What Is Causing This Voltage Drop?

[PCeBiker]

Using my DIY Smart Charge Controller (poor man's Satiator) I can see the rate and ramp down with any charger.

I remember that charge controller.
Can you post a link to that again?..

I think I've got what I need to make one?

It too looks really nice in its box.

I'm pretty it was your post that inspired me to buy it.

I know that I can use it to get 5V at ~20 amps out of my 48V battery, or to get 12V to run things that plug into a car lighter.

 

[Gionnirocket]

https://www.aliexpress.us/item/3256802934338156.html?spm=a2g0o.order_list.order_list_main.5.21ef1802yrO9ra&gatewayAdapt=glo2usa

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20a DC

https://www.aliexpress.us/item/2255800150347754.html?spm=a2g0o.order_list.order_list_main.30.21ef1802yrO9ra&gatewayAdapt=glo2usa

 

[PCeBiker]

https://www.aliexpress.us/item/3256802934338156.html?spm=a2g0o.order_list.order_list_main.5.21ef1802yrO9ra&gatewayAdapt=glo2usa

+
20a DC

https://www.aliexpress.us/item/2255800150347754.html?spm=a2g0o.order_list.order_list_main.30.21ef1802yrO9ra&gatewayAdapt=glo2usa

Well it looks like I bought more than I needed.
I guess I had in mind converting my 48 volts to 5 and 12 as well as charging.

The 1200 Watt converter allows me to brew some coffee with my ebike battery,..

I could have it gimbaled and brewing while I ride.

 

[6zfshdb]

I understand what you are doing... But I'm speaking about the OP and charging with the Grin Satiator.
I've charged with my power supply but rarely.. Usually to verify it can indeed take a full charge. Most chargers shut down a few tenths short.
Using my DIY Smart Charge Controller (poor man's Satiator) I can see the rate and ramp down with any charger.
My original battery when doing a full charge would start ramping down at 54.3v.

The "standard" 52V charge program in the Satiator reduces the current down to a trickle charge as the voltage approaches 58.8. The problem is, it shuts off too soon to maintain proper cell balance. I'm sure it's done for safety reasons. The Satiator is programmable though, so I should be able to create one for occasional use that will maintain cell balance.

 

[Gionnirocket]

The "standard" 52V charge program in the Satiator reduces the current down to a trickle charge as the voltage approaches 58.8. The problem is, it shuts off too soon to maintain proper cell balance. I'm sure it's done for safety reasons. The Satiator is programmable though, so I should be able to create one for occasional use that will maintain cell balance.

The better/smarter ones do that. My original charger wouldn't put out until connected to the battery and then once a full charged was achieved it would shut down completely and not restart or trickle... as you say, for safety.
As the battery settled after charging in would end up at 54.2v
That's only 0.03v/cell so I think we can become preoccupied by the numbers.
My cheap charger will continue to trickle at 54.6 which then puts all the safety on the BMS. In this state people say it's balancing but without a balance BMS that's impossible... It's just toping off the sag after the initial charge.
My better/safer charger won't allow this.

Edit:
It's the same thing that happens after riding, especially hard.... You may see the battery down to 45v after a ride...come back in an hour after it was resting and it's 45.8v.
Did it just self charge and balance?