by Doug Coulter » Fri Nov 12, 2010 10:38 am
Well, that's interesting and I concur -- there are definate quality differences, and probably some things that track capacity per volume. We used the Sanyo batteries in some hearing aid projects and they were indeed nice -- they were the only ones making them flat, square and other odd shapes that made them easier to package. Self discharge is only a problem in batteries not in use, what I'm looking for is use statistics.
I was really looking for data on things that really use batteries at some power level and beat on them hard -- like portable power tools, or laptops -- there you have no good choice other than to accept what the manufacturer gives you. Presumably they have tuned their chargers to suit their batteries as well. Most are claiming well over 300 cycle life, some as high as the 700's.
Is anyone getting that? I know I'm not, and the real numbers are very very nasty compared to the claims, which could be described as "outright lies" in most cases. In fact, I've never seen 700 full cycles in ones in products I've designed and tuned the chargers for that particular cell according to the manufacturers suggestions.
Ok, since it appears no one is paying attention -- here's more or less what I see.
NiCads in things like geiger counters -- weekly use, about one charge a month. 1 year. 12 cycles (sub C batteries)
NiCads in Ryobi drills and other tools -- two years, maybe one charge per two weeks. -- 50 cycles
NiMH in Makita tools (and this is an over $100 battery) -- three years, charged maybe every two weeks. ~ 75 cycles
Laptop LiIon -- haven't fried one yet, but then this lappy only runs on AC here. Maybe ran it down once.
Camera LiIon -- still going after 2 years, but never out of the charger and turned on more than about 10 minutes either.
Also an expensive battery only from Kodak, no substitution possible.
The above numbers are actually very optimistic -- some of the power tool batteries only see once a month or less frequent cycling, as I have a lot of them and a lot of tools that don't see frequent use. But it's bordering on a dollar per cycle! Heck, I can recharge alkaline batteries 3-4 times and they aren't meant for that! ( I have a charger that claims to do that correctly, and it seems to work about as well as reported above).
For another whole class of thing -- L-16 6v, 375ah lead acid, I get maybe 8 years in a solar system babying them as much as possible, as in "your life revolves around them". Very fancy 3 stage charging scheme, use most power when the sun is up (eg direct from the panels) and bypass them with smaller deep cycle batteries that take most of the peaks and die within a year doing that.
Usually 10% cycle/day tops, maybe really run them down once or twice in the entire life. I don't know the life of the Rolls-Surrette submarine batteries I'm using now, but they have a 25 year warranty and claim a few thousand cycles. We'll see on those, but I'm hoping they last for "life" eg mine. This is very high class stuff and they aren't cheap at all -- that bank I show in my solar system was about $6000 with a good discount.
I'll have to ask a friend who bought a Prius how his are doing. He takes better care of things than just about anyone, and mostly walks places anyway, doesn't use it to commute the 10 miles to his job, but uses a regular vehicle for that...Hmmm. Maybe not a good place to get a number, as he only uses that for longer trips (eg, very little use of the battery).
Of course, warranty on anything is only good for the life of the company giving the guarantee, and an old trick in the car battery business was to "go out of business" and change the company name to avoid paying warranties. The discount auto batteries companies would do this about once a year and pop right back up with one letter of the company name changed.
And when I declare them dead, it's not because they have half capacity. They are DEAD and maybe will run the device for 5 minutes off a fresh charge, if that.
Anyone else seeing this sort of "dollar per use" kind of numbers? I've had much better luck with AA nicads or NiMH in low draw use, like cameras, but still not very good.
Now the Makita batteries are so expensive (so as to even be hard to find, stores don't want that much bucks in inventory laying around) I will take them apart and replace the cells with ones from DigiKey soon, but even that won't be cheap. But I'm not going to toss out a $275 drill because of that -- it's a very good tool.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.