Using a different group size battery

[Toy4x4]

About the mid 90s when the stock battery died, I was told to use a 34/78 size battery. The current (3rd) battery went out and I bought another 34/78 today as was the second.
Well, lo n behold I find out the stock size is a 25

.

Will any harm be done since the CCA are about ~100 more than the grp 25 battery? 34/78 - 880, 25 - ~750?

 

[Audi Junkie]

The more the merrier. First chance I get to re-use my oem Honda battery in another car, I'll give it away and will do whatever it takes to fit in an upsize. I'm more used to big Euro #41 batteries that can start a battleship.

 

[BarkerMan]

Your starter and electrical system will thank you, every day.

 

[Toy4x4]

Thank you, guys! Relieved!

 

[mechtech2]

More battery is mo betta.

 

[dwendt44]

No such thing as to big a battery.
Get one that will get you home on the starter motor.

 

[NYEngineer]

Originally Posted By: dwendt44
No such thing as to big a battery.
Get one that will get you home on the starter motor.

For the most part I agree, but I used to see "too big a battery" on standby generators. If you used 1300 amp 8Ds on an engine that only required 500 CA, the batteries would sulfate internally and sort of seek their own level. You want to tailor the cranking amps to the requirements set by the starter so the battery gets cycled properly and the plates get cleaned off with every crank.

 

[artificialist]

My experience shows that more CCA always leads to a longer lived battery. I sometimes see batteries with higher than factory CCA in Florida, and they hold together for 4 or 5 years, and that is quite a job in this heat.

That in mind, if you really want more life out of a car battery, mount it in the trunk, rather than underhood. I often see 6 or 7 years out of those batteries. Typically a 94R or 79 battery is used. Replacements have about 10% more CCA than factory, so by the time the battery is dead, the car is in the boneyard already.

 

[dwendt44]

The long cables would be a concern; line loss.

 

[dailydriver]

Originally Posted By: dwendt44
The long cables would be a concern; line loss.


I think that is why he was saying a humongo battery is used in these apps; to combat that loss somewhat (along with 1 guage wire).
But all of this can get real heavy, real quick.
Hence why some race car builders use it as 'ballast' over the passenger side rear wheel, if/when they are allowed to do this.

 

[artificialist]

My Saturn ION has a trunk mounted battery, but it is only a group 75. The factory battery had 600 CCA. My Carquest/Deka replacement has 690 CCA. I couldn't use anything other than a Group 75 with a sealed top because of the gas vents.

 

[johnd]

Not to muddy the water but line losses are from resistance. A bigger battery is the same voltage and the wires will have the same amount of drop for a given voltage. Only a higher voltage will overcome line loss.

 

[sprintman]

I learnt a long time ago to always fit the physically largest battery the battery tray will take. Just fitted a 670 cca battery to the Outback which is not only longer but taller as well. We run two fridges so the bigger battery is a no brainer and they last much longer as well

 

[swalve]

Originally Posted By: johnd
Not to muddy the water but line losses are from resistance. A bigger battery is the same voltage and the wires will have the same amount of drop for a given voltage. Only a higher voltage will overcome line loss.


Very true. But at the lengths we're talking about, the voltage drop can easily be overcome with bigger gauge wires. And I'd guess that a higher capacity battery would be able to overcome any added resistance.

Here's what I'm thinking, and I might be completely wrong- the starter needs a certain number of watts of energy to turn the engine and start the car. Suppose the starter draws 250 amps at 12 volts. That's 3000 watts. But if there's a 2 volt drop, the starter will need to draw 300 amps to overcome the resistance and still deliver the 3000 watts necessary to start the car. So a battery able to deliver more amps will work better.

If I'm wrong, please correct me!