The Stovebolt Site Forums The Shop Area The Electrical Bay smelly battery

Hi all I took my truck out for nice drive today for about an hour and a half and when I got back noticed both my muffler clamps were broken. No problem I can fix that up but the battery was hissing and smelt really horrible. Ever heard this one before. Also not sure if I have this posted in the right spot. Thanks rick

sounds like it may have been overcharging, might check the gen/regulator or alternator for proper function

Bill

What am I checking for or how

Voltmeter on battery before start=12.6V after start=14-15V. More than that=overcharging. Also you could have a leaking or bad battery. Sometimes they do "blow up". Especially if they get HOT! and Smell!! Give it some high idle to see if charge goes over 15V.

I would check the fluid level first. It really does sound like it is overcharging.

check your charging system and water level in the battery ( that hiss was the vent and for sure was pushing out fumes/boiled over water from the battery)but more likely then not you'll have to replace the battery, because it is for sure over charging and if it's been overcharged for awhile it usually turns the battery into scrap. but check into that stuff and see if it will hold charge after the problem has been fixed.

bartamos is right they do blow up if kept overcharging you may even notice your battery has a bulge somewhere on the sides of it now

OK I know it is lead acid battery
BUT what configuration?

Gel cell, or other sealed types
OR
wet cell battery.

IF wet cell and you have electrolyte covering the plates (that is all you need) then should not smell. Even on overcharge it should not smell UNLESS you are overheating. Check temperature (do not touch plates with metal thermometer) and check voltage 15 is good value for maximum voltage.

IF sealed unit some of them have 14.4 max voltage. The "hissing" makes me think this is what you have.

Blowing up - if you overcharge a sealed unit then pressure builds up inside. If relief valves cannot keep up with pressure change the case gets overpressurized and can rupture.

Dan Bentler

it doesn't have to be charging over 14-15V to be over charging, what's needed is for the regulator [internal or external] to be bad so it's constantly feeding max charging current even tho the battery is/was fully charged, that's why plug-in battery chargers work in stages and taper off the charging current as the battery slows the rate it's taking amps ... any type battery that's overcharged will be getting hot, and any battery that's 'hissing' is gassing off hydrogen [explosive], wetcell, AGM or gel - also any overcharged battery will be damaged to some extent by sulphation from overcharging and should be checked properly by a shop that can evaluate it's load capacity

Bill

Hi all just had my friend check with a voltmeter and as you said it was 12.75 not running then shot up 16 when I started it. He says it must be the voltage regulator. Do you know if you adjust these or do I just buy a new one? Can you still get new ones or do you have them rebuilt?.
Thanks Rick

any of the vendors will have regulators, as well as most local parts stores like NAPA - the original regulators are adjustable, but it could be more than just adjustment, and the best way to deal with that would be to have a good auto electric shop check/adjust it - also be a good idea to have the battery professionally checked before you spend money on other things

Bill

OK I bought and installed the voltage regulator. The battery tester is reading full charge but when I try to start it just barely gives me one little grunt. Not nearly enough to start it. Is it possible that the bat is giving a false reading? Should I try to give it a boost with another truck. I put a charger on as well and it said it was full as well. When I tried to start it with the old v reg it started no problem.

if you abused that battery enough for it to be off-gassing and stinking, it's damaged - did you get the battery tested at a shop? load tested? are you sure you got all the connections back correctly and tight on clean terminals? especially all ground connections? did you polarize the regulator when you installed it? do you have an auto electric shop around that could check things out?

Bill

I followed the instruction very carefully . Yes I did polarize. I Marked off the wires before taking them off. I have not had the bat load tested. I'm not positive what that is. I assume if it is reading full then it should be working. If I have to have it tested I am sure around here it will cost half of a new bat

Sulfation is produced by the discharge cycle. It is driven back ie removed during the charge cycle.

If battery is fully charged and you are still seeing a high current you must reduce voltage. Ohms Law does apply to batteries since they have an internal resistance. Current is the result of a voltage applied to a resistance

Dan Bentler

a load test indicates if the voltage your meter is reading is really backed up by the amps the battery is rated at {"CCA"], that is, when you call for full power can the battery deliver it - many places that sell batteries test them for free, NAPA here will do it ... even if it costs a few bucks it might save you throwing money at things until you realize the battery is the remaining problem

a quick search of your area finds a dozen or more shops that offer electrical repairs, consult one of them to find out just what the problem is

Bill

quick way to see if the battery is killing during start is, put a voltmeter on the battery see your reading then try and start the vehicle (with the voltmeter on it the whole time) then see if the voltage drops significantly when trying to start. if your saying that it basically does nothing when u try and start chances are your battery is no good, and you'll see the voltage drop down as soon as u go to start. you also can do the same thing but check amps.

After what happened to your battery i'm sure its no good, I personally always change boiled over/over charged batteries.

best of luck

Came home and tried to start. It started right up ran it for awhile meter says just under 14 revved up. I will see if it starts again after dinner but will get load test anyway maybe get a new bat also anyway

Tried to start again after dinner but it was dead going for a load test

Load test says bad dead. Got a new one gonna try it. Do I need to do anything first

hook it up and try it out, if it starts, check what's happening with charging, a bad battery could have damaged the new regulator

Bill

Guess I'm lucky all seems to be fine 12.75 when off and 14.75 idling high

Hi red 58 I noticed earlier you said it should not keep delervering a Max charge it should go up and down. When I put the tester on it for about a minute
I revved it for about a minute and it fluxuated between 14.75 and 14.86 maybe, never went over or near 15. How much should it fluxuate and over what time period

you misinterpreted Rick, a plug in battery charger will change the 'rate of charge' depending on how "smart" it is [amps, not volts] - an auto regulator should deliver a steady voltage that may vary slightly with RPM, with the amount of current sent to the battery depending on battery condition - sounds like yours is doing the job now

notice your ammeter right after you start the truck, when cranking it should show a discharge [indicating current is flowing out of the battery], as soon as started the meter should show some amount of charge, indicating the regulator is sending some or all of the amps produced by the generator to the battery, and that rate of charge will taper off as the battery returns to fully charged, so the meter will return to 'neutral'

Bill

Great thanks red, yes I think it is working OK now took it far 30 minute run and came home , no smell. I felt the bat and it was not hot at all. When my son gets home I will try starting with the meter on to see if it goes down a bit as you describe. Thanks for your help. Rick

Red58's right on the money with his advice. I had a '73 Monte Carlo,with an internal regulator in the alternator. The regulator diode went bad,which fried the regulator,alternator,and the wet-cell battery! It was hissing,and smelled like cooked rotten eggs. And the case had a bulge in both sides. EXPENSIVE!