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Xtar’s E-cigarette Safety Shield (ESS) technology tested

Discussion in 'Batteries and Chargers' started by Mooch, Sep 8, 2019.

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  1. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    Also called E-cigarette Security Shield. This is the tech Xtar is putting in their newer chargers and, if I understand correctly, they are offering it (via licensing) to mod and charger companies. They have a short promo video, linked at the bottom of this post.

    The ESS module is basically just a cell DC internal resistance reading circuit. It measures how much voltage sag a cell has and the “brains” of the device, a charger or mod, can then decide what the maximum charging current should be limited to or what the highest power setting in a mod should be. It offers an extra level of safety for vapers using cells with too low a current rating or old/damaged cells. This is a good thing.

    I’ve seen the schematic and it is a wonderfully simple and elegant design, making it more affordable to include in more devices.

    Xtar is using it in their new chargers (like the ST2 I am testing now) and they sent me a separate prototype ESS module and a mod with an ESS circuit inside. Testing them against my DC internal resistance setup showed them to be surprisingly accurate if the contacts of the module’s battery sled or mod made good contact against the cell. No device trying to measure internal resistance can give you good results with dirty or juice covered contacts or contacts that press against the cell too gently.


    Here are my test results. Five measurements were taken for each battery for the ESS module and for the Xtar mod, removing the battery each time. As we use slightly different methods of measuring the DC internal resistance of a cell there will be differences in our results. But I was pleasantly surprised at how close they were.

    Panasonic NCR18650B
    My measurement = 52.7-53.1mOhms
    ESS module = 48-56mOhms
    Xtar mod = 48-53mOhms

    Samsung 25R
    My measurement = 18.1-18.5mOhms
    ESS module = 17-31mOhms
    Xtar mod = 14-20mOhms

    I did not expect our results to be the same as there is no standard for this kind of testing and you will get different results depending on how the device pulses the battery, what the battery temperature is, how charged the battery is, etc. My biggest concerns for any internal resistance measuring circuit/devices are consistency and not reading too low.

    The ESS module and Xtar ESS tech demonstrator mod did pretty well considering that both were rough prototypes. They were fairly consistent for the purpose of determining what a charge rate or power setting should not go over. A couple of the readings for the Samsung 25R were a bit lower than mine but I’m not concerned. The difference is small and, as mentioned earlier, we’re measuring the resistance in slightly different ways.

    There are several chargers on the market that measure DC internal resistance but some are quite inaccurate and extremely sensitive to the amount of pressure from the contacts.

    I hope to see this ESS tech, or something similar, used in more mods and chargers but I wonder if these other companies will want to pay for it. As long as Xtar keeps using it in their new chargers though then the community will benefit.

    For those who might be wondering...I am not receiving any kind of compensation from Xtar for this testing or for anything I post about this ESS technology. I’m just always interested in new tech, especially if it’s safety related, and this was exciting to hear about. I wanted to see how well it worked and I think they’ve done a good job!

    As with any technology its effectiveness depends on how well it’s implemented. If a company uses a circuit like this capable of great accuracy but then wires it badly or uses contacts that press too gently on the cell then the results are worthless.

    I want to work for the vaping community full time! If you feel what I do is worth a couple dollars a month and you would like early access to battery availability, battery and charger testing and news, and a say in what I test, then please consider becoming a Patreon patron and supporting my testing efforts: Battery Mooch is creating battery tests and educating vapers | Patreon

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  2. Rossum

    Rossum Surly Curmudgeon Verified Member ECF Veteran

    Supporting member
    Dec 14, 2013
    NE FL
    DNA boards have done this kind of thing "forever" (at least since the DNA20). The may not calculate milliohms, but they definitely monitor how much the battery voltage sags when the mod is being fired and produce "weak battery" messages if the sag is excessive for the power being drawn, so conceptually, it's the same idea.
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  3. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    Yup. A common circuit but the concept is not used nearly widely enough IMO. I’m just glad to see a China company promoting it as a separate feature worthy of its own discussion.
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  4. Heartsdelight

    Heartsdelight Vaping Master ECF Veteran

    Nov 10, 2015
    • Agree Agree x 1
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