LiFePO4 Batteries

On Monday, April 28, 2014 9:16:34 AM UTC-7, Andrew wrote:
I recently got the Starkpower 12V 9Ah battery from Knauff. I've put it through one test charge/discharge cycle so far. I found...



1. It took about 10Ah when I charged it from 9V resting to full voltage (14.4V while charging for a 4 cell LiFeSO4). I imagine the advertised 9Ah rating accounts for aging after many load cycles.



2. It supplies 13.0V to 13.2V for a very long time under a 0.5A load. I'd like to see how it does under a 2A to 4A load.



3. The built-in Battery Management System (BMS) does terminate any charging attempt past 14.6V



4. The BMS does not terminate discharging at 10.5V as Starkpower's website advertises. I only brought the pack down to 9V, but other sources indicate the BMS terminates discharge at 8.2V.



On Monday, April 28, 2014 10:55:16 AM UTC-4, vontresc wrote:

So I am in the market for a new battery for my Libelle. I was thinking it might be time to upgrade to a LiFePO4 battery.







Any recommendations/reviews from the community? I've seen people using the K2 and Stark Power batteries. Any preference between the two?







Thanks







Peter

I did a discharge test on the Stark Power 12v 9Ah. 1.4 amp draw got me 280 minutes.

The lead acid 12v 9Ah at 1.4amp got me 150 to 180 minutes.

The other great advantage to the LiFePO4 is if you drop one on your foot it doesn't hurt.

Richard
www.craggyareo.com

This test of actual battery performance is fantastic.
Now, can someone do the same test of each of the batteries that are for sale?
What a great project for SSA !!! This would be a real service to all glider pilots.

On Saturday, May 17, 2014 7:09:38 AM UTC-7, Richard wrote:
On Monday, April 28, 2014 9:16:34 AM UTC-7, Andrew wrote:

I recently got the Starkpower 12V 9Ah battery from Knauff. I've put it through one test charge/discharge cycle so far. I found...







1. It took about 10Ah when I charged it from 9V resting to full voltage (14.4V while charging for a 4 cell LiFeSO4). I imagine the advertised 9Ah rating accounts for aging after many load cycles.







2. It supplies 13.0V to 13.2V for a very long time under a 0.5A load. I'd like to see how it does under a 2A to 4A load.







3. The built-in Battery Management System (BMS) does terminate any charging attempt past 14.6V







4. The BMS does not terminate discharging at 10.5V as Starkpower's website advertises. I only brought the pack down to 9V, but other sources indicate the BMS terminates discharge at 8.2V.







On Monday, April 28, 2014 10:55:16 AM UTC-4, vontresc wrote:



So I am in the market for a new battery for my Libelle. I was thinking it might be time to upgrade to a LiFePO4 battery.















Any recommendations/reviews from the community? I've seen people using the K2 and Stark Power batteries. Any preference between the two?















Thanks















Peter



I did a discharge test on the Stark Power 12v 9Ah. 1.4 amp draw got me 280 minutes.



The lead acid 12v 9Ah at 1.4amp got me 150 to 180 minutes.



The other great advantage to the LiFePO4 is if you drop one on your foot it doesn't hurt.



Richard

www.craggyareo.com

Meaning: neither came anywhere close to their 9AH spec, at least at this discharge rate. Lead acid usually spec'd at the 20 hour discharge, not sure if there is a standard for LiFe. Peukert is alive and well?

So from that test we could conclude that they both sucked, but the LiFe sucked less.....


I just got a Stark Power 12AH, seems to hold the voltage up higher always, and last longer than the 12 AH AGM that it replaced.

As Jon says, it is always good to have a look at the spec.
Taking the PowerSonic PS1290 spec as an example
http://powersonic.com/images/powerso...10-PS-1290.pdf

At the 5-hour discharge current of 1.44A, the specified capacity for this PS1290 9Ah SLA battery is 7.2Ah.
Richard measured 180 min = 3 hours @ 1.4 Amps = 4.2Ah.
4.2Ah of remaining capacity out of the specified 7.2 Ah means that this battery has deteriorated to 4.2/7.2 = 58% of the original capacity.
If this is a used battery, with a number of deep-discharge cycles, this deterioration is quite normal.
If this a new SLA Lead Acid battery, this is a very poor specimen.

