Please critique my wiring diagram.

[er9]

I'm going to attempt to attach two images, the first is the way my boat is currently wired and the second the way i intend to wire it.

My goals are to add a brand new free to me FLA battery to my chronically underpowered house bank. To re-route the charge circuit to a common charge bus (directed to house bank). To add an ACR between the banks and to add fusing (currently there is none).

This isnt intended to be a major wiring upgrade, that will happen next year, this is more of a quick and dirty upgrade in the interim just to add the new FLA, make charging a little more efficient and safer.

My main concerns/questions are if i missed anything? Will my ancient charger work safely with the way i intend to re-wire things and is my ground circuit safe/acceptable?

Apologies for the Crayola drawing.

If its not obvious, the small square boxes with #'s in them are the fuse sizes i intend to add inline on those wires. Also i will not be touching the AC side at all.

[er9]

Updated pics

[wingssail]

Originally Posted by er9

I'm going to attempt to attach two images, the first is the way my boat is currently wired and the second the way i intend to wire it.

My goals are to add a brand new free to me FLA battery to my chronically underpowered house bank. To re-route the charge circuit to a common charge bus (directed to house bank). To add an ACR between the banks and to add fusing (currently there is none).

This isnt intended to be a major wiring upgrade, that will happen next year, this is more of a quick and dirty upgrade in the interim just to add the new FLA, make charging a little more efficient and safer.

My main concerns/questions are if i missed anything? Will my ancient charger work safely with the way i intend to re-wire things and is my ground circuit safe/acceptable?

Apologies for the Crayola drawing.

If its not obvious, the small square boxes with #'s in them are the fuse sizes i intend to add inline on those wires. Also i will not be touching the AC side at all.

You will get a lot of disagreement about my proposal but I believe it gives you better flexibility.

• You can supply the DC Dist and the Pos Bus with either battery
• You can start the engine with either battery
• You can charge either battery even without the ACR
• In marginal situations when you batteries are low you can use "Both" to start the engine
• When you switch the Batt SW to OFF, everything is off
• If you get solar or wind, wire it to the Pos Bus

EDIT: Wire the starter to the Pos Bus, then you get a fuse on that line.

[Kelkara]

Just a couple of comments on fuses...


- 300A is a mighty big fuse for such little batteries, what size wires are you using? They had better be big. What kind of DC loads do you have?
- The fuse from the house bank should be at the battery end, not the bus end (unless the wire is very short).
- The 50A battery charger cable is currently only protected by a 300A fuse ... unless this is also a huge cable it needs a separate fuse near the bus.
- The 300A fuse on the line from the pos bus to the 12B switch is superfluous (already has a 300A fuse between it and battery.)
- The 300A fuse on the distribution line is also superfluous for the same reason ... but if the cable to the panel is a smaller gauge, then there should be a smaller fuse here. [Edit... I take this back, with the switch on Both, there is potentially 600A here ... but do you really need 300A at the panel?]
- The ACR (BlueSea ones at least) require a fuse in the negative line.

[er9]

Originally Posted by Kelkara

Just a couple of comments on fuses...


- 300A is a mighty big fuse for such little batteries, what size wires are you using?

i will triple check but it looks to all be original 2/0.

They had better be big. What kind of DC loads do you have?


very small DC loads. Boat is very bare bones at the moment, just LED's
and fresh water pumps mainly, chart plotter, nav lights. I have been doing
ok on a single 85 Ah battery to give you some idea, but i charge it a lot. I
dont have energy budget done yet, not enough to worry about at the
moment. Mainly was sizing according to the wire.

- The fuse from the house bank should be at the battery end, not the bus end (unless the wire is very short).

Noted. it will be rather long, maybe 4-6ft.

- The 50A battery charger cable is currently only protected by a 300A fuse ... unless this is also a huge cable it needs a separate fuse near the bus.

Thank you, missed that, adding 100AMP fuse

- The 300A fuse on the line from the pos bus to the 12B switch is superfluous (already has a 300A fuse between it and battery.)

i meant to delete one of those and forgot to.

- The 300A fuse on the distribution line is also superfluous for the same reason ... but if the cable to the panel is a smaller gauge, then there should be a smaller fuse here. [Edit... I take this back, with the switch on Both, there is potentially 600A here ... but do you really need 300A at the panel?]

Noted, i was sizing that fuse to the largest potential wire and load that
might be pushed through that wire to the panel. the 1,2, off switch is rated
for 350 amps and each post can receive that many amps but im open to
opinions/ discussion/ education on this. The largest combined draw at the
panel will ultimately be a much smaller draw but i dont have those
numbers yet. It looks like the panel wire currently is 1/0.

- The ACR (BlueSea ones at least) require a fuse in the negative line.

Good to know. I dont own it yet so wasn't aware of that. Thank You.

will update drawing and re-post it.

[er9]

Originally Posted by wingssail

You will get a lot of disagreement about my proposal but I believe it gives you better flexibility.

