Temporary Battery

[Jriddle]

Good Morning

I have one of the 8-D batteries on my spare bus that is bad. I was looking at making a 500 mile trip with this bus. What would be the problem with putting a smaller size battery with the good 8-D for this trip?

John

[Jerry32]

No problem if it is heavy enough to crank the engine. Those *D's were for all the load that used to be in the bus so is not needed any more. Jerry

[Jriddle]

That was the answer I was expecting. The positive side of this is not paying for the expensive battery. I just don't see any down side myself but with all the experience out there I though I might be missing something.

Thanks John

[Lin]

I would say to use a group 31.  As explained numerous times here, a mismatched set may created other battery issues long term, but I do not think the bus will particularly notice.

[gus]

One 8D will crank any of these engines unless it is weak or the weather is very cold. Even one 31 will crank them.

The only reason the bus companies used two was to support the huge AC/heat fan motor.

[John316]

The only reason the bus companies used two was to support the huge AC/heat fan motor.

Another minor reason that ours uses two, is our coach is 24V. Won't work on one

[TomC]

Check with the big rig truck dealerships. I know we have new size 31's for $85.00. We sell boat loads of them. Good Luck, TomC

[Jriddle]

Engine started up with one 8-D and a group 24. I haven't started this bus since June. I just let it crank a few turns then let is set for 30 seconds and had to do that twice then bus fired right up. It took a minute to smooth out but was running. Plan trip later this week.
Thanks
John

[gus]

Good point, I have a hard time wrapping my mind around 24v systems which are a real pain. Thankfully I only have one of those now.

The 24 won't take too much of that!

[luvrbus]

Most older buses used the 2 -8D for amps because of the battery placement with 80 ft of cable not for the load the 50D alternators had no problem handling the load

 Eagle had the same load as others with a 12v system and used 3-31 batteries with short cables the batteries were close to the engine compartment not up front like a MCI and GM 

I think the load deal is a tale that started on one of the boards JMO

[Jriddle]

I think the load deal is a tale that started on one of the boards JMO

I'm sure the bus would have started with two group 24 batteries. When this bus was in service and different kinds of drivers it would pay the operators to have a large power supply for the driver that would continue cranking. Both of my buses start on very little cranking. I'm sure with the use I give my bus the smaller batteries would be fine.

John  

[gus]

Both my GM battery comps are at the rear so I assume the other GMs are also?

[Lin]

Clifford, I can only speculate on why they did it the way they did.  It has been said that they used the two 8d's as backup power for AC, heat, etc. while idling.  Now, that could make sense since they could not shut the bus down and turn that stuff off while full of passengers.  Of course, if they put it on fast idle, I would think that there would have been enough power from the alternator.  As my 5a starts just fine with two 31's, it has nothing to do with starting.  It would seem that they were putting in a nice safety factor, which would make sense to me.  You mentioned that the Eagles had three 31's.  That amounts to an 8d and a half. My guess (only a guess) is that they just put in less of a safety factor.

[luvrbus]

I think it was because the buses were all over the country not just in one area the 42 delco starter will draw a lot of amps under a load cranking a cold engine with out a block heater most buses did not have back in the day

The HVAC motors on a 24 v system will only draw 1/2 of what a 12 v system draws ,no ac or heat with out the engine running anyway so there is not need for reserve the 50D will handle the load IMO 

[Lin]

Hey Clifford, did you get my PM?