Imren 18350 LiIon Cell Review

I’ve tested some 18350 cells, but I asked for this cell specifically because it’s an inexpensive option, and has a button top, too.  Both of those are things a user might need, so it’s good to have these tested.  These cells surprised me a little, and I think the graphs will be a useful addition to my data!  Read on!

As always, click for bigger images!!  See the new graph format, too.  I used edited my previous cell review with this same format, but I sort of slipped that edit in later.  I rearranged the graph so that the legend doesn’t cover any data, among other changes.  Hope it’s good.  If it is let me know!  If it isn’t let me know!


Official Specs

Here’s a link to the Imren 18350 product page at liionwholesale.  I can’t find the product on Imren’s official site, so that one will have to do.

Price

Currently these are $2.99 per cell, with volume discounts starting at 3 cells.  Buy them at LiIonWholesale.com!

Short Review

These cells will be ok for very low discharge use cases.  They could be useful if you really need button tops.  They’re ok for the price.

Long Review

Package

Build

The Imren sticker attached to the blue wrapper isn’t all that sticky, and seems to want to roll up on the edges.  Probably these will end up getting pulled off, and I’ll write what the cells are in Sharpie on the blue label.  

Size

These are 18350 cells, but that measurement (18mm x 35mm) is for the base cell – the unprotected flat top.  The cell as presented has (at least) a button added (but likely no protection circuit).  So this one will be a little longer than 35mm!

Testing

I’ve tried to keep the scales similar, so over time the charts will be generally comparable.  These scales are specific to 18350 cells.  

Discharge tests

Capacity

These cells are rated at 800mAh, and as the tests show, easily surpass that.  Even up to 1A discharge (much higher than the usual 0.2A spec for LiIon cells, though this cell doesn’t have a datasheet), the cell still provides over 800mAh.

But also do note the disparity after 3A.  Higher discharges than 3A really drop off in performance, exhibited here by an extremely diminished capacity.

Energy

Bounce

“Bounce back” is what the cell voltage does when the cell rests after a discharge. After heavy discharge rates, the cell voltage bounces back higher when discharge is stopped.  This corresponds to a discharge amount of less energy, and does mean that there’s energy left in the cell.  So if I selected the cell with the highest bounce back voltage (ie the cell that was discharged at the highest current), then discharged it to 2.8V at 0.2A, I’d still find that there was a lot of energy still in the cell. 

Here is why I think it so interesting about “Bounce.”  A poorly performing cell will bounce back higher after high discharges.  That’s because the IR is higher, and because the cell performs much worse under high loads.  So a good performing cell will bounce back much less because it’s much more capable of high discharge.  At high discharge on a capable cell, more of the energy makes its way out of the cell!  Hence less bounce. 

I more or less figured this out on my own, so I welcome discourse about this topic.  Until I hear it’s wrong, I propose this as a new metric for cell quality!

Please also note, after all the text above, this cell is a good example of Bounce showing the cell isn’t performing well.  Under high loads (even moderate loads, to be honest), the cell bounces back fairly high.  And at the highest tested discharge (9A on just one cell, 8A on both), the voltage drops to the cutoff almost immediately, and then immediately bounces back to almost the starting point.  

Charge Test

Temperature

Temperature here is going to be meaningless – the discharge at the highest currents was so short that the cell wouldn’t even have time to heat up.  

Power, Constant

(Sorry for the A 20W test:  it was so short lived that the math doesn’t even work for the calculations.)

Internal Resistance

Most often (read: always), internal resistance is mentioned as a spot value.  In truth, the IR changes over time.  Due to cell age and cell heat among other things.  A graph of IR is interesting because it can show, for example, when a cell begins to “die” – at which point the remaining energy will be “harder” to extract.  This is when the IR spikes.  In this cell, that’s around 600mAh.  These graphs are also useful for determining if a cell would be good for a hot-rod flashlight, for example.  

Note that average IR:  198mOhm.  That’s high.  A lot of that is due to the button – buttons add resistance naturally.  But some of it seems to just be because the cell isn’t a very high performer.  

Conclusion

I would buy other cells, even if other cells cost a couple extra dollars.  If you have a very low drain application (under 2A), then these cells will be great.  If you need >3A, then stick with the Vapcell 18350 I reviewed the other day.


Notes

  • These cells were provided by LiIonWholesale.com for review. I was not paid to write this review.
  • This content originally appeared at zeroair.org.  Please visit there for the best experience!
  • Whether or not I have a coupon for these cells, I do have a bunch of coupons!!  Have a look at my spreadsheet for those coupons. It’s possible to subscribe and get notifications when the sheet is edited!!

Author: zeroair

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