The KA7OEI FT-817 pages
Operating the FT-817 from Lithium-Ion (Li-Ion) batteries

Front panel view of my FT-817
A Front-panel view of my FT-817. 
Using Lithium-Ion (Li-Ion) (and other) Batteries with the FT-817:

Important note:  Lithium-Ion (Li-Ion,) NiCd, and NiMH cells and battery packs are potentially dangerous!  Very specific precautions must be taken to assure cell longevity as well as safety of personnel and equipment! Do not use a Li-Ion cell or battery pack in any way other than specifically stated by the manufacturer without first fully understanding the factors involved in their usage:  There is a good reason why you can't just go out and buy individual Lithium-Ion cells at your local electronics store.  What follows are general guidelines and it is up to the user to do his/her own research to determine how best to (safely) use the technology.  (This warning can also be applied to Lead-Acid, Alkaline,  and other cell types as well.) You have been warned!

For information about operating the FT-817 with other types of cells, go here.

One of the more recent innovations in battery technology is the development of the Lithium-Ion cell.  Unlike the previous (well-known) lithium cells (such as the coin cells used in watches, computer battery backup, etc.)  it contains no actual metallic lithium - an element that is highly reactive -  but rather a Lithium-Cobalt Oxide is typically used - a material that poses less of a hazard.  The major advantage of Lithium-Ion cells is that they have a good power-to-weight ratio (i.e. "more watts per pound") as compared to almost any other common rechargeable battery technology.  Note that even though Lithium-Ion cells are light, they aren't necessarily smaller that other types. These desirable properties come at a price:  Lithium-Ion cells are a real pain to work with.  They do not take kindly to abuse - and any abuse that you insist on meting out will likely result in permanent damage - to the cell - and possibly the user!  (But more on this later...)

First off, how many cells are required to run the FT-817?  The nominal voltage for each cell is 3.6 volts or so, so it would seem that either 3 cells (10.8 volts) or 4 cells (14.4 volts) would be ideal.  The reality is quite different, however.  

More conventional rechargeable batteries (such as NiCd and NiMH) have the rather unique property (in the battery world) that they maintain a fairly constant voltage over their discharge cycle - around 1.2 volts - although they start out in the vicinity of 1.5 volts when "fresh out of the charger" and very quickly settle down to the lower voltage.  They maintain their voltage fairly well (within a few tenths of a volt, depending on load and battery condition) until their charge is nearly depleted - and then the voltage suddenly nosedives.
Differences in Li-Ion cells

When this page was first assembled in 2001 the majority of the Li-Ion cells available (especially on the surplus/used market) used a coke anode.   Since that time, the newer Graphite anode cells have become dominant.  The three most important properties of the newer cells are: 

- Higher capacity.  A 18650-type cells originally had a capacity in the 1.3-1.5 aH range while the newest 18650 types hover around the 3 aH range.  There are some sellers that advertize 4 aH capacity cells, but load/capacity testing by those in various "Flashlight" forums indicate that these ratings are usually "optimistic".
- Higher "discharge" voltages.  The older (coke anode) cells were discharged when their voltage got down to 2.5 volts or so, while the newest cells are considered discharged at about 3.0 volts. 
- Flatter discharge curves.  Newer graphic anode cells stay at higher voltages for a longer time, thus allowing some devices - such as the FT-817 in a 3-cell arrangement - to utilize more of the cells' charge. 

What does this mean with respect to the '817, then?  Take our "3 cell Li-Ion pack" example: 

- With the older coke anode cells, the voltage would drop below 8 volts (the lowest voltage at which the radio is guaranteed to operate "normally") with a significant amount of energy still left in the cells. 

- With graphite anode cells, the cells are "dead" at 3 volts, meaning that the radio still "sees" 9 volts - a voltage at which the radio is perfectly happy. 

A Word of warning:  If you chose to assemble a 3-cell Li-Ion pack for your '817 (heeding all other warnings, of course) you must determine if your cells are coke or graphite types anddesign your pack to disconnect the cells appropriately - something done with a "protection circuit", a device easily found at many of the same places that sell the LiIon cells in the first place!

