Battery isolator no longer isolating?

S

seascape

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Hi all, hope everyone is safe and healthy!

Our Cdory has a battery isolator on board feeding both battery banks and I think it has shorted. When I switch between bank 1 (starting) and 2 (house) using the battery selector the voltage up in the console on the battery gauge reads the same each time. I only noticed this recently when I knew for sure my house batteries were totally dead (I think the isolator didn't isolate actually). I used a voltmeter on the house bank (it's actually two in parallel) it read below 10 V, the starting battery was fully charged.

I decided to troubleshoot and I disconnected the starting battery from the isolator and also disconnected what I believe is thin wiring from the outboard motor into the isolator. Then I checked the voltage up front at the battery gauge on the console and it actually read the voltages more accurately (I think there is some voltage loss from the wiring run but it's not very significant). The battery gauge now showed the two different voltages which more closely matched what the voltmeter read when I directly tested the batteries.

So I tried to figure out why the outboard, a Honda BF135, might have a separate thin gauge wiring and from what I read it might be because the ECU or ECM is sensitive to voltage drop/sag and so is wired separately. Has anyone heard of that before? I'm thinking of getting a new isolator or more likely a VSR and am wondering how I should wire it up. I want to keep the shore power as an option for charging the battery banks if possible, but more importantly I want to charge either bank when under way. I read you can pair two VSR's to achieve all of this but also found a company selling a dual sense VSR which sounded interesting.

Anyways, any advice is appreciated! I'm not sure what happened to the isolator. From the previous owner the cockpit was flooded at some point while it was on a lift and charging from shore, so I imagine the isolator probably shorted at that point.
 
Give us some more information on the "isolator". Is this a single or several diodes with a heat sink? Or is it a really, or a Voltage Sensitive Relay?

Is all of the wiring in perfect condition (no corrosion, all of the crimped joints good and all of the nuts and connectors tight)?

10 volts does not sound good, and the batteries may be shot. How old are the batteries.

VSR can run down batteries, if the are not turned off when the boat is idle and. no charging.
 
Hi thanks for the response!

It's a multi battery isolator from "Professional Mariner" model 2-70-3, it has two inputs (listed as A1 and A2) and 3 outputs. The unit has max 70 amps and 6-50v inputs. Yes it looks like a large heatsink. I can send a picture if you think that's helpful.

I replaced much of the wiring between battery selector and batteries themselves. I did not change out these thin gauge wires, but I cleaned everything off with a dremel and brass brush bit. It's been pretty good for the two seasons I used it after this work I did.

There was a lot of corrosion originally (from over charging I believe), the batteries were the original 2004 batteries (4 dual purpose batteries in two banks) and were well over 10 years old at the time! Not entirely sure how that's feasible but they actually worked for the first season for us. I replaced the batteries with a new configuration-- two deep and one starting.

The new batteries are probably 3 years old now, I think the deep cycles basically trickle charged the starting battery while sitting dry so their voltage was very low. I charged them back up and seemed to hold their voltage. I was pretty bummed when I first realized they were so depleted, I'm crossing my fingers they will be ok.

I heard about VSR's causing dead batteries so I am a bit hesitant, but from what I read the newer models have very low parasitic draw.

Any idea what the thin-gauge wiring from the Honda is? I only found one post on the internet about it. I have to get a look at a real mechanics manual.
 
I am familiar with that isolator. It is for 2 alternators and 3 batteries. Not sure why it was used on the C Dory with a single engine, except it may be what was available. There is going to always be at least 1/2 volt drop over the diodes of that isolator. I have not used that type of isolator for over 20 years.

Another thought--I wonder if he had a single output battery charger to the other "alternator" input?

The VSR is a far better choice. You can just cut them off and no parasitic draw. I have been using VSR for many years, and never had a problem. There is no voltage drop. With your configuration a VSR should work very well.

Here is the quote from the manual for the isolator:

]How do I wire up the isolator?

ANSWER: The isolator is wired between the alternator and the batteries. One or two alternator input terminals
connect from the alternators to either two or three output terminals connected to batteries.

4) QUESTION: There is no output voltage on my isolator?

ANSWER: Check to see if the isolator is working with a digital multi-meter set on “DIODE CHECK” mode. Put the red lead on the alternator input terminal and the black lead on one of the battery output terminals.....you should get a reading around .4 on most meters. Then reverse the leads and you should get a reading of infinity. Perform this procedure from all of your alternator input terminals to all of your battery output terminals. If you get a different reading with the red lead on a battery terminal then the isolator is defective.
Click to expand...

The manual calls for a #6 for 20 feet or # 8 for 10 feet round trip from alternator to battery. So if they have put a wire directly from the alternator, it should not be a small wire. It would also be little unusual on an outboard to go from the alternator to an isolator which is also attached to the start battery.

I would guess that the batteries being dry, would be overcharged by a shore power battery charger or did not have the fluid check on a regular basis.


My best guess is that the isolator has a defective diode. I would not use it any further. You can also put a battery into the input, and just read the output on each of the terminals with you digital volt meter to further check the diodes and voltage drop.

As to the "thin wiring from the outboard motor into the isolator." I would guess that this was supposed to be from the alternator? I would trace that wire back. I have the full shop manual for the 2004 to 2010 Honda 150 HP outboard. (about 1 1/2" thick. The alternator is connected thru a 90 amp fuse to the starter relay and then to the start battery. There is another leg of this from the battery back to the main electrical fuse panel inside of the engine cover.

What color is the wire, and where does it go once inside the cowl?

What 110 volt battery charger do you have?
 
I'll try those diode check troubleshooting steps next chance I get, thanks.

You're right one of the inputs to the isolator is from the shore power charging system which I did test. The other input runs back towards the outboard into the bundle that feeds from it. I didn't look under the cowl to see where it went, I figured I could look in a manual but what I found online is not similar to what I think is wired-- I won't be able to get back to the boat soon. All of those inputs to and from the isolator are more like # 12, so low amperage I'm assuming.

I'm on board for the VSR except I was hoping to keep both alternator charging and shore charging systems for both banks, if possible. So I'm not entirely sure how that would work. I also have a battery selector to both banks, it's a 1-both-2-off switch.
Thanks for your help!
 
The battery charger could be shot--what model do you have. The factory Guest chargers don't last all that long.

The VSR will do all that you want-keeping the 40 amp output of the alternator and whatever you want with a battery charger.

Keep the 1/2/all/off switch.

Someone has fooled with the wiring already. #12 is small for the 40 amp alternator. It would be OK for 5 or 10 amps, if fairly short. For my 30 amp charging off the 44 amp alternator of the 150, (scaled down to 30 amps for battery to battery for Li batteries, I use #8 wire. With 30 amp circuit breakers on both ends.
 
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