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252,000+ Miles
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Discussion Starter #1
A-la RV/Boat style. Not using an isolator or fusable link. I already have an upgraded load boss 165amp alternator and I've done the big 3 upgrade so all my wires under the hood are 4ga. (Alt to Fuse Box, Fuse Box to battery, battery to body, battery to block, block to frame).

My plan is to run a Blue Sea Systems ML-ACR Automatic Charging Relay with Manual Control - 12V DC 500A PN7622 in order to give me the options I want. My question is, do I actually need the pair of ML series remote battery switches to go with it? I want to be able to bring the cranking battery in as help for the winch, as well as be able to jump the cranking battery of the deep cycles if I need to.

My original thought was just to drop a fuse between the alternator and the ACR before the deep cycle batteries, but I'm not sure that will give me the end result I am seeking. The secondary bank will run its own fuse box with the winch, offroad lights, 1800w inverter, etc. Running 1/0 for the entire kit.

Camping for 10 days in June with a 1yr old, need this up and running since we are tenting, and I need the bugs worked out.

Anyone have any experience wiring up boats or rv's with ACR's?
 

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252,000+ Miles
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Discussion Starter #2
Got a response, these guys are great.
Hello,

The 7622 ACR could be used to manually (through either the yellow knob on the top of the unit, or the remote control switch) combine your two batteries whenever needed. This could be when winching, or when needing to jump start from your house battery.

Beyond the manual combine feature, the primary function of an ACR is to automatically combine (parallel) batteries when a charging source is present, but leave them isolated otherwise. This means basically that if your engine is running, the ACR will automatically combine batteries so that they can both be charged from the alternator, and when your engine is shut off, the ACR will isolate them. This is accomplished by sensing battery terminal voltage to decide when to combine/isolate. If one or both of the batteries is at least 13.0V, the ACR will close (combine), after a short time delay for some hysteresis. Once combined, if voltage drops to 12.75V or below, the ACR will open (isolate).

I explain the combine/isolate functionality because you mention that you want the system to “recharge the operation battery first”. This is not strictly how an ACR is intended to operate. Frequently, there is a misconception that an ACR will decide how to “direct” charging current to one battery or the other, when in fact what really happens is that the ACR simply parallels the batteries for charging. Once paralleled, the batteries draw current as necessary from the charging source depending on their individual need.

I’ve linked some articles below that further explain ACR function:

Application Briefs - Blue Sea Systems

ACR Operation - Blue Sea Systems

Automatic Charging Relay (ACR) Explained - Blue Sea Systems

Regarding battery disconnect switches (remote or otherwise), they are not strictly necessary for operation of the ACR. They are a good idea for safety reasons on larger batteries/banks. In the marine world there is a regulatory issue, in that batteries greater than 800 CCA or 100 Ah are required to have battery disconnect switches installed. I cannot speak to automotive regulations.

Best regards,

Sam Schanken
Design Engineer
Blue Sea Systems
So, it looks to me like this is the way to go. No extra parts needed since it's not waterborne. Makes it expensive, but not unreasonably so for the functionality and peace of mind.

Adding to the build plan...
 

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252,000+ Miles
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1,316 Posts
Discussion Starter #4 (Edited)
Spoke to Sam again yesterday about a few details, when doing this, don't mix Gel Cell batteries with AGM or plate! as they don't like each other due to different ideal charging voltages (gel likes 13.8, AGM and plate like 14.5).

These guys know their stuff. I was turned on to them after seeing how bulky isolators are to work with and how they really weren't what I wanted.
 
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