Soldering Battery Cables

[Craig Illman]

In one of Mike Vaccaro's project descriptions he noted:

"The best way to ensure a proper, mechanically sound connection is to "crimp for strength" and "solder for juice," finishing all connections with a quality, glue-lined shrink-wrap."

What technique do people use for soldering large gauge wire to lugs? My propane torch seems a bit excessive, on one of my tests a lot of heat wicked up the cable. I'm a bit nervous about using the torch on the boat while trying to get the optimal length.

Craig Illman

[Footloose]

Craig,

You can use a propane torch to solder the cables but you have to be careful not to over heat things.  Hold the edge of the flame at the tip of the wire while at the same time holding the solder on the wire next to the insulation.  As the wire becomes hot, the solder will melt and be drawn toward the hotter tip.  Remove the heat from the tip of the wire soon after the solder begins to melt or you can easily overheat it.  Don't over do it with the solder either.  Experiment on some scrap if you have it.  I used this technique and haven't had any problems.  If you need to you can put a small piece of metal behind where you are working which will act as a heat shield.  Also it is probally a good idea to remove the batteries from the area you are working and watch where your flame is pointing behind your work for flamable stuff.

This upgrade reduces the resistance in the charging/starting circuit.  At the amperage that our starters draw and upgraded alternators put out, a small amout of resistance can be quite significant.  You will notice an improvement right away.

[Jeff McKinney]

Dave,

Excellent safety pointer about open flames & being near the batteries.

Remember class, they vent HYDROGEN which is EXTREMELY flammable.

Remember the Hindenberg!!

[Ron Hill]

Craig : I've soldered most of my projects like cables with a BIG Weller D550 electric gun.
You can also use a torch, but a small one.  You should be using marine grade TINNED wire, so the solder will flow easily.

Hydrogen is lighter than air so if you open the battery compartment it should dissipate.  Also hydrogen is generated while you're charging the batteries -- I wouldn't recommend to anyone to be charging while soldering!!  

[Craig Illman]

Thanks, I think I'll try another experiment, using needle-nose visegrips as a heatsink opposite the lug. I think I'll also do it off the boat, after carefully measuring with some smaller wire or something else as a template.

I'm running some #1 & #2 from the battery bank directly back to the engine compartment to support a new 80A alternator and a larger gauge starter path. I've gotten too many good ideas from the projects pages and forum threads. The PO (or PPO) had added a start battery and an echo charger, they just didn't beef up any of the existing wiring. The start battery wiring is #1, extended back to the original wiring in the standard battery box. I'm going to run #1 (POS & NEG) back to the engine, as well as run a #2 from the alternator back to the house bank. I'm changing the panel 1-2-all to just an on/off for the house loads. I'm also adding 150A surface mount breakers at each bank to safely isolate the batteries close to the source. Lastly, I'm adding an emergency on/off to combine the start/house banks under the head sink.  I'll probably go with the 4-6v house bank and new shore power charger when I add the refrigeration.  I've already installed a Link20 a couple weeks ago. I got a bit concerned when I found my diesel cabn heater was wired directly to the house bank and not fused!

- Craig Illman