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Thread: High voltage 18650 pack

  1. #1

    Default High voltage 18650 pack

    Hi all, I'm wondering about the feasibility of building a rather high voltage 18650 battery pack.
    would need to be 670v and around 30a although only looking for 5-10 min of capacity. I'm thinking this isn't really feasible but currious what thoughts people have? Aside from the obvious high risk and related danger from that voltage level and power capacity I'm wondering what would be the other major issues? From what I've researched it would seem I likely need two cells in parallel with around 180 pairs in series, and that series cells need balancing circuits, I'm suspecting accomplishing the balancing for that many cells would be the main difficulty as well as the risk for a cascading failure?

    thanks

  2. #2

    Default Re: High voltage 18650 pack

    That would be ~190 18650's in series! Charging would be frightening and the positive cell would take a battering!!! And at 30A you'd be looking at vtc5a's or equivalent so 2300mah tops which at 30A would be around 5-6 mins of runtime. For a definite 10 mins runtime your gunna need nearly 400 cells! May not be feasible.
    What's it for?

  3. #3

    Default Re: High voltage 18650 pack

    Thanks for the reply, as for the application I have a 480v vfd drive I use to run large motors on various projects and stuff I have(like a tornado siren, another area of interest). Often I'd like to run these in remote locations, a generator is obviously the logical choice however they are large, noisy, etc. and I really don't need much run time at all so wanted to look into batteries to see if even possible. I think ideally I'd want 15 minutes but at a minimum 5, due to complexity and such probably leaning toward 5 for the purposes of consideration.

  4. #4

    Default Re: High voltage 18650 pack

    That's some serious power. If you were to do it I'd recommend pairs of 30Q's, that'd give you whatever your voltage and 6Ah rated for 40A continuous. 30A on 6Ah is 1/5hr, or 12ish minutes. Don't know if you can buy them in bulk, as $6 x 380 cells is very not cheap. Not to mention they'd weigh almost 40lbs without case/electronics.

    Possible? Sure. Feasible? Ehh, I don't know your budget/ how badly you wanna spin that siren

  5. #5

    Default Re: High voltage 18650 pack

    Yeah, the electronics are more the part I wasn't sure about, I had come up with about what you've stated about the batteries themselves but I have no idea as far as balancing circuits/charging that many batteries...

  6. #6

    Default Re: High voltage 18650 pack

    My bad- I missed that, and am lacking in this area of knowledge. I wonder if any sort of wrecked EV's in that voltage range get sent to a junkyard or the like? Maybe snag some sort of workable harness?

  7. #7
    Str8stroke's Avatar
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    Default Re: High voltage 18650 pack

    Kobalt has some 80 volt lion battery packs for their blowers. Get you 8 of those and wire them in series. Put some safety measures in place too. But, it would likely work.
    Interested in Saltytri lights. Pm me!


  8. #8
    BVH's Avatar
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    Default Re: High voltage 18650 pack

    Maybe a little less unfeasable to use RC type Lipo brick packs, maybe 4S/5000 mAh rated 25-30C. 670 / 14.8 (per pack) = 45 packs. They can easily sustain 10C (50 Amps) and would give about 5 minutes run time down to about 80% Depth of Discharge. At 30 Amps, you'd probably get 7 minutes run time. Cost about $45 each so around $2500 to your door. Buy an FMA Dual PowerLab 8 balancing charger, a 24V power supply and two parallel charging boards and you could balance charge 12 at one time - charge time of about 1 hour per 12. Charging system would cost about $500. With Lipo Bricks, there would be no spot welding tabs or more risky soldering of tabs onto 180 18650 cells, no special wiring for running the balance circuits and much easier to handle the fewer bricks. All of this is already factory-built into the setup I "built" above. Keep all the packs separate and connect when you need to use it. You could also get the same mAh capacity packs in 6S so only 30 needed. These are a little more volatile than the typical 18650 if not treated right. But if you're cautious, it is a reasonable risk. As a comparison, I spent about $1600 building my NightSun and Tank Light portable power supply for running the lights away from house power.

    http://www.candlepowerforums.com/vb/...ghtsun+battery

    Not sure why you say you need 670 Volts but in a later post, you mention 480Volt equipment?
    Last edited by BVH; 03-19-2017 at 07:58 PM.
    WWII 60" Anti Aircraft Carbon Arc (Sold), 1.6KW NightSun, 1KW VSS-3A, .8KW TrakkaBeam, 600W M-134 Gun Light, 500W X-500-14s, 500W Starburst, 500W Spectrolab A120b SA's, 300W Locators, Megaray, 150W Communicator, Maxabeam Gen3, Pichel 75W Mini-Novas, LarryK14@52V

  9. #9

    Default Re: High voltage 18650 pack

    So then the rc type packs, can those be seriesed in that quantity without any sort of regulating circuits between? I'm just thinking with the combined overal voltage level if any one cell or pack had an issue things could get exciting quickley.