• You can supply the DC Dist and the Pos Bus with either battery
• You can start the engine with either battery
• You can charge either battery even without the ACR
• In marginal situations when you batteries are low you can use "Both" to start the engine
• When you switch the Batt SW to OFF, everything is off
• If you get solar or wind, wire it to the Pos Bus

EDIT: Wire the starter to the Pos Bus, then you get a fuse on that line.

How would the house bank get charged, back through the common post?

[rgleason]

Given this configuration by Wingsail,

Is the ACR really needed, since switching to Bank #2 Reserve and charging is possible? It does require being more mindful about the battery state.

Since you are able to switch to OFF (somehow I had not realized this previously) I believe you want a 3-way switch which also has an Alternator field disconnect, otherwise you or your wife will inadvertantly switch the Banks through the OFF switch while the alternator is charging and potentially fry the alternator. Using a Zap Stop will also help.

I do like this setup. Since there is an Off switch you might not need an Engine room Emergency Alternator disconnect, but I think it would be better because you do have a charger, and it would be safer!

[er9]

Originally Posted by wingssail

You will get a lot of disagreement about my proposal but I believe it gives you better flexibility.

• You can supply the DC Dist and the Pos Bus with either battery
• You can start the engine with either battery
• You can charge either battery even without the ACR
• In marginal situations when you batteries are low you can use "Both" to start the engine
• When you switch the Batt SW to OFF, everything is off
• If you get solar or wind, wire it to the Pos Bus

EDIT: Wire the starter to the Pos Bus, then you get a fuse on that line.

Thanks Wingsail. im still trying to completely wrap my head around your proposed diagram.

from my view so far though the only advantage i see is that the alternator is 100% off when the switch is in the OFF position, meaning i dont need a service interrupt switch. the disadvantages seem to be i can fry my alt (easily remedied) and that i have to manage the charging for both banksindividually (not the end of the world).

as far as can tell though my proposed wiring solution can also do all of the same things you noted above although i would need to rely on the ACR for charging the second bank. if it ever died i would loose charging to that bank. that being said i would have an sg-200 installed on both banks to keep an eye out for their charge state and health, although thats a future upgrade i admit.

forgive my current state of ignorance if im missing something obvious, you may have to elaborate a bit.

[wingssail]

Originally Posted by er9

Thanks Wingsail. im still trying to completely wrap my head around your proposed diagram.

from my view so far though the only advantage i see is that the alternator is 100% off when the switch is in the OFF position, meaning i dont need a service interrupt switch. the disadvantages seem to be i can fry my alt (easily remedied) and that i have to manage the charging for both banksindividually (not the end of the world).

as far as can tell though my proposed wiring solution can also do all of the same things you noted above although i would need to rely on the ACR for charging the second bank. if it ever died i would loose charging to that bank. that being said i would have an sg-200 installed on both banks to keep an eye out for their charge state and health, although thats a future upgrade i admit.

forgive my current state of ignorance if im missing something obvious, you may have to elaborate a bit.

Originally Posted by er9

Thanks Wingsail. im still trying to completely wrap my head around your proposed diagram.

from my view so far though the only advantage i see is that the alternator is 100% off when the switch is in the OFF position, meaning i dont need a service interrupt switch. the disadvantages seem to be i can fry my alt (easily remedied) and that i have to manage the charging for both banksindividually (not the end of the world).

as far as can tell though my proposed wiring solution can also do all of the same things you noted above although i would need to rely on the ACR for charging the second bank. if it ever died i would loose charging to that bank. that being said i would have an sg-200 installed on both banks to keep an eye out for their charge state and health, although thats a future upgrade i admit.

forgive my current state of ignorance if im missing something obvious, you may have to elaborate a bit.

Yes, I guess you can do everything with your original "new" diagram. I didn't see it all when I responded. I just preferred the simplest solution. Others may disagree.

Regarding the "frying" of the alternator: your alternator field source should be supplied by the ignition swith via the pos bus or DC dist panel (or, for example, if your alternator is controled by a smart regulator). When you (IF you) turn to "off" while the engine is running, supposedly the regulator will shut down and field supply will be cut off and the alternator will shut down, preventing the diode blast when there is nowhere to go.

I myself am skeptical about this sequence of events, but in 34 years we have never switched to "off" while the engine is running on our boat to test that theory. In any event, we have "two" spare alternators. If Wifey or anyone does that dastardly deed, we'll change alts post haste and be back in business.

[er9]

Originally Posted by wingssail

Yes, I guess you can do everything with your original "new" diagram. I didn't see it all when I responded. I just preferred the simplest solution. Others may disagree.

Regarding the "frying" of the alternator: your alternator field source should be supplied by the ignition swith via the pos bus or DC dist panel (or, for example, if your alternator is controled by a smart regulator). When you (IF you) turn to "off" while the engine is running, supposedly the regulator will shut down and field supply will be cut off and the alternator will shut down, preventing the diode blast when there is nowhere to go.

