I was playing with some used jump starters, they look like a very useful source of power when you need it.
A particular one looks very useful, it has a USB 5V port, 12V Cigarette lighter outlet, and even a 3-prong outlet. It is just slightly used for around 1-2 years.
(EDIT: it also has a compressor switch on the back that maybe the one that prevents the unit from getting charged.)
Short story:
Even though it shows some juice power, I can’t seem to be able to recharge it.
Long Story:
The jump starter doesn’t have a Gauge, to show you capacity, just an indicator
RED, YELLOW, GREEN lights
Right now it is on RED, meaning it is almost discharged.
Charging it is simple, just plugin an extension cord.
I looked up the manual and when charging, the RED light supposed to be ON, eventually changing to yellow and green.
So I plugged in an extension cord, to charge it up, but won’t charge even in 24 hours, meaning the RED light won’t even light up showing it is taking the charge. I tried a bunch of cords, and nothing, I tried to charge a different jump starter and no problem with that one.
The jump starter must have some juice, I used the USB, and 12V cigarette and it powered up my devices with no problem. just don’t want to kill the battery completely.
Do you have a DMM to measure the voltage at the leads. I suspect one of the batteries inside is very low or dead.
It might be possible to disassemble the charger and charge just that one battery or bank.
It’s probably using a protection circuit and reading either a bad cell or bank and could be reading to low of total pack voltage.
Did it come with a manual to see if it has anything about the battery being low.
I looked at the small print in the manual, it did have a bunch of related suggestions
“when the battery is overly discharged, the GREEN LED lights up when charger is plugged in which indicates high impedance stage”
This wasn’t my case.
Another one:
“it will not charge if the compressor switch is turned on”
I didn’t even notice, but it has a compressor switch in the back. obviously it wasn’t on, but
I just popped it On and OFF twice and then I noticed the RED charging light came on. so this seemed to resolve it.
I guess the whole issues was that the compressor switch was in between on and OFF?
I think you are probably right wle.
If you have a car battery charger, you might connect lead to lead and see what the car charger says. It might even charge it back up to where the factory charger will work. Like wle said though, usually if they have set discharged for a while, they’re toast. Sulfation has probably already set in.
Almost all of these larger jump boxes have a 12v 18Ah sealed AGM battery in them.
If the battery is below 12.2v or so and it has been sitting like that for more than a few months or 11.5v for a few weeks, it it probably sulfated at least to some degree.
Check the voltage at the terminals and report back with that and how long it has been resting in that state. Charging a battery with a regular charger (or what comes inside those boxes) after it has sulfated will only permanently ruin the battery.
You will need to use a desulfating style charger to have a chance at bringing a sulfated battery back to life.
I had/have(?) a Peak cobblestone-with-handle. High impedance. Charge it forever, will indicate “charged”, throw a taillight across the leads, glows about half-brightness. Forget about jumpstarting even a Matchbox car. It just sat too long without a charge.
The thick leads are necessarily bolted right to the battery, so you can clip those to your car’s battery and have the alternator try to top it off like any other Pb-acid battery. The extension-cord dealy is only if you want to charge it in the house.
It’ll read a decent enough no-load voltage, but is probably sulfated to Hell, so is pretty useless without a battery transplant or at least some heavy-duty fizzing on a desulfating charger.
And even so, I wouldn’t trust it enough to actually lug it around in a car.
that means no dead cells
but they could all still be equally sulfated - symptom would be ‘will not charge or start a car though the voltage shows normal or high’
Assuming this is an AGM battery…
That is a little high even if it has been recently charged.
Have you checked your voltmeter for accuracy?
An AGM battery fully charged is 12.8v - 13v. Usually 13v only for a few hours after being charged then it drops some.
It could have been overcharged at some point and some of the electrolyte boiled out.
Do you know if an outboard charger was used to charge this and if so what model and how long was it charging?
It could still work, but might live a little shorter life and have less power than new.
I’m not sure that voltage alone tells you that the battery is still good. A load test would help to verify that the battery has more than just a surface charge.
Thanks for pointing that out. I would probably use it just for charging other devices, maybe a laptop.
You are right 13.23 it is odd, the other jumps starter had 12.78. I will have to check the voltmeter I am using and then check again.
It seems that the only way you can charge it is just plug it in the wall so I don’t think it was charged with any desulfating charger or a trickle charger
I was thinking maybe I can try charging it with a male to male 12V cigarette lighter type of cable from the car.
If the battery isn’t completely sealed you can clean it out. You pop the caps off. Pour the acid into a bucket you’ll need it again. Fill each hole with Epsom salt and distilled water. And slowly charge it. I’ve seen them start a car with the Epsom salt and water. But after that drain the Epsom salt and water. Rinse with distilled water. Then put your battery acid back in and charge it again. And the lead plates will be a lot cleaner. One guy on youtube kept his same car battery for 20 years doing this until the lead plates were just to bad. Wear some gloves when doing this obviously.
