Battery Power

Actually it is not 10 hours worth....its about 4 hours worth.

The "rated" 9 AH is rated at .05C or 450 ma.

If you run at 800 ma, that's about .1C.....so you don't get half the time,
you get way less than half...........

Also they rate the batteries as "dead" at 10.5 volts, but for glider
equipment, once you get down to 11.5 or so, stuff doesn't work well.

Actually anything under 12 volts means time to recharge.....below 10.5
volts and battery damage can occur.

For an 800 ma draw, the proper battery would be 16 AH.....this in theory
would last 20 hours, and leave you at 10.5 volts.....probably 10 hours to
stay above 11.5...

Cookie





At 03:30 24 September 2012, Mike the Strike wrote:
The 9A.h batteries I use would have a rated capacity of about 8A.h at a
current of 0.8A - that's about ten hours' worth. Dropping the
temperature
to freezing will drop that to about 7 to 8 hours - still more than you're
getting.

Also remember that the current drawn by some devices may increase as the
voltage drops. I'd suggest checking your current draw at a range of
battery voltages.

If your charger's ok, it sounds like your battery isn't.

Mike

Actually it is not 10 hours worth....its about 4 hours worth.

The "rated" 9 AH is rated at .05C or 450 ma.

If you run at 800 ma, that's about .1C.....so you don't get half the time,
you get way less than half...........

Also they rate the batteries as "dead" at 10.5 volts, but for glider
equipment, once you get down to 11.5 or so, stuff doesn't work well.

Actually anything under 12 volts means time to recharge.....below 10.5
volts and battery damage can occur.

For an 800 ma draw, the proper battery would be 16 AH.....this in theory
would last 20 hours, and leave you at 10.5 volts.....probably 10 hours to
stay above 11.5...

Cookie





At 03:30 24 September 2012, Mike the Strike wrote:
The 9A.h batteries I use would have a rated capacity of about 8A.h at a
current of 0.8A - that's about ten hours' worth. Dropping the
temperature
to freezing will drop that to about 7 to 8 hours - still more than you're
getting.

Also remember that the current drawn by some devices may increase as the
voltage drops. I'd suggest checking your current draw at a range of
battery voltages.

If your charger's ok, it sounds like your battery isn't.

Mike

Actually it is not 10 hours worth....its about 4 hours worth.

The "rated" 9 AH is rated at .05C or 450 ma.

If you run at 800 ma, that's about .1C.....so you don't get half the time,
you get way less than half...........

Also they rate the batteries as "dead" at 10.5 volts, but for glider
equipment, once you get down to 11.5 or so, stuff doesn't work well.

Actually anything under 12 volts means time to recharge.....below 10.5
volts and battery damage can occur.

For an 800 ma draw, the proper battery would be 16 AH.....this in theory
would last 20 hours, and leave you at 10.5 volts.....probably 10 hours to
stay above 11.5...

Cookie





At 03:30 24 September 2012, Mike the Strike wrote:
The 9A.h batteries I use would have a rated capacity of about 8A.h at a
current of 0.8A - that's about ten hours' worth. Dropping the
temperature
to freezing will drop that to about 7 to 8 hours - still more than you're
getting.

Also remember that the current drawn by some devices may increase as the
voltage drops. I'd suggest checking your current draw at a range of
battery voltages.

If your charger's ok, it sounds like your battery isn't.

Mike

On 9/24/2012 8:39 AM, Bob Cook wrote:
Actually it is not 10 hours worth....its about 4 hours worth.

The "rated" 9 AH is rated at .05C or 450 ma.

If you run at 800 ma, that's about .1C.....so you don't get half the time,
you get way less than half...........

Also they rate the batteries as "dead" at 10.5 volts, but for glider
equipment, once you get down to 11.5 or so, stuff doesn't work well.

Actually anything under 12 volts means time to recharge.....below 10.5
volts and battery damage can occur.