Any rechargeable battery is a consumable.
The capacity decreases with each and every discharge-charge cycle.
The use case has a big influence on the rate of deterioration, e.g: shallow vs. deep discharge.
Looking further down the spec sheet of the Lead Acid battery, in the "life Characteristics in cyclic use" graph, you can see that this battery has a life expectancy of only about 200 deep-discharge cycles (100% discharge) and about 1100 cycles of shallow (30%) discharge.
This is why I run my batteries in parallel.

Similar calculations can be made for the LiFePO4s. I have no specification for this chemistry.
Assuming that the LiFePO4 9Ah battery derates similarly to 7.2Ah at the 5-hour current draw, Richard's measurement would indicate:
280 minutes = 4.66 hours @ 1.4 Amps = 6.53Ah or 6.53/7.2 = 91% of capacity.
Not too bad.

As said, I have all 3 of my fused SLA batteries switched in parallel. I am very comfortable with that (and no, one battery does not charge the other !)
As far as I know, the LiFePO4 packaged batteries have build-in discharge and charge protection circuits. With those, I would need to understand the spec in much detail before I would be comfortable switching them in parallel.
3U

On Saturday, May 17, 2014 10:09:38 AM UTC-4, Richard wrote:

I did a discharge test on the Stark Power 12v 9Ah. 1.4 amp draw got me 280 minutes.



Most of these LFP batteries come up right to, or just over manufacturer's spec. For example, I bought a bioenno 12AH battery that I tested at 12.3 AH using a fancy RC battery charger with an integrating discharge function.

T8

On Saturday, May 17, 2014 2:10:06 PM UTC-7, wrote:
As Jon says, it is always good to have a look at the spec.

Taking the PowerSonic PS1290 spec as an example

http://powersonic.com/images/powerso...10-PS-1290.pdf



At the 5-hour discharge current of 1.44A, the specified capacity for this PS1290 9Ah SLA battery is 7.2Ah.

Richard measured 180 min = 3 hours @ 1.4 Amps = 4.2Ah.

4.2Ah of remaining capacity out of the specified 7.2 Ah means that this battery has deteriorated to 4.2/7.2 = 58% of the original capacity.

If this is a used battery, with a number of deep-discharge cycles, this deterioration is quite normal.

If this a new SLA Lead Acid battery, this is a very poor specimen.



Any rechargeable battery is a consumable.

The capacity decreases with each and every discharge-charge cycle.

The use case has a big influence on the rate of deterioration, e.g: shallow vs. deep discharge.

Looking further down the spec sheet of the Lead Acid battery, in the "life Characteristics in cyclic use" graph, you can see that this battery has a life expectancy of only about 200 deep-discharge cycles (100% discharge) and about 1100 cycles of shallow (30%) discharge.

This is why I run my batteries in parallel.



Similar calculations can be made for the LiFePO4s. I have no specification for this chemistry.

Assuming that the LiFePO4 9Ah battery derates similarly to 7.2Ah at the 5-hour current draw, Richard's measurement would indicate:

280 minutes = 4.66 hours @ 1.4 Amps = 6.53Ah or 6.53/7.2 = 91% of capacity.

Not too bad.



As said, I have all 3 of my fused SLA batteries switched in parallel. I am very comfortable with that (and no, one battery does not charge the other !)

As far as I know, the LiFePO4 packaged batteries have build-in discharge and charge protection circuits. With those, I would need to understand the spec in much detail before I would be comfortable switching them in parallel.

3U

I think more relevant to gliders is how deep the battery can usefully be discharged. SLA specs usually regard completely discharged as 10.5V. Modern electronics have DC-DC power supplies inside, as the input supply voltage deteriorates the current consumption goes UP, in order to supply the same currents at 5 or 3.3V to the electronics internally. Also when you hit the transmit button to announce your pattern at the end of the day, in my glider at least the current goes from about 0.6A to 1.6A. Add another 20% due to low voltage and I am trying to draw 2 amps from a mostly depleted battery, dropping the voltage further.

I don't care if I only get 200 deep discharge cycles from a $30 SLA - that represents many years of flying, the battery will decay from age before that. But the LiFe will hold its output voltage up higher when it is deeply discharged, according to Starkpower well above 12V even at 90% discharge. Another potential advantage of LiFe is that they need not be recharged fully immediately after use as they do not sulfate. Most Li battery vendors seem to recommend leaving them in a partially charged state (50-80%) for storage. So if you forget to charge it after the weekend's flying, you will do less damage to it.

