Battery Drain??

Twas Fri, 15 Oct 2004 09:57:13 +0200 when "fanie" put finger to keyboard producing:

A battery that has been discharged to completely flat may have problems holding a charge afterwards (and for the rest of it's life).

As for tracing a drain, that can be a pain in the wossit.

You could try connecting a multimeter to measure the furrent drain and remove and repleace the fuses one by one, that may help. If nothing there do the same with relays, one may be stuck on.

Regards. Mark.(AKA, Mr.Nice.)

On or around Fri, 15 Oct 2004 09:57:13 +0200, "fanie" enlightened us thusly:

what do you get on the battery, when it's running? You should get something around 14.5V with the engine at 1500 rpm or more and no headlights.

if not, it's not charging properly.

try disconnecting the battery, see if it still goes flat. if it does, it's buggered (get it swapped under guarantee, making no mention of having flattened it just in case) and if not, then yes, you've a leak somewhere.

tracing leaks is a matter of faffing around - disconnect the battery, insert ammeter, note current drain if any. have assistant watch ammeter, pull fuses one by one and see if the drain stops at any point... that isolates the problem circuit if you're lucky, then you have to find out what on that circuit is leaking.

6.5V on the negative terminal with respect to chassis would indicate a high resistance earth connection. Check all the earth straps and cables.

Also it may take more than 24hrs for the charge rate to drop below 1A depending on what the max charge rate has been.

Regards Jeff

A slow charge, checked with a battery hydrometer, would be worthwhile. But it takes time. It's worth checking with an hydrometer at this time of year, before a dodgy cell and cold weather combine to give trouble.

I guess that the rules for a series 3 are different once again.

I have done worse than leave the lights on, I have left the heater fan on, and returned to a flat battery, but never so flat as the engine has not come to life on a mere grunt from the starter and the battery recharged after that.

As I said in another post I managed to start the engine from a measured voltage of only 9.5 volts which impressed me.

There is always a problem with undercharging the battery on short runs in the rain and the dark in that the alternator will not do anything at idling speed and there is consequently a net drain on the battery.

Anyway despite that abuse my battery is not ready for the knackers yard just yet.

On or around Sat, 16 Oct 2004 01:05:13 +0100, "Larry" enlightened us thusly:

if the battery was seriously flat the starter would do nothing. There is the point that an alternator won't necessarily charge a totally flat battery, whereas a dynamo will, but yours is probably an alternator. 9.5V however, if the battery is otherwise OK, is not flat, just very low, and if it'll still crank (2¼ petrols crank very easily) then it'll start and recharge.

If you've got it to the point where nothing works at all, then it's a different story.

A friend of mine had a range rover which kept suffering a flat battery and when we connected a current meter in series with the battery something was drawing just over an amp. After some investigation and allot of faffing about it turned out that the vehicle had been fitted with a tracker. The tracker had got its own small 12 volt 1.8 amp back up battery so that if the vehicle had been stolen and the main vehicle battery had been disconnected the tracker would of still activated and sent out its homing signal. Unfortunately the back up battery had deteriorated over the years and went I connected a volt meter across the terminals it was only reading 6 volts indicating that three of the cells had failed and it was constantly drawing current from the main battery and causing it to go flat. I replaced the back up battery with a new one and it totally cured the problem. Has your vehicle got some sort of tracking devise or security alarm installed which has got its own internal battery which may be causing a problem? Just a thought but its worth bearing in mind.

I meant to say in my last post, be careful if you try pulling fuses that your radio is not security coded or you may end up with a non working radio.