Can we run on just one battery?

[Lazy-Boy]

Just got back from lunch with a friend. It was his turn to drive so we took his sedan. Anyway, we get back in the car and he turns the ignition and we hear a loud POP. We open the hood and his battery has blown. Fortunately it didn't do any damage or make a mess. So, we'll just get a new battery and then get his car out of there on the way home today.



But now I'm thinking. If something like this happened on a diesel with two batteries, and you were out in the boonies, could the one good battery suffice to get you home?

If so what would be the procedures? Does the good battery need to be moved to the right or left side? Should I leave the bad battery in there because of some sort of chain wiring?



I don't know a whole lot about the electrical system so you'll have to bear with me.



Thanks in advance

 

[Matt S]

If it will start then yes. If it won't then no. 1st Gen's had only one battery. It was a big one but one none the less. I think they went to 2 smaller ones for $$ reasons. Just tape up the ends on the bad battery so they don't short out. If it were really cold I'm not sure you could get it started but who really knows.

 

[Joe G.]

The way these things are wired with the extra taps on the left battery that is the one you want to use if there is only one.

 

[americana]

i think you can get away with one if you live in the milder climate zones like the one here on the left coast. i think the HVAC uses only one.

 

[WOWZY]

My buddies '95 has 2 in his and had one to go bad. It was about 25F outside and it wouldn't start. It would just turn the engine over real slow.

 

[Steve St.Laurent]

I'm running on one right now. The battery on the driver's side went bad 3 days ago and the truck wouldn't start at all (just clicking). I just disconnected the negative terminal on the battery and zip tied it to the truck so it wasn't flopping around and left the positive hooked up to it. The truck fired right up - whew, I would have been stuck otherwise. My wife had already left for the day. The engine does crank over slower but it at least starts now. I'll be replacing both of them soon. I'm quite sure that if it was cold enough for the grid heaters to come on that it wouldn't work.

 

[EMDDIESEL]

I saw another TDR member using one battery with no problems. The winter is another story, but for summer you only need one.

 

[Chad Sheets]

The starters run off of 24 volts, the rest of the system is 12. Take one battery out of the equation and you only have 12 volts for starting.

Since a diesel is ignited by the heat produced during compresion, the 12 volt system wont spin the starters fast enough to allow heat to build up and stay. Everything is spinning so slow that the heat doesnt have a chance to build up before the exhaust valves open and lets it all out and more cold air comes in from the intake valves. If everything is hot/warm, you can get away with it, but like you guys said, cold climate is another ball of wax.

 

[Woodenhead]

new meening for BOMBing the CTD

Anyone ever had a battey explode when starting. A few weeks back I hit the key in the wee hrs of morning and KABOOM! Smoke starting coming out from under the hood. The bang was loud enough to get neighbours out of their houses. I opened the hood to find Both ends and the top of the battery blown open and acid all over (even grabbed the camera and took a pic). No big loss since the truck was getting a new battery before winter anyway. Sorry for getting a little off topic, just wondering if anyone else has got to clean acid and chunks of plastic from under the hood.

 

[chuck3]

Woodenhead, a friend that I work with just had the same thing happen to him, he said the neighbors came out to see what happened, said it sounded like a gun went off under the hood. Battery acid all over the eng. comp.

 

[Chad Sheets]

Just happened to the wifes Blazer 2 days ago. What a mess. Gotta love this heat

 

[Dane]

HVAC has been running only one for a while now. I'm going to run a single group 31 in pickup bed to get some weight off the front suspension and move it to the rear as soon as I need new battries. I'm sure it'll work in the warmer states, but might get a bit iffy for those folks in the great white north

 

[drag racer]

Wrong Info. Here

Originally posted by Chad Sheets

The starters run off of 24 volts, the rest of the system is 12. Take one battery out of the equation and you only have 12 volts for starting.

Since a diesel is ignited by the heat produced during compresion, the 12 volt system wont spin the starters fast enough to allow heat to build up and stay. Everything is spinning so slow that the heat doesnt have a chance to build up before the exhaust valves open and lets it all out and more cold air comes in from the intake valves. If everything is hot/warm, you can get away with it, but like you guys said, cold climate is another ball of wax.

NOT TRUE!!



The electrical system is 12V. The starter motor is designed for 12V, not 24V. 24V applied to a starter designed for 12V will fry it in short order.