  10. #10
    BVH's Avatar
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    Default Re: High voltage 18650 pack

    Yes, there are no "unique" issues with Series'd Lipo packs versus any other Lithium based packs. There is no need for any regulating circuits between any packs. But as with any pack you would build with that much Voltage, any issue can be significant. Over on RCGroups forum, a few year back, a guy used more packs than this to power his ultralight. It was a beautiful job and a beautiful machine. I think he flew it to Oshkosh from quite a distance. That would be a very good read thread for you to look at. I will try to find it and link it.
    Last edited by BVH; 03-19-2017 at 08:10 PM.
    WWII 60" Anti Aircraft Carbon Arc (Sold), 1.6KW NightSun, 1KW VSS-3A, .8KW TrakkaBeam, 600W M-134 Gun Light, 500W X-500-14s, 500W Starburst, 500W Spectrolab A120b SA's, 300W Locators, Megaray, 150W Communicator, Maxabeam Gen3, Pichel 75W Mini-Novas, LarryK14@52V

  11. #11
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    Default Re: High voltage 18650 pack

    Last edited by BVH; 03-19-2017 at 08:15 PM.
    WWII 60" Anti Aircraft Carbon Arc (Sold), 1.6KW NightSun, 1KW VSS-3A, .8KW TrakkaBeam, 600W M-134 Gun Light, 500W X-500-14s, 500W Starburst, 500W Spectrolab A120b SA's, 300W Locators, Megaray, 150W Communicator, Maxabeam Gen3, Pichel 75W Mini-Novas, LarryK14@52V

  12. #12

    Default Re: High voltage 18650 pack

    Okay, thanks for all the info! And yeah, as far as cost and such I will not be able to do this right now although now have an idea of what it would entail. I haven't really done much with battery powered systems in general so didn't have a good idea where to start with it

  13. #13

    Default Re: High voltage 18650 pack

    And looking through the drive manual it looks as though I don't need a voltage that high. I believe 420 is the minimum D.C. Voltage, so that helps

  14. #14
    BVH's Avatar
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    Default Re: High voltage 18650 pack

    So if you went with 6S packs, you'd need about 19 packs (422 Volts) which is more manageable than 30-6S packs or 45-4S packs. These are rough numbers using 3.7 Nominal Volts per cell - knowing that when you actually make the electrical connection to the device while the device is NOT running, overall Voltage will be higher until you introduce the load - 479 Volts. So you need to know that the device can withstand the higher 4.2 Volts per cell total voltage. If you get to this point, post again and I can help you work through the numbers and there are ways to overcome the difference between unloaded and loaded Volts.
    WWII 60" Anti Aircraft Carbon Arc (Sold), 1.6KW NightSun, 1KW VSS-3A, .8KW TrakkaBeam, 600W M-134 Gun Light, 500W X-500-14s, 500W Starburst, 500W Spectrolab A120b SA's, 300W Locators, Megaray, 150W Communicator, Maxabeam Gen3, Pichel 75W Mini-Novas, LarryK14@52V

  15. #15

    Default Re: High voltage 18650 pack

    The higher initial voltage will not be an issue. Acording to the manual the low voltage trip is 400+\-20v, and the high voltage trip is 790. I don't know that I'll be getting to this project that quickly (recently moved, not a lot of cash or a work area right now)but if/when I do I'll be sure to post the results here. Ohh, and previously you asked why the 670 for a 480v drive, I had not looked up my specific manual at that point and it seemed the common D.C. bus voltage of a 480v drive was 670 due to the rectification of the incoming ac. It seems my particular drive is made to be able to operate on foreign 380v systems up to 480v so it will except a larger input range. As an aside point, I'm thinking this battery pack could also run my searchlight project which I still havent finished as I purchased a more compact inverter welder which was also designed for 400v three phase input so the D.C. bus voltage should be the same as the drive. Thanks again

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