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[megas]

hi, bought the car just a few months ago. if i leave it for a couple of days and go and start her shes fine, but if i sit in it with radio on for any amount of time the battery go dead. is to  do with not enough water in the battery for it to hold a sufficent charge or has the alternator gone up the duff.

getting tired of asking for a jump.

[biker]

could be both, have it tested for charging at local (halfords its free)       or garage eitherway you will get your answer,
Merry xmas.
Dave.

[TheBoy]

I'd be changing battery, but first just measure charging voltage is OK

[Kevin Wood]

Another thing to check is the connection at the positive bnattery terminal. These get weak where the larger of the cables is crimped into the terminal and, with a bit of resistance here, the battery will never be fully charged by the alternator. A quick check is to see if the positive battery terminal gets warm while the engine is running.


Kevin

[Golfbuddy]

hi, bought the car just a few months ago. if i leave it for a couple of days and go and start her shes fine, but if i sit in it with radio on for any amount of time the battery go dead. is to  do with not enough water in the battery for it to hold a sufficent charge or has the alternator gone up the duff.

getting tired of asking for a jump.

I take it you mean that you sit in the car, listening to the radio with the engine switched off? Under these circumstances it would appear that the battery needs changing as it should be man enough to run the radio for several hours without discharging the battery. If this happens with the engine running, then that would point to the alternator as the battery shouldn't have any work to do.

Incidentally, I never get tired of asking for a jump. It's just the constant rejection I get tired of.  

[Kevin Wood]

First you need to establish that the battery is charging. Check the terminals and the charging voltage as TB says. You should see 14 - 14.5 volts across the battery terminals with the engine running (may need to increase revs to 2,000 or so to see the full voltage).

Next, switch some load on (headlights, heated rear screen, etc) and check that the voltage doesn't drop below 13.5 or so.

Now, with the engine off and the battery fully charged (give it an hour on a charger if there's any doubt), watch the battery voltage. You should see about 12.5 volts or more with no load. Switch on the headlights and monitor it for a few minutes. It will drop maybe 0.1 or 0.2 volts but if it steadily declines to 12v or below in the space of a few minutes, and IF the battery started out fully charged, the battery is toast.

Edited to say: i agree that the radio should not drain it. A radio takes maybe 1 amp. 65 amp hour battery will power that for 65 hours in an ideal world. (OK, call it half that if you expect it to subsequently start the car!).

Kevin

[mark.adams]

Incidentally, I never get tired of asking for a jump. It's just the constant rejection I get tired of.  

I work on the principle of 'if you don't ask... you don't get'

[LFF64]

I get tired of asking for a jump too