Nearly had a electrical fire on "Rustless Money Pit" today.

[Gary LaBombard]

Hey guys, I lost my post I was writting, darn.  Anyhow here is as short a story as possible maybe you can help me with.  I have been starting up my bus 2-3 times per week, letting her run about 15 minutes each time to test all systems I have installed, (new air Compressor and all air system, New power steering and testing all new dash gages. 

Anyhow today I attempted to start up bus twice.  I usually let her turn over 5-8 seconds I would say, I know these big girls pull a lot of current.  The second attempt made me open up my battery compartment and I found that my cable for the negative ground outside sheathing nearly all melted off.  The cable was real hot but the positive cable was not.  The positive cable was slightly warm.  After investigating the best I can here is what I come up with and hopefully you can see in my photos here what I did and what I am talking about.

1) I am using (2) 31 batteries hooked in parallel.  The negative cable is .300 thick in diameter and the outer sheathing looks almost like plastic.  Not sure but do not believe it to be Rubber.

2) The positive cable (red connectors) is .500 in diameter over bare wires and has a heavy duty outer casing and this cable was barely warm and showed no signs of overheating in any way.

3) I believe the Negative cable to be too small in diameter, it is .200 smaller than positive cable and the connectors are only 1/4" connections.  I did not realize the negative cable could heat up like this, I have a lot lot to learn for sure.  This has opened my eyes.  Now look at the photos closely, I believe I have everything hooked up to be parallel, please trace for me if possible.  I need to fix this asap. If you have any questions please post them here and I will answer to the best of my ability.  I am sending photos of positive and negative bus bar connections for all cables, photos of both batteries connected together, and photos of the melted negative cable.   I had not looked in this compartment in weeks so I have no idea when this problem started to exist but am so glad it was not on my test run on the road. 

Please, No negative comments, I really good feedback to correct any problems I may have caused.
Thanks ahead of time.

[Gary LaBombard]

BCM would not let me post rest of photos, hope I can here.

[Iceni John]

4/0, and only 4/0, should be the gauge of all high-current cables, if only to minimize voltage drop under load.   Heck, I would use thicker if they were commonly available!   Take this as a good opportunity to completely reevaluate all your cables, and replace any if in doubt.   A small handheld IR thermometer is useful for lots of things in a bus (wheel hubs, brakes, tires, exhaust manifolds, etc.), but I also use mine to check for overheating cables or connectors  -  thankfully nothing found so far.   And crimp the cable lugs on with a proper circumferential crimper to ensure maximum strand-to-lug bonding (you need a "gas-tight" connection):  don't use those cheapo hammer-type crimpers or solder the joints!

John

[MagnoliaBus]

On picture 679, the black cable routed over the red one near the battery post is a time bomb waiting to happen. Imagine the insulation melting near the positive post...
Move that negative cable away. You could route it to the left side of the battery bank, not over it.

Regards,

Denis

[bigred]

I would replace with 4/0 welding cable. Not only easier to work with but if my memory serves me the amp rating is a bit higher .DLO would be even better but a lot harder to find.

[richard5933]

I agree. That negative cable was way too small for the current it needed to carry.

Point of information...Despite commonly thought to be otherwise, current flows in a DC circuit from negative to positive. Probably why the manual for my charger tells you to place the temp sensor on the negative terminal of the battery.

I also agree that you should re-route the negative cable away from the positive to minimize problems. The positive cables also need to be checked to be sure that there are no points of contact with metal body parts that could wear through the insulation and cause a short to ground. A length of heater hose can serve as extra insulation for times with it's necessary to route cables near potential rub points.

[buswarrior]

They told you.

You can purchase big @$# 4/0 cable from proper electric cable supply companies, and the proper fittings.

Pay someone with the expensive crimping tool to whip off your lengths for you.

You can also consider marine tinned cabling, as well as the welding style cable.

You can buy all black cable and mark it strategically with red tape, and red heat shrink for their ends.
Black heat shrink for the negative. This stuff is expensive, and having two different spools with left overs gets spendy...

