Spring Cleaning and Battery Testing

Thanks for all your comments...here are some of my comments on your
comments!

"11.5 volts cut off is way too conservative"
- Probably true. But I am an engineer and being conservative is
inbred. I just don't know what devices people are using. Older
radios don't even like anything less than 12Vdc - thus the reason you
see those odd combo batteries to get to something like 13.6Vdc. Most
moden electronics can survive down to 11Vdc and lower. So 11.5 seems
like a reasonable middle ground.

"I happened to automate the process and as such it works like this. I
have a small PLC that does the work."
"Eagle Tree MicroPower V3 logger"
"http://www.actmeters.com/"
- These are all wonderful tools which I have also used. But for those
that only test a couple of batteries once a year, these systems are
something that most people cannot justify - either too expensive or
too complicated to make. My $0.02.

"testing every 10 minutes you are working kind of hard. My battery, a
12120, takes hours to run down. "
- I guess I like nice smooth curves on my graphs. ;-) Call me
crazy. And yes it takes hours. But I do this while doing my day job
(from home) so I just glance over once in a while and take a reading.
Simple. Your mileage may vary. To speed things up does using a 2x
load and then double the resulting run time make sense?

"Do you do your test in cold air to simulate high altitude, or just
room temp?"
- Room temperature. Flying in the Midwest I don't have much of a
temperature swing to worry about. Not to mention I don't have a
temperature chamber handy. But I understand your concern for the wave
flight types. A refrigerator or ice chest? Too cold? How much is a
lead-acid battery's chemistry changed by temperature? Hmmmm.

"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."
- I have noticed that if you take a large load off of a lead-acid gel
cell battery the voltage will recover somewhat. I don't know the
chemistry to understand why. So I wonder if you battery test rig is
getting fooled into releasing the load at your trip voltage, then the
battery recovers, and you repeat the cycle. Just a thought.

"If you are replacing the 12120 battery, look at the 12140 or the
12150. Same size, heavier, and more capacity."
- Thanks for the idea. I replace a battery per year in my set of
four. Two are on charge and two are in the glider at any one time.
So during my next annual battery buying time I will keep that in
mind.

Lastly - What I am trying to do is create a system of battery testing
that everyone can use with tools that they probably have around the
house or can purchase cheaply. All you need is a pencil, paper, a few
cheap resistors and a voltmeter. What are digical voltmeters going
for these days? $10?

Thanks again,
John DeRosa

One other thought for the automated "instant" testers - While this may
indicate the Ah capacity of the battery, is that an accurate
indication of the often asked question "But, how long will it last?"
Literally, does it tell me how many minutes do I have between full
charge and my minimum voltage threshold? There is certainly a
corrolation between Ah capacity and the duration of actual use, but is
there a formula?

Thanks once again, John DeRosa

On Mar 18, 8:01*am, ContestID67 wrote:
One other thought for the automated "instant" testers - While this may
indicate the Ah capacity of the battery, is that an accurate
indication of the often asked question "But, how long will it last?"
Literally, does it tell me how many minutes do I have between full
charge and my minimum voltage threshold? *There is certainly a
corrolation between Ah capacity and the duration of actual use, but is
there a formula?

Thanks once again, John DeRosa

Hi John,
I expect just about everyone that has a fancy set-up started with a
lamp, a voltmeter, and clock. It is a very accurate system at a very
low cost, I suspect more accurate than the "GOLD-PLUS Intelligent
Battery Tester". Just takes a lot longer.

Every battery has a certain Ah capacity at a given load. For example,
the 12120 battery is rated to deliver 1 amp for 14 hours (not all
batteries have such a lovely symmetry to their spec) and is rated to
deliver 24 amps for 12 minutes and 2.4 amps for 4 hours. Having a
discharge curve is useful. Looking at that curve I see the battery
will provide your load of .6 amps for about 17 hours. I have a
transponder, two varios one of which has an illuminated display, a
very bright LX Minimap, and still keep everything to .85 amp. So
according to that curve I'll get 10 or 12 hours from a new battery,
less as it gets cold or old. I plan to acquire a 12150 (15 Ah) and
also have a 2.4 Ah back-up I can switch to.

Is that what you were asking about as far as a formula? Really I
think you want to match the load (light bulb) to be as close to your
glider load as you can, or a little more. Then the length of your
test will be the same as the duration of your battery in flight. The
other consideration is that your battery will last much longer if you
don't discharge it all the to flat very often. In theory you could
take a 12120 and never fly it down past 12 volts and it would last
quite a few years.

Brian

cheap resistors and a voltmeter. What are digical voltmeters going
for these days? $10?

Thanks again,
John DeRosa

$3 to Free if you watc the specials at Harbor Freight!

John

A little off-topic, but worth saying.

The best way to get the longest life from a lead-acid battery is to
always keep it topped off. It's amazing to me how many people use
their batteries, then let them set in various states of discharge,
then charge it the night before they go flying again. Or they don't
charge it at all until their instruments quit. Some might not know
there are chemical differences in a battery at different states of
charge. The more you keep it topped off, the longer it will continue
to perform well.

