Blue Sea ML-ACR Contra Switch, worth hooking up?

JCDriller

Adventurer
This may seem like a stupid question, but I just finished installing my second battery and blue sea ML-ACR in my 4runner. I didn't install the supplied contra switch because I can't think of a time when it would be a benefit to isolate the batteries or combine them via a remote switch. Honestly I hope to forget this system even exists while it runs in the background and if I'm winching or need to jump myself I can manually lock them together by turning the knob under the hood.

Is there some use I'm missing?
 

jeegro

Adventurer
If you wired your alternator to your starting battery and your vehicle electronics to your house battery and your house battery is low, the car might freak out about too low voltage. Nice to have the switch to manually combine them rather than wait the ~40 seconds for them to combine. Minor use case...

I installed mine simply out of completeness. It's a neat button after all.
 

dstock

Explorer
I really like the switch as the lights on it allow you to monitor that all is working correctly. Granted the solenoid makes a large sound when it connects, I like the peace of mind of visually seeing the system is working. Also, when something is wrong with the system, the lights on the switch flash alerting you to the issue.

I got in my vehicle on a rainy winter morning to discover my starting battery was dead, lights on switch flashed as soon as I started to turn the key. Was really nice to flip the switch to join the batteries from the driver's seat to be on my way.
 

Bbasso

Expedition Leader
I've yet to use mine as a jumper but being able to switch as needed is nice.
It's not difficult to, why not.

Edit: I have solar, so charging two starter batteries and two house batteries is handy with the press of a button.
 
Last edited:

Ds4x4

Observer
I installed mine. had same thought you did. The silverado's and alot of newer vehicles have adaptive charging systems that monitor voltage and vary the Alt output. if i leave my switch to auto, i find that the alt drops down to a lower voltage lower than the voltage required to complete the ACR circuit.. something like 13.3volts. so i use the switch to isolate the batteries/ I also have no real load on my 2nd batty at this time.
 

JCDriller

Adventurer
Well, you guys talked me into installing last night. No it wasn't hard, but now the engine compartment is a little more cluttered with wire loom... I do like that I know when it is open or closed, the LEDs are nice.

Did everyone use the Start Isolation? I wired it up, but don't love the button flashing for a couple minutes each time I start my engine and I'm not running anything sensitive so I may disconnect it. Thoughts?
 

dstock

Explorer
Well, you guys talked me into installing last night. No it wasn't hard, but now the engine compartment is a little more cluttered with wire loom... I do like that I know when it is open or closed, the LEDs are nice.

Did everyone use the Start Isolation? I wired it up, but don't love the button flashing for a couple minutes each time I start my engine and I'm not running anything sensitive so I may disconnect it. Thoughts?

I did not hook up start isolation.

The other nice thing about having the switch is I have my solar panel and solar charger hooked up to my aux. The panel pulls in enough power to for the switch to connect and charge both batteries, but flipping the switch on the console I can isolate the aux so it gets the full power of the panel, again, nice not to have to pop the hood.
 

JCDriller

Adventurer
I did not hook up start isolation.

The other nice thing about having the switch is I have my solar panel and solar charger hooked up to my aux. The panel pulls in enough power to for the switch to connect and charge both batteries, but flipping the switch on the console I can isolate the aux so it gets the full power of the panel, again, nice not to have to pop the hood.

That is the first good reason I've heard. Thanks!
 

DaveInDenver

Middle Income Semi-Redneck
I never connected the cab switch on my ML-ACR. To get my dual batteries running I made a hasty harness to ground the wire with the intention of someday finishing the system. That was 3, almost 4, years ago and just haven't missed it. A couple of times I manually disconnected the two batteries using the manual override on the isolator itself for a deep discharge recovery. Otherwise it's outta sight, outta mind.

Reason for me, nowhere convenient to put it and generally lack of effort to run wires. I also do not have solar and my shore charger is more than capable of dealing with the combined capacity of my two batteries.
 

vladig

Observer
Just to add another reason to have it.
If there is ever an issue with aux batt the LED's on the switch will start blinking to let you know there is a fault condition.

And its just cool looking :)
 

toyick

I build Boat Anchors
does anyone use the start isolation? i dont for see ever really needing it? anything im over looking?


blahhhhhh
 

toyick

I build Boat Anchors
Start isolation is useful if during battery combined times one has sensitive electronics running on the house side of the system.
Rapid voltage drop & subsequent rise whilst starting the motor may damage, crash, reboot, sensitive appliances.

yeah i know that? but any list of "appliances" that may be effected?


blahhhhhh
 

crazysccrmd

Observer
I opted to not use the cabin switch for a few reasons, the main one being I just didn't want to run the wiring and find a place to put the switch. I have only needed to pop the hood once to manually connect the batteries when I killed the starting battery by leaving my lights on all day. Other than that the loud, obvious sound of the solenoid engaging or disengaging has been enough for me to be confident it is working. I don't power a lot of fancy electronics, pretty much the only major constant draw is the fridge and that's not installed in the truck 24/7.
 

DaveInDenver

Middle Income Semi-Redneck
yeah i know that? but any list of "appliances" that may be effected?


blahhhhhh
Two-way radios sometimes don't like glitchy power. The under voltage trip on my Yaesu FT-857 is 11.2V with a minimum specified operating of 11.7V. Most ham radios are actually designed to work at 13.8V so they are really only happy with the engine running. FWIW, I usually turn my radios off during cranking if I remember.

On the flip side during cranking the voltage spikes can be severe and that's generally bad to put on anything electronic, which is why cars disconnect non-essential electronics during cranking. If you're not using ignition hot to control solenoids for aux and leave them always hot then isolating the aux battery during starting isn't a bad idea. When I hear of a fridge failure I wonder if it's the inverter or controller being hammered with starter-generated EMI.
 

Forum statistics

Threads
185,538
Messages
2,875,658
Members
224,922
Latest member
Randy Towles
Top