How To Check An Isolator

[insuranceman52]

I have a Powerline HEHR 22-27 (PLI160-20) ISOLATOR I'm trying to figure out how to test. My coach batteries was overcharging, boiling, fuming etc and we feel like the isolator is the culprit. This has 3 large terminals on top. Something that is confusing me is the label on the side. It say: 1. main bat: 2. Aux bat: A alt: and 3 aux bat. It seems to have labels for four terminals...but there are only three.

Can someone help me??

Gary

[wolfe10]

Gary,

Hehr has some pretty good troubleshooting manuals on their website: http://www.hehr-international.com/hehr%20power%20systems%20index.html

Brett

[insuranceman52]

I went to the HEHR website....all I see is windows, glass, etc. I don't see electrical or isolators. Help

Thank you for your earlier reply.

Gary

[wolfe10]

Gary,

When you click on the link I posted above-- should be what you are looking for:

Hehr Power Systems

Hehr Power Systems, a division of Hehr International Inc., manufactures a wide range of electrical products for the automotive, RV, marine, transit, and emergency services industries--including POWERLINE Heavy Duty alternators, Aqualine marine regulators, and POWERLINE multi-battery isolators. The manufacturing plant is located in Ft. Worth, Texas, and the Division Director, Sales Manager and their staff work closely with OEM's and a strong distributor network for widespread product availability throughout the United States, Canada and other countries.

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[insuranceman52]

Thank you.

Gary

[chucknewman]

Gary,

I noticed in Google engine you have posted this question on several boards. Your statement "My coach batteries was overcharging, boiling, fuming..." has nothing to do with the isolator. Overcharged batteries are the result of inverter/charger or alternator regulator issues.

If the coach batteries are overcharging when driving, then the engine batteries will do the same. This is the result of a defective alternator regulator.

If the engine batteries are OK and the coach batteries are overcharging when the coach is plugged in, you have a inverter/charger or converter problem, depending on what is installed in your coach.

The isolator merely directs DC voltage from the alternator connected to the center terminal, to both outside terminals. One outside terminal is connected to the coach batteries; the other outside terminal is connected to the engine batteries. The two outside terminals are "isolated" from each other so one set of batteries will not send current into the other set of batteries. It has no voltage regulation characteristics. That is the function of the battery charger/converter and vehicle alternator.

Check the coach batteries when charging while plugged in. They should be between 13.2 vdc and 14.0 vdc(depending of state of battery and type of charger) when fully charged and receiving a maintenance charge. Shut off all DC operated appliances and lights, HWH, furnace, fans, etc. to get an accurate charge reading. I would imagine you will see over 14.0 vdc continuously which will boil out the electrolyte in the batteries.

[wolfe10]

To add to Chuck's post, batteries with a bad cell can cause boiling and fuming, even with a perfectly working alternator, isolator and/or battery charger.

The charging source knows it is supposed to maintain 13.2+ VDC. If the battery has a bad cell, the charging source will try to charge a 10 VDC battery (one dead cell) at 13.2 VDC. So, though the charging source is maintaining exactly the correct voltage, the battery(s) will boil and fume.

IMPORTANT: Have you actually measured voltage at the battery? If so, what reading do you get?

Brett

[PhilOien]

I have this same problem with my house batteries overcharging, and my engine battery not whenever the engine rpms are above idle. I noticed the problem after my inverter (Heart Interface 2500) started shutting down from an over-voltage condition when we were underway, and the a/c outlets stopped working.

I've checked the voltages at the batteries with the hi-idle on and the engine batteries were at 14.4 and the house batteries were at 16.2 upon arriving home after a trip (all fully charged). I removed all the batteries from the coach, and removed all the wires from the isolator terminals. I checked the isolator, a Powerline 190 amp, with a multimeter that has the diode check function. With the meter positive on the center terminal, the forward biased voltage drops were 0.453v and 0.481, and with the meter negative on the center terminal, the reverse bias was infinity, so the isolator checks good with this test.

However, I wanted to test the isolator when it was carrying a charge current, so I split my house batteries into 2 banks, with a common negative, and the positives run with some identical 10 ft. 2 ga cables with ring terminals to the outboard terminals on the isolator. I attached a separate 2 ft. 2 ga cable with a ring terminal on one end and a lead post terminal on the other end to the center terminal of the isolator. I tightened all the connections, and hooked my big portable charger/booster up to charge the 2 banks thru the isolator; each thru a separate diode bank of the isolator.

Both battery banks (6v golfcart) were at 12.88 volts to start. There was an immediate difference in applied voltage between each bank, and it increased as I went from low to medium to high to start on the charger charge settings. I measured the voltage drops across the 2 diode banks, and they were 3.2v and 2.2 volts when on high.

