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Old 12-04-2016, 12:44   #1
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Split Location For House Bank.

I am upgrading my house bank for my 42' sundeck. I was able to fit four lead acid golf cart batteries in the engine compartment but I have six batteries available. I am using 2/0 cable for interconnects. I am using 3/0 cable to go to the inverter that is 3' from the battery bank. The PO had the battery bank under the dinette seat in the galley. It is about 3' from the new battery bank location the opposite way from the inverter.
Question:
Can I put the extra two batteries under the seat where the PO had them for the third 12V section of the house bank? It is vented. Will the 3' of interconnect vs. 1' be too much of a voltage drop?
I don't have to have the two extra batteries based on the usage calculations I made, but it would be nice. I have the charging capacity to keep them up when the starboard engine is running. The inverter is a Victron Energy 12/3000/120 multiplus.
Thanks in advance.
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Old 12-04-2016, 12:51   #2
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Re: split location for house bank.

Yes, that should be fine.

I don't like the batteries in the engine room, though. But if you have to, you have to.

Bill




Quote:
Originally Posted by mcgann454 View Post
I am upgrading my house bank for my 42' sundeck. I was able to fit four lead acid golf cart batteries in the engine compartment but I have six batteries available. I am using 2/0 cable for interconnects. I am using 3/0 cable to go to the inverter that is 3' from the battery bank. The PO had the battery bank under the dinette seat in the galley. It is about 3' from the new battery bank location the opposite way from the inverter.
Question:
Can I put the extra two batteries under the seat where the PO had them for the third 12V section of the house bank? It is vented. Will the 3' of interconnect vs. 1' be too much of a voltage drop?
I don't have to have the two extra batteries based on the usage calculations I made, but it would be nice. I have the charging capacity to keep them up when the starboard engine is running. The inverter is a Victron Energy 12/3000/120 multiplus.
Thanks in advance.
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Old 12-04-2016, 12:54   #3
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Re: split location for house bank.

Bill,
Thanks for the quick reply! Can you expand on the engine room location problem? They are diesels (perkins) and a forced vented large engine room. Is the heat the biggest objection? I put them in the engine room to get them as close to the inverter as possible. The inverter is in the cabin by the panel.
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Old 12-04-2016, 13:01   #4
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Re: split location for house bank.

Yeah. It's the heat, since heat can affect battery longevity, charging times and maximum charging voltage, self-discharge rate, etc.

However, in a large engine room with good ventilation the problem is somewhat mitigated.

Bill
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Old 12-04-2016, 13:52   #5
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Re: split location for house bank.

I have a large 1300 amp battery Bank it is split in 3 locations even though they were all in the engine Department. No problem whatsoever
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Old 12-04-2016, 15:24   #6
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Re: split location for house bank.

The difference in cable length to the different locations will cause the current drawn from the batteries to be unequal (because of the different resistances in the circuits). Everything may appear to be fine but you are not getting the capacity you paid for.

Put simply, the batteries with the longer cables will not be doing their share of the work.
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Old 12-04-2016, 16:24   #7
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Re: split location for house bank.

Not true. if You install the positive and negative Cables at the opposite end of the banks
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Old 12-04-2016, 16:39   #8
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Re: split location for house bank.

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Originally Posted by rwidman View Post
The difference in cable length to the different locations will cause the current drawn from the batteries to be unequal (because of the different resistances in the circuits). Everything may appear to be fine but you are not getting the capacity you paid for.

Put simply, the batteries with the longer cables will not be doing their share of the work.
I figured that the isolated batteries would not be equal to the other four. I have been reading every thread I can find here on house banks. The question should have been will using 2/0 cable for the house bank interconnects make the drop negligible? Many are using lighter AWG cable.
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Old 12-04-2016, 17:00   #9
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Re: split location for house bank.

With a 100 amp starting load, 3' of 2/0 cable will drop about 47 millivolts. That's .047 volts.
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Old 12-04-2016, 17:13   #10
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Re: split location for house bank.

Quote:
Originally Posted by mcgann454 View Post
I figured that the isolated batteries would not be equal to the other four. I have been reading every thread I can find here on house banks. The question should have been will using 2/0 cable for the house bank interconnects make the drop negligible? Many are using lighter AWG cable.
Inverter manuals suggest using the same size wiring from the inverter TO the house bank for ALL house bank battery connections.
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Old 12-04-2016, 17:38   #11
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Re: split location for house bank.

I have 6 GC batteries on Cbreeze, 4 midships and 2 in the bow. They are normally all connected in series/parallel. Bow thruster and windlass tapped directly (with breaker/ fuses) from the fwd bank and inverter is 2' from the 4.

When I fire off the bow thruster it draws 200 amps from the fwd bank and 100 amps from the main. I am sure that after running the thruster there is a small voltage difference between the two banks. This voltage difference will cause a current to flow from the main bank to the fwd bank but in time as the voltage equalizes the current will go to near zero and all is well. When I run the inverter the reverse will happen. Been running it that way for 10 years.

Some that question this arrangement seem to not understand that as the current diminishes the voltage drop also diminishes (its called Ohms Law) even if the two banks are tied together with a piece of #22 gauge hook up wire. My main bank is wired with #1 AWG and the fwd bank is wired with #1/0. The interconnect is #2 fused at 150 amps on both ends.

Each set of batteries is individually switched. A couple of times a year I start my 3GM from each bank starting with the bow set. I can't tell the difference in how fast it starts from each of the three sets even though the fwd bank has a lot more resistance in the circuit.
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Old 12-04-2016, 17:52   #12
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Re: split location for house bank.

Quote:
Originally Posted by motion30 View Post
Not true. if You install the positive and negative Cables at the opposite end of the banks
It is true. He is talking about spreading the banks around different parts of the boat. Draw it out on paper.
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Old 13-04-2016, 11:22   #13
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Re: Split Location For House Bank.

Quote:
Originally Posted by mcgann454 View Post
I am upgrading my house bank for my 42' sundeck. I was able to fit four lead acid golf cart batteries in the engine compartment but I have six batteries available. I am using 2/0 cable for interconnects. I am using 3/0 cable to go to the inverter that is 3' from the battery bank. The PO had the battery bank under the dinette seat in the galley. It is about 3' from the new battery bank location the opposite way from the inverter.
Question:
Can I put the extra two batteries under the seat where the PO had them for the third 12V section of the house bank? It is vented. Will the 3' of interconnect vs. 1' be too much of a voltage drop?
I don't have to have the two extra batteries based on the usage calculations I made, but it would be nice. I have the charging capacity to keep them up when the starboard engine is running. The inverter is a Victron Energy 12/3000/120 multiplus.
Thanks in advance.
Sounds as if you have it covered.
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Old 13-04-2016, 11:28   #14
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Re: Split Location For House Bank.

Thanks for all of the replies. It sounds like it should be fine.
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Old 13-04-2016, 17:58   #15
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Re: Split Location For House Bank.

You'll be fine with different locations. But definitely hook them up in with the positive at one set and the negative at the other end. You want to encourage equal current to come from/to each battery. So don't have a central positive bus and negative bus that each 12v battery set connects to.
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