Battery voltage too high

[Ali_Colquhoun]

Hi,

When running my boat for a long time at a fair speed I sometimes get a "battery voltage too high" alarm on my plotter, which then shuts itself down.

Now I did ignore this but it finally blew my trusty icom up the other day so I need to do something to prevent this.

My thinking is to put a 12v surge protector on the +ve line into the radio/plotter but I was wondering if anyone had any experience and/or better ideas; and I'm sure you do.

Thanks,

Ali

[Poly]

Have you measured the voltage? The regulator on the battery should be keeping the voltage in the right range. Too high a voltage is bad for the battery too. If the battery terminals are loose it can mean there is nowhere to "put the power" and you can get erratic voltages.

[beamishken]

Assuming the battery is connected to an engine that is charging it then the problem is likely with the engines charging system
Which has already been said will damage the battery in time, you will likely find the battery getting hot check the voltage with the engine running should be around 14v

[Ali_Colquhoun]

Thanks, when static the battery voltage is 14v, I'm sure you are right that too high a voltage is coming back from the engine. I will try to clamp my meter on and look at it when I am running the engine. The battery clamps seem secure.
Perhaps I need a larger battery if it is going into overcharge?

[Chris Caton]

if you connect your multimeter to your battery you should get just over 12v without the engine running, with the engine running it should be around 14v, if you're getting over 14v with the engine running it's the voltage regulator on the engine charging that's causing the problem. it's worth checking you've got the right size battery for the engine, but if its overcharging fitting a bigger battery won't help

[Ali_Colquhoun]

Thank you I will check it.

[Last Tango]

How old is your engine?
Older outboards only had rectifiers and not regulators. They relied on the battery to regulate the voltage which worked ok with "wet" batteries as they simply sat there boiling off fluid that could be topped up from time to time. Doesn't work with gel cell leisure batteries though.

Probably too new to fall into that category so, as has been said, ideally should reach 14.6-14.7V but you won't need max revs to get there. Fast idle to 2000rpm should give you that and within reason the size of the battery shouldn't make any difference either as even small gel cell batteries eg 7Ah still use the same charge voltage. (The charge is voltage, not current regulated.)
A knackered battery can cause problems, if it's an old style wet battery check the fluid level but I'd expect if that was the problem you'd have starting issues.

[Ali_Colquhoun]

It's a late 80s Yamaha 80hp. No starting issues and a relatively new battery. I expect you are right and the engine is sending back too high a voltage when running for a long time. I should be able to check it next week.

[9D280]

I had that with my mid 80s Merc. Killed 2 batteries in blissfully ignorance then got my plotter and programmed it to show battery voltage..... O....M.....G.

Battery toast!

The engine now has a Suzie reg / rectifier as it was one that fitted the ridiculously tight package space in a clamshell....

[9D280]

Phone not playin edit....

Engine was chucking out 14.7v at 1300 rpm! No wonder my battery wasn't lasting!

[Last Tango]

Originally Posted by 9D280

Phone not playin edit....

Engine was chucking out 14.7v at 1300 rpm! No wonder my battery wasn't lasting!

Providing it doesn't go over that as the revs go up, that figure is exactly what it should be.
My home step charger (£175 worth) puts out exactly 14.7 volts on a flat battery.

[9D280]

It did.... linearly