Im so excited

My foray into the world of high power flashlights and Li-ion batteries is almost complete!

I ordered a Fenix TK75 . and a combo pack of the Nitecore i4 and 4 Tenergy 2600 Mah protected batteries. Well I received the TK75 on Wednesday an was just being teased until today when I finally got the batteries and charger.

I have a very old GB multimeter, so I got it out to test the batteries, they tested to just a hair under 4..with this old analog tester that's as close as I can get, (going to HF later to see about a digital tester). I threw the batteries in the light for kicks just to test function.. all seems well.

Threw the batteries in the charger and now I wait. For them to finish and darkness to fall!!

I won't lie... I'm pretty stoked!

You will love the TK75!!!

Welcome to the li-ion battery world.

youll find that you'll end up owning lots of chargers, and I want to recommend my favorite travel charger to you -- Soshine SC-S7

It's small, runs off a USB port, can charge one cell at a time, but for a travel charger I've found that's ok, especially because it has a screen that tells the battery's volts and power percentage and other info. You can use it to check cells to make sure they are all at the same charge level. ALSO, it will charge Ni-MH batteries, AA and AAA.

i keep it in my laptop bag all the time and find it useful both when in town and out of town. It's not any more pricy than an extra battery, and I have nothing but good to say about it.

Thanks guys..

And I'll give that charger a look.. I like the idea of the voltage readout. My Nightcore came with both the wall plug and the 12v plug so I can use it on the move if need be, but mostly to plug it in to my solar setup..

Quick update here.. Had the batteries on the charger all afternoon while I was out in the woods with my Stihl 362 chainsaw making firewood. Came in about every 1/2 hour to check on the batteries, Cause I'm sure they were ready to blow up anytime!:huh: Seemed to take forever to charge, bout 5;30 they had one light constant and 2 flashing so I figured I had some time... I know, I know.. never leave them unattended while charging... out to eat and do a little shopping, need a digital multimeter you know..

So we got home and all the lights on the charger were steady... uh oh.. I checked all the batteries and they were all cool/cold, so the charger did what it was supposed to and quit charging when they were full..Good to know. Broke out my brand spanking new digital meter to check them. They all registered right at 4.22v. In the light they went... YEEHAA this light is cool.. very bright, way so more than the 1-2 million candlepower spot light its replacing.

I do believe I'm going to like this guy!!

4.22v is very high (unless you're measuring immediately after the charger reads complete, make sure you take your measurements after a few minutes off the charger), aim for 4.15v for safety's sake. And li-ions ship charged, usually around 4v out of the box - you can use them immediately since that's between 3.6 and 4.15v.

i have the TK75 too.. and wondering how long we can leave the batts in the light without using?
of course to remove the batteries for prolong disuse but there's no specifics. how long is "too long" that we need to remove the batts? i'm using panasonic protected 3400 mah cells.

i think i will be using tk75 maybe once every 1-2 weeks. should i remove the batts?

A.O. said:

My foray into the world of high power flashlights and Li-ion batteries is almost complete!

I ordered a Fenix TK75 . and a combo pack of the Nitecore i4 and 4 Tenergy 2600 Mah protected batteries. Well I received the TK75 on Wednesday an was just being teased until today when I finally got the batteries and charger.

I have a very old GB multimeter, so I got it out to test the batteries, they tested to just a hair under 4..with this old analog tester that's as close as I can get, (going to HF later to see about a digital tester). I threw the batteries in the light for kicks just to test function.. all seems well.

Threw the batteries in the charger and now I wait. For them to finish and darkness to fall!!

I won't lie... I'm pretty stoked!

Click to expand...

foxxkat said:

i have the TK75 too.. and wondering how long we can leave the batts in the light without using?
of course to remove the batteries for prolong disuse but there's no specifics. how long is "too long" that we need to remove the batts? i'm using panasonic protected 3400 mah cells.

i think i will be using tk75 maybe once every 1-2 weeks. should i remove the batts?

Click to expand...

Good question, I was wondering the same.. My 75 will probably just get intermittent use and seems like a pain to put batts in when needed so I'll probably leave them in. Hope I don't have problems with leakage though.

foxxkat said:

i have the TK75 too.. and wondering how long we can leave the batts in the light without using?
of course to remove the batteries for prolong disuse but there's no specifics. how long is "too long" that we need to remove the batts? i'm using panasonic protected 3400 mah cells.

i think i will be using tk75 maybe once every 1-2 weeks. should i remove the batts?

Click to expand...

The TK75 has a built in Digital Regulator - meaning that you can leave your batteries in for approximately 10 years!!! I'd Recommend to take them out though after 6 months without use.

