Can I mix group 24 and group 27 for coach batteries?

[Paradox998]

I have a 2019 25v Chateau. The house batteries have died and I am no where near a dealer. The battery box is very tight with two group 27 batteries. Can a replace the 27 batteries with one group 24 and one group 27? This would buy me an inch and a half in the battery box and I would have the same capacity (320 reserve hours). The original battery are 160's and the new ones would be 180 and 140.


Any problems with mixing these?


Thanks!

[16ACE27]

Yep, The 24 will discharge faster than the 27 and drag it down. In the short term it will work but in the long term the 27 will have a shorter life.

[Peterrrr]

Technically yes, but you also would have to make sure that they are the same type of battery, the manufacturer is the same, and they are roughly the same age. If your going to go with two new batteries and you say you are not near a dealer, you could always go with Walmart or Cosco deep/cycle or marine batteries. With a 2019 there could be something wrong with your charger if your batteries are toast.

[Bob Denman]

It's sort of like a strange team of horses...
You might be able to hook a shetland pony, and a Clydesdale: to the same Beer wagon...

But the whole thing will work better; if both sides are pulling an equal part of the load!

[petefoss]

I beg to differ but in parallel you would be fine with different size batteries. As soon as you connect them they are at the voltage. As you draw from them the current with split automatically so they drain together.

In series two different capacities would be very bad but in parallel they should be fine.

[16ACE27]

Originally Posted by petefoss

I beg to differ but in parallel you would be fine with different size batteries. As soon as you connect them they are at the voltage. As you draw from them the current with split automatically so they drain together.

In series two different capacities would be very bad but in parallel they should be fine.

They may be "at" the same voltage since they are physically connected in parallel, but it doesn't mean they are generating the same voltage, or that he current drawn from each battery will be proportionate to its capacity, nor charge proportionately to its capacity. Putting two different capacity batteries in parallel is not standard or good practice for a reason.

[Hooligan2]

This tutorial says NO..
"Before we move on we need to point out some assumptions we have made. We assume when you plan to connect your batteries in parallel, you are using the same type, age and size of batteries. For example you would not connect a deep cycle battery with a starting battery. Or connect 2 old batteries with 2 brand spanking new batteries. Or connect a group 24 with a group 27 and group 31 sized battery."

https://www.impactbattery.com/blog/t...s-in-parallel/

[SANDDOG]

Originally Posted by 16ACE27

They may be "at" the same voltage since they are physically connected in parallel, but it doesn't mean they are generating the same voltage, or that he current drawn from each battery will be proportionate to its capacity, nor charge proportionately to its capacity. Putting two different capacity batteries in parallel is not standard or good practice for a reason.

Well said and you are spot on in the battery world you are either a slave battery or the master battery they really need to be matched but temporarily you’ll get away with it

[Sweetbriar]

Mixing sizes will work but will be very inefficient. It's a bit of a weakest link in the chain item. The group 27 will end up charging the smaller capacity group 24 as you use energy. The resulting capacity will be somewhere between the two but not the sum of the two.

Any chance a pair of 6VDC GC2 batteries will fit? 10 1/4" (L) x 7 1/8" (W) x 10 7/8" (H). You'll get a much longer service life and a battery that is a much more forgiving to being deeply discharged than group 24 or 27 when used to support the house side of the coach.