Spring Cleaning and Battery Testing

Each year I like to test my batteries and replace those that do not
have enough capacity for a typical flight of 3-4-ish hours with all
the electronics running. I run two batteries so that removes a worry
about loosing power during a record flight. But how do you perform a
good real world test?

My test is basically connecting a resistive load to the battery,
measure the battery voltage every 10 minutes or so. Then wait for the
battery voltage to drop to 11.5Vdc (an arbitratry but safe value).
Simple.

I create an Excel spreadsheet that explains all this - the testing
that I perform, the test rig that I used and templates for gathering
the data and then graphing the results. See http://aviation.derosaweb.net/#batterytest.

I’d love to hear any comments that you might have. Enjoy.

John DeRosa
Johnatderosaweb.com

On Mar 16, 4:00*pm, ContestID67 wrote:
Each year I like to test my batteries and replace those that do not
have enough capacity for a typical flight of 3-4-ish hours with all
the electronics running. I run two batteries so that removes a worry
about loosing power during a record flight. *But how do you perform a
good real world test?

My test is basically connecting a resistive load to the battery,
measure the battery voltage every 10 minutes or so. *Then wait for the
battery voltage to drop to 11.5Vdc (an arbitratry but safe value).
Simple.

I create an Excel spreadsheet that explains all this - the testing
that I perform, the test rig that I used and templates for gathering
the data and then graphing the results. * Seehttp://aviation.derosaweb.net/#batterytest.

I’d love to hear any comments that you might have. *Enjoy.

John DeRosa
Johnatderosaweb.com

John,
I have used that method and it works well, but.............
First, as I am sure you know, you want a load that is similar to the
real-life load. I use a 12 volt lamp (AKA light bulb) and because I
have a lot of stuff I use a 10 watt lamp to create a 830 mA load which
is about what I pull.

If you are testing every 10 minutes you are working kind of hard. My
battery, a 12120, takes hours to run down.

11.5 volts cut off is way too conservative. The published data curve
for the 12120 ................................wait, I am wrong. I
looked it up and I use 11.8 volts. but 11.5 is fine as well.

I use an Eagle Tree MicroPower V3 logger and get a computer generated
log of the discharge. Then I fly with the logger and get an idea of
my real-world consumption and compare the two. Works great. Others
use a pretty common logger with a built-in load, I prefer the Eagle
Tree because it will log a flight one day and a battery the next.

Do you do your test in cold air to simulate high altitude, or just
room temp?

ps. If you are replacing the 12120 battery look at the 12140 or the
12150. Same size, heavier, and more capacity.

Brian

I know nothing about battery technology. I take my batteries to Battery
Plus, who claims that they can recondition batteries and bring them up to
their proper rating. Sometimes I get a battery back with the indication
that it is at say 113%; if the work brings it back to less than 95% there
is no charge and I throw it away. The cost last year was $5.00 per
battery that came out well.

Am I getting good value?


At 00:40 17 March 2011, brianDG303 wrote:
On Mar 16, 4:00=A0pm, ContestID67 wrote:
Each year I like to test my batteries and replace those that do not
have enough capacity for a typical flight of 3-4-ish hours with all
the electronics running. I run two batteries so that removes a worry
about loosing power during a record flight. =A0But how do you perform
a
good real world test?

My test is basically connecting a resistive load to the battery,
measure the battery voltage every 10 minutes or so. =A0Then wait for
the
battery voltage to drop to 11.5Vdc (an arbitratry but safe value).
Simple.

I create an Excel spreadsheet that explains all this - the testing
that I perform, the test rig that I used and templates for gathering
the data and then graphing the results. =A0
Seehttp://aviation.derosaweb.=
net/#batterytest.

I=92d love to hear any comments that you might have. =A0Enjoy.

John DeRosa
Johnderosaweb.com

John,
I have used that method and it works well, but.............
First, as I am sure you know, you want a load that is similar to the
real-life load. I use a 12 volt lamp (AKA light bulb) and because I
have a lot of stuff I use a 10 watt lamp to create a 830 mA load which
is about what I pull.

If you are testing every 10 minutes you are working kind of hard. My
battery, a 12120, takes hours to run down.

11.5 volts cut off is way too conservative. The published data curve
for the 12120 ................................wait, I am wrong. I
looked it up and I use 11.8 volts. but 11.5 is fine as well.

I use an Eagle Tree MicroPower V3 logger and get a computer generated
log of the discharge. Then I fly with the logger and get an idea of
my real-world consumption and compare the two. Works great. Others
use a pretty common logger with a built-in load, I prefer the Eagle
Tree because it will log a flight one day and a battery the next.

