Battery or Regulator?

ajstars · 23 April 2013, 15:30

When at fairly high revs my Navman warns of 'over voltage'. We are running a 2 stroke Yamaha 85hp with a Bosch S3 maintenance free battery rated at 53Ah. I have read that the battery may be the problem rather than the regulator rectifier. Any ideas?
Thanks

Nos4r2 · 23 April 2013, 18:11

Unlikely. More likely it's the battery switch or regulator.

I've got exactly the same motor and I had the same prob, turned out it was a dud battery switch.

ajstars · 23 April 2013, 19:16

Everywhere I look it says not to use maintenance free batteries. I assume by the battery switch you mean a cut off switch?

Nos4r2 · 23 April 2013, 21:25

Quote:

Originally Posted by ajstars

Everywhere I look it says not to use maintenance free batteries. I assume by the battery switch you mean a cut off switch?

Yes.

If it has a poor connection your voltage across your electronics will jump up and down.

If your battery is FUBAR then you'll get a low voltage or problems starting. They won't give more than about 13.2v even when fully charged,

jyasaki · 24 April 2013, 17:04

Quote:

Originally Posted by Nos4r2

If your battery is FUBAR then you'll get a low voltage or problems starting. They won't give more than about 13.2v even when fully charged,

While running? My F115, at higher revs shows 14.2 to 14.4 across the battery.

Since the battery switch is only dealing with the +12V, I don't see how this could affect the supply voltage to the GPS in a way that would increase it.

The output from the motor at speed and with no load (which is not a good thing to do, by the way) is likely to be in the 16 to 18V range or higher (talking potential here, as running with no load may damage things.) With a battery as a load, that usually smooths things out to anywhere from 13.5 to 14.6 or so volts. That range should not cause an overvoltage condition on your GPS.

Two things you should do: Put a voltmeter on the alternator output at the motor and see what that reads, and compare it to the voltage across the battery at a similar rpm, which will give you your cabling loss (which I would expect to be not more than a couple/few tenths of a volt, up to maybe a volt or so.) Do the same with the GPS power input. Any large discrepancy means your cabling is dropping voltage somewhere. Might want to check teh grounds by putting one lead of the voltmeter on the neg at the engine and measuring voltage at the battery (-) and the GPS (-) to see if a ground connection is resistive.

If all the (+) voltages are roughly similar (first step above), then you've got a component causing the problem, and need to start isolating that. Swapping in a different battery temporarily is probably a good place to start.

Luck;

jky

Nos4r2 · 24 April 2013, 18:33

Quote:

Originally Posted by jyasaki

While running? My F115, at higher revs shows 14.2 to 14.4 across the battery.

Since the battery switch is only dealing with the +12V, I don't see how this could affect the supply voltage to the GPS in a way that would increase it.

jky

If the switch is intermittent, you'll get voltage spikes as the battery connection drops in/out.

doggypaddle · 24 April 2013, 18:36

Quote:

Originally Posted by jyasaki

While running? My F115, at higher revs shows 14.2 to 14.4 across the battery.

Since the battery switch is only dealing with the +12V, I don't see how this could affect the supply voltage to the GPS in a way that would increase it.

The output from the motor at speed and with no load (which is not a good thing to do, by the way) is likely to be in the 16 to 18V range or higher

turning the battery switch off or a dodgy switch may have the same effect?
if the battery switch had a resistance then there will be a higher voltage across all the circuits than the battery terminals.

ajstars · 24 April 2013, 23:34

The Yamaha manual states battery should be 70-100ah and 252-360kc.
Ours is 41ah and 360cca. What difference does that make?
(Kc and cca are not typos!)

captnjack · 24 April 2013, 23:43

Quote:

Originally Posted by ajstars

The Yamaha manual states battery should be 70-100ah and 252-360kc.
Ours is 41ah and 360cca. What difference does that make?
(Kc and cca are not typos!)

What is a "Kc"? Never heard that term before.

