 4 packs in parallel at 33.75 volts. The power out of the four battery packs can easily be evenly distributed with a couple of tiny schottky diodes. I use the existing BMS from the battery packs & use the existing charger(s) to charge them & balance them. I simply attach them to a Dewalt light with a few resistors to engage full power/voltage from the built-in BMS of the battery packs. The good thing about it is I kept my batteries intact with warranty still covers. Not only do I save time + trouble & it looks very pretty on my bike. My goal is simplicity.

I commute to work for 20 miles a day round trip. Which means I get a chance to recharge the packs every 10 miles. I can charge them in less than an hour with four chargers at work if I want since I have multiple chargers at home & at work.

Since you already have bought your Black & Decker packs. You should not invest extra money on something you wish to have but not needed to have since we are all in the survival mode economy. The key is to try to utilize your existing resources and go from there. That's one of the thing making America strong by support American products with innovation. I can guide you thru to hook up your B&D packs if you can take photos of your packs with diagram and/or the positive + negative wiring to the connector. Also, let me know the exact model/part number of the battery & how far you want to go one way.

wernmax

I'm guessing you're one of those EndlessSphere guys.

I love that site.

lyen

Please see my other reply for your answers. The definition of special circuits depend on your knowledge of electronics. To me, there is no complexity involve. You don't even have to open the battery case at all. The key in simply find a way to discharge the packs evenly. In addition but optional is to enable the BMS from the flash light adapter. Not again, it is not really needed. I use it just to mount it on my bike to make it looks nice and enable the internal BMS out of the battery packs.

As for how I plug them to my bike, I simply have two wires sticking out from the flash light adapters to the motor controller.

The current price on eBay for packs like this are much higher than what they used to sell a couple years ago. Therefore, it may no longer be practical. The best to go with currently is the Bosch 36V fat packs in terms of price/power ratio but they are explosive if not use with care. Still the Dewalt 9360 is the safest & most powerful packs in the US. I highly recommend Dewalt and Black & Decker to support America.

lyen

How did you know I am one of those EndlessSphere guys? I am a friend of Keywin who built the Ecrazyman Shenzhen controllers. We have actually discussed about the Dewalt batteries & comparable LifePO4 battery technology in China face to face. However, nothing can touch the A123 as of today although engineers & manufacturers in China tried really hard but there is still minor differences. Also, the honestly of the LifePO4 packs from China is questionable in terms of the actual capacity & longevity. The only way to find honest people to deal with is with their native communication & social connection. I as a Chinese American do support American products first, Chinese products second whenever possible.

wernmax

You knew about the voltage dividers to get power out of the DeWalt packs. I first read about them at Endlesssphere when they were working it out.

And just about anybody working with E-bikes knows about those guys. Wish I was smart enough to fill out the membership. I can't seem to get on.

JS Tyro

Just a comment about possible confusion some might have. The B&D XR360 battery packs are not LFP but NiMH (according to a Google search). The B&D VPX batteries (nominal 7V) are LFP - based on the 1.1 Ah A123 (18650 cells). The DeWalt 36V packs are LFP based on the 2.3Ah A123 (26650 cells).

So - the handling of the B&D XR360 cells is as per NiMH cells. Any info that applies to building big NiMH packs applies here. They won't be as light weight as LFP but better than SLA. You can probably adapt a regular Maha or similar charger to work well with them.

Speaking of NiMH - has anyone found a really cheap source of high Ah NiMH D cells? Sanyo Eneloop would be a great alternative to heavy SLA and pricey LFP.

BTW - I remember reading a year or so ago about not putting more than 10 A123 cells in series. Apparently they weren't rated for more than 33V (which may explain why the DeWalt are only 33V and not 36.3V - i.e. 10 cells and not 11). However, I haven't been able to find this info anywhere; I should have bookmarked it. Does anyone know about this? Perhaps A123 changed the design an bit and got rid of this restriction or perhaps I'm confusing it with something else.

wernmax

Good catch and good comments, JS Tyro.

I'm just blathering away on the assumption those B&D batteries are LiFe's....never even thinking to check it out. Great. Potential eye opening excitement waiting to happen there, should they be treated as such.




I have been running a NiMiH 36V13Amp pack on my Tidalforce 750 for about three years of almost daily use, probably about 3,000 miles, even pulling a trailer on occasion. They seem to be a good tough battery for the money. (about $500).

I hadn't heard the more than 10 cell thing, although it may be a safety issue, as those A123 can put more than a 100amps through a shorted circuit.

I'd really hate to short my 48V pack, and there's a lot of stupid ways for it to happen in real life applications. I run a 40 amp fuse on each 12V pack right where the positive lead comes out of the battery case to minimize the risk. I fuse everything battery related, it's scary how many times you'll still pop one doing a project.

misslexi

If one is after power density then using these power tool packs makes a lot of sense.

If one is after energy density then I still believe the ping LiFePO4 packs are the way to go.

Concerning Made in USA (or Canada); are we sure where A123 cells originate?