Unloaded hub motor spinning to reduce battery voltage

[calab]

I need to lose about 1 or 2v total from 48v 13ah with the bike upside down should I leave the throttle wide open and how long would it take I have a flat tire and not in the mood to change it until everything dries it is a 30a controller and I just put it at full throttle and recorded the voltage so will see in an hour some real life testing motor simulator set at 0lbs rider weight, 0watts, full recumbent 14wh/km then 9kg for motor weight says 14.1wh/km

update I started wide open throttle on the 26" 2.25" with 30a at 6:53pm and it went until 8:37pm and it lost 3.50v I was retarded and forgot I had it in the garage at wide open throttle I was going to check after an hour but after 1 hour 44 minutes 104 minutes 1.75v for 52 minutes

 

[calab]

I want to find something I can just plug the battery into to drain the battery at reasonable rate to discharge the battery current I believe normal incandescent lights would work. I just tried it real quick on a little table lamp rain drop 40w light and it lit up the amp reading on the 10a scale was 0.20a voltage is 53.5v its not much to be useful 100w bulb might be 0.50a then put ten 100w bulbs to get 5a. I need this in the form of cheap thrift store heaters or freebies.

I have so many ideas with so much stuff laying around, I have a space heater in the garage, the 20" floor fan pulled 0.38a at 53.5v but blades did not move, clothes iron might be to electronic for dc, hair dryer coils, old stove coils would be cool to find for free.

I looked closer at the toaster with one panel being one sided continuous wire was 34.7ohms and pulled 1.5a at 53.5v
Parallel panel is 48ohms in parallel with 50ohms making half in theory 24.48ohm but 26.6ohms when measured, I spliced the two parallels which was dumb of me but easy to fix and now its easier to understand.
Then I put the single sided panel 34.7ohms in parallel making total 15ohms that pulled 3.5A and I believe its p=v*a 150w how interesting to see what the heat will be.
I will roam the alley ways for a toaster and get the total ohms down to get 7 to 10a which is another panel or two that I can cut the heating wire into what I want. Next step is make a rig to hold the panels and put a fan to disperse the heat. I never good at formulas or math its easy v=ir
10a is 53.5v=10a*5.35ohms but power is 535w bare skin on panel got hot to skin in 20-30s
15a is 53.5v=15a*3.50ohms but power is 802w
20a is 53.5v=20a*2.675ohms but power is 1070w
Two slice toasters are 700w and I have 1.5 slices of the toaster might be glowing red wire pulling 10a at 5.35ohms

 

[calab]

Speaker wire is 0.90mm in diameter using 4 or 5' length with one cheap meter in series to measure current the toaster wire is 36" and it never got hot only the toaster wire gets smoking hot at 2.5a draw, for 2s2p at 2.2a was not smoking but hot when skin was near usually from 7.50-8.00v for 1s2p its 1.25a anywhere from 3.70-4.10v. 48v battery I connect the panels in parallel and I have not measured current because I blew all my fuses, I could test voltage drop and the heat dissipated by the toaster wire was fine the battery bms was my safeguard.

The formula's I came up with in my spreadsheet are volts = Whatever your working with 4v 8v 36v 48v 52v
The discharge amps you want for 4v is 1a 8v is 2a 36v around 15a I did not want to work the battery to much with such a high discharge c rate.
Total power dissipated
Ohm value to achieve amp draw which has a heat watt power
Total Power is volts * amps
Watts/Amps^2 is Ohms = total power/(Amps^2)


When I work with 48v I use both panels because it dissipates the heat really well with some 12v pc case fans hooked up to any battery I have nearby to help dissipate the heat. I remember d.bass bought a bunch of heaters to measure and test his batteries on the lab bench table. What else might work could be pancake griddles but the toaster wire panels work great you can move the tap points around for different voltages. I need 7.2 ohms to be able to dissipate 180w for a current draw of 5a on a 36v battery or whatever your open voltage is 41v 38v 34v will have slightly more or slightly less current draw for same slight heat watt variance.

 

[E-HP]

If you have an old electric stove, then make a harness with this and an XT-90.
https://www.homedepot.com/p/Partsmaster-Range-Receptacle-PM17X104/100135001

The large elements are a little over 25 ohms, and small ones are 45 ohms.

 

[calab]

For battery discharge I first just used 12v fans but they take 0.5a each. Toaster wire is 0.48ohms resistance per inch you can use a lot of different items stove top coils would have been good to have or hair dryer hair curler clothes iron. I am going to make my own heated clothing for the winter with some ultra thin vape coil wire an inch is 2.7 ohms but its not insulated which is not good for skin burn safety, the meter leads are 0.3ohms I have 600 feet of 38ga nichrome 80 to use up heated handlebars if I treat myself nice.

If you have an old electric stove, then make a harness with this and an XT-90.
https://www.homedepot.com/p/Partsmaster-Range-Receptacle-PM17X104/100135001

The large elements are a little over 25 ohms, and small ones are 45 ohms.

 

[E-HP]

For battery discharge I first just used 12v fans but they take 0.5a each. Toaster wire is 0.48ohms resistance per inch you can use a lot of different items stove top coils would have been good to have or hair dryer hair curler clothes iron. I am going to make my own heated clothing for the winter with some ultra thin vape coil wire an inch is 2.7 ohms but its not insulated which is not good for skin burn safety, the meter leads are 0.3ohms I have 600 feet of 38ga nichrome 80 to use up heated handlebars if I treat myself nice.

If you have an old electric stove, then make a harness with this and an XT-90.
https://www.homedepot.com/p/Partsmaster-Range-Receptacle-PM17X104/100135001

The large elements are a little over 25 ohms, and small ones are 45 ohms.

Just responding to the original post/issue of reducing your battery 1 or 2 volts, since doing so at a couple of amps will cause less voltage sag, so easier to get to the voltage you want. I higher current might show a 2V drop as soon as you hook it up, so harder to monitor the actual drop except through trial and error. The stove coils are just about the right resistance, and no fans needed; just bring your battery to the kitchen. :thumb:

 

[amberwolf]

The stove coils are just about the right resistance, and no fans needed; just bring your battery to the kitchen. :thumb:

I have a few old stove elements kept around specifically for battery load tests. You can parallel as many of them as you like for higher loads.

They do get pretty warm even on a 36v pack, so I recommend mounting it so that it doesn't touch anything while in use. As you get closer to whatever voltage the stove was designed to operate on, they'll be even hotter (like turning up the knob on the stove), so you can do serious damage with one if not mounted away from things to prevent that.

BTW, if you remove the connecting bracket between the element ends where it would plug into the stove, you can spread the contacts apart or bring them together just enough to be able to directly plug one of these into the slots of an ebike battery that has that type of connector for a slide-in mounting plate.


An old toaster oven makes a "safer" load of this general type, as it is already enclosed and "heat safe". If the electronics / thermostat in it can't operate on DC or on the voltage you are using, you can bypass them by directly connecting the elements to the cable you will operate the test from.

There are usually four single-bar elements inside one; some have two U-shaped elements, etc. Sometimes the bottom pair are seriesed originally, someitmes paralleled with each other (same for the top). If you parallel the elements instead, you'll get twice the current. If you run both top and bottom elements paralleled, you'll get twice the current, too. (so four times the current if all elements are paralleled, if none were originally).