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DGJBD Bluetooth BMS - a short review

pierre said:
The energy yield was 1365Wh . I will have to calculate the Ah value.
Click to expand...
Pretty impressive, that with 12.5V cutt-off you could extract 100% from the pack.
By the spec, they still must have 15-20% capacity left. Looks like mfg. left a lot of +ive buffer.
Were they sourced from Aliexpress?
 
Thanks for the conversion and the calculation reference , Joe Ham. I often wondered what voltage to use for this rating
as the range is wide , say 11.5 to 13.8v , and therefor rather use the Drok inline meter that displays the energy yield.
Bhu , to answer your question : I bought the cells from an importer here in ZA and I think they are rated at 105Ah but further than that absolutely no information - may even be 2nd use by their appearance. Using a ’no access’ Daly BMS in load testing before I recorded around 1580Wh before the Daly turned off. With this BMS and after many tests and recorded configs I decided to set the pack 0% SOC at the 1360Wh level and hence the built-in buffer to protect the cells from over discharge.
 
pierre said:
I often wondered what voltage to use for this rating as the range is wide , say 11.5 to 13.8v , and therefor rather use the Drok inline meter that displays the energy yield.
Click to expand...
I believe capacity figures are calculated at nominal voltage of the battery.
In case of LifePO4 it should be 3.2v per cell.
 
Bhupinder said:
I believe capacity figures are calculated at nominal voltage of the battery.
In case of LifePO4 it should be 3.2v per cell.
Click to expand...
I see Will P uses 12v for a 4S pack if I am not mistaken , so for 105Ah that will be 1260Wh as a reference for comparing performance , so 1580Wh is a great result.
 
pierre said:
I see Will P uses 12v for a 4S pack if I am not mistaken , so for 105Ah that will be 1260Wh as a reference for comparing performance , so 1580Wh is a great result.
Click to expand...
Prismatic 4S LifepO4 pack should retain {[3.2v(Nominal Voltage) X 105Ah(Current Rate per cell)] X 4}= 1,344‬ Wh worth of power.
Still 1580Wh is way too good to be true for fresh cells (~15% more).
Most probably as you said, they are higher capacity cells with slightly degraded capacity. Well either ways you got good cells.

On that BMS, I've been seeking to check - how does it provide over-charge protection for individual cells?
Does it stop charging the complete pack on detecting voltage threshold for any of the 4 cells? or does it starts burning charge on one of those?
How good would you rate the balancing function of this? Do those thin voltage sensing wires get hot? and lastly whats the self consumption power it is rated at? Apologies for so many queries...only if you may.
 
Last edited:
pierre said:
Thanks for the conversion and the calculation reference , Joe Ham. I often wondered what voltage to use for this rating
as the range is wide , say 11.5 to 13.8v , and therefor rather use the Drok inline meter that displays the energy yield.
Click to expand...

For a "quick and dirty" calculation I just used the end voltage that I saw on one of your pictures.

That would make me happy with 105 Ah cells and close enough for my work. Others may want to be more granular.

Either way the online calculator is nice and I wouldn't have been looking for one if not following your thread.
 
Bhupinder said:
Prismatic 4S LifepO4 pack should retain {[3.2v(Nominal Voltage) X 105Ah(Current Rate per cell)] X 4}= 1,344‬ Wh worth of power.
Still 1580Wh is way too good to be true for fresh cells (~15% more).
Most probably as you said, they are higher capacity cells with slightly degraded capacity. Well either ways you got good cells.

On that BMS, I've been seeking to check - how does it provide over-charge protection for individual cells?
Does it stop charging the complete pack on detecting voltage threshold for any of the 4 cells? or does it starts burning charge on one of those?
How good would you rate the balancing function of this? Do those thin voltage sensing wires get hot? and lastly whats the self consumption power it is rated at? Apologies for so many queries...only if you may.
Click to expand...
Hi Bhu , (1) Over charge protection is on a cell to cell basis as each cell OV can be programmed and also on a Pack Voltage basis (2) you can turn the cell balance on during charging to start at a preset voltage but (3) I do not rate the balancing function highly as it is passive balancing that dumps voltage at a very low current , about 30mA and (4) self discharge is claimed at 0.1% but can also be configured should you find a higher self-discharge over time.
 
