Battery charging anomalies

[sammich]

One last question for now concerning an Eahora x3. It is a 36 volt system with 36 volt 10.4 amp battery, without the charger. I borrowed one from a friend who also has a 36 volt, 10.5 amp battery so should be basically the same. The charger says it's output is 42 volts, 2 amps. While the charger is NOT plugged into the wall, when I plug it into the battery I get a a few Sparks at the connection initially (similar to what you would get discharging a capacitor by shorting it). Still not plugged into the wall the indicator on the charger shows a green light. When I do plug it into the wall the charger shows a red light and then when fully charged turns green (which is what I would expect). Under the same circumstances the other person's bike whom I borrowed the charger from shows no light when the battery is plugged in as long as it's not plugged into the wall and also does not spark at all when plugging into the battery itself. I have included a photo that shows a hole on my battery pack where there might have been an on-off switch in the past. If anybody is familiar with this model bike or if this battery looks familiar and you can verify what is supposed to be in that area please let me know. Also any ideas about the sparking right when plugging in or the indications before even being plugged into the wall. Thanks

 

[harryS]

Some chargers may incorporate an anti-spark feature, as do some batteries. It costs more to put in,

 

[spokewrench]

This is new to me. With the charger off, I guess it sparked because of a capacitor in the charger. Apparently, antispark connectors have a resistor path make contact before the zero-ohm path.

 

[PCeBiker]

,.. While the charger is NOT plugged into the wall, when I plug it into the battery I get a a few Sparks at the connection initially (similar to what you would get discharging a capacitor by shorting it).
,.. Also any ideas about the sparking right when plugging in

I've got three interchangeable batteries, and four chargers.

On one battery, if I connect the battery to any charger without plugging in the charger first, I get One HELL Of a spark. 🌩

The spark actually melted and vaporized some metal on the battery's charge port.



I started plugging the chargers in first for all my batteries and that stopped the sparking.
(even though the instructions for my first battery and charger said to plug the battery in first.)

This is new to me. With the charger off, I guess it sparked because of a capacitor in the charger.

My 48V 4A charger was the worst with it's Huge capacitors.
The BMS allowed current to travel backwards from the battery, through the charge port to charge the empty capacitors in the charger. In about half a microsecond.

I was doing a bit of arc welding.

 

[sammich]

Doing it bas-ackwards worked. No more Spark. Doesn't leave me that warm fuzzy feeling, but if it works .... As others implied, when building a bike on the cheap you don't waste money on silly things like resistors and diodes! Thanks for the education, all.

And I'll assume the 42volt output on the charger is correct for these 36volt batteries as well. (Just seems a little higher than necessary is all)

 

[PCeBiker]

And I'll assume the 42volt output on the charger is correct for these 36volt batteries as well. (Just seems a little higher than necessary is all)

All my 48 volt battery chargers put out 54.6 volts.
My math says a 36 volt battery should charge to 40.95 volts.

So 42volt sounds a little high?

The BMS in the battery may be able to safely deal with that, but you're plugging the charger into a different battery than it was built for, so I don't know what to think?

 

[6zfshdb]

The output voltage of a fully charged 36v lithium battery is 42V. 36v is the "nominal" voltage rating.

A charger that puts out 42v is correct for this battery.
That being said, there is always the possibility Eahora uses some proprietary technology which may alter this voltage.

Any 42v, 2 amp charger designed for lithium batteries should work for your application. Just be sure to check the plug polarity and DO NOT charge the battery unattended!
Sparking at both the AC and DC connectors is quite common with these chargers and will vary with different battery/charger combinations. It can cause damage to the DC connector over time though. A couple of my chargers spark and to eliminate possible DC connector damage, I usually plug in the DC side first. This moves the arcing to the AC plug, which is far easier and cheaper to replace if damage does occur.

Good luck with the project!

 

[sammich]

Thanks for the responses. Great chart. Yeah, no telling about anything on this Eahora. When contacted, the company stated it provides no support for this model (not even to tell me what charger it needs!) Reading other threads I see that it's fairly common with these cheaper Chinese companies to have minimal or no customer support.