Does anyone have any ideas, technical or not, of how many miles running a car has to do to replace the power loss on the battery of a cold start?
Thanks
Edited by Pugugly {P} on 26/01/2008 at 18:27
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This is my arithmetic.
Starting. Say 250 amps for 2 seconds = 500 amp-seconds.
Running. Assume alternator is supplying 5 amps.
Allowing for 80% efficiency it therefore takes 500/5 x 100/80 seconds to replenish the charge. i.e. just over 2 minutes.
Number Cruncher may have a better real-life answer.
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I have a new battery in mine. For the last month or so the average distance travelled per start is around 3 miles, in traffic - 10 minutes?.
Battery gets charged, well trickled from an Optimate every couple of weeks as it seems to become sluggish starting.
Martin
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Some years ago a technician told me that my Mazda6 would need to be driven for about eight miles to fully replenish the battery following a cold start.
Clk Sec
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Thanks for the answers so far everyone.
My parents own an 04 Mazda MX5 1.8. It has recently had a new OE battery fitted (gel type apparently). The car is used for short infrequent runs - this leads to starting difficulties occassionally. My dad has had the car checked for rogue leaks/drains by both the main dealer and an auto electrician and everything is fine apparently...
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This is a recurring problem on bikes which are fitted with immobilisers. The solution is to fit an "Optimate" or similar device, available from Halfords and the like.
If, as I suspect, your Dad just uses the car as a summer toy then all he needs to do is take the battery off and leave it on the bench attached to the device; alternatively he could have a charging socket fitted under the bonnet, all it involves is a lead which is permanently wired in to the battery and you just couple it up when it's on charge.
I'm no sparky so I'll let someone else do the technical bits, bit they do seem to work. You just have to remember to disconnect them before driving away!
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A Halford's advert on TV used to say 15 minutes to put back what was used to start the car.
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Further to my post above. As the annual mileage in my 6 is quite low ( I do drive other vehicles as well), I put my battery on charge for an hour or so every 4/6 weeks.
I?m no mechanic, but would suggest this may resolve the MX5 issue.
Clk Sec
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As the 944 doesn't sit in a garage I use a Maplin £9.99 solar panel. Covers the stereo & alarm drain.
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>>I use a Maplin £9.99 solar panel. Covers the stereo & alarm drain.
I think you mentioned that in a previous thread, and I was going to buy one until I realised my cigarette lighter will not work unless the ignition is switched on.
It may well have saved me the chore of frequent battery charging.
Clk Sec
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What also slowly discharges the battery is the current used by the immobilser etc. Over 24 hours this discharges the battery by more than a single engine start.
Therefore you will need around 15 minutes running to replace both the starting discharge and the loss over 24 hours.
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The other factor with an MX5 is that the battery is located in the boot. The cleanliness and security of the battery leads and their destination terminals under the bonnet is important.
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If it helps, especially for ClkSec, here are my views on the £9.99 Maplin Solar Charger. It was bought for me for Christmas and when I mentioned it on here, a few posters were very sceptical saying it had less charging power than a glow worm needs.
Well, the 306 gets used maybe twice a week for a couple of miles and it's been hurting the battery. But since I installed the charger in the small gap between the tinted glass sunroof and the internal roof cover I've found the car to start instantly when needed and I can feel the battery has some ooomph.
Well worth it in my opinion.
It comes with about 3m of lead and two ways of connecting: the cigar lighter socket and two clips for direct battery connection. It comes with a connecting plug so you can alternate betwen the two ways.
If your socket is off with the ignition turned off, you can connect the clips to the battery permanently, thread the wire back through a hole in the bulkhead and just leave the tiny connector dangling out of site somwhere until needed.
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>>If it helps, especially for ClkSec, here are my views on the £9.99 Maplin Solar >>Charger.
Many thanks Dulwich Estate. I?ll buy one next time I?m in the metropolis.
Clk Sec
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