glider battery duration problems

I guess it depends on how one defines capacity. If you take it as voltage drop from 12V then it is probably the 3% value that you use. If you take it as the battery's ability to do work and the SLA stops doing useful work at 10 V, then you have a 2V range from which the percentage is calculated resulting in the larger drop I quote.

Of course, the thing about statistics is that they will tell you whatever you want if you torture them long enough.

Dave Springford wrote, On 10/2/2013 5:57 PM:
I guess it depends on how one defines capacity. If you take it as
voltage drop from 12V then it is probably the 3% value that you use.
If you take it as the battery's ability to do work and the SLA stops
doing useful work at 10 V, then you have a 2V range from which the
percentage is calculated resulting in the larger drop I quote.

Of course, the thing about statistics is that they will tell you
whatever you want if you torture them long enough.

Capacity is defined as amp hours (sometimes energy is used). It is
definitely not defined as voltage or voltage lost, though measuring
"standing" voltage is one way to estimate the state of charge. Fully
charge an SLA battery, let it sit for a month at 68 deg F, measure the
amp hours, and they will be about 3% less than if you had measured them
right after charging. That means an 8 amp hour battery loses about 0.24
amp hours a month. The voltage will also fall during the month,
approximately 3% of that two volt working range, or about 0.05 volts.

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

The original post was evidently about old batteries that just need replacing with anything new. Replace with the less expensive SLA if you don't intend to fly long days or multiple days without charging, and don't mind replacing again soon. There are no "made in USA" SLA batteries. Hawker Cyclon (used to be Gates X Cell) are the only holdout.
All the "SLA replacement" LiFePO4 batteries have overcharge and over discharge protection. You can use any good multi-stage charger for 12V batteries. Personally prefer the Xenotronics.
Here's a controller (from a much earlier thread) you can use in the trailer to charge two onboard batteries. Works for LiFePO4, but misses the top few millivolts. You can still do a 750k or so on one 10AH LiFePO4 charged with them if you have a full modern panel (VGA display, transponder, com, flarm, etc)
Jim

http://www.futurlec.com/Dual_Charge_Controller.shtml

Further to Dave's comments, I've done some simple discharge testing on my K2 12V/10AH LiFePo4, and it's pretty impressive. At a discharge rate of over 1C, I'm seeing the nearly the full rated capacity (1.2A bulb simulating the load). It never drops below 11V until it starts to fall off rapidly and shuts itself off. I'm seeing 7 hours at that rate (the capacity is theoretically derived at a discharge rate of 1 Amp, so it "should" be a little less than 10AH at the higher discharge rate as I understand it. I use the same smart charger that I used to use for 12V SLA batteries, and it seems to be working just fine. I would love to see an even higher capacity version, even with the larger foot print. The energy density is such that it would still be significantly lighter than an equivalent SLA battery.

P3



On Wednesday, October 2, 2013 7:15:29 PM UTC-4, Dave Springford wrote:
Don't confuse the Li-Ion batteries with the LiFePo4 batteries that are mentioned above. While the Li-Ion batteries have the instability problems associated with thermal runaway during rapid discharge, the Lithium-Iron-Phosphate (LiFePo4) chemistry is stable and do not have these problems.



There are many knock-off Chinese battery packs on the market that are called LiFePo, but be careful what you buy. I am a re-seller for K2 Energy batteries, and these are made in the USA, true LiFePo4 chemistry. I have spent hours on the phone with Mark Stoker at K2 comparing their batteries to some of the cheaper competition and some of the competitors numbers don't add up. The LiFePo4 chemistry is patented and K2 pays patent fees to the patent holder to use it, while many of the others don't. Visit the K2 website for more information at: http://www.k2battery.com/battery-packs-12v.html



Some of the advantages of the LiFePo4 chemistry over the SLA's (sealed Lead Acid) is that it holds peak voltage for much longer during discharge. The SLA's discharge curve is a continually declining slope that quickly reaches the 10 V level where things start to shut-off, while the LiFePo4 discharge curve is almost a straight line from the initial charge of 13 V. See the discharge curve he

http://www.foxonecorp.com/images/sto...0discharge.png



Advantages of the LiFePo4 batteries



provide much longer battery use during flight.



can be used for at least 2000 discharge-recharge cycles, compared to 300 for SLA's



hold their charge during the off-season loosing only 1% per month (unlike the SLA batteries that loose 25-30% per month)



don't have the special charge/discharge requirements of the early Li-ion types and can be charged with most normal SLA chargers as long as they can provide a 14.6 V peak charge voltage



The K2 batteries have the highest capacity available at ANY discharge rate available on the market.





Contact me if you would like more info



Dave Springford

www.foxonecorp.com

Call me an energy whore, but I'm looking at this one:
http://www.amazon.com/Bioenno-Power-...ifepo4+battery


"Papa3" wrote in message
...
Further to Dave's comments, I've done some simple discharge testing on my K2
12V/10AH LiFePo4, and it's pretty impressive. At a discharge rate of over
1C, I'm seeing the nearly the full rated capacity (1.2A bulb simulating the
load). It never drops below 11V until it starts to fall off rapidly and
shuts itself off. I'm seeing 7 hours at that rate (the capacity is
theoretically derived at a discharge rate of 1 Amp, so it "should" be a
little less than 10AH at the higher discharge rate as I understand it. I
use the same smart charger that I used to use for 12V SLA batteries, and it
seems to be working just fine. I would love to see an even higher capacity
version, even with the larger foot print. The energy density is such that
it would still be significantly lighter than an equivalent SLA battery.

