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Or maybe he puts them into two separate banks because SN told him to. Our job is to suggest to him what to do . His job is to read and do what works best for him. Sifting through opinions is what he should do. HOWEVER, I would read through Mainesail tutorials, our resident expert of electrical systems.

His issues are not his wiring, but his charging system. I recommended he start with a simple system he could build on and add to later as he increased his needs. To do that start with quality not cheap crap.

It consists of two banks like he has. A starter and a house. The house he will eventually add on. To charge efficiently and so not to ruin his new batteries he needs a three stage charger. And lastly to see how everything is doing while he learns his boat a battery monitor. 6 volts are true deep cycle batteries with thicker lead plates and more cycles, take vibration better. I suggest he buy an ACR ( cheap automatic combining relay by blue sea.) that way he never has to worry as I one bank was dead his other would combine. He gets a 220 ah bank which for now meets his needs. He can start with simple FLA if he wants or get AGM which he can configure in any formation. The AGM is more expensive but as he reads he decide water he gets that now or not.

A good sold system can be added to and won’t need constant replacement every two- three yers by going cheap. I have 1 house bank (6-6 volt AGM by Lifeline) Yes they are expensive. I probably could get by with 4. My first set lasted 10 years. Second set 10 yers. More than made up for their extra price. Good 40 volt three stage master charger shore power charger keeps them at 100% which AGM like. My alternator is 100 amp Balmar , watched by a remote Balmar three stage external AR5 regulator . Same concept as shore power charger, prevents the batteries from overcharge and destruction by heat sensors. Two 6 volt Lifeline AGM SYSTEM WITH Victron Monito and three stage shore power charger was about $800 when I bought it. All I had to do was add 6-volts to it. When I wanted to upgrade it. Next time in 8 years I may consider a LiFe type battery bu5 that’s a long way away. BTW Lifeline warranty is automatic for 1 yeR replacement. Prorated first 5 years. Anyone else do that?

BTW Maine doesn’t recommend AGM if I remember unless you can easily bring back to 100%. I didn’t recommend he get AGM to start his battery system.
 

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Discussion Starter #42
How is it a waste putting two batteries on separate banks? Since his other battery location is currently unuseable, this is his only option to have two banks until he rebuilds his starter battery box. Do you operate your boat on a single battery bank? If you don't would you? I would do so only in an emergency but would do everything to have a second starting option.

The reason I don't think he should put in two high end 6-v batteries are:

Something is possibly wrong with his electrical system that caused his old banks to go bad. It sounds like he is looking to throw new batteries at it without determining if there is something wrong first.

He currently does not have the knowledge to repair any issues if he can find them.

This is not a cost is no object project. He is concerned about the cost of epoxy to rebuild his battery box or the cost of a multimeter.

He does not know if 6v batteries will even fit, but he might impulse buy them because Sailnet told him to do so. If it does fit will he be able to also fit another battery in that compartment, or is he stuck with a single bank until he repairs his other battery box.

I estimate a single 6v battery bank to cost over $500 Canadian, which is a waste of money if they are put into an electrical system that killed his last 3 batteries.

Okay, so a little update. I finished by battery box, all epoxied up inside, it's the most expensive simple wooden box you've ever seen (had to pay 50 for the epoxy resin). Reattached my starting battery, and I'm at least up and running again.

You're right, jephotog,I was going to throw two batteries at it to try to solve the problem, but I've come around and decided to do some investigating instead.

Shortly, I'm going to pull out the house batteries and take a peak, top em up, etc. I just finished following all the wires from the Charles Charger to see where they go and they definitely go to both, so yeah, why is the house bank underperforming? I have a feeling the insides are about as dry as the starting battery I pulled out, so we'll see.

I have a multimeter now, so that should help. Just got to figure out what to do with it.
 

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You're right, jephotog,I was going to throw two batteries at it to try to solve the problem, but I've come around and decided to do some investigating instead.
Thank you now I can sleep better at night. Glad you are doing this project right.

When you are following the wire, you also need to inspect them.

The wires should be of sufficient size 10 gauge at minimum, likely much bigger depending on distance run.
The connections should be solid and corrosion-free. If the connections are covered with electrical tape peel back the tape and inspect.
 

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Thank you now I can sleep better at night. Glad you are doing this project right.

When you are following the wire, you also need to inspect them.

The wires should be of sufficient size 10 gauge at minimum, likely much bigger depending on distance run.
The connections should be solid and corrosion-free. If the connections are covered with electrical tape peel back the tape and inspect.
Its good to keep investigating. Keep reading
That way you’ll come to a more perfect solution for you

Since you are tracing old wires....why not just replace them if they at all look old or worn out
I would employ the gauge of wire which is appropriate to what is specked in the equipment keeping in mind the length of the run. I added a brief article about wire gauge so you are not guessing and listening to unqualified internet posters who are guessing at what you should use. There is no standard gauge you should use for all wiring. Length of run makes that determination. It’s a scientific formula vs a guess.