There is at least 1 volt difference in the voltage drops across the diode banks, so to assume that whatever the alternator is putting out is applied equally to both banks is incorrect. My isolator works, but probably has a problem (as the original poster was thinking).

The link above to the Hehr website doesn't work from my iPhone. The server cannot be found. I'd like to troubleshoot the isolator before I buy a new one, or get something better, since the price is the same.

[desertdeals69]

I have this same problem with my house batteries overcharging, and my engine battery not whenever the engine rpms are above idle. I noticed the problem after my inverter (Heart Interface 2500) started shutting down from an over-voltage condition when we were underway, and the a/c outlets stopped working.

I've checked the voltages at the batteries with the hi-idle on and the engine batteries were at 14.4 and the house batteries were at 16.2 upon arriving home after a trip (all fully charged). I removed all the batteries from the coach, and removed all the wires from the isolator terminals. I checked the isolator, a Powerline 190 amp, with a multimeter that has the diode check function. With the meter positive on the center terminal, the forward biased voltage drops were 0.453v and 0.481, and with the meter negative on the center terminal, the reverse bias was infinity, so the isolator checks good with this test.

However, I wanted to test the isolator when it was carrying a charge current, so I split my house batteries into 2 banks, with a common negative, and the positives run with some identical 10 ft. 2 ga cables with ring terminals to the outboard terminals on the isolator. I attached a separate 2 ft. 2 ga cable with a ring terminal on one end and a lead post terminal on the other end to the center terminal of the isolator. I tightened all the connections, and hooked my big portable charger/booster up to charge the 2 banks thru the isolator; each thru a separate diode bank of the isolator.

Both battery banks (6v golfcart) were at 12.88 volts to start. There was an immediate difference in applied voltage between each bank, and it increased as I went from low to medium to high to start on the charger charge settings. I measured the voltage drops across the 2 diode banks, and they were 3.2v and 2.2 volts when on high.

There is at least 1 volt difference in the voltage drops across the diode banks, so to assume that whatever the alternator is putting out is applied equally to both banks is incorrect. My isolator works, but probably has a problem (as the original poster was thinking).

The link above to the Hehr website doesn't work from my iPhone. The server cannot be found. I'd like to troubleshoot the isolator before I buy a new one, or get something better, since the price is the same.

Isolators do lower voltage so they are not the best way to hook both banks together. Using a solenoid would not lower the charge voltage.

[wolfe10]

Yes, diode-based isolators do turn some voltage into HEAT (that is why they have the large aluminum cooling fins). But the drop across the diode to the chassis battery should not be materially different from the drop across the diode to the house battery. THAT is the issue here.

And the voltage drop (assuming close to the same) is a non issue if the alternator/regulator has an EXTERNAL SENSE WIRE that senses voltage "downstream" of the diode based isolator. Yes, that makes the alternator work a little harder, but no huge deal. As an example, if the regulator is set to 14.0 VDC and the sense wire is on the chassis battery lug of the isolator (the common location), the regulator will work the alternator to put out the 14.0 at the "far side" of the diode-based isolator. So measuring voltage at the alternator will be 14.0 plus loss across the diode of about .7 so reading at the alternator would be around 14.7 VDC.

There are three common ways to isolate battery banks, yet have them combined when you want for charging.

The simplest (and manual) is a simple marine ON-OFF switch. Alternator output and chassis battery are on one lug and House battery on the other. Switch OFF and alternator charges only chassis battery. Switch ON and alternator charges both battery banks.

Then the two "automatic" solutions: Diode-based isolators and Solenoid-based isolators.

[PhilOien]

Hi Brett, thanks for your rapid response. I was curious if anyone had any experience with the different voltage drops across the 2 isolator channels. I have a 1996 Country Coach Magna with a Leece Neville alternator with the "sense" lead as you mention, and everything has worked automatically for years, until recently, when the inverter started shutting down. The house batteries are about 10 months old, and the engine battery (San Diego, so I only use one) is only a month old, but the problem started about a month after I replaced the house batteries. I do almost exclusively "dry camping" and like to recharge things when underway. I also prefer to keep things automatic, because automatic means I don't have to remember to isolate when it's needed. I put all the troubleshooting details in my post to maybe assist others in their own troubleshooting. I'm a DIY for most things (I like to put money in the fuel tank, not Techs' pockets), and this gremlin is a new one for me, and I've been a professional mechanic for 25 years with a electronics technical school diploma foundation. I know PowerLine doesn't actually manufacture the diodes in the isolator (a semiconductor company does) so I'm inclined to see if I can take apart the isolator, even if it means I destroy the isolator in the process (it's not working right, anyways) to discover what's going on. I'm guessing that the isolator is two banks of diodes in parallel and that possibly one bank has had one or more , but not all of the diodes burn out, not short out, causing the forward resistance to increase and thereby increase the voltage drop. I don't know what's going on, but like I said, I was just curious if anyone has any experience in this area.