Cordless Battery Rebuild– Soldering or Spotwelding

[kgb007stb]

I’ve been looking at tools to rebuild a cordless battery pack. There are some site on the internet where a fairly good spot welder can be built for under $200 to spot weld sub C batteries. There is also lots of information on what type of soldering equipment works best.

Looking at what you have used in the past and what has worked best for you.

 

[brianl703]

A soldering gun works well when you use sub C batteries that have solder tabs on them.

 

[pair of Blazers]

there should be no need for anything bigger than a 35 or 60 watt Weller iron for those tabs.

 

[NYEngineer]

I just solder them.

 

[TooManyWheels]

Use resin core solder and flux. I have forgotten the ideal percentages, but if they are labeled for electrical work you will be fine.

 

[SZR48207]

I worked at a battery specialty store doing this on a daily basis. I mostly rebuilt Dewalt 18V batteries since we got a lot of business from construction companies.

If you can afford to build a spot welder, do it! The main advantage to using one is that you get a VERY solid weld and it puts less heat on the battery.

I asked my higher up why we didn't just solder together rechargeable packs, and the reason was that the high heat from a soldering gun could damage a cell. Something about the vent caps as well, but I don't remember the specifics anymore.

 

[kgb007stb]

Right now I am undecided which route to go. I can try tinkering with a homemade spot welder, that is the route that I am leaning at this time as I have seen that unless you are use to soldering every day, one small mistake can create a weakness in the soldering process. I do have batteries with tabs already spot welded, the spot welder would consists of a 12v charger as its power supply, a couple of capacitors, an SCR and a foot switch to activate. Don’t know how long the terminals (copper end electrodes) would last, but with a 10 to 20A power supply the capacitors should re-charge fairly quickly in between welds. I’ve been looking for a home range spot welder but could not find anything under 4,000. I think most are made for professional use, thus outside of my price range, but I sure would love to have one home.

 

[TexasHonda]

I rebuilt two batteries for my Craftsman drill/light set using sub-C nicads I bought on ebay. It is possible but a lot more tedious that I anticipated to connect all the batteries in the required order by soldering the tabs together, all the while avoiding shorting out the assy. Keep your old battery packs intact to provide a template for form you must achieve. I used masking tape to hold the batteries in place while working and once electrically complete. Adding end connectors, jumpers, etc is another chore. Both battery packs have worked well so it was worth the effort.

good luck

 

[TooManyWheels]

Soldering is not difficult. There are two principles to remember -

Don't touch the solder directly with the gun, except to tin the tip. In other words, heat the connection with the gun, melt the solder into the connection, not the tip of the gun.

Two, the parts of the connection can't move in relation to each other while the joint is hardening.

If the finished connection is silver, you have done it right, if it is grainy gray, you need to redo.

I can't see how spot welding has a lower temp than soldering, as the melting point of solder is quite low. The period of heat application may be lower with spot welding however.

 

[1sttruck]

Other soldering tips...

Hemostats make nice heat sinks, needle nose for bigger heat loads.

Use a wet sponge when soldering to keep the tip clean, and after tinning to get rid of excess solder.

Keep the tip tinned; put solder on the tip to let it flow, then clean it as noted above.

Have at least a couple of different diameters of solder available, one for 'low range' and the other for 'high range'.

Make some sort of mechanical connection and then solder that. As an example when soldering wires to a tab drill a small hole in the tab, and either put the wire thru the hole and solder or better yet put the wire thru the hole, loop it and twist it before soldering. Twist wires together before soldering.

Put the heat shrink tubing on before soldering the wires.

For higher current application crimped connectors work well provided you have good crimping tools and connectors. You shouldn't be able to pull off a crimped connector from the wire with moderate force by hand. I find small wire nuts to be easier to use and more reliable, but they take up more space and don't seem to be common outside of house wiring so they'll look hillbilly. They're great in the vehicle toolkit as they're so eay to use.

 

[tom slick]

What I found with soldering batteries is you need a large soldering iron. the typical iron used for electronics doesn't hold enough heat so when you touch it to the battery the temp. drops and you have to hold the iron on the part longer as it reheats the tip. the longer you hold it there the more heat is transferred into the battery.

I do believe soldering is a superior connection but it is certainly easier and cleaner to spot weld.