Electrical What happened ?

Topic: Electrical What happened ? (Read 1122 times) previous topic - next topic

Electrical What happened ?

August 06, 2011, 09:33:30 pm

Returned t'day to home, ran for about 5 hours with genny running to power roof airs as temps across AR and MS were in high 90's.
On arrival we unloaded a little and when I went out to get more the lights were so dim in the bath that they were yellow. Checked house battery voltage on panel and found at 9.6, had to use boost to start genny , charge rate was 13.8 which is normal. When genny was shut down battery voltage dropped as I watched.
I have not had time to dig into this yet. Alternator is obviously working OK as dash panel shows correct voltage.
Is Isolator not working ? What can cause house batteries to die with genny running ?
I'll dig into it tomorrow but right now I am mystified.
Gary B

Re: Electrical What happened ?

Reply #1 – August 06, 2011, 11:44:41 pm

Gary,
How old are your house batteries? Sounds like a) isolator may be bad or b) batteries aren't taking a charge. Or, what about the 3-stage charger on your converter (Heart, or Xantrex or Iota)? Perhaps that has cratered.

Re: Electrical What happened ?

Reply #2 – August 07, 2011, 09:04:32 am

Gary,

Indeed a puzzler. For the inverter/charger to not work on generator power while driving and then work properly on generator later doesn't make sense. Perhaps a loose connection???

That the battery voltage dropped after running the generator the second time (when charging did occur) could make sense if there was insufficient run time for the inverter/charger to bring the batteries up to full charge.

The other, perhaps unrelated issue is why the alternator did not charge the house battery but did charge the engine battery (as indicated by dash gauges). That clearly points to the isolator or bad house batteries.

Clearly batteries and their connections could be involved in both scenarios.

Brett

Re: Electrical What happened ?

Reply #3 – August 08, 2011, 12:01:59 pm

Brett and Don, Finally got to take a look at battery problems. Pulled off cables and load tested, Voltage at both is 9.5 and load tester indicated WEAK. While messing with it I discovered that the positive connector on both batteries was loose. I cleaned and tightened all of them and now have inverter/charger on to see if they will charge back up. Hope that its that simple. If that takes care of it I will have to blame AR,MS and AL for their p... poor roads.
BTW one of the nicest stretches of road we saw on this trip was US 71/I 540 from Joplin, MO to Fort Smith, AR. With exception of one stretch at AR line there was only two stop lites and road is all new. Monstrous long grades thru the Boston mountains but that is why we have retarders and FT's.

Gary B

Re: Electrical What happened ?

Reply #4 – August 08, 2011, 03:40:34 pm

Sounds like you are talking about the new road... Now the old road was a real humdinger between Fort Smith and Fayetteville! Especially during an ice storm...

Re: Electrical What happened ?

Reply #5 – August 08, 2011, 04:43:35 pm

Dave, That is what surprised me, several years ago I remember this road as a real B...., its a pleasure now.

Re: Electrical What happened ?

Reply #6 – August 09, 2011, 11:06:49 am

Batteries have now been on coach charger for about 18 hours and still only show 10.5 volts. Load tester indicates WEAK. Indicator is in the area of 11 volts where it was as low as 8 volts so I have to conclude that batteries are taking SOME charge.
How long should I leave batteries on charge til I admit that they are not going to charge and need to be replaced ?

Re: Electrical What happened ?

Reply #7 – August 09, 2011, 11:33:00 am

Before I would write them off, I would check the voltage AT THE BATTERIES (on the battery post, not the terminal/connector) while charging. Do an A/B check between post voltage and connector/terminal voltage static and charging. You could then pull the connectors, isolate the batteries and then check voltage on each one. Could charge the batteries with an external charger with them disconnected from the coach. Even a small 6 amp charger should bring them into the 12V range in a few hours. Was thinking of the possibility that something else in your electrical system was rapidly drawing the batteries down (or not letting them charge).
How old are they? Rough road could have stirred up deposits on the bottom of the battery causing a cell to fail if older.

Digital voltmeter would be best here with pencil/paper to make battery map with voltages charging/not charging etc. Too many times I have checked something to find 30 seconds later it was in one ear out the other.

Re: Electrical What happened ?

Reply #8 – August 09, 2011, 11:40:03 am

Pierce, Voltage at the batteries with cables off is 10.5 volts after 18 hour charge..Digital VOM was used Actually the readout panel in the coach only shows 9.5.
I am leaning towards internal damage due to rough roads.
These are about 5 years old.
What really has me concerned is that generator did not keep batteries charged while running down the road. I have confirmed also that the alternator is working and charging the chassis batteries.
Gary B

Re: Electrical What happened ?

Reply #9 – August 09, 2011, 01:49:02 pm

Sounds as if you guessed right. Couple of 8Ds? One question. Did both batteries show the same voltage or was one OK? Five years seems like a short life but you never can tell.

As for battery life, do you leave coach plugged it at home or? What voltage do you usually have at the batteries when charging? Trying to figure if high voltage could have shortened their life. 13.8V is nominal charging voltage, up to 14.4V or so not uncommon. Start to look for regulator problems when voltage goes over 15V.

Ruling out anything else, if you have the batteries disconnected from each other and one is good, you could leave the bad one out (disconnected), run the generator and charge the other and check it after shut down. That way you can eliminate any isolator, etc. problems.

Re: Electrical What happened ?

Reply #10 – August 09, 2011, 01:53:31 pm

Actually, a float voltage (i.e. after batteries fully charged) of over 13.5 VDC will shorten battery life.

Brett

Re: Electrical What happened ?