This property makes them fairly easy to use.  It would be safe to use, say, 10 NiCd or NiMH cells to operate the FT-817:  When freshly charged, this battery would put out 16 volts (the maximum upper voltage for the FT-817) or less, and quickly settle down to 11-12 volts - a fairly "nice" voltage.

Li-Ion cells are different animals, however.  Let's relate them to more familiar technology - the Alkaline cell - first.  We think of Alkaline cells as having 1.5 volts per cell, but the reality is that this "nominal" voltage only occurs when the cell is brand new and unloaded - and this voltage drops gradually as the cell is depleted.  In this manner, Li-Ion batteries behave more like Alkaline cells than NiCd or NiMH - which tend to hold a constant 1.2 volts per cell.

When a Li-Ion cell is fully charged, its voltage is typically 4.20 volts (for some battery chemistries it may slightly higher or lower - but we'll talk about the 4.2 volt variety here...) and during the discharge cycle this voltage drops down until it gets to 3.0 (or 2.5) volts per cell  (see sidebar for an explanation of the differences.)  Like all cell technologies (be they Alkaline, NiCd or NiMH) the internal resistance also increases somewhat as the battery is discharged (and as it ages.)

Let's take this and apply it to our "3 Cell" Li-Ion battery pack.  When fully charged, it will put out 12.6 volts - a nice voltage to operate the radio.  Using coke-anode cells, when it is nearly discharged, this voltage drops to about 7.5 volts - and that is right at the bottom end of where the FT-817 will function and doesn't even take into account the internal resistance of the cells or wiring losses - both of which are factors that reduce the voltage when current is pulled from the cells.  This means that we will have "wasted" some of our cell capacity due to our inability to operate when the voltage is low.  (Note:  Using more modern Graphite-anode cells, this isn't necessarily true - see the sidebar.)

What about our "4 Cell" Li-Ion battery pack?  At a cutoff voltage of 2.5 volts per cell, this would mean that the '817 gets 10 volts - plenty of margin there.  What about the "full charge" voltage?  With 4 cells at 4.2 volts, this would apply 16.8 volts to the radio - nearly a volt beyond the radio's rating - something that is a definite no-no.

The upshot of all of this?  You may not be able to use a Li-Ion battery to directly power the FT-817 and get both full battery life and stay within the radio's voltage ratings.  With 3 cells (using coke anodes) the radio will shut down before the battery is fully discharged, and with 4 cells, the full-charge voltage exceed the rating of the radio.

There are several options to get around this:

The most energy-efficient option is the last one and the reasons for this are described on the linked page.

Keeping Li-Ion Batteries happy:

Li-Ion batteries are very finicky animals.  They are really quite fragile and need to be treated "nicely" in order to assure long life as well as safety.  Here are a few of their finicky properties - some of which may vary slightly with differing Li-Ion cell types and chemistries:
Lithium-Ion cells are fragile!

Li-Ion cells are actually a pain to work with:  They don't like to be over-charged (they can explode!) or discharged too far (they tend to be damaged.) 

For this reason Li-Ion cells are literally surrounded with circuits to protect them from overcharging, "over discharge", and overcurrent.  This circuitry may be built into the pack itself, or it may be in the appliance that uses the cell/battery. 

Here some of the minimum requirements for the circuitry in a "safe" Li-Ion pack: 

  • Every cell is individually monitored to detect an overvoltage or undervoltage condition.  If either condition is detected, the charging current or load is disconnected as appropriate.
  • Short circuit protection must be employed.  This can be as simple as a fuse, or as complicated as a current monitor.
Failure to very carefully monitor the voltage/current conditions can result in a Li-Ion cell/battery that has poor lifetime.  Worse yet, the cells can fail catastrophically if badly abused - possibly resulting in equipment damage or even personal injury! 

In short, you cannot simply just buy some Li-Ion cells and use them to replace Alkaline, NiCd, or NiMH cells and expect them to work safely, efficiently or have a reasonable operational life!  Additional protection circuitry is required to assure overall safety!

Actually using Li-Ion cells with the FT-817:

Having said all of this, you might ask yourself "Who would want to use Li-Ion cells at all?"

Well, I do!  Why?  They are light - having an excellent power/weight ratio.

