Battery Isolator Issue

[kdgreene]

I am having a perplexing issue with the battery isolator installed in my camper. The old one appeared to have a bad solenoid so I replaced it with one made by Blue Sea. The issue is that the house batteries are not being charged.

When the engine is on, my multimeter shows that there is voltage of 14.6 coming into the isolator, as well as 14.6 going out the battery connection side of the isolator. However, as soon as I connect the battery charging wire from the house battery to the isolator, the voltage on BOTH sides of the isolator drop to that of the house batteries, which at this point is 12.8. So presently the house batteries are not being charged by the alternator. Does anyone have any suggestions as to what may be causing this? Thanks.

 

[DiploStrat]

You lost me - where are you measuring? There is only one large terminal for each battery.

Engine running you should see something like:

Alternator - 14v+

Starter battery - about the same, perhaps a bit lower.

Camper battery - Who knows?

The Blue Sea ACR should close, that is combine, when it detects greater than about 13v for at least two minutes at either battery. Are you giving it enough time?

See: Automatic Charging Relay (ACR) Explained - Blue Sea Systems

 

[kdgreene]

I am measuring the voltage on the terminals of the ACR itself. There is the "A" terminal from the truck battery and the "B" terminal for the house batteries.

 

[DaveInDenver]

I am measuring the voltage on the terminals of the ACR itself. There is the "A" terminal from the truck battery and the "B" terminal for the house batteries.

Are you forcing the ACR (a model number may be helpful to verify operation) to combine or waiting for it to do so automatically? You are absolutely sure the solenoid has pulled in and latched?

If it's an ML-ACR (7622) it will latch and unlatch as follows:

Combine at 30 sec with 13.5V or higher
Combine at 90 sec with 13.0V
Open at 10 sec with 12.35V or lower
Open at 30 sec with 12.75V
Open immediately at 16.2V (over voltage condition)

Going from 14.6V down isn't unusual if your house battery is deeply discharged. As long as it doesn't trigger the 10 or 30 second disconnect and start cycling on and off you might just leave it and see if the voltage slowly rises.

I'd also make sure it's actually 12.8V before the combine and you see the 14.6V drop to 12.8V coincident with the solenoid closing. Then measure at several points in the circuit. If it's 12.8V at the ACR I bet it's 12.6V (or something lower anyway) at the house battery and probably higher at the alternator. That would indicate the house battery wants current enough to see the voltage drops in all your wiring.

 

[DiploStrat]

For some reason, this did not post. Dave's comment above is even more complete.
====================================================================
Assuming this wiring: ML-ACRs.jpg (1479×1267) (bluesea.com)

When the relay is closed, the voltage will be the same on both sides. If your camper battery is really down, it may take a few minutes for the alternator to get the voltage at the starter battery high enough to combine. I would leave the engine running for five minutes or more.

Beyond that, beats me - call Blue Sea.

 

[kdgreene]

Thanks. I'm using the 7610 ACR and I've conducted test as per the ACR troubleshooting worksheet provided by Blue Sea.

I am using solar primarily to charge my house batteries. What happened here is this: while on a trip earlier this fall, we experienced several days of bad weather which caused our solar charge to drop, which led us to realize that our existing Isolator was not working properly. When we returned home, I upgraded our isolator to the Blue Sea as our old isolator had been running very hot before it stopped working.

After installing the 7610 and turning off the solar, I was able to check the charging current from the alternator with the charge of the house batteries. The house batteries are only 2 years old and are still working very well.

The 7610 takes approx 2 minutes from the time the alternator begins to send current before it combines to the house battery. So will waiting for the combining to take effect, I kept my voltmeter probes on the unit watching the voltage. The incoming voltage was properly showing 14.6 from the alternator and 12.8 from the house batteries. As soon as the 7610 showed that it was combining the batteries, the voltage on the incoming side of the unit dropped to the same voltage as the house batteries. Moving the voltmeter to the starting battery showed that the alternator was continuing to work properly.

I'm guessing at possible problems now, could it be the wiring harness on my Lance camper? I just don't know. Thanks.

 

[WOODY2]

Perhaps baseline both batteries by fully charging independent of each other and the isolator then reintroduce the isolator to see if system will work as designed?

 

[DiploStrat]

Thanks. I'm using the 7610 ACR and I've conducted test as per the ACR troubleshooting worksheet provided by Blue Sea.

...

