Wiring solar and ACR’s

[DArcy]

I inherited the po’s electrical nightmare, trying to get everything to code. It is a 51 years old boat so a lot has been done in the past years

You are in good company @fred1diver. The DC wiring in my boat was horrendous after 38 years and multiple POs with questionable electrical knowledge modge-podging it together with very scary bits and scraps of wire. This is just some of the mess I pulled out.

This is one of the more offensive areas I had to clean up

 

[jviss]

The radio in the diagram is actually the memory for the automotive stereo. The VHF is powered through the DC distribution panel just like most other DC loads. As mentioned above, I can run the house DC off the starter battery if I need to by switching to Both.

Ah, gotcha! I have a similar wire for my entertainment radio.

I have the same setup. The only weak part is that if the house bank fails catastrophically, and you're running everything off the engine starting battery, you can't charge it with the engine since the alternator output is connected to the house bank. This bothers me!

 

[DArcy]

Ah, gotcha! I have a similar wire for my entertainment radio.

I have the same setup. The only weak part is that if the house bank fails catastrophically, and you're running everything off the engine starting battery, you can't charge it with the engine since the alternator output is connected to the house bank. This bothers me!

I would have to physically disconnect the house battery cable to be able to run off the starter battery. I did think about putting a disconnect on the house bank cable and I may still do that at some point, but it is easy access so it would not be hard to just pull a cable off.

 

[fred1diver]

You guys lost me here, I will try to map out my existing system and come back with it to see how and where to install the m-acr

 

[jviss]

I would have to physically disconnect the house battery cable to be able to run off the starter battery. I did think about putting a disconnect on the house bank cable and I may still do that at some point, but it is easy access so it would not be hard to just pull a cable off.

Unless I misunderstand what you're saying, to "run off the starter battery," i.e., to power your D.C. distribution panel from the starter battery, you need only to switch to "2" and "ON." To charge the starter battery in this configuration, yes, you'd have to move the alternator cable.

I also just noticed you have the fridge connected directly to the house bank. And, with no low voltage disconnect. Why is that?

 

[jviss]

You guys lost me here, I will try to map out my existing system and come back with it to see how and where to install the m-acr

@DArcy 's beautiful diagram can be difficult to follow. Here's a sketch I made on a napkin during a technical conference about 20 years ago when I first came upon this concept rather than the ancient practice of alternating house batteries daily; it's essentially the same configuration as D'Arcy's:

CB = circuit breaker
A = alternator
House = house battery bank
Engine = engine starting battery
S = starter
SW = engine disconnect switch
Echo charger = echo charger
The dotted line box outlines the 1/2/Both/Off switch (switch positions should be self evident).

Your m-acr would replace the echo charger.

(I have recently changed this so the echo charger is powered not directly from the house but from the panel side of the circuit breaker.)


Normal operation is "1" and Sw. = ON (closed).
Faulty house bank -> "2" and ON;
Faulty engine battery -> BOTH and OFF;
Faulty echo charger (or m-acr) -> BOTH and ON (to charge the engine battery).

(I think that's correct! Others can check me. It's been my intention to write a simple user manual for the boat and keep it in an obvious place, so if others use the boat, or I'm incapacitated they can look up what to do, and how to recognize and respond to faults.)

 

[DArcy]

Unless I misunderstand what you're saying, to "run off the starter battery," i.e., to power your D.C. distribution panel from the starter battery, you need only to switch to "2" and "ON." To charge the starter battery in this configuration, yes, you'd have to move the alternator cable.

I also just noticed you have the fridge connected directly to the house bank. And, with no low voltage disconnect. Why is that?

If I wanted to run the house systems off of the starter battery I would disconnect the house battery cable from the battery and switch to Both. This would allow charging and use of the starter battery.

You are correct, I do not have a low voltage disconnect on any of the Always On circuits which I really should. In practice I have found the solar panels more than adequate for keeping up with the always on demands so I have not added a low voltage disconnect.

 

[jviss]

If I wanted to run the house systems off of the starter battery I would disconnect the house battery cable from the battery and switch to Both. This would allow charging and use of the starter battery.

Ah, I see. Would be nicer to have a switch, like the engine battery switch. Or maybe a 1/2/B/OFF switch for the alternator (with a lockout so it doesn't get moved while the engine's running).

