Thanks. Do these IR readings from my Orion look problematic? It's snowing here so I am going to fire up the genset and I'll post again when cell 16 is over 3.6v
Best way to burn some juice of a couple runners?
- Thread starter hammick
- Start date
Luthj what do you mean by 20% or 50%. My BMS shows IR in mOhms
curiouscarbon
Science Penguin
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they might have meant % variance between mOhm values
Your 0.1-0.13 mOhm range is probably acceptable for your application. The cells at 0.17-0.19 may have poor connections.
By percentages I was talking about the total difference between the highest and lowest cell. IR varies with temp and SOC, so you are mostly concerned with how even the cells are.
Note that these values are sensitive to SOC at the top/bottom. So badly out of balance cells can have very different IR readings at that level. As long as you are between 3.0-3.3V, this shouldn't be a major factor.
Once you get the cells balance within 10mv, apply a load to the pack. I would guess the higher IR cells will experience a higher voltage drop than the others, which confirms a resistance variance on those cells.
By percentages I was talking about the total difference between the highest and lowest cell. IR varies with temp and SOC, so you are mostly concerned with how even the cells are.
Note that these values are sensitive to SOC at the top/bottom. So badly out of balance cells can have very different IR readings at that level. As long as you are between 3.0-3.3V, this shouldn't be a major factor.
Once you get the cells balance within 10mv, apply a load to the pack. I would guess the higher IR cells will experience a higher voltage drop than the others, which confirms a resistance variance on those cells.
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Ampster
Renewable Energy Hobbyist
I am on my phone fo a few hours so can't compare easily. Cell 13 shows 0.00 but maybe aberation. I would also look at the two mentioned above. Maybe after cells get balanced. 54.5 CV setting may avoid cells running.
curiouscarbon
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Cell 13
0.080
??(?)
0.080
??(?)
Thanks for all the help! I looked at my fancy (and expensive) braided buss bars and it appears that when they punch the holes it deforms the surface on some of them. I removed the bars that connect to cells 16 and 1 (my runner cells) and hammered them flat and gave a good polishing with 1500 grit sandpaper. That seems to have fixed those two cells from running. I'm going to get some 600 grit sanding blocks so I can do a better job. I will also hammer the other buss bars that are on cells with higher resistance.
Tomorrow and Wed look to be full sun. I'm going to set the CC to 54.5 and let the BMS do it's job. Thanks.
Did you try the 100w bulb? If so, what gauge wire did you use? My 16th cell is still running way high and I need to figure a way to burn some watts off tomorrow. Thanks.
Measure the resistance and use something like https://ohmslawcalculator.com/ohms-law-calculator to figure out the draw and then use appropriately-sized cable. Resistance will increase as the filament gets hot, but this is a bulb designed to draw ~1 amp at 120 volts while hot and you're using 3.2 volts so it's not going to be much.
So if I use 6ga wire can I leave it connected and watch the voltages on my Orion BMS and when the voltage of the 16th cell drops say to the middle of the average cell voltage call it good, start charging and see the results? Any reason I need to isolate the cell? If I do that I can't monitor on the Orion utility.
Thanks!
Ampster
Renewable Energy Hobbyist
No need to isolate the cell. The best place to reduce the voltage is near the top if you can because up there the voltage will be closer to SOC.
BarkingSpider
Carbon Lifeform
Hi, I tried the 100 incandesant light bulb, it works, but very slowly, if you want to lower your cell voltage 100x faster, use this, It lowers the voltage very quickly, and is much safer.
Simply short the two poles of your battery through this resistor, You may need to add some thick wire to make it reach, 10 gauge would be fine. You could also use car jumper leads.
As a safety test, I hold on to it, when it gets too hot to hold any longer, I disconect it from the battery. Its a $10 200W heavy duty resistor.
KKmoon RX24 200W 1ohm / 2ohm / 4ohm / 8ohm / 10ohm Aluminum Shell Resistance Metal Wirewound Wire Wound Winding Resistor Dummy Road - - Amazon.com
KKmoon RX24 200W 1ohm / 2ohm / 4ohm / 8ohm / 10ohm Aluminum Shell Resistance Metal Wirewound Wire Wound Winding Resistor Dummy Road - - Amazon.com
www.amazon.com
I use these resistors all the time to avoid sparks, anytime you connect your inverter, BMS or similar to your battery, Use this inline on the end of the wire first. Just a 1 second touch is all you need, then connect the leads as normal. The polarity is not important. No more sparks!
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Thanks. I only have a few days to get this done so I'll have to get the resistor for the next trip up here. Can you tell me what you mean by slow for the light bulb? Hours or days?
Ampster
Renewable Energy Hobbyist
It depends on resistance. At 3.2 volts one Ohm will pull 3.2 Amps and get hot.
I= V/R
At that rate it might only take 30 minutes.
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BarkingSpider
Carbon Lifeform
OK, I tried fruit, vegetables and other stuff for home made resistors, then realised I already have big resistors all over my house And they work great.
Simply connect your batteries to the AC leads on your
1) Soldering iron (200 ohms)
2) Hot glue gun (80 ohms)
3) Iron
4) Electric heater
etc etc, the voltage dropped fastest with my hot glue gun. I used 2 x 1ft 14 gauge wires with crocodile clips on to connect the battery. So any old wires around the house will work fine.
The higher the voltage you use, the faster it works, so put your high voltage cells in series to bulk reduce the power at first, then do one at a time when they are close to the voltage you want.
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Interesting. I only have one cell that I need to drain. What size wire do you recommend if I use our iron?
