Illumn.com Protected MJ1 Lithium-ion Cell Review

Illumn.com is offering this Protected MJ1 18650 Cell. Quite a performer with regards to capacity, at 3500mAh! Discharge is around 10A, too.

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Official Specs

Here’s a link to the Illumn.com Protected MJ1 Lithium-ion Cell product page.

Nominal Capacity: 3500 mAh
Minimum Capacity: 3400mAh
Nominal Voltage: 3.6V
Discharge End Voltage: 2.5V
Standard Charging Current: 1.7A
Max. Continuous Discharging Current: 8A (due to protection cut-off)
Protection IC: Seiko S8261G2J
Mosfet: AO AO8814 x 2

Short Review

Great cells which perform well, but the protection circuit prevents actual 8A discharge.

Long Review

Package

These cell ship (if you buy sets of 2) in a plastic case inside a cardboard box, with foam to hold the cells securely.

The plastic case that holds two of these cells is a little different than most of the common (cheaper) cases.  This one’s quite nice.  The two tabs that hold it closed are a little hard to snap open.

Build Quality

These cells are nicely put together, with added protection and extra sleeve.  A nice touch is that the outside (added) shrink wrap is clear, so the original MJ1 green is visible.

An interesting artifact of this is that the metal strip that runs from the top to bottom of the cell (which has to do with the protection circuit) is visible.

Law requires (at least to the best of my knowledge) that cells like these be labeled with the capacity and the like.  This sticker is clear too except the text, which again, is a nice touch.

The clear wrapper (again, did I say the clear wrapper is cool?) allows the protection circuit, which is on the negative end of the cell, to be seen clearly.

At right below, see the metal strip running from negative to positive.

Size

Officially:  68.8mm (L) x 18.7mm (D).

Longer than an unprotected 18650 cell by the length of one button and one protection circuit.

Testing

I tested these the same way as I tested the cells in the previous review.  (Another MJ1, but with a different protection circuit).

Discharge tests

I didn’t test these cells higher than 10A because the protection circuit is a 8A circuit.  These cells will discharge at 7A for a few minutes (10-15 minutes) but the protection circuit will eventually trip.  At 10A discharge, the circuit trips immediately.

Capacity

Again, disregard the 7A test.

Energy

Charge test

Power, Constant 10W

Internal Resistance

Graph of internal resistance (IR).  This is shown over the course of a discharge, and comparisons are made between the nearest discharge currents (ie 0.2A vs 0.5A) and also vs disparate discharge currents (0.2A vs 5.0A).

Interestingly I threw these cells in the SkyRC MC3000, and the IR was reported at around 105-120mR. Which is to say that it’s nice to see these very different means of testing IR to match up very precisely.

Spec Sheets

Here’s the spec sheet for the base model of this cell, the LG MJ1.

Conclusion

I like these cells for medium discharge (where medium is 5A or so, and below).  It’s very nice to be able to get these MJ1’s with protection, for a great price ($6.50).

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Notes

• These cells were provided by Illumn.com for review. I was not paid to write this review.
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