My battery isolator doesn't seem to work

[Zeusdafreak1]

I added a second battery 2 months ago. I used a battery isolator I purchased from Fleebay. The alternator charge wire goes to center post and each side post goes to each battery from the isolator. My ground from my auxilary battery is grounded to my original cranking battery because it was the easiest way for me to ground it. as far as I know this should cause I problem

The only thing I use my second battery for is the sound system. The original cranking battery is still hooked up with everything as from the factory. My problem occurred last weekend when I removed my deep cycle second battery to use in my fishing boat for trolling. I drained the battery and put it back drained. I discovered that the drained second deep cycle pulled my original cranking battery down. It shouldn't have because the battery isolator shouldn't allow them to see each other right? Did I do something wrong or is the battery isolator not working? what can I do to check this?

I wanted to do this right from the beginning AND keep it cheap and simple without buying the Blue Sea Add a battery which is really what I wanted but didn't want to pay that much.

 

[PondTunes]

Re: My battery isolator doesn't seem to work

What brand / model is it? It sounds like you've got it hooked up right. But it may be that it only isolates 1 direction. Ie it won't let the Deep Cycle be drained by the Cranking (which would probably be backwards) To fix it you might have to switch the way the batteries are connected to protect the cranking instead of protecting the deep cycle.

Blue Sea's add a battery system is top notch and worth the expense imo I've had great luck with them.

 

[Zeusdafreak1]

Re: My battery isolator doesn't seem to work

Here is the exact isolator I bought. Its a Cole-Hersee 70amp. I didn't see any arrows or any indicators telling me the direction of isolation but thats a possibility I didn't think of.

http://cgi.ebay.com/ebaymotors/70-a...018QQitemZ280151405336QQrdZ1QQsspagenameZWDVW

 

[PondTunes]

Re: My battery isolator doesn't seem to work

It shouldn't be an issue. Looking at the information at: http://www.colehersee.com/04resource/tec^Batt iso.htm

It says the unit contains 2 diodes and shouldn't allow one to drain the other. Are you sure there is no other link between the two systems?

 

[Zeusdafreak1]

Re: My battery isolator doesn't seem to work

The only thing attached to the second battery(deep cycle):

Ground Post:
One ground lead connected to first battery
One ground lead connecting AB amplifier for audio system

Positive Post:
One charging lead from one side of battery isolator
One positive lead from AB amplifier for audio system

Could the power for the radio be the issue? I have the remote turn on lead from the amp hooked to the head unit. Could this be the link enabling the 2 batteries to "see each other"? The main power is 8 gauge wire for both pos. and neg to the deep cycle battery but the remote turn on lead is that tiny blue wire that turns on the amp when the radio is powered on. The only other thing I can think of would be the radio power itself. It is powered by the first( original battery) and it is connected to the amplifier which is connected to the second battery.

To recap these are the only things I can thing of:

1. bad isolator
2. remote turn on lead for amp
3. power for head unit
4. common line grounding both batteries together

 

[PondTunes]

Re: My battery isolator doesn't seem to work

To recap these are the only things I can thing of:

1. bad isolator
2. remote turn on lead for amp
3. power for head unit
4. common line grounding both batteries together

1. Possible, but it seems that if it wasn't working it wouldn't charge either. Does it charge them?

2. The remote turn on shouldn't draw ANY power unless the head unit is on, it also shouldn't provide a path to the other battery as what it does is energize a circuit inside to power the amp up.
3. Constant power for the head unit could eventually drain your starting battery but it should take quite a long time. Your starting battery IS being drained while you play the audio system. (headunit drawing from the starting battery) so you may want to move the power to the radio to the 2nd battery.
4. This hookup is ok and won't cause any drain.

 

[Have Fun Today]

Re: My battery isolator doesn't seem to work

Before you spend too much time troubleshooting, do you know beyond a doubt that the isolator isn't working? Check the voltage at the second battery with the engine running. Use a voltmeter to compare it with primary battery voltage, should be the same. You may have to bump the engine slightly above idle to get the alternator voltage above the isolator voltage threshold (13.3 volts on mine).

