battery maintenance

[Stu Jackson]

Don, my reply #4 link's Reply #16

has a suggestion for running the fridge.

"To come at the cycling problem caused by leaving the refrigerator on 24/7 from another angle.

"I have just installed a separate 10 AMP charger and small battery (refrigerator manual says there must be a battery in the refrigerator power circuit) to power the refrigerator when at the dock.

"Which battery is used for the refrigerator is controlled by a relay which in turn is controlled by the main DC switch – main DC switch is ON, the refrigerator is powered by the main batteries, main DC switch is OFF, the refrigerator is powered for the separate battery / charger."

 

[Don S/V ILLusion]

relay specs

sounds like a good alternative - missed it previously.
I assume the relay, when powered, is on the bank circuit and denergized to the separate refrig battery and supply?

 

[GuyT]

Capacitance..

If your power source/charger has sufficient capacitance at the output, it will work with the fridge.
If the motor is a brushless DC type, it creates back EMF that will produce a voltage rise if the capacitance is low - tends to go VERRRRY high if there is no output capacitor.
Most battery chargers (to save cost) eliminate this output capacitor since the battery produces around 1 Farad per 100 amp hour.

Do not give up on the idea of running the fridge without a battery!
It can absolutely be done with an appropriately sized capacitor and discharge resistance(pre-load).

Main Sail - do you have wet or agm batts? I may come up with something literature wise for you.

 

[Stu Jackson]

The Adler Barbour literature goes on some more

about the "dangers" of connecting directly, for various reasons. Don't feel like retyping another paragraph since Adobe doesn't let ya cut & paste anymore! Drats!

Read your manual, and make up your own minds: your boat, your choice!

 

[Maine Sail]

Guy..

Quote: "Main Sail - do you have wet or agm batts? I may come up with something literature wise for you."


Wet cells. Thanks Guy, I'd really like to feel comfortable leaving them in float mode!

 

[GuyT]

Since wet battery technology is so old,

application literature is hard to find.
Here is a link to discussion of AGM batteries and temperature compensation from a battery Mfg.
They clearly talk about grid growth being the life limitation when overcharged due to lack of temperature compensation. The grid growth does not matter what chemistry you have.
Over the years I have accumulated a vast library of AGM literature but none for flooded batteries. Flooded batteries have received no development and therefore no application literature from the manufacturers.
Maybe an old book from the 60's or 70's may be the best place to look.

Happy Reading!

 

[Stu Jackson]

Chargers - might be interested in this

C34 link.

 

[Buck2796]

Guy, Interesting ...

Per your "related link" ...

"Float charge voltage :
The selection and maintenance of a specific float charge voltage is essential to achieving the designed service life and rated capacity of the battery. If the float charge voltage is too high, more float charge current will flow through the battery causing accelerated grid growth (corrosion), hence shortening the battery service life. If the float charge voltage is too low, the battery will not be maintained in a full charge state.This will cause the accumulation of the lead sulfate, resulting in degradation of capacity, followed by a reduction in service life. Battery temperatures play an important role in the selection of the float charge voltage used in any stationary application. The PRC Series batteries are designed for 10 years full float charge operation @ 77°F and 2.25 - 2.27 V.P.C. When the application's environments is such that the battery's temperature varies from the 77°F standard, changes occur in the float charge voltage requirements. These changes are due to variations in the battery self-discharge rate, internal resistance, current acceptance and electrolyte viscosity. It is therefore recommended that the float charge voltage be temperature compensated to accommodate the variations. "


This would seem to be another argument for running your boat's A/C system during the Summer to help keep battery temps down.

Thanks for the link !

 

[GuyT]

Temperature compensation..

Make sure your temperature compensation is done at the battery terminal.
Chargers that have temperature compensation without the temperature probe connected to the battery can do more harm than good in environments with wide daily temperature fluxuations.

Batteries have a large physical mass - they do not change temperature as rapidly as the environment they are in.

Lets say that the batteries temperature is 70 degrees (measured at the post)and the day gets overcast and cold.
A temperature compensated charger will raise the voltage when it gets cold. If the battery is not as cold as the ambient, now an overcharge condition exists.

Many chargers that have temperature compensation use the battery terminal as their temperature feedback. So, if you are going to buy a charger that has temperature compensation, you should go with this type.

If you are one of the people that got one of these probes and did not connect it to the battery and just left it hanging - connect it up! It will make your batteries happier.