and RC time.
its own.
Read further down that page: " A single cell driving a load won't suffer from polarity reversal, because there are no other cells to reverse-charge it when it becomes discharged. Irreversible damage from polarity reversal is a particular danger in systems... " Single cell discharge is not the problem, it's the cell reversal in battery packs that kills the weaker cells that discharged first.
Grant.
On a sunny day (Sat, 07 Aug 2010 08:20:59 +1000) it happened Grant wrote in :
I/O and RC time.
its own.
Yes, polarity reversal is bad. But total discharge is also bad, this does not nullify that. But if you are so sure will you pay for new cells if I damage these ones by leaving them connected to a load till it reads less then .5 V? I though not.
If you are so sure why does my singe cell Muvo (Creative Labs) mp3 player has a power down feature if the battery voltage drops below some level? Creative realy know what they are doing. Maybe that is why these AAA it runs on have already had several hundred charge cycles and are still just fine.
Anyways, I found a nice solution with a MOSFET that also creates a touch switch on-off system, so perfection is here :-) See my other post for the ASCII diagram. Usenet Patent of course.
I/O and RC time.
of its own.
power down
cycles and are still just fine.
Probably my memory of the NiCd cells? They don't mind going to zero? I have lost NiCd and NiMH cells due to over-discharging when there's two or more, but I have one device here (old beard trimmer) that uses a single NiCd cell and is decades old, still works ;) Anything with two or more cells seems to go trash sooner rather than later. Except the camera, it runs a pair of AA and has low voltage shutdown at around 1V/cell.
on-off system,
Yes, I saw that. I'm likely to try something that you and Tim cooked up together :)
Grant.
I/O and RC time.
of its own.
a power down
cycles and are still just fine.
No such animal in modern NiCads, at least not as such.
No, =0 is fine, < 0, not so much.
Right. This point should be chosen depending on the number of cells. With more cells this point has to be set higher.
switch on-off system,
me I/O and RC time.
er of its own.
minal
rther
I think they're talking about multiple cells in series--batteries--not cells. The next Wiki paragraph (on "over-discharge") clarifies that the danger is not over-discharging but polarity-reversing the cell. That's possible with batteries, not with single cells.
Would the manufacturer's literature carry any weight with you?
See sections 5.3, 5.6, and 5.8.
Summary: Cells are not damaged by 0v, and can be stored without damage in the zero-volt condition. Party on!
-- Cheers, James Arthur
A synchronous rectifier saves half that, but at unreasonable added complexity and expense. It's not usually worth it.
On a sunny day (Sat, 7 Aug 2010 14:35:08 -0700 (PDT)) it happened snipped-for-privacy@yahoo.com wrote in :
First I want to thank you for that nice pdf link,. As I use Duracell (among other batteries) it is good info to have. How much I would like to agree with you, because it would make the design simpler, the 1.0 V discharge limit is all over that pdf. And consider this quote from page 19, it sort of confirms what I wrote about my single cell mp3 player that has a cutoff, Cycle life is also affected by the depth of dis- charge. Depending upon the charge termination method, up to 500 cycles can be obtained with the battery being fully discharged on each cycle (100 percent depth of dis- charge, or "DOD"). Considerably higher cycle life can be obtained if the battery is cycled at shallower charge/ discharges.
In the end product there is of course also the possibility that somebody puts in a normal not rechargeable, so it would make sense to not discharge that to the leaking point.
simpler,
e that to the leaking point.
Yes, you get more cycles if you reduce the depth of discharge, but ISTM the limiting factor in most real-life applications today is getting fried a little every time they're charged. (I haven't seen a charger yet that comes close to table 7.2.1's recommended temperature limits.)
So, with available chargers you might get better life using the full charge and recharging a cell fewer times. Any which way, full discharging and 500 cycles is nothing to sneeze at...
-- Cheers, James Arthur
On a sunny day (Sat, 7 Aug 2010 18:06:52 -0700 (PDT)) it happened snipped-for-privacy@yahoo.com wrote in :
I have two original Duracell chargers that accept both AA and AAA, So the ball is in their court so to speak.
Also, the voltage converter in the circuit will not work correctly below .9 V or so, the output voltage will drop below 3V and the PIC's brownout detector comes in at 2.85V... I am testing using the brownout detector to switch of the battery, that works, but is messy (the relationship with the real battery voltage is 'vague'. Next I will try using the PIC's internal analog comparator and internal reference voltage as low battery voltage detector. The internal reference has some tolerance too, need to do some calculations. Just to get rid of a trimpot...
