voltage problem

Portholme · 30 July 2011, 17:22

i'm hoping someone can help me. been on the boat most of the day and most of the day I've had the same problem. both the GPS and fishfinder are flashing up low voltage warnings. they say i have only 10.5 volts.

the boat has started on the button and all the electrics work fine.

with my rudimentary knowledge i'm thinking this is either;

1. something i can ignore
2. an alternator problem
3. a knackered battery.

any of you folks got any insight or thoughts please - gonna be using the boat the whole of the next fortnight.

thanks

doggypaddle · 30 July 2011, 18:00

I dont think ignoring it is a option

You are quite right it could be a knackered battery, though unlikely. (would expect around 12 volts when charging with a cell gone in the battery)
Most likely explanation is either lack of charging, or a high resistance in the wiring that supplies BOTH the items that read the low voltage.
for what its worth here is what i would do.
Firstly find out if the problem is with the supply to the instruments or the battery voltage really is low. do this with a digital voltmeter straight across the battery terminals, and check the difference between that reading and what your instruments tell you. if the battery voltage is normal then the wiring to the instruments is likely at fault.
If the battery voltage really is 10.5v then its likely its not charging.
with the engine running at a few thousand RPM the battery voltage should be between around 13v and 14.8v. if not then its likely its not charging and futher investigation is required.
check the charging connections, fuse if there is one, and check the stator continuity with the ohm setting on your meter.
If all that checks OK its likely the fault lies in the recifier/regulator packs. or the battery has a dead cell. Bench charge the battery for 2 days and leave stand for a day. Terminal voltasge should be well over 12 volts more like 13.2V 11.2 volts ish indicates a failed cell.
if the boat
cranks over fast on the starter and all else seems OK then i would suspect the wiring to the instruments or a dodgy battery first.

hope this helps

Erin · 30 July 2011, 18:46

Sounds very much like a poor connection or corrosion somewhere in the cabling serving your navigation instruments.

Channel Ribs · 31 July 2011, 06:59

Can you measure* the voltage at the battery with the engine off and then with the engine running at fast idle? This will help quite a bit.

If the battery has a good voltage then as suggested, work along the system until you find a drop - it will probably be quite sudden and highlight the problem area.

* If you don't have a multimeter then it is well worth a tenner in your local Maplins.

Cookee · 31 July 2011, 07:43

If it starts fine then the battery is ok - if it's confined to the dash then it's a bad earth or distribution busbar or similar.

Portholme · 31 July 2011, 07:55

Thanks Cookee. I'm in Salcombe and wondering how far i'll have to drive for a Maplins!!!

Looks like I'm off for a potter down Island Street.

Cookee · 31 July 2011, 08:09

Quote:

Originally Posted by Portholme

Thanks Cookee. I'm in Salcombe and wondering how far i'll have to drive for a Maplins!!!

Looks like I'm off for a potter down Island Street.

Where is the boat - 07836268747 and I'll have a quick gander if you like?

boristhebold · 31 July 2011, 08:28

Sounds like a bad battery, I had similar last year and it made my engine splutter and cut out, it was a bad battery, happened as I crossed the ferry crossing point in Poole harbour entrance, luckily I had fitted a second battery when I bought the boat so just switched to second battery.

The voltage on my batteries when underway reading off the yamaha gauges is normally around 13.4 v to 14.1v, so even if it reads 12v you should check it under load. It's also worth changing the battery cables to some decent ones

Portholme · 31 July 2011, 08:33

hi Cookee that's a very kind offer indeed. we are in one of the apartments in The Salcombe. I'm on 07912 731183 . If you don't mind taking a gander I'd really appreciate it. Please feel free to call/text at any time and I'll get it to where ever you are to minimise your inconvenience.

thanks

Richard

Portholme · 31 July 2011, 15:39

Thanks to Cookee for coming to look over the boat, for his advice and for the invite to the new boat launch party!

The saga continued after he left us to it. We went out to sea and the voltage suddenly nose dived to 9.0 volts. The alarm was going like mad so I stopped and cut the engine (habit from when alarms go off rather than engaging the brain). Came to restart and guess what????? Not enough charge to turn the engine over.

We left it 15 minutes whilst another family member came to give us a tow and then it started. Motored back to the beach, stopped the engine and it wouldn't restart.

I started to figure that this was probably an intermittent battery issue with a dodgey cell or alternator so I put a new battery on and all is well - - - - so far!!!!

Got some top tips from Cookee and a big thanks to him for giving me his time on a Sunday morning - top bloke.