DIY Electric Car Forums banner

1 - 3 of 3 Posts

·
Registered
Joined
·
66 Posts
Discussion Starter #1
I'm sure this question would have been asked before but i can't for the life of me find the thread.

i was looking into thundersky batteries mainly because there one of the cheapest lithium going around, and the seem to be good quality. with a long life 3000 cycles (10ish years) with a high max current discharge at 20c.

however there seems to be rumors going around that they aren't all that there cracked up to be.:confused:

i was hoping to find out from users of the batteries.

can they withstand 20c discharge?

how long would they last a 10c?
I'm going to use a controller that goes up to 1600amps max and i want 160ah, will they able to put out 1600amps for at least 10 seconds?

do they perform fine at the recommended 3c continues discharge?


according to the stat sheet they should be able to do all this with ease but i wanted to know if anyone out there using thundersky batteries had any independent data.

any help would be greatly appreciated:D
 

·
Registered
Joined
·
2,222 Posts
I've never turned mine up past 5C but I haven't found anything warm. In a vehicle it is very hard to maintain even 3C for long so I'm not sure how to test it except for bench testing. My pack consists of 40, 60 amp hour cells. I'm still working on the rest of the EV so I've only driven it a little bit. It has been on the road since early June, mostly neighborhood testing and a few car shows. I'm working on it again now and hope to put the pack to work next year. I've been working a lot of overtime lately; it seems I either have the money to play with EVs or the time to play with EVs. It is nice to have the money again.

I'm not sure I would actually try 20C with either TS or CALB cells. My pack is staying above 116 volts at 5C (average over 2.9 vpc) and no cell is going below 2.5 volts (BMS didn't go off.)

This is a bit of Otmar's testing of a 90 and 100 amp hour cell. It was posted to the NEDRA list back in October 2009:
I figure the group might like to know about what I did the other
night. I have not seen any high current discharge data on TS cells,
and the TS factory data only shows draws up to 1C, so I figured I'd
do some tests.

First disclaimer: This was a sample size of only 1 and the outside
temperatures were cool at 15 degrees C. This was only a quick "get a
feel for it" test, not exhaustively accurate.

I ran some simple load tests to compare battery sag on both the
TSLFP90AHA and the new TSLFP100AHA in my 914. I ran them up as high
as 1125 amps at which point the cells sagged to 2.022 Volts and 2.069
V respectively. A curve fit through the various data points from
100-1100 Amps slopes at very close to 1 milliohm for either cell.

Before running these tests each new cell was charged at 30A to 4.2V
until current was less than 0.5A. Then it was discharged at 30A to
check capacity (they came in 10-15% over rating) and then recharged
at 3.8V to < 0.2A. Cells where then driven to use up 20-25 AHR and
tests were done with the cells already down 25-50 AHR to insure that
we were on the flat part of the discharge curve. This means the cells
were at approximately 50% SOC.

The test consisted of putting one of each cell in series and adding
them to my normal 240V battery pack. I put a volt meter on each cell
(high quality flukes) and a shunt in the setup for current measuring.
I then put my camera on video mode and drove while filming the
meters. My loads were on repetitively for about 3 to 6 seconds on the
high current pulses and longer on lower draws. Temperatures were low
at 15 degrees C starting temp. The cells gained about 10 degrees C
after resting from 20+ AHR of testing (this amp hour meter caps at
511A, so I don't know the accurate discharge) . There was a definite
trend of less sag as they discharged which I attribute to them
putting out more power as they heated up. The cheap 2/0 welding
cables got hotter than the cells during the short high current
pulses. By the end I could smell the cables and they were getting
floppy. This is not unusual when I race this car. Usually though I
don't have them inside the passenger compartment with me to smell.
The brakes were also smoking a bit by the end of the tests since I
would stand on the brakes at about 40 mph to hold current without
accelerating, no surprise since they were holding back at least 150
HP.
 

·
Registered
Joined
·
66 Posts
Discussion Starter #3
cool thanks for the info, it looks as though thundersky batteries should be able to handle anything i can through at them.

i don't think that i'll take them past 5c very often, i don't think it would be good for the batteries or my own longevity :eek:
 
1 - 3 of 3 Posts
Top