Shore power & temp control?

[billknny]

Originally Posted by 4kMike

Thank you fellows!

My point was the battery temperature sensor and the temperature knee point on 25 degrees. Doesn't that mean that I never get the full charging voltage (and because of that full amperes) when in tropics? My primary charging is solar, and secondary main engine, but it would be nice to get that 20-25 amps when running genset too. Of course without boiling batteries.. ;-)

No, not quite right.

What you are not understanding is that at elevated temperatures a battery IS fully charged at lower voltages, it is a property of the chemistry going on inside. It in not correct to think that your batteries are not being fully charged because the voltage is lower at higher temperatures.

There is nothing magic about 25C, it is just one point on a line. "Full charging voltage" is HIGHER below 25C, and lower above it. But that is true of every temperature!

[RaymondR]

I'm a bit baffled, why would one measure battery temperature by having the sensor clamped to the cables?

[slug]

Originally Posted by 4kMike

Hi all!
We are now sailing in Caribbean. When running genset and charging batteries w. Shorepower charger, we don't get more than 14 A to the batteries.
I just found on manual that our Ctec 300 (max 25 amp) charger has battery temperatude control cutting current down when over 25 deg C!
Any suggestions, fellows..? Should I disable (cut off..?) the temperature sensor.. or put it to the ice box..??? :-)

Yes

25 amp is too small, that’s a charger for s small daysailer

You must double your capacity

[4kMike]

Ok... thank you again...but I'm possibly still missing something: When batteries are (by battery monitor and voltage), quite low .. around 50% charge.. they take full 45 amps with engine alternator. But not full 25A with ctec charger. Only half of that... I understand that the alternator is "stupid" and cuts charging always in the same V level.... but still, is Ctec too clever? For these climates (all th rime >27C ), I mean.. Although this climate suits for me better, ;-)

[4kMike]

Hi! Sensor is fixed on the top of one battery, of course. And as I wrote earlier, solar and main engine are the primary chargers.... we have not been connected to shore for months, but running genset now and then. So Ctec is OK, but I would like it to do what is promised on specs.

[slug]

Originally Posted by 4kMike

Hi! Sensor is fixed on the top of one battery, of course. And as I wrote earlier, solar and main engine are the primary chargers.... we have not been connected to shore for months, but running genset now and then. So Ctec is OK, but I would like it to do what is promised on specs.

You might contact ctec and ask if you can modify the charge profile
Some chargers are user programable

[smac999]

Originally Posted by 4kMike

Ok... thank you again...but I'm possibly still missing something: When batteries are (by battery monitor and voltage), quite low .. around 50% charge.. they take full 45 amps with engine alternator. But not full 25A with ctec charger. Only half of that... I understand that the alternator is "stupid" and cuts charging always in the same V level.... but still, is Ctec too clever? For these climates (all th rime >27C ), I mean.. Although this climate suits for me better, ;-)

Turn all your loads off. Turn the battery switch off. Now check how many Amps are going in. Or better yet clamp the charger wire with a meter.

I bet the charger is putting out 25a. But the boat is consuming half of it. Leaving only half to charge the battery.

The alt is probably putting out ~ 60a. And 45 is going to batt. Same thing.

[GordMay]

Originally Posted by billknny

... A battery charger's temperature compensation should work not by altering the charge current, but rather the voltage, typically lowering it by about 24 millivolts per degree C above 25C, although the exact number should be specified by the battery manufacturer...

Indeed.
The ideal storage and charging temperature range for a lead acid battery is 70˚-77˚F.
By adjusting lead-acid battery charge voltages for temperature, the battery can be properly charged in warm and cold weather.
Different battery manufactures recommend different temperature compensation values.
Rolls & Concorde recommend -4mV/°C/cell (24mV per °C for 12V batt)
Deka & Crown battery recommend -3mV/°C/cell (18 mV per °C for 12V batt)