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Discussion Starter · #1 ·
After reading all the excellent advice in my previous thread (http://www.sailnet.com/forums/electrical-systems/134770-would-you-buy-used-agms.html), I've opted to buy four new flooded golf cart batteries rather than the questionable AGMs I was asking about before. They're about the same price -- I got the GC115's from BatteriesPlus; with a quantity 4 discount they're $100/ea. My research suggests these are relabled Deka GC15s, and the BatteriesPlus rep confirmed this. They had a better Ah/$ rating than any other size I looked at, including the GC25.

So now comes the question of how do I install them. I bought four single-battery boxes from Defender, so I think physical installation is handled, but I'm wondering about electrical. My existing system is two "banks" of one Group 27 each, wired to a 1-2-both-off switch (separate positive and negative cable for each). I do not have a separate starting battery nor do I have space for one. I have never treated these banks as separate, the switch is always either off or both. Thus I intend to wire them as a single bank. It will also ease installation of my new battery monitor (Victron BMV-700, to better obsess over my new batteries, of course), which wants a shunt in the negative lead to the bank. Does this seem like a good idea?

I'm thinking jumpers between two sets of two batteries to make them 12V, then jumpers between the 12Vs and grounds, respectively, to form them into a single bank. I'll then connect my two positive leads to the combiner switch to one "corner" of the bank, and the two negatives to the other corner. What size wire should I use for the jumpers? My system is a mix of 1/0 (or maybe 2/0) cables to the bank plus 4/0 from the combiner to the inverter/charger. I'm thinking the jumpers should be 1/0 or 2/0 but I'm not sure which. They'll be very short, probably only about a foot.

Thanks!
 

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I wired my 4 6V batteries into 2 banks because that is the way my boat was already wired. I don't have a 1,2, both switch like lots of boast and instead have a sepaerate breaker from each bank to the main DC panel. I also have another switch that selects which bank (1,2, or both) supplies the inverter and that same switch determines which bank charges from the alternator.

I normally run with both banks supplying the main DC panel and the inverter switch in both.

I have a Victron BM and all ground legs go though it before branching out to the 2 battery banks. The BM is programed for the total house battery capacity as that is what it is far as the BM cares. If I were to have to take out a bank all I would need to do is change the capacity volume in the BM.
 

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So now comes the question of how do I install them. I bought four single-battery boxes from Defender, so I think physical installation is handled, but I'm wondering about electrical. My existing system is two "banks" of one Group 27 each, wired to a 1-2-both-off switch (separate positive and negative cable for each). I do not have a separate starting battery nor do I have space for one. I have never treated these banks as separate, the switch is always either off or both. Thus I intend to wire them as a single bank. It will also ease installation of my new battery monitor (Victron BMV-700, to better obsess over my new batteries, of course), which wants a shunt in the negative lead to the bank. Does this seem like a good idea?
Definitely wire them as one contiguous bank if you are using a shunt based battery monitor.. One large bank is also more efficient than two smaller banks.. It is easy enough for a battery monitor to get out of synch wiring two banks and using them as one via a switch will only lead to more eventual human errors and thus counting errors...

I'm thinking jumpers between two sets of two batteries to make them 12V, then jumpers between the 12Vs and grounds, respectively, to form them into a single bank. I'll then connect my two positive leads to the combiner switch to one "corner" of the bank, and the two negatives to the other corner. What size wire should I use for the jumpers? My system is a mix of 1/0 (or maybe 2/0) cables to the bank plus 4/0 from the combiner to the inverter/charger. I'm thinking the jumpers should be 1/0 or 2/0 but I'm not sure which. They'll be very short, probably only about a foot.

Thanks!
If you have 2/0 use that, 1/0 would work...


One way:


Same wiring just all batts in one box before it was epoxied.
 

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Discussion Starter · #4 ·
Thanks for the recommendations. I think I'll make a single bank using 2/0. Maine Sail, that's a beautiful wiring job in the top photo :)
 

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rm-
The quality of the crimps on the cable lugs is important, and making a good crimp can require an expensive tool. So if you weren't already set up for this, consider ordering the cables from genuinedealz.com, who will sell you marine grade cable with proper crimps installed, to order, for about the same thing you'd pay for the cable and fittings locally.

Some cheap rope cut up, or a tape measure, will make sure the lengths are right when you order. And of course, provide for proper primary fusing right on the battery bank at the same time.
 

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Discussion Starter · #6 ·
hellosailor, that's a good point. I was already planning on getting the cables from genuinedealz; I've always been very impressed with their service and prices. I hadn't really given thought to fusing the batteries. I see genuinedealz sells some battery terminal fuses that look like they'd work, but I don't see the blocks they're supposed to go with. Is there a particular fuse arrangement you'd recommend?
 

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Ask me first for a religion, or a wife.(G)

Mainesail found a number of no-name ANLs to be less than expected, so you might go to BlueSeas and check out what options they offer in the capacity you want and then consider if you want to may gen-you-whine prices, or explore options. And of course, get a couple of spares in case someone drops a wrench.
 