For an 800 ma draw, the proper battery would be 16 AH.....this in theory
would last 20 hours, and leave you at 10.5 volts.....probably 10 hours to
stay above 11.5...

Hi Cookie - I agree it's a good rule of thumb to use batteries at the 20
hour rate, and I encourage pilots use it; however, it doesn't seem to be
the problem. Using a bigger battery is desirable in general, but may be
awkward to do in practice.

SLA data sheets show a 10% reduction in AH capacity at the 0.1C rate,
and if you restrict the voltage drop to 11.5 volts, you lose another
10%. That lowers his 9 AH to 7.2 AH, allowing a nominal 9 hour run time
at 800 ma. Since he is getting only 4 hours, something is dramatically
wrong. A full charge, then a discharge test at 800 ma can rule out
charger/battery problems, and it's easy, so that is where I would start.

Also, unless you have old "stuff", 11.5 volts is plenty of voltage to
run things, and he didn't mention any problems.

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

On Monday, September 24, 2012 11:45:03 AM UTC-4, Cookie wrote:
Actually it is not 10 hours worth....its about 4 hours worth.



The "rated" 9 AH is rated at .05C or 450 ma.



If you run at 800 ma, that's about .1C.....so you don't get half the time,

you get way less than half...........



Also they rate the batteries as "dead" at 10.5 volts, but for glider

equipment, once you get down to 11.5 or so, stuff doesn't work well.



Actually anything under 12 volts means time to recharge.....below 10.5

volts and battery damage can occur.



For an 800 ma draw, the proper battery would be 16 AH.....this in theory

would last 20 hours, and leave you at 10.5 volts.....probably 10 hours to

stay above 11.5...



Cookie











At 03:30 24 September 2012, Mike the Strike wrote:

The 9A.h batteries I use would have a rated capacity of about 8A.h at a

current of 0.8A - that's about ten hours' worth. Dropping the

temperature

to freezing will drop that to about 7 to 8 hours - still more than you're

getting.



Also remember that the current drawn by some devices may increase as the

voltage drops. I'd suggest checking your current draw at a range of

battery voltages.



If your charger's ok, it sounds like your battery isn't.



Mike



Cookie nailed it. Also, that is all for a new battery. The numbers all go sour as the battery gets old and abused. Deep discharge is the worst offender over time. Keep 'em charged boys! (Yes even in off-seasons).

-Jim

If I am reading the data sheet correctly, I see a lot more than a 10%
reduction in AH at the .1C rate...more like 50%

Cookie






At 17:41 24 September 2012, Eric Greenwell wrote:
On 9/24/2012 8:39 AM, Bob Cook wrote:
Actually it is not 10 hours worth....its about 4 hours worth.

The "rated" 9 AH is rated at .05C or 450 ma.

If you run at 800 ma, that's about .1C.....so you don't get half the
time,
you get way less than half...........

Also they rate the batteries as "dead" at 10.5 volts, but for glider
equipment, once you get down to 11.5 or so, stuff doesn't work well.

Actually anything under 12 volts means time to recharge.....below 10.5
volts and battery damage can occur.

For an 800 ma draw, the proper battery would be 16 AH.....this in
theory
would last 20 hours, and leave you at 10.5 volts.....probably 10 hours
to
stay above 11.5...

Hi Cookie - I agree it's a good rule of thumb to use batteries at the 20
hour rate, and I encourage pilots use it; however, it doesn't seem to be
the problem. Using a bigger battery is desirable in general, but may be
awkward to do in practice.

SLA data sheets show a 10% reduction in AH capacity at the 0.1C rate,
and if you restrict the voltage drop to 11.5 volts, you lose another
10%. That lowers his 9 AH to 7.2 AH, allowing a nominal 9 hour run time
at 800 ma. Since he is getting only 4 hours, something is dramatically
wrong. A full charge, then a discharge test at 800 ma can rule out
charger/battery problems, and it's easy, so that is where I would start.

