Multi-location battery bank

[pwillems]

Hi all,

I will be doing an upgrade of my solar and house battery bank soon which will involve 10 or 12 trojan T-105s (~300kg) up from 4. To not worsen an already slight list, I would like to put the new batteries around 2 meters away from the existing ones and want them all connected as a single large bank.

Is there anything I need to be concerned about doing this?

Thanks.

[sailormed]

Correct sizing and connecting of cables.

[rom]

Originally Posted by pwillems

Is there anything I need to be concerned about doing this?

Yes, balancing. You are going to have a hard time doing it right with such a setup. Once connected, pull say 200A from the bank and check with a clamp ammeter that each of those 10 batteries provides (close to) 20A. I suspect it will not, reconnect differently, check again.

[GordMay]

Originally Posted by rom

Yes, balancing...

Ideally, parallel battery banks require that the batteries and banks be identical.

[Nightsky]

We will be doing the same thing, doubling the size of our battery bank. Just trying to decide if separating in to two banks, a house bank and an inverter bank would be the best way to go, or to just doulble the # of batteries but separate them with the extra batteries on other side of the boat, in our case about 10' apart.

[Dockhead]

2 meters is not so bad. Use real fat cables to connect them and this should be relatively ok.


Keep in mind however that paralleling batteries is not really good and you will have balance problems, and even if they are slight ones, it will impact battery life.


I know what I'm talking about because I have two interconnected banks of 4 Trojans each, separated by about 7 meters. Connected with multiple fat cables, but life is clearly impacted -- I only get 3 or 4 years at best out of a set.


For this very reason, I am considering replacing all this mess with LiFePo4, which is compact enough that I can get the whole capacity needed into one of the two battery boxes.

[Dockhead]

Originally Posted by Nightsky

We will be doing the same thing, doubling the size of our battery bank. Just trying to decide if separating in to two banks, a house bank and an inverter bank would be the best way to go, or to just doulble the # of batteries but separate them with the extra batteries on other side of the boat, in our case about 10' apart.

With lead batteries, you're damned if you do and damned if you don't.


Separate the banks and you eliminate the balance problem, but you lose a lot of effective capacity due to Peukert.


If you can get all the batteries you need in the same place, with minimum or no paralleling, then that is the best solution, with lead batteries. If you can build up a large battery out of 2v cells, with no paralleling, that is best of all.