Duncan, Thanks for that. I wasn't planning of course to push my luck for
anything like 5 hrs. It was simply my starting position for working out
whether I could expect it to get across the shortish Dunkerque-Dover
crossing with pump and radio working. Does the 80% figure apply to pure
lead/gas recombinant batteries, which claim all sorts of qualities not
possessed by ordinary lead/acid batteries?
Regards, David----- Original Message -----
<ami@mcfadyean.freeserve.co.uk>
>
> << 3 amps with a topped up 16 amp/hours battery I reckoned
> > this gave us 5 hrs flying >>
>
> David,
> This is a rather an optimistic calculation because:
> 1.Battery capacity is quoted at the 20 amp.hour rate. When discharged at
> higher rates there is progressively less capacity.
> 2.A brand new battery may have the full amp-hour capacity, but it is
normal
> to allow only 80% of this for a battery in good condition. "State of
charge"
> or terminal voltage is no indication of battery capacity.
>
> If you want to be sure about the state of a battery at any one time then
> you'd need an integrating ammeter, which keeps an account of amps-in an
> amps-out, with presettable factors to allow for self discharge etc.
>
> Regards,
> Duncan.
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