I was told my P1A is heating up on high mode because the Energizer Ultimate Lithium are 1.6V. The Product Datasheet states they are 1.5V. http://data.energizer.com/PDFs/l91.pdf
The L91 is initially 1.6+ volts under NO LOAD conditions. In fact the Pulse Response test shows it can when new be as much as 1.8V no load voltage. Note that the 1.5V is listed as NOMINAL VOLTAGE but the graphs show how that varies with time and loads. Under the drain of a LED flashlight it falls rapidly to about 1.5 volts but under the same current draw the 1.5 volt alkaline battery drops to considerably lower than 1.5V as it has much higher internal resistance. The Ultimate Lithium can provide much greater voltage and current under high load conditions, as can the best quality NiMh rechargeable batteries such as Eneloops but the Eneloops do it at 1.2V nominal.
Download the E91 Alkaline battery PDF and compare them. Under any real current load the E91 falls on it’s face. The link is in the Specifications area on the L91 PDF you linked to in your post. The light gets hotter because the L91 is a much higher current capable device that SUSTAINS its nominal voltage under higher current drain conditions. It continues to allow the light to run at the output level that alkalines only provided for a few minutes or less.
I would like to share you comments on the Going Gear P1A YouTube video.
I have been concerned that the senior lady who will ultimately use the P1A light would have a problem using the P1A with the Ultimate Lithium Battery, She lives in a cold climate and the P1A might be left her her car for months at a time. After reading your comments I see that under the drain of a LED flashlight it falls rapidly to about 1.5 volts. I fell confident that the P1A will be able to be used with the Energizer Ultimate Lithium. No harm will come to the P1A or the senior lady.
Thank you so much for all your help. Your explanation was clear and concise. What an amazing forum.
Feel free to use my comments. In a cold climate the light might not work at all with alkaline batteries as their output capacity falls rapidly at low temperatures. The Ultimate Lithium batteries capacity versus temperature graph is included with the PDF you linked to. For an emergency light the Ultimate Lithium batteries are outstanding as their shelf life is up to 20 years. If annually recharged a set of low self discharge NiMH rechargeable batteries such as Eneloop rechargeable batteries are also good and work well at relatively low temperatures. Alkaline batteries in a emergency light are a poor choice as they tend to leak and corrode the light internals badly if left in a light for long periods. To me Alkalines are obsolete technology which survive due to being CHEAP! Even worse are carbon zinc batteries which are almost 120 year old technology and survive by being even cheaper!
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