Poke holes in my wiring plan

[sailingunity]

First of all thanks everyone for your replies I truly appreciate the advice. This is the plan from Maine Sail that I was following. I'm honestly kind of neutral on whether or not to run the starter and windlass off the house bank and have a "reserve" battery instead of a dedicated start battery, but I already have 3 holes in my bulkhead and 3 1/2/off/both switches, so I was leaning toward this arrangement.

[sailingunity]

I could run the #2 post from the main switch to the C post of the start / reserve switch and it would function the same as an on/off switch, right?

[guyrj33]

Is your shunt large enough to handle the current load from the starter?

If not you might want to move the starter negative lead to the other side of the shunt.
Then the shunt will only be measuring the house bank.

[mitiempo]

Originally Posted by sailingunity

If the engine starter is already on the load side of the shunt, why also wire the batt negative there as well? Wouldn't that effectively bypass the shunt?

You want to bypass the shunt with the start battery. Otherwise - as drawn - it will be included in the measurements of the battery monitor. You will never get an accurate measurement of the status of the house bank.

Start battery should be wired to starter only through the switch. Run the windlass from the house bank - the bank that receives the charge sources. The ACR takes care of the start battery.

[stormalong]

Originally Posted by sailingunity

Yep here's the original article that I found but it is pretty much identical to the other one. The reason I went with the terminal block instead of the last configuration they show as being "ideal" where the batteries are jumpered is because their example is 4 batteries, and I'll have 5, so i wasn't quite sure how that would translate to ensure even charging.

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

The author's examples are for very high current loads. Loads that high won't be happening on your house batteries. Charging currents, especially at battery float are very small and the resistances would be insignificant. I also question the reference to the internal battery resistance because that resistance is not part of the paralleling wiring.

I have three pairs of T-105s for my house bank. I replaced them this past spring after nine or ten years - a good run for a set of batteries. I do not think the way they were wired had any detrimental effect on them.

[smac999]

Originally Posted by guyrj33

Is your shunt large enough to handle the current load from the starter?

If not you might want to move the starter negative lead to the other side of the shunt.
Then the shunt will only be measuring the house bank.

it needs to be moved anyways. I already told him that. if he wants to measure both banks he needs 2 shunts. his drawing is wrong as one shunt is trying to measure both banks which will not work.

[smac999]

This is how I would wire the two 1, 2, all switches.


edit, that's anoying, it's right up on my phone

[sailingunity]

The shunt is pretty large, but I'll move the starter ground to the other side of the shunt to keep the readings correct.

I suppose you are right that we don't typically have huge loads on the batteries. Intermittently an appliance in the galley that pulls 100 amps out of the batteries via the inverter (we have an electrical kettle). We also have a 12V watermaker that pulls 30 amps or so, but it would be smart to run that while solar input is high. The windlass would generate a pretty high load, but the engine would typically be running at the same time so it wouldn't be a big load on the batteries.

Thanks for the diagram!

[sailingunity]

Originally Posted by stormalong

The author's examples are for very high current loads. Loads that high won't be happening on your house batteries. Charging currents, especially at battery float are very small and the resistances would be insignificant. I also question the reference to the internal battery resistance because that resistance is not part of the paralleling wiring.

I have three pairs of T-105s for my house bank. I replaced them this past spring after nine or ten years - a good run for a set of batteries. I do not think the way they were wired had any detrimental effect on them.

Are you saying that while bulk charge might results in some uneven charging, once it kicks into float mode they would equal out? Looking at the price of bus bars, I'd like to see if I can skip that!

Any recommendations for a fuse? Should I use those MRBF fuses, one for each battery at say 80 amps each (400 total), or go with a single 400 amp class T?

[millsie]

Overall concept works ,
cable - bigger is better.
slowly catches monkey Enjoy.

[mitiempo]

Originally Posted by sailingunity

Any recommendations for a fuse? Should I use those MRBF fuses, one for each battery at say 80 amps each (400 total), or go with a single 400 amp class T?

One fuse is sufficient for the whole bank. 400 amps is not needed though. Assuming 2/0 wiring I would fuse at 250 or 300 with a MRBF terminal fuse.

