Say "73" to your li-ion batteries!

[nanZor]

Ok, bad title pun ..

On any handheld that provides some sort of battery voltage display readout, I find it handy to use 7.3 volts as the 20% capacity-left trigger for me to put it back on the charger, rather then wait for the dreaded "low voltage" audible readout, which is basically ZERO percent left.

7.3V, or "73" in amateur radio lingo which means goodbye / see you later - is easy to remember. Say goodbye to the battery and put it on the charger since deep cycling li-ion cuts down on cycle life.

So 7.3V is roughly 20% left.
7.0V is about 10% capacity left.

I try not to exceed these values, but like anyone else I foget and get the low-voltage warning, or come back to batteries so depleted that the protector circuit kicks in, disconnects the cells internall, and you have zero-volts at the terminals. Usually the charger will restart the protection circuit and allow you to charge again. But I don't like to go there on a regular basis.

Still at the end of the day, these are consumable inexpensive li-ion batteries, but I use the "73" mnemonic to put a little care into them.

 

[Firekite]

"73" in amateur radio lingo which means goodbye / see you later

It actually means “best wishes” or “best regards” though it’s certainly most often used at the end of a conversation or contact.

From Ham Radio Glossary

73 -- Ham lingo for "best regards." Used on both phone and CW toward the end of a contact.

The first authentic use of 73 is in the publication The National Telegraph Review and Operators' Guide, first published in April 1857. At that time, 73 meant "My love to you!"

In the National Telegraph Convention, the numeral was changed to a friendly "word" between operators.

In 1859, the Western Union Company set up the standard "92 Code." A list of numerals from one to 92 was compiled to indicate a series of prepared phrases for use by the operators on the wires. Here, in the 92 Code, 73 changes to "accept my compliments," which was in keeping with the florid language of that era.

Over the years from 1859 to 1900, the many manuals of telegraphy show variations of this meaning. Dodge's The Telegraph Instructor shows it merely as "compliments." The Twentieth Century Manual of Railway and Commercial Telegraphy defines it two ways, one listing as "my compliments to you;" but in the glossary of abbreviations it is merely "compliments." Theodore A. Edison's Telegraphy Self-Taught shows a return to "accept my compliments." By 1908, however, a later edition of the Dodge Manual gives us today's definition of "best regards" with a backward look at the older meaning in another part of the work where it also lists it as "compliments."

"Best regards" has remained ever since as the "put-it-down-in-black-and-white" meaning of 73 but it has acquired overtones of much warmer meaning. Today, amateurs use it more in the manner that James Reid had intended that it be used --a "friendly word between operators."

 

[nanZor]

That's very interesting how the definition of 73 over the last century has changed a little bit.

Edison would say my-compliments to the battery for making it down to 20% and put it on the charger.

If you like the easy-mnemonic, you'll love this easy to remember voltage - 8.0v at rest.

Normally, most consider battery replacement when it has only 80% of it's rated capacity left. How to test yours:

1) Charge the battery to full, pull it from the charger, and let it rest overnight / 12 hours or so.

2) Measure the voltage, and if it is below 8.0V at rest, then it is approximately only capable of holding 80% of it's original rated capacity value. Consider buying a replacment.

Of course if the charger itself is not charging the battery to full, you may want to run this test on another charger.

 

[nanZor]

Generic tips

The nice thing about Baofeng li-on batts (and others) is that one needn't go nutso about it - just buy a new one if you accidentally abuse it.

That being said, I still follow the guidelines for avoiding spending much time at the extremes of full charge or total depletion:

1) Don't let the discharged batt (low voltage battery alert, or perhaps sitting below 6.5v) sit around for too long, like days at a time. Get it on a charger, although you don't have to charge to full. Just get it away from the bottom.

2) In like manner, don't keep spares fully charged if you aren't going to use them in say 2 weeks time. If storage is longer than that, I just pull them away from the top.

3) Heat exagerates things. If you are comfortable, so are the batteries.

If you want to store them say from 40-60% as is often recommended, then a *ballpark* voltage at rest would be 7.5 to 7.6v

I like my long term spares in a bit more of operational readiness, so I prefer about 7.8 to 7.9v or so - about 75% capacity.

One can go totally bonkers with RC-modeling like concerns of measuring with a true battery analyzer, but for me the KISS method of just staying away from the bottom of charge and away from the top of charge works at this price-point.

 

[nanZor]

Use a real voltmeter

If one is doing the 80% capacity test, where letting the battery rest for 12 hours after reaching full charge, and seeing what voltage the battery settles to, it is best to use a real voltmeter with some sort of accuracy.

Don't rely solely on the Baoefeng's internal voltage meter. Use a quality voltmeter to see if the battery has settled below 8.0 volts.