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Old 01-08-2016, 10:33 PM   #1
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Battery Isolator??

What does this thing do?? Newbie owner here just bought an Overland Lorado and trying to figure out what everything does. Not a whole lot of info on these coaches, though I suspect this is a common appliance on an RV.

I have 4 6V house batts (series/parallel), and 2 chassis batts that measure 12.18 volts on the voltmeter, but the gauge on the instrument cluster shows close to 8V when I turn the key on the accessory prior to starting. The gauge will climb when I push the emergency start switch...I'm assuming the solenoid is closing when I do this, thus connecting the house batts to the chassis??

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Old 01-08-2016, 11:24 PM   #2
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Quote:
Originally Posted by OvrLand Flyr View Post
What does this thing do?? Newbie owner here just bought an Overland Lorado and trying to figure out what everything does. Not a whole lot of info on these coaches, though I suspect this is a common appliance on an RV.

I have 4 6V house batts (series/parallel), and 2 chassis batts that measure 12.18 volts on the voltmeter, but the gauge on the instrument cluster shows close to 8V when I turn the key on the accessory prior to starting. The gauge will climb when I push the emergency start switch...I'm assuming the solenoid is closing when I do this, thus connecting the house batts to the chassis??

That is an electronic battery isolator. In many coaches, it's mechanical, like ours. Mechanical is a solenoid that closes to connect both the house batteries and chassis batteries to be charged, while driving down the road.

But what you appear to have is, an electronic version. That unit connects both the house batts and chassis batts for charging by your engines alternator.

But, when you shut the engine down, that unit simply "isolates" the chassis batteries from the coach batteries so that, power to run the coach appliances is only derived from the coach batteries.
Scott
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Old 01-09-2016, 05:52 AM   #3
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What that isolator does is take your altenator output ( center wire ) and direct the current to both battery banks thru one way diodes. Because of the diodes, the current can't come back and drain to the other batteries.

Be Carefull if you need to replace your alternator. Newer style alternators will not have the correct wire connections to work properly.

When you hit the boost switch, you are connecting both battery banks with a solenoid, not the isolator.

Have someone hit the boost switch and listen for its "clunk"

If you need to hit the boost to start, you may have bad start batteries or a charging problem.
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Old 01-09-2016, 09:56 AM   #4
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What that isolator does is take your altenator output ( center wire ) and direct the current to both battery banks thru one way diodes. Because of the diodes, the current can't come back and drain to the other batteries....
OK, so I did a little googling and found out that while you are correct, maybe theres another, more efficient way to go about charging House/Chassis batteries from the Alternator, then using an Isolator such as this one.

Apparently, a "Combiner" would work better here because of the limitations of the design on the Isolator. Here is a quote from somebody on Amazon website in the comments section of a Noco Isolator such as mine...

Tell me what you think about the validity of this idea...seems legit.

Quote:
I was going to use this in my boat to connect the house and starting battery so they would charge together, and then keep the starting battery from discharging when the boat was off. Just as I was about to install, my boss came by (he's an electrical engineer by trade) and pointed out that I really wanted a combiner, and here's why:

With an isolator you will never see a full charge. The silicon used in the isolator will take about .6-.7 volts, so the most you will ever see is about 13.7 with the engine running (when 14.4 is being delivered). This is not satisfactory, as it will effectively reduce the run time on your house battery by about 20-25%.

Also, heat. It's going to generate a lot of heat. That's why it's encased in an enormous heatsink. I was going to mount this under a seat where there was little airflow and that wasn't going to work. A combiner generates NO heat at all, and the footprint is MUCH smaller.

Basically a combiner is just a switch. When the alternator is putting out juice, the batteries are connected. Simple. Both batteries receive a charge. When the alternator is not putting out juice and the combiner senses a draw on the second battery, it disconnects the two. Simple as that. It is a little more expensive but to me, very worth it (about $70 at cost, ~$90 retail). Blue Sea Systems sells one and they call it an Automatic Charging Relay. That's the one you want.

I'm sure this is a great product. Looked very well constructed, but it's not what you really want if you're looking to do what a lot of people here have done. Isolators were big in the 80s but technology has advanced.
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Old 01-09-2016, 10:05 AM   #5
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Yup look up " Yandina.com" they have a nice setup
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Old 01-09-2016, 10:05 AM   #6
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What ever "floats your boat" -- Dont see any issue with efficiency as most days, you are going down the road for hours--plenty of time to recover your bats. This isolator plays no role in charging while on genset or shore power, except to isolate the bats. If you ever need to replace the alternator, you will need to look for one with a Du Vac system that uses a separate wire to sense battery voltage.
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Old 01-09-2016, 10:36 AM   #7
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Something to test...

It seems the diode type has gone out of fashion with selenoids more popular.

This "looks" like a diode type but may not be.

Get a voltmeter and with engine off measure voltage at all posts.

Should have battery voltage at outside and nothing in the center.

Write these down.

Start engine and measure again.

Next place red lead on center and black lead one each outside post and measure the voltage between center and outside.

Write all of this down as way down the road yiu may need it...

