Electric motor - what voltage?

Brushless motors can tolerate a wide voltage range, more volts than we can afford. The limits of concern for the motor is heat. You would do well to add a temp sensor to the stator (they are tiny). This way you can explore the limits. At the very least, you will learn the temperature where your type of motor dies.

If the motor is always cold, it's probably larger, heavier, and more expensive than your loads need. 190F is too hot, and temporary peaks of 140F is a useful goal. If you frequently hit 160F, you might consider selling the motor while it still runs, and getting a slightly larger one.

The Pikes Peak racer used a common 1,000W 9C direct drive bicycle hubmotor. He drilled large holes in the side plates to let the heat out, and ran it at 111V. I think he used 50A, but it was a long time ago. Its rated for 20A at 48V.

Lithium batteries are typically listed as being charged full at 4.2V per cell. They will last twice as long in months of daily use if they are only charged to 4.1V, and 4.0V is slightly better. There is no benefit to charging to 3.9V.

As soon as you use a cell for a minute, the voltage has a sharp drop-off to its fat middle, where it is reasonably steady at its "nominal" average for the whole cycle. Most cells list this voltage at 3.6V-3.7V

At roughly 3.3V the useful range is used up, and voltage will begin dropping off rapidly. There is no useful range below 3.0V. That is where many BMS's and controllers set the Low-Voltage-Cutoff LVC.

72V is usually considered to be 20S when selecting matching components. Nothing wrong with using 22S or 24S. Zero motorcycles uses 28S. Many years ago, 72V was often achieved by using two 36V / 10S packs in series.
 
fatty said:
MK2R said:
Question*
Can i use an XT90 connector (or anything similar) as an AWG "ampliffier", put 2 cables in paralell. like i have one 8mm^2 cable, and i run 2 cables into that XT90 with same polarity to get similar as an 16mm^2 amp carry capacity ?
Yes, but connectors have a maximum wire size spec, and the connector boot only fits a single wire, and current is going to be limited by the connector, not the wire.

If you need more current, use a bigger connector, like a QS8 antispark, which takes 6AWG.

okay, if i understand it correctly the 8mm^2 cable have a limit of around 40A carrying, and the XT90 have a limit of 90A, so if i carry the current with 2 of those cables the cables will be limited to 80A and the connector to 90A :? am i right?
 
MK2R said:
okay, if i understand it correctly the 8mm^2 cable have a limit of around 40A carrying
Ampacity is wire insulation and application specific.
8AWG at 40A is continuous for enclosed wire. That building code doesn't apply to ebikes.
You should look up the rated current of the actual wire model (not size) you'll use.

MK2R said:
and the XT90 have a limit of 90A
90A continuous, 120A peak

MK2R said:
so if i carry the current with 2 of those cables the cables will be limited to 80A and the connector to 90A :? am i right?
No, because XT90s can only only fit 5mm2 wire, so you can't fit 8mm2 wire, let alone 2x 8mm2 wires.
 
fatty said:
MK2R said:
okay, if i understand it correctly the 8mm^2 cable have a limit of around 40A carrying
Ampacity is wire insulation and application specific.
8AWG at 40A is continuous for enclosed wire. That building code doesn't apply to ebikes.
You should look up the rated current of the actual wire model (not size) you'll use.

MK2R said:
and the XT90 have a limit of 90A
90A continuous, 120A peak

MK2R said:
so if i carry the current with 2 of those cables the cables will be limited to 80A and the connector to 90A :? am i right?
No, because XT90s can only only fit 5mm2 wire, so you can't fit 8mm2 wire, let alone 2x 8mm2 wires.

damnit, i have some 8mm wire laying around. and something thicker that say 4awg. so i need to get myself some slimmer wires then i suppose or find some larger connectors
 
MK2R said:
damnit, i have some 8mm wire laying around. and something thicker that say 4awg. so i need to get myself some slimmer wires then i suppose or find some larger connectors
Wire is cheap -- just get the largest size for your connectors.
Or get the QS8 Antispark connectors above -- they're cheap as well.
 
