Battery Drain

My 5 ton only runs two batteries(m543) to keep the batteries from draining when not in use I am thinking about putting one of the the knob(dial) type disconnects on the crossover cable connecting the two batteries. If I do this, will this prevent the batteries from being drained by a short, or do I have to make the disconnect on the primary +/- cables? I know it will kill power to the master power switch.
Thanks,
James G.

It will disconnect the batteries by an open, not short. I think that should work, but you should wait for the other responces.

why not use a disconnect on the ground side? this is the safest way to isolate the batts in my opinion. just be sure to get a switch that will handle the amps.

It's okay to install the disconnect at any terminal, including the cross over to prevent draining.
However, if you put the switch in the cross over "leg", then you can still produce a nasty spark if you accidentally touch the still grounded battery's positive terminal with a wrench or something, shorting it to ground.

I'v gotto get a life......

I have not noticed battery drain in my trucks with the alternator like I do on the older trucks with the generator. The generator voltage regulator constantly draws a small current, but I was not aware of the alternator trucks doing that. I remove the battery cable from one battery in my M37 and M135/M211 trucks to prevent this. This is easy for us, a no wrench operation. We never totally tighten one terminal on anything we own. We have had instances on our own, and assisting others on vehicles with electrical fires where we had to fumble around to find a wrench to remove the battery cable to stop the fire when time is of the essence. If a starter solenoid sticks, we can quickly pull off the cable as well. We just push them down tight with a twisting motion, and if the terminal kept clean and greased, have had no connectivity problems. We use regular gun grease on all of our terminals before assembly to prevent corrosion. I have found this to be the cheapest and most expedient method of battery terminal protection over all of my years of mechanic work.
Regards Marti

Marti:
I have been using the same method of leaving one cable a little loose for safety and security, but I have not been using the grease. I had one of my cable ends arc to the battery terminal leaving a small pool of lead on top of the battery that was why I was exploring my options, when you say gun grease what are you talking about?
Thanks,
James G.

PS: My intent eventually is to install a master power switch on the ground cable to kill the electrical system, I used this approach on my 6217 and it works great, and cheap too.

How about installing a solar panel rather than a disconnect? Its better for the batteries in the long run as it helps maintain them so they last longer. Teds trucks had a NOS surplus lot of these for sale a few months ago for like $20 or so each... I picked up a spare just to have it as the replacement cost on them is something like $150. I don't know if they still have any left but it would be worth the phone call to find out...

I would try to find the cause of the drain.... 5 tons with alternators should have no drains... remember to turn your light switch off.. the dash lites can drain batteries in a week... RAM

Master switch is a good idea.. but does not fix the problem... only masks it.. RAM

battery drain

I've had the same problem in my working M35A2 since I own it. A small current draw that I cannot find. I suspect the light switch is the culprit. The disconnect between the two batteries will work. That is the way I have mine set up. As I figure at that location the switch should only have to carry 1/2 the current load. (not sure on that; I'm not an electrical engineer). But anyway mine has worked well for the past 3 years. It also is a theft prevention device when parked. It's one more hoop someone has to jump through before they go for a joy ride on "Rambo's truck". It's also a safety measure against fire in a 35+ year old truck.

RE: battery drain

Has anyone thought about putting in a main breaker like in a service entrance box would that work?

RE: battery drain

I would endorse the disconnect switch away from the battery. When batteries charge they produce hydrogen gas with is highly explosive. Avoid any sparks near the battery. If you forgot and left the heater motor on there would be a spark when you connected the battery or disconnected it. Even with a small drain there could be a small spark. I have seen a battery blow up form having a loose connection and it is not pretty. I have connected hundreds of batteries without incident but it only takes one time. This is why you should connect the pos side of jumper cables and the neg to engine ground away from the battery. Just my precautionary note. No flame to the loose battery cable guys but I like my nuts tight. A bolt cutter will make quick work of a battery cable in an emergency. That is what the fire department uses.

Teds trucks had a NOS surplus lot of these for sale a few months ago for like $20 or so each... I picked up a spare just to have it as the replacement cost on them is something like $150. I don't know if they still have any left but it would be worth the phone call to find out...

Click to expand...

Ted's does still have 24v Solargizers... I just ordered 4, to have a couple as spares. Tell him you're a Steel Soldiers member and you get the discounted price. Ted is a great guy to do business with.

Jon

but I like my nuts tight.

Click to expand...

heheheheheheheheheh

I agree you should find the cause of the drain. Since the deuce has no fusebox, the easiest way to do it is to use a milliamp meter and an assistant. Disconnect the battery at any terminal, and insert the milliamp meter there, note the reading. The assistant can watch the meter and as you disconnect various items, it will suddently drop to zero, showing you the path of the leak. One often-overlooked causes of battery discharge is simply dirty or wet batteries. The expelled electrolyte/water/dirt coating on the top of the battery creates a conductive path between the positive and negative terminals and if it is bad enough it can discharge a battery in a month or two to the point where it might not start the vehicle.

As for the disconnect: Since the negative lead on the M35 attaches to the frame right under the cab, it could be extended up into the cab to a knife switch, then back to the frame. EV (electric vehicle) enthusiasts also use them. I have not found any really "big" mad-scientist sizes, but here is one that clamps to the battery terminal itself:
http://veautomotive.com/?search=knife+switch&category=Automotive

Jon,
Are those solargizers still going for $15 each. I got some for all my stuff including the gensets. The are technically not chargers. They are designed to desulfate the plates on the batteries. I think they do trickle charge also.

Chuck

The input circuitry on the 25 amp regulator (black box on the firewall) has a "battery present" sense circuit, which is always on. It draws perhaps one milliamp, more if there is a faulty component.
This drain is always present.

I just recieved three 24v Solargizers from Karen at Ted's Trucks, still $15 and look great! I don't know that my 543 has a battry drain problem, I have always used a kill switch somewhere on the truck to ensure I have battery power when I need it and as a thieft deterrant. I have used a spare master power switch in the past with no problem at all, I usually mount it in the floor behind the drivers seat. However right now I don't have any where to work on the truck so the field expedient method is to modify the system at the battery, easy to do and undo when I get the time to do it right, thanks for all the input.
James G.

24V Battery Disconnect:

http://www.okoffroad.com/stuff-batteryswitch.htm

I have a similar issue. I just picked up a 1991 M923a2 that needs to be jumped every time to start it. yesterday I noticed the lights are very dim and the horn wont work. I just installed the P2P software (sweet little tool) so this Saturday will be playing "chasing the short". Any recommendations on a starting point?