MK Battery ES17-12 vs MK Battery ES17-12-X Performance Differences

Ordered batteries from MK, and got a new model number this year: ES17-12-X. Older ones are ES-17-12. New batteries have a different date code order, but appear to have the same specs.

The new batteries appear to have a different mold shape for the bottom of the casing.

Anyone know what the difference is between these two model numbers?

Contact them . They’ll respond. :wink:

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There was a thread on this a while ago and it was just because they were made my a different manufacturer. Specs are identical from that thread.

We’re getting pretty bad resistance readings from them. I wonder if this is a common issue for the alternate manufacturer.

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Contacted MK, they said the X should indicate that the batteries are produced in Malaysia. Non-x batteries should be produced in Vietnam.

They were stumped when I told them that both of our SKUs have Vietnam listed as their country of origin. TBD what the deal is there. They asked for a picture and said they’d call me back tomorrow.

I mentioned the high resistance reading, and they said they would likely replace them under warranty and provide non-X versions (though they don’t carry them in our local warehouses anymore).

Curious if anyone else has recieved X versions, and if they’ve noticed high internal resistance as well.

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Glad you called them and asked. Seems like good info.

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Our new ones are still in their boxes awaiting cable harnesses. I’ll look closely next time I’m at the shop. I am pretty sure they were prominently marked as made in Vietnam.

@Aidan-Mundy what were the resistance values you were getting on yours?

~0.020 with 2awg, 12" length tip to tip pre-stripping, and SB120 connectors. Using a modified battery beak that has a native SB120 connector. A non-modified battery beak with AndyMark SB50<->SB120 adapter showed ~0.022 so I know the problem isn’t my customized battery beak.

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MK Called back and told me that the X model is made in both Vietnam and Malaysia.

The only difference they claimed was a different factory, but the two countries of origin and different mold shape make me suspicious that there may be minor variations in the manufacturing process.

After a desulfating cycle on our Noco chargers, the batteries have come down to ~0.017 on the modified beak. I’d expect no higher than ~0.016 for new batteries, and typically target ~0.014 (without needing desulfation), so we may end up proceeding with a warranty replacement.

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Do -X and non-X batteries weigh the same? The KOP battery from a few years back weighed 10% less than all of our others, and performed rather poorly.

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Just say no to battery shrinkflation (not saying that’s what’s happening here, but it’s a legitimate concern).

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Using a 0.5 lb resolution scale (so not good, but definitely good enough in this case):

2019 ES17-12 consistently measured 13.0lb (> 12.75lb)
2021 ES17-12 consistently measured 13.0lb (> 12.75lb)
2022 ES17-12-X 1 consistently measured 12.0lb (< 12.25lb)
2022 ES17-12-X 2 measured either 12.0lb or 12.5lb depending on orientation (<= 12.5lb, likely ~12.25lb)

The X versions weigh at least 0.25lb less than the non-X versions. The difference is probably over 0.5lb, and may be close to 1lb depending on the rounding of our scale and the variance of the batteries.

I’m guessing at the rounding of the scale being in between the steps. I don’t have a better scale on hand that weighs in this range, and this is a small sample size, but I’d consider it to be conclusive enough for me.

Sadly, I think that is what’s happening here.

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Here we go again. We have 4 MK batteries inbound, and I hope they aren’t the X batteries.

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Can anyone from AM/REV confirm if the MK batteries they sell are the original part number or the new one? If so, is it possible for you to continue to carry the original, or has it been discontinued?

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@Greg_Needel I’m hoping to place an order for new batteries once the Canadian warehouse restocks, and this would be awesome to know ahead of time (also what REV’s policy is on potentially defective batteries from MK, or if any testing is done at REV before selling to teams).

Based on my conversation with the MK rep, the original part number has not been discontinued, but it isn’t widely available at the warehouses. I believe they listed NJ and 2 other states that had the original part number still, but that may not have been a complete list.

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These are the ones AndyMark is currently shipping. I don’t see a “-X” anywhere on the packing or the battery itself. This is the first we have heard of this issue and will keep an eye on the situation. I have also informed our purchasing department.

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Our batteries from andymark do not have an x. Their internal resistance measures fine as well. Have not weighed them.

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Warning, possibly a dumb question. How do you check the resistance of the battery? I saw mention of a modified battery beak up above. I’m pretty sure our team has a battery beak, but I’ve never used it so I’m not sure what info it provides.

Thanks in advance.

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The modified battery beak above was because that team was using a different size connector than the typical SB50’s most teams run.

A regular battery beak will tell you the internal resistance of the battery (and any attached leads/connectors).