Do you do your test in cold air to simulate high altitude, or just
room temp?

ps. If you are replacing the 12120 battery look at the 12140 or the
12150. Same size, heavier, and more capacity.

Brian

I've just done my annual battery testing and my process is similar.

I happened to automate the process and as such it works like this. I
have a small PLC that does the work. The battery is connected to a
resistive load to generate a roughly 0.6 Amp draw. The PLC looks at
the battery voltage once a minute until it reaches 10.5 volts ( I
chose 10.5 because I did want to stress the battery a little). The
PLC records the total number of minutes and once the 10.5 volt limit
is reached the load is disconnected and the battery is switched over
to a charger for a recharge. I can start a "test" at any time and
come back later and read the run time. With the battery going back on
charge automatically, I'm not worried about it sitting discharged at
the end of the test.

Now for the interesting part...

Back in march of 2008 I bought 2 new 7AH standard sized batteries and
tested them "new". They both went approximately 540 minutes. I
purchased them from an electronics supply store in town. In 2009 and
2010 I tested and the run times were very similar showing little
capacity loss.

My brother had heard from another club member that Academy here in
Houston actually sold better batteries and he bought one for his
glider. I loaned him my tester and his battery went 800 minutes.
This is a roughly 50% increase in duration so I went and bought one
initially, tested it and found mine also tested at 800 minutes and so
I bought a second and replaced both of my batteries. The second one
initially tested at 730 minutes, but with 3 cycles came up to 800
minutes as well. On a whim, I weighed the original 2008 batteries and
the new ones and found that the new ones weighed something like a 1/2
pound more, both of them.

Also in my testing this spring I ran my 17Ah battery on the tester and
replaced it after it demonstrated some unusual performance. On the
first test it ran only 300 minutes, but when I noticed it had run only
a short time I restarted the test without recharging it. It ran 500
more minutes and then quit again. I again started the test without
recharging and it went another 400 minutes. While I'm not sure why
that was happening, I am convinced that it's not a condition I want to
chance while flying so in this case I think the tester identified a
potentially suspect battery and $40 to replace it is cheap insurance.

I'll try to get the brand info for the batteries I bought at Academy
and re-post. Something like "wildgame" or similar... Cost $21.

Mark

On Mar 16, 7:01*pm, Nyal Williams wrote:
I know nothing about battery technology. *I take my batteries to Battery
Plus, who claims that they can recondition batteries and bring them up to
their proper rating. *Sometimes I get a battery back with the indication
that it is at say 113%; if the work brings it back to less than 95% there
is no charge and I throw it away. *The cost last year was $5.00 per
battery that came out well.

Am I getting good value?

At 00:40 17 March 2011, brianDG303 wrote:

On Mar 16, 4:00=A0pm, ContestID67 *wrote:
Each year I like to test my batteries and replace those that do not
have enough capacity for a typical flight of 3-4-ish hours with all
the electronics running. I run two batteries so that removes a worry
about loosing power during a record flight. =A0But how do you perform
a
good real world test?

My test is basically connecting a resistive load to the battery,
measure the battery voltage every 10 minutes or so. =A0Then wait for
the
battery voltage to drop to 11.5Vdc (an arbitratry but safe value).
Simple.

I create an Excel spreadsheet that explains all this - the testing
that I perform, the test rig that I used and templates for gathering
the data and then graphing the results. =A0
Seehttp://aviation.derosaweb.=
net/#batterytest.

I=92d love to hear any comments that you might have. =A0Enjoy.

John DeRosa
Johnderosaweb.com

John,
I have used that method and it works well, but.............
First, as I am sure you know, you want a load that is similar to the
real-life load. *I use a 12 volt lamp (AKA light bulb) and because I
have a lot of stuff I use a 10 watt lamp to create a 830 mA load which
is about what I pull.

If you are testing every 10 minutes you are working kind of hard. *My
battery, a 12120, takes hours to run down.

11.5 volts cut off is way too conservative. *The published data curve
for the 12120 ................................wait, I am wrong. I
looked it up and I use 11.8 volts. but 11.5 is fine as well.

I use an Eagle Tree MicroPower V3 logger and get a computer generated
log of the discharge. *Then I fly with the logger and get an idea of
my real-world consumption and compare the two. *Works great. *Others
use a pretty common logger with a built-in load, I prefer the Eagle
Tree because it will log a flight one day and a battery the next.

Do you do your test in cold air to simulate high altitude, or just
room temp?

ps. If you are replacing the 12120 battery look at the 12140 or the
12150. *Same size, heavier, and more capacity.

