Battery rack for power tool batteries for use on ebikes

[Lessss]

I am annoyed with the concept of having to make battery packs.
I want to use the packs as they are from power tools.
What is needed is a rack of some sort.
This would allow us to keep the packs intact maintaining their waranty. It would allow us to grow the pack size as the budget allowed.
We could start with say a small 6 amp hrs then grow to 12 18 and 24amp hours.
No need to worry about huge voltage spikes as we could turn on each segment separetly building up the voltage in stages.
So this is what a 56V 18amp hour pack would look like. all the complex wiring is in the rack. The rack would need to use the conector slots like on the chargers.
I'm sure this isn't the first time something like this has been mentioned. So what are the hurdles in making this?

 

[paultrafalgar]

I don't know about Milwaukee packs (as in your picture) but it has been said on this forum that the BMS on DeWalt packs are no good, hence re-assembly. I'm thinking the way to go is non-soldered packs, so that you can dissassemble to do balancing. e.g here: http://www.tppacks.com/proddetail.asp?prod=EBKE%2DA123%2D4s4p%2DKIT

 

[Joey]

I saw somewhere in the forum that one individual used a piece of plywood and mounted battery packs (I think they were Makita 18V LXT) on both sides. I just ordered connectors for Milwaukee 28V packs and was planning to use G10 fiberglass. This is the stuff that circuit boards are commonly made of and it comes in many thicknesses. I'm not sure how thick it would need to be to support 6 to 8 packs. Can any of the experts on this site recommend a thickness for this purpose?

-- Joey

 

[pwbset]

I just last night finished a triangle build of 2s3p Milwaukees that you may want to peek at. It was inspired by jondoh's how-to videos and from the makita triangle mount pack I saw here somewhere... can't find the thread.

http://endless-sphere.com/forums/viewtopic.php?f=6&t=4716

I really like your idea of being able to expand or even minimize a pack based on distance/power needed etc., but, for me, I'm not sure where I could expand to on my little MTB... maybe a 2s2p 4-pack over the front wheel or something. I may make little dummy "pass through" connectors also so I could just do 2s1p for quick trips to town or whatever. The 2s3p triangle pack weighs exactly 15.4lbs and the bike weight feels nicely balanced.

I just used a piece of solid board I had laying around in the garage. Works great and the connector block assemblies are hot glued and tapped/drilled with little screws too. Snug as a bug.

 

[pithy]

very nice pwbset! i've been thinking about trying to do something like that myself to balance the weight better than my current setup:
http://endless-sphere.com/forums/viewtopic.php?f=6&t=3995

how does it feel to ride with those in the middle? is it so wide that it gets in the way of pedaling at all?

 

[pwbset]

very nice pwbset!

That's ironic because it was your board that originally inspired me!

how does it feel to ride with those in the middle? is it so wide that it gets in the way of pedaling at all?

I was worried about that, but so far it isn't a problem. You just sort of adjust to it and you can pedal full strength no sweat... er... well... sweating, but...

 

[efreak]

great topic for discussion and fairly reasonable question and you certainly can,t

argue with still being able to use the warranty on them and reasonable price.

 

[GGoodrum]

I tried to go this route initially, with DeWalt packs, but as Paul points out the DeWalt BMS is just crap. I've not ever tried the v28 BMS, so I don't know if they will fair any better.

The mounts were made from 3/32" black G10, and were "T"-shaped, with the packs hanging from top of the "T". The bottom part of the T was sized/angled so that it would slide into a standard Topeck rack channel. I added pieces on top of the lower mount that duplicated the Topeck channel, so that the upper mount can slide onto the top of the lower one. The packs slid into holders that were simply thicker pieces of G10 on standoffs. There were custom connectors made using blade-type terminals, for connection into the packs. Mechanically and electrically, everything was sound, but the BMS has a 15A limit, so I had to then use the outer negative connection, which bypasses the BMS. The problem is that the first time I tried it, I ran the cells low enough that they wouldn't charge on the DeWalt chargers. It turns out just one or two cells can go just a bit too low, and then the DeWalt charger won't charge them anymore. the cells were fine, and when I took apart the packs, and individually charged the cells back up above the cutoff point, the DeWalt chargers worked again, but by this time I decided this wasn't going to work, and moved on.

-- Gary