16x 3.65V chargers for Enginer system

guys, I’m crazy enough to build this 16 3.65V charger! No more balancing! No more over charging! No mre hard-landing on 3.8V due to poor BMS design! All chargers use CC/CV for charging!



Pic 1) This is how it seats in the back trunk! Red light means “charging”, while green light means “completed”



Pic 2) A circuit breaker to make sure the chargers are not “too greedy” @16A




Pic 3) A wire mesh lets all the chargers seat on it. In this pic, I flipped over the whole thing so you are looking at the bottom side of the charger. Every charger is wired to an Anderson Plug for easier remove of the whole thing for later maintenance.



Pic 4) I have lost my RFE pack already. I rebuilt my 5kwh pack myself long time ago with A123 cells. Every single cell is connected to additional wires to their positive and negative terminals. The two terminals are connected to an Anderson Plug. The plug will then goes to that connected to a charger.


And every morning, I get below results,






And this baby is real hot!

 

I don't know why I can't insert pictures into my message. Anyway, Lopez, the money I spent on this charger is about USD$650. Also, I have spent weeks to build it. "Balancing" is not the only problem for Enginer's BMS. I found it also has a very hard time to accurately detect the ture values of the voltages of the cells.

 

These chargers have some down sides.
1) Really hot. If you look at my pics, it can get the cabinet as hot as 40 degree C.
2) Very power inefficent. It takes up 8kwh to fully charge my 5kwh pack. About 60% conversion efficency.
3) Heavy. Over all added weight is about 3kg.

 

Lopez, I know it’s a crazy price. But money can’t buy time! I had enough of the time I need to baby sitting the pack during balancing! You know what, it balance itself every morning!

 

Yes, Lopez, it was really a lot of work. Thanks for your comment, and I have edited the whole post! Enjoy the pictures!

 

Nort, CC/CV means constant current/ constant voltage. It is a strategy of charging cells. What it does in this strategy is the charger starts in a stage that gives constant current first, in my case 30A, in the begining of charging. When the cells reach 3.65V, CC stage ends and CV stage starts with constant voltage at 3.65V. The charger keeps charging until the current become very small (some where in mA). This is what I would call “soft landing on 3.65V. ” What Enginer BMS does is to over charge cells to 3.8v, and they believe stopping here the cells would slow go back to 3.65V resting voltage. But they were wrong! This hard-landing, or crash-landing, method badly damage cells, specially those weak cells! I have 3-4 cells were damaged this way!

 

Nort, yes, one of my chargers needed to be fine adjusted. It is a little bit over charged cell 15. And if you look closely, cell 5 also has 3.7V. But this cell is in a situation I mentioned before, a situation that Enginer BMS has hard time to correctly detect the voltage. I have checked with a mutimeter on cell 5, it has 3.65V.

 

I got the chargers from China.