How do you use these cells, then?  There are number of chipsets that can be used to monitor/protect a Li-Ion battery pack (see sidebar.)  Also, knowing how to properly treat a Li-Ion pack can go a long way toward aiding one in designing their own protection/interface circuitry using off-the-shelf components.  If you are able to build such a circuit, you probably don't need my help in designing the circuit.

There is also another way - Use an existing Li-Ion battery pack:  That is what I did.

Note:  Disassembling any battery pack can be hazardous and I cannot recommend that you do so.  If you insist on doing so despite my warning, you assume all risks in doing so.  You must take care to avoid shorting, puncturing, or otherwise damaging any cell(s) or associated circuitry in the pack, nor should any safety device be defeated.

Several years ago (at the 1999 Dayton Hamvention, to be precise) I picked up three Li-Ion battery packs (HP model F1193A) that were intended to power a laptop computer.  These are rated at 14.4 volts with a capacity of 2.5 amp/hours.  More recently, I was given a defective (but fairly new) battery pack (the circuit board was blown up, but the cells were just fine) that happened to use the same type of cells (Sony US18650.)  Each pack is arranged in a 2 x 4 array (4 pairs of cells in series.)
A few chips you might be able to use  with Li-Ion cells

If you insist on building your own Li-Ion pack from scratch, you should familiarize yourself with all of the possible hazards associated with doing so. 

You'll also need to properly protect the cells from over and under charge as well as overload conditions.  If you are clever with circuit design, you can come up with your own circuits to do this job.  There are, however, a few ICs out there that are designed to help you do this: 

Maxim Semiconductor has a few ICs that are designed for cell and battery management of NiCd, NiMH and Li-Ion.  A handy table showing the family of such chips may be found here.  A few of the chips of most interest in the context of this article are the MAX1665 and MAX1666.  It is worth noting that Maxim has provisions that permit individuals to buy small quantities of their ICs - go here.

Also, there is the UCC3911 series made by Texas Instruments ( that can disconnect the cell(s) to protect them.  There are several chips made, so be sure that the correct one is chosen for the cell-types that you intend to use.  There are also "gas gauge" chips available from TI - the "BQ2000" series (such as the BQ2050) can help you monitor how much charge is going in to and out of the cell. 

Note:  The above is not intended to be a recommendation or endorsement of a particular manufacturer or IC, but rather to help steer someone toward the right place.  If you find some useful, information please let me know.

These cells have a nominal rating of 1.5 amp hours each (depending on specific vintage, model, and application) and they are of the "Hard Carbon" anode type.  The three packs from Dayton contained a small circuit board which contains the necessary monitoring circuitry to prevent "over-discharge" (i.e. a MOSFET switch disconnects the pack when any of its cells' voltage gets too low) as well as overcharge protection (a MOSFET disconnects the charge current, too...) as well as overcurrent protection (a resettable circuit using a MOSFET to interrupt current flow in case of overload.  In addition to all of this, the board also contains a BQ2050 battery monitor chip - a circuit that is capable of keeping track of the amount of current put into and pulled out of the battery, allowing the current state of charge to be ascertained (I haven't gotten around to interfacing with this chip yet...)

In looking at the circuit board, I did enough reverse-engineering  to determine that it was perfectly capable of handling two of these packs in parallel and the 2 amp draw of the FT-817 was also within the capacity of this circuit. This allowed me to assemble two battery packs, each using a 4 x 4 array of cells - resulting in a battery pack with over 5 amp/hours of capacity.

I repackaged the cells and the circuit board in a homebrew enclosure constructed of acrylic plastic.  In addition to the built-in overcurrent protection (on the circuit boards) each pack has an inline fuse.  Also added is a small pushbutton switch used to reset the overcurrent protection.  Normally, this sort of reset is accomplished by applying charge to the battery.  If you are out in the middle of nowhere, you can't always obtain a charging source.  How, you might ask, does the overcurrent get triggered?  Well, the switching regulator has several thousand uF of input capacitance - and when it is connected this capacitance can appear as a brief short circuit.  When this happens, the overcurrent protection circuit does its job.

When using one of these Li-Ion packs with the FT-817, I use it with the Synchronous Buck-type switching regulator, described on the Optimizing Power Consumption of the FT-817 when using battery power page.  Why?  When fully charged, this pack puts out at least 16.8 volts (over the voltage rating of the FT-817.)  Also, the switching regulator allow more efficient use of the battery's power capacity as described in the aforementioned page.