Check the literature that came with your isolator, it might address the problems associated with having one battery bank drained to a low voltage level. May be that a simple charging of your deep cycle battery (using an external battery charger) is all you need to do.

I have an isolator that works great...I wired a simple selector switch (SPDT toggle type) to my in-dash voltmeter so I can check the voltage on either battery with engine off or on, a simple way to monitor each bus.

Also, if I can make a suggestion, normally one battery is reserved for the engine only, the second battery is used for the "house" bus and powers radios, amps, lights, blender, etc. This way your starting battery is never getting drained when your anchored at the sand bar.

 

[Zeusdafreak1]

Re: My battery isolator doesn't seem to work

I will do some checking and see if they are charging. I have NOT confirmed the voltage. I guess it is possible that neither battery has been charging at all and I just thought they were. Maybe it took this long to finally become an issue. the reason I don't think this is the issue is when we got to the sandbar I trimmed the motor and the power draw from the primary battery when doing this caused the amp to shut off which is hooked solely to the second battery. Thats how I knew they were seeing each other and the second battery(which I put back in the boat drained that morning) drained the primary battery by the time we got out there to the sandbar.

Thanks for info on each item. I wasn't sure about them. I am still kinda confused on how one is draining the other. I will try and gather more info as soon as I can.

 

[PondTunes]

Re: My battery isolator doesn't seem to work

One more thing what kind of engine is this all hooked to? Inboard? Outboard? A outboard will have a tough time charging two batteries at once. And It will take a little while to charge that deep cycle up from totally dead no matter what engine you're running. If the run you're making to the sand bar isn't very far and you don't have some rev's on the engine it's possible they just aren't charging enough. That being said charging the batteries when you get back might be the best option.

 

[Zeusdafreak1]

Re: My battery isolator doesn't seem to work

Its a 4.3 liter 190hp Mercruiser sterndrive with a 55 amp alternator.

 

[bruceb58]

Re: My battery isolator doesn't seem to work

You may have to bump the engine slightly above idle to get the alternator voltage above the isolator voltage threshold (13.3 volts on mine).

First off...isolators don't have threshold voltages. They are only diodes with a voltage drop across them. The voltage measured at the outputs of the isolator will be 0.7V - 0.3V less than the input depending on the type diode in the isolator.

Second, the problem with isolators is that they don't allow a deeply discharged battery to fully charge(will charge slowly) if the other is fully charged. That is why I prefer combiners.

 

[bruceb58]

Re: My battery isolator doesn't seem to work

I discovered that the drained second deep cycle pulled my original cranking battery down.

Sure seems like you have something common connecting the two systems.

Pull one of the cables off one of the batteries and measure the voltage of that open cable. If you measure a voltage, you have something common between the two systems.

 

[Zeusdafreak1]

Re: My battery isolator doesn't seem to work

Sure seems like you have something common connecting the two systems.

Pull one of the cables off one of the batteries and measure the voltage of that open cable. If you measure a voltage, you have something common between the two systems.

I will do that. Thanks a lot for the help. I wouldn't know what to do without you guys helping me.

 

[Boatist]

Re: My battery isolator doesn't seem to work

To test the isolator you can pull all three wires off the isolator. These are hot wires so make sure they are covered or at least that they do not contact anything metal.

With the batteries leads off the isolator and the alternator lead off the isolator you can now test the isolator with a OHM Meter. Set it on a low scale, times 10 or times 100. Never use the OHM scale if have voltage connected.

Put the red lead on the alternator post then touch each of the battery post. When you touch either post the meter should give you a reading.

Now put the black lead on the alternator post and again touch each battery post. In this direction the isolator diodes should not allow any current to flow. You should see it as a open circuit.

As Bruce said likely you have something connecting the two batteries external to the isolator, Maybe thru your radio.

