Danfoss Designed Control Modules for BD35 and BD50 compressors.

[hzcruiser]

Originally Posted by Richard Kollmann

[...] If charger design allows voltage to increase to the next control point around 13.8 volts more current is produced than needed by refrigeration. If refrigerator operates on a 30% to 50% duty cycle with excess current pumped in to battery its service life is shortened.
[...]

Got it, thanks. So the charger constantly overcharging the batts was the problem there. As mentioned, that shouldn't happen anymore.

If someone still has one of those older chargers then yes, it would make sense to hook it up to a separate batt, maybe an open lead acid so you can top up the water every 3 months or so.
And if I were on the boat several times a week I would leave the fridge on, too. Most people here only see their boat on the weekend, if that.

[Richard Kollmann]

Originally Posted by hzcruiser

Got it, thanks. So the charger constantly overcharging the batts was the problem there. As mentioned, that shouldn't happen anymore.

If someone still has one of those older chargers then yes, it would make sense to hook it up to a separate batt, maybe an open lead acid so you can top up the water every 3 months or so.
And if I were on the boat several times a week I would leave the fridge on, too. Most people here only see their boat on the weekend, if that.

It is not a question of old versus new battery chargers. If the test showed liquid loss in battery cells because of refrigeration running battery boiling stress is occurring.

[john61ct]

FLA boiling for part of the charge cycle is normal and healthy.

If continued for a very long time, make sure to keep water topped up, but not otherwise causing significant harm to quality batts in good condition.

But yes, the overcharging should be corrected, by getting better charge sources, regardless of any IMO separate issues wrt load consumer devices.

And of course the load issues should be addressed as well, for their own sake, even if the charging issue has been solved.

[a64pilot]

Originally Posted by Richard Kollmann

It is not a question of old versus new battery chargers. If the test showed liquid loss in battery cells because of refrigeration running battery boiling stress is occurring.

It’s not, perhaps it should be said it’s a difference between a quality battery charger and perhaps an automotive type?
A good battery charger will stay in float, even with huge short time loads, I can crank my engine and that doesn’t trip my chargers to go to absorption for instance, and the engine start load is pretty big.

I am sure some chargers will, because your telling me they will and I believe you, but not all will and it ought to be an easy check to find out if yours does, just watch voltage when you turn the fridge on, or maybe a spotlight etc.

[john61ct]

Also I would think not hard to keep the bank isolated from the charger circuit until the bank drops below X% SoC.

But better to just get a good charger with full programmable setpoints.

[RaymondR]

Years ago I was in a marina and my expensive battery charger exited this world with a fair bit of splooshing and ozone smell. It was still in warranty however I was away from my home port and cruising so did not want to get involved in shipping things back and forth. I called the dealer and explained the circumstances and he agreed that I hold the failed unit until I returned to the home port and then bring it in for exchange. As a stop gap measure I went to a local electronics dealer and bought a transformer and a couple of diode bridge units and wired them up to put dirty DC on the solar panel input to the solar regulators bus. It worked fine until I was able to replace the busted battery charger from the dealer.

On a number of occasions I have considered the notion of revamping my DC charging systems so that it has a 12 volt system for general house and nav use and a separate 24 volt system dedicated to just the refrigerator.

Your statement re having a separate battery system for the fridge has got me pondering on my upcoming refrigerator upgrade and I am inclined to implement it with the two systems and use the dirty DC to the solar bus bars for shore power charging rather than purchase another expensive, high quality 24 volt charger.