Awesome build so far..
I think the box now needs some cosmetics to make it
"theme match" the jeep body
(say a safari luggage rack decal
)
And I'm sorry to warm that up but I have to:
It looks like you got (2) 24V 4AH batteries, wired in series, to form (1) 48V 4AH battery pack
...to power a 48V 1,800W motor that draws IIRC ~40A
A 48V 4AH battery pack can supply 4A for (1) hour
...or ~8A for 1/2 hour (~30 min.)
...or ~16A for 1/4 hour (~15 min.)
...or ~32A for ~7.5 min.
…& then, there's probably gonna be some Voltage drop/sag too
That's is a perfectly valid concern.
If you need 40Amps, 4Ah are not going to last very long
whereas that response to it:
Different animal compared to lead.
is a complete and utter BS I'm afraid,
battery capacitance and current demand
as calculated by Kevin above have absolutely ZERO to do with
battery technology.
I know lead acids cut off sooner than Lipos do on the same occasion;
and so does Kevin for sure;
but the controller doesn't know what battery is connected.
and most cut off sooner than a lead acid would anyways in order to keep those safe and rechargeable.
And in fact:
none of that is (or needed to be) part of the simple x/y=z equation from Kevin above
If you flush your loo with 40 gallons per minute and
have a four gallon tank, it doesn't matter if that tank is ceramic or plastic or steel,
it's empty in six seconds.. period!
I think I know what actually happened here,
namely your ride was still far away from full power
(and don't get me wrong, that's perfect!)
If the motor never needed anything like 1800W even under full throttle, then it just wasn't drawing 40'ish amps.. but maybe only half of that.
makes me wonder.. have you set the speed limiter perhaps?
which on those controllers is actually a throttle divider,
(usually throttle signal will be cut in half for mid and in third for slow speed)
since that results in cut in half/third power
(PWM is 50% duty cycle peak power doesn't change.. available power does.. nevermind)
and 16 amps max for ten minutes
and 10 minutes of maybe 4 Amps
results 3.3Ah of capacitance used
in twenty minutes... sounds plausible to me looking at your results ...
I rode it for twenty minutes almost continuously and at full throttle most of the time.
The battery monitor had me at 25% for the last five minutes and the top speed dropped by half in medium range but stayed the same in low range at 5 mph GPS speed.
I forgot to check the top speed in medium before the battery dropped to 25% so the fastest recorded was 7 mph.
with 7mph top speed there isn't much acceleration going on (which causes the highest demand)
and even under full throttle 7mph isn't requiring anything like 900Watts;
maybe in the realms of 350-400 Watts max.
So mid speed setting wasn't even maxed out really.
I think just cruising would take you about 200Watts on your kart
I think you can (on level road) get a cruising runtime of
about'ish 45minutes or so from your 4Ah batteries.
if you can tell me what that mobscooter weighs with you on it..
I can get you a better guesstimation
or you can calculate it yourself
from this
Anyways;
I'd too suggest to stack a pair of backup cells into the trunk
to swap them out in case you need a bit more oomph and thus greatly reduced the mileage (say climbing an inclination)
just in case.
Since after all, at worst that motor will draw almost 40Amps
and even a 4Ah LiPo pack will not be fully drainable
and only provide you with maybe 3.5-3.7AH of useable capacitance.
So at worst that battery is empty within five to six minutes of full power,
if the controller doesn't cut out earlier that is
'sid
