On Fri, 15 Sep 2017 23:08:42 +0100, (Roger Hayter)
wrote:

T i m wrote:

On Fri, 15 Sep 2017 13:04:46 +0100, (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??

Ok, well all I'm interested in is how it would work up to 30A when
spread across the 3 batteries in parallel Roger. ;-)

So, sorry, I think I must have missed the conclusion. ;-(


50% discharge voltage /= 12.12 - (discharge current [while stable for
a few sec] X 0.00133)

Ok, they look like numbers O could see in an Arduino sketch. ;-)

VSMOP if you can measure current and voltage continuously.

I can (TAIAP), several times a second. But we aren't measuring Ah are
we, we are (only needing to) measure the instantaneous voltage and
compare that with the instantaneous current and from those two
calculate the instantaneous low voltage thresholds (rinse / repeat)?

eg, It will (very predictably) cope with the (example) scenario of me
going continuously at speed one (5A) for three hours before the alarm
sounds. It will also / equally easily cope with me going along at
speed 3 for 50 minutes (15A) or speed 5 for 20 minutes (30A).

So stage one is using the (non linear) runtime / 'voltage that equals
50% DOD' divisor (that operates increasingly as the current goes up
ITRW) as a constant over the entire battery use. Stage two is to
dynamically calculate that LVD voltage as a function of voltage
current and do so once every second. Stage 3 might be to store and
hold and average those values over say 60 seconds to protect against a
few second burst of speed 5 tripping the alarm whilst generally going
at speed 3.

The most difficult bit will be finding out what is a useful value of 'a
few sec'.

See above? shrug

Cheers, T i m