Inside the Big Battery 48v BDGR 2.1 kWH Battery Pack

bluetrepidation

New Member
Hello, inside this pack there is a Samsung battery module in 12s 1p. Samsung Module Tag Does anyone know the original use of this? I also made a quick video of the charger and battery pack that comes with the 4.2 kWH 48v golf cart kit...
It's interesting that the BMS inside is labeled LiFePO4 but the BMS allows 4.2 volts per cell. BMS Label Why would they label this incorrectly? Or is Big Battery programming these generic BMS modules? Thoughts?

Thanks,
A.J.
 

Richard Lee

New Member
Yeah, it seems like mine might be 12 "NMC/LI-Ion Cells". 12 x 4.2v = 50.4v the recommended charge voltage.
Mine have been running 50.4v for a while. I wonder if a little lower charge voltage would extend the cycle life? Maybe 49V or 4.0833v per cell?
 

bluetrepidation

New Member
The label shows 3.7V LiFePO4, not typical 3.2V LiFePO4. Did you check the Voltage of each cell?
Yes the pack tops out at 50.4 volts or 4.2 volts per cell. You are correct 3.7v would be the correct nominal voltage. I guess the LiFePO4 shouldn't be taken literally.

A.J.
 

bluetrepidation

New Member
Yeah, it seems like mine might be 12 "NMC/LI-Ion Cells". 12 x 4.2v = 50.4v the recommended charge voltage.
Mine have been running 50.4v for a while. I wonder if a little lower charge voltage would extend the cycle life? Maybe 49V or 4.0833v per cell?
I tend to keep my packs at half charge and top off when I plan on using them. It's more about the time the pack sits at full charge as well as the max charge voltage. There is a little adjustable trim pot for the charger voltage you could reduce if you wanted.

A.J.
 

Richard Lee

New Member
I'm trying to use these for a back-up power source during grid failures. So, staying at a good SOC would be idea.
I've read advice somewhere about not leaving them at full-charge for too long. Also discharging them (by some percentage?) periodically.
So, I'm thinking of setting my solar charger for 49v and use up some Amp hours every weekend (while I'm home).
Since I'm a newbie, I'm not up to speed on Best Practice for getting some BDGRs to last a few years.

My other problem is weather, if it looks like rain all week, I would skip a discharge cycle because I might need power on sump pumps.
And if's going to overcast for 4 or 5 days, I don't want to be too low on AHs. Have to work around the awful MA weather.

Found this today: https://gocarlite.com/product/48v-12ah-lithium-ncm-battery/
"NCM cell has 3.6 +/- 0.5V nominal working voltage and is cut-off at 4.15-4.20V per cell during charging."
I guess NMC are NCM the mostly the same chemistry.
So, if my BDGR pack cells are being floated at 4.2V on every sunny day, would that shorten their life span as a back-up supply?

Cheers,
Rich
 
Last edited:

bluetrepidation

New Member
I'm trying to use these for a back-up power source during grid failures. So, staying at a good SOC would be idea.
I've read advice somewhere about not leaving them at full-charge for too long. Also discharging them (by some percentage?) periodically.
So, I'm thinking of setting my solar charger for 49v and use up some Amp hours every weekend (while I'm home).
Since I'm a newbie, I'm not up to speed on Best Practice for getting some BDGRs to last a few years.

My other problem is weather, if it looks like rain all week, I would skip a discharge cycle because I might need power on sump pumps.
And if's going to overcast for 4 or 5 days, I don't want to be too low on AHs. Have to work around the awful MA weather.

Found this today: https://gocarlite.com/product/48v-12ah-lithium-ncm-battery/
"NCM cell has 3.6 +/- 0.5V nominal working voltage and is cut-off at 4.15-4.20V per cell during charging."
I guess NMC are NCM the mostly the same chemistry.
So, if my BDGR pack cells are being floated at 4.2V on every sunny day, would that shorten their life span as a back-up supply?

Cheers,
Rich
Yes keeping the pack at 4.2 v per cell will shorten the life. But don't worry. Maybe only charge to 4 volts per cell instead. You actually won't loose to much capacity since the discharge curved is very "flat" except at the ends. Maybe run a capacity test and see.

A.J.
 

Richard Lee

New Member
Yes keeping the pack at 4.2 v per cell will shorten the life. But don't worry. Maybe only charge to 4 volts per cell instead. You actually won't loose to much capacity since the discharge curved is very "flat" except at the ends. Maybe run a capacity test and see.

A.J.

Thanks! They are at 4.0833 right now. The TS-45 is set for 49 volts. I'll take it down to 48v, (4.0) next time I get down there with the laptop.
Since I'm 75 years old, maybe I don't need these batteries to last for a very long time.. :)
 

bluetrepidation

New Member
Thanks! They are at 4.0833 right now. The TS-45 is set for 49 volts. I'll take it down to 48v, (4.0) next time I get down there with the laptop.
Since I'm 75 years old, maybe I don't need these batteries to last for a very long time.. :)
My neighbor is 103 years old, swims daily, and drives still.
 
Top