Battery Power

[Mike McCarron[_2_]]

Help!

I have carefully measured my current draw in my glider at .8 amp. l would
like to know if there is any reasonable explanation for why a 9 amp hour
battery goes from 13 volts open circuit fully charged to 11.6 volts in 4
hours.

MC

[jfitch]

On Sunday, September 23, 2012 3:15:04 PM UTC-7, Mike McCarron wrote:
> Help!
>
>
>
> I have carefully measured my current draw in my glider at .8 amp. l would
>
> like to know if there is any reasonable explanation for why a 9 amp hour
>
> battery goes from 13 volts open circuit fully charged to 11.6 volts in 4
>
> hours.
>
>
>
> MC

Would need to know a lot more: Fully charge the battery and then let it rest off the charger for 12 hours. If it measures 13 V, then either your battery, charger, or DVM is bad. It should read about 12.6 - 12.8 depending on the technology assuming some sort of lead acid. Then run the battery for 4 hours with your 0.8A load. Then remove the load and let rest for several hours, then measure. Should measure about 12.1V or so. Measuring just after removing the charger, or under load, or just after removing the load will give you erroneous results, if your goal is to use voltage as a state of charge indication.

[Bart[_4_]]

> I have carefully measured my current draw in my glider at .8 amp. *l would
> like to know if there is any reasonable explanation for why a 9 amp hour
> battery goes from 13 volts open circuit fully charged to 11.6 volts in 4
> hours.

What's the battery type?

Bart

[Mike McCarron[_2_]]

At 15:53 24 September 2012, Bart wrote:
>> I have carefully measured my current draw in my glider at .8 amp. =A0l
>wo=
>uld
>> like to know if there is any reasonable explanation for why a 9 amp
hour
>> battery goes from 13 volts open circuit fully charged to 11.6 volts in
4
>> hours.
>
>What's the battery type?
>
>Bart
>
Power Sonic Model PS-1290 F2 Sealed Rechargeable

I am guessing lead acid

Mike

[Mike McCarron[_2_]]

At 15:53 24 September 2012, Bart wrote:
>> I have carefully measured my current draw in my glider at .8 amp. =A0l
>wo=
>uld
>> like to know if there is any reasonable explanation for why a 9 amp
hour
>> battery goes from 13 volts open circuit fully charged to 11.6 volts in
4
>> hours.
>
>What's the battery type?
>
>Bart
>
Power Sonic Model PS-1290 F2 Sealed Rechargeable

I am guessing lead acid

Mike

[Mike McCarron[_2_]]

At 15:53 24 September 2012, Bart wrote:
>> I have carefully measured my current draw in my glider at .8 amp. =A0l
>wo=
>uld
>> like to know if there is any reasonable explanation for why a 9 amp
hour
>> battery goes from 13 volts open circuit fully charged to 11.6 volts in
4
>> hours.
>
>What's the battery type?
>
>Bart
>
Power Sonic Model PS-1290 F2 Sealed Rechargeable

I am guessing lead acid

Mike

[Mike McCarron[_2_]]

At 15:53 24 September 2012, Bart wrote:
>> I have carefully measured my current draw in my glider at .8 amp. =A0l
>wo=
>uld
>> like to know if there is any reasonable explanation for why a 9 amp
hour
>> battery goes from 13 volts open circuit fully charged to 11.6 volts in
4
>> hours.
>
>What's the battery type?
>
>Bart
>
Power Sonic Model PS-1290 F2 Sealed Rechargeable

I am guessing lead acid

Mike

[Mike McCarron[_2_]]

At 15:53 24 September 2012, Bart wrote:
>> I have carefully measured my current draw in my glider at .8 amp. =A0l
>wo=
>uld
>> like to know if there is any reasonable explanation for why a 9 amp
hour
>> battery goes from 13 volts open circuit fully charged to 11.6 volts in
4
>> hours.
>
>What's the battery type?
>
>Bart
>
Power Sonic Model PS-1290 F2 Sealed Rechargeable

I am guessing lead acid

Mike

[Mike McCarron[_2_]]

At 15:53 24 September 2012, Bart wrote:
>> I have carefully measured my current draw in my glider at .8 amp. =A0l
>wo=
>uld
>> like to know if there is any reasonable explanation for why a 9 amp
hour
>> battery goes from 13 volts open circuit fully charged to 11.6 volts in
4
>> hours.
>
>What's the battery type?
>
>Bart
>
Power Sonic Model PS-1290 F2 Sealed Rechargeable

I am guessing lead acid

Mike

[Bart[_4_]]

On Sep 24, 10:30*am, Mike McCarron > wrote:
> Power Sonic Model PS-1290 F2 Sealed Rechargeable

http://tinyurl.com/c4n9hem

This battery is rated for 8.1 AH @ 810mA, when discharging to 10.5V.

The manufacturer's discharge curves suggest that if 11.6V is your
minimum, then you should get approximately 8 hours out of your battery
at 0.8A. Obviously, something is wrong.

There may be a voltage drop somewhere in your installation. This would
not affect open circuit measurements, but could be significant under
load. Where do you measure battery voltage? At the battery terminals,
at the panel?

The manufacturer says "Charge until battery voltage (under charge)
reaches 14.4 to 14.7 volts at 68°F (20°C). Hold at 14.4 to 14.7 volts
until current drops to under 90mA." Can you verify that this is what
your charger is doing?

Bart

[JohnDeRosa]

I just helped a fellow pilot test his batteries because he was having in-flight issues with a low battery after just 2 hours. It turned out that his brand new 12Vdc 14Ah battery was defective.

We tested using a 1.2A load (http://aviation.derosaweb.net/#batterytest). His other batteries lasted 5-6 hours at that high load level. We measured his real load by adding one device at a time to the grid. The "all on" load at 1A (constant transmit, audio vario beeping, etc). The somewhat surprising big power hog turned out to be the charging of the battery in his PDA.

[[email protected]]

On Sunday, September 23, 2012 6:15:04 PM UTC-4, Mike McCarron wrote:
> Help!
>
>
>
> I have carefully measured my current draw in my glider at .8 amp. l would
>
> like to know if there is any reasonable explanation for why a 9 amp hour
>
> battery goes from 13 volts open circuit fully charged to 11.6 volts in 4
>
> hours.
>
>
>
> MC

Mike,

Get a K2-Energy Lithium-Iron-Phosphate battery (http://store.peakbattery.com/12lfpba.html). They are expensive, but *much* lighter than the corresponding SLA type, and *much* better performance.

TA

[bumper[_4_]]

Do a search on Shorai lithium. Less expensive than K2, especially on larger batteries. Available on Amazon too. No experience with them.

We live in interesting times, battery wise (and otherwise).

bumper

[Eric Greenwell[_4_]]

On 9/27/2012 10:04 AM, bumper wrote:
> Do a search on Shorai lithium. Less expensive than K2, especially on
> larger batteries. Available on Amazon too. No experience with them.
>
> We live in interesting times, battery wise (and otherwise).

They are probably fine batteries for their intended purpose - starting
"powersports" vehicles, like snowmobiles, seados, etc. - but not for
powering equipment. Their amp hour rating is deceptive, because the amp
hour capacity mentioned is really about half the actual amp hour
capacity of the battery.

What they are selling you is a battery with same CCA rating (cold
cranking amps) as an SLA battery that has the amp hour rating Shorai
uses for it's "Powersports" battery. That's why it's cheaper - it's got
have the Lithium in it.

I'm not suggesting they are intentionally intending to deceive us, just
pointing out they use the amp hour rating in a manner confusing to
people who think it refers to capacity, and not "equivalent starting
performance".

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