Acceptable voltage margin on charger?

[null]

How much voltage difference is acceptable from chargers?

I just received a 84v 5A adjustable from 1rad, (same style as ewheels afaik) and powered on, no battery connected, shows 84.8v. Is this too much?

Measuring equipment have their margins too, will have to try with the multimeter.

Edited December 13, 2019 by null

[Seba]

25 minutes ago, null said:

How much voltage difference is acceptable from chargers?

I just received a 84v 5A adjustable from 1rad, (same style as ewheels afaik) and powered on, no battery connected, shows 84.8v. Is this too much?

Measuring equipment have their margins too, will have to try with the multimeter.

Try with multimeter. Meters built into chargers are not precise.

[Ben Kim]

40 minutes ago, null said:

How much voltage difference is acceptable from chargers?

I just received a 84v 5A adjustable from 1rad, (same style as ewheels afaik) and powered on, no battery connected, shows 84.8v. Is this too much?

Measuring equipment have their margins too, will have to try with the multimeter.

if the multimeter confirms 84.8 yes it is too high. 

[null]

Thanks for the info. I left it on for a few minutes, and the reading wend down to 84.2.
The multimeter (20yo Elro ) shows 83.6. Fairly large gap, but I'll prefer trusting the newer device. At least its probably not too much voltage, will see what it gives when charging.

edit: Turning it off for a few minutes got the display back at 84.7v which have fallen to 84.2 again.
The manual states to plug both AC and DC before powering it on, so of there is a few minutes of spike it would go straight to the wheel.

Edit: after 30 mins the display is down to 83.9v and the multimeter says 83.5v.
So it seems it stabilises slightly low.  

Edited December 13, 2019 by null

[mrelwood]

I wouldn’t worry about the no-load voltage very much. The chargers have a system in place to recognize wether a battery is connected, so it may just not stabilize from the start-up peak very fast. Also, even a $100 multimeter may have an accuracy as bad as +-1%, like mine does.

[null]

Thanks for the reassurance, I’ll post what the 18xl displays as soon as I get it back. My (tall) brother is learning on it.

[Aneta]

On 12/13/2019 at 11:10 AM, null said:

How much voltage difference is acceptable from chargers?

I just received a 84v 5A adjustable from 1rad, (same style as ewheels afaik) and powered on, no battery connected, shows 84.8v. Is this too much?

Measuring equipment have their margins too, will have to try with the multimeter.

Overvoltage is EXTREMELY DANGEROUS for lithium batteries, see recent advisory about this (or equivalent) charger:

 Many a fire has started from overvoltage. I'd consider this charger as faulty and replace it ASAP. Do not use it!

[mrelwood]

1 hour ago, Aneta said:

Overvoltage is EXTREMELY DANGEROUS for lithium batteries

It is. If the charger would apply the same 84.8V when loaded, it would eventually charge the cells to 4.24V, if the BMS malfunctions and doesn’t cut off an overcharge.

From batteryuniversity: ”Prolonged charging above 4.30V on a Li-ion designed for 4.20V/cell will plate metallic lithium on the anode.” ... which will eventually cause venting, and possibly even a fire. This is absolutely a matter that must be taken seriously.

However, we are talking about the no-load voltage here, measured with an ancient multimeter and a charger included add-on voltmeter. As I wrote earlier, +-1% is common accuracy for a $100 multimeter. That is 83.16-84.84V. Old meter or a cheap add-on can be quite a bit more off.

If the charger really does show 84.8 at the end of a charge, and the KS app shows similiar values, then the charger should definitely be checked for accuracy.

But so far the values appear common.

[Mono]

I have also experienced that the no-load voltage seems somewhat erratic and not too meaningful. And if the wheel has a diode (I assume KS does) doesn't it lose already something like at least 0.6V just there?

Edited December 15, 2019 by Mono