Wire gauge question from alternator

[Speakrdude]

What guage wire should I use to charge batteries approx. 20' away from the engine bilge?

My set up is;

Located in Engine compartment-
Single engine, stater battery, house battery, A-B-Both battery switch, (new ACR)

Located 20' away in the galley area-
2, AGM (sealed) batteries, on/off battery switch. (for AC via inverter) Dual bank battery charger installed here for charging while on shore power.

A wiring diagram to compare to my notes would be nice to.

Thanks,
Jim

 

[jaxnjil]

Re: Wire gauge question from alternator

i would say 12 gauge min. and 10 gauge better.

any thing with starter current passing out of battery at least ott

just redid all battery wire on our boat and for life of me cant rember if i ran 1-ott or 2 ott

 

[ENSIGN]

Re: Wire gauge question from alternator

I think I would use at least a #8 cable with a battery isolator inline to prevent a draw on the foward battery.Sorry,I'm not sure how to draw a diagram on the PC.

 

[Speakrdude]

Re: Wire gauge question from alternator

If your using windows, go to accessories, and look for "Paint". Draw all you want but when your done, save as a .jpg file and it will transmit much faster.

Jim

 

[ENSIGN]

Re: Wire gauge question from alternator

I'll give it a try,thanks,Ted

 

[bruceb58]

Re: Wire gauge question from alternator

I think I would use at least a #8 cable with a battery isolator inline to prevent a draw on the foward battery.Sorry,I'm not sure how to draw a diagram on the PC.

Why would you put an isolator in line with an alternator when it isn't necessary at all and will just drop the voltage?

Do NOT add an isolator in-line. If you are going to add anything, add an ACR like you are already doing now. You can just put it inline between the alternator and the 2 batterries if you like.

 

[Texasmark]

Re: Wire gauge question from alternator

House NM has probably the lowest temperature tolerance of available wiring and #10 is coded up to 50' (as I recall) for 30 amperes continuous. Like it runs probably 90% of the clothes dryers in the US and they are rated for a 30 ampere service.

The allowable voltage drop at that load is a few volts which doesn't make much difference when house input power could be 110-124 at different locations around the country at different times.

But, with a 12v system, a few volts can wipe you out, course you said 20', not 50 so that gets you down to 1v drop and when the battery(ies) move into the full charge region, the charging current drops off so the voltage drop essentially disappears.

I think #8 is good for 50 amps under the above circumstances which should be more than adequate as Ensign mentioned possibly the better choice, beins you are talking about an automobile type engine (with a high output alternator) on a larger boat with living accommodations.

My 2c,

Mark

 

[fishrdan]

Re: Wire gauge question from alternator

Here's Blue Sea's wiring diagram for an ACR, though it's not a perfect fit in your situation since you have 3 batteries. http://bluesea.com/files/resources/sales_sheets/6838.pdf

If you are OK with flipping the "galley" battery switch from 1-2-BOTH to charge the AGM batteries, and then again while on the hook to use only 1 battery at a time, 1 ACR will work, but it seems like a PITA to me. The problem I see with 1 ACR charging the 2 AGM batteries (and the battery switches you mentioned) is that you will need to wire the AGM batteries in parallel to charge them both "automatically",,, but this will defeat the battery switch in the galley. Either that or you will have to remember to flip the galley's switch to both while motoring, but again that seems like a PITA. The only way I can see charging each AGM battery automatically, while switched off, is to use 2 ACR's, 1 for each AGM battery.

For wiring, I would run heavy gauge battery cable to the AGM batteries and switches so you can start the boat off the AGM batteries if needed. There are a couple ways of wiring the switches, depending on your needs, but here's 1 way

- Heavy gauge battery cable from batteries to switches and engine.

