My portable jump starter is this one from Cen-tech:


I've had it for about 12 months and used it a few times shortly after I got it. However, I haven't needed it in about 7 months. And unfortunately, it was sitting in my garage in a state of low-charge for most of that time.

Well, my car battery died the other day, so I wanted to get this charger back in action. It was obviously out of charge, but when I plugged it in to charge, nothing happened. No lights come on, nothing happens when I press the "battery test" button, nothing. I charged it overnight and nothing seems to be happening at all.

It's barely been touched, so I'm guessing this is because I didn't do proper maintenance on it.

So I guess what I'm asking is whether the jumper is just ruined. Is there any way to tell if it's still viable? Or was it in a discharged state for so long that there's no hope for it?

  • Welcome to Motor Vehicle Maintenance & Repair! Sep 10, 2018 at 21:08

8 Answers 8


The link says it's a lead acid battery chemistry being used in that device. That type of chemistry does very poorly when sitting around idle. Periodic charges after each use and on a schedule thereafter will enable it to remain as healthy as possible, but even then, there's a life span of three to five years.

You should be able to purchase a replacement 17 amp-hour battery and replace it, to restore the device to practical use. Consider also to invest in what is called a battery tender, which maintains lead acid batteries without overcharging them.

A quick check online shows prices for a 17 ah battery sealed lead acid to be in the US$25-30 and up range. Battery tenders run about that price, but even if you replace the device completely, you'd want a tender to keep it healthy as long as possible, otherwise, you'll be throwing it away later.


Yes, it is ruined. Lead acid batteries do self-discharge and get ruined if stored for long periods of time at empty state of charge. Not only that but they are heavy for the amount of capacity they have.

Next time, buy a lithium ion jump start battery. It will have a lower rate of self discharge and doesn't get damaged if left empty. It costs a bit more $$$, but it's worth it.


I put mine in back of my car and never used it for 6 months i charged it but it didnt have enough juice to jump a dead battery. I pulled the back off charged the lead battery with my battery charger for about 8hrs. Put battery back in the pack and viola. Works great and ive charged it up the normal way and still holding up.


I have the same issue on one of them. Bought it charged it and used it twice, now i did charged it all night till full green light then used it then leave it for one or 2 weeks then try again for cell charging and goes back to yellow 2 bar low batt again? What is the issue????

  • Lol this batt chargers really suck
    – Carlos a
    Apr 1, 2020 at 16:33

I pulled the back off. Found the battery was not the issue. Back ground: Like most people I used it a couple of times. Didn't keep it charged. Then tried to charge it up and wouldn't take a charge. Symptoms: - No red LED charge indicator light unless I turned the lamp on. - If I turned off the lamp the LED light went out. And when turning the lamp on again, Lamp stayed dim. No red LED. - Unplugged from outlet plugged back in no light. No LED. - Turn Lamp on. Unplugged then plugged in Lamp on Bright LED charge indicator light on. Investigation/Findings: - After opening the back found the + terminal was found loose. - Disconnected the heavy red and Black cables from the battery and left only the two wires from the charging circuit card connected. - Power adapter at the back on the AC input was providing 17VDC at the circuit card yet the LED was not lit. - Cycled power (unplug unit from the wall then plugged back in) turned LED back on. - Then unplugged then connected and amp meter between one wire (+) the circuit card and the battery. - Plugged the unit in. LEDs on. Amp meter shows .25 Amps charging the battery. Then unclipped one lead breaking the circuit between the charging circuit and the battery. LEDs went out (not charging. No current). Clipped lead back on (still plugged in). No change. Unplugged and plugged back in. LEDs on current flowing.
Conclusion: With the loose terminal and no light on there was zero current being drawn from the power supply circuit of the charger, and no load on the circuit output 9since the battery term was loose (intermittent open). With no load the circuit must sense no load and shut the charging circuit down. Circuit can only be reset by unplugging and plugging back in. With the loose connection, and the lamp turned on, the light provide the load, even with the battery terminal disconnected. After tightening the battery connection current stayed on regardless of whether the light was on or not, because now the battery provided the load, when the lamp was off. Recommendation: - Pull the back off. - Check for a loose connection at the battery terminal before buying a new battery. - Also was unclear if 250mA is the correct charging current. Seems low. But he spec says ~30 hours is full-charge time. So the low charging current of 250mA might be right. Just takes a long time to charge up. Hense the term trickle charge. - Good luck. Always fun to learn about why things break. Sometimes easy to fix.


I know its a little late to post but just had this issue. I did a couple of things from this thread and still had nothing. Hooked a voltmeter to it and had 1.19vdc and had been on charge for 2 days. During the charge no lights would come on nothing except a very very dim yellow flash (no red or green light flash) So i connected it to my truck battery and started it up. Let the truck run for 5 or 6 minutes with the pack turned on. Immediately had all the light indications and work light started working. When i disconnected i put my voltmeter to it and BAM 11.59vdc and the test battery light indicated red. Connected to the wall charger and got the expected red to yellow to green light rotation. As previously stated the battery may not have the CCA to jump start but will update when i find out.


Seems like it’s mostly been covered, but I was going to add that lead acid batteries have voltage drop as they discharge (whether it’s from self-discharge or otherwise). Usually, devices like this will have some sort of comparator circuit that looks at the voltage level of the battery to determine whether it will charge it. This is likely why others have had success charging the lead acid battery separately. Most battery chargers have more sophisticated charging circuits than what you’d likely find built into this.

I just made a video on why a jumper pack might not work, it’s more for the average joe, but hey, you might get a laugh out of it. :-D



I did what the poster above mentioned. Connected it to my truck battery. Turned the booster on and ran the truck for about 10 minutes. Now I have the booster plugged in and it's charging


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