One other point never discharge your deep cycle below 50 percent and Recharge as soon as possible if you want it to last a long time. Anytime discharged below 50 percent damage is done and the longer it is discharged the more damage is done. So recharge as soon at possible do not wait till the next trip or you will be buying a lot of batteries.

 

[Zeusdafreak1]

Re: My battery isolator doesn't seem to work

Took the boat out for the day today. It sounds awesome. Plenty of lows.

I went with 2-12 volt class 31 batteries wired in parallel for my secondary battery bank which leaves the main cranking battery still only powering the radio. This gives me 12 volts and adds the 125 amp hours each x 2 for a total of 250 amp hours.

I ran it for 3 straight hours and went from a starting voltage of 12.56 volts down to 12.25 volts after parking the boat this evening. This was a positive result. I figure I have plenty of reserve power to run the system another day but I am recharging anyway until I can get more time in to run it longer, etc.

If 10.5 volts is my stopping point I think I will be fine for bumping the sand bar all summer with minimal problems. With the boat running(its a stern drive) I am running off the alternator so all I need the battery bank for is once we park.

MY only issue now is recharging the minor voltage I pull off the cranking battery. It dropped down a bit from the head unit being on but when I cranked back up and ran for a while the alternator SEEMS to be charging the secondary system slightly but not really bringing my cranking battery back to full voltage. Both battery banks were at 12.25 volts when I got home. I don't know if this was a coincidence or not. The cranking battery should have been at 12.65 volts. This, I assume, is because the voltage of the two 12 volt deep cycle class 31 batteries is lower than the voltage of the cranking battery because I drained more power from them, therfore the voltage from the alternator isn't going towards recharging the cranking battery. Any thoughts on this one. I like having the radio on the main battery but may wind up having to change it if I cannot figure out it out.

 

[bruceb58]

Re: My battery isolator doesn't seem to work

If you let it get down to 10.5V you are going to be causing your batteries to have a short life. 11.9V would be my threshold. That would be measured with only a small load to get rid of any surface voltage. 11.9V is the 50% point. Any lower drastically reduces the overall capacity. I also would have gone with 2 Trojan 6V batteries instead of 2 12V batteries in series.

I would also get rid of the isolator and get a combiner. You will never fully charge your batteries with an isolator because of the voltage drop.

 

[Boatist]

Re: My battery isolator doesn't seem to work

I would start from the basic wiring. I assume you have all 3 battery grounds wired the the engine block.

Do you have a volt meter?

If you have a meter then on muff or in the water with the engine off measure the voltage on your starting battery and write it down.

Next measure the voltage on your other two gp 31 batteries and write it down.
Make all measurement from the engine block to the positive post on the battery.

Start the engine and set rpms to 1000.
Measure the voltage at the common wire on you isolator and write it down.

Next measure the voltage again on your starting battery positive post and write it down.

Last measure the vlotage again on your other two gp 31 batteries and write it down.

What you should see
Batteries if fully charged before you start should be 12.6 volts.

After starting the common connector on your isolator should be the same as you alternator output. This will normally be between 13.8 volts and 15 volts.

The output of you isolator for your starting battery should be the same voltage as the starting battery. The voltage of each of your isolator output and the postive post of the batteries should be no lower than .7 volts less than the common post on the isolator. So if the common post is 13.8 volts the battery post should be at least 13.1 volts. If the common post of the isolator is 15 volts then the battery post should be at least 14.3 volts.

With two Group 31 batteries and a starting battery it can take a long while to fully charge maybe 12 hours.

If it wired correctly then both battery banks should be higher than before you started the engine. So if you started with a voltage of 12.6 volts then with the motor running it should be higher and raising. What you would like to see is a battery voltage of 13.8 volts or more.

One last thing if your alternator has a external voltage regulator then you want the input of the regulator to come from the starting battery. This will eliminate any problem of voltage drop acrossed the battery isolator diodes.

Good Luck and report your findings.