A123 dewalt 36v (m1)

[aaannndddyyy]

I have been looking for a set of batteries ps12120 sla for my new kit poject an old shooper 36v sla rw motor with full electrics, lights, indicators, horn just need to find a bike to fit it two know.
And came across the Dewalt DC 36 VOLT (A123 Systems) LITHIUM - ION BATTERY PACKs with 30 amp continues. (The M1cells per the manufacturer's designation) are promised to last longer than LiPo and tolerate more abuse. They should last longer than NiMH. Another real savings consideration is in charge times 30 to 60 min, these are used for power tools but I have seen a video on the netYouTube - Ultimate hybrid electric bicyclewith them used for ebike they allso look fairly easy in Building Packs DeWalt 36V Technology (A123 Systems) allso found this forum which has some good info Endless-sphere.com :: Index

 

[coops]

Hi andy

Check out the advances in battery technology thread on this forum, if you haven't already, for more discussion of these and other new battery types and their suitability, or not, for ebikes... .

Stuart.

 

[aaannndddyyy]

Cheers Coops hadent seen that thread.

 

[Ian]

They look good at first glance Andy, but at only 2.2 Ah they are a quarter of the capacity of a typical bike battery and cost almost £200 so are not cost effective even if they do last longer.
Also I believe actual voltage is 33V which could cause problems with some controllers.
And as for being promised to last longer, the manufacturers won't back up their "promise" with a warranty.

 

[kraeuterbutter]

just seen now this thread...

for the promised cycle-life:
this is true:

tested by a hobby college with 8C and 10C continouse discharge current
the cell went to about 1000Cycles with a constant loose of capacity
(7% after the first 400cycles)
~ 20% after 1000cycles
but the innerrestistance and voltage level stayed same durring this 1000cycles !!
(thats not common with for example Nimh, which loose capacity AND power/punsh)

after 1050 cycles also degrading voltage-level started, innerrestistance stared to rice
cell was always discharged to 2V (so completley empty)

its to say: durring 250 charge-cycles (after the first 400cycles) the cell was charged to 4,3volt !!!! instead of the recommended 3,6Volt
it was no higher capacity loose noticable than seen with normal parameters during the first 400cycles

it was charged with 3-4C, so during 20min each time

so: for cycles: in a bike where you will seldomly see more than 5C this cell WILL get 1000FULL cycles
(you will not empty your pack everytime fully, so in reality you will see even more cycles)

for caldender-life: A123-systems says 10years...
well.. its not possible for use to test THIS except of weighting 10years

33Volt: thats right...
you can see how it performes at discharge
HERE: Elektromodellflug - BMZ 26650-X - LiPo-FePo4 im Test

maybe a problem for many controllers..
maybe you can use 11s ?!?
would be: 39,6Volt after charging
36Volt nominal
so during discharging (depends on current) between 36Volt and 33Volt
and when getting empty falling down to ... well.. 20Volt


for soldering:
maybe this (lot of pictures) is usefull:
Side-by-Side: How To Build a Battery Pack from A123 Cells - RC Groups


Inline:
Lomcovak.czilna:A123 za sebou

anotherone:
Dissecting DeWalt 36V Packs (A123 Systems)

in this links its sometimes said, that the "point" at the bottom of the cell is a vent for safety reason and must not be over-soldered
THAT IS NOT TRUE !
the electrolyt was filled in there..
the over-pressure security unit is on the other side of the cell..
so the point can easily over-soldered
soldering A123 is as easy as soldering Nicd or Nimh

for the low currents you use in an electric bike you can even use the welded taps which are already on the cells when you dismantel a A123-Dewalt pack

when you considere all points (safety, easy handling, weight, lifetime, possible power, price ....) the A123 are hard to be beaten

 

[flecc]

The 39.6 volts that kraeuterbutter mentions is ok for most ebike 36 volt controllers. The eZee controller is one of the fussiest, but that limits the maximum to 44 volts, between 43.5 and 44.5 volts average.

I don't call the DeWalt packs a good price though. At around 36 watt/hours for £100, against 144 watt/hours for £100 with the standard eZee Li-ion battery, they are horribly expensive at four times the price. I haven't bothered to check the A123 prices, but I'll bet they aren't too competitive either.

Of course, at 162 watt/hours per £100, NiMh is once again the best battery!
.

 

[Ian]

I have seen DeWalt batteries on ebay for as low as £70, thats still a lot for a 2.2Ah battery though. They are also not that light at 1.1kg giving a capacity/weight ratio of 66Wh/Kg, not that much better than the Ezee NiMh at 59Wh/Kg. By comparison the Ezee Li-Mg battery works out at 82Wh/Kg, at least in theory before any capacity loss.