Mike, it's certainly doable and has been done. I believe Tom Grover has done this, perhaps he will weigh in and give his experience. It just depends on whether you need the additional capacity or not. We've found with two sets of 6 volts giving us 464 amps and our daily amp draw of about 80-100 amps we're fine, but everyone has different needs. We live aboard for 3 months in the summer and we only take a dock about every 10 days, rest of the time we're on anchor. Finding out what you will need is probably the starting point. The distance involved shouldn't be an issue though as long as you use appropriately sized cables. Big banks will take more charging time as well. More batteries/cable = more weight and while these are big boats we're finding there is a limit to how much stuff you can put in/hang on them.

That's where my #2 battery bank lives.

Hi Mike

I took out the bottom two drawers in the nav station and put two 6v batteries in there. Along with the four 6V batteries under the seat in front of the nav station it gives me 696 AH of battery power for the house bank. I also installed the inverter/charger under the nav table so it is as close to the batteries as possible and I still have lots of knee room at the nav table. Hope this helps.

Mike

I am toying with a similar plan but using it to build a pop/beer cooler you can sit on in place of the nav table seat. I figure if it is well insulated, ice should keep the refreshments cool and reduce the space taken in the fridge and also reduce the number of times the fridge is opened. Of course a drain will be included in the design.

I got rid of the seat and installed a 50 qt waeco cooler it can work as a freezer or frigerator ,my wife loves it for drinks and milk

Mike,

My rational with selecting a 696 ah battery bank is they say you should not discharge it more than 50% before recharging in order to get the best service life out of you batteries. So that gives us 348 ah before needing a recharge. That should be about 5 to 6 days if we manage our consumption properly. In order to help with that, I am replacing our 23 year old Adler Barbour system with a Frig-o-boat keel cooled system and upgrading the insulation around the fridge box.

Bill,

I like that idea. How is the electrical consumption on the Waeco cooler?

Iam not sure at this time because I just installed a xantrax linkpro so the next time Iam off shore power will check seems better than my cold machine have use it for about 5 years

[QUOTE=tgrover;16260]Mike,

My rational with selecting a 696 ah battery bank is they say you should not discharge it more than 50% before recharging in order to get the best service life out of you batteries. So that gives us 348 ah before needing a recharge. That should be about 5 to 6 days if we manage our consumption properly. In order to help with that, I am replacing our 23 year old Adler Barbour system with a Frig-o-boat keel cooled system and upgrading the insulation around the fridge box.

Bill,

I like that idea. How is the electrical consumption on the Waeco cooler?[/QUOTE]

Actually on your second day out, away from the dock, you only have about 30-35% usable capacity. It is darn near impossible on a sailboat, away from a shore charger, to ever get flooded batteries back much above 85% SOC...

It's called declining acceptance.....:mad: So in reality you really only have a 243Ah bank.. Now, if your average draw is low, well below the 20 hour rated draw for that bank or 34.8A, you will get more than 243Ah's... Adding more batteries just boosted your capacity due to Peukert.....;)

I posted this on my forum at SBO a while ago:

Recently I've read a few posts where folks state;

"At the rated 1A draw you'll get X amp hours." or "At the rated 5A draw you get X amp hours."

The Ah capacity used for deep cycle batteries in marine applications is a 20 hour Ah rating. Most all battery monitors need this 20 hour rating to be programmed correctly and most all reputable battery manufacturers of deep cycle batteries can supply you with the 20 hour Ah rating. They will also supply you with the Peukert factor for programming a battery monitor.

To figure the load your battery can support to deliver the same Ah's as the 20 hour rating you divide the rated 20 hour Ah capacity by 20.

100Ah Battery / 20 = 5A

So a 100 Ah battery can support a 5A load for 20 hours before falling to 10.5V which is considered dead for the 20 hour capacity test.

60Ah Battery / 20 = 3A

So a 60Ah battery can only support a 3A load for 20 hours before hitting 10.5V.

130 Ah / 20 = 6.5A

And a 130 Ah battery can support a 6.5A load for 20 hours before hitting 10.5V.

As you can see the "rated load" is entirely dependent upon the Ah capacity of the specific battery in question. A 60Ah battery can not be applied the same load as a 160Ah battery and hit it's rated capacity over 20 hours.

But there is a GOTCHA always is......

Here's the catch, it is called the Peukert Effect. In very simplistic terms it means that any load applied to the battery ABOVE the 20 hour rating will result in less Ah capacity. On the other hand any load below the 20 hour rating will result in more Ah capacity.

I think looking at the math will help. This is the math on a 100Ah battery.

100 Ah Battery With A Peukert Factor of 1.25:

100Ah Battery - 80 Load = 50 Ah Capacity

100Ah Battery - 50A Load = 56.23 Ah Capacity

100Ah Battery - 40A Load =59.5 Ah Capacity

100Ah Battery - 30A Load = 63.9 Ah Capacity

100Ah Battery - 20A Load = 70.7 Ah Capacity

100Ah Battery - 10A Load = 84 Ah Capacity

[B][COLOR="DarkRed"]100Ah Battery - 5A Load =100 Ah Capacity[/COLOR][/B]

100Ah Battery - 3A Load = 113.6 Ah Capacity

100Ah Battery With - 1A Load = 149.5 Ah Capacity

I highlighted the 5A load in red because that is exactly what the divide Ah capacity by 20 gets you too, as I mentioned above.

As you can see any load above the rated capacity at the 20 hour Ah rating results in less Ah capacity. Any load below the 20 hour capacity rating and you have more available Ah capacity..

This is why I almost always cringe when I see people wanting to use large inverters with 80A+ draws on the battery or bank. It can cut your available capacity and without a properly programmed battery monitor you'll not know it.

It is also another reason why a larger bank with smaller loads will survive better.

Take a parallel bank of four 100Ah batteries. You now have a 20 hour rating that can support a 20A load, or 5A per battery, X 4 = 20A. When you run this bank at an average load of say 8A you'll really have 503Ah bank.

If you add just one more battery and make the bank 500Ah's and you'll have a 25A support load, BUT, apply the same 8A load and you have a bank that can deliver 665 Ah's using an average of an 8A load.

Conversely, size your bank small at 100Ah, which would have a 5A support, and still apply the same 8A load and you really only have an 89 Ah bank. Bank size vs. load matters and the bigger the bank and the lower the load the less capacity you use and thus the shallower the discharge cycle. Shallow discharges are good for the battery bank and deep discharges are bad.

This should help explain why we humans, unless perhaps you're Stephen Hawking, can't keep track of Ah capacity by simply watching the amp screen on a simple ammeter.

A battery monitor will make all these calculations for you internally and then represent them as a % of bank capacity. This of course only works well if it has been programmed correctly. For proper programming, at a minimum, you need the banks total Ah capacity, at the 20 hour rate, and the Peukert factor for your specific batteries.

Tom
Nice Job, did you cut out the wall seperation in front to get the batteries in?