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Re: Poundland Kodak Batteries
[Re: Littlebear]
#1050695
30th Dec 2017 10:03am
30th Dec 2017 10:03am
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Joined: Jan 2010
Posts: 1,795 wirral
Excoriator
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Joined: Jan 2010
Posts: 1,795
wirral
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Personally, I hate batteries. They invariably let you down when you need them and take hours to recharge or pounds to replace. So I have replaced them in my portable hand drill with supercapacitors. This is a bit bulkier and requires a separate box to contain them, and holds far less energy. These are major disadvantages, but I find them more than outweighed by the fact that they do not lose capacity, degrade, and - by charging them at 40Amps- they can be fully recharged in 20 seconds. I will, this summer, also use them in our narrowboat to start the diesel. At present there is a starting battery and a leisure battery. I can replace the starting battery with supercapacitors, which will give me two leisure batteries. The supercapacitors can be charged relatively gently from the two leisure batteries, along with the glowplug current, and will supply enough current (1200 Amps) for the short time needed to turn the engine over. Half a dozen of them - they are roughly the size of a 'D' cell - does the job a treat. Here's a video of a Canadian guy who uses them in a car. https://www.youtube.com/watch?v=z3x_kYq3mHM
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Re: Poundland Kodak Batteries
[Re: Littlebear]
#1050702
30th Dec 2017 7:51pm
30th Dec 2017 7:51pm
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Joined: Jan 2010
Posts: 1,795 wirral
Excoriator
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I designed and got made some little PCBs to protect them from overvoltage. These worked OK on the ones on my drill. Above a certain voltage (2.6v) they open a current shunt around the cell. In the ones for my boat they came with a PCB that did the same thing so I was saved from worrying about it. I doubt there is much chance of reverse voltage during discharge. They are all about the same value and are unlikely to go down to a very low voltage.
Like a twit, I managed to reverse the voltage on them for about 10 seconds the first time I tried to charge them and they all survived OK, so I guess they are not all that sensitive anyway.
They are specified to charge and discharge at 1200 Amps so I assume they will not be damaged by currents up to this. I can't measure currents of that size but I suspect that the engine on my boat takes a lot less than that anyway. They retain enough charge for perhaps half a dozen start attempt which implies perhaps about 200A.
I use 350F ones for the drill. For the boat, I got 500F ones which are a bit longer than a 'D' cell. They are all amazingly light though. From memory about 60 grams each (In both cases I have six in series).
My biggest problem was the charger for the drill. You can buy 40A switch-mode units on Ebay at reasonable cost, but they are current protected in 'hiccup' mode. When they are connected to the supercaps it looks like a short so they shut down and try again repeatedly. I had to open them up, trace the circuit and add trickery to make them supply 40A even into a short circuit, which was a right pain in the arse to do. Still, it's been working for some years OK now.
They seem to be extremely rugged. I once tried to discharge a similar one with a screwdriver across the terminals. It went to red hot, then yellow before I could get it off and was never the same again. The supercapacitor seemed utterly unharmed. They are supposed to work down to -40C but I haven't verified that.
Certainly a lot better than Ni-Cd and safer than Lithium.
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Re: Poundland Kodak Batteries
[Re: Excoriator]
#1050704
30th Dec 2017 8:40pm
30th Dec 2017 8:40pm
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Joined: Jul 2008
Posts: 14,116 Birkenhead
diggingdeeper

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Joined: Jul 2008
Posts: 14,116
Birkenhead
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I doubt there is much chance of reverse voltage during discharge. They are all about the same value and are unlikely to go down to a very low voltage. Yes, that's an advantage I hadn't appreciated, all the capacitors will be dropping towards 0V at roughly the same rate instead of the more stepped drops of batteries that creates a cliff edge. Bad luck on the power supply having had over-current protection rather than dropping into constant current mode. Reverse engineering switch mode power supplies can be a real pain, I guess specialist IC's make them a bit simpler than the discrete days of old. The power supply reminds me that I need to dig out the parts I got for a 300W led lighting project, off-the-shelf Chinese constant current modules were far cheaper (and tidier) than anything I would build. I needed a ripple-free high power lighting source for slow motion video, unfortunately the camera developed a mechanical fault inside its lens/sensor assembly and I've not had a bench empty enough to do surgery as yet.
We don't do charity in Germany, We pay taxes. Charity is a failure of governments' responsibilities - Henning Wehn
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Re: Poundland Kodak Batteries
[Re: Littlebear]
#1050708
30th Dec 2017 9:28pm
30th Dec 2017 9:28pm
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Joined: Jan 2010
Posts: 1,795 wirral
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Much as I dislike them, I am forced to use batteries for a hand torch I use for after-dark dog-walking. The torch is a Chinese LED one and came with cheap 18650 batteries optimistically marked 3,400mAh.
They were nothing like this capacity, of course. An example of a Chinese sense of humour perhaps, but eventually, I got pissed off with them and bought some decent 'Nitecore' 3,400mAh ones at about Ł12. Expensive, but worth it. They seem to last forever without my having to recharge them.
I think you certainly get what you pay for sometimes. The difference is dramatic. I bought two and keep one charged and ready whilst the other one is in the torch. I am nervous about them nevertheless, and never leave them on charge at night or when I am out of the house. I also keep the standby one in a hopefully fireproof steel box sitting on a tiled floor.
A friend of mine is keen on radio controlled gliders, and told me of one of his colleagues who - whilst they were flying - stuck a lithium battery in his jacket pocket. A minute or two later, and he had smoke and flames belching from his jacket and was very lucky to get out of it without serious burns.
I really don't trust the things!
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