Battery Power

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.

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

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

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)