Author: J. C. Boco
Date: 15:43:28 04/07/04
Go up one level in this thread
. > >What size batteries are you using? AA? AA batteries, 4 of them. If so, get yourself a NIMH charger and >some 2300mAH batteries. If you use AAA batteries get the same charger but some >750mAH or better batteries. These will put any commercial 'regular' battery to >shame. Before when playing chess on my Palm VII with normal batteries, I don't >remember any specific numbers but after a 6 or so hours w/ AAA batteries I would >get auto-shutoffs (or maybe even less time than that). After switching to 750mAH >AAA batteries it significantly increased the runtime. I could go a few days now >analyzing a position. I wonder if your palm is a device that demands a higher voltage, while a chess computer isn't as finicky. Let me explain-- I spent some time looking around learning about batteries. I learned that Li batteries last 100X as long as alkaline batteries in digital cameras, which are power hungry. However, the actual milliamp*hrs is only about 25% higher than the alkaline. That is, the total energy in the battery is only 25% higher in the Li, but then why does it last 100X????? Because of its discharge curve. An alkaline starts off at 1.5 V, and when it powers something its voltage starts to drop off rather quickly. Just as an example I'm making up for illustration, if you discharge only 20% of the batterie's power, its voltage could be around 1.2V. Now a dedicated chess computer may not care much, it can work down to 1V per battery. That dedicated chess computer can now run 4X longer. But that digital camera relies on higher energy drains to, say, charge the flash, or write to the memory card. The digital camera must stay near 1.5V per battery for it to work. Let's say you only discharge that alkaline 10%, so while it still has 90% power left it's voltage is, let us say, 1.4V. But the camera stops working when the voltage drops to 1.45V. Remember, these numbers are for illustrative purposes only. Now the Li batteries can discharge most of their energy without the voltage drop. Lets discharge a Li battery right now, lets drain 80 % of its power away. Only 20% left, but the camera still works because the Li chemistry keeps the voltage above 1.45V. You can get a hell of a lot more use out of the Li battery, perhaps a factor of 100X if you believe the advertisements, but only because of the level voltage/discharge curve. Actually, the Li battery only has about 25% more power, even though it runs the camera 100X as long. A chess computer can drain that battery down to let us say 1V. Whether it's an alkaline or a Li, it doesn't really care. I think battery life in a dedicated chess computer (which has low power demands) is mostly dictated by the total energy of the battery, its milliamp hours. Thus I think the Li battery would last only 25% longer than alkalines in this kind of low-power set up. The point of all that is that if I got that 2300mAH AA NIMH battery, I think it would only last 15% longer than the alkaline batteries (I think they are 2000mAH for "regular alkalines). I don't think NIMH will put my regular batteries to shame because they are in a chess computer. But if they were in a digital camera than I agree totally. > >I still wasn't satisfied (of course). :) So, I built an 'add on' pack to hold >two 2300mAH AA NIMH batteries. So the Palm VII is now powered with two 2300mAH >and two 750mAH batteries. I can 'forget' to turn off analysis, leave it go all >night and come back in the morning and the battery icon is still above 95%. With >general use it will last over a MONTH. The battery pack doesn't get in the way >either, just big enough to hold two AA batteries and is velcro'ed on the back. > >You can take a look at the batteries & chargers at www.thomasdistributing.com > >Here are the AA batteries I use: >http://www.thomasdistributing.com/lm-pro415-23.htm > >These AA batteries might be a little better as they're 2400mAH. >http://www.thomasdistributing.com/cta-4aa2400.htm > >This place doesn't have the AAA batteries I have but these are excellent (and >800mAH): >http://www.thomasdistributing.com/gp70aaahc-u4.htm > >The charger I have is this one: >http://www.thomasdistributing.com/maha-mh-c204f.htm > >With this combination you will not go wrong. I'm glad I have a nice NIMH setup >now, batteries at the store cost way too much now days! If you do any testing >with these definitely post the results here. I bought the Rayovac AA battery charger with the 2 incluced batteries, NIMH 2000mAHrs. Those ones that charge in 15 minutes. But I'm using them for something else...
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