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Another battery question

Jerry Gaffke
 

Some addendums to my suggesting the use of a Gooloo 2000 for portable power.

First off, the reviews all suggest it does well for the intended purpose of starting 
a vehicle that has a low battery.  And that it is reasonably safe.

I just measured mine, it weights about 1.4 lbs, not the 3 lbs they give
as the shipping weight with packaging and accessories.

The Amazon webpage for it says it's a "2000 Amp Car Battery Jump Starter",
Lettering on the device says "500A(3s) 400A(5s) 2000A Peak".
Amazon price at $69.99 is suddenly cheaper than Walmart, that changed since yesterday.

They claim 19800 milliamp hours.
I would read that as 19800 mAh worth of 3.7 Volt cells,
so divide by four and it is roughly 5 Amp-hours at 3.7*4=14.8 Volts.
This is typical of all the other auto jump start devices, they all have to play
the same game or they lose their mostly naive customers.
The Gooloo also says it is 73 Watt-hours, which checks since 73Wh/14.8V = 4.93 Amp-hours.

It does have a port on it with lettering that says "15V 10A", I haven't yet used it.
That port has a standard 5.5mm coaxial power connector with a 2.1mm pin.
Nice that it's a standard connector, but those are typically rated for a max of 5 Amps.
If you want much more current than that, perhaps best off using the provided
jump cable and appropriate fusing. 
Output voltage will typically be between 15 and 12 VDC depending on charge state.

Not bad.
73 Watt-hours means you could run a rig drawing 10 Watts continuously
for 7.3 hours.   Adequate for most ham QRP outings.
Or a rig drawing 400*12=4800 Watts for 5 seconds, at which point the battery would overheat and shut down.
Or maybe start your car some dark night.

That 10 Ah Lumenier that Don pointed to has almost exactly twice the claimed capacity,
    10 Ah at 14.8 Volts would be 148 Watt-hours.
The Lumenier is also double the price, and that does not include a proper charger with BMS for it.
However, the Lumenier should run a 3700 Watt rig for 2.4 minutes, which could actually be useful.
And might start a small car in a pinch, though be careful as it probably doesn't have overcurrent protection.

Jerry, KE7ER



On Wed, Nov 23, 2022 at 06:08 PM, Jerry Gaffke wrote:

Speaking of fast discharging, it is amazing how well the new breed of auto jump start
batteries work.  I have a Gooloo 2000 which I rather like.  In addition to being able to
jump start an F250 diesel, it has a 15V 10Amp port out the side to run a small transceiver.
It charges slowly through a USB-C port.  Fast discharge is not possible unless you
plug the jump start cable into the side of the pack.  Includes a flashlight and several
USB power out ports.   Weighs 3 lbs.  Walmart sells it for $78.  Might save your bacon
if you leave the headlights on while working Parks-On-The-Air.  Using the battery off a
shop tool also makes good sense to me.  Why buy an extra battery for ham gear
when you can make use of a battery that is used for other purposes?  A high volume
consumer product is often cheaper than a niche product.
Don LeRoi
 

Andy,

Thanks for your comments. 

I would suggest that RC battery packs without BMS are unsafe in the hands of people that don't understand the technology.  For example, there's nothing to prevent someone from overcharging them by using the wrong kind of charger.  Over-charging can cause thermal runaway and result in fire.  Even on the right charger, if someone doesn't appreciate the need to balance the cells, one or more cells may eventually become seriously over-charged.

I build multi-rotor RC helicopters for a living.  I don't know of any that disconnect the load when the battery drops below a certain voltage.  In my view, that would present another safety risk when the aircraft falls out of the sky.  In my early days of flying electric aircraft, there weren't suitable Li-Po batteries and chargers available, so we used Milwaukee V28 tool batteries.  However, we stripped out the BMS so that they couldn't shut off in-flight.  Ultimately, we removed the 7 individual V28 cells to assemble our own 3S and 4S battery packs.  Today, my flight controllers start the aircraft toward home at a certain low voltage threshold and land it if the voltage drops below the next threshold.       

Cheers,
Don
   
ajparent1/kb1gmx
 

Never hand a hammer to someone that's never used one they will hurt
themselves, usually applied to many tools.

Technology masks the hazards but can and often do make us safer.
So to me the idea of low battery go home makes sense as it performs
battery protection and reduces other hazards.

Never said BMS/BMB were he only way just its common and most
cases its the way to do it.  As someone that flew electric models
and real aircraft sudden fan stops make for much sweat.


