Mixing Battery ages ?

[xeitosaphil]

In an effort to off-set battery consumption I am trying to acquire an aging 110ah battery which still has some life in it, to add to my 3-4 year old bank of two 110Ah (posted recently in the wanted section).

What would be the possible consequences of buying a new battery and adding it to a 3-4 year old battery bank? I thought that the old ones would possibly pull the new one down, but what actual physical effect would this have.
I have an engine start battery which is of the same age as the 110Ah bank but unfortunately it is 90Ah so I assume unsuitable to parallel with two 110Ah.

I know that at some stage in the future I will have to replace the two originals 110Ah and could wait till then but hopefully it may be a while, so thought a reasonably good discarded one from a bank renewal may fill the post until I have to replace all mine.

Any thoughts on the effects of possible addition of a new added 110Ah.to an older bank of 2 x 110A.

 

[makingplansfor]

I cannot help with the technical aspects of the question but I am waiting for new batteries to replace 2 off 110Ah which should be delivered today. I am changing as I have noticed that they don't hold up for as long as they used to and I dont want to take any risks for the family holiday later this month. You would be very welcome to them both if you collect from Plymouth - I will be taking them to the tip anyway.

 

[sailaboutvic]

I add three new battery's to two old ones ( two years old ) I had the old once tested first , so far all Been ok it now two years on , I know people will say don't add new one to old one , but I think if your old one are still good and holding charge there wouldn't be much of a problem , just make sure there are all the same type .

I am sure someone will correct me on this .

www.dufour385.webs.com

 

[Little Five]

I am no expert on batteries but i believe the accepted wisdom is never to mix old and new batteries or to have different amp hour ratings

 

[Spi D]

It depends, IMO, on more facts.

If your charging setup supports individual charging of more batteries/banks, you face different challenges than those who combine more batteries and expect the charger to treat them as inviduals (ie impossible).

If mixing batteries into one or more banks they will interfere and confuse the charger. May work, but chances are that it will be less than good.

Best advice is to ensure that batteries on same bank are identical.

 

[xeitosaphil]

I cannot help with the technical aspects of the question but I am waiting for new batteries to replace 2 off 110Ah which should be delivered today. I am changing as I have noticed that they don't hold up for as long as they used to and I dont want to take any risks for the family holiday later this month. You would be very welcome to them both if you collect from Plymouth - I will be taking them to the tip anyway.

Hi makingplansfor that is a very kind offer and I would be most grateful for them. Have PM you for more details

 

[xeitosaphil]

I add three new battery's to two old ones ( two years old ) I had the old once tested first , so far all Been ok it now two years on , I know people will say don't add new one to old one , but I think if your old one are still good and holding charge there wouldn't be much of a problem , just make sure there are all the same type .

I am sure someone will correct me on this .

www.dufour385.webs.com

Thats very interesting and I will bare it in mind, thanks for the reply

 

[xeitosaphil]

It depends, IMO, on more facts.

If your charging setup supports individual charging of more batteries/banks, you face different challenges than those who combine more batteries and expect the charger to treat them as inviduals (ie impossible).

If mixing batteries into one or more banks they will interfere and confuse the charger. May work, but chances are that it will be less than good.

Best advice is to ensure that batteries on same bank are identical.

Thanks little five and Spi D for your input - All batteries will be the same type and amp hour rating, and wired in parallel charge by either a Adverc charging system and VSR, or a CTEK M300 25amp 8 stage inteligent shore based charger, so I assume all will be ok?

 

[VicS]

Thanks little five and Spi D for your input - All batteries will be the same type and amp hour rating, and wired in parallel charge by either a Adverc charging system and VSR, or a CTEK M300 25amp 8 stage intelligent shore based charger, so I assume all will be ok?

There is always a risk that an old one will stat to fail before the others and your battery bank as a whole will suffer until you realise what has happened and disconnect the dodgy one.

That said even three brand new batteries will probably start to deteriorate at different ages.

 

[Spi D]

Intelligent chargers will handle without any issues if it detects the battery banks correctly. This is why batteries on same bank should be identical.. avoid confusing the 'intelligence' by combining batteries of different type/size.

A matter of layout, really.

Note: Intelligent chargers run a schedule to get through all stages, commonly some 8-10 hours in all. Allow it to complete the run in order to make use of the built-in genious.

 

[noelex]

Mixing old and new batteries is not optimum, but can be satisfactory in some circumstances.
The main risk is the lifespan of the new battery will be shorter than ideal.

In some/most cases the overall battery cost will be lower driving the existing batteries harder (say using 70% discharge instead of 50%) and then replacing the bank with 3 new matched batteries, when the two batteries die.

Given the low cost of single 110 AHr battery I don't think the difference between the two approaches is too critical.

For long distance cruising boat a bank of two house batteries gives more versatility, but few boats fit this.

 

[xeitosaphil]

There is always a risk that an old one will stat to fail before the others and your battery bank as a whole will suffer until you realise what has happened and disconnect the dodgy one.

That said even three brand new batteries will probably start to deteriorate at different ages.

Thanks for that Vic,
Perhaps I will monitor the old ones for a while to see what sort of self discharge they have, to get an idea of how compatible they are with my own before connecting them up.
As I said mine are 3-4 years old so must have started deteriorating a bit so I will have to be diligent in my monitoring of them all.

 

[CAPTAIN FANTASTIC]

For as long as the "old" batteries are performing ok, there is not a problem in mixing old with new batteries; in theory the old will bring the new batteries down, but in practise it will not happen. Naturally, you will need to test the batteries individually each season and all things being equal, the old batteries should expire first, however, the way the old batteries have been used in the past and the quality will determine the rate of decline.

 

[Little Five]

Mixing old and new batteries is not optimum, but can be satisfactory in some circumstances.
The main risk is the lifespan of the new battery will be shorter than ideal.

In some/most cases the overall battery cost will be lower driving the existing batteries harder (say using 70% discharge instead of 50%) and then replacing the bank with 3 new matched batteries, when the two batteries die.

Given the low cost of single 110 AHr battery I don't think the difference between the two approaches is too critical.


For long distance cruising boat a bank of two house batteries gives more versatility, but few boats fit this.

The Rival 38 which i sailed/lived on for 6 months had 4 x 110 amp hours each domestic batteries and 2 starter batteries of 100 amp hours each. We had to run the engine to top up the batteries every 2nd day. The fridge was the main culprit but to be fair we were in the tropics and cold beer is a must.