Battery sandwich - different approach to DIY powerwall (based on 18650s)

roman2

New member
Joined
Mar 17, 2021
Messages
12
I've done balancer heat up test.

THE GOAL:
Temperature measuring on cell during the durability test on the highest possible parameters.


SETUP:
- ambient temperature 22.8 celsius degree, humidity 40%
- room with no mechanical support of air circulation (no window open, no fan, no air conditioning)
- infrared thermometer used: Parkside PITA 1
- one additional "contact" sensor
- one kit (8 x 18650), one (of two) balancer will be enabled and active in continuous mode (due to voltage > 4.19v)
- brand new cells 8 x LG INR18650MJ1, and one additional random cell (not connected at all)
- cells charged to 4.25v
- additional power supply connected, configured to around 4.25v / 500mA, to give enough power to the balancer and make sure that the voltage stay at this level for whole test
- the main object of this test is the cell, which is the most exposed to the heat from the resistors
- the second object is cell, which is not connected to anything and stay in my pocket in my trousers during the balancer will be active, just for reference


PROCEDURE:
Just enabling the balancer and see what happen ;)
1. Start the balancer and measuring the temps on the sensor/test points in period. Balancer will be enabled until temperature on all of the sensor points stabilized
2. Turn off the balancer and processing measurements until temp stabilized

SENSORS / TEST POINTS CONFIGURATION:
A - "contact" sensor glued to the bottom of the cell, precision 1 degree
B - temperature of cell casing, precision 0.1 degree
C - temperature of cell casing which stay in my pocket during the test, precision 0.1 degree

THE RESULTS:
Duration: 110 minutes
20210410_174154.jpg20210409_131029.jpg20210409_131328.jpg20210409_131413.jpg20210409_134944.jpg

heat-test.png



- Sensor "A" is not flat, height is 2-3mm, so temperature from this sensor is not temp of the bottom of cell, It's rather the combination of: temperature of the bottom of the cell and temperature which the cell is exposed to from the back of the board.
- monitoring temp with IR thermo does not much sense on the PCB or resistors, there are some weird measurements, because the reflections. I've measured this on the warm up with the "touching sensor", the resistors get like 80 celsius degree and they stay on this level, the pcb very near the resistors could get roughly 65, the other side of board (the side in the front of bottom of cells) is like 45 in the hottest place.
- overall the cell was heated to max 29.3 degree celsius (from 22.5) and temperature stabilized at this level, so it's roughly 7 degree more, during the 90 minutes heating
- the cell which was in pocket in my trousers get much and quicker heated, it looks like human body is a better heater to cells then balancer's resistors
- depending on the ambient temperature, especially if the ambient temp was higher the final result for sure would be higher also, but I suppose that won't work in liner way.
- conditions of this test are as I described above, the results could be different depending on battery pack design (especially the size) or higher ambient temp, but I suppose temperatures that could be dangerous to the cells are unattainable.


Don't hesitate to comment, ask, give ideas about this test, etc
 

italianuser

Active member
Joined
Feb 25, 2020
Messages
246
My solar system starts at 8:30am with the sun and my battery packs. My house is powered just like the utility company would do it. When the sun goes down we are watching a little TV or on the computer still on battery. (snip) Everybody I know see my bill is really low but can't believe it is so. Only thing that matters is I am happy and I am not going to lie to myself about my system. It is what it is.
Wow, that's the way I think! Don't know if you know that in Italy on an electricity bill of 100€ the electricity cost is around 25€ and all the rest is taxes... :cautious:

But in any case I don't want to pay for electricity if solar can do it for me yeahh! :giggle:
 

J_Mack58

Member
Joined
Apr 7, 2021
Messages
45
Wow, that's the way I think! Don't know if you know that in Italy on an electricity bill of 100€ the electricity cost is around 25€ and all the rest is taxes... :cautious:

But in any case I don't want to pay for electricity if solar can do it for me yeahh! :giggle:
With our new President we about to get some hefty taxes. A Kilowatthour here is 26 cents and rising. I just leased a Nissan Leaf and it is a must that I charge it with solar or I'm going to be living in a Leaf.
 

basjes

New member
Joined
Apr 29, 2021
Messages
2
Hi Roman, I'm interested in testing your "sandwich", could you please contact me?
 
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