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HUUUGE USB POWERBANK
#11
Quote:I could certainly add it in, then i would have to get rid of the 40 cells on top tho to make room for thr cherge controller. 
When i was deciding on how to put the cells in i noticed that i can put 120 in the base with using the stabdard cell holders but with cell holders that can package them of center to each other i can put 160 just in the base. So i can actually move all the cells into the base.

Got a link to those cell holders?

I managed to find some: Cylindrical Cell Bracket
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#12
(08-10-2018, 12:19 PM)Gerard Achternaam Wrote:
Quote:I could certainly add it in, then i would have to get rid of the 40 cells on top tho to make room for thr cherge controller. 
When i was deciding on how to put the cells in i noticed that i can put 120 in the base with using the stabdard cell holders but with cell holders that can package them of center to each other i can put 160 just in the base. So i can actually move all the cells into the base.

Got a link to those cell holders?

I managed to find some: Cylindrical Cell Bracket
Exactly thats the ones i woudlve gotten.
I had some cell holder from ebikes that i was playing with, wouldve had to chop some edges off and get rid of 2 slots for it to work, didnt want to do that Big Grin
Im working in some other holders myself tho.
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#13
(08-04-2018, 03:55 PM)Korishan Wrote: Yeah, I don't see any diodes, other than what's built in the FETs.  

Check all the solder joints and make sure all the pads are making good contact. If not, hit it with the iron after applying flux to the area (this minimizes the chances of bridging)

I suppose it's also possible that there's a FET that isn't closing all the way, but I doubt that.

The voltage drop is probably from the body diode of the charge transistors, in a configuration like an image below. 



if the charge transistor is off and the discharge is on you will get a diode drop on the output.
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#14
(08-04-2018, 02:26 PM)The-J-Man Wrote:
(08-04-2018, 01:17 PM)Korishan Wrote: Which bms did you get? Possibly voltage drop from diodes

it should be this one:
https://www.ebay.de/itm/4S-30A-14-8V-Li-...%7Ciid%3A1

I seem to have exactly that BMS in my stock, but didnt use it until now.
 
I will build up a mock unit to measure.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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#15
Done.



Voltage drop @1 A (both directions) about 6,4 mV. With Rdson 5mOhm, 5 parallel 2 in series, plus 2mOhm from the resistors this is close to what can be expected.

On overvoltage from the cell at charging the Fets open, they are sitting in the Minus line.
I didnt check the 30 A shortcut.....

Its exaxctly as can be expected.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
Reply
#16
(08-10-2018, 08:27 PM)Gregor Scott Wrote: The voltage drop is probably from the body diode of the charge transistors, in a configuration like an image below. 



if the charge transistor is off and the discharge is on you will get a diode drop on the output.

So a BMS with separate charge and discharge ports would solve the issue?

(08-15-2018, 05:03 PM)Cherry67 Wrote: Done.



Voltage drop @1 A (both directions) about 6,4 mV. With Rdson 5mOhm, 5 parallel 2 in series, plus 2mOhm from the resistors this is close to what can be expected.

On overvoltage from the cell at charging the Fets open, they are sitting in the Minus line.
I didnt check the 30 A shortcut.....

Its exaxctly as can be expected.
thanks you checking that out
No voltage drop when idle at all? 
Makes me think I connected something wrong, then again thats not possible with such a small drop...
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#17
(08-18-2018, 11:25 AM)The-J-Man Wrote:
(08-15-2018, 05:03 PM)Cherry67 Wrote: Done.



Voltage drop @1 A (both directions) about 6,4 mV. With Rdson 5mOhm, 5 parallel 2 in series, plus 2mOhm from the resistors this is close to what can be expected.

On overvoltage from the cell at charging the Fets open, they are sitting in the Minus line.
I didnt check the 30 A shortcut.....

Its exactly as can be expected.
thanks you checking that out
No voltage drop when idle at all? 
Makes me think I connected something wrong, then again thats not possible with such a small drop...
No voltage drop (except the mentioned 6.4 mV) at 1 A charging or 1 A Load.
No "diode loss" in any direction.
Definitely.

I cant be sure that your BMS is ok, but mine shows as i described.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
Reply
#18
(08-18-2018, 03:38 PM)Cherry67 Wrote:
(08-18-2018, 11:25 AM)The-J-Man Wrote:
(08-15-2018, 05:03 PM)Cherry67 Wrote: Done.

Voltage drop @1 A (both directions) about 6,4 mV. With Rdson 5mOhm, 5 parallel 2 in series, plus 2mOhm from the resistors this is close to what can be expected.

On overvoltage from the cell at charging the Fets open, they are sitting in the Minus line.
I didnt check the 30 A shortcut.....

Its exactly as can be expected.
thanks you checking that out
No voltage drop when idle at all? 
Makes me think I connected something wrong, then again thats not possible with such a small drop...
No voltage drop (except the mentioned 6.4 mV) at 1 A charging or 1 A Load.
No "diode loss" in any direction.
Definitely.

I cant be sure that your BMS is ok, but mine shows as i described.
Cheers for the info.
I contacted the seller and he said its normal. Of course he would say that but for 7.17€ I cant be bothered taking it all apart again and sending it back. Maybe one day I pop a new BMS in. 
For now the pack is standing on top of my powerwall Big Grin
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