I need some schooling on batteries….

I think the question was already answered here but here's what Delorme had to say…

"Hello Ian,

Thank you for contacting DeLorme Technical Support. This inReach can withstand a 5V charge at 1A with no problem. Please let me know if you have any further questions. Have a great day!

Regards,

Casey A
DeLorme Customer Care
Phone: (800) 511-2459 or Internationally at (207) 847-1165
Many answers can be found at our on-line knowledge base within the link below.
http://support.delorme.com"

Since there is some confusion on the topic of voltage, I am going to make it worse.

Most of the rechargeable Li-ion cells are nominally 3.7V. Their safe range, from fully charged to a safe discharge level is about 4.2V to 3.2V. Some devices may run them lower than 3.2V, but not much.

However, devices that are recharged through USB cables, typically with a micro-B plug, expect 5V. Rechargers powered with Li-ion cells that accept USB cables will provide about 5V. How do they do this? Little bitty solid-state circuits that take whatever the cells are giving and convert it into what the USB specs require.

As mentioned in an earlier post, the cost of this service is a loss of efficiency, perhaps 15%. A similar thing happens in the device being recharged. Its cell(s) (Li-ion) need various voltages at different times while charging, and those are supplied in the device by its own circuitry, starting from the standard USB 5V input. All this voltage regulation is done with solid-state magic — no transformers allowed. Remember those big heavy wall-wart or brick power supplies of old? Transformers! In modern low-power devices transformers are as obsolete as vacuum tubes.

Some people have never even seen a vacuum tube. Well, actually they have: That's what TV tubes are, but now many kids are growing up ignorant of display history. Kids, these days!

When thinking about charging it's better to use watts rather than voltage, as this is really the measurement we are really interested in.

You can think about the watts all day if you wish, but if the input power source voltage is less than the rechargeable battery voltage, you are never going to accomplish anything.

Getting that extra little bit of driving voltage can be very handy. Take a lithium primary AA battery voltage, typically around 1.7 volts. Three of those in series gets you around 5.1 volts, and that is a good voltage to use to recharge a rechargeable lithium ion battery. In contrast, if you tried to use three rechargeable AA batteries in series, it would likely work for only a moment and then stop.

–B.G.–

I think you mean Watt-hour, Mark, which is an amount of energy. A Watt is a rate of energy.

For the small rechargeable Li cells we've been talking about, multiply the nominal voltage (usually 3.7 V) by its mAh rating (e.g., 2450 mAh) to get its mWh capacity (9065 mWh), or divide that by 1000 for the Watt-hour value (9.1 Wh). If a device consumes 90mW on average, then it will use 9.1Wh in 100.7 hours. The cell in this example might last 101 hours powering the device, plus or minus, depending on several variables.

"You can think about the watts all day if you wish, but if the input power source voltage is less than the rechargeable battery voltage, you are never going to accomplish anything."

Bob, do not ignore the role of solid-state voltage regulation in virtually all chargers these days. I discussed this a few comments back.

Jim, I understand the purpose of a voltage up-verter. However, if you are using plain lithium batteries in series, you skip the up-verter and the efficiency loss, and you can just drive the rechargeable battery directly. That's what I have.

–B.G.–

"You can think about the watts all day if you wish, but if the input power source voltage is less than the rechargeable battery voltage, you are never going to accomplish anything."

And yet the setup i've been using daily for the last 2 years DOES work and works very very well

"And yet the setup i've been using daily for the last 2 years DOES work and works very very well"

What you show says nothing at all about voltage or watts or watt-hours or anything else, except that maybe it weighs 213 grams.

–B.G.–

Bob, you asked for it by implying that if the cells don't supply enough voltage to charge something then FAIL. The photo shows a Miller ML105, which bumps up the 3.7 V of the 18650 in it to 5 V output. You know all about this, but you are just being ornery.

Your scheme, Bob, of directly producing the five volts is fine so far as it goes, but the drawback is that when the Li cells' voltage starts to drop, the remaining capacity of the cells is no longer accessible, though admittedly that's not a lot. The Miller charger sucks just about all of the useful charge out of its 18650 — but with some loss of efficiency (probably about 15%).

"Bob, you asked for it by implying that if the cells don't supply enough voltage to charge something then FAIL."

Jim, no I did not. I said nothing and implied nothing about cells at all, did I?

The _source_ has to have enough voltage to drive the rechargeable battery. In this case, what is coming across the cable is likely to be about 5 volts. That is the interface point between the two. The OP did not identify this as being a Miller anything, so it might as well have been a 218-gram rolling pin.

–B.G.–

"What you show says nothing at all about voltage or watts or watt-hours or anything else, except that maybe it weighs 213 grams."

Why do i need to show the outputs, Jim clearly stated these devices have a voltage regulator or step up inverter in old currency.

If you don't believe Jim the voltges are clearly stated in the specs
http://www.fasttech.com/product/1137904-miller-ml-102-universal-usb-smart-charger-version

Current Output 1.2 A
Output Type DC 5.1V

Then you have my experience of 2 years pretty much daily use of the device.

Will that voltage converter lose some efficiency, more than likely
Does the device still work well, yes

When hiking i tend to put my phone into airplane mode and use Endomondo as a GPS logger, after a 8 to 10 hour days i've usually have around 30% to 40% battery left in my phone (Galaxy S4).
My phone uses a 2600mAh battery, so at 40% it will have drained around 1500mAh out of it.

The 18650's i use are 3400mAh and i am seeing 2 day and a bit days use out of 1 3400mAh x 18650 cell.

The pic i posted is of 3 x 3400mAh cells that lasted me 7 days of charging my phone and GPS device.