[Elecraft] Choosing A Battery For Ham Use

Thu Jun 30 20:02:16 EDT 2016

I'm also replying to the list.  Jim's advice and observations [I left 
them on this] are in total agreement with mine.  My LiFePO4 A123 4S1P 
pack powers my K2 for way longer than I choose to sit on the ground on 
some SOTA peak.  With the K2, over-discharge is self-limiting -- at what 
amounts to full discharge on the pack, the voltage drops very quickly 
and the K2 shuts down.  Store them with about 75-80% charge.

I've had one LiPoly RC pack burst into flames while operating in a 
Spartan Sprint with my KX1.  Fortunately, I was out on the deck, and 
more fortunately, had the pack on a pigtail external to the KX1 and 
could fling it over onto the gravel driveway.  I understand their use 
and good attributes in the RC-world, my only advice is charge them 
outside. :-)

Yes, LiFePO4's do require a cell-balancing charger [some say they don't, 
but then some say the moon landings were faked too], and this 
complicates a situation where you want to power your station from 
batteries on a float charger.

If ounces matter to you, LiPoly is probably the lightest for the 
capacity.  Hard to beat LiFePO4 if you can tolerate a little more weight 
however.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org

On 6/30/2016 4:17 PM, Bill wrote:
> My RC hobby charger manages these batteries according to specs. I have not
> tried but am ready to pull the plug to use them to charge my LIPOs in the
> field to enjoy more operation time. Any thoughts or experience appreciated.
> I do RC via boats, cars and sailplanes.
>
> Bill
> K9YEQ

> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jim
> Brown
> Sent: Thursday, June 30, 2016 3:29 PM
> To: Reflector Elecraft <elecraft at mailman.qth.net>
> Subject: [Elecraft] Choosing A Battery For Ham Use
>
> Hi Clay,
>
> Because this is of general interest, I'm replying to the list.
>
> First, LiFePO4 batteries are pretty much ideal for ham applications because
> of their relatively flat discharge curve, and because their Ah vs weight
> ratio is a good compromise.  For example, an LiFePO4 pack will be above 12.5
> for about 80% of capacity and 12V for 90% of capacity, while a lead-acid
> battery will drop below 12V before it reaches 50% of capacity.
>
> Second, LiFePO4 batteries provide a LOT more charge-discharge cycles if
> treated properly. The result is that if you're going to use them for a lot
> of years, the longer life more than compensates for their higher cost.
>
> Third, LiFePO4 batteries are MUCH safer than Li-ion batteries.
>
> Disadvantages of LiFePO4 are initial cost and the fact that they need a
> special charger. However -- Bioenne told me that they can be safely charged
> using the West Mountain SuperPWR Gate set for AGM batteries and a power
> supply that is adjusted to about 14.5 volts. The AGM setting of the PwrGate
> limits the charging voltage to 14.2V, which is what LiFePO4 batteries need.
> Also, LiFePO4 batteries do NOT like to be discharged below about 95%, so
> care must be taken not to fully discharge them. Good battery packs will have
> control circuity that prevents this.
>
> Now, as to how much battery to buy.  Start by studying current draw of the
> radio(s) and other equipment that you'll use with the battery, taking TX/RX
> duty cycle into account. Also look at weight if you're going to carry it.  I
> bought a 20Ah pack (5.5#) to loan to a friend who was going to pack several
> miles uphill to activate a rare 6M grid with a
> KX3 and the 100W amp, and I just bought a 100Ah pack (26#) to run my SO2R
> shack. If I were going to pack with a KX2 or KX3, I'd buy something much
> smaller, like 6 - 12 Ah (2 - 4#), or even smaller.  Your application
> carrying a K3/P3 around to chase RFI pulls about 1.6A, (1.8A with the SVGA
> module in the P3).  A KX3 plus PX3 pulls about 350 mA at max screen
> brightness.
>
> Bioenne (and other vendors) package their LiFePO4 batteries more than one
> way for the same Ah capacity, often to retrofit into existing gear.
> With Bioenne batteries, I chose the PVC pack, which is lighter weight than
> the rectangular "solid" format.
>
> Bioenne and other battery vendors do NOT say that their chargers are
> RF-quiet, which is why you would use a PowerGate and known clean supply.
> To charge from solar, buy a Genasun charge regulator, which IS pretty
> RF-quiet.  I've told Bioenne that they need to find quiet chargers.
> We'll see how they respond.
>
> As to voltages -- I would ONLY buy 12V nominal to power ham gear. If you
> need other voltages for other gear, look at http://www.batteryspace.com
> which carries a MUCH broader range of batteries. They're also good people,
> located in the SF Bay area. Bioenne is in Santa Ana, CA.
>
> I've chosen to avoid voltage boost products, which are essentially SMPS, and
> noisy. Yes, you can set them to be active only on TX, but if you're running
> two radios, the one you aren't TXing on will hear the noise.
>
> As to charging -- LiFePO4 batteries will last a lot longer if they are not
> fast-charged.  A good rule of thumb is their 4 hour or 10 hour discharge
> current. In other words, for a 20Ah battery, avoid more than about 5A charge
> current.
>
> If you're sizing the battery to power your shack and will be float charging
> it, the charge current can be added to the capacity to figure how much
> battery you need. In my application, with worst case of SO2R contesting at
> 100W, I'll be TX on one radio or the other almost all the time, so I'm
> looking at roughly 12A worst case. If I wasn't doing SO2R, I could get by
> with a smaller battery.
>
> For non-critical applications like video monitors, router, cable modem, etc,
> I'm using el-cheapo lead acid batteries from my hamfest stash, and floating
> them from suitably sized linear wall warts. I've found that for most gear,
> voltage is not all that critical. For example, my Samsung computer monitors
> are sold with a 14VDC wall wart, but were still running fine when my
> lead-acid battery had dropped to 10.5 volts.
>
> I've looked around a lot, and so far have not found a better practical
> battery chemistry than LiFePO4.
>
> Another important point. For running electronics of all types, we do NOT
> want automotive batteries, which are primarily designed to provide a big
> hunk of current to start the engine, but which don't like to be deeply
> discharged. Instead, we want deep discharge types. Pay attention to this
> when selecting a battery.
>
> 73, Jim K9YC
>
> On Thu,6/30/2016 12:07 PM, Clay Autery wrote:
>> Jim,
>>
>> Looking to get LFP batts for my shack/house/mobile.
>>
>> Could you recommend sizing guidance?  Is it as simple as multiplying
>> the voltage x amps to get watts and then dividing by 12VDC to get a
>> 12VDC current draw, and then spec'ing a batt based on Ah, etc etc...
>> calculate run time to 80% discharge (they claim up to 90%).
>> Or do I need to spec for some % overhead.  I usually size stuff for
>> 50% overhead, so that if the device is running flat out it won't push
>> the supply beyond 50% max continuous.  Does that apply here?
>>
>> Suggestions on how to get the required voltages I need:
>>
>> 5VDC - Probably won't need for now...  Can get most of the supply I
>> need from the laptop docking station via multiple powered USB sockets.
>> 12 VDC - easy (and run the 18.8 VDC K3s and P3 from 12V if I have to?)
>> 13.8 VDC - For radio if possible to do it quietly.  (12 VDC w/ boost
>> circuit or 24 VDC with buck circuit...  Boost seems more efficient,
>> but see below)
>> 19.5 VDC - Laptop (and USB 5VDC)  Boost or buck...
>>
>> Any ideas would be greatly appreciated...
>>
>> At a minimum, I want to get at least one battery to run my K3s/P3 to
>> hunt RFI with the house service off and then on one branch at a time.
>> At some point want to put batteries on all HAM, Broadband, Router, and
>> switches...
>>
>>
>> Thanks...
>>
>> ______________________
>> Clay Autery, KY5G
>> MONTAC Enterprises
>
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