Connection are important too as Jeph noted. Wires should be crimped to good connectors .



No one ever suggested you just throw two batteries at your issue. I suggested when you eventually decide to UPGRADE to look at deep cycle golf cart 6 volt. There are obvious advantages.

Jeph.....Just curious .....what is your set up?
 

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Jeph.....Just curious .....what is your set up?
Here you go photos of my current boat's electrical layout. This is not my work but what I am currently working with. It was I strongly suggest anyone with a 30+ year old boat inspect and consider rewiring a boat upon purchase or before installing new batteries.
136486
136487
136488
136489



Since you are tracing old wires....why not just replace them if they at all look old or worn out
I would employ the gauge of wire which is appropriate to what is specked in the equipment keeping in mind the length of the run. I added a brief article about wire gauge so you are not guessing and listening to unqualified internet posters who are guessing at what you should use. There is no standard gauge you should use for all wiring. Length of run makes that determination. It’s a scientific formula vs a guess.
When I suggested inspecting the current wiring and look for 10 gauge, I was just throwing out a number of what he should look for to inspect for a current weakness in his current wiring. I was not suggesting he install 10 gauge when he rewires the boat. If he sees lamp wire instead of 10 gauge running from the charger to the batteries, suspect that as a potential problem.

Just to check my WAG I plugged a 30a charger with a 10 foot run (roundtrip) which means 5 feet of wire running between charger and batteries, at 3% voltage drop, the resulting wire should be 10 gauge. I do not know if this run should be calculated at 3 or 10% voltage drop but I was being conservative. For ****s and grins I plugged in 40a charger with a 15 foot round trip wiring and got 6 gauge wire for this run.

If you do rewire the boat use this calculator to determine the wire gauge for each run.

 

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Here you go photos of my current boat's electrical layout. This is not my work but what I am currently working with. It was I strongly suggest anyone with a 30+ year old boat inspect and consider rewiring a boat upon purchase or before installing new batteries. View attachment 136486 View attachment 136487 View attachment 136488 View attachment 136489




When I suggested inspecting the current wiring and look for 10 gauge, I was just throwing out a number of what he should look for to inspect for a current weakness in his current wiring. I was not suggesting he install 10 gauge when he rewires the boat. If he sees lamp wire instead of 10 gauge running from the charger to the batteries, suspect that as a potential problem.



Just to check my WAG I plugged a 30a charger with a 10 foot run (roundtrip) which means 5 feet of wire running between charger and batteries, at 3% voltage drop, the resulting wire should be 10 gauge. I do not know if this run should be calculated at 3 or 10% voltage drop but I was being conservative. For ****s and grins I plugged in 40a charger with a 15 foot round trip wiring and got 6 gauge wire for this run.

If you do rewire the boat use this calculator to determine the wire gauge for each run.

That’s a mess. I remember finding similar on my boat before I re-wired. I only had one previous owner. Looked like a spaghetti factory owned by Rube Goldberg.

Mainesail has good advice on fusing and wiring also
 

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That’s a mess. I remember finding similar on my boat before I re-wired. I only had one previous owner. Looked like a spaghetti factory owned by Rube Goldberg.

Mainesail has good advice on fusing and wiring also
This my 4th boat rewire in 20 years, 3 in the last 4 years. It is why I tell people to inspect the condition of their wiring if there is a problem before adding new batteries or equipment. I have yet to open up the hood of a boat I owned and not see something like this. Even if everything looks good there might be one circuit added by one of the owners who buys their connectors from Harbor Freight and uses lampwire and pliers to build the circuits.

The last one was recent and much bigger so I am current on all of Mainesail's techniques. It is not as bad as it looks because the system is so simple. Since I will be brining in power from the stern from alternator and a small solar panel, I will need to order #6 cable, PV cable and all the right sized rings. I will also need to add a lug crimper to my tools. I figure 2-3 days work, if I take the afternoon off to sail each day. The hardest part is logistics.

My biggest stumbling block, is my mast appears to be sans lights of any sort, although there are switches and looks like wires in place. That will probably be a spring project.

One more picture to share.
136491
 

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There should only be a single House bank, if at all possible, even if there are multiple paralleled sub-banks in different locations, the should be connected into one functional bank at all times

other than for testing and maintenance.

Shallower DoD% averages lead to longer bank life

with a bigger bank you'll be drawing it down less as a % of discharge and the bank will last longer.

Plus your overall effective Ah capacity will be higher with a single larger bank compared to the same load rates rotated between smaller split banks.

See Peukert Effect
 
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