Can I add more batteries now?

[DaveKdot]

About 18 mo. ago the former owner replaced the four T-105 batteries before he placed the boat on the hard and put it up for sale. Even while on the hard solar panels with a charge controller kept the charge level up. For the last six mo. the boat has been docked with shore power keeping the batteries at full charge. I have heard that you should not add fresh batteries to an existing bank. What will happen if I go ahead and add two more? I expect the existing four to last for years and don't want to wait until they fail to increase the capacity and I don't want to kill them either. I hope it makes a difference that the existing four have been through only a few deep discharge cycles.

[Stu Jackson]

Just do it. Not an issue based on your description.

[john61ct]

Yes not a sin, just an economic decision.

Worst case it is as if you are paying new price for adding secondhand batteries same condition as the existing ones.

Compared to selling off the existing ones and replacing with all new.

[Phil70]

As has been said, just do it, it'll be OK
Phil

[ontherocks83]

18 months and been mostly on a charger the whole time. I would add more without worry if it were my boat. If you want to be really thorough do an equalizing charge on your existing bank just before adding the new batteries.

[Ivansgarage]

Originally Posted by DaveKdot

About 18 mo. ago the former owner replaced the four T-105 batteries before he placed the boat on the hard and put it up for sale. Even while on the hard solar panels with a charge controller kept the charge level up. For the last six mo. the boat has been docked with shore power keeping the batteries at full charge. I have heard that you should not add fresh batteries to an existing bank. What will happen if I go ahead and add two more? I expect the existing four to last for years and don't want to wait until they fail to increase the capacity and I don't want to kill them either. I hope it makes a difference that the existing four have been through only a few deep discharge cycles.

They are the same kind and size you should be ok.
Never mix batteries in a bank.

[john61ct]

Never say never, it's just less efficient. Up to the owner and situation, weighing the pro's and con's