Thread: Battery Question

Originally Posted by Disco95

Hmmm, the plot thickens. Now I don't know what to think.
I generally trust what I see, it seems a bit of a coincidence that I've had 2 x batteries go at once. I'll have to quiz my neighbour on where he got his info, and what he bought to stop it happening. He did tell me but I was busy at the time and can't remember what it was. He's a construction engineer with the council, building approvals and all that.
Now, I'm running an isolator that only lets the starting battery get down to 12 volts or something similar before isolating the batteries. When the vehicle's running there's 14.5 volts coming from the alternator so the batteries aren't isolated. I know my alternator works also.
So, what do I know:
1. my starter's good
2. my alternator's good
3. my positive and earths are good
4. the trigger wire connection is good
5. the vehicle jump starts fine
6. a new battery, and the small used one from my 4 cylinder honda start the vehicle well
7. the 2 x batteries that were in the vehicle for the past 2 years (one of those is about 3 1/2 years old) don't start the car even after charging for a long time.
8. Both these batteries read 12.5 volts on 2 different multi meters

What would you surmise from all that?

Sean, going on the fact that your batteries are getting on, I would surmise that they may be Sulphated up and on the way to the scrap yard. If the battery out of your wifes car starts the Disco OK then it points to the batteries being crook. You can try putting a bottle of Inox battery conditioner in each battery (about $7.50 ea.) which will break up the Sulphation of the lead plates and allow your battery to take and hold a full charge. Also invest a few $'s in a Hydrometer (one of those plastic tubes with the float inside and the rubber bulb one one end) which is essential to check the state of the battery and very useful for transferring battery acid to your toolbox. If you go the Inox route put your batteries on charge for a few days and check the electrolyte regularly, they may come back to life and you will get some more mileage out of your batteries, let us know how you go, Regards Frank.

G'day Frank, I did the inox route with the older of the two batteries and had no joy.
This particular one was getting toward the end of its life I'd suspect.
I'm going to try the other one at some stage, but for now I've bought a new battery.

Hi Disco95, take the two batteries to an auto electrician or a battery centre and have them load tested.

The test is free and will tell you immediately if the batteries are good or stuffed.

Cheers.

Your batteries are stuffed if they are only holding 12.5 V. On a multimeter that is a no load open circuit voltage. If you put a load on and test for voltage your batteries are not likely to hold that 12.5 V, as drive safe said get them tested with a load and you will know.

I have never heard good reports about trying to recondition a battery once sulphated. Best to maintain your battery so it does not get sulphated in the first place.

What he said! 12.5 is not good-- 13.1 ish is good --if it doesnt work under load its Kapootsa. Probably a dropped cell id say. check your cells for low water, dirtyness, swelling and the dead giveaway is acid (white ****) build up on terminals even when its not under constant load.

12.6 volts is a fully charged battery. But readings should only been taken after the motor has been switched off for a while. While charging the battery will read up to 14.5 volts and the voltage can take a little while to settle back once you stop the charging.

regarding your neighbor and his boats too.. chances are he originally had a switch to switch the batteries they give an option of off, batt1, batt2, batt1+batt2

to charge both you have to switch it to batt1+batt2 to and for chargind batt1 it s batt1 etc.

im assuming this is why the batteries died as one was pulling the other down.. and he probably had it switched to both.

this is why on my boat i have a dual circuit switch which switches both batteries on.. but to different circuits (aux and crank) and doesnt join them. the only join i have between the batteries is one of drivesafes sc40's which pulls the crank battery down a bit (but safely) then isolates it.. but then opens up when the motor is running. if my crank battery dies however i also have a combine position on the switch which in effect lets me use the aux battery to jump start the motor.

all this and i dont have to remember to set the switch to charge the batteries

Surface charge is very misleading.. all you need to do is put your multimeter across the battery and wire a bulb (globe) across the battery terminals and you will see the voltage dip (with enough power being drawn)

Thanks

Steve

quick test

turn on the ignition (dont start)
turn on high beam
turn the heater fan on flat out
check the voltage

if its 12.5 and dropping noticeably thats bad
if its under 12 thats worse.
under 11 its toast and
under 10.5 and you wont have enough to get the ECU to fire the injectors on a td5 and on an EFI petrol engine you may not have enough to get the fuel rail up to pressure or reliabley fire the electronic ignition while cranking, (if you can get it to crank)