welding of an ebike battery

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solarshift

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Sep 23, 2012
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im going on a long tour partally in remote arias and it would be great to be somehow be able to weld the bike back togeather if I need to. Im going to have 60ah of 16s LiFePO4 and an 80a controller. I know its posable to arc weld directly of 24v of lead but the current would bepritty massive. idealy I have a setup that can produce variable amps between say 40A and 60A at not mutch more than 20v and runs directly of my battery. would it be posable to rectify the controller oultput, disconect it from the motor and limit the battery amps to produce an apropriate wattage/ current at the ark? or is this stupid and desten to burn my controller with to mutch current going threw the fets?
 
Given the number of controller failures I've seen or read of because of poor connections causing arcing, I don't think it'd be a great idea to use your controller for that. It could be possible to protect the FETs from the RF spikes from the arcing, but I dont' know exactly how you'd do it.


Welding right off the battery, if there's no BMS, fuse, or fusible link on interconnects, or per-cell built-in protection (like some 18650s have) could work ok if the current capacity is high enough.


For variable voltage, you can simply setup the battery so you can parallel sections of it for lower voltage but higher current. Variable current, well, not sure about that.

But I couldnt sya if any particular battery is suitable for this.
 
ye, thiers a bms, its a duct tape battery so I parelel it down to a lowish voltage though that would be ideal if it was esy enough. the battery is easelly capable of suplying 80- 90 amps witch is far more than Il want to be welding off, if I had a varyable resister it could be posable to limit the current that way and just accsept that its a 50% efficent system to only use occasonly. anyone know how posable it is to find a varyable resister capable of disepating at lest a kw of heat?
 
why? you can buy a battery already assembled cheaper than building one. jeremy has a thread on how to build a spot welder for less the $100 so that would be the way to go if you have to build it yourself by welding steel cylinders.

use some form of insulation where the parallel connection strap crosses over on the anode end of the cells. that strap can short to the case and catch the pack on fire.

if you look at the battery packs in laptops, they use a cardboard layer stuck onto the ends of the cell before they put the strap down and spot weld it. so look at a laptop battery pack to see what i am talking about. you would need to do something identical.
 
sorry I kind missed a fundemental carnt, I ment to sy that I carnt easelly/ dont want to desemble my battery in the midde of the desert to parelel it togeather as a welder. because it will be for repars of all sorts of stuff a stick welding setup would be prpreferable to a spot welder.
 
solarshift said:
if I had a varyable resister it could be posable to limit the current that way and just accsept that its a 50% efficent system to only use occasonly. anyone know how posable it is to find a varyable resister capable of disepating at lest a kw of heat?
Click to expand...
Sure. There are big wirewound pots used for dimming stage lights. But they are bigger than large hubmotors, and heavier. I have one here that I've posted pics of on ES and my old Electricle blog somewhere. It's HUGE. You don't wanna be carrying one around all the time--it'd probably be lighter (and maybe smaller!) to carry an actual real adjustable welder with you that's designed to run off DC. :lol:



@dnmun: The OP is talking about using his existing battery for welding up stuff to repair things en-route if necessary, rather than welding a new battery together.
 
dc powerd welders actully exist? is there a chance that somthing like this would be feasable?
 
Carry one 5 ah 14s lipo pack, and have a 48v welder. It will also run your bike some too.
 
im reluctent to carry another battery if I can avoid it, espechelly lipo that i have to be really carefull with. I have a farly powerfull solar charging setup for my mainbattery and I dont want to have to do fidderly charging on the road if I can avoid it. do 48v welders exist? where can I find one? would it be posable to run one on 16s LiFePo4, sitting arond 53v?
 
i dont actually own a welder but i have used a lipo battery as a welder. i use a 6s lipo pack to do some light welding with 1/16th inch electrode and 10s lipo pack with 3/32th electrode.

also if you look up doctorbass's thread posts and videos, youll see that he has welded with a a123 battery pack.
[youtube]WsD-xU4gtHM[/youtube]
 
seing doctorbass's vidio was got me thinking that somthing like this was posable, pehaps his aproch of just putting a someting of considerable resistence in the circet to limit the current could be workable with my battery.
most of thoose welders seem to be dc oultput welders, not dc in, or am I misreading descriptions? outherwise they seem to be powerd by a reletivly low (<30v) dc power sause, and directly ark of that.
 
It's cheaper to buy a welder. You can only stick weld with batteries whereas with a real welder you can choose AC or DC output, stick, tig, mig. A 220v DC stick welder can be had for $350. A near-useless 120v SMAw unit can be bought for $99 on sale sometimes.
 
I have a (2) welders in my workshop but Im locking for a simple emergeny setup for a touring mecheane that will not have acses to mains power, but will have a serioous battery bank with solid solar charging.
another option Il loock into could be pareleling my pannels into a 24volt system and welding of that, should give me about 20 amps witch is pathetic, but I shold be able to ceep a vit of volatage across the ark and make some heat, but it will be pathetic,in every way, I have welded of about 3 amps of solar pannels at 24 v befor and have been able to melt the end of a peice of wire, still thats a long way of making a uesfull weld.
I may just have to hope the frame dosent catestrophecly snap somwhere compleatly inacsesable.
 
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