non-zero, powered-off battery voltage???

[Doug Devine]

Does anyone else get a positive voltage reading on their battery pack with it powered off? I always found that strange. When I plug in my voltmeter probes, I get about 25V but it quickly decreases and then it steadies around 12.5V. Removing the probes and reinserting them repeats the aforementioned. (These numbers vary, depending on level of charge of the battery, but they're never 0V.)

Why is there any voltage coming out of a powered off battery??? Is this a feature or a bug?

(btw, I get expected voltage readings with the battery powered on...ie, the actual battery voltage.)

 

[OrangeWagon]

Yes, there is some charge still in the system. I didn't test the battery directly, but noticed that after turning off the battery, I can still turn on the LCD briefly.
No biggie IMO

 

[SLove]

Sorry, slightly different topic but it seems like you may have done this in your tests. Do you you know how many volts Rad has wired to run to the front lights?

 

[Pa1adin]

Sorry, slightly different topic but it seems like you may have done this in your tests. Do you you know how many volts Rad has wired to run to the front lights?

The front light runs at 48v. If you want to run a light off of the main power you will need a 48V light or reduce the voltage down to 12v using something like this:
https://www.amazon.com/gp/product/B0151BF6DI

Of course you can use other reducers at other voltages.

 

[SLove]

Thank you so much! The people on this forum are awesome.

I actually ordered this:

https://www.aliexpress.com/item/1X-...32812299433.html?spm=a2g0s.9042311.0.0.BCpnnG

and then I'm going to get some LED strips and wire them in parallel for rear lights and to be seen from the sides.

 

[Lost]

There is likely a "pull up" circuit on the solid state switch. It would be fed by a high resistance resistor and a cap that gets charged by it. You would have a higher voltage initially until the load of your meter drains it out to the pull up voltage through that high resistor.

 

[Doug Devine]

Good info, guys, but not the intended thrust of this thread.

I'm talking about the naked battery back...NOT connected to the bike. Just sitting on a table, for example. If you stick voltmeter probes in your tabled, unpowered pack, do you get a positive voltage? I do and it's not intuitive that should be the case. I'm wondering if your pack presents with the same behavior.

And the weird thing is that the steady state voltage varies greatly. When I originally posted, it bottomed out at 12.5V. Now, it bottoms out at 6.8V. And I just charged it to 90% (53.3V). If this is a big-ohm resistor/capacitor phenomenon, wouldn't there be consistency in the steady state voltage? Shouldn't it bottom out at the same voltage every time?

Isn't the whole point of the power button on the pack to serve as a switch for power coming from the battery? Like a wall switch in your house. I wouldn't expect partial voltage to be able to flow when I flip my wall switch off.

(As I finish this post, the updated bottomed out voltage is 7.2V.)

 

[Lost]

Good info, guys, but not the intended thrust of this thread.

I'm talking about the naked battery back...NOT connected to the bike. Just sitting on a table, for example. If you stick voltmeter probes in your tabled, unpowered pack, do you get a positive voltage? I do and it's not intuitive that should be the case. I'm wondering if your pack presents with the same behavior.

And the weird thing is that the steady state voltage varies greatly. When I originally posted, it bottomed out at 12.5V. Now, it bottoms out at 6.8V. And I just charged it to 90% (53.3V). If this is a big-ohm resistor/capacitor phenomenon, wouldn't there be consistency in the steady state voltage? Shouldn't it bottom out at the same voltage every time?

Isn't the whole point of the power button on the pack to serve as a switch for power coming from the battery? Like a wall switch in your house. I wouldn't expect partial voltage to be able to flow when I flip my wall switch off.

(As I finish this post, the updated bottomed out voltage is 7.2V.)

Yes, I'm talking about the circuitry within the battery itself. It is actually a rather complex bit of engineering in the battery.

 

[Pa1adin]

I guess my question would be why does it bother you so much? You planning on connecting it to something while off the bike?

Was it ever stated that this button completely cuts ALL power and it is not functioning as stated?

I believe the main power button turns off power to the USB ports. though I never measured it. It may also put it in a specific state to be charged. If it does not completely turn off power to the bottom port that is not a huge deal. Could be various reasons why you can still measure some voltage while it is in the "off" position. As Lost stated above, you could just be reading voltage stored in capacitors etc..

Lots of , maybe most, EBike batteries don't have a power button at all and you can always measure the full stored voltage while off the bike.

Having a power button is just the design of this particular battery. Some people don't like that you have to use a separate power button and turn that on before you can then press the mode button to power the bike. I never thought is was a big deal at all.

So maybe it is there to be able to turn off the external USB power, and reduce the voltage for charging or other reasons.

Having some voltage remain with the button off is a non-issue IMHO.

 

[Lost]

Yes, all part of the design. Just because there is voltage at the output, there is no useful energy available, it has an incredibly high internal resistance at this point.

 

[Trail Cruiser]

Does anyone else get a positive voltage reading on their battery pack with it powered off? I always found that strange. When I plug in my voltmeter probes, I get about 25V but it quickly decreases and then it steadies around 12.5V. Removing the probes and reinserting them repeats the aforementioned. (These numbers vary, depending on level of charge of the battery, but they're never 0V.)

Why is there any voltage coming out of a powered off battery??? Is this a feature or a bug?

(btw, I get expected voltage readings with the battery powered on...ie, the actual battery voltage.)

It's like a garden hose. You turn off the faucet but there's still residual pressure in the hose itself, but it will quickly drop down to zero once you open up the tip of the hose with a quick but short squirt. Or water will slowly trickle down from various small leaks in the hose itself until the pressure drops down to zero.

 

[larry-new]

There's also voltage in the bike with the battery removed.

 

[AHicks]

Without the circuitry that's discussed here, you're going to get a big POW spark (harmless, but it WILL scare you into next week!) when connecting the charger to the battery.