When inserting the batteries they need to be at the same charge level ± few %, but that’s unavoidable for parallel cells. During operation it doesn’t really matter. If you insert very high quality cells with very low current capable cells, the high quality cells will have to handle almost the entire curren alone, so ideally the cells should be the same type. But that’s about it. No need to match capacity or IR, unlike for series connection lights.
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While I mostly agree with you, I think it important to highlight the rare possibility, when using lights with cells in parallel connection, if one cell develops a short, instead of just having to deal with it’s own internal energy, all of the connected cells will also dump their current into the cell… Rare but not an impossibility, I believe this is one of the reasons the DIY powerwall guys use cell level fusing.
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That’s a good point, and shows that deep discharged cells (which should not be used at all) must absolutely never be used for parallel lights again, as one of the main effects of deep-discharge is the formation of oxides inside the cells that may short them, sometimes even weeks or months after the deep discharge happened.
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Awesome, thanks for the information.
Just a tiny bit of confusion though about what you meant by “but that’s unavoidable for parallel cells” ?
Wrap bacon on it😂
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When plugging different batteries in parallel, the charge always has to equal out. So you get currents from one cell into another. There’s no reasonable way for the electronics to keep that from happening, that wouldn’t introduce a bunch of series resistance (and therefore, losses). So always charge all 3 cells to 100% before putting them in a parallel cell flashlight together. Then you’re golden.
If one is at 4.0V, one at 4.1 and one at 4.2, nothing bad should happen either. Just make sure not to plug one at 3.7 and one at 4.1 in together, for example.
Great, thanks again!
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@Simon_Mao I saw that you added the EVE 40PL battery to your store. I am very excited about this battery, and was wondering if you were going to add it as an option for flashlights. Also, how much would it cost then?
Last week I get M21A SFT40 with buck 8A driver.
I compare it with my good old M21A SFT40 with linear 6A driver and from tests I get conclusion that flashlight with linear 6A driver heats more and faster. But in practical use in night with tempearatures about 0 degs celsius with wind, I think that body of lamp cannot go more than 40-45 degs. I didn’t measured temps, this is my aproxymately subjective conclusion.
I must say that there are differencies between this two lamps because old model have smaller and cleaner hotspot with better corona than new model with buck driver. It is Convoy inconsistency with components but I must say that are minor differencies but I don’t like that when You don’t now for every purchase will You get the same characteristic for the same model of flashlight.
Also 8A buck driver has very short contact spring and I can’t use 18650 like I can with 6A linear driver model.
I’ve updated the battery option to the link for the flashlight.
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Sorry, I think I was unclear. What I ment was that when you buy a flashlight, you can choose a optional battery. I was wondering if the EVE 40PL would be added as one of those options?
L21B and some others have it already… Maybe Simon only added it to lights that can actually draw high currents, and not to lights that can’t really max this cell anyway.
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Okay, that makes sense. Thank you very much for the help!
Simon, I believe that’s a 4000mAh battery. The option to buy with the light shows 5000mAh.
Please correct it before someone buys it and complain to you later, and wants to give you trouble or something.
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If anyone is having trouble accessing https://convoylight.com/, I have learned that that site does not play nice with the Chromium-based extension Ghostery, so you need to disable that extension for Simon’s website. 
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Simon, is the silver L6 discontinued? All of the options for it are crossed out. Thanks!
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Hmm…
Maybe I’m wrong.
Sometimes, I’m still having trouble accessing Simon’s site and I have Ghostery disabled for that site.
@Simon_Mao Here’s a screenshot of what I frequently see:
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I’m seeing the exact same thing with the mobile Brave browser.
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Recently got one of Simon’s S6 lights with an sft40 and 18350 tube. It is a great little pocket rocket!
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It’s a site’s issue. Sometimes page’s markout gets broken and the main menu is shown in a wrong way. You can scroll down and there see main content.
This issue became oftent in recent days.
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