It seems to me, that if you only discharge to the point where the circuit still just works OK, you not only get more battery life (cycles), but also need less charge time :-). And less frustration 'because it does not work right (because of low battery)', better switch it off completely forcing the people to put in a fresh battery.
dy
arge
.9 V or so,
f the battery,
is 'vague'.
eference voltage as low battery voltage detector.
ns.
still
less
cause of low battery)',
ery.
The NiMH cell is pretty close to empty when it hits 1.20v, and has only a percent or two of its energy left at 1.10v, so I'd count those both as "full discharge" as far as affect on the longevity of the cell. You just don't have to worry that these levels or lower will outright damage your cell--they won't.
You might well want to cut off earlier for other reasons, like to give the user some warning before the thing dies. If these voltages were accurate and temperature stable (which they aren't) I'd warn at 1.20v and cut off around 1.15v on an NiMH cell, and run alkalines down to
1.0v.Wondering what other designers do, I started picking up AA cells people toss on the road. They're usually 1.3v, only 20% used for an alkaline cell.(*) That's a sin. If we're going to condone toss-aways we ought to at least use them fully, don't you agree? Keeps them off the road, out of the waste stream, and the user enjoys the longer run time too. Win-win.
(*)(e.g.
Whether it's better to get 500 full cycles from an NiMH or 1,000+ half- cycles? That's up to you of course.
-- Cheers, James Arthur
On a sunny day (Sun, 8 Aug 2010 05:49:19 -0700 (PDT)) it happened snipped-for-privacy@yahoo.com wrote in :
outright damage your cell--they won't.
I did some test today, and ended up using the PICs internal Vref of about 1.024V and its internal analog comparator to drive the MOSFET battery switch. You can program that comparator to have some hysteresis. It now needs a little bit above 1.0 V to keep working. Switches of nicely, and the tolerances according to the PIC datasheet of that reference voltage are not bad at all. I put in a fresh charged 2300mAh NiMh and it is running now. Will see how long :-) It is a 2 component solution, MOSFET + 1 resistor.
Yes, exactly.
Do not alkaline sort of go back up after you remove the load? Zi effect? May read 1.3 but could well read 1 V in a camera for example with a lot of current charging the flash capacitor.
If the thing does not work right on an almost empty battery then 1000 is the best choice :-)
ys
f current charging the flash
Roadside batteries come mostly from joggers and MP3 addicts. Apparently joggers run on AA cells.
-- Cheers, James Arthur
current charging the flash
best choice :-)
It varies so much, my canon A580 camera reports Alkaline cell low too early, and doesn't like any but the best NiMH cells. So one can go on to take a few dozen shots sans flash (in warm weather) on alkaline before the cam packs it in and tells one to replace the battery.
On NiMH it's only a few shots before death, battery is measured on load too.
Some stuff on canon A590, now sadly expired, too expensive to fix.
Written up just over a year ago, examines power behaviour of A590 2 AA cell camera, probably roughly applies to other Canon models designed for 2 cell operation.
Grant.
On a sunny day (Sun, 8 Aug 2010 14:13:41 -0700 (PDT)) it happened snipped-for-privacy@yahoo.com wrote in :
They wont get far that way :-)
On a sunny day (Mon, 09 Aug 2010 07:15:58 +1000) it happened Grant wrote in :
best choice :-)
I have a canon A470. Same story, but my NiMH holds out a bit longer. I have never used it with non-rechargeables. It sometimes reports empty, and that message then goes away after taking a lot of pics, beats me. If you do not frequently take pictures, the low capacity NiMH last longer and have a lower self-discharge. That means you wont face an empty battery when you need the camera. My Duracell 2500 mAh are empty if left for a week or so, in this camera. The Duracell 1700 mAh just lasts for several weeks, so I only use those. There also exist 'Eneloop' batteries, those are NiMH that keep 85% charge for almost a year, have slightly less capacity too, ideal if you only take pictures every now and then. What it all boils down to, is that I always have some NiMH in the chargers, with
2 chargers running 24/7. Then I have the Li-ion batteries for other camers too.. Then the laptop is charging. Also have a huge sealed lead-acid on backup charge. :-)
'soft'
Hate to be picky but that efficiency is really poor, 240 mW in and 150 mW out. Maybe try a more standard boost configuration.
They keep going, and going, and going...
a 'soft'
I don't see the appeal compared to lt1110 - twice as many parts including a custom transformer plus lower efficiency. Not really a winner in my book.
You're confusing joggers, with dimbulb. :(
You couldn't get any light out of DimBulb with all the EverReadys on the planet.
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