battery problem on forester

[BOB HOLLOWAY [ UK].]

is there any truth in line i am being fed by my dealer that the battery does
not re-charge unless the vehicle is at cruising speed ie town driving is no
good!!!

 

[Orienteer]

Depends how many accessories you're using; the heater fan, radio, heated
seats/windscreen, wipers, lights all take power. If you're not using any of
these, then the alternator will charge the battery even at town speeds.

 

[Ed P]

is there any truth in line i am being fed by my dealer that the battery does
not re-charge unless the vehicle is at cruising speed ie town driving is no
good!!!

Bob,

Certainly the statement that town driving is no good for recharging the
battery is bogus.

Modern cars have alternators that produce substantial output at engine
idle speeds and achieve their rated output and speeds just a little
above idle and certainly by about 1800 RPM or so.

Whether a battery charges or discharges at idle or in low speed driving
depends on whether total electrical load exceeds the alternator's
capacity. High-beam lights, heater/AC high-fan speed, and rear-window
defogger are the main high electrical load items. If most or all such
high-load functions are ON at the same time, the battery may discharge
at idle or in stop-and-go driving. You can probably observe this by
noting whether your head lights dim at idle with the heater and defogger
ON and that the lights brighten as soon as the car begins to move.

The real questions should be what problems are you having with your car
and have they been properly diagnosed? A quality garage should have
the equipment to load test your battery and measure the current the
charging system can deliver to the battery.

Ed P

 

[BOB HOLLOWAY [ UK].]

Ed P
This is what I thought,I remember from way back that the principle advantage
of the altenator over the dynamo, was that the former delivered its max
output at low revs.
The whole story is that we were woken @ 2 am with the car alarm waking the
dead!
The main battery had gone down and the alarm sensed this as a problem and
kicked in, I had only had the vehicle [new] 8weeks and was in a real sweat.
The alarm manual tells you how to over-ride the alarm, what it FAILS to tell
you is that you must enter the over-ride code with all the doors and windows
closed!!
So it was a case of put the earplugs in and wait for the call out guy ,[the
neighbours love me]
NB The BS about the charging was from Subaru UK