How do I charge these cells?  Actually, the built-in circuitry makes it quite easy:  I have a power supply set to precisely 16.80 volts and the circuitry prevents overcharge.  Ultimately, I plan to build a "smart" charger (so I don't monopolize my workbench power supply when charging these things) but in the meantime, this method works.
View of the two 14.4 volt 6 aH Lithium-Ion batter packs.
Exterior view of the two 6 amp/hour 14.4 volt Li-Ion packs.  As-packaged, these packs weigh 32 oz (approx. 900 grams) each
Click on the picture for a larger version.

You might also wondering if the cells above are rated at 1.5 amp hours, and there were two in parallel in the original packs, then why was the original pack capacity 2.5 amp/hours instead of 3 amp/hours?  My guess is that it has to do with the property of any battery pack:  The higher the load, the lower the capacity.  In the case of, say, a 100 amp/hour battery, you can probably draw 1 amp for 100 hours, but you can't pull 100 amps for 1 hour.  Why?  The chemistry is less efficient at this higher current end of the world.  The same goes for the Li-Ion packs:  The laptop for which they were originally intended probably pulled several amps - and the amp/hour ratings of the cells is based on a much smaller load - approximately 0.2C.  Since the FT-817 generally pulls about 300 mA on receive, I would guess that the actual capacity of the packs will be closer to 6 amp/hours.

How long will one of these packs power the FT-817?  If the '817 is just sitting there on receive in a squelched state, using the switching supply, one could reasonably expect about 26 hours of operation. Without the switching regulator, this would drop to 20 hours or so.

Notice:  The information contained on this and related pages is believed to be accurate, but no guarantees are expressed or implied.  The information on this and related pages should be considered to be "as-is" and the user is completely responsible for the way this information is used.  If you have questions, additional information, or you find information that you believe to be incorrect, please report it via email.

Follow-up - and some practical advice on using/storing batteries and packs:

As you might expect, the cells in the battery packs depicted above eventually "died" of old age as LiIon packs do:  At best, one can typically expect to get just 5-7 years after the date of manufacture out of a set of normal LiIon (or Li-Poly) cells under normal conditions:  That's just the way that they are!
Since the original writing of this web page back in 2002 or so I have learned more about how to "care" about LiIon cells of various types.  While there is nothing wrong with the original advice, above, there are a few things that one can do to prolong the life of  LiIon packs:
As you read the above, something may have occurred to you along the lines of "The entire reason that I have these batteries is for emergency/backup/portable use, so how do I justify keeping them around if they aren't fully-charged?"

That is a very good question, and if you find that this applies to you, the most pertinent advice is probably the first point, above, about not "fully" charging them.  If your needs are such that you must keep your LiIon battery packs charged at all times, your best options are:
Remember:  With casual use it can be difficult to tell how badly a cell has degraded.  Having used a variety of LiIon (and other types of) cells for several decades now and having the equipment on-hand to analyze the actual capacity of those cells I have observed that it is not immediately obvious that a NiCd, NiMH or LiIon battery pack for a radio such as a Handie Talkie - or even a lead-acid battery - has degraded until it gets down to 15-25% of its original amp-hour capacity.  Even at such diminished capacity it will "seem" to work OK - even at high transmit power - but it is not until it is used "heavily" for several hours or days that it suddenly becomes obvious that it is a shadow of its former self - and then it's too late!

For additional information about charging Lithium-Ion cells, visit these pages:

For information about operating the FT-817 with other types of cells, go here.

Another "battery" page:

The NiCd/NiMH page  -  This page describes in some detail the care and feeding of NiCd and NiMH cells and batteries.  This explains how to keep NiCd cells going, and what that "memory" affect really is!  (Hint:  It's not the "memory" effect at all!)  This page also has Links to manufacturers' information about various types of cells (NiCd, NiMH, Li-Ion, Alkaline, etc.)

Go to The KA7OEI FT-817 "Front Page" - This is, well, the "front" page of the '817 pages here...

Any comments or questions?  Send an email!

This page maintained by Clint Turner, KA7OEI and was last updated on 20150415.  (Copyright 2001-2015 by Clint Turner)

Since 12/2010: