"MartinM" <[email hidden]> wrote in message news:[email hidden]
Quoted message said:
I see Maplin do a Li-Ion rechargable pack (meant for camcorders but prolly adaptable) which is 2Ah, seems a good trade off between weight and capacity.
Not a good idea - LiIon batteries have a tendency to explode if not handled and treated in accordance with guidelines - one thing they don't like is deep current draw and vibration.
OK thanks. Out of interest does anyone know what the actaul capacity of the various alkaline D cells on the market is? (the are very secretive on their packaging).
In my experience, AA Duracells used in an incandescent bike light or a digital camera are only about 1200mAH. Basic NiMH cells can equal their performance. The D cells should be much better, and most big name NiMH D cells don't take advantage of the larger size to increase capacity. There are AA and D cells in 2500mAH, for example. I suspect the D cell has the same innards as the AA - its only advantage being that it will fit things that require that size.
"Chris Eilbeck" <[email hidden]> wrote in message news:[email hidden]
Quoted message said:
Lithium polymer are fine under those circumstances though.
Highly debatable. I was looking into the technologies and did a little research, the horror stories are remarkable.
LiPo batteries from Kokam, Thunderpower etc. are designed for very high discharge rates, 15-20C, and for use in model aircraft. This situation far exceeds the duty expected of a battery driving a lighting system on a bike. True, there can be dangerous problems associated with lithium batteries but from what I can tell these are brought about by either impact damage or excessive charging and discharging. I've been using lithium batteries for almost the last 15 years, from coin cells to 300Ah packs, and I've never had a problem despite what sometimes appears to be deliberate abuse by some of my users.
"Chris Eilbeck" <[email hidden]> wrote in message news:[email hidden]
Quoted message said:
Lithium polymer are fine under those circumstances though.
Highly debatable. I was looking into the technologies and did a little research, the horror stories are remarkable.
LiPo batteries from Kokam, Thunderpower etc. are designed for very high discharge rates, 15-20C, and for use in model aircraft. This situation far exceeds the duty expected of a battery driving a lighting system on a bike. True, there can be dangerous problems associated with lithium batteries but from what I can tell these are brought about by either impact damage or excessive charging and discharging. I've been using lithium batteries for almost the last 15 years, from coin cells to 300Ah packs, and I've never had a problem despite what sometimes appears to be deliberate abuse by some of my users.
Chris
Aren't lithium-polonium batteries a little, err, dangerous? -- Chris
"Inform all the troops that communications have completely broken down."
"Chris Eilbeck" <[email hidden]> wrote in message news:[email hidden]
> Lithium polymer are fine under those circumstances though.
Highly debatable. I was looking into the technologies and did a little research, the horror stories are remarkable.
LiPo batteries from Kokam, Thunderpower etc. are designed for very high discharge rates, 15-20C, and for use in model aircraft. This situation far exceeds the duty expected of a battery driving a lighting system on a bike. True, there can be dangerous problems associated with lithium batteries but from what I can tell these are brought about by either impact damage or excessive charging and discharging. I've been using lithium batteries for almost the last 15 years, from coin cells to 300Ah packs, and I've never had a problem despite what sometimes appears to be deliberate abuse by some of my users.
Aren't lithium-polonium batteries a little, err, dangerous?
Like I say, only if you pierce them, over charge them, or allow them to discharge at too high a rate or discharge too far. Everything can be dangerous if you misuse it.
Chris -- Chris Eilbeck MARS Flight Crew http://www.mars.org.uk/ UKRA #1108 Level 2 UYB Tripoli UK Member #9527 LSMR
-- Sent from Birmingham, UK timdunne at blueyonder.co.uk 'God's electrician sparked up the heavens once again, heading northbound on the 7:10. And the lord said let there be commuters...' - Thea Gilmore Look, mum, an anorak on a bike! Check out www.nervouscyclist.org
"Zog The Undeniable" <[email hidden]> wrote in message news:43da914b.0@entanet
Quoted message said:
That's not a bad capacity for AA and it's an amazing capacity for D (if it's true). With 4 "D" cells you could run a 2.4W front lamp for a whole Dunwich Dynamo.
"Chris Eilbeck" <[email hidden]> wrote in message news:[email hidden]
Quoted message said:
Like I say, only if you pierce them, over charge them, or allow them to discharge at too high a rate or discharge too far. Everything can be dangerous if you misuse it.
So, in short, they're not for amateur use without protective ciruitry, and are still dangerous on impact. I rest my case...
:o)
Tim
-- Sent from Birmingham, UK timdunne at blueyonder.co.uk 'God's electrician sparked up the heavens once again, heading northbound on the 7:10. And the lord said let there be commuters...' - Thea Gilmore Look, mum, an anorak on a bike! Check out www.nervouscyclist.org
"Chris Eilbeck" <[email hidden]> wrote in message news:[email hidden]
Quoted message said:
Like I say, only if you pierce them, over charge them, or allow them to discharge at too high a rate or discharge too far. Everything can be dangerous if you misuse it.
So, in short, they're not for amateur use without protective ciruitry, and are still dangerous on impact. I rest my case...
Some protection may already be built in. Vibration or any impact they're likely to get isn't a problem for Lumicycle Li-Ion batteries -- which I doubt are incredibly special.
"Jim Ley" <[email hidden]> wrote in message news:[email hidden]
Quoted message said:
Quoted message said:
So the cycle mounts for mobile phones have something to deal with this, or do they all come with, your phone may explode warnings?
Quoted message said:
Why should they? The people who make cycle mounts wouldn't care - do you think it's a good idea to subject a mobile to that kind of vibration anyway? I've dropped a medical Li-ion pack at work and very nearly been badly burned in the resultant flare-up.
Quoted message said:
Do a google, this isn't trivial.
And the mobile phone newsgroups have stories of abused Li-on phones exploding.
-- Chris Malcolm [email hidden] +44 (0)131 651 3445 DoD #205 IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK [http://www.dai.ed.ac.uk/homes/cam/]
OK thanks. Out of interest does anyone know what the actaul capacity of the various alkaline D cells on the market is? (the are very secretive on their packaging).
Quoted message said:
Not so much secretive, as the answer can't be usefully quantified in most cases. The useful (or apparent) capacity is strongly dependant on the drain current, and somewhat dependant on service conditions and duty cycle. They could quote a value, but it may or may not actually resemble what you actually get.
Quoted message said:
Your best bet is to peruse information intended for commercial users. I find Farnell to be a good source for data sheets. For example, at http://www.farnell.com/datasheets/31104.pdf you can find families of curves for Duracell Ultra M3 D cells.
Quoted message said:
Typically, upper-end alkaline D cells are in teh 15-18 Ah range.
THe problem with D-size rechargeables is most of them aren't Ds: they're AAs or Cs in a bigger tube, which you can tell by weighing them. Real full size Ds are expensive, and are *large* capacity.
-- Chris Malcolm [email hidden] +44 (0)131 651 3445 DoD #205 IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK [http://www.dai.ed.ac.uk/homes/cam/]
THe problem with D-size rechargeables is most of them aren't Ds: they're AAs or Cs in a bigger tube, which you can tell by weighing them. Real full size Ds are expensive, and are *large* capacity.
And are heavy.
-- Tony
"The best way I know of to win an argument is to start by being in the right." - Lord Hailsham
"Chris Eilbeck" <[email hidden]> wrote in message news:[email hidden]
Quoted message said:
Like I say, only if you pierce them, over charge them, or allow them to discharge at too high a rate or discharge too far. Everything can be dangerous if you misuse it.
So, in short, they're not for amateur use without protective ciruitry, and are still dangerous on impact. I rest my case...
:o)
Amateur use in things like laptops, PDAs, power tools, mobile phones?
"Chris Eilbeck" <[email hidden]> wrote in message news:[email hidden]
Quoted message said:
Amateur use in things like laptops, PDAs, power tools, mobile phones?
Power tools? Name one...
Whilst I suspect my PDA was designed by an amateur[1], it was made by HP and incorporates suitable protection circuitry, as do the other devices you mention. Li technology is nowhere near as simple as NiCd/NiMH or Pb, and design for it requires a degree of specialised knowledge - the kind an amateur is unlikely to have.
Tim
-- Sent from Birmingham, UK timdunne at blueyonder.co.uk 'God's electrician sparked up the heavens once again, heading northbound on the 7:10. And the lord said let there be commuters...' - Thea Gilmore Look, mum, an anorak on a bike! Check out www.nervouscyclist.org
Whilst I suspect my PDA was designed by an amateur[1], it was made by HP and incorporates suitable protection circuitry, as do the other devices you mention. Li technology is nowhere near as simple as NiCd/NiMH or Pb, and design for it requires a degree of specialised knowledge - the kind an amateur is unlikely to have.
How difficult is it to put a fuse in something? How difficult is it to use a charger specifically designed for that type of battery?
Chris -- Chris Eilbeck MARS Flight Crew http://www.mars.org.uk/ UKRA #1108 Level 2 UYB Tripoli UK Member #9527 LSMR
"Chris Eilbeck" <[email hidden]> wrote in message news:[email hidden]
Quoted message said:
How difficult is it to put a fuse in something? How difficult is it to use a charger specifically designed for that type of battery?
I suggest you read a little on the subject. It's more than just a fuse.
Sin
-- Sent from Birmingham, UK timdunne at blueyonder.co.uk 'God's electrician sparked up the heavens once again, heading northbound on the 7:10. And the lord said let there be commuters...' - Thea Gilmore Look, mum, an anorak on a bike! Check out www.nervouscyclist.org
-- Sent from Birmingham, UK timdunne at blueyonder.co.uk 'God's electrician sparked up the heavens once again, heading northbound on the 7:10. And the lord said let there be commuters...' - Thea Gilmore Look, mum, an anorak on a bike! Check out www.nervouscyclist.org
So, in short, they're not for amateur use without protective ciruitry
Quoted message said:
Amateur use in things like laptops, PDAs, power tools, mobile phones?
They'd have the protective circuitry built in.
Don't kid yourself! Just because something is designed by someone "professionally", it doesn't mean it's really safe even if it does have CE marking. In portable devices there often just isn't the space.
I've got an Electron 5W/10W system which uses a NiMh pack and the charger for that is a very basic constant voltage power supply ie a transformer, a bridge rectifier and a capacitor. This is absolutely the wrong way to charge a NiMh pack and has no safety features, no fuse, no thermal trip, nothing at all other than a warning not to charge the pack for more than 20 hours.
Anything sold commercially like this is designed down to a price, any measures to enhance its safety will have been weighed against the potential cost of claims made against the company for its failure in a dangerous manner.
