mixing old and new batteries

[TobyQuest]

Arrived back to my motorhome after 4 months of no use ovwer winter and the engine battery was totally dead.
I managed to jump start it and after a couple of weeks of long journeys its charged up to 12.6volts, although im not sure how well its going to hold its charge.

I swapped it out for a new engine battery, but im wondering if its a good idea or not to now add this old engine battery in series to my existing leisure battery.
My leisure battery is a deep cycle 100ah an my engine battery is 100ah. both are lead acid.
The pro's as far as i can tell is a bigger battery bank, which would be great.
The con's i dont really understand well enough, whether it will damage my existing batteries or simply not work?

 

[Cheshirecat57]

Leisure battery and Engine Battery might both be 100ah, but one is made of chalk, the other cheese

 

[Shrimp]

Surely a leisure battery works quite differently to an engine battery-even I know that!

 

[Kannon Fodda]

Your leisure battery is usually designed for high capacity, and for discharge at moderate rates over a period of time. The engine battery doesn't normally have a big capacity, but is intended to cope with the heavy short loads of starting the motor. So they are normally quite different.

Usually if you are pairing batteries, they should be the same brand and capacity. It's recommended they are they same age / condition. A good battery can be dragged down by a bad one (when recharging the bad one tries to take energy stopping the good one getting it so resulting in undercharge and then when you are drawing energy the good one has to work too hard).

If you've killed a battery that's it, it's dead.

 

[Jim]

Surely a leisure battery works quite differently to an engine battery-even I know that!

At the budget end of some brands of Leisure batteries I’m not sure there is much difference at all. Apart from the sticker.

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[eddie]

Arrived back to my motorhome after 4 months of no use ovwer winter and the engine battery was totally dead.
I managed to jump start it and after a couple of weeks of long journeys its charged up to 12.6volts, although im not sure how well its going to hold its charge.

I swapped it out for a new engine battery, but im wondering if its a good idea or not to now add this old engine battery in series to my existing leisure battery.
My leisure battery is a deep cycle 100ah an my engine battery is 100ah. both are lead acid.
The pro's as far as i can tell is a bigger battery bank, which would be great.
The con's i dont really understand well enough, whether it will damage my existing batteries or simply not work?

If it wont’t hold its charge, it will still go flat, whether it is in the engine bay or connected to the leisure battery.

scenario ‘A’ Your engine won’t start
scenario ‘B‘ Your leisure battery will also go flat

The only place for a knackered battery is the bin.

 

[ctc]

At the budget end of some brands of Leisure batteries I’m not sure there is much difference at all. Apart from the sticker.

Exactly. People who sell expensive batteries, not necessarily better ones, will tell you leisure batteries are different and behave differently. Try A&N for battery advice.

 

[funflair]

If your leisure battery is a really good (expensive) deep cycle one then I would not do it, on the other hand if your leisure battery is cheap as chips and the old starter battery seems to be holding charge then you don't have much to loose so go for it, in my caravanning days we just fitted anything with anything and we could last a few days or even a week in a field.

If you do it just keep an eye on the battery performance and if it seems worse take the second on off and weigh it in for scrap.

Martin

 

[Pausim]

Surely a leisure battery works quite differently to an engine battery-even I know that!

Some years back the Caravan Club cut open 9 so called leisure batteries to see whether they were different from engine batteries. Of the 9 they tested only 2 were different from engine batteries so it seems the other 7 were just re-labelled cons. The article may be out of date by now but I suspect that labelling is still a very grey area.

https://www.caravanclub.co.uk/media/13871919/ccmnovtechnical.pdf?type=archive

 

[funflair]

But if you do link them in parallel not series.

Martin

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[eddie]

Some years back the Caravan Club cut open 9 so called leisure batteries to see whether they were different from engine batteries. Of the 9 they tested only 2 were different from engine batteries so it seems the other 7 were just re-labelled cons. The article may be out of date by now but I suspect that labelling is still a very grey area.

https://www.caravanclub.co.uk/media/13871919/ccmnovtechnical.pdf?type=archive

Hi Martin, the ‘knackerd’ one will only charge up to 12.6 volts after a long run

 

[Spriddler]

Some years back the Caravan Club cut open 9 so called leisure batteries to see whether they were different from engine batteries. Of the 9 they tested only 2 were different from engine batteries so it seems the other 7 were just re-labelled cons. The article may be out of date by now but I suspect that labelling is still a very grey area.

https://www.caravanclub.co.uk/media/13871919/ccmnovtechnical.pdf?type=archive

I've been using a new Bosch 'starter' type battery (the same one) for hab power in my m/h for 5 years without any issues. Whilst 'pitched', (rarely on EHU), the 12v only has to supply my water pump, loo pump, lights, fridge igniter, radio, and charge my 'phone. (I've no other 12v equipment).
No solar power or inverter and only ever charged by the vehicle's alternator whilst driving in summer and on EHU in my drive in winter months.

 

[Lenny HB]

The only place for a knackered battery is the bin.

I disagree the local Scrapie will give you £10-£15 for it.

 

[funflair]

Hi Martin, the ‘knackerd’ one will only charge up to 12.6 volts after a long run

Yes but the habitation one could be just as bad for all we know so if you add the two together and get more time off hook up it would be a bonus OR an indication that it is time to invest in good habits batteries and junk the old one, difficult call from a distance I would say.

Martin

 

[eddie]

I disagree the local Scrapie will give you £10-£15 for it.

I have a bunded battery bin with about 40 -50 batteries in. I'll sell you the lot for £25

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[Lenny HB]

I have a bunded battery bin with about 40 -50 batteries in. I'll sell you the lot for £25

If you weren't so far away I'd be straight round.

 

[eddie]

Genuinely we have to pay to get rid of the bloody things

 

[Spriddler]

I have a bunded battery bin with about 40 -50 batteries in. I'll sell you the lot for £25

I'd have thought they'd be at no charge.

 

[Richard n Ann]

We got 8 quid for our leisure battery last year ?

 

[TobyQuest]

if i pass by scrappy i will try and trade it in for a tenner. if it takes up more time its hardly worth it. i do want to dispose of it in an ethical way though.
decided it might be more trouble than its worth linking it up. if i was on a real budget and couldnt afford to buy additional batteries then i would do it.
i just like to recycle and find uses for things where possible, but alas i think not worth the risk of damaging the 2 good batteries i have which are new.

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[pappajohn]

If you weren't so far away I'd be straight round.

You'd have to fight me for them Lenny.
Our local scrapyard pay between 8 and 10 quid each.

 

[Lenny HB]

You'd have to fight me for them Lenny.
Our local scrapyard pay between 8 and 10 quid each.

Got 13 quid each for the last two I took to mine.