[mxmtech]

I have a couple of good battery packs from a cordless drill that I am going to solder into a 20 cell pack for my ebike. I found what looks like a suitable charger at this site batteryspace.com http://www.batteryspace.com/universa...connector.aspx
at the same site they have this battery pack advertized for sale http://www.batteryspace.com/li-ion18...withpcb-1.aspx
this battery pack has a maximum output of 5 amps so naturally it won't power my ebike the way it is
Does anybody have any advise for me concerning soldering the battery connections to handle a maximum 30 amp draw?

[major]

Originally Posted by mxmtech

Does anybody have any advise for me concerning soldering the battery connections to handle a maximum 30 amp draw?

Hi mxm,

Most will tell you not solder cells like that. You need to spot weld. But what the H. I do it. You need a large soldering iron. I found an old one which weighed about 8 pounds. It was like a one kilowatt iron. Pre-tin the cell and the strap. Then with the iron good and hot, press down on the strap on top of the cell. As the tinned solder starts to flow, feed in a little more solder. Get in hot and get out fast. I find it takes 3 hands. So get a helper. If you mess it up, let it cool completely and try again in about 10 minutes. If you heat the cell too much, it is damaged or can burst. You need to accomplish the solder joint in a matter of seconds. Get good electrical grade solder and good flux.

Wear safety glasses.

And for the record, I don't recommend you try it

major

[mxmtech]

I can pack the cells in wet sand to keep the heat down and I can build a soldering iron by driving a bolt into a piece of copper pipe and heating it with my propane torch I suppose I could flatten a piece of the correct guage of copper wire for a strap. This experiment is with free batteries. Is there anything else that I should be considering?

[major]

Originally Posted by mxmtech

I can pack the cells in wet sand to keep the heat down and I can build a soldering iron by driving a bolt into a piece of copper pipe and heating it with my propane torch I suppose I could flatten a piece of the correct guage of copper wire for a strap. This experiment is with free batteries. Is there anything else that I should be considering?

Hey mxm,

You don't understand. If the sides of the cell get hot, you're screwed. Forget the wet sand. Keep it clean and neat. I'd stay away from propane. Go electric. The iron I use looks something like this 110436914748 eBay item #, $5. Or something like they might use for stained glass lead work.

You can do what you want, but I advise to get reasonable tools and use a clean and safe set-up.

And for the straps, get some thin copper strips or braided copper ground strap. New, clean copper will work. Old crappy stuff will give you problems.

Regards,

major

[mxmtech]

I tinned a piece of 10 guage wire with my torch and used my 115 watt soldering iron to tin the existing connection tabs and make the connection. I just strung both strings of batteries together to make 36.2 volts and hooked it up to my bike. I figured if I was just careful to keep the amp down it shouldn't damage my controller, especially since I have seen on this site that it is safe to do so.
I ran my bike up and down the driveway on the nicad pack but it had no power whatsoever. It didn't even register on my ampmeter (60 amp analog)
I'm thinking that the amp limit is integral to the battery (this pack is just C cells) and that a D cell is only capable of a 5 amp output.
So I put the lead acid battery back in and went to work.

[spad4me]

Originally Posted by mxmtech

I tinned a piece of 10 guage wire with my torch and used my 115 watt soldering iron to tin the existing connection tabs and make the connection. I just strung both strings of batteries together to make 36.2 volts and hooked it up to my bike. I figured if I was just careful to keep the amp down it shouldn't damage my controller, especially since I have seen on this site that it is safe to do so.
I ran my bike up and down the driveway on the nicad pack but it had no power whatsoever. It didn't even register on my ampmeter (60 amp analog)
I'm thinking that the amp limit is integral to the battery (this pack is just C cells) and that a D cell is only capable of a 5 amp output.
So I put the lead acid battery back in and went to work.

The c cell batteries are rated at something like 2200 mah

Series gives you voltage Parallel gives you amperage.
You need like ,I just fudged but not by much, 1200 cells in 36 volt strings to get near your voltage with about 70 amps
You could probably get away with 400 to 600 c cells
Like the early prius battery wow.