Does second leisure battery have to be new one?

[Maddogontour]

i am considering installing a second leisure battery and I know that in principle I should replace the original one at the same time so that they are both new and well matched. However I was wondering if I could get away with only buying one battery and retain the original? It is a Varta Professional Dual Purpose AGM LA95 (95 amp hour), which seems to be quite a decent one. The motorhome is a 2016 model
Any advice/ guidance much appreciated
Thanks

 

[dixieland]

We had our new van in 2011 and added a second leisure battery 2 years later. The pair worked well until this year when we replaced both.

 

[Maddogontour]

Sounds promising then....
Thanks

 

[Bryden]

We did the same as Dixieland last year and have had no problems so far

 

[Lenny HB]

Probably ok at only 2 years old.

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[Maddogontour]

Cheers

 

[Minxy]

We did similar in a previous MH without a problem, they were also different sizes (power).

 

[bigtwin]

We added a new battery to an existing 4 year old battery 8 years ago and they’re both still fine.
I’m starting to wonder how much longer they are going to last - certainly outlasting my original expectations.

Ian

 

[Jim]

I've ignored most of the good advice about batteries over the years.

I've mixed gels and lead acid batteries They worked OK for years
I've linked new batteries to old ones, no problem at all.
I've fitted additional batteries "too Far" from the existing ones; they worked well.

Advice I did take . "get yourself some AGMs" . they were rubbish. Should have ignored that too.

 

[Maddogontour]

Thanks
I suspected that might be the case
Oh.... what is an AGM anyway?

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[Liverpoollass]

Thanks
I suspected that might be the case
Oh.... what is an AGM anyway?

Ditto!

 

[Pausim]

AGM, Annual General Meeting. Once a year the battery cells have a meeting and decide whether to pack up and fail or go on for another year.

 

[mike mcglynn]

Ditto!

Hello, An AGM battery is absorbing glass mat : instead of lead plates they are supposed to be more heavy duty as in starting /stopping technology I have two one in the van as an engine battery and one in our car and they are a lot more expensive than the usual Lead /acid type.Only time will tell

 

[Lenny HB]

AGM, Annual General Meeting. Once a year the battery cells have a meeting and decide whether to pack up and fail or go on for another year.

Funny but unfortunately very true, in my last van they lasted 18 months. New van I didn't risk it got rid of the AGM and fitted 3 Gels.

 

[bigtwin]

Hello, An AGM battery is absorbing glass mat : instead of lead plates they are supposed to be more heavy duty as in starting /stopping technology I have two one in the van as an engine battery and one in our car and they are a lot more expensive than the usual Lead /acid type.Only time will tell

They still have lead plates. It’s just the medium used for the acid that is different.

Ian

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[chatteris]

if you mixed battery capacity say 90ah and 100ah and used the positive on one battery and the negative from the other what would the theoretical ah be

 

[funflair]

if you mixed battery capacity say 90ah and 100ah and used the positive on one battery and the negative from the other what would the theoretical ah be

The capacity will be the addition of the two batteries.

Martin

 

[two]

I have done both but believe that it’s better to replace batteries together. It would ‘work’ if you didn’t, but you could be unlucky and find that the new one fails prematurely when the older one dies (they often go together).

A charger (or solar controller) is going to be confused by the presence of mismatched batteries and may not provide the best charging regime, so I think it’s false economy to mix new and old.

 

[Jim]

I have done both but believe that it’s better to replace batteries together.

It's what everybody says. But in my real world experience its a waste.

 

[two]

The capacity will be the addition of the two batteries.

Aside from the fact that capacity reduces with age, I’m sure that the capacity of two mis-matched batteries would be less than the sum of the two. I suggest you assume only twice the capacity of the smaller one because the strong one will become ineffective when the weaker one is exhausted.

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[jezport]

As long as the older battery is still performing as new and the capacity and battery type is the same you should be OK.

 

[bigtwin]

A charger (or solar controller) is going to be confused by the presence of mismatched batteries and may not provide the best charging regime, so I think it’s false economy to mix new and old.

On what do you base that?

The charger will simply see an impedance that changes with charge state irrespective of how many batteries are involved.

Ian

 

[bigtwin]

Aside from the fact that capacity reduces with age, I’m sure that the capacity of two mis-matched batteries would be less than the sum of the two. I suggest you assume only twice the capacity of the smaller one because the strong one will become ineffective when the weaker one is exhausted.

Again, on what do base that thinking?

Two batteries are just the same as two water tanks connected together. The capacity of two water tanks won’t magically reduce because you connect them together!

Ian

 

[chaser]

It's what everybody says. But in my real world experience its a waste.

all my tractors run on batterys that other people have thrown out because of matching them or some other reason.

 

[Geo]

Nooooooooooooooooooooooooooooooooo!!!!!
Your all going to Die

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[two]

On what do you base that?

The charger will simply see an impedance that changes with charge state irrespective of how many batteries are involved.

Ian

My thoughts are that it will not see the individual impedances and hence know their actual state of charge. Only one charging pattern can be issued, so they cannot respect the needs of mixed sets (wet & gel, say) either.

 

[bigtwin]

My thoughts are that it will not see the individual impedances and hence know their actual state of charge. Only one charging pattern can be issued, so they cannot respect the needs of mixed sets (wet & gel, say) either.

Of course they won’t, they’re in parallel.

And yes, the charging regime for different battery types are different.

Ian

 

[Minxy]

Only one charging pattern can be issued, so they cannot respect the needs of mixed sets (wet & gel, say) either.

... but you should NOT be using lead acid and gel leisure batteries together anyway! Why on earth would you????

 

[two]

see post #9

 

[Minxy]

Only one charging pattern can be issued, so they cannot respect the needs of mixed sets (wet & gel, say) either.

... but you should NOT be using lead acid and gel leisure batteries together anyway! Why on earth would you????

see post #9

Yes I read that earlier by Jim and whilst they may work without an issue the charging regime for gel is different to lead-acid so the gel is unlikely to ever be fully charged. I would imagine that Jim never let his get below 50% discharge though ('cause he's a sensible bloke! ) but if you did so, whilst the gel will be able to cope and recover, the lead acid may not do so well over time.

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