[stormalong]

Originally Posted by sailingunity

Are you saying that while bulk charge might results in some uneven charging, once it kicks into float mode they would equal out? Looking at the price of bus bars, I'd like to see if I can skip that!

Any recommendations for a fuse? Should I use those MRBF fuses, one for each battery at say 80 amps each (400 total), or go with a single 400 amp class T?

Sailingunity: The best that I can do is relate my setup. As I said earlier, I have three pairs of Trojan T-105s in series-parallel for 660 amp hours for my house bank. The batteries are paralleled using 1/0 jumpers. The power is drawn from the bank using 2/0 cable. Off hand I could not tell you if the 2/0 is connected to an end set of batteries or the center set. The 2/0 goes to an on/off switch and then to a bus bar with multiple taps for the battery loads. Each individual load has an appropriately sized circuit breaker - they range from 25 amps for the ham radio to 140 amps for the windlass.

Bus bars are expensive and are designed for the mass market. They often do not satisfy my needs so I make my own. There are multiple sources for copper bars. One that I recently bought from is onlinemetals.com. I use stainless steel bolts. Before everyone jumps on me I always put the terminal lugs directly against the copper and only use washers under the nut and the head. Copper bar isn't cheap but is is a lot cheaper and, by my choice, thicker than most commercially made bus bars.

If your batteries are physically side by side and they have threaded stud posts you could do both bus bars and jumpers in one neat package. Buy two 1/4 inch by 1 inch copper bars long enough to connect all of the positive and all of the negative terminals together. Drill holes spaced for each stud. I would also put heat shrink tube over each bar with cutouts for each stud. Considering the cost of heavy wire and terminals this may be cheaper - it is definitely neater.

I like neat wiring. That is part of why I say use jumpers rather than bus bars. I have been asked many times to help other cruisers with wiring issues and have seen a lot of rats nest wiring. Many times done by "professionals". With sloppy wiring the biggest problem is just figuring out what's what.

And to answer your first question last all I can say is that I am happy with my set-up. The batteries get bulk charged from the alternator when the engine is running and get topped off by 390 watts of solar. I have not measured individual current draw on the batteries - it is a big bank for my loads so all I can say is that this is what I have and what I have evolved the electrical system into over the last 29 years of owning this boat.

PS. As a past full time live aboard and full time cruiser I have spent a lot of time fine tuning my boat. Some of these systems have been redone multiple times until I was happy with them. I can truly say: I have fixed my boat in exotic ports all over the world.

[rgleason]

That link is good, I guess I was thinking of this one
Smartgauge - Interconnecting batteries.

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank



Starter on the load side of shunt is fine if the shunt is rated for it.

Originally Posted by sailingunity

The batteries are wired to a bus bar like that based on a link someone referenced on here saying that, especially in banks with an odd number of batteries, the middle battery could get less charge due to resistive losses in the connections.

Also the way the switches are wired came from Maine Sail's post here: https://forums.sailboatowners.com/in...usings.137615/ How should they be wired differently?

If the engine starter is already on the load side of the shunt, why also wire the batt negative there as well? Wouldn't that effectively bypass the shunt?

[sailingunity]

Yep that's the link I was looking for earlier! Although, I'm not quite sure how I would wire 5 batteries using that bottom configuration, I don't think it would work. The top configuration with a bus bar would work. I like the idea of the solid bar between battery posts as suggested by stormalong, and would definitely be neater and simpler to install (read: not have to cut and crimp 8 short connections to each of the batteries)

The reason for the 400 amp fuse on the bank is that the victron 3000 charger/inverter requires a 400 amp fuse. It also specifies to use 2 - 1/0 cables. Even though, by my calculations, it should only ever pull 234 amps at the most (3000/12.8), and 99% of the time we probably wouldn't even need that. But it didn't seem to make sense to fuse the inverter at 400 amps and the bank for 300 amps.

If the starter is on the load side of the shunt, the battery monitor should be programmed include the AH's of the starter battery too right?

[sailingunity]

Look at thta, same website you mentioned also sells tinned copper bar!

https://www.onlinemetals.com/en/buy/...edge/pid/23802

Suspect that would be better than using untinned copper? Strange that it appears to actually be cheaper than plan copper.

Mike