I’m a noob in the battery world and i’m on a learning curve since a few week.
I bought a car jump starter and wanted to test capacity using my accucel 6.
The car jump i bought had a claimed capacity of 16800mah. (it is write 50800mah on it but seller told me it is 16800)
First, i tested it using the usb port on it and applied a 1A discharge on it.
After 5800mah, the test ended and no more power was coming out of the usb port and the power led show no more power
I charged it again and i hooked my accucel to the car jump clip and run a discharge test at 2A
The power bank go down to 8.13 volt getting only around 5000mah
Trying to charge using the regular charger did not work…
So i tried charging using my accucel and after only 3500mah, the cell inflated.
The seller told me that these are not regular polymer lithium and can not be discharge this way.
He also told me that since it is for car jumper, the discharge rate is very low as it need to provide high current to be able to start the car so this is normal that i only get around 5800mah even if the battery is 16800mah
Is this bullshit or does it make sense?
Is there a way to test the real capacity of these portable power bank?
“He also told me that since it is for car jumper, the discharge rate is very low as it need to provide high current to be able to start the car”
Contradictory and the rest sounds like bs. I don’t think I’ve ever heard of a cell that had a higher discharge capacity at high amp discharge than at a lower amp discharge. A car battery charger should be relatively low amp but a jumper needs to be high current to start the car.
As for starting a vehicle that has a weak but still functional battery it can be topped up with a 12V wall wart and I’ve been able to start mine with a power tool battery.
I also tested it on my car, i had remove the clip from the battery and start only using the car jump, i’ve started my car 4 times and still have 3 of the 4 power led light on.
The claimed capacity of 16800 mAh is almost certainly rated for the typical cell voltage around 3.7V. This calculates to 62160 mWh, which equates to 5180 mAh when converted to 12V. I’m not sure why the USB result was so low, but it seems to be correct for the 12V output. As for the cell inflating when charged using the Accucel, is it possible the wrong charging algorithm was used?
Just remember mAh without a voltage reference is not enough to determine total capacity. 1000 mAh at 3.7 V does not equal 1000 mAh at 12V, that’s why capacity should be stated in (milli)Watt-hours.
Yup, they overstated the capacity. As for the lower than expected capacity using the USB output, it wouldn’t surprise me if they were using a very inefficient converter. It could also be related to how you setup the connections and testing apparatus.
As for the safety aspect, my understanding is that once they inflate, that means there’s gas buildup and it will eventually rupture. How serious an event the rupture becomes partly depends on what’s going on at the time, but I certainly wouldn’t be using that pack to jump start my car or charging it inside the house.
You’re forgetting that there are 3 cells in there, giving you 44.4 Wh. At 5V, that would calculate to 8.88 Ah. If you got around 5.8 Ah in your test, then that means about 35% of the power is getting lost somewhere or the cells are not really 4 Ah either. I’m not sure what typical loss figures are for these converters, but 35% is probably not out of line for inefficient designs.
Unless you have a device that is capable of integrating all the values, using the average voltage is the generally accepted practice. That’s why 3.7V is used for a lithium battery which varies from 4.2 down to 3.2 volts. Same for the USB, which is supposed to be steady at 5V. You’re not going to get an exactly accurate result, but it should probably be within 10 to 15 percent. The amount of load will also diminish the capacity result, as a higher current generally causes more losses in the cells and circuitry.
I’m not sure how it’s handled in Canada, but here in the US we can take it to a battery store or the city’s recycling center. However, I would discharge them slowly until either protection kicked in or the voltage is near 0 before taking them in.
Can I ask which brand and model jump-start did you purchase? I know there are tons of them online. I personally have been using the Antigravity Batteries Micro-Start Jump Starter XP-1 for almost 2 years now, and actually getting ready to retire it today for the RAVPower Portable Jump Starter Power Bank w/12,000mAh capacity w/Boost of 500 Amps.
Both of the above are rated at 44.4 Wh, but the Antigravity unit I have always had a very high parasitic drain. So today I received the RAVPower and testing it on my iPad 1st generation and see how it charges. Hopefully the RAVPower will be able to start a car with a dead battery as well as the Micro-Start always has.
I bought a cheap one on aliexpress chinease brand. One is WUHAI the other is generic “HIGH POWER” But they mostly all come from china, even the high costly “branded one” i saw. i tested 2 different one and both had the same capacity.
Most distributor just both them from china and ask to customize it.
Both were able to start my car multiple time even with no battery in the car.
I’m not sure it worth paying 3 times the price for a branded one but i might be wrong
I know what you mean. As you may have mentioned in one of your previous posts, the jumper cables are a direct connection to the Li-poly cells for starting a dead battery and seem to work great. But I’ve found these jump-started are less than stellar when it comes to using them as a USB charger.
When we are away from home, I tend to use dedicated portable USB chargers for our iPhones and iPads, and seem to have great experiences with them.