Brian

Has anyone tried a LiFePO4 battery such as the Shorai brand that can
be seen at:
http://www.batterystuff.com/batterie...14L2-BS12.html ?

Weight of the 12v 14ah LiFePO4 battery is 1.6 lb vs 13 lb for a sealed
lead acid battery. And, it's smaller.

Steve

On 3/16/2011 9:20 PM, SP wrote:

Has anyone tried a LiFePO4 battery such as the Shorai brand that can
be seen at:
http://www.batterystuff.com/batterie...14L2-BS12.html ?

Weight of the 12v 14ah LiFePO4 battery is 1.6 lb vs 13 lb for a sealed
lead acid battery. And, it's smaller.

I think you would be very disappointed in the amphour capacity of the
battery. From their website:

"The internal "completely discharged" capacity of a Shorai battery is
1/3 the rated "PbEq" capacity"

So the battery has only 14/3 = 4.7 amphours with a full discharge. They
are offering it as *starter* battery, and the "PbEq" (lead-acid
equivalent) rating indicates it will perform that task as well as
lead-acid battery with that amphour rating.

But it sure looked good at first...

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl

I've just done my annual battery testing and my process is similar.

I happened to automate the process and as such it works like this. I
have a small PLC that does the work. The battery is connected to a
resistive load to generate a roughly 0.6 Amp draw. The PLC looks at
the battery voltage once a minute until it reaches 10.5 volts ( I
chose 10.5 because I did want to stress the battery a little). The
PLC records the total number of minutes and once the 10.5 volt limit
is reached the load is disconnected and the battery is switched over
to a charger for a recharge. I can start a "test" at any time and
come back later and read the run time. With the battery going back on
charge automatically, I'm not worried about it sitting discharged at
the end of the test.

You are going the right way with this sort of a test. The meaningful
test is to check whether the battery is still performing as the maker
intended. Apply a load which will discharge it in 20 hours and find out
how long it takes for the voltage to drop to 10.5 volts (1.75v per cell).
The 20 hours and the 10.5 volts are the standard conditions used by
battery makers when claiming their capacities.

Having an automated tester will save you the boredom of watching a
voltmeter!

If you discharge a battery faster than 20 hours, on test or in the air,
you won't get the nominal ampere-hours out of the battery. If your
electronics (especially some radios) don't work down to 10.5 volts then
don't count on the endurance predicted from ampere-hours divided by load
- and if you fly at low ambients you will lose yet more capacity.

Some battery makers websites, eg Yuasa, have a lot of useful information
on how batteries behave with varying loads, at low temperatures, and when
subjected to repeated charge and discharge cycles.

On Mar 16, 10:37*pm, Eric Greenwell wrote:
On 3/16/2011 9:20 PM, SP wrote:

Has anyone tried a LiFePO4 battery such as the Shorai brand that can
be seen at:
http://www.batterystuff.com/batterie...L2-BS12.html*?

Weight of the 12v 14ah LiFePO4 battery is 1.6 lb vs 13 lb for a sealed
lead acid battery. And, it's smaller.

I think you would be very disappointed in the amphour capacity of the
battery. From their website:

"The internal "completely discharged" capacity of a Shorai battery is
1/3 the rated "PbEq" capacity"

So the battery has only 14/3 = 4.7 amphours with a full discharge. They
are offering it as *starter* battery, and the "PbEq" (lead-acid
equivalent) rating indicates it will perform that task as well as
lead-acid battery with that amphour rating.

But it sure looked good at first...

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl

There you go with amphors again!

Andy

On 3/17/2011 7:13 AM, Andy wrote:

There you go with amphors again!

It's a hard habit to break!

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On 3/17/2011 2:11 AM, Tim Newport-Peace wrote:

My test is basically connecting a resistive load to the battery,
measure the battery voltage every 10 minutes or so. Then wait for the
battery voltage to drop to 11.5Vdc (an arbitratry but safe value).
Simple.

I create an Excel spreadsheet that explains all this - the testing
that I perform, the test rig that I used and templates for gathering
the data and then graphing the results. See http://aviation.derosaweb.net/#bat
terytest.

I’d love to hear any comments that you might have. Enjoy.

John DeRosa
Johnatderosaweb.com


http://www.actmeters.com/

Gives a result in seconds.

The "GOLD-PLUS Intelligent Battery Tester" on the site has interesting
claims. Are there any reports from users on how well it works,
comparison tests with the usual constant current discharge method, and
details of the principles of it's method? Without more info, the ~$400
price is a bit off-putting.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)