Mixing old and new AGM batteries

[richardeilers]

I have a 280ah domestic bank made up of three AGM batteries controlled by a smart charger. They are about 5 years old, fairly lightly used and hold their charge well. I'd like to have another 100ah or so. So, is it good idea to add a new AGM? Or should I wait until the existing ones are getting knackered and replace all in one go?

 

[NB Willawaw]

Providing they are still in good condition, you can add another battery of the Same type.

 

[VicS]

Trouble is at 5 years old the existing ones are well into their expected life span, middle aged so to speak, so will inevitably start to fail long before any new addition.

It depends how urgent it is to increase the capacity. Add the extra 100Ah if you need it but you will for some time then have one battery about 50% out of step, in terms of life span, from the others.

 

[Hugh Foulis]

there will be many on here who will tell you that the charge voltage on new batteries will be affected by the tamping wopple not being compatible with the cowie nadgers on the old batteries leading to cogitative indefference. My batteries have more varieties than Heinz, the last one I bought for the domestic system was second hand from a scrap yard.
Get yer Nike's on and just do it and enjoy your boat.

HF

 

[Plevier]

Trouble is at 5 years old the existing ones are well into their expected life span, middle aged so to speak, so will inevitably start to fail long before any new addition.

It depends how urgent it is to increase the capacity. Add the extra 100Ah if you need it but you will for some time then have one battery about 50% out of step, in terms of life span, from the others.

+1

 

[Plevier]

there will be many on here who will tell you that the charge voltage on new batteries will be affected by the tamping wopple not being compatible with the cowie nadgers on the old batteries leading to cogitative indefference. My batteries have more varieties than Heinz, the last one I bought for the domestic system was second hand from a scrap yard.
Get yer Nike's on and just do it and enjoy your boat.

HF

I bet they aren't AGM.
You can get away with a lot more with wets and I bet you don't know whether you are getting maximum performance from them anyway.

 

[NormanS]

I have a 280ah domestic bank made up of three AGM batteries controlled by a smart charger. They are about 5 years old, fairly lightly used and hold their charge well. I'd like to have another 100ah or so. So, is it good idea to add a new AGM? Or should I wait until the existing ones are getting knackered and replace all in one go?

Not a good idea. I did something similar, a few years ago, and the old ones dragged the new one down.