oh my lord, the motor is spinning :shock:
Got it today and just connected it up by the wiering diagram that was provided with it, connected it to my psu at 60V (max 8.7A) and just let the throttle twist a little and it was spinning nicely. didn't wanna test it more than a few spins. I am not sure how things would react to the 8.7A supplied when it's ment to draw up to 45A.

but the sum is it worked. i am actually starting to think that i can do this. still waiting for some stuffs to arrive thou. I got some XT90-S antispark, and that 8mm^2 cable seem to fit just as tight as it can be in there. so for the able i got, i could get away with those i guess
I am having a really hard time to find something good in english about the XT90 connector but since i managed to fit 8mm^2 cable in the connector maybe this information is correct
https://www.ebay.com/itm/293988547441?_trkparms=ispr%3D1&hash=item4473153b71:g:aPIAAOSwCm9gVz6-&amdata=enc%3AAQAFAAACcBaobrjLl8XobRIiIML1V4Imu%252Fn%252BzU5L90Z278x5ickkvjzWOStkxwnlDuxSI1PVVi0xOk%252BOL7Y74qpFuIJUs%252Bq6UrRNfkCpZgtjJaNFmOfa2r5kdAokHZ5hxNeKT3WZZJ2Ydk7vy9tdgFXsZ1lGzbvmbRIhpSDGrZsEA8MAxE4Yefq6qRTcuEvSHa%252Fygow0gmhYAyQYU70kFqBWw3PuDfzFuvBhFtnNn%252Fi70S8wXZaGWSDz5x%252FdpNQtc1agW74o1aLoPgtotzXGi1rgnZXDcchyvnxIYdQeFos%252BXHoOrUJz12JfAcijy3FhQ1kFYbfIgMfIKv0JuUodk3ICrZgXI42oJehhL7IEZWfJLIJNP1LSJNJHMYCUcsEgRHfqM063sfrYm2eN1yei4Cy5G8tNSaiJ6LhZYaUHwcNCiblkAXdwY194ZBUbrR5b%252F%252FPNDB4oSPEiamiro%252FMyYe6zXcUq1oXcJqgZn6wD5ImvdNu6j5mjrq9Odsds6z%252FpGeS7osLd%252B2cDxWG%252BQsPwHr%252F8EApA4J9mm2Q8MIqsojCJceX8Cp4A4TMQezZU53cNJFMtTPQ03pm98m6SOyRe%252BVaBS7ruVdP9wxP9yjBGbAmcXrzQOwlLaibfusD1Ny%252FfoZapTa4v17fGAR7CtwXoGXE6q91HixxEZ7vcSGpIxbtOjxePBKXbVuaP2%252B5vZ%252FOxeuzFHgERu%252FVdymmph%252BCq%252FQp7jUBgdZEtJC5uZsFb7VELvW0xuwlXn3mKph8vSrpli4yWv5DhrkmYE6pWxZyK%252BQ5KvWSSO4gZrbxI4CbgLaFaQFi1IDaiJV8SXkcREmRWm9YcJk33rA%253D%253D%7Ccksum%3A2939885474413caf26d37e3748ab93a0cbf2796aa3fb%7Campid%3APL_CLK%7Cclp%3A2334524

Maybe not look at the german text but just the numbers. or are there different versions of the XT90 connector?
 
MK2R said:
I got some XT90-S antispark, and that 8mm^2 cable seem to fit just as tight as it can be in there. so for the able i got, i could get away with those i guess
I am having a really hard time to find something good in english about the XT90 connector but since i managed to fit 8mm^2 cable in the connector maybe this information is correct

Yeah, I never found an actual datasheet from Amass -- just their catalog.
The spec is 40A continuous, 90A non-continuous, 10AWG
AMASS XT90.png
But if you can fit 8mm2, that's great! That should help the connector current capacity as well.
 
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