I myself am skeptical about this sequence of events, but in 34 years we have never switched to "off" while the engine is running on our boat to test that theory. In any event, we have "two" spare alternators. If Wifey or anyone does that dastardly deed, we'll change alts post haste and be back in business.

good stuff....thank you. wow! you and your wife have had/ are having quite the adventure. hats off to you, i hope to follow in your footsteps soon.

[rgleason]

One other thing to consider, doesn't Wingsail's configuration have the Alternator more directly connected to the DC Panel rather than through a moderating battery, so your more sensitive and important DC Equipment may be subjected to greater variation and possible spikes.

Also I have had a Zap Stop on our 90-65a alternator for twenty years, and in that time I have no doubt someone, including me, has turned the switch through OFF while the engine was running. Since this alternator is not very high amperage, I do not know if the Zap-Stop was key to keeping the alternator running and undamaged.

Devices to Protect the Alternator from spikes
Balmar TSP-12 transient spike protector for 12 voltsBalmar TSP-24 transient spike protector for 24 volts

This MaineSail statement is worth reading, Zap Stop -Fact or Fiction post 40

So, alt output and sensing need to go to ideally go to the same bank otherwise you can run a risk of cooking one bank....

As always if you wire the alt direct to the house bank it should have a fuse as close to the battery bank as possible. I also install an engine room "service" switch for the alt output so when working on the engine the bank can be isolated. This switch is in the engine bay or hidden
elsewhere so "Uncle Bob" does not reach down and turn it....

Hellosailor down below that in the same thread, wrote about these diode devices:

"Yes, a continuous overload would blow up the diode, or any spike absorbing device. But we're looking to clamp transients that may be on the order of 1000V for a couple of microseconds, and a properly selected diode or other spike protection device should be able to take typically several hundred or thousand hits on that scale. They don't heat up and explode instantly, you need to keep the load on them way longer than one spike incident."

Since the most likely action is to turn through the "OFF" to charge the other bank perhaps, rather than just leave it on "OFF" with the engine running, in this case these devices are useful.

There are other clever devices for protecting the alternator.


https://livsailing.com/2019/11/04/pr...ng-to-lithium/



MaineSail thinks this is a good idea


Automotive Circuit Protection using Littelfuse Automotive TVS Diode

[er9]

Originally Posted by rgleason

One other thing to consider, doesn't Wingsail's configuration have the Alternator more directly connected to the DC Panel rather than through a moderating battery, so your more sensitive and important DC Equipment may be subjected to greater variation and possible spikes.

Also I have had a Zap Stop on our 90-65a alternator for twenty years, and in that time I have no doubt someone, including me, has turned the switch through OFF while the engine was running. Since this alternator is not very high amperage, I do not know if the Zap-Stop was key to keeping the alternator running and undamaged.

Devices to Protect the Alternator from spikes
Balmar TSP-12 transient spike protector for 12 voltsBalmar TSP-24 transient spike protector for 24 volts

This MaineSail statement is worth reading, Zap Stop -Fact or Fiction post 40
Hellosailor down below that in the same thread, wrote about these diode devices:
Since the most likely action is to turn through the "OFF" to charge the other bank perhaps, rather than just leave it on "OFF" with the engine running, in this case these devices are useful.

There are other clever devices for protecting the alternator.


https://livsailing.com/2019/11/04/pr...ng-to-lithium/



MaineSail thinks this is a good idea


Automotive Circuit Protection using Littelfuse Automotive TVS Diode

The nice advantage about wiring the alt to the 'always on' charge bus, that feeds the house bank is, you wont blow alternator diodes because the alternator will always be able to dump its output into the house bank, ie...no voltage spikes.

[rgleason]

Yes, that's right, but a backup might be good.

Also why are we so sure a small FLA 20ah tractor battery will take the BMS cutoff spike from an 80a alternator?

Can you provide some of the rational?
If the batt is too small the spike protector for 3$ will help protect electronics during the cutoff.

Would an AGM battery work just as well?

[mitiempo]

The last 3 posts by rgleason do not seem to relate to this thread at all.

I would wire it differently.

There should be a positive charge bus. All charge sources go to this bus - alternator, Raritan charger, any future sources such as solar. The house bank positive goes to this bus. From this bus a wire goes to position #1 on main switch. Another wire from this bus goes to the ACR and the other side to the start bank.

Start bank positive to #2 on the main switch.

Common on main switch wired to both starter and distribution panel.

No worry about the alternator at all as it is connected to the house bank at all times.

Appropriate fusing of course.

[waterman46]

Originally Posted by wingssail

Regarding the "frying" of the alternator: your alternator field source should be supplied by the ignition swith via the pos bus or DC dist panel (or, for example, if your alternator is controled by a smart regulator). When you (IF you) turn to "off" while the engine is running, supposedly the regulator will shut down and field supply will be cut off and the alternator will shut down, preventing the diode blast when there is nowhere to go.
.

Without delving into all the details of OP's wiring diagram, I think the point about frying alternator diodes is directed at a theoretical situation where ALL battery banks might accidentally be disconnected from the alternator while engine is running. Quite different than simply turning off the engine ignition switch, which as you say will not harm the alternator.