Same size battery? (1 Viewer)

[Happy1]

Trying to add a second leisure battery, the existing one is 85 amp, is it ok to add a 100 amp battery?
Any advantage or disadvantage?
From my wallets point of view I already have the 100!!

 

[pappajohn]

Add any size you like.
The charger and 12v system only see them as one battery of combined capacity.
In this instance one 185ah battery.
Age of battery does matter though.
Ideally they should all be around the same age....within a year or so if they've been looked after and not repeatedly over discharged.
The only disadvantage is the higher the combined capacity, the longer the charge time.

 

[Happy1]

Thanks papajohn, is it ok to mix AGM and gel? The charging rates seem similar depending on which suppliers fact sheet you read.

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[Lenny HB]

Thanks papajohn, is it ok to mix AGM and gel? The charging rates seem similar depending on which suppliers fact sheet you read.

No, AGM require the absorption charge to be 14.7v and once up to that needs to be held for 4 hours for a full charge, Gel the absorption charge is 14.4v and needs to be held at that for at least 8 hours for a full charge.
A Gel on AGM settings will shorten it's life, AGM on Gel settings will never receive a full charge and you will be lucky if it lasts much more than a year. AGM's are a bit of a disarster for leisure use, Hymer group have been fitting them for a few years, they are holding up a bit better since they started fitting proper AGM chargers but still loads of reports on German forums of them failing. I would steer well clear of AGM's.

 

[Pausim]

I was told when I purchased one of my motorhomes that both batteries needed to be of the same size, type and age. The advice of one battery manufacturer can be found here
Go to pages 20-21

 

[Happy1]

thanks pausim, it also recommends the biggest single battery that fits, something i had not thought about and have plenty of space.

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[TerryL]

Ideally you should fit two batteries of the same age and type, and as big a capacity that will fit. But as papajohn says, no problem in what you're doing, but don't mix types.

 

[denisejoe]

I thought if you had 1x80 +1x100 you would 160 amps available.
Ready to be shot down though

Joe

 

[pappajohn]

I was told when I purchased one of my motorhomes that both batteries needed to be of the same size, type and age. The advice of one battery manufacturer can be found here
Go to pages 20-21

Nowhere does it state 'same size'

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[Pausim]

Nowhere does it state 'same size'

View attachment 170243

If you read what I wrote I didn't say the advice about same size batteries came from the battery manufacturer, I clearly only attributed this to the seller of the motorhome. Indeed I did not claim to qoute the battery manufacturer at all, I simply provided a link that I thought might be helpful.

 

[pappajohn]

My apologies, obviously misread.

 

[vwalan]

If you read what I wrote I didn't say the advice about same size batteries came from the battery manufacturer, I clearly only attributed this to the seller of the motorhome. Indeed I did not claim to qoute the battery manufacturer at all, I simply provided a link that I thought might be helpful.

and banner are a battery i think anyone should avoid . they seem to just live a little bit longer than the warranty then let you down .
having a garage for years and hearing others talk i dont rate them at all.

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[pappajohn]

I thought if you had 1x80 +1x100 you would 160 amps available.
Ready to be shot down though

Joe

160 Obviously a typo, yes one battery of 180ah.

 

[denisejoe]

No as big battery will only act as 80 ah

https://www.optimabatteries.com/en-us/experience/2014/04/can-i-connect-dissimilar-batteries-parallel

 

[BMM]

I have 2 leisure batteries and room for a 3rd, last week I asked exactly the same question to my mechanic and he insisted all 3 need to be the same. I'm going to buy 3 new ones just to be sure

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[Pausim]

My apologies, obviously misread.

Appreciated, no problem.

 

[pappajohn]

No as big battery will only act as 80 ah

https://www.optimabatteries.com/en-us/experience/2014/04/can-i-connect-dissimilar-batteries-parallel

Sorry, but incorrect.
The two batteries will become one 180ah.
The 100ah will still charge to 100amp capacity and the 80ah will still charge to 80ah unless one is 'past its best'
If the older 80ah has lost 10% of its capacity then they will become a combined 172ah