- In the galley, connect 2 ACR's to the battery switch's common post and then over to post #1 and #2 using 10-8ga wire. (if there is such a thing as an ACR with 2 switched outputs, use 1 of those)

In this scenerio when you flip the engine's battery switch to both it will connect the engine to the start battery and galley battery switch, then when you start the engine the AGM batteries will charge. While on the hook, flip the engine's battery switch off and you can run your galley loads off the AGM batteries, selectable by the galley's battery switch. If your engine battery dies, switch the engine battery switch to #2 and the galley switch to the best battery and start the engine.

I guess another way to wire it would be to place the ACR on the engine battery switch's #2 post and then run 8-6 gauge wire to the galley battery switch and AGM batteries. But then the only thing the AGM batteries would do is run galley loads, they wouldn't be able to start the engine in an emergency situation when the engine battery is dead and you have to start the engine NOW! Be aware that there is a possibility of fire if connecting thin gauge wire (not battery cable) between the switch and batteries, and then trying to pull a high current load down the wire... IE: trying to start the engine with the AGM batteries,,, by manually locking the ACR(s) closed. If your ACR does not have the manual lock feature or you don't wire it up, I don't think you will have a problem running 8-6ga wire for the AGM batteries. (Personally, I wouldn't connect a battery to a battery switch with 6-8ga unless it was protected with a breaker)

{EDIT: I didn't notice you had a house battery in the stern (1 more battery) so I edited my post to make some kind of sense... I guess you don't have to worry about redundancy for the start battery}

 

[Don S]

Re: Wire gauge question from alternator

1. The size wire you use, is going to depend a lot on the size of alternator you have. If you have a 65A alternator and almost dead house batteries, you are going to need a lot more than 8ga. wire 20 feet away.
2. You need to get rid of that Off-1-Both-2 switch. There are switches specially designed for use with ACR's see below.
3. You will need battery cables going from the house batteries to the battery switch in the engine compartment if you plan on using the house batteries to start the engine should the starting battery go bad.

Here is some info you really need to read. Especially page two of this one.
http://bluesea.com/files/resources/...g_battery_switching_and_charge_management.pdf

This should help you determine wire size for about anything.
http://beta.circuitwizard.bluesea.com/#

In general, here is a lot of information on switchs, circuit breakers, buss bars, ACR's about anything electrical.
http://bluesea.com/resources/2

 

[bruceb58]

Re: Wire gauge question from alternator

I am not sure how you have your 2 batteries hooked up that drive your inverter but this is what I would add. The red lines are your new wires.

Doesn't have to be exactly as I drew it. The last ACR just needs to be between the two AGM positive terminals. You can then have the first ACR have a disconnect switch that keeps the alternator from charging the AGM batteries if desired. Of course if the two AGM batterries are wired in parallel, you just need an on/off switch and one ACR but you wouldn't need a dual charger. Let me know if this is your configuration and I can change the drawing.

 

[ENSIGN]

Re: Wire gauge question from alternator

Really sorry for the confusion guy's,I should have said ACR instead of the isolator

 

[Don S]

Re: Wire gauge question from alternator

Bruce, as I see your drawing, the ACR on the start/house batteries will do nothing. Once you turn the battery switch to both, your automatically charging both batteries.
What he needs to do is replace the 1/2/Both/off battery switch to the Bluesea dual circuit battery switch. It would then isolate the two systems, but still allow the batteries to be combined manually in case the starting battery was dead.
Then, just add a second ACR between the house battery switch terminal and the Inverter on off switch. This would allow the inverter batteries to charge as soon as the house battery was charging.

 

[Speakrdude]

Re: Wire gauge question from alternator

Plain, easy and simple. I love it. Thanks for everyone's input.

Don as a side note, This is for Bayliner 2750 #2, which is sold and leaving next week, if the ice has thawed enough at the marina (yes, we're in the south??) Have 2 Sea Ray 300's I am working on now. One has inboards, one has I/O's.
A long way from the first backwards boat huh?

lol

Jim

 

[Don S]

Re: Wire gauge question from alternator

I always thought ole blue would have been enough for you. But Nooooooo LOL

Ever thought of just going outside and beating yourself with a stick? All the pain, and it doesn't cost anything

 

[bruceb58]

Re: Wire gauge question from alternator

Bruce, as I see your drawing, the ACR on the start/house batteries will do nothing. Once you turn the battery switch to both, your automatically charging both batteries.