Also, unless you have old "stuff", 11.5 volts is plenty of voltage to
run things, and he didn't mention any problems.

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

just rechecked the powersonic manual....

at .1c a 12 volt battery will drop below 12 volts in about 5 hours...below
11.5 in about 6.........10.5 almost 10 hours

Cookie




At 17:41 24 September 2012, Eric Greenwell wrote:
On 9/24/2012 8:39 AM, Bob Cook wrote:
Actually it is not 10 hours worth....its about 4 hours worth.

The "rated" 9 AH is rated at .05C or 450 ma.

If you run at 800 ma, that's about .1C.....so you don't get half the
time,
you get way less than half...........

Also they rate the batteries as "dead" at 10.5 volts, but for glider
equipment, once you get down to 11.5 or so, stuff doesn't work well.

Actually anything under 12 volts means time to recharge.....below 10.5
volts and battery damage can occur.

For an 800 ma draw, the proper battery would be 16 AH.....this in
theory
would last 20 hours, and leave you at 10.5 volts.....probably 10 hours
to
stay above 11.5...

Hi Cookie - I agree it's a good rule of thumb to use batteries at the 20
hour rate, and I encourage pilots use it; however, it doesn't seem to be
the problem. Using a bigger battery is desirable in general, but may be
awkward to do in practice.

SLA data sheets show a 10% reduction in AH capacity at the 0.1C rate,
and if you restrict the voltage drop to 11.5 volts, you lose another
10%. That lowers his 9 AH to 7.2 AH, allowing a nominal 9 hour run time
at 800 ma. Since he is getting only 4 hours, something is dramatically
wrong. A full charge, then a discharge test at 800 ma can rule out
charger/battery problems, and it's easy, so that is where I would start.

Also, unless you have old "stuff", 11.5 volts is plenty of voltage to
run things, and he didn't mention any problems.

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

On Sep 24, 6:45*pm, Bob Cook wrote:
If I am reading the data sheet correctly, I see a lot more than a 10%
reduction in AH at the .1C rate...more like 50%

Ctrl-C/Ctrl-V:

Nominal Capacity
20-hr. (450mA to 10.50
volts) .................................................. ..... 9.00
AH
10-hr. (810mA to 10.50
volts) .................................................. ....... 8.10
AH

B.

http://www.power-sonic.com/images/po...hManual-Lo.pdf

See page 8.....

Chart for certain temp. and new battery...Colder or older will net worse
time.

You really want to stay in the "over 12 volt" range of this chart.

Again... 9 AH rated battery is kind of borderline for glider flying at 800
Ma draw....

Solution = larger battery or second battery.

Cookie






At 01:50 25 September 2012, Bart wrote:
On Sep 24, 6:45=A0pm, Bob Cook wrote:
If I am reading the data sheet correctly, I see a lot more than a 10%
reduction in AH at the .1C rate...more like 50%

Ctrl-C/Ctrl-V:

Nominal Capacity
20-hr. (450mA to 10.50
volts) .................................................. ..... 9.00
AH
10-hr. (810mA to 10.50
volts) .................................................. ....... 8.10
AH

B.

On Sep 25, 4:15*am, Bob Cook wrote:
On Sep 24, 6:45=A0pm, Bob Cook *wrote:
If I am reading the data sheet correctly, I see a lot more than a 10%
reduction in AH at the .1C rate...more like 50%
Ctrl-C/Ctrl-V:
Nominal Capacity
20-hr. (450mA to 10.50
volts) *................................................. ...... 9.00
AH
10-hr. (810mA to 10.50
volts) *................................................. ........ 8.10
AH
http://www.power-sonic.com/images/po...1277751263_201...

See page 8.....

Chart for certain temp. and new battery...Colder or older will net worse
time.

Yeah, I still see about 10% reduction in capacity at 0.1C. Where you
see the 50% reduction, I have no idea. Unless you thought "reduction
in discharge time" but wrote "reduction in AH."

Bart