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Old 19-01-2014, 17:53   #1
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Distance between batteries in one bank?

Currently I have a 2 battery house bank and a 1 battery reserve bank. I want to add a 3rd battery to the house bank but the nearest location to put it is approximately 10 feet away via the route the cable would take from the other 2 batteries. Is it ok / effective to have a battery hooked up in parallel in the same bank that far away?
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Old 19-01-2014, 21:08   #2
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Re: Distance between batteries in one bank?

it's definatlly not ideal. they will not charge / discharge equally. and you'd need fuses on each side of the jumper wire so you don't have a 10' long unfused jumper wire.
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Old 20-01-2014, 06:06   #3
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Re: Distance between batteries in one bank?

That's what I was afraid of. Thank you for the input. Looks like I'll have to figure something else out.
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Old 20-01-2014, 06:24   #4
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Re: Distance between batteries in one bank?

I wouldn't give up, but I would find someone who knows more about charging than I do. Here are my thoughts to guide your questioning:
-The requirement for fuses on the cables between the batteries is correct. Do it.
-The problem with having the batteries a significant distance apart is that the connecting wires have resistance; there will be a voltage difference between the batteries.
-The way to reduce the voltage drop is to use large diameter wires ($$). The WEST Marine catalog has graphical comparisons/recommendations for wire sizes VS length and current draw for 2 voltage drops

Now for some speculations: I wonder just how much of a practical difference it makes that the batteries don't charge exactly the same?

Good luck

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Old 20-01-2014, 06:34   #5
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Re: Distance between batteries in one bank?

Just my two cents worth! I just installed a slide in camper into my pick up and wanted a herky house set up as I also installed a 3000 watt inverter. The camper came with a good 12 volt deep cycle battery. I happened to possess several good 6 volt deep cycle batteries. My proposal was to install two of the 6 volters in series, then in parallel to the 12 volter. The was nixed by the gurus because they have different charging rates. Ostensibly, the battery becoming fully charged first would signal the regulating system that it was fully charged and the others would never receive a full charge. Just how it was explained to me. I ultimately went with four of the 6 volters with equal charging rates. George
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Old 20-01-2014, 11:14   #6
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Re: Distance between batteries in one bank?

While not ideal to have batteries in a single bank separated by 10' it can be done if the positive feed was from one battery and the negative feed was from the other. The load or charge current will then be balanced as each battery will see the same voltage drop in the 10' cable. However if the intended load current or charger current is much over 50A then the cost of heavy battery cables and fuses as recommended would most likely make it impractical.
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Old 20-01-2014, 11:38   #7
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Re: Distance between batteries in one bank?

Quote:
Originally Posted by ontherocks83 View Post
That's what I was afraid of. Thank you for the input. Looks like I'll have to figure something else out.
Consider a Echo Charger of some description. When the existing house bank reaches a preset state of charge, the excess is "trickled" to the next battery.

Battery Chargers | Auxiliary Battery Charger | Xantrex

While I have a Xantrex and have been happy with it, there are other brands working on the same principles.
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Old 20-01-2014, 13:14   #8
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Re: Distance between batteries in one bank?

what about the battery for the windlass, located in the bow area?
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Old 20-01-2014, 14:28   #9
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Re: Distance between batteries in one bank?

Quote:
Originally Posted by S/V Alchemy View Post
Consider a Echo Charger of some description. When the existing house bank reaches a preset state of charge, the excess is "trickled" to the next battery.

Battery Chargers | Auxiliary Battery Charger | Xantrex

While I have a Xantrex and have been happy with it, there are other brands working on the same principles.
I like the idea of a xantrex for the starter battery but for the house bank I was just trying to make it bigger with an additional battery, not sure its worth the trouble though.

How do you like the xantrex, I have been eyeing that for some time but haven't heard much what people think of them
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Old 20-01-2014, 17:33   #10
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Re: Distance between batteries in one bank?

Quote:
Originally Posted by ontherocks83 View Post
I like the idea of a xantrex for the starter battery but for the house bank I was just trying to make it bigger with an additional battery, not sure its worth the trouble though.

How do you like the xantrex, I have been eyeing that for some time but haven't heard much what people think of them
I used it (and will use it again) to keep the starter battery charged from the house bank. It worked as advertised, and meant I could route all alternator output just to the house bank, as it was through that circuit that the start was kept charged.

This simplified things for me. You have to have the habit of monitoring your states of charge, however.

Some people have said that the Xantrex echo chargers can be a little flukey. Not mine, and not so far. The principle of echo charging is a good one, I think, particularly on the hook with solar or wind, as it gives you a "dump" for all those amps you are making (literally) while the sun shines but which you may not be using at that point.
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Old 21-01-2014, 01:29   #11
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Re: Distance between batteries in one bank?

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Originally Posted by ontherocks83 View Post
That's what I was afraid of. Thank you for the input. Looks like I'll have to figure something else out.
Don't be afraid it is possible.

I have 5 AGMs in different locations. Each battery has 2/0 cables going to one central Bus Bar where all charging/loads are connected. Each cable to each battery is the same length. I get a 0.01v drop on each cable when under the 20 hour rated current. The batteries are now 10 years old and all test the same under load.

Yes it will cost more for the extra cables and size, and fuses, but if it gets you a battery capacity that you want/need then it will be worth it. It is a one-off cost that will make the batteries last longer.

Don't add a new battery to an old bank. All should be the same type and age - they can however be different Ah capacity/size to fit different locations, and the charging/loading will still be balanced. All battery manufacturers recommend a "Balanced" wiring regime - see other current posts.

Unfortunately there are a few serial offenders on this forum who would disagree.

I saw a wonderful signature on another site: BEWARE INTERNET FORUMS MAY CONTAIN NUTS.
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Old 21-01-2014, 05:16   #12
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Re: Distance between batteries in one bank?

I think Andina has commented on this issue. In a purely theoretical world , the balancing of interconnecting leads would be an issue.

In the real world it is not. Batteries have a spread of internal impedance , especially as they age , connector resistance , etc etc. mean that in practice it's makes little to no difference what lengths the interconnects are.

Fuse long cables for safety

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Old 21-01-2014, 07:36   #13
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Re: Distance between batteries in one bank?

Thank you all for the info. I will definitely be considering all options.

If people don't mind I'd like to expand on my question.

I was thinking of setting up a positive bus just for things that can be physically hardwired to the battery. In my case the alternator, the charger, and the bilge pump.

My variation to this and why I want a dedicated positive bus for these is I was going to put an on/off switch between the positive bus and the house bank incase I need to 100% isolate that bank.

My specific question relates to the charger. The charger has a lead for the positive post and one for the negative. If I put the Positive lead to the dedicated "hard wire" positive bus and the negative lead to the negative bus does this still work the same as hardwiring the charger straight to the battery?

Also with this set up I would be using either an acr or xantrex echo charger for the start battery.

Thank you all again for your advice and I appreciate any further insight on this set up or my original question.
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Old 21-01-2014, 08:10   #14
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Re: Distance between batteries in one bank?

Could the extra battery not just be connected with H/D welding cables,

Battery to Battery,
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Old 21-01-2014, 08:25   #15
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Re: Distance between batteries in one bank?

A positive bus with a switch is a good idea, wires of various sizes can then be properly terminated to the bus rather than stacked haphazard on the battery terminal. The only other wires you may want to connect directly to the battery terminal are battery voltage sense wires from an external alternator regulator and a battery monitor, these should be fused as well.

Just don't turn the switch off when the alternator is running, alternator diodes don't like that.
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