True but so will the "both" setting in the BluSeas Switch. I do like the Blue Seas switch since it allows you to switch the House loads off. The switch I had in there's only purpose was to switch to both in the case where you starter battery was dead. You would normally never leave it on both.

 

[Don S]

Re: Wire gauge question from alternator

True but so will the "both" setting in the BluSeas Switch.

It does not have a "Both" type position on it Bruce.
It works like 3 on/off switches. Let me find my drawing of my boat with the 3 switches. I did it before this dual circuit switch came out.
Be back in a bit.

 

[Don S]

Re: Wire gauge question from alternator

The switch I had in there's only purpose was to switch to both in the case where you starter battery was dead. You would normally never leave it on both.

The way you have your switch wired in the wiring diagram, you CAN NOT shut off power to the house without disconnecting the battery.

 

[Don S]

Re: Wire gauge question from alternator

The first thing one has to do is forget the name of the ACR, or battery combiner, or whatever the manufacturers call them. They are Voltage sensitive relays. Meaning the one side of the relay is sensing voltage to your main battery (start battery in this case) and the secondary side is sensing voltage from the secondary battery (House battery in this example)
When the engine starts and the voltage in the primary battery reaches 14V (Easy to type number for the example) and the secondary is less than 14V, the relay energizes. Which does nothing more than connects the two batteries together (combines them) and they equalize voltage and continue charging until the engine is shut off. When one side drops voltage below the other, the relay opens again. Now, no connection between the batteries.

Now lets look at the battery switch.

While it's hard to understand how they work by looking at them from the outside, the dual circuit battery switch from Bluesea, works like the three on off switches in the drawing below. The dual circuit switch (DCS) has only 3 positions. OFF, ON, and Combine. Off is obvious using the 3 switch system below, all 3 switchs are off.
When the DCS is turned to the on position, it's the same as turning the engine and accessory switches on. NOT the parallel switch it remains off.
Now, just follow the wiring when the engine starts, it will charge the starting battery only because the voltage sensing side of the ACR is attached to the starting battery. As soon as it sees the start battery is charged to a certain point, it closes and allows charging of the house battery.

Should the starting battery go bad, you can turn the DCS to the Combine position which should have the same size battery cables as the starting battery to start the engine.

Hope this makes some sense to anyone that reads it.

 

[bruceb58]

Re: Wire gauge question from alternator

The way you have your switch wired in the wiring diagram, you CAN NOT shut off power to the house without disconnecting the battery.

i agree with you. The BlueSeas is the better way to go.

It does have a "both" position except they call it "combine batteries".

http://bluesea.com/files/resources/sales_sheets/Dual_Circuit_Plus_Battery_Switches_(2,200 KB).pdf

 

[Don S]

Re: Wire gauge question from alternator

It's not a "Both" position, it only gets used in emergency.

On a normal 4way battery switch, when you put it to 1, you use battery 1 to power house and start.

when you go to position 2, you use battery 2 to power house and start.

When you go to both, you use both batteries to power house and start. They are not seperatied 1 battery for start and one for house.

On the Bluesea, in the normal position (ON) 1 battery goes to the starter, the other battery goes to the house. If you use up the house battery using the blender and stereo and lights, well. You are done, but you can still start the engine.
Sure you can turn it to combine, but now you will consciously kill your starting battery too.

The neat thing about the dual circuit switch is that it's a no brainer. You don't have to think about things like did I put it on 1 or 2 and sure hope I didn't leave it on Both. And if you don't have it on BOTH, you can't charge BOTH batteries.
With the dual circuit switch and an ACR, you turn it on and it keeps you out of trouble and you can always start your engine to get home.

PS: Bruce, this info is also for others that don't understand, not just you. You just happen to be the one that I get to explain it to.

I was looking for the link to that switch and couldn't find it. Thanks