LiFePO4 batteries keep going so long that you'll rarely see a discharge below 12V.
They behave fine in parallel, charge and discharge.
They hold a charge for ages, so those who put their glider away for the winter could fly months later on the old charge.... Not that anybody ever forget to charge batteries!
There's no need to keep the panel off after preflight. No more waiting to turn the transponder on until hooking up the rope. For those with bluetooth devices, no more "it won't connect to the logger" while taking up slack.
Dare I say no more excuse to not have a transponder?
WARNING: These batteries cost more than a roll of cheap yellow electrical tape on Amazon.
Jim
(You Only Live Once department)

JS wrote:
LiFePO4 batteries keep going so long that you'll rarely see a discharge below 12V.
They behave fine in parallel, charge and discharge.
They hold a charge for ages, so those who put their glider away for the
winter could fly months later on the old charge.... Not that anybody ever
forget to charge batteries!
There's no need to keep the panel off after preflight. No more waiting to
turn the transponder on until hooking up the rope. For those with
bluetooth devices, no more "it won't connect to the logger" while taking up slack.
Dare I say no more excuse to not have a transponder?
WARNING: These batteries cost more than a roll of cheap yellow electrical tape on Amazon.
Jim
(You Only Live Once department)

Update: bought one if the stark power batteries from Tom Knauff, and so far
I am impressed. After three hours battery voltage was still 12.7 or better.
Also I like the fact that it's nice and light should I ever drop it on my
foot ;-)

Pete

On Wednesday, May 21, 2014 12:08:47 PM UTC-7, vontresc wrote:
JS wrote:

LiFePO4 batteries keep going so long that you'll rarely see a discharge below 12V.

They behave fine in parallel, charge and discharge.

They hold a charge for ages, so those who put their glider away for the

winter could fly months later on the old charge.... Not that anybody ever

forget to charge batteries!

There's no need to keep the panel off after preflight. No more waiting to

turn the transponder on until hooking up the rope. For those with

bluetooth devices, no more "it won't connect to the logger" while taking up slack.

Dare I say no more excuse to not have a transponder?

WARNING: These batteries cost more than a roll of cheap yellow electrical tape on Amazon.

Jim

(You Only Live Once department)



Update: bought one if the stark power batteries from Tom Knauff, and so far

I am impressed. After three hours battery voltage was still 12.7 or better.

I bought a 10 Ah Tenergy from Amazon.com and it included a free smart
charger. It's a direct fit for the 9 Ah lead acid battery in the
baggage compartment of my LAK-17a and much lighter. Lasts a long time, too!


Dan Marotta 5J
On 5/21/2014 3:33 PM, jfitch wrote:
On Wednesday, May 21, 2014 12:08:47 PM UTC-7, vontresc wrote:
JS wrote:

LiFePO4 batteries keep going so long that you'll rarely see a discharge below 12V.
They behave fine in parallel, charge and discharge.
They hold a charge for ages, so those who put their glider away for the
winter could fly months later on the old charge.... Not that anybody ever
forget to charge batteries!
There's no need to keep the panel off after preflight. No more waiting to
turn the transponder on until hooking up the rope. For those with
bluetooth devices, no more "it won't connect to the logger" while taking up slack.
Dare I say no more excuse to not have a transponder?
WARNING: These batteries cost more than a roll of cheap yellow electrical tape on Amazon.
Jim
(You Only Live Once department)


Update: bought one if the stark power batteries from Tom Knauff, and so far

I am impressed. After three hours battery voltage was still 12.7 or better.

Also I like the fact that it's nice and light should I ever drop it on my

foot ;-)



Pete
I have a new Starkpower 12 AH. I just ran it down to see how long it would last, also when it goes flat how suddenly. Powering a Butterfly vario, PowerFlarm, Trig 21, Dittel radio, Ilec spare vario, iPhone 5S running iGlide. Draw was bout 0.9A until the iPhone is charged, then drops to around 0.7A with no radio transmission and infrequent transponder hits. Starts out at 13.1V, then quickly settles to 12.9V. At about hour 11, down to 12.5V. From there to hour 13 a more steady decline to 11.5V. I shut it off at 14 hours, about 11.2V. That's longer than my usual day flying! I'm not sure how much longer until the 9.5V shutoff, probably not much as the voltage decline was accelerating. Anyway, plenty of life, plenty of warning when it is going soft.