Here's a long post that appeared on the news group RAMPS. What is RAMPS? (See FAQ021-WIRELESS)
To the Group:
Here's the results of the new version of the iPower 500 mA rechargeable Li Ion Polymer battery tests. We also ran tests on the Ultralife 9 Volt single use lithiums and standard Eveready alkaline 9 Volts for reference. The batteries were run down multiple times in a UM450 because it is a power hog, 125 mA at 8 Volts or 1 Watt (!). We then ran the batteries down in a UM400 (a power piglet) just for further reference. In all cases the transmitters were run continuously until shut down of the transmitter. The batteries were then put on the charger and recharged. It made little difference if the battery was charged for one hour (green indicator just came on) or overnight. The runs were at 72 F ambient. Here's the results:
The first iPower battery in UM450:
The second iPower battery in UM450:
3:10 (double charged. See end of post.)
Brand new from the factory Ultralife Lithium in UM450:
Few months old Eveready Alkaline in UM450:
The Ultralife does not like the high current demands of the UM450 and does worse than an Eveready alkaline. The 500 mAh iPower has almost exactly 50% more capacity than either, at this high current load. If you remember the previously posted cold tests, the iPower also did quite well, though that was on a 400 mAh battery. Below are tests in a UM400, a more normal load:
The first iPower battery in UM400:
The second iPower battery in UM400:
Two brand new from the factory Ultralife Lithiums in UM400:
Two (few months old) Eveready Alkalines in UM400:
Here the Ultralife Lithiums come into their own, since the current drains are more reasonable and show a 62% increase in battery life compared to the Eveready alkalines as standards. The iPowers still show a good 20% increase over the alkalines.
This UM400 was a block 29 and seemed to pull a little more current than the average UM400. The ratios of battery life should still be valid. If you are getting a particular battery life on alkaline Evereadys, simply add the proper percentage. If you are using ProCells (Mallory) the iPower improvement will be an additional 10% more (30% instead of 20% for example).
Doing a 100% discharge on Li Ion Poly batteries (iPowers) is worst case for usage.
The iPowers work well in the cold.
We tried a "double" charge on the iPower with no big effect. We charged it completely, removed the battery, and started the charge cycle again. It took about an hour for the charging light to go from red to green again. I don't know what that means, but it didn't look good. However, the capacity of the battery went down only 4 minutes. I don't think it was significant, but....
We will ship the iPower system with the UM450.
I can't stress enough that "YMMV".