You are correct, I do not have a low voltage disconnect on any of the Always On circuits which I really should. In practice I have found the solar panels more than adequate for keeping up with the always on demands so I have not added a low voltage disconnect.

I see. Yes, a LVD has been on my drawing board for years and I haven't gotten there yet. I even had a plan for a DIN rail behind the DC panel with adjustable LVDs for various things - shedding loads in order of less criticality as the battery voltage dropped.

 

[DArcy]

I even had a plan for a DIN rail behind the DC panel with adjustable LVDs for various things - shedding loads in order of less criticality as the battery voltage dropped.

That is much more ambitious than I would do but sounds like a fun project for an Arduino

 

[jviss]

That is much more ambitious than I would do but sounds like a fun project for an Arduino

No Arduino necessary! I found small, programmable LVDs with 20A relays on eBay for under $8!

XH-M609 12-36V Battery Low Voltage Disconnect Protection Module DC Output LED US

They don't exactly fit the DIN rail carriers I bought, but can be made to fit.

Rod (MaineSail) balked when I mentioned this previously, as they are not "marine" components, but then, virtually non of the components in my other marine components are marine components.

 

[DArcy]

Thanks for the link @jviss , I just ordered one
I have a 15A fuse in line with the AO Bus 2 which the fridge is on so I will just put it there. I'll work out an enclosure for it that I can 3D print for mounting.

 

[jviss]

Thanks for the link @jviss , I just ordered one
I have a 15A fuse in line with the AO Bus 2 which the fridge is on so I will just put it there. I'll work out an enclosure for it that I can 3D print for mounting.

Awesome, glad I could be of some assistance. Note, I assume no liability! I'm an electrical engineer, but not a licensed P.E. or marine electronics practitioner.

There are others out there, in housings, such as this one:

CZH-LABS LVD Low Voltage Disconnect Module. (12V / 30Amp)

I also have a time delay that will fit on a DIN rail adapter, that can handle 30A. I want to use it for the bilge pump, to keep it running a bit after the bilge switch opens, or maybe to control one of those dry bilge systems, to keep the dry bilge pump running after the regular bilge pump turns off.

Build Your Own DIY Arid Bilge or Dry Bilge System

 

[fred1diver]

Still wondering aimlessly trying to grasp how to complete my system lol
Ok so both batteries are connected to an a-b-both switch.
The battery charger is connected to both batteries.
I still haven’t figured how the alternator is connected to everything.
From the C post on the switch everything is going to a bud and then to the breaker panel.
Need to figure out how to connect my MPPT and ACR to the system, will work on a diagram soon, too many things on the go at the moment

 

[JoeWhite]

Fred, I just added a solar panel with mppt charger.
It is simple, just connect the output of the charger to the shunt, you are done.
Then select ALL or your setting on your switch to combine all 3 bayteries.

 

[jviss]

everything is going to a bud

What does that mean?

 

[jviss]

Fred, I just added a solar panel with mppt charger.
It is simple, just connect the output of the charger to the shunt, you are done.
Then select ALL or your setting on your switch to combine all 3 bayteries.

What shunt? Which side? In my experience shunts for measuring battery activity are installed on the negative side of batteries. Connecting the charger output there wouldn't work, of course.

 

[fred1diver]

What does that mean?

Oops meant bus

 

[JoeWhite]

Jviss, connect the positive side of the charger to the positive side of the battery and the negative side of the charger to the shunt, not to the negative side of the battery. The shunt is connected between the negative side of the battery and the negative side of the house bus.
This connection will provide power to be used to charge the battery and power everything else.

 

[jviss]

The shunt is connected between the negative side of the battery and the negative side of the house bank

Either I just don't get it, or you are writing imprecisely. The negative side of the the battery is the negative side of the house bank, isn't it? Perhaps you mean between the battery and negative bus?

I know a little bit about this, have rewired two boats so far, one with solar.

 

[JoeWhite]

I just don't get it, or you are writing imprecisely. The negative side of the the battery is the negative side of the house bank, isn't it? Perhaps

Yes, that is what I meant, shunt goes between battery and the house bus. Thanks for noticing my inaccurate description.