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Re : High Charging Voltage Problem

RE : Alternator Problem or Battery Problem ?
Following up my original query on 27th January - I have now had an opportunity to carry out tests etc. suggested by Mark Langley and Rupert Smedley.
Battery voltage decay over four days : Start 12.58 to 12.58 (= 0), Domestic #1 12.56 to 12.56 (= 0), Domestic #2 12.56 to 12.55 (= 0.01, are meters that precise ?)
On charge individually from the alternator :
Start 15.08v, Domestic #1 15.14v, Domestic #2 15.18v : ambient temperature just above freezing.
The two domestic batteries together, start battery disconnected, 14.83v : all three batteries on charge together 14.81v.
The batteries are bog-standard lead-acid, bought from a reputable chandlery - the two domestics are "leisure". No particular cell is using more water than the others.
I think the batteries have had a gentle life : we do perhaps ten weeks' cruising a year, + odd weekends and odd days. When at base, (until this problem started ) they have been on 'float charge' as advocated in WW by Graham Booth some years ago.
There is absolutely no "glow" at all in the warning lamp when charging : the alternator was load-tested by Carwoods (Coventry), who replaced the regulator, before being returned, with the following results :
Off-load 14.5v, 21a. On load 14.3v, 41a. At increased load 14.1v, 55a. - all at 3329 alternator rpm., which would be fast cruising for the boat.
I have not checked so far the voltage between the warning lamp terminal and battery positive - this will require dismantling of shelves at the back of the boat, and time has not allowed.
Richard Smith

Asked by: Richard Smith  | 12.07pm, Sunday 5 February

WW says:

The batteries do not appear to be self dicharging and the voltages appear OK, so I think they are not the cause.
Was the battery charger disconnected when the voltages were measured?
What engine do you have?
This is obviously not a simple problem, and it might take a while to hit the problem.
Could you contact me directly via rupert.smedley@waterwaysworld.com

Rupert Smedley  | 2.18PM, Monday 6 February

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