P3



On Wednesday, October 2, 2013 7:15:29 PM UTC-4, Dave Springford wrote:
Don't confuse the Li-Ion batteries with the LiFePo4 batteries that are
mentioned above. While the Li-Ion batteries have the instability problems
associated with thermal runaway during rapid discharge, the
Lithium-Iron-Phosphate (LiFePo4) chemistry is stable and do not have these
problems.



There are many knock-off Chinese battery packs on the market that are
called LiFePo, but be careful what you buy. I am a re-seller for K2
Energy batteries, and these are made in the USA, true LiFePo4 chemistry.
I have spent hours on the phone with Mark Stoker at K2 comparing their
batteries to some of the cheaper competition and some of the competitors
numbers don't add up. The LiFePo4 chemistry is patented and K2 pays
patent fees to the patent holder to use it, while many of the others
don't. Visit the K2 website for more information at:
http://www.k2battery.com/battery-packs-12v.html



Some of the advantages of the LiFePo4 chemistry over the SLA's (sealed
Lead Acid) is that it holds peak voltage for much longer during discharge.
The SLA's discharge curve is a continually declining slope that quickly
reaches the 10 V level where things start to shut-off, while the LiFePo4
discharge curve is almost a straight line from the initial charge of 13 V.
See the discharge curve he

http://www.foxonecorp.com/images/sto...0discharge.png



Advantages of the LiFePo4 batteries



provide much longer battery use during flight.



can be used for at least 2000 discharge-recharge cycles, compared to
300 for SLA's



hold their charge during the off-season loosing only 1% per month
(unlike the SLA batteries that loose 25-30% per month)



don't have the special charge/discharge requirements of the early
Li-ion types and can be charged with most normal SLA chargers as long as
they can provide a 14.6 V peak charge voltage



The K2 batteries have the highest capacity available at ANY discharge
rate available on the market.





Contact me if you would like more info



Dave Springford

www.foxonecorp.com

On Thursday, October 3, 2013 10:06:36 AM UTC-4, Dan Marotta wrote:
Call me an energy whore, but I'm looking at this one:

http://www.amazon.com/Bioenno-Power-...ifepo4+battery



P-l-e-a-s-e use batteries in rugged (e.g. ABS) cases, not poly shrink wrap.

I've had good luck so far with the Bioenno 12 AH LFP battery + charger.

-Evan Ludeman / T8

"P-l-e-a-s-e use batteries in rugged (e.g. ABS) cases, not poly shrink wrap."

How about bamboo!?
http://www.electric-bike-kit.com/lit...placement.aspx

The battery I linked to is by the same manufacturer you're espousing. I've
read the technical details and can't find anything about the case, much less
"poly shrink wrap". Where did you come up with that description?

If it is, indeed, a flimsy wrapper, I could always make a fiberglass box to
house it and bond it into the fuselage very near the CG.

"Evan Ludeman" wrote in message
...
On Thursday, October 3, 2013 10:06:36 AM UTC-4, Dan Marotta wrote:
Call me an energy whore, but I'm looking at this one:

http://www.amazon.com/Bioenno-Power-...ifepo4+battery



P-l-e-a-s-e use batteries in rugged (e.g. ABS) cases, not poly shrink
wrap.

I've had good luck so far with the Bioenno 12 AH LFP battery + charger.

-Evan Ludeman / T8

On Wednesday, October 2, 2013 11:46:32 AM UTC-6, John Marshall wrote:
I need advice about the best choice of batteries for an asg 29e. lithium

ion would be outside manufacturer's remit and the insurer's plus too many

risks-the fuel tank is directly above the battery housings. I would like

something with at least 9 amp hours, whether gel cell or mh.

Maybe this is way off track - but maybe you have a transponder ?
if most transponders are not specially programmed (set up) they will
run all the time - they are "on" all of the time - drawing power even
when your panel read out says "off" - I had that problem in 2 gliders -
EB28 Edition - another solution to check this power loss is to unplug
the transponder and see if that solves the problem - if it does then
get out your manual and find out how to change the settings - good luck

On Wednesday, October 23, 2013 8:15:26 PM UTC-4, wrote:
if most transponders are not specially programmed (set up) they will
run all the time - they are "on" all of the time - drawing power even
when your panel read out says "off"

Say what ? A transponder should draw very little power except
when it is transmitting, which it only does when interrogated.
A Mode S transponder draws less than Mode C as it responds to
selective (fewer) interrogations (yes Daryll, I'm simplifying).
The only notable draw for a transponder installation would be a
poor quality encoder (older models have power-hungry heaters
rather than temperature-compensated altitude transducers);
should not be a problem for modern units...

Perhaps you can email me offline make/model of the setup
which gave you power problems?

Hope that helps,
Best Regards, Dave