[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.

[mxmtech]

these batteries are only 1500 mah, I only strung them together for an experiment. When I get more I'll break them into 20 cell groups and hook them up in parallel. When I give the motor 30 amps I can smell the insulation burning so I don't intend to do that again except in an emergency situation. This was up the most extreme hill in my area. (British Columbia, Canada)
The motor is rated for 18.75 amps continuous but when I do that I only get about 4 kilometers out of my SLA pack, so I don't want to do that much. (One hill that would make me puff if I had to pedal and I'm pretty fit) average speed of 30 kilometers/hour
When I held it to 5 amps I went 22 kilometers and pretty much fully discharged the batteries but the recharge only used .26 kwh. Average speed of 20 kilometers/hour.
I haven't learned the math to calculate the AH capacity of my 24 volt battery pack yet, they say 12 AH but I don't think they are in top notch shape even though I just got them a month ago.
I figure I need 120 D cells to give me 24 volts at 30 amps 30 AH, but only 40 to give me 10 amps 10 AH and that would be a good start.
Nicads like to be fully discharged and give the full voltage output all the way to full discharge even in extreme cold, whereas lead acid batteries like to be kept at a full charge especially when it's cold, so to me it seems a no-brainer to use a nicad pack from charging station to full discharge, then switch to lead acid then on to the next charging station.
I ebike 4 kilometers to work from home, recharge at work then go back home, change battery packs, and ebike 4 kilometers to my girl friend's and recharge, then ebike back to my place in the morning for a battery change before going to work. Two battery packs, three charging stations, and two chargers. I average 16 kilometers a day but sometimes I do a lot more. There is one big hill from my place to my gf's place and one big hill from my place to work.
I got my ebike September 2008 in a not working condition and finally got the parts in March 2009. I've been using it as much as I can ever since.
In the beginning I was only using it on nice days, then when I got fenders I started using it five days a week, now that I've built a trailer I'm using it every day that I can. (I tote about a hundred pounds of tools)
Sometimes, like today, I have no choice and I have to drive my gas guzzling pig (4 k/liter)

[mxmtech]

The price on the nicads is too good to be true.
Their charger is $30 but they want $76 shipping and handling
Their 24V Dcell battery pack is $72 but they want $98 shipping and handling.
Will be looking for another source
The End