The 7610 takes approx 2 minutes from the time the alternator begins to send current before it combines to the house battery. So will waiting for the combining to take effect, I kept my voltmeter probes on the unit watching the voltage. The incoming voltage was properly showing 14.6 from the alternator and 12.8 from the house batteries. As soon as the 7610 showed that it was combining the batteries, the voltage on the incoming side of the unit dropped to the same voltage as the house batteries. Moving the voltmeter to the starting battery showed that the alternator was continuing to work properly.

...

It is working perfectly. The camper batteries draw down the voltage of the circuit and will continue to do so until they are charged.

 

[DaveInDenver]

I upgraded our isolator to the Blue Sea as our old isolator had been running very hot before it stopped working.
-snip-
I'm guessing at possible problems now, could it be the wiring harness on my Lance camper? I just don't know. Thanks.

It does sound like it's working as expected. With the 7610 the only thing you can really watch is that you have a solid connection to your ground bus and that it's a good bus across both sides.

The thing that concerns me is when you say the old one was running hot. If you start to develop a voltage to ground or between truck and house ground you might get erratic behavior or damage. The control circuit is supposed to draw about 175 mA so there shouldn't be any noticeable heat dissipated from that.

It's unlikely (but not impossible, do you know what it's rated?) your alternator will source enough current to overheat the solenoid itself. The device is rated to 120 amps continuous and 210 amps for up to 5 minutes. It might get a little warm if you ask it to carry 120 amps for a long time (several tens of minutes) but subjectively it shouldn't be "hot". More like an incandescent appliance or Christmas light warm, a few watts.

SI-ACR Automatic Charging Relay - 12/24V DC 120A - Blue Sea Systems

Automatically combines batteries during charging, isolates batteries when discharging and when starting engines.

www.bluesea.com

 

[DiploStrat]

... However, as soon as I connect the battery charging wire from the house battery to the isolator, the voltage on BOTH sides of the isolator drop to that of the house batteries, which at this point is 12.8. So presently the house batteries are not being charged by the alternator.
...

Actually, they are. The Blue Sea ACR is merely a voltage sensing relay, or solenoid. When it is closed, it acts like a wire connecting the two batteries.

Now, take two batteries, one charged, one discharged and connect them in parallel. The voltage across the circuit will be somewhere between the voltage of the higher and the lower battery. The speed with which they both reach the same voltage will depend on, among other things, the size of the wire connecting the two batteries - big wire = fast change.

The great advantage of a voltage sensing (or "intelligent") relay is that a charge at EITHER battery, starter or camper, is shared with the other. So, typically, when driving, the charge source is the alternator. When parked, solar or shore power. Set things up properly and you will never have to worry about a dead starter battery.

See "Doubling Up!" on this page: Documents | DiploStrat

 

[kdgreene]

Thanks for all the suggestions. It does appear to be wired correctly, so maybe I'm just impatient to see a positive charge on the house batteries. I'll have to do some more testing to confirm that the batteries are charging.

 

[DiploStrat]

Depending on your alternator, count about one to two hours per 100Ah of camper battery, and then 30 minutes to one hour of absorb charge per 100Ah of battery.

You should, however, see the voltage begin to rise in one to two hours.

 

[john61ct]

Did not read the thread

The ACR is just a switch, best you hope is minimal V drop across it when closed.

The CIRCUIT voltage from target batteries back to the actual source

should also have minimal V drop - fat wires help, beyond what safety dictates. Or get a DCDC for long distances.

That circuit voltage will vary as the battery goes from low SoC to the CV setpoint, and then sits there ideally for many hours before the regulator drops V to Float.

Unfortunately very few charge sources do hold CV / Absorb stage anywhere near long enough

and the resulting PSOC abuse is the #1 cause of House banks getting murdered early.

as soon as I connect the battery charging wire from the house battery to the isolator, the voltage on BOTH sides of the isolator drop to that of the house batteries, which at this point is 12.8. So presently the house batteries are not being charged by the alternator.

So this is normal, and the bank SoC, and circuit voltage should be rising over the next 6-8 hours.

But many modern alternators are crap at charging House bank without a DC-DC charger like Sterling's BB series.

Especially if the regulation is done by the ECU for fuel mileage reasons, modern Euro style vehicles being particularly hopeless

 

[john61ct]

For old-school trucks you can convert the alt to an external regulator like Balmar MC-614 or the new Wakespeed type.

And also maybe upgrade to a bigger amps large-frame alt, but usually not worth the expense without also upgrading to a LFP House bank.

 

[burleyman]

I've seen nothing about measuring amperage. Volts and Watts get all the attention. Current flow/amps tell the truth. Volts should get a glance. Amps should be stared at. Nothing is really known about charging without an amp reading.