Happy coaching!
Buswarrior

[chessie4905]

Negative cable way too small, and should be as large as start cable. Your way of connecting battery grounds to each other is totally unsatisfactory. Wingnut connections totally inadequate for starting system. Should be battery post connected. Probably overheated when wingnut/s connection deteriorated over time. The amount of current they had to pass caused heating and degradation of connections

[luvrbus]

Gary,buy military grade battery terminals don't use the cheapo battery terminals going from post to a stud type blade.Miltray grade will cost you 6 to 8 bucks ea at Del City   

[Utahclaimjumper]

 You should also NOT be starting the coach 2-3 times per week for ANY reason,,and should not be running it for ONLY 10-15 minutes.. This action does more harm that good.>>>Dan

[Gary LaBombard]

Getting great info here and very much appreciated.  Dan, I have to disagree with not starting up my bus for a few minutes at a time right now anyhow, I have done so much to bus since starting my conversion and I need to test all outlets to be sure they are working to satisfy me, like this battery cable wiring for instance.  I could have burned up by bus on the road and 15 years down the tube.  I know starting up the bus for a short period is not good, but I made a choice for my testing reason only but will do 1 per week to continue until I start driving it.  Most testing is completed now anyhow.  

Cliff, as usual, thanks also, I will try to research (Del City).  I will have all my NEW cables crimped as suggested, what a journey this has been.  I hope my wife's next husband appreciates all I have done.  Only kidding of course.

Big Red, I do not know what .DLO stands for?

Found website for Del City as suggested by Cliff.  Here it is for anyone else interested.
https://www.delcity.net/store/Battery-Cables-&-Accessories/][url]https://www.delcity.net/store/Battery-Cables-&-Accessories/[/url]

[kyle4501]

Welding cable insulation is not as durable as the marine boat cable. Welding cable insulation is designed for a very different purpose than the automotive environment. I've seen several instances where the welding cable insulation dry rotted & fell off.

I replaced all of my battery cables when I relocated my batteries. I bought a hydraulic crimper and used the good tinned lugs & tinned copper 4/0 boat cable.

What I got off eBay --
-Tin Plated Heavy Duty FTZ Power Lugs
-PER-213 & 211 Red & Black Terminal Junction Block Insulated Battery 3/8 Stud
-75908-BX Cole Hersee - Master Disconnect Switch, 2000A
-Military Battery Terminals - Heavy Duty Battery Terminals For Off-Road Vehicles
-Pro Start T100EX Brass Battery Post Connector Grease Nipple Kit MACK 8993743X303 (my favorite)

from iboats.com --
- 4/0 tinned marine cable
-colored heat shrink

Call me if you want to discuss. . . .

[Iceni John]

Dan, I have to disagree with not starting up my bus for a few minutes at a time right now anyhow, I have done so much to bus since starting my conversion and I need to test all outlets to be sure they are working to satisfy me, like this battery cable wiring for instance.  I could have burned up by bus on the road and 15 years down the tube.  I know starting up the bus for a short period is not good, but I made a choice for my testing reason only but will do 1 per week to continue until I start driving it.  Most testing is completed now anyhow.  

Can you use another battery, perhaps an old junk battery at the end of its useful life, just for testing?   I'm using my old 8D start batteries as temporary house batteries now for this exact reason, so I can test systems without using the real stuff.   Anything you can do to avoid starting the engine is worth it  -  an engine experiences more wear and tear in the first few seconds than during a long run (assuming it doesn't overheat or run out of oil or whatever!), so don't start it unless you'll drive it 20 miles or so to get it fully up to temperature.   It's better to let an engine sit than to start it too often.

FYI, US-made 4/0 welding cable is available off eBay for less than $4 a foot, in red and black.   I also protect every positive cable inside split-loom or conduit, and I always use extra sheathing wherever any cables pass over or through anything else, then ziptie everything to prevent any movement at all.

John 

[kyle4501]

I have added a way to air up mine with my shop air compressor. It is lots easier to hear leaks when the big noisy thing in the back is quiet. 

[TomC]

My bus is 12v. It has one set of 4-0 cables per battery-so 2 positive and 2 negative individual battery cables. You can continue to use that small negative cable, but double up on it. Good Luck, TomC