Adding to Battery Bank

[chrisgee]

I have two x 170amp batteries about 2 years old working fine for the domestic side.
I want to add a third one to increase the capacity.
Does it have to be the same amperage and will it matter that it will be new whilst the other 2 are older.

Thanks for any info.

 

[affinite]

No & Yes

Chris
Conventional wisdom is the you should not add to an existing bank and that you should replace the lot. Not sure how many people have ignored that advice but I did and I dont think that it has done any harm. (so far)
If you do add a battery to the bank it does really need to be the same capacity ie 170Ahr

 

[VicS]

As above it would be preferable to renew the existing batteries at the same time so that they are all the same age but at only 2 years old not many people would go down that route I suspect, unless they could find a buyer or alternative use for the two year old ones.

Also preferable for all three to have the same Ah capacity but not vital although I would keep them similar.

More important is that the batteries should all be the same type.


There are right and wrong ways of interconnecting multiple batteries to form a single large bank . See http://www.smartgauge.co.uk/batt_con.html

 

[pvb]

The only stipulation is that all the batteries should be of the same type, ie wet, maintenance-free, AGM, gel, etc. Otherwise, it doesn't make much difference. You can mix different capacities or ages without problems.

 

[vyv_cox]

I combined my starter battery with my two domestic batteries into a single bank, replacing the former with an AGM. All three were leisure types, 110 Ah open flooded cell, the starter about four years old and the other two a year younger. The three combined lasted a further two years and then only failed due to being left for about 8 months with full solar panel charging, which dried several cells in them.