K2 battery endurance

On Thursday, June 4, 2020 at 8:48:04 AM UTC-7, kinsell wrote:
On 6/2/20 11:09 AM, Eric Greenwell wrote:
Richard Pfiffner wrote on 6/2/2020 9:26 AM:
...


StarkPower had a series of batteries aimed at motorcycles that they were
quite open about not having a BMS.Â* Unfortunately they're in Chapter 7
now and the website is gone.

More commonly, some batteries with BMS don't have over and under voltage
protection.Â* Richard Pfiffner one time was testing batteries, and his
vendor shipped 24 volt chargers accidentally for 12 volt batteries.Â* All
the white stuff leaked out of the battery.Â* Some electrical genius on
R.A.S. (don't remember which one) declared that they really had
overvoltage protection, but 24 volts just wasn't enough to trigger it..

One of our fellow Schleicher motorglider pilots had an LFP, left the
transponder on, and ruined the battery.Â* A 15-20 AH battery intended as
a starter battery can easily find it's way into other applications.Â* You
may have read about the ASG 32 mi that got fried when the solar
controller malfunctioned, drained the battery, and got quite hot when
charged from another charger.Â* Did it have a BMS?Â* Doesn't really
matter.

Dave

The problem batteries were Bioenno Batteries.

Were they Bioennos with a BMS that protects against overvoltage? For
example, I use the BLF-1220AS, which ....

"Includes built-in PCM (protection circuit module) which provides
internal cell balancing and management, protection from overcurrent,
undervoltage (overdischarge), overvoltage and short circuiting, and has
integrated charging circuitry "

I haven't tried applying 24 volts to it, but I'd expect it to protect
against 24 VDC being applied to it. I've just emailed Bioenno this
question, but have not heard back.


The glossy brochures say they have short-circuit protection, yet the
actual user manual says "Caution do not short circuit negative and
positive terminals" Apparently the BMS circuit isn't as effective as
they like to make it sound.

Reminds me of a story, one of our motorglider friends was telling me
about his new LFP batteries he installed, and said he felt they were
safe due to the BMS. I asked him if he had ever put a wrench across the
terminals to test the short circuit protection. Turns out he hadn't,
and wasn't about to try that. He's the one that had the transponder
left on accidentally, and ruined the battery due to overdischarge just a
few months later. Apparently his BMS circuit wasn't as effective as he
had been lead to believe. I see a pattern here.

John the OP is using two K2 batteries in parallel. The Bioenno manual
says you can do that with theirs, but you should measure the internal
impedance of the batteries and compensate for any difference with
resistors. It warns of the danger of fire, and says to monitor the
batteries continuously. The user is responsible for any problems due to
parallel or series connections. Not exactly a ringing endorsement for
using them in parallel.

https://cdn.shopify.com/s/files/1/02...3_2019.pdf?209

Would be nice to see what K2 says about that, but they require
registration to see their specs. I'm not saying Bioenno makes a bad
battery, they just seem to be a little more candid than others about the
limitations of their batteries.

-Dave

There is one thing about designing in protection against an unintentional short circuit and an entirely another about doing it deliberately. Of course, Bioenno is going to warn against shorting the battery - this can cause serious injury.

Tom