Sanyo 2070C Lithium-Ion Cell Review

Sanyo 2070C Lithium-Ion Cell Review

The Sanyo 2070C is a (maybe) unusual lithium-ion cell size, of 20700. It’s a very solid cell though, as you’d expect from Sanyo! Read on!


Official Specs

Here’s a link to the Sanyo 2070C Lithium-Ion Cell product page on liionwholesale.com.  Here’s the official datasheet, too.  

Price

These are $8.99 each, with volume discounts starting at 3 cells.  

Short Review

Fine cells, with low resistance, and great ability at higher currents (up to 20A tested).

Long Review

Package

I received these in a plastic case, as you would if you ordered two or more.  

Build Quality

Great quality on the wrapper, and everything is just as it should be.  

Size

These cells are just over 20mm in diameter, and just over 70mm long.  

Testing

I’ve tried to keep the scales similar, so over time the charts will be generally comparable.

Discharge tests

Capacity

Energy

Bounce

Bounce on these cells is good.  This indicates the cell is getting most of the energy out and isn’t being driven so hard that the voltage drops to the cutoff.

“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 is 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!

Charge Test

Temperature

Power, Constant

Internal Resistance

The average IR on this chart includes the spike at the end.  So in reality, the rating (13mOhm) is not inaccurate.

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 the graph below, that’s around 750-800mAh.  These graphs are also useful for determining if a cell would be good for a hot-rod flashlight, for example.  

Conclusion

These are fine cells, easily capable to 20A, and likely good to the 30A rating too.  


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!
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