Bosch battery shows 12,5 volts

BlueonBlue

My std bosch S4 026 type 068 battery shows 12.5 volts when first put on a charger then after charging hits 13.5 to 13.7 volts but drops back to 12.5volts a day or so later on the bench .
Its 3years 9 months old from manufacture according to the coded stamped numbers on the battery.
Bosch S4 are 4 year batterys .

Does this reading give any indication of its health or is this reading pointless and needs a proper stress test elsewhere 

MattMattMattUK

BlueonBlue said:

My std bosch S4 026 type 068 battery shows 12.5 volts when first put on a charger then after charging hits 13.5 to 13.7 volts but drops back to 12.5volts a day or so later on the bench .
Its 3years 9 months old from manufacture according to the coded stamped numbers on the battery.
Bosch S4 are 4 year batterys .

Does this reading give any indication of its health or is this reading pointless and needs a proper stress test elsewhere 

It does not indicate anything, in a best case scenario in a lab one might be able to gain some mildly useful information from voltage readings, with controlled temperature and load and analysing voltage drops over time etc. but nothing useful from what you have there.

Why do you feel the battery needs a stress test?

Stubod

..seems about right to me???.....I regularly put our "other" car on charge if it does not get used for more than a week. I always check the voltage before I put it on charge and it is around 12.4 volts, after charging it reads 13.4v...

BlueonBlue

I just needed to know more on this in general without visiting ECP for a test and if the  voltage info I gave indicated anything or doesnt help much .
My feeling was the battery is probably still ok ;
Its a spare as I have a S4 024 type 005 manufactured in 2018 from the coded numbers that is still doing fine .
I would like to be able to test batterys at home but imagine that requires expensive kit not diy tools like a digital battery charger

droopsnoot

^ Machine Mart do a battery drop tester for around £45, but a lot of car service places will have one, you might be able to ask one of them to test it for you. The one I used recently showed the percentage of the original CCA figure and used it to determine battery state.

Mildly_Miffed

12.5V is about right for a fully charged lead acid battery, give or take a little for a less-than-calibrated meter.

Anything above that, freshly off-charge, is simply the battery returning to normal after being on charge - it can take up to an hour or so.

Rest voltage, though, is no real guarantee of battery health. It's how well it copes with a big load.

Rodders53

12.5 Volts after surface charge removal (few days off charge or halogen headlights on for a couple of minutes) for a maintenance free wet lead acid battery (Ca/Ca) at 21 C is, according to my spreadsheet for State of Charge somewhere near or just under 75%...  Approximately 12.8 Volts would be 100% State of Charge.

13.7 or even 13.8 Volts peak charging voltage is not sufficient to fully charge the battery.  Get a smart charger from Lidl/Aldi or Halfords... or CTEK if money is aplenty. They'll peak to over 14 Volts as part of the charging cycle.

forgotmyname

12.5v reading is pointless unless you put the battery under load. when testing.

I have an old wheelchair 12v battery which shows 12.4v but putting just a 5w bulb on it causes the voltage to
drop to 11v.  It charges daily with a solar panel and runs a circuit that only requires 1.5v and a tiny current so
will do the job for a good while yet but useless for anything else.

BlueonBlue

Ideally a load or stress test would be great but trusting anything euro car parts say and do after a test isnt sensible imo as they have no interest in not selling me a battery .

I have and use a Ultimate Speed ULG 12 A2 which is now a older larger type battery charger as in link below.
https://www.manua.ls/ultimate-speed/ulg-12-a2/manual
Its a little odd to use at times or perhaps I dont understand its use but it has charged batterys well and worked for a number of years now 

My other slighly older battery a Bosch S4 024 type 005 was 12.7 -12.8volts after charging so did show a higher reading than this S4 026 battery  which only showed 12.5volts.