Allison
------------------
Please use the forum, offline and private will go to bit bucket.
Jerry Gaffke
 

Don,

Years ago, I occasionally used a small inverter type DC arc welder to charge a 24v offgrid lead acid battery bank.
Could set the current to something appropriate, this was way faster than any other charger I had available.
Worked great for me but I don't recommend this technique to others, they might try using their AC buzzbox
or not guess right on which clamp is positive. 
If overcharged and/or poorly ventilated, the outgassing could have become quite dangerous.
As Andy said:   "Without automation, we become the management system - the battery is as dangerous as we are."   

Here's what Andy had to say about BMS's on RC aircraft batteries:
"RC batteries aren't unsafe because they don't have an i ternal BMS. In RC use, management is split between the charger on the ground (charges, controls voltage and current, and balances). In the air, the speed controller monitors battery voltage and disconnects the load. The only weakness is cell level low voltage isn't monitored (though the low voltage disconnect is conservative for that reason)."

So they keep the BMS as part of the charger, not part of the battery.  This reduces the weight of what goes up in the air, which seems ideal.  But anybody using one of those batteries (especially those charging at 25C!) should be using a BMS during charging.  The operator (or aircraft firmware) needs to be smart enough to land the thing safely before the battery expires.

Perhaps you object to this passage:
"My bench battery for the past 12 or so years was a 'naked' 4S 10 Ah LiFePO4 pack made from PSI cells. I didn't worry about low voltage monitoring because I seldom discharged to 50%. I connected to an analogue BMS when charging with my bench PSU."

So about the same as the RC battery, he charged with a BMS, and was careful not to discharge too far.  Discharging to zero might ruin the battery, but would not be dangerous.  Doesn't say if he fused it to limit the maximum current, but that's about the only additional safety measure I'd recommend.

Jerry, KE7ER
Don LeRoi
 

Jerry,

I don't object to anything that Andy is doing because he knows what he's doing.  My concern is for people that don't know what they're doing.  That's all. 

Cheers,
Don 
Jerry Gaffke
 

Indeed, none of us have any argument with that.
Batteries concentrate lots of energy in a very small space, that makes them dangerous.
Safest to buy a complete battery system and charger that is
well reviewed and shows few failures, and then thoroughly read the documentation.
The alternative is, as you suggest, to make sure you know what you are doing
before proceeding. 

 

On Sat, Nov 26, 2022 at 05:38 PM, Don LeRoi wrote:

I don't object to anything that Andy is doing because he knows what he's doing.  My concern is for people that don't know what they're doing.  That's all. 

AndyH
 

Thanks Don. I'be only flown fixed wing RC, so am not familiar with how powered lift devices are managed. The ESCs I've used reduce or cut power to the motor when the battery gets low. Since servos are connected to the battery directly, they continue to function after the prop stops spinning. It makes it easy to glide back for a battery swap if one loses track of time.

Andy
Richard E Neese
 



On Nov 27, 2022, at 12:15, AndyH <awhecker@...> wrote:

Thanks Don. I'be only flown fixed wing RC, so am not familiar with how powered lift devices are managed. The ESCs I've used reduce or cut power to the motor when the battery gets low. Since servos are connected to the battery directly, they continue to function after the prop stops spinning. It makes it easy to glide back for a battery swap if one loses track of time.

Andy

AndyH
 

Yessir - the 10 Ah PSI cells are rated for 10C charge/discharge. One of the cell interconnects is a 100 A fuse, which can be seen in the photo.  Radios had their own fuses as well. The battery started as a test pack and has a couple sets of balance leads for different BMS and LVC devices. The bench-top spaghetti monster. hihi



On Sat, Nov 26, 2022 at 12:32 PM, Jerry Gaffke wrote:

Perhaps you object to this passage:
"My bench battery for the past 12 or so years was a 'naked' 4S 10 Ah LiFePO4 pack made from PSI cells. I didn't worry about low voltage monitoring because I seldom discharged to 50%. I connected to an analogue BMS when charging with my bench PSU."

So about the same as the RC battery, he charged with a BMS, and was careful not to discharge too far.  Discharging to zero might ruin the battery, but would not be dangerous.  Doesn't say if he fused it to limit the maximum current, but that's about the only additional safety measure I'd recommend.

Jerry, KE7ER
Jerry Gaffke
 

Richard,

That Lossigy 20AH 12V LiFePO43 looks very interesting.
Includes a BMS inside, should be as easy to use as a lead acid battery.
Has 4x the Amp-hours of my Gooloo (though the Lossigy won't start my car!).
Web hits on "Lossigy" seem mostly positive.
A comparable Bioenno is nearly 4x the price.

Jerry, KE7ER
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