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BTcap lithium ion hybrid supercapacitor

FyKnight

New Member
Joined
Feb 1, 2021
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39
Hi I found these seemingly amazing 2200 mAh hybrid "capacitors" on Alibaba, called "BTcap 21700 Flash Charge Battery"

Does anyone have an opinions or experience with them? They'd be perfect for my solar-powered project that needs to output a few hundred watts for about a minute. Normally to do that you'd need a few hundred watt hours of battery to get the rate something near 1C. With these guys I just need 2 or 3 of them!

They have a continuous discharge rate of 60 A which is about 30C. Standard charge and discharge are great too at 22 A = 10C.
ESR is really small (11 mOhm), cycle life is huge (30k fast, 50k standard). Their self-discharge is even minimal compared to regular EDLC supercapacitors (see graphs). The voltage range (2.5 V to 4.2 V) is not too far off regular BMS kits.

So... what am I missing? What's the catch? Google can't find me anyone talking about them. Thanks!
 
My order came in last week and I'm going to test them this coming week. I actually received the 2500 mAh version, which is rated up to 70 A discharge. According to the (very friendly) supplier they have had a lot of interest in them. I'll post my results here if there's interest.
 
My order came in last week and I'm going to test them this coming week. I actually received the 2500 mAh version, which is rated up to 70 A discharge. According to the (very friendly) supplier they have had a lot of interest in them. I'll post my results here if there's interest.
I'm really interested as I think I might be purchasing two 3.55 Sirius soon. Still waiting to hear from Sirius as to their components.
 
My order came in last week and I'm going to test them this coming week. I actually received the 2500 mAh version, which is rated up to 70 A discharge. According to the (very friendly) supplier they have had a lot of interest in them. I'll post my results here if there's interest.
How did they perform? By my math they should be more like 250 mah not 2500-typical Chinese fake performance markup
 
I only tested them recently and haven't tried up to the specs, just what I need for my application. Discharging at 26 A for 30 seconds works fine, as does continuous charging and discharging at around 8 A, over a couple of hours (this is all I need). I haven't taken them below 2.9 V nor above 4 V per cell. I'm pretty happy in fact.. the cells don't even get warm. I've been checking them very frequently!

I'm not using a BMS (yet), and have noted a decent variance in cell capacity. After a couple of months (ok more like 6 months) on the shelf they had capacities of 3.69 - 3.75 V each. Discharging them in 14s strings to around 3.0 V resulted in most cells sitting within 40 mV of each other, though there were one or two outliers per string at 100 mV lower than the rest. Recharging the string brought them all back to the same 3.75 V level, which is nice.

I haven't tried to measure capacity directly but run-time is in line with my expectations, certainly not more than a factor of 2 out. (e.g. charging at 8 A for ~5 mins brings voltage up from 3.6 V to 3.8 V)
 
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