If a diode isolator the voltage between center and outside should be 0.6 or so volts.

The outside voltage should be what the battery needs and center needs to be 0.6 volts higher.

If no difference it may be an electronic magic via MOFFET or other solid state devices.

Main thing here is document what you have when working properly.

If it is diode type the alternator voltage needs to be adjusted higher or special wiring to sense battery voltage.

Spare time project is to confirm exactly what you have so when the alternator takes a dump you can get correct one.

Tony ' s law states if you know it may be different and do not note it yiu will need to have done so but if you take the time now you will never need it...Unless you loose the notes...
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Old 01-09-2016, 10:47 AM   #8
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What does this thing do??

OvrLand Flyr
That's a 200A "solid state"/"diode based" battery isolator
See: Battery Isolator | Isolator for Multiple Batteries | Waytek Wire - Page 1 of 2
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Old 01-09-2016, 12:44 PM   #9
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Overland,
Welcome to IRV2. You should check your chassis batteries, electrolyte and charge. The battery voltage dropping like yours did when you turn the key is a sign of a dead battery.
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Old 01-09-2016, 01:24 PM   #10
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Overland,
Welcome to IRV2. You should check your chassis batteries, electrolyte and charge. The battery voltage dropping like yours did when you turn the key is a sign of a dead battery.
I checked the chassis batteries this morning after removing shore power that was on all night....disconnected all cables and got a reading of 12.18V on each chassis battery. Re-connected all cables and re-checked the same.

Before start with the key on and waiting for the start light to go out, the voltmeter read between 8-9 volts...



Once the start light went out, I cranked the engine (without using house batt assist) and the engine turned over real strong and started up just fine. After letting it idle for a minute or so, I cranked up the idle speed to about 1000RPM and went to the battery compartment to check voltages.
Chassis Batts - 13.3V
Alternator - 14.3V
Isolator output studs - 13.4V (see pic in first post)
Picture below shows the gauge reading after all this...I interpolate based on the numbers on the gauge that it reads about 12V...


Do I just have a bad gauge maybe??
Why such a voltage drop coming out of the isolator?
Is 13.4V enough to charge the batts properly??
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Old 01-09-2016, 01:39 PM   #11
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Well, that's the thing with isolators. They charge, but a bit slower then combiners. The alternator regulator may be adjustable and need to be turned up.

Check the voltage after a long run to see it it goes up. The batteries may be low.

The reason your voltage drops when first tuning the key is an electric pre-heat system that uses quite a bit of energy. They time out and shut down after a while.
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Old 01-10-2016, 06:42 AM   #12
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I checked the chassis batteries this morning after removing shore power that was on all night....disconnected all cables and got a reading of 12.18V on each chassis battery. Re-connected all cables and re-checked the same.

Before start with the key on and waiting for the start light to go out, the voltmeter read between 8-9 volts...

Once the start light went out, I cranked the engine (without using house batt assist) and the engine turned over real strong and started up just fine. After letting it idle for a minute or so, I cranked up the idle speed to about 1000RPM and went to the battery compartment to check voltages.
Chassis Batts - 13.3V
Alternator - 14.3V
Isolator output studs - 13.4V
Picture below shows the gauge reading after all this...I interpolate based on the numbers on the gauge that it reads about 12V...

Do I just have a bad gauge maybe??
Why such a voltage drop coming out of the isolator?
Is 13.4V enough to charge the batts properly??
OvrLand Flyr
I doubt that your dash gauge is bad... (few dash voltmeters are acurate meters... most simply give an you an "indication of the state of charge of the chassis battery").

Because all of your measured volt readings are within a 10th of a volt or 2 of what mine read under the conditions you describe methinks your charging system is working correctly.

Mel
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Old 01-10-2016, 08:59 AM   #13
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Sounds like your batteries are going bad. The first sign is the large voltage drop in the engine pre-heat and the second is that on a "full charge" you are only getting 12.18 volts. Batteries that are 12v are really 12.6 volts fully charged, 12v batteries have 6 cells and each cell should read 2.1 volts (same with 6v batteries but the only have 3 cells).

When testing your batteries they need to be unhooked and tested alone after the surface change has been removed, you can buy a capacitance tester for $50-70 on amazon or take them to auto zone/checkers and they will test them for free. Remember that if you have one battery that is bad it will drain the other, you should replace them in pairs. Good luck and let us know what you find.
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Old 01-10-2016, 11:45 AM   #14
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This could be right or wrong?

30 years ago it was explained to me that a battery isolator main use was to control the charging of two batteries or banks.

For EG.
If one battery bank was bigger than the other.

Or one of the batteries have a wiring gauge difference, or as well as a different or longer distance from the charge source.

The battery isolator would vary the charge rate between the two batteries, so that the closer battery would not over charge while trying to charge the further battery. Over time charging both batteries would come to a full charge.

When the batteries are hooked to the same charging source the further battery puts a load on the system calling for a higher charge rate from the regulator. This can over charge the closer battery and at the same time the further battery never receives a full charge.

I do not know for sure but all this could be done in a Battery Control Center that for e.g. is in my unit? and probably in most others now a days.
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