Need a little Electrical advice

[croaker stroker]

I would like to hook up my winch battery so it will charge. My house battery is an AGM so they recommend not combining these with a lead/acid.

So, I think I need to parallel my winch battery to my start battery? I have read that the Blue Sea ACR is nothing more than an electric relay that combines two batteries. I don't think a battery isolator (diodes) will work with my ETEC EMM charging system and I sure don't want to blow that up again.

I could use a Perko battery switch and manually turn it on when I want to charge the winch battery.

They also make a switch/circuit breaker combo.

What would you do?

My#2 question is....

What size cable do I need from the start battery to the winch battery? Do I need a wire big enough to carry the load of the winch motor, or just big enough to handle the charging of the winch battery? 

[Diablo]

Ok I'll take a stab at first question.
I would use the house battery if that does not have the capacity for the winch and other loads then I would add a second AGM house battery in parallel. Having three separate battery systems becomes complicated.

[davidsea]

    If you can use a winch battery that is functionally identical to your start battery (same type, capacity and charging characteristics ) , they could both charge in parallel - but not while trying to charge the AGM house battery at the same time.  One way to wire this would be to use a 3-way battery switch  ( OFF- 1 -2 - BOTH) for your 2 existing batteries, and then parallel the winch battery with the start battery through an ON-OFF switch in the line to the winch.  If you did this, then you could run a much smaller cable forward to the winch, only large enough for the charge current.   HOWEVER, if you forgot to turn that switch OFF before using the winch, the smaller wire would turn into neon, trying to share the load from both both winch and start batteries.
   Probably not what you want to hear, but the simplest, most reliable solution would be to run 3 identical batteries, start and winch in parallel, with cables large enough to handle the current of both start and winch batteries running the winch, and both running the starter, as well.  With a 3-way, switching to 'BOTH' would give you the combined power of all 3 batteries to do whatever, and allow all 3 to charge at once when the main is running.   Unfortunately, this wouldn't work well unless all three batteries were identical.
    Personally, I'd run the winch off the house side rather than the motor side - you can always haul line by hand, but hand-starting a motor? no thanks...... m2c, but Dev probably has a better idea....

[DevMah]

Croaker

I have used magnum converters on RVs they allow one charge source for two different batteries, I have not used it for marine purposes, but may work for your needs. This unit is not a simple relay rather a electronic charger.


https://www.magnum-dimensions.com/sites/default/files/MagDocs/64-0019-ME-SBC-web.pdf

There is a 25A over current shut off built into the battery combiner.

Option 2 is a manual combiner switch with your wire size and fused/breaker rated  to your outboards max charging output. This fuse/breaker would trip if you accidentally left the combiner switch on while using the winch or cranking the motor.

It's always best to run identical batteries, this would give you the longest and best battery life and performance.


Dev

[croaker stroker]

Thanks guys.

How about running 4 awg from the winch battery to a circuit breaker with built-in switch near the start battery ?  I could leave the switch off unless the winch battery got low. That way, if the switch is accidentally left on, the wire would be adequate and protected by the breaker.

Although the two batteries are similar, I would not want to leave the them paralleled for long...Just don't feel comfortable with that.

One of these breakers came with the winch and it is pretty cool. I could purchase another one. (I'd use 60amp)

This project cost has been snow-balling.   

[Speyside]

What about using a DC-DC charger? Something like this...

https://redarcelectronics.com/products/20a-in-vehicle-dc-battery-charger-ignition-control

There are other DC-DC chargers out there too, this one is just an example.

[croaker stroker]

Thanks Speyside. I'll check those out.

[DevMah]

Thanks guys.

How about running 4 awg from the winch battery to a circuit breaker with built-in switch near the start battery ?  I could leave the switch off unless the winch battery got low. That way, if the switch is accidentally left on, the wire would be adequate and protected by the breaker.

Although the two batteries are similar, I would not want to leave the them paralleled for long...Just don't feel comfortable with that.

One of these breakers came with the winch and it is pretty cool. I could purchase another one. (I'd use 60amp)

This project cost has been snow-balling.   

Croaker


AWG 4 has a max capacity of 85 Amps, I'm not to concerned about voltage drop as it's primary use is for combined battery charging not load sharing.

You should be good to go...you could also install a ACR with a breaker and switch(the switch would be on the negative of the ACR and would toggle it on or off)

Dev

[DevMah]

What about using a DC-DC charger? Something like this...

https://redarcelectronics.com/products/20a-in-vehicle-dc-battery-charger-ignition-control

There are other DC-DC chargers out there too, this one is just an example.

IMO

This is the same as the magnum converter. (It's actually a dc charger)


Dev

[croaker stroker]

Thanks Dev.