18650 Protected Or Unprotected For Scubapro Nova Light 720r

[fmerkel]

Some recommend unprotected for backup light, because a protected battery will suddenly just cut out when the voltage drops below a threshold. Personally I use protected cells and just take an extra backup light when night diving.

Effectively not much difference. Most protection circuits cut out around 2.7v (2.5-3.0 depending on the circuit). There is almost no capacity left in a 18650 below 3.0v. If you want maximum longevity you shut it down around 3.2v, before it gets dim or cuts out.

(Note: All use pulls the working voltage down. The higher the amp draw the more it is pulled down. How much it drops depends on the quality of the battery. With a poor battery and a high load it can cut off pretty quickly. When the load is removed the voltage reading will rebound. If you then check it later the voltage may seem to be still quite decent, which can be puzzling if you don't understand this draw-drop-rebound scenario. If you have a completely charged battery that simply isn't doing it's 'job', chances are it either has insufficient power output to support the amp draw, or it's a bad/old battery.)

If you absolutely must have light, with no backup, and it's cut out, you can possibly get a few more minutes by turning it to the lowest setting if it has one......that's assuming the circuit does cut back in. Sometimes you have to put a positive charge across the battery to reset it.

 

[erbedo]

So I went with the Panasonic and the xtar. Amazon should deliver tomorrow

 

[fmerkel]

So I went with the Panasonic and the xtar. Amazon should deliver tomorrow

Should be an excellent combo.

 

[erbedo]

Should be an excellent combo.

Hope so First dive scheduled for April the 3rd, let's see

 

[fmerkel]

You can do a bucket of water dry run before then. Might not be a bad idea. Unlike NiMh which is almost useless to get a reading from you can get a rough idea of capacity remaining from li-on:
volts - capacity remaining in %
4.2 - 100
4.17 - 98
4.13 - 95
4.1 - 92
4.07 - 89
4.03 - 86
4.0 - 82
3.96 - 78
3.93 - 74
3.9 - 69
3.87 - 64
3.83 - 59
3.8 - 53
3.77 - 47
3.73 - 36
3.7 - 22
3.66 - 12

Note - I did not create this, it's off an RC flying forum, and it's more for lithium polymer but the 'principal' is good enough.
It looks deadly accurate, BUT IS NOT, it's very approximate. There are a number of variables that will affect it.