EMRFD Message Archive 14257

Message Date From Subject
14257 2017-09-05 10:54:53 byjimeny Would one of these car starters work as a QRP supply?
Not exactly EMRFD but still....

It seems it would, however, I really do not expect it to be an 18 AH capacity.
It would have a 12v output which would be good for SOTA work. Eh?




14258 2017-09-05 11:47:37 AD7ZU Re: Would one of these car starters work as a QRP supply?
that thing will go beyond a QRP supply ... probably run a 100W xcvr for a few hours 
not a bad price considering it comes with the charger, metering and cables


14259 2017-09-05 12:37:16 Bill Carver Re: Would one of these car starters work as a QRP supply?
AH capacities always going up so the 18AH is quite possible. Bare battery vendor claims often aren't true, but in this case, in a finished product, I expect they monitor their battery supplier and know they're getting 18 AH batteries.

I used a 10AH four-cell Lithium helicopter battery to run my 100W K3 from the base of a FD antenna for a while. In my experience with a model helicopter battery, four cells delivered more than 15V at 20A, KEY DOWN, to a 100 watt K3. Scarey but the K3 did survive.  It does not say what the open circuit voltage is. It's either 3 or 4 Lithium cells. Three doesn't delivers about 11V, probably insufficient for a commercial QRP rig expecting a nominal 13.6V supply.

"Recharges in 5.5 hours". That's 15V x 5.5 AH = 82.5 watt hours. If the battery is four cells, about 15V, that's 5.5 AH. How do you recharge even a half discharged 18AH battery with 5.5AH? Answer, you don't. That "recharges in...." is BOGUS.  They left off "...from one successful car start" or some other mealy-mouth qualifier. If it's an 18AH 3-cell battery and a 100% efficient switching charger delivering 15W, that's 12.6 hours for a four cell battery. Since the battery itself is not 100% efficient its is going to take longer than that by 10-20 percent. I'd guess 8 hours to recharge from 50%. It'll charge faster if it's only three cells, but still way longer than "5.5 hours".


14260 2017-09-05 14:35:58 Lasse Moell Re: Would one of these car starters work as a QRP supply?
It may be even worse!
Often with ultra cheap powerbanks, the stated mAh is really w.r.t. the cell voltage i.e. using LiIon with 3.8 V... So for those rated at 10 Ah this will translate to 38 Wh, and with 5 V output this is only 7.6 Wh.

If they have pulled the same thing here... we have 18 Ah at 3.8 volt and this translates to 68.4 Ah, and charging with 5 V and 2.1A for 5,5 h equals 58 Ah...

I bet the pack can only deliver 12 V 5A for one hour tops... And we hade this disussi
14261 2017-09-05 14:49:28 Frank Dinger Re: Would one of these car starters work as a QRP supply?
Bought a similar car start battery pack here in the UK ,but the starter cable had a MOSFET circuit in a separate enclosure which only passed current when the impedance of the device to which current  was to be supplied was LOW, (hence the car battery)so as bought I could not supply a radio even with a fully charged battery pack .

So, I removed the MOSFET circuit ,replacing it with a fuse and now the pack can supply a radio or other electronic devices ........but probably can no longer be used to start an engine.

My battery pack has a built-in torch which even can automatically send Morse ...---...
I remember I paid GBP 29.95 for the pack which is small (size 155 x 100 x 35 mm)  and labelled 8000A1 providing 8000mAh at 3.2-3.4 V  ;  4600mAh at 5V (via 2 USB sockets  and 2000mAh  at 12V.
Charging the pack is with 5V-1A(max) through a microUSB port

I extended the "fat" starter cable with a thinner cable adding an Anderson Powerpole connector, using the pack with a FT817 radio for mobile/field operation .

If you consider buying the unit as per your message please check suitability for feeding a radio ,etc

Frank  ,  GM0CSZ / KN6WH    in IO87AT

14262 2017-09-05 17:20:33 mosaicmerc Re: Would one of these car starters work as a QRP supply?
Interesting ..
I was looking at  making an RFI controlled & shielded boost regulator to make a  5V to 13V for QRP use to make all these cheap 20AH ($12 - $13)  power banks compatible.

If anyone is interested , let me know...I might make a few extra for the group.
14263 2017-09-05 21:00:04 Gabriel Nemeth Re: Would one of these car starters work as a QRP supply?
Not sure I trust these devices without taking them apart. I suspect it is great for delivery of a high current for a very short time. So, long term constant current drain may not be the best use for this device, that is just a guess.

IMO. I would prefer to purchase a quality Motorcycle Sealed Gel cell battery. You can get them here for 50$.

14264 2017-09-05 21:24:19 Bill Carver Re: Would one of these car starters work as a QRP supply?
The 4-cell 10 AH Lithium "helicopter battery" was rated at 100A maximum. It was about $30 two years ago. I also got a "Turnigy" Accucell 6 charger. It runs off 12VDC and charges all kinds of batteries, including the model airplane batteries with have a connector bring each cell out so the charger can balance all the cells. The Turnigy has been copied by Chinese vendors, I've heard bad stories about them. The Real Turnigy was about $25, in my opinion too much rides on the charger to get a knock off.

