$10 DIY Smart Charger Alternative / Ver. 2.0

[Gionnirocket]

Cool little circuit you’ve assembled. I totally agree that hacking is part of the fun. I hack other thing last for the same reason. I may use this for my 36v battery. Maybe I can use the same unit for a 36v battery and a 48v battery. Though, at the price, maybe I’ll make a separate one. I like to monitor my charging.

Depending on your use between the two batteries. . .
Very easy to adjust voltage and I've set it up so it's easy to swap out charger and battery input/output connectors. But if I had to change back and forth daily I'd definitely build 2 for convenience.

 

[Gionnirocket]

With a new bike and battery I had to update my charge adapter similarly to the mod' @rounds had to make.
The safety features of the Zen battery does not output voltage on the battery charge port unless it receives a handshake from the charger.
So I had to install a momentary contact switch which needs to be held for 2 seconds to initiate the charge... then it's all automatic to my desired SOC as before.


Special thanks to @Zen Support for helping with the necessary cables as their proprietary 3 pin Julet connector was impossible to source.


One question for Mr. @Ravi Kempaiah...
Is it correct to assume that Watt-hour in equals Watt-hour out?
Example...
If I charge to 50.0V
Then ride 20 miles.
Then charge to exactly 50.0V again with a total of 155Wh being input back into the battery.
Can I divide the Wh in by miles driven to have a fairly accurate Wh per mile?
(155Wh/20mi = 7.75Wh/mi)

 

[Ravi Kempaiah]

With a new bike and battery I had to update my charge adapter similarly to the mod' @rounds had to make.
The safety features of the Zen battery does not output voltage on the battery charge port unless it receives a handshake from the charger.
So I had to install a momentary contact switch which needs to be held for 2 seconds to initiate the charge... then it's all automatic to my desired SOC as before.
View attachment 173481

Special thanks to @Zen Support for helping with the necessary cables as their proprietary 3 pin Julet connector was impossible to source.
View attachment 173482

One question for Mr. @Ravi Kempaiah...
Is it correct to assume that Watt-hour in equals Watt-hour out?
Example...
If I charge to 50.0V
Then ride 20 miles.
Then charge to exactly 50.0V again with a total of 155Wh being input back into the battery.
Can I divide the Wh in by miles driven to have a fairly accurate Wh per mile?
(155Wh/20mi = 7.75Wh/mi)
View attachment 173480

Wh - in will always be > Wh - out.
There are inefficiencies with every charger, and it is safe to add 5-8 % buffer to compensate for that.

 

[Gionnirocket]

Wh - in will always be > Wh - out.
There are inefficiencies with every charger, and it is safe to add 5-8 % buffer to compensate for that

Thanks Rav'
Yes I'm aware of charger inefficiencies... but I'm measuring Wh -in post charger so the charger inefficiency are bypassed and the remaining concerns would be the wiring, the BMS and the internal resistance of the cells.
Since the generated heat in these areas is negligible (as far as I can tell)
Do you think the buffer lower (1%)... or am I assuming incorrectly?

 

[il Munduato]

Here's the $30 version.
Having the same necessity of the momentary contact switch to initiate the charge...
I opted for an Off Delay Relay which makes the process automated. This allows me to plug everything in and start a charge by a home automation timer early in the morning or by app while still lying in bed before getting up as well as saving a trip to the basement to initiate it manually.

I couldn't locate a 48v panel mount relay so I had to add a voltage step down brick.


I also changed the input to panel mount instead of the cord and connector for neatness.



It works like a charm and allows for a very granular SOC level.


Great thing is that the set up also adds multiple levels of safety as the Home Automation outlet as well as the charging relay both have adjustable maximum time settings so things shut down at a preset amount of time. Even if everything fails (2 timers + 1 SOC shut down) the worst that can happen is that you're back to the basic charger / bms shut down safety features... but having all 3 fail at the same time I find highly improbable.

 

[il Munduato]

I found myself occasionally needing to restart the Off Delay Relay if I decided to make changes to the SoC setting if my plans changed during a charge.... So instead of cycling the power on and off I decided to add a Normally Closed Momentary Contact Switch to just cycle the Relay.
Wasn't really necessary but was more fun than not doing it once I thought of it... and raising the build price to $33