14.8v from leisure battery with engine running

[AndyS95]

Hi all

Bit of advice please. I've put a new leisure battery in as the old one had reached the end of the road, also fixed the wiring for the interior spotlights - there must have been a break in the wire or dodgy connection as cutting in a new wire about 4' from the end with new inline fuse holder and terminal connector fixed the problem. I have also wired in directly to the LB a 12v aux socket, 2 x USB, ON/OFF switch and voltmeter into the back as I wasn't confident the original rear cig socket was up to the job. All working nicely - will post pics in pimp my bongo later.

However, I just plugged in the little 12v tire air compressor and it stuttered then stopped working immediately. Front 12v aux now not working nether was stereo, so guessed fuse blown. Empty space in fuse panel which wasn't that surprising when i thought about it as all the electrics run off the LB, so found blown 10amp fuse in one of the inline holders wired to the LB, replaced it, socket and stereo now working. I haven't risked trying the compressor again though..

Anyway, the point to all this waffle is that when i switched on my front mounted voltmeter it was registering 14.8v with engine on (engine was on when i plugged in compressor) and 13.7 when off. Should I be worried that this is a little high and I could end up with blown fuses when running gear off the aux sockets when the engine is running? Or should I replace the 10amp fuse with a 15? Any thoughts and advice very welcome

cheers, Andy

[Bob]

Obviously Geoff is our man here, so this is just my thoughts.

Those voltages don't sound stupid, ideally to check the battery when not charging it should be left for 30 mins/1hour to stabilise, then 12.7v is fully charged.

Higher voltage just after charging is normal.

I wouldn't recomend up grading the 10 amp fuse, it was fitted for a reason.

When you used the compressor did you start it then connect the air line to the tyre?

Connecting the air first, then starting it, will cause a very high current draw.

It might be worth using something like this:

https://www.amazon.co.uk/dp/B01CDUU536/ ... 1819949602

And plugging the compressor direct to the battery.

If Geoff says different go with his advice.

[g8dhe]

14.8 volts is a bit on the high side, but I would check this first with a multi-meter, the socket based meters are notoriously inaccurate, but you don't normally want to exceed 14.4 to 14.6 volts as otherwise battery gassing will occur and over any time it would damage the battery, with the engine at idle speed its normally around 13.8 volts rising to 14.4 when you have some reasonable rev's. If it really is 14.8 volts then the alternator regulator would be my first suspicion.

[AndyS95]

Thanks loads Geoff and Bob, makes perfect sense, I reckon it is likely down to the cheap clock / temp / volt display. I noticed an hour or so later it was reading 12.9 in front and 12,6 in the back. Will check next w/e with multimeter, not going out in to the cold again now - red wine and fire time!

ps

Bob: I think I plugged in compressor, screwed it into the valve then turned it on, i think it was probably a one off glitch, i was actually inflating tyre of our little Mazda 2, did it off the cig lighter in that in the end..

[Bob]

Sounds good.

[Sven]

These tyre inflators quite often run at about 10 amps, so could easily blow your fuse. I’ve blown fuses on my motorbike when using them & now use it through one of these direct from the battery.
https://www.amazon.co.uk/Accessory-Sock ... ocket+croc

[haydn callow]

I have 3 hand held multi meters, not expensive ones but £10 to £20 each, there is a 0.6volt variation between them, this error could be important when checking alternator or battery voltages.