Need Help w/ Battery Cable Sizing

[rbmcintire]

Ok, my journey continues. So far I have not been able to understand the parameters to decide on sizing the cables for my new battery configuration. I have Calder's book but all the pieces are not coming together for me yet. Existing setup is two banks of two, a pair of 65Ah's and a pair of 85Ah's. Blue Sea Systems 1-2-B. I want to combine these four into a new House bank and charge them w/ a Freedom HF 1800W I/C (40 amp charging). The HF 1800 documentation requires 2/0 to the bank, but do I continue the parallelling of the House batteries with 2/0 jumpers or not? I assume when I've got the flat screen, coffeemaker and microwave all going at once that the amp draw may need 2/0?

Rob

 

[Don S/V ILLusion]

you might want to reconsider combining batteries of different capacity into a single bank as the charger will sense the two smaller ones first as fully charged and never charge the larger ones fully which is the second worst thing you can do to a battery.

 

[Stu Jackson]

The 2/0 wiring is needed to take the power OUT of the bank to serve the inverter. So make both Positive and Negative distribution posts for the house bank and run the 2/0s to there, then #2 wiring should suffice between the individual batteries within the bank. That's what I did in 1998 on our Freedom 15, and its been working ever since.

Here's a wiring diagram, see reply #23: http://c34.org/bbs/index.php/topic,4623.msg27335.html#msg27335

 

[rbmcintire]

you might want to reconsider combining batteries of different capacity into a single bank as the charger will sense the two smaller ones first as fully charged and never charge the larger ones fully which is the second worst thing you can do to a battery.

Well, to make it even worser, I've purchased a 79Ah AGM to be my Reserve. The ACR will be a Blue Sea Systems SI (start isolating). I was hoping to get by on the old wet cells as House and buy only one new battery this first year, for a reliable Reserve, so we could head out on the Bay, learn more about this sailing thing and have a higher probability of making it back. I don't have a lot of faith in the remaining longevity of the two pairs. One group is 2007 and the other two I recently discovered are
2001 (older than I previously thought). Let me ask you this: the existing setup from the previous owner has a separate battery charger for each group of two (a Guest and a Truecharge). Should I:
1.) Hold off the install of the Freedom HF and ACR until I get all AGM's?
2.) Install the HF only (and not the ACR) for the House. Plus also, put the AGM on the 3-step Truecharge and never, never, never select "Both" on the battery switch? Boatyard Sale the Guest charger?
I really want to have as many comforts of home available to my wife and kids so their experience on the boat will be as "normal" as possible.

Rob

 

[Stu Jackson]

It all depends on how it's wired

Do you intend to plug in all week when you're away?

If so, reconsider. Staying unplugged is safer.

I'd install the Freedom, then make the choice later, after I've done some homework, what I want to connect to (i.e., new batteries) and how I want to wire my boat.

It's gonna take a while to get the first step accomplished anyway.

Try this: http://c34.org/bbs/index.php/topic,4949.0.html

Oh? Normal on a boat? Keep dreamin'...

 

[rbmcintire]

The 2/0 wiring is needed to take the power OUT of the bank to serve the inverter. So make both Positive and Negative distribution posts for the house bank and run the 2/0s to there, then #2 wiring should suffice between the individual batteries within the bank. That's what I did in 1998 on our Freedom 15, and its been working ever since.

Here's a wiring diagram, see reply #23: http://c34.org/bbs/index.php/topic,4623.msg27335.html#msg27335

Thanks, Stu. I see the wire sizesin your diagram. If 2AWG is sufficient, then it's quite a money saver to go that route.

Rob