Adverc oddity

[sailinglegend420]

... Hitachi regulator's temperature compensation is primarily to protect against over-heating of the alternator.

Not wishing to fall out on this one but do consider the facts.

If the temperature compensation was purely to protect the alternator then a very crude temperature cut-out could be used. The Hitachi internal temp compensator is very crude BUT it does have some intelligence and is designed to reduce the output voltage at the rate 0.03v per degC rise in temperature above 25C. So at 40 C it will reduce the voltage by 15 x 0.03v = 0.45v. So the battery voltage will come down from 14.4v to 13.95v. This rate of fall is exactly the compensation needed to stop the battery gassing. At 40C a battery gases at 13.98v.

So if the temperature compensation was ONLY to protect the alternator why have such a precise temperature gradient. This kind of works in a car where the battery is near the alternator, but on a boat the battery should never be anywhere near the alternator so is never at the same voltage. This is why an external regulator with a battery temperature sensor actually on the battery will always charge at the correct voltage and therefore make charging faster and more efficient.

EDIT

40C is not very hot. My Balmar is designed to cut the output by 50% when it gets to 105C!

 

[pvb]

Not wishing to fall out on this one but do consider the facts.

If the temperature compensation was purely to protect the alternator then a very crude temperature cut-out could be used. The Hitachi internal temp compensator is very crude BUT it does have some intelligence and is designed to reduce the output voltage at the rate 0.03v per degC rise in temperature above 25C. So at 40 C it will reduce the voltage by 15 x 0.03v = 0.45v. So the battery voltage will come down from 14.4v to 13.95v. This rate of fall is exactly the compensation needed to stop the battery gassing. At 40C a battery gases at 13.98v.

So if the temperature compensation was ONLY to protect the alternator why have such a precise temperature gradient. This kind of works in a car where the battery is near the alternator, but on a boat the battery should never be anywhere near the alternator so is never at the same voltage. This is why an external regulator with a battery temperature sensor actually on the battery will always charge at the correct voltage and therefore make charging faster and more efficient.

EDIT

40C is not very hot. My Balmar is designed to cut the output by 50% when it gets to 105C!

Well, to start with, Yanmar describe it as "over-heating" compensation, rather than anything to do with battery gassing. You mention the car scenario, and the Hitachi is an automotive alternator, which is why it's designed that way.

Next, you seem to misunderstand the temperature compensation. It's only 0.01v per degC rise, not 0.03v, and it starts at 20C, not 25C. That means that in your theoretical case, the voltage will reduce from 14.5v (the rated voltage at 20C) to 14.3v at 40C - rather more than the 13.95v you claimed.

 

[sailinglegend420]

.....you seem to misunderstand the temperature compensation. It's only 0.01v per degC rise, not 0.03v, ......

OK I accept your figures, I had misread the poor online photocopy.....

But let's take your figures and apply to the real world situation of an engine alternator getting to at least 70C on an overworked automotive alternator trying to charge a depleted house bank. That's 50 X 0.01v = 0.5v drop, so the regulator will cut the output volts to 14 volts. The batteries will take a long time to charge at this voltage if they are not in the engine compartment and are still at 20C, so don't need their charging voltage reduced.

70C is a conservative value, my 'hot rated' Balmar regularly gets to 95C - it is designed to cut the output in half at 105C. I think Sterling cuts out at 95C. Many internal regulators have a simple cut-out at the same kind of value, in many cases much higher. This is designed to protect the alternator. The more modern ones have compensation based on a sliding scale of around 0.01v/C which will protect the batteries from gassing - but will of course protect the alternator as well. They may describe it as "over-heating compensation type" because nobody will understand 'battery gassing temperature compensation'.

 

[Sans Bateau]

I was just about to start a post when I read this one, same subject, similar scenario.

My Advec has been fitted to the boat for many years, always worked fine. Last season after a long period under motor the gas alarm went off. As the gas was turned off, I panic'd a little before I realised it was battery gas I could smell, I looked at the charge voltage and it was up at around 16V (maybe more, cant remember exactly). The batteries were not hot at all and unplugging the Advec, the voltage soon dropped to a sensible level. So guys, what wrong?

 

[JumbleDuck]

I have a VSR between the engine battery and the house bank. If that failed to operate for any reason then I'd be sensing a battery to which the alternator was not connected, so I have chosen to sense the engine battery.

I've just found this in the Adverc instructions ... I knew I'd seen it somewhere:

When split-charging using a relay, connect ADVERC BLUE to the alternator B+ terminal and ADVERC RED to the engine (their emphasis - JD) battery +ve post, as a precautionary measure.

Sensing a battery which may not be connected to the alternator is probably not a good idea. They do say to sense the domestic bank when using a diode splitter, though.