The K3, at 100W, was pulling less than 20A. But that's still a substantial current. I had a 4-2/1 digit FLuke in my bag and I measured the battery terminal voltage key up, key down: I don't remember now how much it dropped, but the voltage change was in milllivolts, not ever a tenth of a volt and I was startled.  Have to be careful: airplane batteries do NOT have much mechanical protection. Puncture is easy, compared to that packaged gadget. After crimping a PowerPole on mine, I cut a hole for the lead wire to exit its carboard box, and I used glass tape to hold the box together to provide slight protection. I wasn't pulling enough energy, or charging it quickly, so the battery didn't ever get hot, despite the carboard around it.

The Lithium batteries are really great batteries. And heck of a lot lighter than a motorcycle battery.  The only issue is the terminal voltage is low on 3 cells, high on 4 cells, compared to 6 x 1.2V from lead-acid batteries.


14265 2017-09-06 04:45:56 Alan Melia Re: Would one of these car starters work as a QRP supply?
Aha be careful what you expect SLABs at 18AH will NOT supply 18A for an hour
! Look carefully at the specs and you will see the 18AH is at the "20 hour
rate" so it will supply 900mA for 20 hours. As soon as the current draw
increases, then the capacity reduces. See the Battery University for more
detail. .......But yes they are useful.

14266 2017-09-06 08:07:48 byjimeny Re: Would one of these car starters work as a QRP supply?
I should have mentioned that I am a big (oxymoron) QRPer and my main radio is a KX3 which draws only about 1.2 amps on transmit and even smaller amount on receive.  Not looking to power a 100w rig.  Thanks for all the suggestions and ideas.  I'll see if I can borrow one from another ham and try it out. 
14267 2017-09-06 08:53:55 Thomas Noel Re: Would one of these car starters work as a QRP supply?
I purchased a Kimoon 12000 man combo 5V USB charger and 12V car jumper from TomTop for $29 on sale. I estimate it is really about 8-9 Ah capacity.  !2V auto jumping connection is 10ga with large alligator clamps. I cut the 10ga and inserted 45A Anderson Powerpoles so I have a choice of APP or the clamps. Measured output is a well regulated 13.8V. If drawn to 12V it takes 8-9 hours to recharge. Device has flashlight and emergency flasher. 

I have not jumped a car, but I have jumped a 750cc motorcycle with no problem, and I have operated a BitX40 v3 sad for 6 hours on field Day.

Thomas W Noel

14268 2017-09-06 09:07:02 Bill Carver Re: Would one of these car starters work as a QRP supply?
April 2015 QST has an article by Phil Salas, AD5X. He has a KX3 and says a 3-cell lithium battery is too low to run it, and a fully charged 4-cell exceeds its maximum voltage rating. A key issue before you connect the KX3, is measure the voltage of the battery. Be good idea to not connect it if you measure >15 VDC 'cause it's a 4-cell. If it measures around 11 volts, then its a 3 cell and will crank a car (for a while) but not run the KX3.

His solution is to put two diodes in series with a 4 cell Lithium battery when its fully changed, shorting them out when the battery discharges and the voltage drops.

I will point out that he uses two 1N5401. The parts list says "Shottkey diode", which is incorrect. It's just a normal 3A silicon rectifier.  Any 1N540x (x=1 to ) will work just as well and a 1N5404 (400PIV) might be easier to find locally, or already in your junkbox.


14269 2017-09-06 12:54:45 Clark Martin Re: Would one of these car starters work as a QRP supply?
I bought one such battery pack.  12V with 12V output, USB output and car starting connection.  Rated at 12 A-h.  It has 4 Li cells marked as 2.9 A-h.  Series wired and they multiplied the A-h rating.  Simply put a lie.  It’s still useful and the pack does have a balanced charger plus under voltage protection. 

One additional problem with some of these is you have to press a button to turn on power and if you aren’t drawing enough it turns the power off.  Could be a problem with some QRP rigs.

Clark Martin

14270 2017-09-06 13:20:54 Bill Carver Re: Would one of these car starters work as a QRP supply?
So they were saying 4 cells in series make it a  4 x 2.9 AH battery?
Hafta wonder if they're dunces, or dumb like a fox (IE, if consumer doesn't know any better OK, if they think I'm dumb, OK)
I use 3 Li cells to run my N2PK network analyzer at the antenna and it's oh so much lighter than the lead acid battery with same AH rating that I used before.

14271 2017-09-06 15:38:57 bellettau Re: Would one of these car starters work as a QRP supply?
One thing to watch with some of these 'car starter' packs that have a switch to cycle through modes. (torch, CW etc). The 5V output voltage, when switched on, spikes for a short duration to a very high voltage.
So, if you are using the 5v supply for any gear, be aware of this.  I destroyed a nice project running on 5v when using one. Fitting a 5v1 or similar Zener on the 5v output fixed the problem.
14273 2017-09-06 17:10:07 Clark Martin Re: Would one of these car starters work as a QRP supply?
Well few people have any clue what A-h means and even fewer understand it correctly.

Clark Martin

14275 2017-09-07 13:25:22 Brooke Clarke Re: Would one of these car starters work as a QRP supply?

I have a couple of these.

The first one was called a jump starter rated for 8 AH, but when tested at 4 amps it produced 1.8 AH. So maybe 8AH if
the load was a lot lower.
This one has EC5 connectors to handle the high current of starting.
PS I've read recently that these "Jump Starters" Should NOT be connected when the starter motor is used. That's to say
they really are intended to be used a fast battery chargers.
PPS Note you can connect a string of 10 to 12 AA batteries to a "dead" battery and after a few minutes may be able to
start you car.
https://youtu.be/I0utNemFsl8 (this guy has some really good videos)

Have Fun,

Brooke Clarke