Dual battery solenoid options

[Cruisertrash]

What is a measure and defining of topped off?

100%. I put MRBF Terminal Fuses (Blue Sea or Bussman brand) on the battery at each end of the long run from engine bay to under Longcruiser rear seats. My short runs between batteries under the long cruiser rear seats are in PET Expandable Braided Sleeving inside flexible wire loom. I have a MRBF Terminal Fuse at the battery end of the long run from my other 80's cable (2 or 4 ga I think) from engine bay to ARB twin compressor in the cargo area. This is not because I anticipate heavy loads. This is to protect the wires from ground shorts.

12.6VDC

 

[MDH33]

Thanks for all the replies and info, great stuff!

Following up, I had a road trip planned last week and needed it working to power my fridge and radios. I pulled the solenoid and connected everything direct and when I put a volt meter on the aux battery I was getting a weird intermittent, fluctuating charge. I started going through the wires and terminals and found that one of the big 100A midi fuses was bad. Looked OK and wasn't evident it was blown, but once I removed it, it literally fell apart. I picked up some better blue sea fuse holders and new fuses, replaced the wire end connectors and reinstalled the solenoid and it worked flawlessly on my 1000 mile road trip up to the North Shore. I should've started with the easy stuff rather than assuming the solenoid was bad, but the symptoms were odd. Anyway all set and now I have good references for future upgrades.

 

[Inukshuk]

Cool!
Yes, bad fuses do wired things!

 

[nakman]

Alright I'm about to do this again... and leaning again towards the same Blue Sea setup. @Inukshuk Daniel you said on the last page that the Blue Sea system combines based on time, not voltage? I guess that didn't sink in until now...

Sure, isolators have some nifty battery health features, but they are by no means necessary to reap benefits of having multiple parallel battery.


That "switch" combines in 10 or 90 seconds and opens in 10 or 30 seconds.
It is time and voltage based. It simply makes sense to not combine when the start battery is powering the starter and then put some juice into the just-used starter battery first. Nothing to do with state of charge.
Blue Sea MIL ACR Relay Instructions: https://d2pyqm2yd3fw2i.cloudfront.net/files/resources/instructions/980035700-001-ML-ACRs.pdf

Blue Sea MIL ACR Relay Instructions: https://d2pyqm2yd3fw2i.cloudfront.net/files/resources/instructions/980035700-001-ML-ACRs.pdf and https://www.bluesea.com/support/articles/1366/Automatic_Charging_Relay_[ACR]_Explained

An alternator can only do its maximum. If you have one dead car battery on a 100 amp alternator, that alternator will output whatever the battery will accept up to 100 amps. If you have two or 10 dead car battery on a 100 amp alternator, that alternator will output whatever the batteries will accept up to 100 amps.

Just the same above time and voltage based method.

Same as above: An alternator can only do its maximum. If you have one dead car battery on a 100 amp alternator, that alternator will output whatever the battery will accept up to 100 amps. If you have two or 10 dead car battery on a 100 amp alternator, that alternator will output whatever the batteries will accept up to 100 amps.

Undervoltage lockout is 9.6 for Blue Sea ACRs. The point being if a battery only reads 9.5 it is likely damaged and should be treated differently than ordinary charging. https://www.bluesea.com/support/articles/1366/Automatic_Charging_Relay_[ACR]_Explained

"What does “Undervoltage Lockout” mean? As a safety feature, some ACRs prevent combining into a severely discharged battery. A dual-sensing ACR will monitor the voltage on both batteries and will not connect if either battery is below the undervoltage lockout level. Use caution when combining into a battery with extremely low voltage, because this might represent a faulty battery or a problem elsewhere in the system."​

Just want to make sure I understand this, as I'm about to do it again... So the Blue Sea MIL ACR combines based on voltage+time. If volts>13.5 then 30 seconds, volts >13.0 then 90 seconds, and voltage < 13.0 then no combine. I still feel like this is pretty ideal for my real world conditions.


Just looking for a reason to not go with Blue Sea again.. my other argument in the "for" column would be 3 trucks all with Blue Sea setups.

 

[DaveInDenver]

The values are fine with the only exception being under difficult conditions you might want to manually latch it. That might be forced into connected or forced into disconnect, that's your choice. But the 12.35V open and 13.0V reconnect can occasionally lead to the relay flopping between states when you're winching or jump starting someone. I've since moved to a DC-DC solution, but when I had an ML-ACR I would override it to stay open during winching so that it would never try to pull energy from the house/backup battery. In my case the second battery only had the fridge on it, so right off charging it would still have enough surface charge to confuse the logic.

 

[nakman]

The values are fine with the only exception being under difficult conditions you might want to manually latch it. That might be forced into connected or forced into disconnect, that's your choice. But the 12.35V open and 13.0V reconnect can occasionally lead to the relay flopping between states when you're winching or jump starting someone. I've since moved to a DC-DC solution, but when I had an ML-ACR I would override it to stay open during winching so that it would never try to pull energy from the house/backup battery. In my case the second battery only had the fridge on it, so right off charging it would still have enough surface charge to confuse the logic.

that's why I like the switch for the Blue Sea. for example when I air up, I pop the switch to combine both batteries- it's almost as good as leaving the truck idling, but it's quieter. plus I'm saving the planet. And sometimes I'll manually disconnect them just to expand upon one of my many mental solar panel experiments. I also like leaving the switch in "auto" all the time, so I can see the status of the ACR. I hadn't thought about disconnecting during winching, yes the winch is connected to the main battery but gosh, I bet it's been 10 years since I've actually done a mired down winch pull, all we seem to do lately is winch demos and flip over fences at Waldorf.

I have the switch in the GX, I don't have the switch in the Tundra (no clean place to install one). but I gotta have the switch...

 

[DaveInDenver]

You don't need the remote switch strictly speaking. There's a rotating selector with a button in the middle on the ML-ACR. If you rotate the knob you select either remote/auto (e.g. the time-voltage criteria) or force them to disconnect (they will never connect).

With the knob rotated to auto it'll follow the remote switch or if you push the button in the middle it'll force combine them for 10 minutes after which the logic will decide if it stays combined or open based on voltage.

The only wire that must be used is the small black, which is ground in the control harness for the logic. You can leave all the other wires floating.

 

[nakman]

It's really tough to reach that knob though while driving. I don't open the hood as often as I want to manipulate/monitor battery monitoring.

 

[DaveInDenver]

Gotcha. I usually just let the thing do it's thing except while winching, when I'd have to open the hood for its battery disconnect anyway.

 

[MDH33]

It's really tough to reach that knob though while driving. I don't open the hood as often as I want to manipulate/monitor battery monitoring.

One of the things I like about my National Luna solenoid is the in cab voltage meter. It has a button that let's you manually connect the batteries for witching, airing up or to bypass the low voltage disconnect and charge both batteries. What I don't like is that the low voltage disconnect is kind of high in my opinion, like 12.4 or something, so if I'm idling or in traffic and have all the lights, heater fan on, it will auto disconnect.

 

[Inukshuk]

Time and voltage.
I like it for its simplicity.