15.9v - Err, whassup?

[Tintin]

...
My money stays on a defective or disconnected regulator (provided that the Adverc is not connected and battery sensing is not connected, i.e. the alternator is being used in bog standard form, as stated by the OP). Alternatively perhaps the diodes supplying D+ (not the main output diodes).

Just one other thought, is the pulley size right, the alternator isn't running insanely fast is it?

Yes, all bog standard.

On the puley size, this is the same as what was on the Valeo. If anything it is too large as I have to be above 1500rpm to get any good output when first charging (e.g. 50-60amp) and 1500rpm gives a nice 4.5knot cruising speed.

Depends on battery level, but after 90% the voltage to charge the battery rises rapidly to around 16 volt, it's not a bucket that you pour amps into. The output voltage of the alternator regulating at 14.4 volt on your multimeter, on a scope has peak voltage of 16 volts or more with a fully charged battery.

Turning on the fridge drops voltage to normal, so not a lot of load sorts the problem, so first job is find the problem, in this case does the large battery bank size have a effect on output voltage, halving it, does it alter voltage?

Brian

Fridge load is about 10amps

This is looking more like a measurement issue to me. OP, do you have an old-fashioned analogue meter you could try? (of course a 'scope would be ideal).

I am taking the voltages from both the cockpit mounted Garmin GPSMAP750 plotter and also the Victron BMV battery monitor adjacent to the switch panel. The former I would doubt, the latter I am reasonable certain as to its accuracy - do you still think an analogue meter would be worthwhile?

 

[Plevier]

Depends on battery level, but after 90% the voltage to charge the battery rises rapidly to around 16 volt,

### I'm sure that's not what you mean! It will charge to 100% at anything above 13.8V but it will take time. At 16V you'll get a substantial current (but poor charge efficiency with accompanying gassing and heating). I can't put a figure on the current, I can't lay my hands on any curves going to such a high voltage at the moment, but I would expect more than 1%. What does a 10% constant current charger get up to if you leave it on too long, isn't it about 18V? Long time since I've done it!

The output voltage of the alternator regulating at 14.4 volt on your multimeter, on a scope has peak voltage of 16 volts or more with a fully charged battery.

### The normal rule of thumb for a 6 diode alternator with a charged battery is ripple no more than 0.5V rms. Spikes of 1.6V would be bad news.

.

 

[VicMallows]

do you still think an analogue meter would be worthwhile?

Yes. I have come across too many instances of digital meters becoming confused by spiky waveforms (as also alluded to by Halcyon).

Edit: Just for clarity I DO mean a real moving-coil meter ..... not just some modern interpretation that happens to display in a dial format rather than numeric

 

[halcyon]

### The normal rule of thumb for a 6 diode alternator with a charged battery is ripple no more than 0.5V rms. Spikes of 1.6V would be bad news..

And a fully charged battery is 15.5 volt.

Batteries and charging is a funny thing, I used to use a transformer with secondary out of 13.8 volt, for Delco Freedom batteries we charged to 15.6 volt with that transformer. Depending on type of secondary loads ( with and without fridge in this case ) has a big effect on charge voltage that you read on your meter.

Brian

 

[Plevier]

And a fully charged battery is 15.5 volt.

Thats an interesting propodition. I can't think of a battery manufacturer who would agree with that. Certainly doesn't apply to the many millions we produced, whether automotive, stationary or traction, Plante, tubular or pasted, antimony, calcium or pure lead, conventional or AGM! A lot of vehicle electronics would object too.

 

[charles_reed]

Thats an interesting propodition. I can't think of a battery manufacturer who would agree with that. Certainly doesn't apply to the many millions we produced, whether automotive, stationary or traction, Plante, tubular or pasted, antimony, calcium or pure lead, conventional or AGM! A lot of vehicle electronics would object too.

Halcyon remembers right - Delco specified 15.5 - 15.8 volts as the adsorption charge for their Freedom batteries when they introduced them to the market in the late '70s. No one was producing a standard charger that put out that charge. Personally I think it was a ploy to be able to refuse on their 3 year warranty.
Horrid over-priced batteries...

 

[halcyon]

Thats an interesting propodition. I can't think of a battery manufacturer who would agree with that. Certainly doesn't apply to the many millions we produced, whether automotive, stationary or traction, Plante, tubular or pasted, antimony, calcium or pure lead, conventional or AGM! A lot of vehicle electronics would object too.

What voltage do you think a standard flooded lead acid battery takes at full charge then ?

Brian

 

[halcyon]

Halcyon remembers right - Delco specified 15.5 - 15.8 volts as the adsorption charge for their Freedom batteries when they introduced them to the market in the late '70s. No one was producing a standard charger that put out that charge. Personally I think it was a ploy to be able to refuse on their 3 year warranty.
Horrid over-priced batteries...

Sometime worry about those chargers we made back then for Westerly, if an later owner changed to standard flooded batteries, charging to 15.5 floating at 14.4, from memory, want do them a lot of good.

Brian

 

[Plevier]

What voltage do you think a standard flooded lead acid battery takes at full charge then ?

Brian

If you assume a fully charged sg of 1.280 (which is the highest commonly used other than some AGMs that use 1.300) at 25 deg then the minimum voltage to achieve full charge will be 13.9, for s.g 1.260 (common in automotive batteries) 13.8V, for 1.220 s.g. (large stationary batteries) 13.6V. I am not arguing that a bit more is not OK or even desirable - as long as it is reduced when you reach the float situation - but I would certainly consider 15.5 unwise. It will lead to excessive gassing, heating, paste erosion and grid corrosion if sustained.

I wouldn't regard Battery University as the ultimate authority but rather than quote a particular manufacturer, I would regard their page http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery as a reasonable summary.

Yes I forgot about the Freedom battery Charles, I know they called for startling voltages, I don't know why. I don't know a lot about them although my colleagues on our automotive side examined them and weren't impressed (like you!). You say they wanted 15.5-15.8V in the absorption stage; that isn't the stage Brian and I are disagreeing about, we are talking post absorption, where the voltage limit is normally lower.

The other oddball is the Cyclon cell which has special considerations not relevant here.

 

[Plevier]

Sometime worry about those chargers we made back then for Westerly, if an later owner changed to standard flooded batteries, charging to 15.5 floating at 14.4, from memory, want do them a lot of good.

Brian

Well I'd agree with that! How do you square that with your other statements?

At the same time, I'm pretty sure that in practise more batteries are spoiled by undercharging than by overcharging.