pierre said:
Hi Bhu , (1) Over charge protection is on a cell to cell basis as each cell OV can be programmed and also on a Pack Voltage basis (2) you can turn the cell balance on during charging to start at a preset voltage but (3) I do not rate the balancing function highly as it is passive balancing that dumps voltage at a very low current , about 30mA and (4) self discharge is claimed at 0.1% but can also be configured should you find a higher self-discharge over time.
Click to expand...
are you saying you can set the over/undervoltage of each cell? so its not a generic x.xx v for all cells but different for every one.
 
Craig said:
are you saying you can set the over/undervoltage of each cell? so its not a generic x.xx v for all cells but different for every one.
Click to expand...
Terribly sorry - my bad. Do not know what I was thinking at the time of posting. There is only one setting for Cell OV and UV as well as Pack OV and UV. :(
 
pierre said:
Hi Bhu , (1) Over charge protection is on a cell to cell basis as each cell OV can be programmed and also on a Pack Voltage basis
Click to expand...
Thanks! Thats interesting, did you got a chance to dig into how its trying to maintain OV at cell levels?

So the BIG question to all BMS experts:

Is it good to spend money on this relatively cheaper product with limited service support post sales
V/S
Electrodacus SBMS0 - which is not only a super-set in terms of functions & price but has a super PLUS of being OPEN SOURCE.
May be one can expect some remote support with the diagnosis and repairs if need be.
Saw the guy in YT channel Everlanders doing repairs to his SBMS, which is a cool way to maintain things than just popping out old - for new ones.
 
I use this BMS only as a developmental tool for the packs that I build. After testing and evaluation I strap on a Daly plug&play BMS , test it and give it to the client.
As to your question above Bhu , as soon as the BMS detects an OV condition it opens the Charge FET and UV condition the Discharge FET.
So far I have not had any problems with this BMS but time will tell.
 
Thanks for the response, so in nutshell it would stop charging as soon as any of the cells hit OV condition. Right?
 
pierre said:
Terribly sorry - my bad. Do not know what I was thinking at the time of posting. There is only one setting for Cell OV and UV as well as Pack OV and UV. :(
Click to expand...
I meant to say "one setting each for Cell OV and UV and one setting each for Pack OV and UV" Sorry for the confusion.
 
pierre said:
It is still better to get the Windows app to run on your computer via RS232/UART as you get access to a few more settings and the best of all , while testing the capacity of your battery pack , you do not have to wait up for 5hrs or so to monitor / record the performance . The Windows app has a feature called 'Save data' . Once activated the app saves the state of the pack to an Excel file every 1 second. Which other BMS has this function ?
Click to expand...
Hi Pierre
Received mine yesterday and all wired up and installed. Works great. Took 6 days from dispatch to my door. They did not have any RS232 connectors so just using the Bluetooth. Busy running a discharge cycle at the minute. It did a great job balancing the cells overnight too.
You have your voltage range set very narrow (2.9 to 3.4) is that for maximum cycles?

regards
 
Hi Dodger , great news man ! That really was quick service. I have about 12 different profiles developed so far and that particular profile is a more ‘conservative’ one which should result in increased lifespan - not that it is really important as the pack will outlast me anyway ;) As mentioned before , two of the cells are slightly out of whack on the upper and lower limits and that narrow voltage range favors the current pack makeup. I am waiting for more cells but my order is delayed due to Covid.
Once you start using the RS232 you can really capture so much data which will enable you to optimize your setup. I think that you could ’push’ your cells to near their limits for a few charge / discharge cycles to condition them. Enjoy experimenting and keep feedback coming.
 
Hi Pierre
Currently doing a capacity test and the BMS is keeping them well in line. Do you get your batteries via Alibaba. There are some great deals there. Some comprehensive threads on here about experiences with different sellers.
How is Cape Town doing under the lockdown! It is still my most favourite city in the world. Mulled wine at the restaurants in Fish Hoek. Hmmmmm.
Regards
 

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