[downeast450]

I have managed to securely locate three identical group 27 batteries in our I-28. That gives us 345 [email protected] which has been all we need with a comfortable margin. At the same time I have made access to the aft end of the engine difficult. I am considering replacing one of the group 27 batteries with a group 26 that will fit under the floorboards in the bilge. That would give me the access to the engine space I need in the lazarette. The group 26 would have 525 CCA and would be dedicated as the A-4s starting battery.

What are the consequences of this change I need to anticipate?

Down

 

[TakeFive]

Depends on how you have them connected. With three identical (same model and same date of manufacture), you could wire all three in parallel with no selector. This could prolong their life by minimizing the depth of discharge on all of theme, but if one goes bad it could pull down the others.

But if one of the batteries is different (especially if it is a starting battery), you will need a selector of some type and/or multi-bank charger, and all the complexity and risk that comes with that. Maybe that's what you have already, if so no biggie.

 

[Faster]

We have a bank of 4 T-105s, plus a 'starting battery', all charging sources go to the main bank, with a Blue Seas ACR between that and the starting battery. It's been working very well. The ACR is a reasonably priced addition to that kind of system and not difficult to install.

 

[eherlihy]

I have managed to securely locate three identical group 27 batteries in our I-28. That gives us 345 [email protected] which has been all we need with a comfortable margin. At the same time I have made access to the aft end of the engine difficult. I am considering replacing one of the group 27 batteries with a group 26 that will fit under the floorboards in the bilge. That would give me the access to the engine space I need in the lazarette. The group 26 would have 525 CCA and would be dedicated as the A-4s starting battery.

What are the consequences of this change I need to anticipate?

Down

Similar to Faster's suggestion, I would connect all three identical batteries in parallel to have a large house bank. Remember to have the + and - at opposite ends of the bank. This large bank would be Bank 1.

I would add the group 26 as a dedicated start battery as Bank 2. I would connect it to the house bank by either a Xantrex Echo Charge or a Blue Sea Systems ACR. I would use an "OFF, 1, 1+2, 2" switch (assume that you already have this) to allow you to select either bank in an emergency, but run normally on Bank 1 for all your needs.

You will need to carefully figure out the wire lengths, crimp heavy lugs onto the ends, and I would connect to the "OFF, 1, 1+2, 2" switch through no less than AWG 2. I also suggest a >175AMP MRBF on the + connector of each bank.