Do I need both batteries?

[BGPick]

Probably dumb questions but I’ve also never owned a diesel before. Does my truck actually need both batteries? Why are there two to begin with?

 

[Blue Ox]

Yes. It was standard from the factory.

Why? You're starting a diesel, man.

 

[Blue Ox]

But I'm sure the real reason for two small instead of one large is packaging. It was already an option on gassers so it was easy to just make it mandatory to get the amperage they needed.

 

[BGPick]

I figured as much. Wasn’t planning on removing one I just was curious. I’d assume these pull a lot of power on cranking and startup.

 

[Blue Ox]

Yeah, that 21.3:1 compression ratio needs a swift kick to get it spinning.

 

[shiftpro]

I don't believe the factory twin batteries have any isolation device so...
One dead or weak battery will insure... two weak/dead batteries.
Actually all you need is one weak cell to beat down both batteries.

 

[shiftpro]

Speaking of dual batteries, check this site out for info and a good source for solutions...

http://www.fridge-and-solar.net/dual_bat.htm

 

[highdesertrange]

yes, yes you need both batteries. not run as a starter and house battery but wired together in series. highdesertranger

 

[Blue Ox]

I think you meant parallel. Series would give you 24 volts.

 

[hatzie]

I think you meant parallel. Series would give you 24 volts.

It depends... The 24v CUCV has two 6TL batteries in series for NATO compliance.
The Civvy trucks have the batteries in parallel. If you upgrade from the 27MT direct drive starter to the 28MT gear reduction starter getting the largest batteries you can fit is less critical but they still need two. The diesel batteries are like tires. They need to be mated pairs. Never ever replace just one.

 

[Keith Seymore]

I think what the group here is trying to say is: diesel both batteries are wired to provide the necessary cranking force.

RPO TP2 "Auxiliary Batteries (not available on diesel) are wired with one battery for cranking, and one in reserve to run a camper or RV trailer.

This is even though the physical packaging of the batteries underhood is the same.

K

 

[v30]

it really depends on how cold it gets and the condition of your truck and the starter. I had a decent 6.2 in a 87 that came with a 4.3 and a four speed and never bothered to add the second battery, using a 6.5 starter. that was in hampton roads va and it still started during a snow storm, but the glow plugs were good and on a momentary switch. You will not get as many chances with one battery. I also recently started my international bus at the farm with a single battery after the two in it went dead.

i will most likely have two batteries in the cummins swap on my cc dually and the international from the bus in my 79 ford.

 

[PBALLARD]

I HAVE A 1986 K-30 DIRECT FROM BIG BROTHER SPORTING TWO GROUP 31 BATTERIES AND TWO 100 AMP ALTERNATORS- TRUCK RUNS ON 12 VOLTS AND STARTS ON 24 VOLTS. I NEVER RUN OUT OF ELECTRIC POWER ON WINTER STARTS. NEVER PLUG IT IN TILL IT GETS BELOW ZERO - KEEP THE DUAL BATTERIES!

 

[82sbshortbed]

No need to yell. We can hear ya just fine.

 

[highdesertrange]

oops blue ox is right I meant wired in parallel. not in a series. this is for the civilian trucks. as pointed out the military trunks have a mixed system. highdesertranger