Surprising Lite Load Alk/NiMH Test

[jayflash]

A variety of different brands of AA alkaline cells lasted from 10 - 13 hours in my scanner before the (one volt) low battery alarm began beeping.

All of my one to two year old "Duraloop" and ROV Hybrid cells provided 15 - 16 hours of service before "low bat."

At only a 130 mA load I expected more from the alkies. Had the scanner been active and set at high volume, the difference would have been greater.

 

[Mr Happy]

In a way, it is interesting that the rechargeable cells did so well.

You might be interested in the Energizer Alkaline Handbook and Fig. 13 particularly. I think your numbers are roughly consistent with that chart.

 

[VidPro]

a 130ma load that is like the load of a modern piece of electronics, poor alkalines :-)
with LSD the alkalines can be pretty much discontinued
which leaves that stuff people have laying about that might go 6 full months before its next use, and then although there is a charge on the LSD the voltage under load has dropped compared to alkies.

i still use alkaline in remotes, but not sure why , a single leakage is worse than a 6 month recharge
and i still use them in the house digital HVAC controller, but i am not quite sure why , when it only goes a year before complaining too.
if i had a wall clock, like the single AA type i would probably use alkies there too

 

[MorePower]

A variety of different brands of AA alkaline cells lasted from 10 - 13 hours in my scanner before the (one volt) low battery alarm began beeping.

All of my one to two year old "Duraloop" and ROV Hybrid cells provided 15 - 16 hours of service before "low bat."

At only a 130 mA load I expected more from the alkies. Had the scanner been active and set at high volume, the difference would have been greater.

That's a bit surprising. 10 hours to 1.0V on a decent alkaline cell should happen at closer to 200mA discharge rate.

Is it possible that your scanner has occasional short, high spikes in current draw, and that's what sets off the low battery alarm? NiMH cells would be much better able to deal with that.

You'll note in Mr. Happy's linked PDF (in figure 12) that at 100mA continuous, an Energizer AA should last ~22 hours to 1.0V. An increase to 130mA shouldn't cut that time in half. I'd suspect bad cells, or the aforementioned current spikes causing early cutout.

Mr. Happy-
I don't see how Fig. 13 could be considered consistent with jayflash's results. Nearly 2500mAh to 0.8V at 100mA doesn't translate to 10 hours to 1.0V at 130mAh

 

[jayflash]

I only used my Fluke 112 and not a scope so it's likely that current is being consumed in much higher pulses than the average reading. Given that only two AA cells are used, I'd guess the load is more difficult than what appears at first glance.

Thanks for the link, Mr. :) and the other replies.

 

[Mr Happy]

Mr. Happy-
I don't see how Fig. 13 could be considered consistent with jayflash's results. Nearly 2500mAh to 0.8V at 100mA doesn't translate to 10 hours to 1.0V at 130mAh

I reason it like this. A "Duraloop" or Hybrid cell provides a reliable reference of about 2000 mAh. If we say 2000 mAh discharged in 15 hours, that would be 130 mA, so it is consistent with the meter reading.

For the alkaline cell we have nearly 2500 mAh at 100 mA. It will be a bit lower at 130 mA, say 2300 mAh. It will be a bit lower still when discharging to 1.0 V instead of 0.8 V, say 2100 mAh. That puts us in the ballpark of the rechargeable. Allowing that different brands of alkaline cell can vary by 30% or more in capacity, the reported results are conceivable. I think we may imagine that Energizer's graph is presented in the most favorable light using their highest quality cell under ideal test conditions.

 

[Black Rose]

What type of scanner was it?

I have a Uniden BC95XLT that I use primarily for listening to aircraft communications.
I've never run alkaline cells in it, only regular and LSD NiMh cells.

 

[jayflash]

It's a Uniden BC72XLT. Unsquelched at full volume it draws about 320 mA which may represent an approximate 3% duty cycle.

Although unused, the alks had expiration dates ranging from 2013 - 2015 and were at room temperature for some months. I store the bulk of my stash at ~50F in an insulated box in the cellar.