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#21
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Lithium Ion vs NiMh battery
On Mon, 23 Oct 2017 08:06:07 -0700, sms
wrote: On 10/22/2017 8:13 PM, Jeff Liebermann wrote: I recently bought a few of the lowest priced 18650 on eBay. Garbage in, lumens out. These were suppose to be 5800 and 5000 ma-hr but delivered 1000 and 880 ma-hr: http://802.11junk.com/jeffl/battery-tests/18650.jpg After about 10 charge/discharge cycles, the 5000 ma-hr cell is showing signs impending failure. Oh please, did you really expect 5800 mAH from an 18650? There is no such thing! Of course not. Notice that I said "bought a few of the lowest priced 18650 on eBay". I wanted to see how the worst possible cells preformed. These seem to be a fairly reasonable proposition. I haven't massaged the numbers quite yet, but it seems that a $1 junk 18650 battery, that produces about 1000 ma-hr capacity, has a lower cost of ownership than a $5 cell 2500 ma-hr from a reputable vendor. If I buy only junk batteries, I would get twice the capacity for the same cost, if I'm willing to ride with a bag full of spare batteries. However, early results from repeated charge/discharge cycles is showing that the junk cells don't last. The cheapest way to buy flat top 18650 cells is to buy one of those USB battery packs. Fry's has a 16,800 mAH model comprised of six 2800mAH 18650 cells for $17. That's $2.83 per cell. For button-top cells, the source that Barry Beams provided is probably the best option. I.e. for button-top https://liionwholesale.com/collections/batteries/products/protected-panasonic-ncr18650b-3400mah-li-ion-18650-button-top-battery?variant=1925834564. The prices are certainly tolerable, but only if the batteries are not counterfeit. That's the problem I had buying on eBay. I bought a few odd high priced cells, that were suppose to be name brand cells, and ended up with counterfeits. Of course, when I complained, the vendors refunded my money and claimed they didn't know that they were counterfeit. Incidentally, I usually weigh my 18650 cells. For a good battery, I usually end up with 45 grams/cell. One of the aforementioned batteries weighted an amazing 72 grams, was advertised as 3500 ma-hr and measured 800 ma-hr. I couldn't resist opening it up. Inside, I found what looked like the guts from a 14500 cell and a mixture of sand and wax to increase the weight. Another oddity is while 18650 cells are often market with wildly optimistic ma-hr ratings (much like flashlight lumens), other size LiIon cells seems to be marked with more realistic ratings. For example, I bought a pile of SkyWolfEye 14500 (AA size) cells marked 1200 ma-hr. They measure about 1100 ma-hr when tested at the industry standard 0.2C constant current discharge rate. However, at the 1A discharge, where I plan to use these cells, the best they could do is about 450 ma-hr. Still, if you use common 0.2C test method, they almost meet their advertised spec. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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#22
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Lithium Ion vs NiMh battery
"James" wrote in message news On 23/10/17 10:42, Sir Ridesalot wrote: Dynamo hubs are out for me because I use my light on a number of different bicycles depending on what any particular ride is for. It'd cost me afortune to a dynamo hub on all of my bikes. A first world problem of too many bicycles. I'm down to 2 and one with not a lot missing. |
#23
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Lithium Ion vs NiMh battery
"Oculus Lights" wrote in message ... On Sunday, October 22, 2017 at 1:07:26 PM UTC-7, Ian Field wrote: "Jeff Liebermann" wrote in message ... On Fri, 20 Oct 2017 21:40:42 -0700 (PDT), Sir Ridesalot wrote: A while back I asked about using an external NiMh battery instead of an external Lithium Ion battery on a light that came with a Lithium Ion battery. Due to a problem with the Lithium Ion battery pack of mine not holding a charge or for some other reason battery related for the light suddenly going out I put a Tamiya connector onto the light's wire and used my NiMh battery. Guess what? It works perfectly and my battery run time is a LOT longer now than what it was. Seeing as I have a few of these 5000Mah NiMh batteries from my RC boats I can now ride VERY FAR at night with no worry about the light going out suddenly or dimming drastically at low speeds or when stopped. My guess(tm) is that there is either something wrong with your LiIon battery pack, or the LiIon battery pack was assembled using cheap junk LiIon cells. I've seen both, mostly from 18650 cells. Identifying counterfeit cells is difficult: https://batterybro.com/blogs/18650-wholesale-battery-reviews/104619270-can-you-identify-the-fake-lg-hg2-18650-battery I used to weigh the cells and compare them with a known good cell, but that hasn't worked since the counterfeiters started adding waxes sand to the cell to increase the weight. All my 18650s were rescued from discarded laptop packs - if I get any duds, there's no point complaining to anyone. The 3W Tesco headlamp uses one, but my biggest application is my e cigarette. That's been in service well over 5yrs and I've only had to swap out a couple of battery sets. The one that came with the Tesco unit is only 1800mAh - I get a lot more running time from salvaged cells. Laptop battery packs used to be great sources for core cells. The big laptop battery recall in 07-08 sent case loads of new packs to large companies. Problem