Some notes on my bat packs I did at lunch
One set of 24 3.8 AH 1.2V NiMh sub C's is $100
72 cells is $300
2 43 V packs is the same as 13 A123 cells
43V @ 7.6AH = 326 WH
48V @ 7.6AH = 364WH * needs more then 2 packs *
48V @ 11.4AH = 540WH $500 ( 5 packs of 24 cells )
38V @ 11.4 AH = 437 WH $400 ( 4 packs of 24 cells )
Today I got a chain installed and did a few various tests .
Test A was with the bike flipped up side down to measure wheel RPM .
I use a chunk of reflective foil on the bike wheel and a non contact RPM gauge to see real world
RPM values as the sprocket was not the 1:2 I wanted . But more like 1:3.
I ran the bike at 24 , 36 and 48V to get a curve .
At 24V the rim was at 200 RPM.. math says 11 MPH
At 36V the rim was at 316 RPM.. math says 17 MPH
At 48V the rim was at 500 RPM.. math says 25 MPH ( YIKES !)
From this test I can confirm that the V to RPM is not linear.
Test B was a simple test to see how much HP there really is off various voltages .
I applied 24 36 and 48 V each with me then applying some ever increasing break pressure .
The Idea is that My load of me riding is less then the Breaks fully applied .
I found out that at all the above voltages that the motor had no problem overcoming the breaks .
Test C was to see if 24V Was enough to have a decent ride ..
I rigged up the speed con and 2 12V 10AH AGM batts to the bike and headed out of the lab.
I was amazed to see that at 12V UNDER the rated motor spec at 36 V it ( bike ) had enough GO to move me with out it being too sluggish .
I then proceeded to test the same rig at 36 V to get a idea if I would enjoy a higher voltage .
36V had a TON more ” GO “ as expected .
Mind the batts were on the back rack so the balance is way off , but it will with a hard throttle do a “wheele “
I see that 450 W motor was OK for the job so far.
This is good as the cells are not cheap and if 24-36 range is enough power then why use a 48V pack .
Test D was done back at my flat with a meter to see how much current is really drawn off that pack so I can size it better ..
I used my Meter to read the current draws at 24 and 36 V
24V was 28-30 amps peak and 19A average.
36V was 32-40 amps peak and 20A average.
NOTE I have concluded that 48V is not needed so its not going to be in any test from now on .
At this point I am looking at 28V as my standard as its a multiple of 14.4 and 7.2 RC car packs AND its a cross over from Li based batts .
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