On Fri, 15 Sep 2017 13:21:32 +0100, (Roger Hayter)
wrote:

Roger Hayter wrote:



None of the information you have helps with saying whether this relation
will still be valid above 93A, but perhaps it should be good up to the
rated maximum current of the batteries??

Caveat is that battery voltage drops at high current due to reversible
changes, so using an underlying open circuit fixed voltage for detecting
a given discharge point is too conservative.

Agreed, and should only be done after resting the battery for 24 hours
or so (I read somewhere).

But, as I say, the makers
use a linear relation up to 93A so perhaps it is not outrageously wrong.

But how does that fit with what they say here?

http://www.mkbattery.com/images/8GU1H.pdf

Or are you also taking that into consideration?

Capacity at C/100 = 36 Ah
Capacity at C/20 = 31.6 Ah
Capacity at C/5 = 26.8 Ah

They are saying that between that range of currents there is a 10Ah
capacity difference, that's over 30% of it's average capacity?
Realistically I would only be interested to see how much the capacity
changed between say 10 and 30A. *If* the capacity doesn't change much
between those particular values then it may not be worth including.
*If*. ;-)

In any case, unless they tell you how you can't allow for this
accurately.

Ok, but if I understand the above info correctly the difference in
capacity changes significantly within the range of currents I intend
to use therefore (in my mind anyway) making it worth of inclusion in
any gauge trying to display the cutoff voltage for a given depth of
discharge? As you say, we need the 'how' and I was hoping we might be
able to extrapolate that from the information we *have* been given?

Thanks very much for your feedback on this Roger. ;-)

Cheers, T i m