with the packs that was causing fires was cheap charging controllers, and poor design that put groups of three cells in parallel without regulating charging between each cell. That resulted in some cells being forced to absorb power beyond safe charging capacity if one cell was substandard or dropped off a tenth of a volt after many charges. Instructions were given NOT to return old packs, to dispose of locally. That gave me a huge harvest of 2800 Samsungs and Panasonics from Lenovo and Dell packs, for my early lights. I don't get it! - I use a simple DIY charger and never had an accident. Commercial manufacturers seem intent on comic people cartwheeling through the air. There's plenty of spectaculars on Youtube including people blowing up cells deliberately - I've never set out to do that, but I always "push the envelope" when exploring a new technology. Once I ruined an AA cell with my "brute force & ignorance" charger - but it didn't go exothermic. |
#24
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Lithium Ion vs NiMh battery
On 10/23/2017 10:53 AM, Ian Field wrote:
snip I don't get it! - I use a simple DIY charger and never had an accident. Commercial manufacturers seem intent on comic people cartwheeling through the air. If you're using protected cells you won't have any problem. It's also very different when you're charging two cells in series at 8.4V or one cell at 4.2V. You already have two levels of protection, the voltage is correct and the PCB in the battery doesn't let the voltage exceed 4.2V. At work, we had been charging unprotected cells with a variable power supply at 8.4V. This worked just fine. Except when we had a product that used a single cell and the tech hooked it up to the 8.4V--quite a mess when it exploded and caught fire on the bench. Commercial manufacturers are doing high-rate charging while monitoring temperature. They are also often charging in parallel but discharging in series, or a in series-parallel combination. |
#25
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Lithium Ion vs NiMh battery
"Jeff Liebermann" wrote in message ... On Sun, 22 Oct 2017 21:07:22 +0100, "Ian Field" wrote: All my 18650s were rescued from discarded laptop packs - if I get any duds, there's no point complaining to anyone. I have a small collection of such batteries. The problem is that the spot welded + terminal is flat and is missing the "button top" used in most removable 18650 cells. I had to buy a few magnetic "button tops" which work well enough, but are easily lost or misplaced: Active plumber's flux will allow you to tin the stainless straps, the spot welds have a fair bit of thermal resistance to the actual battery contact. Make the solder joint without dilly-dally and you don't cook the cell. The strong flux will also allow you to tin a M4 nut to solder on the + end. So far, I haven't had to - but I can if needed. Recover pack cells carefully - pulling the straps off completely can rip the spot welds out and leave holes in the steel jacket. Tin snips are the proper job, but scissors will do if you don't need them to cut anything else afterward. |
#26
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Lithium Ion vs NiMh battery
"sms" wrote in message news On 10/22/2017 8:13 PM, Jeff Liebermann wrote: On Sun, 22 Oct 2017 21:07:22 +0100, "Ian Field" wrote: All my 18650s were rescued from discarded laptop packs - if I get any duds, there's no point complaining to anyone. I have a small collection of such batteries. The problem is that the spot welded + terminal is flat and is missing the "button top" used in most removable 18650 cells. I had to buy a few magnetic "button tops" which work well enough, but are easily lost or misplaced: https://www.ebay.com/itm/282578704173 My testing, using a West Mountain Radio CBA-II discharge tester, showed that the cells market 2200 ma-hr delivered 2000 ma-hr at 1.5A. Good enough. The 3W Tesco headlamp uses one, but my biggest application is my e cigarette. That's been in service well over 5yrs and I've only had to swap out a couple of battery sets. Between the eCigarettes, eBikes, LED lighting enthusiasts, power tools, and radio geeks, it's a wonder that one can find 18650 cells. The one that came with the Tesco unit is only 1800mAh - I get a lot more running time from salvaged cells. I recently bought a few of the lowest priced 18650 on eBay. Garbage in, lumens out. These were suppose to be 5800 and 5000 ma-hr but delivered 1000 and 880 ma-hr: http://802.11junk.com/jeffl/battery-tests/18650.jpg After about 10 charge/discharge cycles, the 5000 ma-hr cell is showing signs impending failure. Oh please, did you really expect 5800 mAH from an 18650? There is no such thing! A laptop pack containing 3S1P claimed 5200mAh, but I never bothered verifying that it actually got that much work done. A recent find in the recycling was an Ultrafire 3600mAh 18650. It still had shrink wrap on it that covered the contacts - it was probably binned because the charger fault LED lit up. Its in my headlight right now, so I'm in the process of finding out how long it runs. |
#27
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Lithium Ion vs NiMh battery
