Thanks Jim! That'll get me started! ______________________ Clay Autery, KY5G MONTAC Enterprises (318) 518-1389
On 6/30/2016 3:28 PM, Jim Brown wrote: > 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 > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
