Adding more batteries to a bank

[David Popken]

So, I read on RC's PBase site that it's not a good idea to add batteries to a bank that are not in close proximity to each other. I would like to add two more 6v batteries to my existing pair of 6v Trojans. I have space under the Nav seat about 4' away from the existing pair. It seems to me that with the proper cable sizing, I will not experience any significant voltage drop for a run of that length and I can properly fuse them at the positive terminals. My question is, what is/are the negative aspects of doing this? I have no more room under the quarterberth for additional batteries, so to keep them all together, I would have to dedicate an entirely new location for all of the batteries, thus entailing all new cables for EVERYTHING and in the process, the main cable runs would by necessity be longer than they are now. I'm not even sure if there is a viable option at present for another location.

David Popken

 

[woodster]

some tomes you just have to do what you have to .......at the least you will have to up size all the cables if yours are not the correct size for the round trip run even the jumpers for joining the 2 6v in each set ...along with a larger negative cable and a positive cable and maybe even a larger alt cable to the maine bank...hope this helps

 

[Stu Jackson]

It seems to me that with the proper cable sizing, I will not experience any significant voltage drop for a run of that length and I can properly fuse them at the positive terminals. My question is, what is/are the negative aspects of doing this?

Essentially no negative aspects. You fuse the entire bank, not individual 12v sections within the bank. Just use the same size wires between the banks as used to the bank, assuming they are the right size to begin with.

 

[Maine Sail]

So, I read on RC's PBase site that it's not a good idea to add batteries to a bank that are not in close proximity to each other. I would like to add two more 6v batteries to my existing pair of 6v Trojans. I have space under the Nav seat about 4' away from the existing pair. It seems to me that with the proper cable sizing, I will not experience any significant voltage drop for a run of that length and I can properly fuse them at the positive terminals. My question is, what is/are the negative aspects of doing this? I have no more room under the quarterberth for additional batteries, so to keep them all together, I would have to dedicate an entirely new location for all of the batteries, thus entailing all new cables for EVERYTHING and in the process, the main cable runs would by necessity be longer than they are now. I'm not even sure if there is a viable option at present for another location.

David Popken

As long as the positive take off and the negative take off are one opposite ends of the bank it can work. If your parallel wiring is more than "jumper length" then both sides of the bank need fusing.

 

[Newport Bob]

Main,
Looking at your diagram I have a hookup question. My house bank is 2 4Ds, one in original spot aft of engine, the second in stbd locker. Cable runs between them ~ 4 ft. The hookup is takeoffs are both from the first bat. Second bat is connected pos to pos, net to neg. Is this OK?

 

[woodster]

i am not main but if you want full benefit of your charging circuit you need to do it like he has it ...that way it makes a complete round trip rather than charging the second battery by osmosis

 

[Newport Bob]

Thanks woodster, looks like I now have another project to add to the spring list. The current hookup "seemed" to work during our ICW trip last year, but your explanation makes sense for a better charge.

 

[David Popken]

Excellent! I have not done the requisite daily load calcs for my current power consumption, but I would like to add some type of 12v refrigeration. It would then seem prudent to have more than 110 AH of usable power. Would there be any problems with two newer and two older 6v's as a bank? How does one define "jumper length"? They will be +/- 4', so I'm guessing that's longer than "jumper length".

 

[woodster]

jumper length is usually 1 foot or less in most cases and iirc correctly fuses for the bats are supposed to be 9 or 7 inches from the battery post or directly on the post or stud

 

[dlochner]

Excellent! I have not done the requisite daily load calcs for my current power consumption, but I would like to add some type of 12v refrigeration. It would then seem prudent to have more than 110 AH of usable power. Would there be any problems with two newer and two older 6v's as a bank? How does one define "jumper length"? They will be +/- 4', so I'm guessing that's longer than "jumper length".

A related question. In a 4 GC battery system with batteries of equal age and type, is there any advantage or disadvantage to changing the pairing? That is if Battery 1 and 2 are in series and 3 and 4 are in series, does it matter if the pairing is changed to Battery 1 + 3 and 2+4?

 

[Maine Sail]

A related question. In a 4 GC battery system with batteries of equal age and type, is there any advantage or disadvantage to changing the pairing? That is if Battery 1 and 2 are in series and 3 and 4 are in series, does it matter if the pairing is changed to Battery 1 + 3 and 2+4?

No benefit. There is some benefit to commissioning & occasionally wiring the series batts in parallel and equalizing them as a parallel pair at 7.75V. You need a variable power supply to do this but it helps to rebalance the series batts especially after being used in a PSOC use situation..

 

[Stu Jackson]

I have not done the requisite daily load calcs for my current power consumption, but I would like to add some type of 12v refrigeration.

David, here's a true life example:

Record of Daily Energy Use of 100 ah per day:

http://c34.org/bbs/index.php/topic,6353.msg41471.html#msg41471

Here's a quick reference for an Energy Budget:

The All-Important Energy Budget:

http://c34.org/bbs/index.php/topic,3976.0.html

click on the PDF to open it

 

[David Popken]

Thanks Stu, very informative. Do or did you have led lighting? Also, in your calcs for an overnight passage, you have the autopilot taking 10 AH. Is that a real life result? And is that a below decks AP? Clearly, the refrigeration is the elephant in the room. I am considering one of the portable freezers, and trying to make do with our engine driven cold plate, plus upgrading the insulation around the box. Of course, adding solar or wind as a charging source seems to be a must if one wants to ride at anchor or a mooring for more than 2-3 days. I totally get the "acceptance" issue. Before I upgraded to a 30A shorepower battery charger, I had a 10A smart charger. After just a day sail, it would take a couple of days to get the banks back to 100% SOC!

 

[David Popken]

Currently have fusing right at the battery post, so I'll do the same for the two new ones.

 

[PatTormey]

The only difference is the inherent difference in the resistance on the battery cables and if the terminals are clean there won't be enough to measure even if there were 20 feet apart.