P38 Battery charging improved

brilliant I was going to replace all the cables but this is easier and in many ways better thanks for the info

Check your charging across the battery before and after. See how much difference it makes

at the moment getting 13.5 across battery and 14.6 out of alt can only get better

Very interesting test Javars. Before fitting the new cables, one thing that you could have done is to measure the volt drops between alt body and the neg batt terminal and also the alt power stud and the batt pos terminal. This would have shown which cable was causing the volt drop. My money is on the neg. cable and the volt drops will be at the connections (especially on the chassis fixing point). There was a bulletin for ground shifts back in 96 or 97 that stated the max volt drop on the earth should be 100mV between engine and battery. To my knowledge, the copper will not increase in resistance over time, but the connections will deteriorate over time. The small variation in the alternator output could be caused by the regulator temperature (a lower temp gives a higher voltage output). On final thing, if you have the heated front screen on and switch on the rear screen, headlamps and blowers, then the electrical system will not load balance and the battery will discharge until the front screen times out after 4mins. So bare this in mind if you do a lot of short distances.

interestingly I tested all legs and the one for me that was causing the problem was the connection between the alt and starter (i replaced the starter to battery last year and the neg leads ) so basically it was my own fault also read somewhere that all leads have a 10 yr life not sure how this works as I would have thought environment and usage would have accelerated the process but so far so good

javars said:

As Im sure many have experienced in the last couple of weeks, the battery on my 4.6 has been getting slowly weaker (short journeys, everything on flat out) so Ive been hooking the car up to my oxford maximiser overnight every few days.
So I thought I would do a few checks, voltage across the battery with the engine running at 2000 was 13.4v but the voltage at the alternator was 14v. Switch the lights, fans etc on and it would dip to 12v. so basically there was hardly no charge going back to the battery on my journeys to and from work (4 miles)
So Ive fitted 2 extra leads, one from the alternator straight back to the + terminal on the battery and one from the - terminal to the alternator bracket. On retesting the was 14v across the battery, rising to 14.1v with revs. Switch on all the gizmos and I am still getting 13.5v
Will see how this week pans out and report back. Also made sure all the other earths were good afterwards but that didnt change the results.
Cost £9.48
Steve

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Hi all.
After reading this thread and suffering from the same low charge rate at the battery, i decided i might try this adaption javar has done.
So popped out this morning and did a temp set up using jump leads as a test connected as javar fitted his two additional in the quote above and 14.1 volts at the battery, but after disconnecting the lead from the power out on the alt to the positive side of the battery and leaving the temp earth lead in place i was still getting 14.1v acroos the battery, so nipped across to my local autoshop and bought a pre-made 760mm long earth strap with ends in place for £3.Went home and fitted the lead from the o/s chassis where there is a threaded hole just above the point where the main earths are bolted,to the front -and easiest to get to-nut on the inlet manifold. I now have 14.1 volts across the battery with only one body to engine strap fitted. Total cost= £3, total labour time=15 mins.Hope this may be of help to someone out there.
Ed