Community Forums

robisinwa · 07-18-2021, 01:44 PM

So issue start last weekend... batteries got cooked while driving and then using the generator (god love the rotten egg smell!). Thought damn I am a poor maintenance guy not checking the batteries often enough for water though I had checked them 2-3 months ago). Batteries were 4ish years old so not a much deal per say, so got 4 new house batteries, all seemed well, so back on the road this weekend.

Camp all weekend, all systems working, used the generator, no problems... close everything up, start the engine, inverter control panel complains over high batt, stop charge message. Turn inverter off on control panel, get underneath, turn switch on inverter off there as well, go throw master switch on house batteries to off as well. Decide we'll deal with when we get home.

Barely get a mile, inverter burns up, shut everything done on the road, abandon ship with fire extinguishers in hand. Get into the mid-compartment where the inverter is, let the smoke clear and thankfully not an in process fire, just something burned up obviously. After removing the outer panel on the inverter, looks like the capacitors burned up. Disconnect all power sources from the inverter, have thrown all circuit breakers to off as well so all coach power should be dead.

Check engine batteries, good at 12.64v... get engine started again, check voltage on engine batteries again, check inverter its still dead, check engine batteries again looking good in the 12.48v range, back the coach up a mile (with a trailer attached mind you) to get back to boondocking camp space we were at.

New inverter is on order but ship to home since we're in a field quiet literally in the middle of no where.

Question is though, should I attempt or have a problem (with all 110 and low voltage off and inverted disconnected) to drive about 2 hours to home?

Thought maybe somehow alternator might have been supplying too high of voltage, but dash gauge has never shown it nor any issues with the engine batteries themselves. Truly seems all inverter related. I should have checked voltage to house batteries from inverter but again, thought it was my own poor maintenance of not maintaining battery water and obviously can't now that the inverter is literally fried.

Thoughts?

wolfe10 · 07-18-2021, 01:54 PM

Quote:

Originally Posted by robisinwa

Check engine batteries, good at 12.64v... get engine started again, check voltage on engine batteries again, check inverter its still dead, check engine batteries again looking good in the 12.48v range, back the coach up a mile (with a trailer attached mind you) to get back to boondocking camp space we were at.

If you are concerned about charge voltage from the alternator, please tell us voltage at the chassis batteries with engine at 1,100- 1,200 RPM.

Also, one or more of your batteries may be bad. That will cause an overcharge condition in all of them. If wet cell, buy a BATTERY HYDROMETER (under $10) and check the SG. Alternately, with them fully charged, disconnect and load test them individually.

robisinwa · 07-18-2021, 02:28 PM

12.36 on the engine batteries with engine running.

Totally get that a bad cell could have caused issue with the prior coach batteries the first time for over charging, being 4 years old I shrugged and decided yep, lets just replace. But now all 4 six volt batteries are brand new. And that couldn't have caused the inverter to literally burn up I wouldn't believe.

So my thinking is inverter going bad, 'caused problem with old batteries. Now inverter has gone bad, second problem. But I'm not seeing an issue with driving home unless someone tells me something I am missing.

wolfe10 · 07-18-2021, 02:35 PM

Quote:

Originally Posted by robisinwa

12.36 on the engine batteries with engine running.

No, at 12.36 VDC with engine running over 1,100 RPM, the charging system (alternator, battery isolator and/or wiring) is NOT working.

Ljwt330 · 07-18-2021, 04:09 PM

Quote:

Originally Posted by wolfe10

No, at 12.36 VDC with engine running over 1,100 RPM, the charging system (alternator, battery isolator and/or wiring) is NOT working.

Agree^^.

Alternator should be putting out more voltage to the batteries. Check out all systems from alternator to battery posts.

RobRoy · 07-18-2021, 05:00 PM

Quote:

Originally Posted by robisinwa

Check engine batteries, good at 12.64v... get engine started again, check voltage on engine batteries again, check inverter its still dead, check engine batteries again looking good in the 12.48v range, back the coach up a mile (with a trailer attached mind you) to get back to boondocking camp space we were at.

Question is though, should I attempt or have a problem (with all 110 and low voltage off and inverted disconnected) to drive about 2 hours to home?

Thought maybe somehow alternator might have been supplying too high of voltage, but dash gauge has never shown it nor any issues with the engine batteries themselves. Truly seems all inverter related. I should have checked voltage to house batteries from inverter but again, thought it was my own poor maintenance of not maintaining battery water and obviously can't now that the inverter is literally fried.

Thoughts?

So to try and answer your question.

As others stated it sounds like your alternator is not charging.

