Alternator Charging Rate

Hi All, Just a quick question. About three months ago, I had some problems with different error codes appearing. I cleared the codes and then another one would appear a few days later. I was told it could be a battery problem and because I kept getting a build up of corrosion very quickly around the battery terminal I replaced the battery. Since until about a week ago all was fine, but I started getting little misfires now and again and also the temperature gauge shot up to maximum which was another thing it used to do. I checked the battery and there was acid around the battery box and the green magic eye was missing. The one thing that I didn't do was to take out the the vent plugs at each end, so I was assuming the the gasses pushed out the magic eye. Before that I was wondering if it may have been overcharging. I checked the Haynes manual and it said it should be charging between 13 and 14 volts. When I checked it and revved it though all ranges it was showing 14.37 to 14.39 volts. When I have check other sites it said that was normal, but was wondering if the C3 was different and should be lower. Please could some one tell me if the readings that i got are OK.
Thanks Jeff

Hello Outbound1

A battery charging voltage of around 14.5 volts seems reasonable to me.

At the same time, the symptoms you describe at your battery suggest that it is being cooked, especially the part about blowing out the charge indicator!

How or rather when did you measure the battery voltage? I'm thinking this may be an intermittent fault while your driving which would only show up if you monitor the battery voltage continuously.

Hi Missing Lincs,
Since the new battery I haven't had any corrosion build up around the terminals and as I mentioned no problems until now. Since clearing up the acid and topping up what was spilt it has been fine, I have temporally covered the hole and the acid is not leaking. I was hoping that it might be due to me not taking out the two vent plugs used for transit, so of course there was nowhere for the gases to escape. I only tested the alternator by measuring the output on the battery terminals and took it through various rev ranges. It only went between 14.37 and 14.39.
Thank you for you reply

Missing Lincs wrote:A battery charging voltage of around 14.5 volts seems reasonable to me.

The first reading was taken at idle on a 1.4 petrol and the second with some revs.
The car had just come back from a run, so it had warmed up and made up for the cold start.
A better test would be to load up the alternator with lights on (all of them), the rear heater on and anything else that can draw a decent current. This will stress the alternator regulator circuit but the charge voltage should stay steady.

I'm thinking this may be an intermittent fault while your driving which would only show up if you monitor the battery voltage continuously.

You can fit one of these meters (from ebay) in the cigarette lighter socket and get a reading over time and a number of different conditions.

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Outbound1 wrote:so of course there was nowhere for the gases to escape.

The gasses are not supposed to escape on the modern - sealed for life batteries. The acids are recycled and stay within the battery. This means they never need topping up because they never loose any liquid.

Thanks everyone for your replies, I have just bought the plug in gauge, at least now I can see if there are any spike whilst normal driving. I did do a test yesterday with all the equipment on and the meter did stay steady. Thanks again