A volt is a volt and an amp is an amp

[Scimitar]

I've been noticing my Bosch charger doesn't like it much when I have to recharge my six Fatpacks (10 LiMn cells per battery, in series to give 36V - then six Fatpacks in parallel presented to the controller or charger)
It copes well enough if I've only use 3.0Ah but anything above 7.0Ah, it starts to smell a bit hot. Not blisteringly hot and it might well be ok, but it leaves me uneasy, and they're not cheap.
I have the original 36V lead acid charger that came with the bike kit - would it be sensible to bung that on and monitor the voltage, to say a max of 38 or 39V and let the Bosch charger finish off?
These Konion cells are very robust and tolerate things that would have a normal LiIon cell choking or dying. I'm so impressed with them my next battery will be built using these.

 

[jerrysimon]

Yes the Konion cells have a great reputation. I considered them but they are hard to get hold of as single cells.

Checkout endlessphere as there is a large post on there about careing and feeding Konions.

Which Bosch charger is it ?

I am pretty certain the Lead Acid charger will not be any good as I use that for 12s of 3.3v A123s whereas your cells are 3.7v.

Again on endlessphere I think there are some posts about using larger server power supplies which you can tweak the voltage and use higher current charging on.

PS is it these you use

http://www.ebay.co.uk/itm/Bosch-36V-2-6AH-Li-Ion-Premium-Battery-Power-Tool-Rotak-Hedge-Trimmer-Chainsaw-/130716879095?pt=UK_Home_Garden_PowerTools_SM&hash=item1e6f5548f7

How do you bipass the currrent limit ?

Regards


Jerry

 

[flecc]

A volt is a volt and an amp is an amp

Watt?
........

 

[oigoi]

Could you use a plug in timer where your charger plugs into the wall socket to give the charger a half hour or hour break to cool down halfway through charging?

 

[jerrysimon]

Take a read through this thread.

Endless-sphere.com • View topic - Bosch 36V fatpacks opened up

Regards

Jerry

 

[Scimitar]

Yes the Konion cells have a great reputation. I considered them but they are hard to get hold of as single cells.

Checkout endlessphere as there is a large post on there about careing and feeding Konions.

Which Bosch charger is it ?

I am pretty certain the Lead Acid charger will not be any good as I use that for 12s of 3.3v A123s whereas your cells are 3.7v.

Again on endlessphere I think there are some posts about using larger server power supplies which you can tweak the voltage and use higher current charging on.

PS is it these you use

Bosch 36V 2.6AH Li-Ion Premium Battery Power Tool Rotak Hedge Trimmer Chainsaw | eBay

How do you bipass the currrent limit ?

Regards


Jerry

Yes, it's those 2.6Ah fatpacks (smaller ones are 1.3Ah and not worth the bother) Six in parallel, so current limiting isn't a problem
Even with four parallel it was fine.
I read that ES thread from the beginning, two years ago and kept up with it - slightly disappointed there's been no recent developments there, but I suppose everything needed to be said about them has been - just fit and go, basically.
The Konion cells are available singly, but not all that cheaply - I've been keeping an eye open on ebay and other places.
Trouble is, I'm not sure whether the aftermarket fatpacks use the same cells - there's a high chance they do, as they're using the same charger and I doubt a less safe chemistry would be used willy-nilly, but you never know. The aftermarket FPs are ~£60 new, so quite attractive, compared to the new price of Bosch FPs - around £120 iirc.
Otoh, some of the dedicated e-bike LiFePo batteries at the £200 mark for 10Ah start to look like good value, and that's what I would've went for in the first place if the prices then were as low as they are now.
The huge advantage of using FPs was I could build up a battery a bit at a time.

The charger is a standard Bosch one for these - an AL3640.

edit...
I've just found the same question on the second last page of the fatpacks thread - after I'd stopped reading it last year.
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=7569&start=555
Looks like a no-go for that unless I can tweak the output accurately. I'd probably be better off buying a more specialised charger from HobbyKing or somewhere.

 

[Scimitar]

Could you use a plug in timer where your charger plugs into the wall socket to give the charger a half hour or hour break to cool down halfway through charging?

Absolutely! Stroke of genius, my man.
I have a few of those too; and I was using them for similar applications, just never connected the dots.
I did think of fitting a fan to the charger case, but it seemed like such a pita to do.

 

[Scimitar]

Well, today I got home from a ride and the battery was 50% discharged, so dug out a plug-in timer and connected the charger up with 1/2hour on/off intervals. I was varnishing the stair, as you do, when I heard this whining noise - the charger had got a bit warm on one of the cycles and lo and behold, the whining racket was a fan in the charger case.
Huh. Saves me a job, I suppose, but I'm not too impressed at its efficacy, so might try fitting a better quality PC fan from Dorothy Bradbury.