Has anyone tried using an i3 battery pack with a more powerful motor?
Spec sheet seems to indicate 417A for 5seconds (around 150kW for a full voltage pack) which matches well for the i3's maximum 137kw peak
What's likely to be the outcome of pushing further? Hoping to drive ~220kw into a tesla SDU for periods of around 5 seconds. This is around 30% over spec.
cloudy wrote: ↑Mon Jun 01, 2020 3:43 pm
What's likely to be the outcome of pushing further?
Voltage sag and heat are the most likely outcomes from short duration excessive current draw.
Why not test a single cell to find out for sure?
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Lets take your arbitrary 220kw, the joke is this not drawn till you hit field weakening thus max power, but lets assume its a constant draw for the sake of making things easier.
This is a real crude graph of what happens, now the thing to keep in mind is that your whole system will have a voltage drop so the actual delivered current to achieve 220Kw at the motor input would be upto 20-30% higher due to the voltage sagging by the same amount across all other connections.
However looking at the cell specs you are well clear of their 2.7V limit over most of the voltage range.
Thankyou - that's super helpful, I guess the only real test is to try it and watch for sag/heat - not easy to get hold of single cells due to the construction of the busbars, but could test a single pack...
cloudy wrote: ↑Mon Jun 01, 2020 7:30 pm
Thankyou - that's super helpful, I guess the only real test is to try it and watch for sag/heat - not easy to get hold of single cells due to the construction of the busbars, but could test a single pack...
The biggest issue is how to control that 500-800 Amps and log data. As you could use the good old rebar in water with jumper cable trick but its not really repeatable or controlled.
My plan for stress testing the eig c20 cells is to use the isabellenhütte shunt and a bunch of contactors that I can program to open different value high power resistors. I have 100w rated 0R2 resistors and all the stuff already just need to find the time to build the bench.
tom91 wrote: ↑Mon Jun 01, 2020 7:46 pm
The biggest issue is how to control that 500-800 Amps and log data. As you could use the good old rebar in water with jumper cable trick but its not really repeatable or controlled.
The carbon piles used in lead acid load testers can often be broken down into their individual elements. We had one that contained five discs that was pretty stable if you restricted the tests to 20 seconds to prevent excess heat impacting the measurements. iirc it cost five quid on ebay and was rated at 1000A.
If you use an ISA shunt I think you can measure battery current and voltage accurately enough to answers the OP's question
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i3 (94Ah Samsung SDI) pulse currents?
