Any test to discover controller AMP rating

[minexplorer]

As i understand it .A motors watt rating,is based on the nominal Amp output of the controller.Typically a 36v 250w motors controller is 7-15 amp. Hence 7amp x 36 volt =250w motor.
The bike ive been working on was originally 24v.Motor rated 200w ,with only one level pas (full power). Logically it seems,to get a 200w rating,with the controller always giving full power.It must be limited to 9amps? Or do these one level pas also ramp down ,when full speed is attained. So may be 9 - 15 amp?
So far,with d8vehs expertise ive fitted a 36v battery and volt meter and converted the pas wiring to a throttle.I now have full control of the power output.
My conundrum is. If these 6fet controllers can safely run 20amps (not continously of course).Id rather like to try the shunt mod im reading about.Give the controller a 17 -18amp top end,for those hill moments.
Its a typical 6fet controller,50v capaciters.Shunt wire about 20mm long.
So adding solder (how thick?),to a third of the length is safe and will give a 3-5 ? amp increase.Sounds good,but i need to be sure what the controller is originally.It may already be 15+amp max . Is there any way with a multimeter to find out? .Much thanks,if anyones got some info.

 

[anotherkiwi]

You can get peak Amps readout from a Watt meter:

- charge battery to full and put Watt meter between battery and controller
- point bike at steep hill and full throttle it
- read the max Amps pulled as well as peak Watts etc

Yesterday I charged my 12S battery up to full (49.5v) and went out for a quick thrash and got the full 735W peak Amps (49v x 15A) The controller is in a plastic controller box so I don't know how hot it got though.

Other good news is the b+m headlight rated for 42v has no problems handling +49v, it is a little brighter

 

[wheeliepete]

Something like this will do the job connected between battery and controller. It will log max amps and watts, so you do not need it in view while you are riding. Useful bit of kit to gauge power use on a ride. Keep it dry, as it is not waterproof.

https://www.ebay.co.uk/itm/1pcs-LCD-RC-High-Precision-Power-Analyzer-Tester-Watt-Meter-150A-60V-New/263484838748

 

[minexplorer]

Thanks guys, thats just the job.Good tool to have,even if not kept
Permanently connected.

 

[Deleted member 4366]

As i understand it .A motors watt rating,is based on the nominal Amp output of the controller.Typically a 36v 250w motors controller is 7-15 amp. Hence 7amp x 36 volt =250w motor.

200W is just a label for compliance. It has nothing to do with motor or controller power.

If you're still using the original 24v controller, it's most likely 12 or 14 amps, and you can safely go to 18 amps. Just put a big blob of solder on one leg of the shunt and you'll be fine.

If you want to be exact, get a cheap wattmeter. Stick it in between the battery and the controller. Lift the wheel off the ground, spin it up with the throttle, and while at full throttle, apply the brake to slow the wheel right down. That will show the maximum current. Repeat after adding the solder to see the difference.

 

[minexplorer]

200W is just a label for compliance. It has nothing to do with motor or controller power.

If you're still using the original 24v controller, it's most likely 12 or 14 amps, and you can safely go to 18 amps. Just put a big blob of solder on one leg of the shunt and you'll be fine

hi d8veh. Im only after a moderate tweak ,so if its likely 12- 14 and a blob of solder will add a few more,thats good enough. The watt meter idea looks good.If i get one,being able to test it in the shed and take it off again,is more what i had in mind.Thanks

 

[minexplorer]

hi d8veh. Im only after a moderate tweak ,so if its likely 12- 14 and a blob of solder will add a few more,thats good enough. The watt meter idea looks good.If i get one,being able to test it in the shed and take it off again,is more what i had in mind.Thanks