"sms" wrote in message news On 10/23/2017 10:53 AM, Ian Field wrote: snip I don't get it! - I use a simple DIY charger and never had an accident. Commercial manufacturers seem intent on comic people cartwheeling through the air. If you're using protected cells you won't have any problem. It's also very different when you're charging two cells in series at 8.4V or one cell at 4.2V. You already have two levels of protection, the voltage is correct and the PCB in the battery doesn't let the voltage exceed 4.2V. At work, we had been charging unprotected cells with a variable power supply at 8.4V. This worked just fine. Except when we had a product that used a single cell and the tech hooked it up to the 8.4V--quite a mess when it exploded and caught fire on the bench. Commercial manufacturers are doing high-rate charging while monitoring temperature. They are also often charging in parallel but discharging in series, or a in series-parallel combination. Parallel charging for series use is probably as safe as it gets - I was considering designing something, but it seems to be one of those projects that doesn't quite evolve into something tangible. Series balancing isn't all that difficult - but I haven't quite cracked the "micropower" bit of the sensing circuits. |
#28
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Lithium Ion vs NiMh battery
On Mon, 23 Oct 2017 19:02:03 +0100, "Ian Field"
wrote: "Jeff Liebermann" wrote in message .. . On Sun, 22 Oct 2017 21:07:22 +0100, "Ian Field" wrote: All my 18650s were rescued from discarded laptop packs - if I get any duds, there's no point complaining to anyone. I have a small collection of such batteries. The problem is that the spot welded + terminal is flat and is missing the "button top" used in most removable 18650 cells. I had to buy a few magnetic "button tops" which work well enough, but are easily lost or misplaced: Active plumber's flux will allow you to tin the stainless straps, The strips are nickel, not stainless. Some are nickel plasted steel. http://www.ebikeschool.com/how-to-differ-between-pure-nickel-strip-battery-tabs-vs-steel-core/ the spot welds have a fair bit of thermal resistance to the actual battery contact. Make the solder joint without dilly-dally and you don't cook the cell. The strong flux will also allow you to tin a M4 nut to solder on the + end. So far, I haven't had to - but I can if needed. An M4 nut seems to be too thick for the purpose. The magnet is only 0.85mm thick. Recover pack cells carefully - pulling the straps off completely can rip the spot welds out and leave holes in the steel jacket. Tin snips are the proper job, but scissors will do if you don't need them to cut anything else afterward. I use diagonal wire cutters. I'll admit to ripping holes in the steel battery jacket, but I just plug them with solder. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#29
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Lithium Ion vs NiMh battery
"Jeff Liebermann" wrote in message ... On Mon, 23 Oct 2017 19:02:03 +0100, "Ian Field" wrote: "Jeff Liebermann" wrote in message . .. On Sun, 22 Oct 2017 21:07:22 +0100, "Ian Field" wrote: All my 18650s were rescued from discarded laptop packs - if I get any duds, there's no point complaining to anyone. I have a small collection of such batteries. The problem is that the spot welded + terminal is flat and is missing the "button top" used in most removable 18650 cells. I had to buy a few magnetic "button tops" which work well enough, but are easily lost or misplaced: Active plumber's flux will allow you to tin the stainless straps, The strips are nickel, not stainless. Some are nickel plasted steel. http://www.ebikeschool.com/how-to-differ-between-pure-nickel-strip-battery-tabs-vs-steel-core/ the spot welds have a fair bit of thermal resistance to the actual battery contact. Make the solder joint without dilly-dally and you don't cook the cell. The strong flux will also allow you to tin a M4 nut to solder on the + end. So far, I haven't had to - but I can if needed. An M4 nut seems to be too thick for the purpose. The magnet is only 0.85mm thick. Recover pack cells carefully - pulling the straps off completely can rip the spot welds out and leave holes in the steel jacket. Tin snips are the proper job, but scissors will do if you don't need them to cut anything else afterward. I use diagonal wire cutters. I'll admit to ripping holes in the steel battery jacket, but I just plug them with solder. There's probably an electrolyte contamination issue there, but i'm no chemist - so I'll leave if for you to look it up. Whatever the straps are made of - plumbers flux gets the job done. |
#30
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Lithium Ion vs NiMh battery
On Monday, October 23, 2017 at 11:01:42 AM UTC-7, sms wrote:
On 10/23/2017 10:53 AM, Ian Field wrote: snip I don't get it! - I use a simple DIY charger and never had an accident. Commercial manufacturers seem intent on comic people cartwheeling through the air. If you're using protected cells you won't have any problem. It's also very different when you're charging two cells in series at 8.4V or one cell at 4.2V. You already have two levels of protection, the voltage is correct and the PCB in the battery doesn't let the voltage exceed 4.2V. At work, we had been charging unprotected cells with a variable power supply at 8.4V. This worked just fine. Except when we had a product that used a single cell and the tech hooked it up to the 8.4V--quite a mess when it exploded and caught fire on the bench. Commercial manufacturers are doing high-rate charging while monitoring temperature. They are also often charging in parallel but discharging in series, or a in series-parallel combination. All of my speedos use 2032 cells. I used to just buy a card of them and insert new ones. Then I realized that they are Li-ion. Do these things charge up again? |
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