On Tuesday, June 2, 2020 at 2:10:54 PM UTC-4, Dan Marotta wrote:
My Bioenno batteries worked just fine for several years.Â* Just sayin'...

On 6/2/2020 10:26 AM, Richard Pfiffner wrote:
On Monday, June 1, 2020 at 9:46:09 PM UTC-7, kinsell wrote:
On 5/25/20 9:47 PM, Eric Greenwell wrote:
2G wrote on 5/25/2020 2:20 PM:
On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote:
...
The BMS in all LFPs may not have the same functionality regarding
balancing but at the very least they should start/stop accepting
charge appropriately.

It matters not what you think should happen, the truth is not all LFP
batteries have a BMS, and of those that do, not all of them protect from
over and under voltage.
Which LFP batteries don't have a BMS?

Tom
The "powersports" (ie, for engine starting) LFP don't always have a BMS.
A motorglider pilot might be tempted to use one for the engine, for
example.

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.

Richard

--
Dan, 5J

The BMS boards must be changing over the years. I don't expect a company like Bioenno could keep getting the same model BMS over time, even if they tried. Not at a reasonable price anyway. You just get whatever is being churned out in large numbers by a few Chinese factories at the moment. If you want to know whether your specific battery has overvoltage cutoff, try it! Connect to a source with about 15-18 volts, via a resistor to limit the current, and watch the voltage on the battery. It should eventually drop (when cut off at something less than 15V if it's a "12V" LFP), and then the voltage on the resistor should drop to zero (no current). A smart charger such as the iMax B6 can serve for the test, tell it the battery has 5 LFP cells in series ("15V" battery), limit the current to 0.1A, and watch what happens.

Last year I bought an "energized outside" brand (since renamed) LFP battery.. When I charge it with my B6 smart charger, the BMS cuts out at about 14.4V, a bit earlier than the B6 would stop the charge at about 14.6V. As a result, the B6 yells at me about the battery being disconnected, and I can't see what the total amphours charge was. Minor annoyance. At least I know that that battery has a high-voltage cutoff.

And another LFP battery I recently bought, PowerSync brand, shuts itself off when it tries to start up the motor in an electric mower I am using it in.. (Actually two 12V batteries in series.) The initial current surge is somewhat over the 20 amps peak that this battery allows. I solved that problem by adding a longish spool of wire in series with the motor to serve as extra resistance (0.3 ohms) to limit that current surge. And now I know that that BMS really does have an over-current shut-off.