Lithium Jump Starter

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Battery in my truck is over 3 years old so I bought this jump starter and put it in my truck 3 months ago.

https://smile.amazon.com/gp/product/B07GN5HHXJ/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

The instructions say to charge it every 3 months regardless of whether you use it so I set my phone to remind me and it went off today so I bring it in and check it and it still reads 100% so I'm guessing it doesn't need charging.

Do these really hold a charge that long?

I was thinking I would charge my phone just to use it so I can charge it back up but not sure it's necessay or is it?
 
Depends on the conditions. If it's stored fairly warm the self-discharge should increase. It's typically 1-2% charge loss each day in good conditions, although I've heard with some cells there could be something like 5% loss in a day when it's fully charged. Here's a chart:

[Linked Image]


https://batteryuniversity.com/learn/article/elevating_self_discharge
 
Originally Posted by Duffyjr

The instructions say to charge it every 3 months regardless of whether you use it


I have something similar.... it is SHOCKING how many amps such a small pack can put out.

I charge mine every 3 months, also (per instructions)
 
These packs hate to remain discharged.

Secondly, these pack prefer not to remain at full charge.

Personally, I keep mine at 50-75% charge. To ensure it has sufficient capacity, I use it to charge whatever, then charge it to 3/4 dots.
 
Originally Posted by y_p_w
Depends on the conditions. If it's stored fairly warm the self-discharge should increase. It's typically 1-2% charge loss each day in good conditions, although I've heard with some cells there could be something like 5% loss in a day when it's fully charged. Here's a chart:

[Linked Image]


https://batteryuniversity.com/learn/article/elevating_self_discharge


That should be 1 - 2% per month, not per day................ for li-ion, which is what the OP mentioned.
 
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I have one I bought from Costco.....I charge it once a year....when I get it out it still has 3 out of 4 bars. I did this also after using it once....same result.
 
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I bought one a year and a half ago and it still has 4 bars. I guess they hold it for a long time, I wont recharge it till it drops to 3.
 
To make these last as long as possible, it's best to leave them charged at 50-70%, not 100%.
 
Originally Posted by nobb
To make these last as long as possible, it's best to leave them charged at 50-70%, not 100%.


This is pretty much what I do.

Most packs advertise the ability to jump multiple times, so 100% SoC isn't necessary.
If it takes multiple attempts to jump the vehicle, then something else is seriously wrong and a jump pack won't be the solution.

With that said, I was there when some poor dude stalled at a stop-light, was jumped using one of these jump packs, then proceeded to stutter and barely make it through the large intersection before stalling at the entrance to a store parking lot. Even with that little bit of juice he almost made it; couldn't believe it! The guy who used his jump pack on this guy's car left, so I had to pull my cables out and charge his battery just enough to get him into a parking space.

His alternator was donezo. This was actually my first experience seeing how long an engine can actually run on just a little bit of charge to the battery.

As an aside: I almost got into a fight with a truck full of bro-dudes, whom we were (partially) blocking, since the dude I was helping stalled, well, where he stalled; couldn't do much about it, and the parking lot we were trying to get him to was UPHILL.

They shouted expletives, but were able to actually get around him without any issue...
33.gif

Like an idiot, I shouted back to either help or shut the heck up (though I didn't use those exact words...) They got out of the truck after parking and marched right toward us, chests all puffed out (they were actually very large men, so I would have been crap out of luck if they came after me).

I think the only things that saved me, were that I was in uniform, they finally saw that the person I was helping was pretty old and that the chances of us pushing his Buick uphill were not in our favor, and the complex had a liquor store, which they diverted into after yelling at me, because, you know...priorities

/rant
 
Thanks all for your replies, I'll throw it back in the truck and check it again in 3 months. I was kind of concerned maybe the digital readout was stuck at 100.
 
I don't really care about the recharge cycle lifespan enough to let a jump starter drop much below 85%.

There's no way I'd exceed the recharge cycle limits before one died of # years age instead, and there are cases where you want as much capacity as you can get like if the reason your battery is low is because your alternator died.

However in that case I'd much rather have a higher capacity lead-acid battery pack... those li-ion packs are usually deceitfully rated by mAh by multiplying by # of cells, not by what it is at the series voltage (12V like the older lead-acid jump starters, or more often 14.4V due to the per cell voltage of Li-Ion).

For example the true capacity of a Li-Ion pack claiming 30,0000mAh could be deceptively claimed to be something like 12 cells x 2500mAh/cell = 30,000mAh while its 4S3P (4 series 3 parallel) real capacity is 3.6V x 4 = 14.4V, 3 x 2500mAh = 7500mAh.
 
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Originally Posted by Dave9
I don't really care about the recharge cycle lifespan enough to let a jump starter drop much below 85%.

There's no way I'd exceed the recharge cycle limits before one died of # years age instead, and there are cases where you want as much capacity as you can get like if the reason your battery is low is because your alternator died.


It's not about the # of charge cycles, lithium ion goes bad naturally just sitting there. If you keep it stored at 100% charge, then after 2-3 years it might only be at 70% of new capacity even if you've never used it. You will get far far greater performance long term out of it by keeping it at 50-70% charge. That's why Tesla batteries are good even after 10 years.

You also don't take much of a performance hit by keeping it at 50-70% charge because lithium ions have high discharge rates, so even at 50% charged you can still start the car. The only difference of storing the battery at 50% vs 100% is that you'll get less # of starts out of the battery pack but IMO that hardly matters in this application.
 
I was off about the self discharge rate, as I was thinking NiMH. However, with a lot of these low power jump starters one might try hooking it up for a bit where it will transfer a bit of charge to the battery before attempting a start.

Also, there's a tendency to fudge the percentage readout on most devices with lithium rechargeable batteries. Some devices (especially cell phones) display 100% until it reaches about 95% and then displays a percentage number proportional to that 0-95% range. At 50% it's really at 47.5%. Also 0% isn't the absolute floor, but where they shut down to prevent deep discharge. A lithium battery discharged too deep can be damaged to the point where there's significant capacity loss or even where it will refuse to take a charge.

I've checked my phone battery with a computer program that displays the raw charge percentage. So I could see how it fudged the display.
 
I bought one a couple of years ago and I use it more often to boost friends/family vehicles than anything else but I keep it fully charged in the back of my van should I need it. That said I pulled it out the other day to check the level as the last time I charged it was 9 months ago and it was still at about 90% charge. It says it can start a car at 25% charge or more so it still had lots of juice left.
 
I bought a cheap mini 12V solar panel to trickle charge my power pack in the trunk. I never need to recharge it. But I'm not sure if this will work for the lithium booster.
 
Been keeping an eye on this since I bought it and just turning it on and checking the percentage may not work for this one. I finally had a chance to use it, co-worker needed a jump. When I first turned it on it said 97%, as I was waiting form him to connect the cables it kept dropping, by the time I got it hooked up it was reading 76%. After the jump when I got home I checked it again and it was down to 40%. While it did a good job of getting his little four cylinder going I think the read out is faulty or not what I expected. At least I know this now and when I check it again in a couple months I'll throw my phone on there and see if it changes.
 
Quote
If it takes multiple attempts to jump the vehicle, then something else is seriously wrong and a jump pack won't be the solution.


Not necessarily, if you're dealing with an older vehicle with a carb and ignition points. Those can be tough to start on a cold day especially if they've been sitting around for a while, or if you flood the engine with too much pumping the gas pedal against a closed choke. Nature of the beast.
 
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