Hamid,

Where did this come from?:

<<One little detail that most people are not aware of is that a 35Ah battery is rated to produce that much energy if it is drained over 20 hours.

….If you drain it at 35A, it will not last one full hour, likely somewhere

around 45 minutes or less at room temperature >>

 

For the batteries in question here, the very definition of the nominal battery capacity designation is the number of amps that can be discharged for one hour.  This definition is provided in the battery manufacturer’s literature – see Gill and Concorde websites.  Other manufacturers may use a different definition, in particular for energy batteries (long duration, low current applications).  Gill does provide capacity data for a 20 hour discharge, but the Ah rating claimed is for the 60 minute discharge.  Note that the ‘25’ in Gill ‘G-25’ does not mean 25 Ah, just as the ‘25’ in Concorde’s ‘RG-25XC’ does not mean 25 Ah.  The Gill G-25 is rated at 18 Ah and the Concorde RG-25XC at 24 Ah.

 

Other conditions that apply in order to achieve the battery rated capacity are:

-the battery must be new

-the test must start with a fully charged battery (manufacturer’s procedure must be followed)

-the battery must start at the correct temperature (results are sensitive to this)

 

If you only get 45 minutes at a 1C discharge, the battery would fail Concorde’s criteria for airworthiness and the battery should be rejected.  Concorde uses 80% capacity as their acceptable limit (or 19.2 Ah for the RG25XC).  The manufacturers specify how often to perform a capacity test.  I do one on my RG25XC at every annual inspection (I mean ‘condition inspection’).

 

 

Chris Zavatson

N91CZ

360std

www.N91CZ.com