Alot of manufactures spec some pretty big batteries. 100Ah would be larger than the battery in my 381hp pickup truck. My attitude is as long as you have enough cranking power to turn over and reliably start in cold weather any extra is just wasted weight, unless you need it for a bilge pump while not running etc.

kerny · 25 April 2013, 00:18

Quote:

Originally Posted by captnjack

What is a "Kc"? Never heard that term before.

Thats because he missed the f out in the middle

Nos4r2 · 25 April 2013, 03:48

Quote:

Originally Posted by ajstars

The Yamaha manual states battery should be 70-100ah and 252-360kc.
Ours is 41ah and 360cca. What difference does that make?
(Kc and cca are not typos!)

It's not dependant on the battery as long as it's a 12v battery and it's connected correctly.

C-NUMB · 25 April 2013, 10:33

Quote:

Originally Posted by ajstars

The Yamaha manual states battery should be 70-100ah and 252-360kc.
Ours is 41ah and 360cca. What difference does that make?
(Kc and cca are not typos!)

I would borrow a "bigger" battery( 80 ah) and test it out. I have been tould that using a smaller ah battery than recomended might caus an increase in voltage(when battery is fully charged, possible due to smaller resistance). 41ah is pretty small compared to 70-100ah recomendation?

ajstars · 25 April 2013, 10:49

Those are my thoughts too. There are plenty of threads on not using a maintenance free battery on other forums so I am surprised no one has views on that here! Should I be looking at the Leisure type batteries then?

jyasaki · 25 April 2013, 17:14

Quote:

Originally Posted by Nos4r2

If the switch is intermittent, you'll get voltage spikes as the battery connection drops in/out.

But not on the load side. You are, in effect having an intermittent resistor in line with the supply voltage. Any short term spike as the resistance is removed is unlikely to trigger an overvoltage warning on the GPS, as it will be a very short duration event.

jky

captnjack · 25 April 2013, 17:17

Quote:

Originally Posted by jyasaki

But not on the load side. You are, in effect having an intermittent resistor in line with the supply voltage. Any short term spike as the resistance is removed is unlikely to trigger an overvoltage warning on the GPS, as it will be a very short duration event.

jky

Agree. I'd look at the voltage directly across the rectifier before messing with the battery or the switch. If its >16V there's your problem.

Nos4r2 · 25 April 2013, 19:14

Guys, I'm sat here telling you it happened to me with EXACTLY the same motor and the battery switch was the solution. It's not unlikely, it IS what the problem was and it gave exactly the same symptoms.

It's also the cheapest and easiest thing to check-just remove the battery switch so the battery is permanently live and take it for a run.

By the nature of the way Yamaha rectifier/regulators work, they won't overvoltage if the unit fails. They generally just stop charging or drop output right down.

jyasaki · 25 April 2013, 21:53

Quote:

Originally Posted by Nos4r2

It's also the cheapest and easiest thing to check-just remove the battery switch so the battery is permanently live and take it for a run.

Don't even have to do that. Take a single jumper cable and clip one end to the switch pole and the other to the throw, and you've bypassed the switch.

jky

Nos4r2 · 25 April 2013, 21:58

Quote:

Originally Posted by jyasaki

Don't even have to do that. Take a single jumper cable and clip one end to the switch pole and the other to the throw, and you've bypassed the switch.

jky

That'd work, but I wouldn't fancy the consequences if it fell off while trying it out.

ajstars · 25 April 2013, 23:59

I'm still confused - what switch are we talking about here?
My battery is direct to the engine - the only switch I have is for auxiliary equipment.

Nos4r2 · 26 April 2013, 01:22

Quote:

Originally Posted by ajstars

I'm still confused - what switch are we talking about here?
My battery is direct to the engine - the only switch I have is for auxiliary equipment.

Ok, check your battery connections then.It could be a bad contact there. See if the terminals get hot during starting, or they wiggle about.Both the +ve and -ve. Check the connections on the rectifier/regulator unit as well.

If it is a regulator problem, Electrex will be able to supply a new rec/reg unit at a lot less than Yamaha will want for one.
It won't be your battery in any case. The alternator on that motor is old tech and it doesn't have a massive output. Certainly nowhere near enough to overwhelm a battery the size of the one you have.

You could do with an isolator switch on the battery by the way.