Hello everyone. I relay on this website a lot so im want to give back a bit.
To get started This is what I have and a Modification that i has made everything work way better.
The modification is that when the car is OFF, the batteries are ALWAYS disconnected, so you always have one battery safe from the other.
dual battery set up (OPTIMA YELLOW TOPS)
Blue Sea ML-ACR 500 AMP with remote Automatic Charging Relay
Amazon.com : Blue Sea Systems ML-ACR 12V DC 500A Automatic Charging Relay with Manual Control : Boating Battery Switches : Sports & Outdoors
So basically, here is the wiring diagram from Blue Sea
as you can see its pretty basic, you only have to connect 3 wires from the unit.
The RED wire, goes to the remote 2 spot.
The YELLOW wire goes to the remote 7 spot
The Brown goes to the IGNITION of the car.
why all the extra wires? (the Brown, Green and Orange all do the same, so if you have a machine or boat with 2 engines you can isolate when any engine turns on)
Now, from the car you need a Positive and a Negative.
POSITIVE goes to 8 and 3 on remote
NEGATIVE goes to 1 on the remote.
Up to this point is basic
TIPS.
Take the positive ONLY from 1 of the batteries, most likely the STARTING or MAIN battery. The battery you will most likely always have on in the car, so you always have a positive line active.
Put fuese on all positive line cables, this includes the BROWN wire that goes to the ignition switch.
Where is the ignition? if you have never taken an IG line then just go to the main fuse box inside of the car, look for the IG logo, and take it from the cable that is connected AFTER the fuse
If you have accessories already connected, you can take the IG (Ignition) line from any cable that is already IG, but put a fuse (2-3.5 amp) smaller the better.
It does not matter which battery goes to A or B port of the unit, its just a cut out switch, so it does not care if A is start or main, or aux or whatever or if B is. It only senses voltage from both ports and lets current thru in both directions.
.................................
Ok, now to understand how the system works and why It need a Modification in my opinion.
The Blue Sea ML-ACR works by combining the batteries if several things happen. (when remote turn to auto)
1. If there is a voltage source that is over 13.5 volt going to either one of the batteries (A or B terminal of the unit) for more than 2 minutes
1.If both batteries are at least 12.1 volts (or 12.3 i cant remember). Basically, if both are ok healthy, so if one battery is at 7Volt, and you turn the car on, and it connected the batteries together you will ruin the good battery with the bad one. This is the reason why this is there.
Ok. Now for how the ML-ACR works when the batteries are ALREADY connected together, so, how does it know to disconnect them??
1. if there is a voltage ramp from one of the ISOLATION WIRES (Orange, Brown or Green) this is why when you are going to turn on the car and the remote is on AUTO, it will isolate the batteries and use only the STARTER battery to start the car, from there it goes into the wait 2 min, is the voltage High enough, etc.
Understand its a RAMP, so it does not need to stay ON for the batteries to disconnect, a simple 12Volt then 0 Volt will do to isolate the batteries. This ramp is a positive one, so going from 0 to 12 volt, not from 12 to 0.
2. If either of the batteries drops below 12.65 volts, the ML-ARC will disconnect the batteries. this is to make sure if you have the batteries AUTOMATICALLY connected together and you are running your fridge, or lights or stereo, when the voltage drops to 12.65 it will disconnect the batteries, and then your stuff will be only running from wherever you have it connected, most likely your AUX battery.
THIS is where the mod comes in. lets explain why.
If you have normal acid flooded batteries, 12.65 is preatty good. If you have Red Tops 12.65 is good. IF YOU HAVE YELLOW TOPS OPTIMAS or any other DUAL PURPOSE SEALED AGM batteries then thats a bad number.
Yellow Tops are good on 13-13.2 volts, fully charged.
So if you have a very good new battery, that charges and holds 13.2 volts, and another crappy battery, that charges and holds only 12.8 volts. When you go for a drive, the batteries automatically connect together, fully charge and then you stop, park the car over night and go to sleep.
over the night the healthy battery wants to stay at 13.2 volts, but the s*** one will want to go to 12.8, so they start to steal charge from each other, the good battery gives voltage to the bad battery until they both are on 12.8.
this does not sound so bad but think of it this way, 12-13 volts is your only usable voltage range of a battery, so this 1 volt is 100%
if you drop from 13.2 to 12.8 you just lost 40% of you energy, usable energy, just because one battery stole it from the other.
And since both batteries are still over 12.65 volts, the Blue Sea ARC will not disconnect them, it will keep them together, until this keeps on happening the bad one eventually only holds 12.6 volts (which is a good holding voltage for a normal flooded battery) and then it will disconnect.
The bad news is since this is every night you just ruined your yellow top because now it also only holds 12.6 volts, because you are recharging it every day forever!!!!
another example.
