Charger pulsating Amperage?

[null]

As a replacement for my 18XLs stock charger I got a small 300W set at 84V/3A in order to have a bit of headroom (have a 9A for travel)

The Amperage (built in display) is pulsating between 2.8A and 3.5A. On the larger charger of the same type it is stable. 
The rhythm could remind of the pulsating sound people are noticing on the YZ-450.

Should this be normal? Charged Voltage as shown by the EUC is very even.
It is not controlled by pots but an MCU which is programmed by some serial thingie.

(very boring video, only fluctuating numbers in real time)

Edited May 14, 2021 by null

[Chriull]

1 hour ago, null said:

Should this be normal? 

Does not seem very trustworthy.

But imho nothing (immedeately) dangerous - just bad design?

If you can return it i'd send it back.

[null]

Thanks, yes I haven’t seen this elsewhere. I’ll see what I can do.

I like the monitoring feature, but suddenly you see the stuff you might have lived happily with without knowing

Anyhow, safe side best.

Edited May 14, 2021 by null

[Mantraguy]

I have a cheap 'fast' charger that came with my Gotway Tesla V2; it's supposed to be 5A but only actually outputs between about 2.5 and 3.2A. It doesn't have a display but I use it with a Charge Doctor and plot the charge graphs. The current on it fluctuates constantly from about 2.5 to 3.2A, and the average current drops gradually when in CC mode. Once it gets close to 100% the current drops as you'd expect (CV mode) and at that point, the current is stable. It seems to work just fine; balances the batteries well etc. I've been using it for around 6 months and haven't had any problems; it just doesn't charge as fast as advertised (supposed to be 5A) and fluctuates a lot. There are no potentiometers inside so nothing to adjust.

[null]

Thanks for sharing @Mantraguy .
Good to know yours have functioned well in spite of the weird system. The charging itself looked well enough, and amperage was reduced same as yours; still fluctuating but lowering. Sadly it id some weird stuff towards the end, a bit early it stopped charging, but went into some sort of probe battery mode where the 18XL turned off and on repeatedly. I suspect the schoky / anti return diodes might have something to do with it, and / or the charger might be set for the wrong battery chemistry. (the pulses?).

The seller is the factory in China, they mainly focus on bulk so I probably won't be able to return it. As it is programable I might try to get the device to do it (just 5€) and hassle around with inexistent documentation in Chinese. Will report back.

It's a C300M BTW, been happy with the other chargers from them, including another MCU controlled which work fine with the 18XLs reverse diodes.

Will report back if any news. Preparing an overview of these chargers.