Mandrake wrote:Seems my battery is not being kept as well charged on my daily commute as I expected!
I'm surprised it's not. The alternator should be well up to it... I used to run mine to work and back regularly (6 miles of slow country lanes) and never experienced any issue at all, even in the depths of winter.
I'm surprised too Jim, however my daily routine looks like this:
Start the car at about 6:50am, let it run for a few minutes while I de-ice (if necessary) and get Joshua bundled into his car seat and into the car. I then have to stop the engine so that I can go back and lock the door and start it again, so that's two starts.
I then drive about 20-25 minutes with the headlights on, rear window heater on, and blower fan on full for a while then medium speed, then stop to drop him off with his Gran. I then start the car again 20 minutes later with lights, fan and rear demister and drive about 3 minutes to the train station. Coming home is the reverse. So that's a lot of cranking and driving with heavy loads.
To fully charge a battery it needs to be able to reach 14.4 volts - on my previous Xantia V6 I found if I had the combined load of headlights, rear window demister and full speed blower fan the best the alternator could do was about 13.9 volts, so if you're doing lots of starts per day and driving with heavy electrical loads all the time as I do in the winter, you can easily see how the charge voltage is not sufficient to replace the energy lost in cranking. :/
I haven't checked the voltage under load on this Xantia but I suspect it will be a similar situation - I'll try to check it this weekend.
After a full charge on the battery charger I certainly notice quite an improvement in cranking. I think with winter driving the battery is not being fully replenished by the alternator alone.
Keeping a battery on float is a good idea in your sort of circumstance Simon but it's worth checking it really is correctly floating as an incorrect float can shorten the life of the battery..
When fully charged the float should be just enough to compensate for the natural self-discharge and no more... My charger floats at around 100-150mA into what I know is a battery that's a little past it's best.
This charger does just that - when it reaches 14.4 volts charging "finishes" and it drops to a 100mA float, allowing the battery voltage to fall to about 12.8 volts.