Reply #11 – August 09, 2011, 02:25:59 pm

Quote from: wolfe10 – August 09, 2011, 01:53:31 pm

Actually, a float voltage (i.e. after batteries fully charged) of over 13.5 VDC will shorten battery life.

Brett

Brett,

Exactly!

I was speaking of a medium discharged battery at 13.8V as a charging rate only. Sustained 13.8 will shorten battery life considerably.

I usually just let my coach sit unplugged, check my digital voltmeters every few days and then charge with AC for an hour or so when voltage drops a bit. I never trust 110V not to somehow cause a problem if constantly connected. I have a 80 watt panel and have kept it plugged in the past but the regulator failed last winter so after ordering a new one, will keep bats up with it.

Re: Electrical What happened ?

Reply #12 – August 09, 2011, 03:00:11 pm

Batteries were disconnected and each tested WEAK and voltage after charging for about 18 hours is 10.5. They both test the same. I always leave coach plugged in and have never had a battery problem til now. Normally charge voltage is 13.XXX unless heavily discharged, then will show 14.2 til fully charged. These batteries were installed about five years ago when the seven year old batteries began to show signs of discharging quicker than usual. USUALLY, when batteries are dischag ed o'nite say while dry camping they will drop to 12.2 3 or 4 and an hour or so of genny time will recharge them.
Looks like I better start shopping for batteries. ( OUCH ).
Gary B

Re: Electrical What happened ?

Reply #13 – August 09, 2011, 03:39:47 pm

In my opinion, 13xx is too high for continual charge and will cut battery life considerably. Bill Chaplin has a cute little charger he made to JUST keep the batteries approx. 1265sg but not cut the lifespan. Ask for PDF. As I remember, his batteries have lasted almost forever. There are several posts on this forum regarding new chargers and pitfalls of older units like we or at least I have.

I bought 8Ds at Sam's Club for right at $100 each about three years ago for a Greyhound conversion I sold. Bought a couple 15 years or so ago also at Sam's Club that lasted years. Price was about $90 at the time so they have not gone up too much. Again, my opinion but I think a properly maintained SC 8D will be the least expensive house battery per year than any other choice. If they last 10 years, that is only $20/yr. Not bad. At half that, it's still not bad. I changed out to solar house batteries only because company went bankrupt and were absolutely dirt cheap.

Good thing about keeping batteries up is that it is almost impossible to freeze them in winter. As the specific gravity goes down the freezing point goes up until a flat battery will freeze and break the case not far below 32F if daytime temps are low.

Re: Electrical What happened ?

Reply #14 – August 09, 2011, 04:08:33 pm

I do love this subject, and would like to add from my 40+ years experience with emergency generator servicing, what has became perfectly clear.
On a 12 volt system, if you keep the battery floating at 12.95 and not over 13.000 volts, you can easy get 10 years out of a quality cranking battery. Most chargers are not adjustable and seem to love 13.3 volt float range, and these chargers shorten battery life to about 3 and maybe 4 years max. On these systems we change batteries out at 3 years to prevent the midnight emergency calls from a non starting genset due to dead battery.

Maybe a good place to mention not all batteries are quality built. I have mentioned before that we have best luck with Johnson Control Batteries for cranking batteries, we purchase them from a wholesaler who sends them back for recycle, once they exceed 60 days old. Funny why we never have battery issues due to these issues.
Highly recommend learning how to read the date code on battery, no date code, pass it up.
Enough for now but as usual FWIW

Re: Electrical What happened ?

Reply #15 – August 09, 2011, 08:47:06 pm

Gary,

My 12KW generator can't charge my house batteries to float in an hour. It takes more like four hours. If you're boondocking and not fully recharging your batteries, you're risking shortening the life of your batteries.

Re: Electrical What happened ?

Reply #16 – August 10, 2011, 08:20:08 am

Amos, I understand, what I meant was that if batteries were down after dry camping I could fire the genny for a couple hours and then leave out and depend on the alternator to finish up the charge while driving. I doubt that my 10K genny would charge house batteries in only an hour, I have never measured it but would probably take 4 to 5 hours depending on how low they were.
Gary B

Re: Electrical What happened ?

Reply #17 – August 12, 2011, 12:24:34 am

Each battery cell full voltage is 2.1 volts times 6 cells = 12.6 volts. When one cell fails with a short, battery voltage drops by 2.1 to 10.5 volts. When one cell fails open, battery voltage is zero.

Wet cell batteries can check each cell voltage with caps off, and with digital meter probes on end post and IN closest cell. Measure next cell with volt-meter probes in 1st cell and in 2nd cell. Continue until you reach the other post. Clean volt-meter probes as cell solution is acid.

Re: Electrical What happened ?

Reply #18 – August 12, 2011, 10:10:25 am

I have confirmed that BOTH 8D AGM's are dead and will not take a charge. Again, I think it was due to severe road conditions and heat that did these 5 year old batteries in.
After shopping around I found replacements at anywhere from $650 to $399.
After confirming that East Penn makes O'Reilley's batteries I ordered them . At $399 and no freight or core charges this was the best price I could find. In addition I find that batteries at the recyclers are worth 25 cents a pound so I will recover a little of the cost.
Thanks to all for info and tips on batteries.
Gary B

Re: Electrical What happened ?

Reply #19 – August 12, 2011, 11:08:54 am

Quote from: Gary Bouland – August 12, 2011, 10:10:25 am

I find that batteries at the recyclers are worth 25 cents a pound so I will recover a little of the cost.
Thanks to all for info and tips on batteries.
Gary B

That is good if you are close enough to one to make it worth while. but if you had to haul it any distance???

Affiliate Notice