You have a dual battery system but now you have a RED TOP and a YELLOW TOP.
they will get combined under normal driving, then you turn off the car go to sleep, since the holding voltage is different, same thing happens, the RED TOP will steal from the YELLOW TOP until they both are equally at the lower voltage. 12.7 if your red top is brand new, or 12.65 until isolation from the sistem
since there is no factory way to make sure your batteries are disconnected AUTOMATICALLY when you turn your car off, you have to manually switch it to OFF, and make sure you put it in AUTO or ON next time you start the car.
so looking at the wiring diagram and doing some testing I noticed that the unit Isolates the battery when the REMOTE cable feels a ground or is Grounded permanently.
on this line of thought what i did was put a relay that is Normally Closed connected to ground and the REMOTE wire. and activate the relay with the IGNITNION voltage so that when ever you turn the key to IG the relay will be open and the unit will function normally.
here is the modified wire diagram
To explain.
the relay is in the natural state of NORMALLY CLOSED, so if you dont do anything to it wires 30 and 87a (black and blue) will be connected.
if the relay gets activated by a 12 volt source on pin 85 (pink wire) then it will OPEN THE RELAY and you will nave no continuity between pins 30 and 87a or Black and Blue.
since the IGNITION wire or PINK wire is at 0 volt when the car is off or the key is not in the IG position, there will be a GROUND on the REMOTE wire, thus Isolating your batteries.
But!!! if you turn the car on! or put the key on the IG position, the relay will activate and disable the force Isolation, thus putting the Blue Sea back to original function and waiting for the necessary events to connect the battery.
This mod has worked wonders on my car. Now every morning both of my batteries are on 13 volts (12.96 and 13.1 to be exact) before, every morning both were on 12.65volt since they were battling each other all night.
Now every time i park at for overnight camping my start battery is totally isolated and i dont have to worry that if a do a stupid short of something catastrophic happens, its all disconnected.
Also, if i ever need to put a normal flooded battery in the car because one battery brakes or waterer i dont have to worry about only having limited voltage.
in any case, this is my long story and hope to help someone.
on a note, and help needed on this. if you for some stupid reason move the remote to the ON position while the car is OFF and the key is not in the IG position, you just sent voltage from the battery (pin 8 on the remote) to ground (thru pin 87a and 30) so you just short the ignition fuse. to fix this i was thinking of puting a small light on this wire from 87a to REMOTE, basically put a light in the middle of the blue wire. So if you ever do this a light will turn on and thats it, then you know you have to put the key in the IG position, what do you guys think?
thanks again for reading.
To get started This is what I have and a Modification that i has made everything work way better.
The modification is that when the car is OFF, the batteries are ALWAYS disconnected, so you always have one battery safe from the other.
dual battery set up (OPTIMA YELLOW TOPS)
Blue Sea ML-ACR 500 AMP with remote Automatic Charging Relay
Amazon.com : Blue Sea Systems ML-ACR 12V DC 500A Automatic Charging Relay with Manual Control : Boating Battery Switches : Sports & Outdoors
So basically, here is the wiring diagram from Blue Sea
as you can see its pretty basic, you only have to connect 3 wires from the unit.
The RED wire, goes to the remote 2 spot.
The YELLOW wire goes to the remote 7 spot
The Brown goes to the IGNITION of the car.
why all the extra wires? (the Brown, Green and Orange all do the same, so if you have a machine or boat with 2 engines you can isolate when any engine turns on)
Now, from the car you need a Positive and a Negative.
POSITIVE goes to 8 and 3 on remote
NEGATIVE goes to 1 on the remote.
Up to this point is basic
TIPS.
Take the positive ONLY from 1 of the batteries, most likely the STARTING or MAIN battery. The battery you will most likely always have on in the car, so you always have a positive line active.
Put fuese on all positive line cables, this includes the BROWN wire that goes to the ignition switch.
Where is the ignition? if you have never taken an IG line then just go to the main fuse box inside of the car, look for the IG logo, and take it from the cable that is connected AFTER the fuse
If you have accessories already connected, you can take the IG (Ignition) line from any cable that is already IG, but put a fuse (2-3.5 amp) smaller the better.
It does not matter which battery goes to A or B port of the unit, its just a cut out switch, so it does not care if A is start or main, or aux or whatever or if B is. It only senses voltage from both ports and lets current thru in both directions.
.................................
Ok, now to understand how the system works and why It need a Modification in my opinion.
The Blue Sea ML-ACR works by combining the batteries if several things happen. (when remote turn to auto)
1. If there is a voltage source that is over 13.5 volt going to either one of the batteries (A or B terminal of the unit) for more than 2 minutes
1.If both batteries are at least 12.1 volts (or 12.3 i cant remember). Basically, if both are ok healthy, so if one battery is at 7Volt, and you turn the car on, and it connected the batteries together you will ruin the good battery with the bad one. This is the reason why this is there.
