Split Location For House Bank.

[leftbrainstuff]

Originally Posted by mcgann454

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.

Should be ok keep wire runs as short as possible and locate batteries as low down and as close to the center of mass as possible.

We have 6 trojans. 4 are grouped together and the other 2 are adjacent the mast. They are paired with 3 isolators.

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[smac999]

split banks become an issue with a shunt. the runs become pretty long do it with right with an end to end wired bank with single ground.


if you do it "improper" and have the 2nd bank feeding the first bank, and loads not end to end, then the wiring is less long.


you definatlly want more then 4 golf carts with a 3000w inverter

[twinboat]

Originally Posted by leftbrainstuff

We have 6 trojans. 4 are grouped together and the other 2 are adjacent the mast. They are paired with 3 isolators.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

What does "paired with 3 isolators" mean ?

[Dockhead]

Originally Posted by exMaggieDrum

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.

And if you don't do this?

I have a situation similar to the OP's, except that I had two separate banks in separate locations which I combined. It was not possible nor desirable to take the power off only the ends of each bank -- loads are connected to one bank or the other.

I've been using it this way for 6 years, and it works ok. If one part of the bank is disproportionately discharged, remember that when the load is taken off, the charge will equalize -- the batteries which weren't drawn down will "charge" the ones which were.

The problem, if I understand it correctly, is the small differences in voltage resulting from the cables, which prevents this effect from being entirely effective.

[Dockhead]

Originally Posted by smac999

split banks become an issue with a shunt. the runs become pretty long do it with right with an end to end wired bank with single ground.


if you do it "improper" and have the 2nd bank feeding the first bank, and loads not end to end, then the wiring is less long.. . .r

That was exactly my logic.

[Frankly]

Emeter/ shunt location is an issue with my tapping the fwd bank directly to power the bow thruster and anchor windlass. My out for this is the duty cycle for both these loads is rather small and thus the total AH missed by the Emeter is not a big concern (these AH meters are not real precise). 300 amps for 30 seconds is only 2.5 AHs and 30 seconds is a lot of bow thrusting (ignoring Mr Peukert).

I considered running a second load return back to the ground bus but that defeats one of the advantages of getting the 12V source near the load. For different arrangements this might not be the case.

[rwidman]

You can put some of your batteries in the bow, some in the stern and some in the bilge, connect them all together and think you're doing fine. Everything will work.


But, as someone who did this mentioned, the current drawn from each set is different, based on the resistance of the interconnecting cables. This means that some batteries are carrying more of the load and some are carrying less. You don't actually have the capacity you would expect based on the battery ratings. Charging will be unequal as well.

[Dockhead]

Originally Posted by Frankly

Emeter/ shunt location is an issue with my tapping the fwd bank directly to power the bow thruster and anchor windlass. My out for this is the duty cycle for both these loads is rather small and thus the total AH missed by the Emeter is not a big concern (these AH meters are not real precise). 300 amps for 30 seconds is only 2.5 AHs and 30 seconds is a lot of bow thrusting (ignoring Mr Peukert).

I found it impossible to rig up a shunt which would allow a Victron battery monitor to work normally with my combined remote banks. I wasted some money having a professional try it, but he failed.


For a few years I've just used system voltage to evaluate battery state and that's worked quite well.

Now I have a SmartGauge which does not need shunt. The makers advised me to connect the negative lead to the negative of one bank, and positive to the positive of the other bank. I'll report on how well it works in this configuration.

[twinboat]

If you charge them long enough they will equal out.

The voltage drop is based on amps carried. As they charge, the amps drop and the voltage will rise. Once the close ones reach 100% the others will follow.

The closer batteries will do a bit more of the work but you could rotate them seasonally.

[mcgann454]

Thanks All for the input. New question, though.
I'm having trouble getting all the cables on the T class fuse holder for the batteries. I was going to run each 12 v group to the holder for the positive and the negative to the shunt. Would it OK to parallel the two battery groups in the engine compartment and then connect those four to the fuse holder and the shunt with the remote batteries? I plan on putting a fuze on the remote battery positive terminal to be on the safe side and comply with the 7" rule.

[exMaggieDrum]

Mcgann,
You should only need to connect one battery to the fuse - if you wire it the recommended way which is to parallel the three battery 12v sets (if using 6v batteries in series to make a 12v set) together first, and then run one, and only one cable from the positive of one battery (e.g. #1) with #2 in the middle, and one and only one cable from from the negative post off of battery #3. You should not run cables for each battery set positive to the fuse, nor should you run each 12v battery set negative to the battery side of the shunt.

This allows/requires all the charging and discharging current to go through all the batteries. The most current will always take the path of lowest resistance which may be to only one battery set the way you indicate you would do, and, that is not a good thing. It will work so far as powering the boat but the individual batteries will grow unbalanced with different current flows going in and out of each set.

[mcgann454]

Originally Posted by exMaggieDrum

Mcgann,
You should only need to connect one battery to the fuse - if you wire it the recommended way which is to parallel the three battery 12v sets (if using 6v batteries in series to make a 12v set) together first, and then run one, and only one cable from the positive of one battery (e.g. #1) with #2 in the middle, and one and only one cable from from the negative post off of battery #3. You should not run cables for each battery set positive to the fuse, nor should you run each 12v battery set negative to the battery side of the shunt.

This allows/requires all the charging and discharging current to go through all the batteries. The most current will always take the path of lowest resistance which may be to only one battery set the way you indicate you would do, and, that is not a good thing. It will work so far as powering the boat but the individual batteries will grow unbalanced with different current flows going in and out of each set.

Wouldn't that require me to run three cables to the remote group of two batteries?
Either the pos or neg would have to come off of that to do that correct?
Thanks,

[exMaggieDrum]

Originally Posted by mcgann454

Wouldn't that require me to run three cables to the remote group of two batteries?
Either the pos or neg would have to come off of that to do that correct?
Thanks,

If you have one bank (#1 say) near your new fuse you could run one cable from its positive to the fuse. The positive and negative for that battery would go to #2 of the remotes. #2 would have cables from its positive and negative posts (there would be two cables on the #2 positive) to #3. The negative on #3 would go to the shunt (if you have one) or to the main negative bus). So #3 would have one cable on its positive from #2. It would have two cables on the negative, one from #2 negative and one to the shunt.

So, yes you would have three cables to/from the remote batteries - one from #1 positive, one from #1 negative, both going to #2. And there would be one going to the shunt from #3 negative. Only one cable from #1 positive to the fuse.

[exMaggieDrum]

Originally Posted by mcgann454

Wouldn't that require me to run three cables to the remote group of two batteries?
Either the pos or neg would have to come off of that to do that correct?
Thanks,

If you have one bank (#1 say) near your new fuse you could run one cable from its positive to the fuse. The positive and negative for that battery would go to #2 of the remotes. #2 would have cables from its positive and negative posts (there would be two cables on the #2 positive) to #3. The negative on #3 would go to the shunt (if you have one) or to the main negative bus. So #3 would have one cable on its positive from #2. It would have two cables on the negative, one from #2 negative and one to the shunt.

So, yes you would have three cables to/from the remote batteries - one from #1 positive, one from #1 negative, both going to #2. And there would be one going to the shunt from #3 negative. And three cables from #1 - one to the fuse from the positive, and one from that same positive to #2, and one from the #1 negative to #2 negative.

[Cadence]

It seems like the OP has every thing in hand and some other posts are making a simple thing complex.