I have two 7ah batteries that I alternate. The first thing I do when I
get home from flying is put it back on the charger. Five years old and
going strong. I test them once a year with my West Mountian Radio
battery analyzer. They're almost as healthy as when they were brand
new.

On Fri, 18 Mar 2011 12:51:34 -0700, Westbender wrote:

I have two 7ah batteries that I alternate. The first thing I do when I
get home from flying is put it back on the charger. Five years old and
going strong. I test them once a year with my West Mountian Radio
battery analyzer. They're almost as healthy as when they were brand new.

I do exactly the same except that:

- I carry both my batteries on every flight (one drives radio and T&B,
the other drives varios and PNA.

- I have a pair of 3 stage mains lead-acid chargers for the after-flight
recharge.

- I do the annual cycle and capacity measurement with a Pro-Peak
Prodigy II model flying charger.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Mar 18, 8:52*am, brianDG303 wrote:
On Mar 18, 8:01*am, ContestID67 wrote:

One other thought for the automated "instant" testers - While this may
indicate the Ah capacity of the battery, is that an accurate
indication of the often asked question "But, how long will it last?"
Literally, does it tell me how many minutes do I have between full
charge and my minimum voltage threshold? *There is certainly a
corrolation between Ah capacity and the duration of actual use, but is
there a formula?

Thanks once again, John DeRosa

Hi John,
I expect just about everyone that has a fancy set-up started with a
lamp, a voltmeter, and clock. *It is a very accurate system at a very
low cost, I suspect more accurate than the "GOLD-PLUS Intelligent
Battery Tester". *Just takes a lot longer.

Every battery has a certain Ah capacity at a given load. *For example,
the 12120 battery is rated to deliver 1 amp for 14 hours (not all
batteries have such a lovely symmetry to their spec) and is rated to
deliver 24 amps for 12 minutes and 2.4 amps for 4 hours. *Having a
discharge curve is useful. *Looking at that curve I see the battery
will provide your load of .6 amps for about 17 hours. *I have a
transponder, two varios one of which has an illuminated display, a
very bright LX Minimap, and still keep everything to .85 amp. *So
according to that curve I'll get 10 or 12 hours from a new battery,
less as it gets cold or old. *I plan to acquire a 12150 (15 Ah) and
also have a 2.4 Ah back-up I can switch to.

Is that what you were asking about as far as a formula? *Really I
think you want to match the load (light bulb) to be as close to your
glider load as you can, or a little more. *Then the length of your
test will be the same as the duration of your battery in flight. *The
other consideration is that your battery will last much longer if you
don't discharge it all the to flat very often. *In theory you could
take a 12120 and never fly it down past 12 volts and it would last
quite a few years.

Brian

One thing to consider if using a lightbulb as a load is that the
resistance is current dependent. You will not get quite the same
discharge curve as you would using a fixed resistance load.

The variable resistance characteristic of lamps was made use of in
some battery charging circuits. A series lamp can be used to limit
current when the battery under charge is at low voltage but still
allow it to reach full charge voltage. Sure, this is late 70's
technology but it worked quite well before exotic computer controlled
chargers were available.

I still have my RST crew radio that used 2 car light bulbs in the
charging circuit. A relay split the 12v pack into 2 6v packs for
charging when plugged into the crew car.

Andy

On Mar 18, 9:12*am, "John Scott" wrote:

$3 to Free if you watc the specials at Harbor Freight!

Just be sure you don't get one with a photo-voltaic display! I had
one that drove me nuts until I realized that the readings it gave were
different in sunlight than if used indoors. Just shade the display
and watch the reading change.

Andy

On Mar 18, 3:51*pm, Westbender wrote:
A little off-topic, but worth saying.

The best way to get the longest life from a lead-acid battery is to
always keep it topped off. It's amazing to me how many people use
their batteries, then let them set in various states of discharge,
then charge it the night before they go flying again. Or they don't
charge it at all until their instruments quit. Some might not know
there are chemical differences in a battery at different states of
charge. The more you keep it topped off, the longer it will continue
to perform well.

I have two 7ah batteries that I alternate. The first thing I do when I
get home from flying is put it back on the charger. Five years old and
going strong. I test them once a year with my West Mountian Radio
battery analyzer. They're almost as healthy as when they were brand
new.

What does the group think about desulfautors? I've done some
searching and see lots of widely varying opinions (which I suspect
I'll get here as well).

On 3/18/2011 9:17 PM, Papa3 wrote:


What does the group think about desulfautors? I've done some
searching and see lots of widely varying opinions (which I suspect
I'll get here as well).

I'm skeptical about their value, because the only place I've seen them
touted is by the people that sell them, and I've never seen a technical
manual from Powersonic, Yuasa, Panasonic, etc., for SLA batteries that
even mentions them, much less suggest them. Instead, the manuals and
battery datasheets always recommend three phase chargers as the best
type of charger. Approximately...

Phase 1: constant current until 14.5 volts is reached
Phase 2: constant voltage 14.5 until the charge current drops off to 2%
of amp-hour rating (e.g., 7 AH x 2% = 0.140 amps)
Phase 3: constant voltage at 13.7 volts

But, I'm not aware that they do any harm, either.

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