Battery drain

[watglen]

D6R
Brand new Interstate bats last fall.

Over the winter the bats were found dead. Unit was in warm shop at the time so we charged them. Leaving the machine sit for a couple days drains the bats.

Finally, I made a point of turning off the disconnect, and the bats were dead the next time i checked!

Pulled both bats out, charged them, and started to monitor them. They both stay fully charged on the bench. Played around with them over a couple weeks and can't say there is anything wrong with them. Can't understand why they stay charged on the bench but drain when in the machine with the disconnect off.

Any experiences like this out there?

Ken

 

[funwithfuel]

Does your disconnect break power to cab or entire machine. I have had alternator diodes short to ground. Charge OK, no faults till the machine is shut off. Then they start discharging the batteries.
Is there a 12v keep alive for radios, phone chargers 2-ways etc. This would also be a potential drain.
If you have an old ammeter laying around, measure amps draw between beg post and chassis ground. More than half an amp, too much.
Good luck.

 

[DMiller]

With the disconnect open would be no different than sitting on the bench UNLESS some component was connected upstream of the disconnect

 

[funwithfuel]

Meant to say negative post and ground

 

[John C.]

I usually would disconnect one of the battery cables and put a test light between the cable and the terminal on the battery. If the light comes on you know current if flowing. From that point I start pulling fuses and connectors until I find the culprit. Other culprits are people hooking into one battery for some 12 volt accessory.

 

[Delmer]

... and by connectors, John C means the alternator, which is hooked up without a fuse.

 

[007]

Hi Watglen,
Typical vehicles which retain power on clocks and radios etc have very low current figures.
Any where between 30 to 100ma might be expected.
.5amps x 24V would be 12watts drain which would flatten your battery's quick smart.
The bulb test method is ok but use the smallest bulb you can find. (2watt dash bulb or less)
Can you explain how you are establishing your battery's are retaining there charge on the bench.
Are you just measuring the voltage, or load testing them, or just putting them back in the machine and seeing if it is cranking ok?

 

[watglen]

Hi 007 and everyone else, thanks for the input so far.

Yeah, on the bench I have several testers. I charged both bats and tested them seperately with digital voltmeter, one of those little electronic battery testers, and one of those cheap load testers that apply a load to heat an element. Over several weeks of monitoring, all the testers say the bats are fine, and stay charged around 12.3 V

I put them back in the dozer yesterday after cleaning the bat box, checking for bare wire, etc. I put a digital ammeter between the neg post and neg cable. With the switch turned on there is about .25-.3 amps draw. With the switch off there is exactly 0 draw. I cycled the switch many times and confirmed the draw is zero.

On the negative side there is only one big cable, between the disconnect switch and the neg battery post. There is a heavy jumper pos to neg on adjacent battery. Then, on bat 2, there is the heavy pos cable and many small wires associated with radios, monitors, gps, etc etc.

Will check it again this morning when I go out.

I wonder if its possible there is an intermittent short in one of the bats. The seller said bring them back no problem, but I don't want to get new bats (again) and continue to have the same problem. Grrr...

 

[007]

Each style of battery has different characteristics and you need to say what type you have and how many amp hour is there capacity.
If you have the older style flooded lead acid type a common problem was if the battery is exposed to vibration and rough up and down the active material can break loose of the plates and sink to the bottom of each cell.
The battery manufacturer leaves a space at the bottom to collect this material.
But in some cases the dislodged material fills that space completely and touches the bottom of the plates shorting them out causing high self discharge rates on the battery.
But the battery's when they reach that state are usually not cranking well because they have lost so much capacity.
It is possible you have stirred the bottom by man handling the battery's getting them out?
High sulfation on the bottom of the cells can cause self discharge as well.
There are battery rejuvenation liquid you can buy but i have never had any success with.
We used to put an excessively high charge on flooded battery to blow some of the sulfation off but that had low success also.
I suspect your battery's are getting sad and down on capacity for any number of reasons.
I say that because 12.3V standing voltage is low for a fully charged battery couple that with cold conditions and your parasite load of 7watts is high.
U realize the average car taillight bulb is 6 watts so you have a light on 24/7 running your bank down.
A proper charge and load test will tell you straight away if your battery's are tip top.


savhear seare If enough material

 

[funwithfuel]

Just a simple question, if you flip off the battery disconnect, then turn it back on. Does your radio lose its time and presets? Do you have access to your telematics(GPS) , is it reporting location with key off/ disconnect off when you ping it? If either of those are happening, you are not fully disconnected .

 

[Birken Vogt]

12.3 volts standing is not anywhere near fully charged, more like fully flat

 

[DMiller]

Birken is correct, a fully charged 12V battery sits around 12.8-13.4 MINIMUM as has six 2.2v(rough base v) cells inside. Sounds like a bad or iffy cell in at least one. Alternator needs to be running 13.8 to 14.4v output to keep a battery fully charged as has to be higher voltage to push amps.

 

[funwithfuel]

Guys , that might be true for AGM or spiral wound gel mat batteries. Flooded lead acid fully charged is 12.45v all day long. 12.3 is fine if the reserve capacity is sufficient. Have you checked water/acid levels in the cells? Do you have the means to check specific gravity

 

[DMiller]

Batteries for as long as I have worked in automotive have been a minimum of 2.1v/cell up to 2.2v, that is still over 12.6v minimum for a new battery. Used to be 6.3v minimum for a heavy cell 6v for 24v start series parallel systems in the 70's. Standard for lead acid cell batteries for forever.

 

[funwithfuel]

I'm out

 

[watglen]

Water levels are fine across both bats. I don't have a specific gravity tester.

Alternator output is 28 V running.

 

[DMiller]

Sorry I got the voltage incorrect, 28v is good for the 24v charge system, I cannot help defaulting to old truck numbers.

 

[Birken Vogt]

Guys , that might be true for AGM or spiral wound gel mat batteries. Flooded lead acid fully charged is 12.45v all day long. 12.3 is fine if the reserve capacity is sufficient. Have you checked water/acid levels in the cells? Do you have the means to check specific gravity

Sorry if I'm beating a dead horse here, but I don't even use AGM or gel batteries and when I go out in the yard to grab a good one for jump starting or whatever, 12.6 is the minimum I will grab if it has been sitting a while. 12.8 is not uncommon for a battery in good condition after weeks of sitting. 12.3, probably won't start whatever I put it on.

 

[DMiller]

Thanks BV, thought I was experiencing Old Timers disease or something.

 

[Dickjr.]

I thought everybody had a refractometer? Anyway , I have had new batteries go bad in the matter of months these days. They give me a new no problem. Could've been made on a Monday or Friday but it happens. Even a second could have gotten mixed in with the good ones.