Anybody actually running their Chargery using the external power port connected to the pack via a diode?

Maast

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I dont remember reading somebody actually doing it, just a couple of theoretical discussions about it and a search didnt turn up anything.

I'm thinking I'm going to run my 16T through a couple of diodes in series (40v 20A diodes I've got laying around) and an small toriod inductor to connect to the 48v pack. I might do a pair of diodes each on both the positive and negative leads.

The idea is to isolate the BMS main power from any ripple coming from the inverter.

If you've done it, what were your results?
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
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I'm running four Chargery BMS8T-300's with 300A-DCC's.
I use External Power from the Battery Pack terminals to power the BMS' using the Chargery Adapter and the ISO Board between the BMS & DCC.

ISO Board Info: https://diysolarforum.com/threads/chargery-bms-dcc-solid-state-contactor-thread.11756/post-169742
Power Adapter: https://diysolarforum.com/threads/checking-chargery-voltage-measurements.14712/post-179788
The ripple issues and constant fluctuations have stopped and the passive balancing actually does behave much better too as a result.
SOC Calculations @ BMS still get wonky and it seems to me that it's a Math Error miscalculating on the lowest cell voltage to the highest cell voltage.
isopower11-8t-jpg.28642
externals-jpg.30492


< ISO board
Power board >








I have the bank tweaked out so all packs get up to 27.9V (3.4875 per cell) and leveled up nicely, typically with the cells varying <20mv. Reminder, I am also using a QNBBM-8S Active Balancer on every pack which does make a difference in leveling up the cells nicely & evenly.

SettingDefaultMy settingsNOTES
Over charge P Voltage3.653.65
Over charge R Voltage3.553.55
Over charge Current5086A / 150A0.5C rate for 174AH / 280AH
Over Discharge P Voltage3.002.65CUTOFF Trigger
Over Discharge R Voltage2.002.75Release @ this V.
Over Discharge Current300175A / 250A1.0C Rate for 174AH / 280AH
Low SOC cutoff20%0%forces cutoff @ % (faulty)
High Temp cutoff50C70C
Diff of Batt Temp1015C
Diff of cell Voltage30mv200mvUnmatched cells drift,
Temp UnitCC
Key BeeperONON
LCD Backlight1010min
Cut off Delay Time1010S
Current Calibration-SET-
Temp AlarmONON
Cell Empty Voltage2.502.50
Cell Full Voltage4.20?3.65
Default SettingEnable
Balance Parameter-SET- (OFF)*Passive is ON charge only, start at 3.30V, 30mv diff.
Battery Capacity AH1174 | 280Label Value of cells
Battery Power WH10004554 | 7168FORMULA (NominalVolt * #ofCell * AH Rating) 3.2*8*280=7168
Low Temp cut off in Charge2C2C
Low Temp cut off in Discharge-10-10C

Absorb: 28.2 for 15 minutes
Equalize: OFF
Float 27.9V
MIn Volts: 22.0 Max Volts: 28.7
Rebulk Voltage: 27.7
End Amps: 14A

This get's the bank charged to full with high amps (Constant Current) and then float (Constant Voltage) tops off so the cells are on average between 3.475-3.500. I am running 7/24/365 so float is used up by the Inverter + provides whatever the packs will take to top off.
 

Bob B

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I'm doing it with a BMS8T with a 2P4S configuration ..... just using 1 Schottky diode in series with the negative side ... and a fuse. The snip below from the 4.2 manual is what I used as a starting point .... but I added a 5A fuse on the + side and also wired the negative to the downstream side of the shunt. That way, any relay current and the BMS and LCD power will be measured by the shunt.

It really improved the accuracy of my cell voltages .... but I have heard from other threads that the 16 is more challenged for accurate cell voltages ..... please let us know what your experience is with cell voltage accuracy.

ExternalPower.png
 

Maast

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Excellent! Thank you both. I must have missed that in the manual. Since it's a 48v I'll use two of the 40v 20a diodes in the bag, just in case. Think I'm still gong to use the inductor too - mainly because I have a stripped parts bin full of gerschmutz I'd like to use up. Figure it can't hurt and might make a big difference. Also making the leads go through three turns through a ferrite before the connection points.
 

Maast

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This is what I came up with, two diodes per leg with a 330mh inductor in the middle. Just for the heck of it I measured the twisted pair capacitance and it came out at a surprisingly high .39uf aka 390pf.
P1040043.JPG
 

Bob B

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That is surprising .... I would have expected the twisted pair to be somewhat inductive .... but I'm not in the habit of measuring those kind of things.
 

Thames014

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Sep 22, 2020
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This is what I came up with, two diodes per leg with a 330mh inductor in the middle. Just for the heck of it I measured the twisted pair capacitance and it came out at a surprisingly high .39uf aka 390pf.
View attachment 41574
Can you post a circuit diagram for this 'adapter'. I plan on using this to power the Chargery BMS16T from the 16s pack.
 

Maast

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Messages
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Washington State
Can you post a circuit diagram for this 'adapter'. I plan on using this to power the Chargery BMS16T from the 16s pack.
Its just a plug-->diode-->inductor-->diode-->twisted pair wire and then the same on the other leg with the diodes. The inductors are 330uH 3A toroidials and the diodes are 20A axial schottkey that I had laying around. I think I got both from Amazon.

It does drop the output voltage about 2 volts but it doesnt really matter.

I spooged clear silicone over the back of the perf board to insulate it and then brushed on clear flex seal over the top as a conformal coating.
 
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