Do you have a way to connect the house battery's to the chassis battery's like jumping across the Big Boy relay? ( like the batt boost button does) and that may give you enough reserve capacity to get you home with all accessories in the coach shut down except the engine.

Are you towing a toad? if so?... you could POSIBLY rig jumper cables from the toad to the coach and leave the toad running on the journey home. That said I would not use the spring loaded jumper clamps to do so due to the possibility of shorting out.

I would get some battery cable eyelet ends from the local parts store or some other option other than using spring loaded jumper clamp ends in that situation.

Good luck

Happy Trails

robisinwa · 07-18-2021, 06:09 PM

So the item with blue fins... that's my battery isolator correct? It got cooked it would appear as well.

I wanted to try to test the alternator at the source, but its up in there with the leads not facing outwards so a wee bit racey to get up in there with my 18 inch testing leads while the engine is running. Of course I don't carry spare loose wire, any other ideas for testing the alternator?

Since we're someplace safe, so far I've elected to just sit put... I don't to run down the engine batteries with the 2 hour drive though if I don't run any accessories, in full sun, I would think the solar charger would keep them up enough to get home.

Thanks for everyone's comments so far.

robisinwa · 07-18-2021, 08:35 PM

With the engine off, I get the same reading on the engine post of the battery isolator as I do the battery so that checks out I believe.

Nothing on the center post with the engine off as one would expect, as I understand that to be from the alternator.

Once the engine is running, the center alternator post is typically nothing, but then jumps around up to 17, down to 3, 12, then nothing.

So if I'm trouble shooting correctly... alternator has an issue and based on cracking, battery isolator needs to be replaced as well.

I'm not quite getting how all that took out the inverter, assuming they are related.

wolfe10 · 07-18-2021, 08:40 PM

OK, you KNOW that that diode-based battery isolator is fried.

Replace it, verify that all connections at the alternator are clean and tight and THEN take new readings.

Make sure to check the small SENSE WIRE from somewhere on the chassis battery side of the battery isolator to the alternator sense terminal.

If you need a short term fix to get home, not difficult IF (yes, big IF) your only 12 VDC charging issue is the diode-based isolator. Just combine all three of the cables isolator onto ONE lug. That effectively makes one large battery bank of your chassis and house banks and is a direct connection to the cable from alternator B+ terminal. Again, verify sense wire as it is small gauge and can get lost.

twinboat · 07-18-2021, 08:51 PM

If your hitting 17 + volts, the alternator has lost the battery sense voltage from the chassis battery to the alternators regulator.

With out sensing battery voltage, the regulator, on the alternator, lets the alternator go full output, boiling batteries and overheating the isolator.

Look for the wire marked Duvac on the alternator. It should show chassis battery voltage.

If you recently replaced the alternator, it may be the wrong one. Temporary fix is to move the alternator wire from the center terminal of the isolator to the engine battery terminal. That lets the alternator sense battery voltage thru the large cable.

153stars · 07-18-2021, 09:01 PM

EDIT.....Okay you were getting help as I started my post. I had friends at local fireworks and rushed out after.Not trying to regurgitate their answers.
The center wire on isolator is alternator ,one side is chassis other is house. If diode to chassis battery died you could stack alt. wire on chassis post. I don't read many failed isolators but sounds like you had some stuff happen. I have read of an alternator fuse on smaller battery sense wire needed for Dulvac charging system.

153stars · 07-18-2021, 09:16 PM

You may want to also consider a Bluesea MTL ACR if your diode isolator is fried.
There's many posts on the swap replaces diode isolator and boost solenoid in one 4"x6" package. I just did it. I won't go into much there's enough for you to worry about at the moment.

wolfe10 · 07-19-2021, 07:37 AM

Quote:

Originally Posted by 153stars

You may want to also consider a Bluesea MTL ACR if your diode isolator is fried.

Yes, a good option to the old-technology diode-based isolator.

wolfe10 · 07-19-2021, 07:41 AM

Quote:

Originally Posted by twinboat

If your hitting 17 + volts, the alternator has lost the battery sense voltage from the chassis battery to the alternators regulator.

With out sensing battery voltage, the regulator, on the alternator, lets the alternator go full output, boiling batteries and overheating the isolator.

Absolutely, a loss of accurate chassis battery voltage to the sense terminal will cause overcharging (high voltage). Even a poor connection can provide the alternator with a false/low reading from the chassis battery.

Another cause could be that failed diode-based isolator. Speculating here on exactly what is wrong with it, but if the failure is such that the bridge between center lug (alternator B+) and the lug to the chassis battery then the chassis battery will not be charged and the sense wire will see a low voltage reading and ramp up voltage in an attempt to bring chassis battery voltage up.