StarHalo said:

4.22v is very high (unless you're measuring immediately after the charger reads complete, make sure you take your measurements after a few minutes off the charger), aim for 4.15v for safety's sake. And li-ions ship charged, usually around 4v out of the box - you can use them immediately since that's between 3.6 and 4.15v.

Click to expand...

I measured that right out of the charger, but seeing as the batteries were cold I figured they had been done charging for a while, next time I'll wait a bit to check them. So if after waiting they are still at 4.22... what can be done? If the charger charges to that amount what can I do?

3liminate said:

The TK75 has a built in Digital Regulator - meaning that you can leave your batteries in for approximately 10 years!!! I'd Recommend to take them out though after 6 months without use.

Click to expand...

Thanks for the reply...that is good to know but I at least would never go that long without using mine.

A.O. said:

So if after waiting they are still at 4.44...

Click to expand...

I didn't know you could charge a li-ion that high without it exploding, quite a stroke of luck there. Anything over 4.2 is really pushing your luck, your charger is defective if it's supposed to signal a completed charge and you get a reading that high. Definitely time for a new charger.

StarHalo said:

I didn't know you could charge a li-ion that high without it exploding, quite a stroke of luck there. Anything over 4.2 is really pushing your luck, your charger is defective if it's supposed to signal a completed charge and you get a reading that high. Definitely time for a new charger.

Click to expand...

Or... it was a typo on my end.. they tested at 4.22. Sorry bout that.

4.2V is 100% charged, but it isn't at all uncommon for a charger to run it up to 4.1 or 4.2. It also isn't at all unusual for a DMM to be a tenth or two off, unless you bought a Fluke or something of comparable quality.

I've never hurt a light running 4.2V cell/cells in it. You'll never get that unloaded voltage reading past the circuit to the emitter(s). Resistance will diminish it sufficiently.

A.O. said:

Or... it was a typo on my end.. they tested at 4.22. Sorry bout that.

Click to expand...

Oh, whew; yeah, when a charger goes a wee bit over, the trick is to get near the end of the charging cycle and then take the cells off the charger every 15 minutes to check voltage. It's a bit of effort to get exactly 4.15 (and your meter most likely has a margin of error that isn't that accurate anyway) so just get the cells over 4.1 and call it done.

donn_ said:

4.2V is 100% charged, but it isn't at all uncommon for a charger to run it up to 4.1 or 4.2. It also isn't at all unusual for a DMM to be a tenth or two off, unless you bought a Fluke or something of comparable quality.

I've never hurt a light running 4.2V cell/cells in it. You'll never get that unloaded voltage reading past the circuit to the emitter(s). Resistance will diminish it sufficiently.

Click to expand...

If 4.2v is fully charged why wouldn't a charger take it to 4.2v? Shouldn't a charger charge it all the way?

A.O. said:

If 4.2v is fully charged why wouldn't a charger take it to 4.2v? Shouldn't a charger charge it all the way?

Click to expand...

There's a lot of confusion on this.

The correct spec is for chargers to provide 4.2v. But a battery will never return/read the voltage it is provide, they always measure several .01v less than what they are given.

Making matters worse, most chargers provide closer to 4.25v so that cells will show 4.2 when measured/read, because people expect a reading of 4.2 to be 'full' and anything less to be short changed.

Ideally, a charger will provide 4.2 and cells will show about 4.15 off the charger. This provides safer charges and longer cell life. Few do this by design.

ElectronGuru said:

There's a lot of confusion on this.

The correct spec is for chargers to provide 4.2v. But a battery will never return/read the voltage it is provide, they always measure several .01v less than what they are given.

Making matters worse, most chargers provide closer to 4.25v so that cells will show 4.2 when measured/read, because people expect a reading of 4.2 to be 'full' and anything less to be short changed.

Ideally, a charger will provide 4.2 and cells will show about 4.15 off the charger. This provides safer charges and longer cell life. Few do this by design.

Click to expand...

Thanks for confirming that.

3liminate said:

The TK75 has a built in Digital Regulator - meaning that you can leave your batteries in for approximately 10 years!!! I'd Recommend to take them out though after 6 months without use.

Click to expand...

thx, good to know.

ok, something else i still dont get it... let's say recommended to remove batts if no use for 6mths. as opposed to, let's say.. if i use once every 3mths, does that mean it's ok to leave the batts in for 2 years? but not ok for 6mths if no usage? why is that?


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What good is a flashlight with no batteries in it?
You never know when you might need it. Just check the voltage every few months and it will be all good.