izeman said:
amberwolf said:
A123 20AHr Pouch Cell Battery Build & Info Thread
- Thread starter bigmoose
- Start date
izeman
1 GW
Sorry I read that o.c., but light bulbs don't have the correct ohm. Do they? I need to discharge a single cell which is 3.3v. So I need a resistor of 0.1 ohm for 30a current. A light bulb with 12v will not even glow.
parallel enough and it will work. meausre curent drwa of one and caclulate how many u need.
ev99saturn
100 µW
- Joined
- Nov 21, 2011
- Messages
- 8
You can use a length of copper wire as a resistive load. 12 gauge wire is is 1.588 ohms per 1000 feet, so 69 feet of it would draw about 30 amps at 3.3V, and of course a bit less with the voltage sag that current level. Shorter lengths will heat up quickly. To pull more current, use bare wire and submerse it in water to dissipate heat, don't let any it short to itself.
The attached picture shows about 30 ft of 12 ga in a coil that was lowered in water to load test pouches. For a single cell it pulls about 60 amps. Use a separate switch to make & break the connection so you don't arc at the cell tabs.
-Wayne
The attached picture shows about 30 ft of 12 ga in a coil that was lowered in water to load test pouches. For a single cell it pulls about 60 amps. Use a separate switch to make & break the connection so you don't arc at the cell tabs.
-Wayne
izeman said:
999zip999
100 TW
What size pack are you going to make ?
999zip999
100 TW
i charge on my hyperion and it stops at 3.59v but rests at 3.51v ect. Yes i could run it up to 3.8v and take off for the ah reading and wouldn't hurt the cell. So ?
ev99saturn
100 µW
- Joined
- Nov 21, 2011
- Messages
- 8
Not sure if your question is for izeman or me, but I am building 12S4P packs.
999zip999 said:
dnmun
1 PW
why do you have to discharge a cell at 30A?
999zip999
100 TW
ev99saturn 12s4p are these sub- packs for a car ? And yes what is izeman planing to do with his ?
ev99saturn
100 µW
- Joined
- Nov 21, 2011
- Messages
- 8
Yes, they are packs for a car. There will be 8 total, I am building #6 at the moment. The car is quick with the first 3 installed. These cells really deliver.
999zip999 said:
dnmun
1 PW
ohhh, dream car. i saw a S2000 roadster today in traffic too, some designs are classics.
izeman
1 GW
atm i can only discharge at 6a. which gives me high 19ah+. but to test those cells under real live conditions i need 30a load to see sag and how much they will deliver. as i wrote internal resistance is about 5-10 times higher then nominal. so i expect some sag - and now i want to be sure what will happen, or i will have to open a paypal case.dnmun said:
izeman
1 GW
in case you asked me: 24s1p for an ebike.999zip999 said:
izeman
1 GW
ordered this now: 100w 0.1ohm. mounted to a cpu heatsink with cooler, this will be a nice 30a load. 
http://www.conrad.at/ce/de/product/422894/ATE-Electronics-100-Watt-Hochlast-Drahtwiderstand-axial-bedrahtet-Hochlast-01-100-W-5-
http://www.conrad.at/ce/de/product/422894/ATE-Electronics-100-Watt-Hochlast-Drahtwiderstand-axial-bedrahtet-Hochlast-01-100-W-5-
izeman
1 GW
did you measure resistance of your whole battery? i found out that w/o enough pressure between the tabs, resistance of the whole battery may double. these cotter pins seem to be pushed over the two tabs, and no other pressure than that correct? what current to you pull from that pack? other than my thoughts this is very nicely made. looking good
edit: sorry. i saw this discussed earlier before. nether the less i'd like to see the resistance of the whole pack.
edit: sorry. i saw this discussed earlier before. nether the less i'd like to see the resistance of the whole pack.
I measured connections, not whole battery, 0.6-0.8mOm, read about it in first my build link.izeman said:
BMS is 50A continuously, 100A peak. I guess this cotter pin connections be good up to 100-150A
Edit: I guess 16S battery without BMS is about 40-50mOm, I will measure for you later
sendler2112
100 kW
Beautiful build. McMaster-Carr has brass cotter pins.
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http://www.mcmaster.com/#catalog/118/3356/=kvxvzv
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Are the main wires soldered onto a pin also?
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http://www.mcmaster.com/#catalog/118/3356/=kvxvzv
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Are the main wires soldered onto a pin also?
izeman
1 GW
thanks. 50mOhm would be a great value.evb said:izeman said:.. I guess 16S battery without BMS is about 40-50mOm, I will measure for you later
megacycle
100 kW
izeman said:ordered this now: 100w 0.1ohm. mounted to a cpu heatsink with cooler, this will be a nice 30a load.
http://www.conrad.at/ce/de/product/422894/ATE-Electronics-100-Watt-Hochlast-Drahtwiderstand-axial-bedrahtet-Hochlast-01-100-W-5-
Light globes and resistors they've all got their temp coefficients to take into account.
They warm up resistance changes, if your monitoring your current it will alter with the resistor temperature which will be affected by an Isqd driven by a dropping terminal voltage
I think your resistor spec is here http://www.brose-elektronik.de/english/bricks/ATE_WI_RB_eng.html.
Basically you'll have to log a varying current for Ah, for accurate.
Have fun and luck, hope your cells are good.
I'll look how the pro's measure the Ah, I've seen the tests and results before just can't remember how :?
izeman
1 GW
megacycle said:izeman said:ordered this now: 100w 0.1ohm. mounted to a cpu heatsink with cooler, this will be a nice 30a load.
http://www.conrad.at/ce/de/product/422894/ATE-Electronics-100-Watt-Hochlast-Drahtwiderstand-axial-bedrahtet-Hochlast-01-100-W-5-
Light globes and resistors they've all got their temp coefficients to take into account.
They warm up resistance changes, if your monitoring your current it will alter with the resistor temperature which will be affected by an Isqd driven by a dropping terminal voltage
I think your resistor spec is here http://www.brose-elektronik.de/english/bricks/ATE_WI_RB_eng.html.
Basically you'll have to log a varying current for Ah, for accurate.
Have fun and luck, hope your cells are good.
I'll look how the pro's measure the Ah, I've seen the tests and results before just can't remember how :?
sure. i know that resistance changes with temperature, and that those mini resistors need to be cooled. resistance does change, but it's still good enough to produce a high enough load. i don't care if it's 25a or 35a. anything in that range is ok, as it's about the same current my bike will need.
I had some tests an A123 cell with this (a set of resistors), 120A is ok for discharge 20Ah cellmegacycle said:izeman said:ordered this now: 100w 0.1ohm. mounted to a cpu heatsink with cooler, this will be a nice 30a load.
http://www.conrad.at/ce/de/product/422894/ATE-Electronics-100-Watt-Hochlast-Drahtwiderstand-axial-bedrahtet-Hochlast-01-100-W-5-
izeman
1 GW
looks nice i will go for one 0.1ohm resistor for now, and a big cpu cooler. to calculate R(int) i can just out another (bigger) resistor in parallel, therefor changing current, and this will give me V(delta) and I(delta).
i will go for one 0.1ohm resistor for now, and a big cpu cooler. to calculate R(int) i can just out another (bigger) resistor in parallel, therefor changing current, and this will give me V(delta) and I(delta).
megacycle
100 kW
A rehostat in series with a fixed resistor across your power resistor would be good, probably be about $20 US though.