General converter information

[scrubjaysnest]

This is more of a why I don't like what comes with new or used TM's or other RV's.

The three charging stages or four if you want to count equalization a stage.

Bulk, some times called boost. This puts back about 80% of your charge
current is held constant typically for a deep cycle this max is C/20 times 5.
C=aH rating of the battery. Example 100/20 =5x5= 25 amps max.
Ideal charger will push as many amps as the battery will take, not
exceeding C/20 times 5. This goes on until the battery voltage
raises to 14.7 volts(varies a little between manufacturers).

Absorption, This will try to get the last 20%, voltage is held constant.
The current will decrease until about 1% of C/20. Again varies
between manufacturers.
This is my biggest complaint area, most batteries require absorption voltages at 14.8 or above. The converters currently used by the RV industry don't go above 14.4 volts. Note: AGM and Gel batteries use lower voltages then the flooded lead acid batteries most common in RV's.

Ok enough rant.

Float is a maintenance level that should not boil the batteries.
The ideal charger will drop its output to 13.2 to 13.4 volts and
between 1 and 2 amps. Again varies a little between manufacturers.

Equalization, output is raised to 14.8 volts or higher, some batteries require
as high as 15.5 volts. This is a timed function usually 1 to 2
hours. Again varies between manufacturers. AGM's and Gels
don't need this. What your doing here is stirring the fluid to
get rid of stratification and knock sulfation off the plates.


In the ideal world the user should be able to adjust the charger(converter) to match what the battery manufacture requires for their batteries.
Additionally the charger(converter) should have temperature compensation and remote sense. The only one that comes closest that I have seen to date is Xantrex. Their charging curve is wrong, they hold bulk voltage at 14.7. But they do have temperature compensation.

A quality solar charger comes the closest to ideal but you can't run a converter or charger through them.


AGM's can take a higher bulk charge current and absorption is usually kept
to 14.4 volts.

Gels, lower bulk charge current then either flooded or AGM and lower
absorption voltage.

Since gels and AGM are higher dollar then flooded you really need to look closely at
what the manufacture has to say.


A good source of information is batteryfaq.org.

Maybe this will help members understand better "why my isn't holding charge" or "why batteries don't seem to last very long"

What you can do. Get a good battery, so called smart, charger and monitor the current and voltage during the charge cycle. A bit expensive but less then a new battery every couple of years.
Second thing, add 100 watts solar(minimum) per 100aH of battery with a quality charge controller. This is expensive and buying batteries every couple of years may fit you wallet better. Trojan T 105's are about $150 each now and it takes two for 12 volts.

New batteries before using them charge them fully and let them rest not connected for about 6 hours. Measure the voltage and specific gravity(sg).
SG is measured for each cell. Record the SG you got, the voltage you measured and case temperature to correct the SG reading. This probably needs done once a year or if you think there is a problem. Die hard battery people will say quarterly on monthly.



@ Bill please put in your two cents worth on anything I missed