On 18 May 2005 18:40:28 -0700, wrote:

There has been alot of discussion about this on the Cardinal owners
site lately. It appears that the RG batteries are good only if you fly
alot, flight schools are good places for them. If flown infrequently
(less than once a week)then old style wet cells last longer.

Have more experience with Concorde RG's than I really want to think
about, in both piston and turbine apps.

Initially, they were an extremely cost-effective alternative to ni-cad
main batteries for turbine engine starts. Use 'em for a year and throw
them away. The cost has steadily increased over the years almost to
the point of being prohibitive in turbine apps.

If they are used infrequently, they can lose capacity in less than
12-18 months. If they are allowed to sit on the shelf without periodic
boost charging they will tend to have lower capacity/service life
after they are installed. It is important to note the manufacturing
date and shelf service label before installing them.

High utilization (engine start cycles more than operating hours) can
cause them to lose capacity in less than 12-14 months.

Leaving the master switch on and allowing them to fully discharge can
cause them to lose capacity at any point during their service life.

The real killer is excessive charging voltage. The Concorde
recommendations for charging voltage vs. battery operating temperature
can help extend service life. In some cases, due to AMM requirements
this is not an option.

The basic concept of the RG battery is that the battery is filled with
electrolyte, allowed to sit, and the electrolyte drained. The
electrolyte that has soaked into the inner workings is sufficient to
keep things working BUT excessive charging voltage will literally dry
out the plates. Once the electrolyte supply within the battery is
reduced, capacity is reduced.

It is a vicious circle- as the electrolyte supply is gradually
reduced, the operating temp within the battery increases-increasing
the rate the electrolyte is depleted.

A valve allows the pressure produced from "over" charging to escape,
but chemically treated pad renders the escaping gas free from
corrosive elements.

Please don't ask what happens if you get a RG battery that they forgot
to drain the electrolyte out of...my policy (now) is to weigh an RG
battery before I install it.

Back to the original poster, I really don't consider Concorde asking
to see a copy of the original maintenance record entry as verification
of install date excessively invasive.