battery problem i think ...

gorrie · Post by **gorrie** » Wed Jan 16, 2008 10:29 am

It's more mileage than mine gets...

scott_e · Post by **scott_e** » Wed Jan 16, 2008 10:34 am

gorrie wrote:It's more mileage than mine gets...

mmm. so it may not be battery.

I have a electrical test voltage meter with me here.

Do i set it to AC then the 20V range ?

fd · Post by fd » Wed Jan 16, 2008 10:58 am

DC, 20V range . . .

as Robin said you cannot 'take out more than you are putting in' with a modern alternator / car . . . you're sat nav left on all the time will, however, screw things up - disconnect it when you're not driving.

Unlike dynamos (which I havn't seen in a car for decades) modern alternators will supply 80+ AMPS continuously at ~14.5 Volts at idle or very close to it . . . which is far more than is required to run the car and charge the battery, it will take the alternator only couple of minutes to replace the energy required to start the engine even with everything else switched on, so unless the alt is fecked or the battery has failed (it does happen) then you are left looking for something else . . . like your satnav perhaps - draining the battery every night . . . something that will eventually kill the battery in any car.

Fd

scott_e · Post by **scott_e** » Wed Jan 16, 2008 11:11 am

Thanks for the reply FD. So if i:

- purchase tricker charger + bat boot pack
- test the voltage on old bat (DC)
- tricker charge
- see if it drops then disconnect
- if it does its another prob and i give mmc a call

how long do i have before the imobiliser drains ?

thanks for all the help everyone
scott

fd · Post by fd » Wed Jan 16, 2008 11:32 am

battery voltage with a good battery and engine running should be >13.5 Volts, probably 14v, may be as high as 14.5V.

battery voltage with fully charged battery and engine NOT running should be ~13.2V

Your list of steps are reasonable . . . but I would bench charge the current battery with a decent charger (20A+ output) before buying a new one, if you don't have a decent charger then perhaps just buy the battery . . . that way you are up and running again . . .

With flat car batteries BIG chargers are better . . . even with a 20A charger it could take 12 hours to fully charge a very flat battery . . . with a 5A charger that turns into 2 days . . . also with very flat batteries you should fast charge them for 1/2 hour before going into normal charging speed - apparetly this helps the chemistry on the plates recover from having been fully flat better (the reason why decent chargers have a 'boost' or 'high' charge setting).

The best charger you have is in the car . . . the alternator . . .

Fd

scott_e · Post by **scott_e** » Wed Jan 16, 2008 1:36 pm

http://www.halfords.com/webapp/wcs/stor ... ryId_31335

is this ok for boosting the battery instead of jump leads ?

steve_weegie · Post by **steve_weegie** » Wed Jan 16, 2008 2:40 pm

Looks like a decent 10 amp battery charger, but it's not a battery booster that will allow you to start the engine almost immediatly like jump leads will. You'll need to leave it on charge for a while before you can start the engine and take the car for a run to charge it properly.

If the battery has deep discharged many times, it will result in a permanant capacity loss and this could be the root of your problems. Car batteries are designed to provide very large starting currents for a short period, rather than a constant current for long periods.

Your symptoms are pretty similar to what i experienced 1 month ago. No matter how long i charged the battery for, it was simply done in!

scott_e · Post by **scott_e** » Wed Jan 16, 2008 2:44 pm

thanks for reply steve.

can you recommend a battery booster from halfords / B&Q ?

can you reommend a trickle charger from halfords / B&Q ?

not too sure what im looking for.

As you say may need battery as well but found the booster worked really well last night so would like to get one today.

Rich H · Post by **Rich H** » Wed Jan 16, 2008 2:50 pm

I have used battery conditioner tablets with success, bringing totally wrecked batteries back to life.

gorrie · Post by **gorrie** » Wed Jan 16, 2008 2:55 pm

Scott... the one in the link I gave you does the lot... the halfords own make, and at a decent price. It does pulse charging (which is better than traditional trickle) and it will charge a run down battery, as long as it isn't completely f3cked. I think that B&D one is also in that group test & scored well (but more pricey)

Even my charger (the Gunson one which was in the same group test) does traditional trickle & I recently used it to charge on almost flat battery that I removed from the elise.

If removing the battery terminals, I think you need to make sure you do it within 30 seconds of turning off the alarm/imobiliser (ie, before the imobiliser re-activates)... otherwise it's a PITA.

scott_e · Post by **scott_e** » Wed Jan 16, 2008 3:01 pm

gorrie, thanks. did not relise you edited the post sorry.

steve_weegie · Post by **steve_weegie** » Wed Jan 16, 2008 3:08 pm

Scott, Id use a booster as a last resort - you'll get much better performance from poping the battery out the car and bench charging it overnight. You can also use a charger to keep the battery topped up if you're not using the car for a couple of weeks. As i said, car batteries dont like being deeply discharged - if you can keep it topped up by using the car loads (fun option) or trickle charging it every week (boring option) the battery will last a whole lot longer.

The booster can be used for short term emergencies, but until you get as much charge in the battery as it will take, you wont know if you need a new battery.

I however suspect you do need a new battery! A decent battery in decent nick will give you enough juce to start the car after 10 mins of running from a jump start in my experience. If yours doesnt do this, or looses a lot of charge overnight, its time for a replacement.

HTH

Steve

scott_e · Post by **scott_e** » Wed Jan 16, 2008 6:49 pm

hi,

1. ok purchased a trickle charger.
2. took out battery
3. plugged into mains
4. charged for 1 min
5. disconnected from main
6. plugged into car
7. started car.
8. voltage reads 14.2
9. stopped car left for 5 mins
10. voltage read 12.3 seems steady so far
11. started car again
12. leaving is for a while to see if Voltage goes up while running

all lights, radio, sat nav off / unplugged.

can anyone offer advice ?

scott_e · Post by **scott_e** » Wed Jan 16, 2008 6:55 pm

voltage stays at 14.2 while running.

scott_e · Post by **scott_e** » Wed Jan 16, 2008 6:58 pm

dont want to disconnect battery from the car again just in case it causes imobiliser problems.

can i disconnect to charge overnight or should i leave it connected while charging ?