Richard Pfiffner wrote on 6/3/2020 5:35 AM:
On Tuesday, June 2, 2020 at 10:09:21 AM UTC-7, 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. 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. Richard Pfiffner one time was testing batteries, and his
vendor shipped 24 volt chargers accidentally for 12 volt batteries. All
the white stuff leaked out of the battery. 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. A 15-20 AH battery intended as
a starter battery can easily find it's way into other applications. 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. Did it have a BMS? 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.
Eric,
I don't know about the BMS. All I know is Bioenno supplied the batteries with a 24 volt charger. When the batteries were charged they were destroyed. Bioenno replaced the batteries and chargers although it took a long time to get the replacements.
Richard
I emailed this question to Bioenno:
"Does the BLF-1220AS protect itself if a charger for a 24 volt Bioenno is
connected to it?"
Their answer:
"The BLF-1220AS can only accept a charging voltage from 13.8VDC to 15.3VDC. If
you exceed 15.3VDC, the BMS will trip and the battery shuts off. However, high
voltage should not be left attached continuously to the battery which can cause
permanent damage to the BMS/cells. If the voltage is less than 13.8VDC, the
battery will charge, but not be 100% charged.
-Kevin"
I don't consider 24 volts (or the likely charging voltage of 28 volts) to be a
"high voltage", but it sounds like leaving a 24 volt charger applied to a 12 volt
Bioenno battery will damage the battery after a while. So, while the battery does
protect itself in the short term, neither the battery nor the charger indicate
that there is a problem. Since the battery can be hidden from view, I think the
charger should be smart enough to indicate it's been connected to the wrong
battery AND it should disconnect itself. The Bioenno charger does neither,
unfortunately.
If you do connect the 24 volt charger to the 12 volt battery, the LED indicator
(all it has) will show GREEN, indicating the battery is fully charged, instead of
RED, your expectation to indicate it is charging. Too subtle, I think.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1