Finally fitted a watt meter the other day.Decided to fit as a permanent display screwed to a bike light bracket.Used d8ves method of running the black wire only to handlebars & back with 14 awg .Removing the thick red wires from the meter and using a single thin wire off the Pos for power.A much neater job all round when shrink wrapped. A few dabs of silicon for water proofing in case of a shower.But used connectors at the meter ,so i can take it off if it really pours and connect wires together.
As to testing the single speed controller.I found without load i had a good range of power adjustment with the throttle.Compared to either off or full power with the former pas.However under actual riding conditions, it was immediately apparent theres still only off or full.
The bike was originally 24v 200 watt rated. I was suprised to find the controller was no more than 9 amps. With the 36v its around 350 watts.Ive added some solder to the shunt. Now its hovering around 14 -15.5 amps ,550 watts,on both level ish or hilly terrain.Drops on dead flat/slightest downgrades tho.
The bike has a single 16t freewheel 42t up front ,so the most power for hills is desirable.Its improved significantly ,but id like more. Ive been told a basic controller will take 20 amps,18 to be safe and the brushless hub motor 1000watts (tho not continous). So will i be ok going to 18 amp, Around 660- 700 watts ? I intend to be peddling, without assistance all the time ,on flat terrain,when im not bothered about speed. Though as ive said once the trottles on, its hard for it to not be full power.
Unlike my bbs01 350w, i didnt notice any heat on the motor casing after long inclines at 14 -15 amps. Some time ago i did notice the
Controller got very warm (when only 9 amp) slowly climbing a 2mile hill . (I had sealed its compartment somewhat against water tho, which ive now reversed). Will more amps = faster climbing/efficiency = less stress/heat,for motor and controller?
Anyones two penneth worth, much appreciated.

 

[anotherkiwi]

More Amps = more Watts = more controller heat...

 

[Deleted member 4366]

The controller will heat up more if you increase the current, but you will be going faster, so the time under full power will be less, so not all bad. As I said, most small controllers are OK at 18 amps, provided you're sensible. I've run one at 24A without problems, but that was on a two-motor setup, so each controller had an easier time.

You always need to be mindful of the battery. Many cheap ones start cutting off around 20A.

 

[minexplorer]

You always need to be mindful of the battery. Many cheap ones start cutting off around 20A.

I think the battery will be ok d8veh. 14.5ah 5p10s LGmg1 cells. From Elifebikes (pswpower).Says 25A continous, 50A pulse.

 

[Deleted member 4366]

I think the battery will be ok d8veh. 14.5ah 5p10s LGmg1 cells. From Elifebikes (pswpower).Says 25A continous, 50A pulse.

Go for it then.

 

[harrys]

I have several of those wattmeters. The first one I owned seemed to give watt-hour numbers I could believe. Then I broke it, or it broke itself, and the replacement gave far lower readings.

That led me to try two more, and all were inconsistent on WH, up to 50% different, except that the AH was reproducible when I put them in series. So I use them to assess batteries and usage. Nice to have anyway.

 

[Deleted member 4366]

You can make a current meter, All you need is 100mm of 14g wire with a voltmeter attached to the ends. if your battery wire is already 14g, you can scrape off the insulation in two places 100mm apart. The resistance of 100mm of 14g wire is 0.001 ohms, so each amp will cause a voltage drop of 0.001v. Set your voltmeter to read mV scale and the reading is the number of amps flowing.

 

[minexplorer]

I have several of those wattmeters. The first one I owned seemed to give watt-hour numbers I could believe. Then I broke it, or it broke itself, and the replacement gave far lower readings.

That led me to try two more, and all were inconsistent on WH, up to 50% different, except that the AH was reproducible when I put them in series. So I use them to assess batteries and usage. Nice to have anyway.

I cant say ive looked at the AH & WH readings harrys .Ive only been interested in the controller AMPs , motor watt output & batt voltage readings. The watt output readings im seeing are correct for the Amps x voltage at that moment. The battery cut out at the correct voltage after 20 miles.The last few miles had a little less power on hills.With the meter showing the motor producing lower watts for the same Amps .Consistent with the lower batt voltage..
As i increased the max Amps from around 9 to 14/15 then to 16/17 the bikes performance improved consistantly.It climbs hills with a dramatic improvement now ,i even did an unintentional wheelie pulling away,giving too much throttle. The motor case didnt even get warm ,despite running at 16.5 to 17.5 Amps much of the time.The amp draw drops much lower on level ground,but no drop in performance . I wont add any more solder to the shunt ,its only a small 6 fet controller.The watt meter enabled accurate tinkering.