Can I make a battery pack with these power tool batteries?

[Synthman]

I recently got a new cordless saw (Bosch GSA 10.8vLi if anyone's interested) and it came with 2 batteries. I also have two batteries from cordless drill/driver I've already got. And now two chargers.

Bosch Li-lon Battery Pack 10.8V | Screwfix.com

They are 10.8v 1.3ah lithium, with a fast charge time. The batteries measure about 12.2v when fully charged.

This is not a serious project, but would like to know out of curiosity if it would work?

Would the batteries have to be connected in series or parallel?

 

[Scottyf]

Simple answer.

Yes.

However the voltage and capacity are very low . So you would need alot more to make them actually useable in an ebike application.

 

[Scimitar]

You'd need a lot of them. However, I've done it with Bosch Fatpacks (36V, 2.6Ah), six of them in parallel. Charging is a doddle - just use one of the removed charging adapters and stick it in the charger, the charger/bike connection is simple flex.
Check EndlessSphere for Bosch Fatpacks and absorb.

 

[Synthman]

How many would I need to make a 36v battery?

 

[flecc]

It's problematic with that awkward 10.8 voltage. The 12 volts fully charged can be ignored, that disappears the moment a load is applied, so you'd need 4 in series to make 43 volts and use that with a nominally 36 volt controller that can accept that voltage.

You'd need a number of those series sets in parallel to make enough capacity. For a practical minimum of 6.5 Ah, you'd need 5 of those series sets in parallel, so 20 in all.

For a far more useful 10.4 Ah, you'd need 8 sets in parallel, so 32 in all.

Obviously uneconomic as ever, £860 for the former, £1376 for the latter.
.

 

[Synthman]

It seems pointless then. Wonder if I could use the cordless drill to directly power the bike instead? I know that's been done before!

 

[flecc]

Yes, a few have done that, but the power is very low for that purpose.

E-bike batteries can seem very expensive, but the alternative methods using other types are rarely productive in the longer term in my view. Tool use conditions are usually very different from e-bikes, the one intermittent, the other often continuously demanding high currents for an hour or more, not at all the same thing, especially in terms of battery life.

 

[Scimitar]

And yet, it doesn't seem to bother the Fatpacks - six in parallel are quite happily working away. It was the fit-and-forget nature of the Konion cells in the Fatpacks that appealed to me - rather than LiPo and always be wondering if my workshop/house was going to go up in flames.
I might do LiPo next time, simply for cheapness and bang (hopefully not literally) per buck; but I'll be charging and storing outside.

 

[Scottyf]

Lipo isn't that bad as long as your not a muppet with it.

 

[NRG]

Lipo isn't that bad as long as your not a muppet with it.

That make good tag line!

 

[Scimitar]

Lipo isn't that bad as long as your not a muppet with it.

Hah. Care to tell that to the folk who've done everything right and STILL had a bang/fire/flare-up?
As I said - outside, or not at all. I wouldn't take the chance of having a LiPo battery indoors.

 

[NRG]

The earlier Cobalt based lipos where certainly dangerous but the latest Lipos with compound cathodes have proved to be more reliable, one guy on ES even reusing puffed cells by releasing the gas, squeezing the cell back together with a vice and re-sealing! OK not something I would do or recommend but given care of charge and discharge there is no need to fear them to the same degree as previously.

 

[Scottyf]

Like nrg said it's no where near as bad as what it was.
And in an ebike application your hardly getting the cells to perform that hard at the lower c ratings. An if you don't charge at a hideous rate they can be good.

But your right keeping them outside would be the best just incase. At least for peace of mind.