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Hello Bill here N3GTY Try this one much better and very lite weight ? ? ? ? ? ? ? ? ? ? ? ? ?

Does anybody know if this will work well for taking QRP to a picnic table , and how long it will last Operating QRP.

Paul,

It'll work but it's designed as a motor starting battery, which means
it works best at high loads for short periods of time, with
near-immediate recharging. So with a low discharge rate (as with QRP
use) and an uncertain time until recharge, its service life will be
disappointingly short. Still, you should easily be able to run all
day at QRP, including occasional amp use.

You need a battery that's designed for relatively low discharge over
an extended period, and then a time-to-recharge measured in hours or
even days, like a marine deep-cycle battery, such as for a trolling
motor.

If you have to carry a battery very far, you may want something
smaller and lighter. The newer LiFePO4 18650 batteries may be useful
for you. Prices now start at USD$2.50 each and they range in capacity
up to 4000mA-hr. But -- beware of marketing "specsmanship," which may
incorrectly represent actual power ratings.

Nevertheless -- three of these will give you an honest 12VDC for quite
a while at true QRP power (amplifiers need not apply), and you can
parallel banks of three for extra current (balancing may be required),
or switch between banks of three as one bank runs out.

If you insist on using an amplifier, you have the luxury of adding
these batteries in series at a nominal 4 V/cell to get the optimal
voltage for your amp if it needs other than 12V nominal.

I've started using these, and right now my biggest down side seems to
be finding battery holders.

73
Jim N6OTQ

On Thu, Dec 1, 2022 at 12:05 PM K2DB Paul Mackanos
<paul.mackanos@...> wrote:

Does anybody know if this will work well for taking QRP to a picnic table , and how long it will last Operating QRP.

Hi Paul,

Yes, that battery would work, though it would not be optimum as it is not a deep-cycle battery.? Walmart does make a U1-AGM battery that is designed for the type of operation that you describe.

The length of time that the battery will power a QRP rig will depend on the rig and operating practice.

I would assume a 5-watt transceiver with 100MA draws on receive.? I would also take the worst case of 25% efficiency of the transmitter and 50% of the time transmitting.? These are very much the worst case.? I would also assume that the average voltage supplied by the battery is (voltage fully charged + voltage to discharge point)/2 or (13.5+12)/2=12.75 volts.? NOTE: most batteries are not recommended to discharge below 12 volts.? Also that the maximum voltage is not 12 volts.

With the above assumptions, the average current draw during transmission would be I=P/(V*.5) or 5/(12.75*.25) = 1.57 amps.? NOTE:? efficiency of the transmitter can have a significant effect on the run time for the battery.? Substitute the current draw when transmitting for your rig.? Most of the QRP-Labs transceivers use less than 1 amp on transmit.

The average current draw per hour would be (1.57+0.1)/2 = 0.83 amps.

The battery is listed as a 35amphour, so approximately 35/.83 = 42 hours.

Above are my best guess.
73
Evan
AC9TU

That is a starting battery, it is designed to supply a high current for a short period then be quickly recharged and is intolerant of deep discharge; a single deep discharge can do significant damage.? You might get away with short periods of use but I would monitor the voltage and stop when you get to maybe 80% charge; past that and the likelihood of damage goes up quickly.??

Deep cycle lead-acid batteries or lithium batteries would be a better choice.? Lithium will also be a LOT lighter (surprisingly so) and easier to tote around.
73, Don N2VGU

For my QDX and QCXs I use a Power Delivery capable phone charging power pack and a PD trigger set to the voltage I need. The same battery pack will deliver either 8.8 volts for my QDX or 11.7 volts for my QCXs. and both will fit in one cargo pocket.?
--
73, Dan - W2DLC

If you’re on a budget like me, any 12 V batteries gonna work great. I mean come on, these things don’t draw very much. HI

Trevor/ N0YMA

Regarding LiFePo4 batteries, typically 4 cells in series is better than 3.? With only 3 cells, it will be just under 11V folly charged and will go down to 9V when mostly dead.

3S is better for LiPo or Li-Ion which are at 12.6v fully charged and drop down to 9V mostly dead.? This is a little low, but 4S Li-Po would be 16.8v fully charged, which is well above published voltage ranges for most rigs.

With 4 cells you are at 14.6V fully charged and 12v nearly dead, which is nearly a perfect voltage range for electronics designed around 12v automotive power.

Apologies for the unclear wording of my last post - Here is a better summary:

3S LiFePo4 is too low at 11-9V
4S LiFePo4 is about perfect at 14.6-12V

3S LiPo/Li-Ion is acceptable at 12.6-9V

Agree completely! LiFePO4 4SxP is a sweet spot for a ham battery chemistry..

Good voltage range match to 12V nominal systems, the chemistry is a lot safer than other Lithium chemistries, a little lighter as well for the same rough size/volume... Capable of high peak and continuous current discharge with appropriate parallel packs. The discharge curve is almost flat across about 90% of it's capacity, no charge memory, and high number of charge cycles... All good things!

The slight downsides are lower power density compared to LiPo and LiIon ( but still very good ), perhaps still a bit of a price premium (but that's dropping... ), and low temp charging ( <0degC ) will damage the cells...

I just replaced my commercial 8Ah LiFePO4 in my POTA pack, which was a great performer ( just too bulky ) with a homebuilt 4Ah 4S1P pack. It's a fun build and good little performer that frees up space in my POTA bag for some antenna options :-)

I am using a battery from Amazon, "12V 6Ah LiFePO4 Battery Pack LF4011, 2000 Cycles Rechargeable 12.8V 76.8Wh Lithium Iron Phosphate Battery with 14.6V Charger" It's about $50 and way too big for a QCX and an amp. If I have known more, I would have gotten one half the size. I strongly recommend the LiFePO4 chemistry. It has great properties.
--
Colin - K6JTH?

Paul,
I have enjoyed this battery for my QCX, Minis, and QDX.
I use it for camping and park use.
12 and 9 volt with USB.
Hope this gives you some help.
TalentCell 12V LiFePO4 Battery Pack LF4100, 2000 Cycles Rechargeable 12.8V 6.5Ah 83.2Wh Lithium Iron Phosphate Battery with DC 12/9 Volt and 5V USB Output for LED Strip, CCTV Camera, Mobile and More https://a.co/d/fES1xhC

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I have had one of these for a year with no issues. A friend recommended it to me and his is 3 years old and strong with no issues as well.

"I strongly recommend the LiFePO4 chemistry. It has great properties"

I agree with that.? Great batteries. Light weight compared to lead acid, no need to charge regularly and very safe. They are supposed to be the safest batteries around and won't catch fire. .? I use them on a mobility scooter and they are very good and better performance than the original lead acid batteries. For standing around not being used for a while it's best to have around 60 to 70% charge in them, not 100%. That's it. Lead acid batteries require a regular charge or float charge or they go bad. Maybe need to check the LifePo4 once a year.

Admittedly they are more expensive than lead acid but they will last far, far longer and unless the lead acid is regularly maintained they will have a pretty short life span.

Reg???????????????????????????? G4NFR