When dual batteries are wired in PARALLEL (as is the case on Dodge Rams), the voltage is constant at 12V, and the amperage is additive. The engine cranks slower with one battery because you have just removed several hundred amps that used to be available to the starter to use against the huge load of turning a diesel engine over.



If dual batteries are wired in SERIES, then the amperage is constant, and the voltage additive.



Just basic DC circuit theory here.

 

[Max340]

dunno 'bout the rest of you....

Originally posted by Chad Sheets

The starters run off of 24 volts, the rest of the system is 12. Take one battery out of the equation and you only have 12 volts for starting.

Since a diesel is ignited by the heat produced during compresion, the 12 volt system wont spin the starters fast enough to allow heat to build up and stay

but my batteries are wired in parallel. Thus my entire system is 12v. My starter is not 24v, in fact, it says right on it:



Starter: Nippondenso (Denso)

Chrysler P/N: 4741012

Cummins P/N: 353888

Voltage: 12v DC

Ground: Case



So to answer the original question, if you have a battery die, do what one person already did, and pull the negative post on the dead battery. This takes the drain out of the system. Now you are able to run the truck and all systems on half the AMPS (NOT VOLTS for those new to this), which is where the difficulty comes in. Your circumstance may need the full 1500a available from the factory batteries. If so, you won't be able to start on 750a of factory battery.



Not sure where the rumor of 24v being under our hoods came from, all one needs do is look at the battery cables.



Parallel has both positive terminals on one cable, and both negative terminals on another. The batteries would lie parallel in a schematic showing them connected to the cables.



Series has the first positive connected to the truck, the other positive connected to the first battery's negative, and the negative of the second battery connected to ground. The batteries are in a long series of 6 cells and 6 cells.



If its set up in parallel, check the number of cells in one battery, multiply by 2, and you have voltage. Check the amperage on one battery, and multiply by two, and you have the amperage.



If its set up in series, add the number of cells [(6+6) x 2] and multiply by two, and you have voltage. Check the amperage of one battery and that its the amperage of the total battery.



If for some reason the system used a step up transformer to get 24v from the two 12v batteries, it would halve the amount of available amperage.

 

[Mill Rat]

Electricity 101

drag racer is correct on this, our batts. are in parallel. Voltage stays the same, current is additive. . Takes me back to the old college days in elecrticity 1.

Always wanted to make up a bumper sticker to say "Repeal Ohm's Law".

One more thing, transformers won't work with DC current, Must be AC.

 

[Steve St.Laurent]

I agree with those above - the batteries are in parallel and the starter is 12v. I checked the schematics before disconnecting the negative terminal from the one battery to make sure. My good battery was damaged some from running for a while with a bad second battery. I didn't notice it until the truck sat for a couple of days and then it would crank really slow. The good battery got a good bit of corrosion on the terminal because of the bad one - not sure how long I ran the truck with one bad cell because I drive it daily most of the time. When I've run the truck recently it cranks just like normal - it only cranks slow when it's been sitting for a day or two.



-Steve

 

[Joe G.]

I once had a boat with a Buda diesel that had a 24V starter. The boat had two 12V batteries. It's a big hairy deal to set it up to start on 24V and then charge both batteries on 12V if you don't have the US Navy solenoids and switches. These trucks are definitly 12V start and run.

 

[EMDDIESEL]

Definately a 12v starter. There is not enough compression to be a problem in our engine for a 12v starter. The person i know who is running one battery has not had any problems with the setup either.

 

[illflem]

When both the stock batteries in one of my trucks went bad after five years I borrowed one stock battery from the 3500 to put in the 2500. Both trucks started just fine for three months, it was summer though, until I had the time and money to buy four Optimas. I feel one battery is plenty if you don't need the grid heaters. BTW the 5 year old stock battery I borrowed went into a tractor that needed one, it is still cranking after 6. 5 years.



Chad, you've been hanging around too many Cat engines, most start on 24 volts, but not our Rams.

 

[Chad Sheets]

Correct-a-mundo. Thats what I get for playing on the computer with 3 hours of shut eye in 2 days.



CAT is 24, and thats where I had my wires crossed. 24 to the ECM, 24 to the starters. Thats what I am doing at work now, wireing, flashing ECM's and such... got cornfused