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Discussion Starter · #10 ·
Excellent link, as Maine Sail's articles always are :) One thing neither it nor the posts thus far have addressed, to my reading, is where to fuse: does each battery in the bank get a fuse, or each 12V series pair, or just one for where the bank connects to the house wiring?
 

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Normally, just one fuse is used for the house bank, located as close to the batteries as possible. ABYC calls for within 7 inches.

For many, the MRBF (terminal) fuses will be very convenient. For some, they may not be, due to height restrictions or other reason. There's at least one report of corrosion possibly due to out gassing from flooded batteries.

Note that only three type of fuses are acceptable for direct connection to a house battery bank: the aforementioned MRBF, the ANL (with caveats as reported by MaineSail), and the Class-T fuses which come in larger sizes and are appropriate for, e.g., large inverters. Other fuses do not have a large enough ampere interrupt capacity (AIC)....should be at least 5,000 amps.

Also, only one type of breaker meets this specification: the new Blue Sea Systems series.

You mentioned earlier that you'd connect both wires to the positive end and both to the negative end of the new battery bank. Not sure what you are thinking, but only one connection at each end is required, especially if you're going to use 1/0 or 2/0 cabling. That cable should go to either position 1 or position 2 on your switch...whichever you plan to use all the time.

Bill
 

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Discussion Starter · #12 ·
Ok, one fuse for the bank it is :) That's easier on the wallet.

The two wires is because I'm not going to replace the wires from my existing two banks. They seem quite servicable and redoing them is time and money I don't want to expend. So I have two wires now, which are probably 1/0, and I'll hook them up in parallel. The wire gauge I was asking about before was for jumpers between the batteries.
 

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A bit OT but about corrosion on fittings: Other than BoeShield I hadn't seen any anti-corrosion sprays on the market in ages. Last week I found one from Rustoluem, of all the odd folks, hiding with the spray paint cans. Apparently a thin wipeable film, meant for shovel blades, tools, whatever and I'm hoping good for anything including electrical connections.
 

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...My system is a mix of 1/0 (or maybe 2/0) cables to the bank plus 4/0 from the combiner to the inverter/charger. I'm thinking the jumpers should be 1/0 or 2/0 but I'm not sure which. They'll be very short, probably only about a foot.

Thanks!
Just make sure you are sizing your cables correctly. 4/0 for a combiner to charger and 1/0 or 2/0 for a jumper are overkill.
Do you mean 1 AWG not 1/0 AWG maybe?
 

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Discussion Starter · #15 ·
I don't think they're overkill. I sized the one to the inverter/charger using an online calculator. It can pull about 200A fully loaded, and it's probably a 6-8' from the combiner one way. This bank also feeds the engine starter and the autopilot, which are both heavy loads, though intermittent. I've actually been thinking that my battery cables to the combiner are a little on the small side, but since there are two of them I've decided it's good enough.
 

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One note: if you draw high amperage you may want to consider clamping to the post rather then bolting to the SS studs. They studs can heat up and melt out of the lead. There is simply not enough contact area.

 

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One note: if you draw high amperage you may want to consider clamping to the post rather then bolting to the SS studs. They studs can heat up and melt out of the lead. There is simply not enough contact area.

I've got 400A bow thrusters using less than the contact area on a marine battery stud post... We have starters on 800HP diesels with less contact area than a marine stud battery post and they do fine...

The ONLY time I have seen melting of terminals is from improper installation of lugs (bad crimp), improper battery nut torque, improper lug stacking or SS flat washers inserted between ring and battery..

I've never once seen a melted stud post terminal, when properly installed.

I actually dislike clamp style terminals because they tend to creep and stretch over time and tend to get loose. Many of the large cranking batteries today don't even offer clamp posts they are bolt through because of this. If I had a dime for every "clamp" post what was pinched as tight as it would go, until both ears were touching, and I could still twist it by hand......;)

Heck I have a 100' "Deadliest Catch" off shore fishing boat I work on with a 12' long Caterpillar diesel that uses ring terminals and has been since the boat was built...;)

But beyond all that lets follow the logical progression of the DC circuit and what is in the circuit for the highest amperage loads we'd see on a sailboat..

Starter - Never seen a lead clamp post on one, for ring terminals only
Battery Switch - Never seen a lead clamp post on one, for ring terminals only
Windlass - Never seen a lead clamp post on one, for ring terminals only
Bow Thruster - Never seen a lead clamp post on one, for ring terminals only
Inverter or Inverter Charger - Never seen a lead clamp post on one, for ring terminals only
ANL, Class T, MRBF Bank Fusing - Never seen a lead clamp post on one, for ring terminals only
DC Watermaker - Never seen a lead clamp post on one, for ring terminals only
HO Alternator - Never seen a lead clamp post on one, for ring terminals only
HO Battery Charger - Never seen a lead clamp post on one, for ring terminals only
High Amp Shunts - Never seen a lead clamp post on one, for ring terminals only
High Amp Busbars - Never seen a lead clamp post on one, for ring terminals only
 
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