Ok. Now for how the ML-ACR works when the batteries are ALREADY connected together, so, how does it know to disconnect them??
1. if there is a voltage ramp from one of the ISOLATION WIRES (Orange, Brown or Green) this is why when you are going to turn on the car and the remote is on AUTO, it will isolate the batteries and use only the STARTER battery to start the car, from there it goes into the wait 2 min, is the voltage High enough, etc.
Understand its a RAMP, so it does not need to stay ON for the batteries to disconnect, a simple 12Volt then 0 Volt will do to isolate the batteries. This ramp is a positive one, so going from 0 to 12 volt, not from 12 to 0.
2. If either of the batteries drops below 12.65 volts, the ML-ARC will disconnect the batteries. this is to make sure if you have the batteries AUTOMATICALLY connected together and you are running your fridge, or lights or stereo, when the voltage drops to 12.65 it will disconnect the batteries, and then your stuff will be only running from wherever you have it connected, most likely your AUX battery.
THIS is where the mod comes in. lets explain why.
If you have normal acid flooded batteries, 12.65 is preatty good. If you have Red Tops 12.65 is good. IF YOU HAVE YELLOW TOPS OPTIMAS or any other DUAL PURPOSE SEALED AGM batteries then thats a bad number.
Yellow Tops are good on 13-13.2 volts, fully charged.
So if you have a very good new battery, that charges and holds 13.2 volts, and another crappy battery, that charges and holds only 12.8 volts. When you go for a drive, the batteries automatically connect together, fully charge and then you stop, park the car over night and go to sleep.
over the night the healthy battery wants to stay at 13.2 volts, but the s*** one will want to go to 12.8, so they start to steal charge from each other, the good battery gives voltage to the bad battery until they both are on 12.8.
this does not sound so bad but think of it this way, 12-13 volts is your only usable voltage range of a battery, so this 1 volt is 100%
if you drop from 13.2 to 12.8 you just lost 40% of you energy, usable energy, just because one battery stole it from the other.
And since both batteries are still over 12.65 volts, the Blue Sea ARC will not disconnect them, it will keep them together, until this keeps on happening the bad one eventually only holds 12.6 volts (which is a good holding voltage for a normal flooded battery) and then it will disconnect.
The bad news is since this is every night you just ruined your yellow top because now it also only holds 12.6 volts, because you are recharging it every day forever!!!!
another example.
You have a dual battery system but now you have a RED TOP and a YELLOW TOP.
they will get combined under normal driving, then you turn off the car go to sleep, since the holding voltage is different, same thing happens, the RED TOP will steal from the YELLOW TOP until they both are equally at the lower voltage. 12.7 if your red top is brand new, or 12.65 until isolation from the sistem
since there is no factory way to make sure your batteries are disconnected AUTOMATICALLY when you turn your car off, you have to manually switch it to OFF, and make sure you put it in AUTO or ON next time you start the car.
so looking at the wiring diagram and doing some testing I noticed that the unit Isolates the battery when the REMOTE cable feels a ground or is Grounded permanently.
on this line of thought what i did was put a relay that is Normally Closed connected to ground and the REMOTE wire. and activate the relay with the IGNITNION voltage so that when ever you turn the key to IG the relay will be open and the unit will function normally.
here is the modified wire diagram
To explain.
the relay is in the natural state of NORMALLY CLOSED, so if you dont do anything to it wires 30 and 87a (black and blue) will be connected.
if the relay gets activated by a 12 volt source on pin 85 (pink wire) then it will OPEN THE RELAY and you will nave no continuity between pins 30 and 87a or Black and Blue.
since the IGNITION wire or PINK wire is at 0 volt when the car is off or the key is not in the IG position, there will be a GROUND on the REMOTE wire, thus Isolating your batteries.
But!!! if you turn the car on! or put the key on the IG position, the relay will activate and disable the force Isolation, thus putting the Blue Sea back to original function and waiting for the necessary events to connect the battery.
This mod has worked wonders on my car. Now every morning both of my batteries are on 13 volts (12.96 and 13.1 to be exact) before, every morning both were on 12.65volt since they were battling each other all night.
Now every time i park at for overnight camping my start battery is totally isolated and i dont have to worry that if a do a stupid short of something catastrophic happens, its all disconnected.
Also, if i ever need to put a normal flooded battery in the car because one battery brakes or waterer i dont have to worry about only having limited voltage.
in any case, this is my long story and hope to help someone.
on a note, and help needed on this. if you for some stupid reason move the remote to the ON position while the car is OFF and the key is not in the IG position, you just sent voltage from the battery (pin 8 on the remote) to ground (thru pin 87a and 30) so you just short the ignition fuse. to fix this i was thinking of puting a small light on this wire from 87a to REMOTE, basically put a light in the middle of the blue wire. So if you ever do this a light will turn on and thats it, then you know you have to put the key in the IG position, what do you guys think?
thanks again for reading.
