K2 battery endurance

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 not sure how old they are but they're at least 3 years old as this is my 3rd season with the ship. Yesterday, after a little over 5 hours I got a low battery warning with the batteries at 11.3 volts. I had all the above avionics on but did virtually no transmitting on the com, just listening. They were fully charged at takeoff.

I'm not sure if this normal endurance for these batteries or not, any advice would be appreciated.

Thanks,

John S.

I run a similar system and I don't think you have a problem. Charge them for a couple of days and go fly.

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"

On Friday, May 8, 2020 at 6:37:33 PM UTC-7, Piet Barber wrote:
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"

Read before you comment on how to charge a LiFEPO4 Battery

https://www.planetanalog.com/how-to-...le-batteries/#

Richard
www.craggyaero.com

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

On Friday, May 8, 2020 at 8:29:23 PM UTC-7, Eric Greenwell wrote:
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

One thing that comes to mind is how did you know that the batteries were fully charged? The charger may have shut off for some unknown reason. I never fully trust battery chargers and double-check their operation with a battery monitor:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Most of the time the charger and the monitor agree within the margin of error, but occasionally there is a significant disagreement.

And, speaking of battery chargers, which charger are you using?

Tom

after a little over 5 hours I got a low battery warning with the batteries at 11.3 volts.

It might be worth checking at the batt terminals just to make sure something didn't get loose.

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 not sure how old they are but they're at least 3 years old as this is my 3rd season with the ship. Yesterday, after a little over 5 hours I got a low battery warning with the batteries at 11.3 volts. I had all the above avionics on but did virtually no transmitting on the com, just listening. They were fully charged at takeoff.

I'm not sure if this normal endurance for these batteries or not, any advice would be appreciated.

Thanks,

John S.

Hi,

Thanks for all the information, I have some good ideas to work from now. I use the proper K2 charger and usually charge the batteries overnight. Temperature may have been a player too as it was -17C at cloud base (over 10,000' very unusual for the Northeast) and the batteries are behind the rear bulkhead on a Ventus so I'm sure they were cold soaked.

Thanks again for all the info.

One of my early K2's experienced a cell failure which dropped that battery's voltage output and lowered it's capacity. I run two batteries in parallel and had an experience like yours. Individual testing of each found the bad battery. Replacement is the only fix for this.

Battery testing can be done pretty easily and low tech. Using a voltmeter and 12V side marker lights from your local tractor supply. , 2-4 of the side marker lights should approximate your gliders normal electrical load. Plug them into the battery then check and record the voltage every half hour until it drops to 11.5V.

You can measure amperage with most multi-meters, just be careful to switch the leads back to voltage measurement. The cheap meters are not fused. Had a guy blow one up checking 480V with an un-fused meter set to measure current. It can cause serious injury, so exercise caution. The batteries we use in sailplanes can deliver enough energy to melt things if shorted out, so respect that potential when dealing with them. We had to evacuate a 300,000 SQFT manufacturing facility once because a technician shorted out a single lithium Ion battery cell in his test stand, The smoke from off-gassing was impressive.

SF

Testing is always good, but John has a very reasonable suspicion the
problem was due to cold soaking the batteries. LFP's really don't like
the cold, and can even be damaged if charged below freezing. Maybe he
had a temporary loss of capacity that wouldn't show up under room temp
testing.




On 5/30/20 8:50 AM, SF wrote:
One of my early K2's experienced a cell failure which dropped that battery's voltage output and lowered it's capacity. I run two batteries in parallel and had an experience like yours. Individual testing of each found the bad battery. Replacement is the only fix for this.

Battery testing can be done pretty easily and low tech. Using a voltmeter and 12V side marker lights from your local tractor supply. , 2-4 of the side marker lights should approximate your gliders normal electrical load. Plug them into the battery then check and record the voltage every half hour until it drops to 11.5V.

You can measure amperage with most multi-meters, just be careful to switch the leads back to voltage measurement. The cheap meters are not fused. Had a guy blow one up checking 480V with an un-fused meter set to measure current. It can cause serious injury, so exercise caution. The batteries we use in sailplanes can deliver enough energy to melt things if shorted out, so respect that potential when dealing with them. We had to evacuate a 300,000 SQFT manufacturing facility once because a technician shorted out a single lithium Ion battery cell in his test stand, The smoke from off-gassing was impressive.

SF

On Saturday, May 30, 2020 at 5:47:01 PM UTC-4, kinsell wrote:
Testing is always good, but John has a very reasonable suspicion the
problem was due to cold soaking the batteries. LFP's really don't like
the cold, and can even be damaged if charged below freezing. Maybe he
had a temporary loss of capacity that wouldn't show up under room temp
testing.

LFPs don't like to be charged while cold (below the freezing point of water is the rule of thumb, even though they are not made of water). But they discharge just fine while (reasonably) cold. Their capacity while cold doesn't suffer anything like the way SLAs capacity does.