K2 battery endurance

Piet Barber wrote on 5/8/2020 6:37 PM:
On Friday, May 8, 2020 at 3:21:11 PM UTC-4, John Silverberg wrote:
Hi,

I'm hoping someone with experience with K2 batteries can help determine if mine are due for replacement. I have dual K2 batteries wired in parallel to supply avionics power. I have an LX9000, S8 and V8 varios, trig transponder, FLARM core, and becker com radio running off them.

I'm guessing your LX9000 was the one making the complaints about the battery levels, right? Under the Hardware settings, what setting do you have for a battery? The LXNav flight computer doesn't have a "K2 Battery" setting. You should consider going into the setup page, go to hardware, select battery type and select "Custom"
For the battery settings under "Custom" enter the numbers they have printed on the side of the K2 battery. The numbers, as listed on the side of the K2 battery a

Discharge Voltage Cutoff | 10.0V

That number is the absolute bitter end of the battery. I wouldn't recommend discharging your battery all the way to that level! But theoretically you can set the custom settings to that number for the "this whole system could shut off at any moment" value. Try playing around with the numbers to see what you can come up with that seems right.

I remember going into this setting immediately after turning on the system, finding out what the maximum battery charge is.

If you choose one of the other settings like Lead Acid, LiFe or LiPO, the numbers aren't quite right. I have a two seater, and like clockwork, I turn on the system and the passenger says, "Uh, the battery meter is already showing yellow"

At 11.3 volts, the K2 battery should have very little charge left, less than 5%.
The setting is OK as an endpoint, but you need to determine that the 9000 is
measuring the voltage accurately. If not, fix the measurement, or adjust the 9000
alarm point until it alarms when the battery is 11.3-11.7.

But, first measure the capacity of each battery.

--
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