New battery jumper

[Lichen 218]

After seeing @LiddlJK's nifty handheld battery jumper/charger gizmo on the Mogollon Rim trip, I just had to have one.  Got this off Amazon for about $100.  It did charge my bluetooth speaker quickly.

[shellback91 2,332]

These are awesome. I have had one for a while now and have used it on more than a few things that needed charged. 

[Curly 1,329]

I bought one to have "just in case" on my recent trip to the Maze district of Utah.  I used it to recharge a small flashlight while on the trail.  Unfortunately, despite the manufactures claims, this killed the battery on the jump start.  This is the one I got, do not recommend. 

https://no.co/gb40

[Lichen 218]

12 hours ago, Curly said:

I bought one to have "just in case" on my recent trip to the Maze district of Utah.  I used it to recharge a small flashlight while on the trail.  Unfortunately, despite the manufactures claims, this killed the battery on the jump start.  This is the one I got, do not recommend. 

https://no.co/gb40

Maybe 1000 amps isn't enough?  I don't know.  This one had good reviews.

[theksmith 5,874]

On 6/13/2025 at 12:07 AM, Curly said:

I bought one to have "just in case" on my recent trip to the Maze district of Utah.  I used it to recharge a small flashlight while on the trail.  Unfortunately, despite the manufactures claims, this killed the battery on the jump start.  This is the one I got, do not recommend. 

https://no.co/gb40

 

i've had good luck with a Noco myself, but it's the larger GB70. i think all the brands are optimistic with their ratings.

 

i got the GB70 not only for the higher crank rating, but because it has a safety override button that connects its internal battery straight to the cables. normally the leads don't actually connect till it sees you've hooked them up correctly, however with a really dead battery (i.e. very low voltage), they sometimes won't switch "on" correctly, hence the need for the override button in certain conditions.

 

my next one will probably be one of the Hulkmans with "-40℉ Start Tech", i.e. a self-warming feature. cold really affects the power on these little guys, so that one can use a little juice to warm itself up before you try to jump from it. not needed too often in AZ, but we always take winter trips in the WK2 to somewhere with snow, so it would be a good feature to have.

Edited June 14, 2025 by theksmith

[4x4tographer 3,667]

On 6/13/2025 at 12:07 AM, Curly said:

I bought one to have "just in case" on my recent trip to the Maze district of Utah.  I used it to recharge a small flashlight while on the trail.  Unfortunately, despite the manufactures claims, this killed the battery on the jump start.  This is the one I got, do not recommend. 

https://no.co/gb40

Does your JL have the 3.6 with the Aux battery setup? They a pain to jump start if both batteries are dead since the main and aux are connected in parallel when you’re not in an ESS event. Some great info, including jump start procedures off of just the Aux battery.

 

I have the same Noco GB70 that K has and it worked for me, but took a while to give enough juice (I was trying to jump with both batteries connected).

 

I ended up “deleting” my Aux battery after I went through a few main batteries that were killed by a bad Aux.

[Curly 1,329]

55 minutes ago, 4x4tographer said:

Does your JL have the 3.6 with the Aux battery setup? They a pain to jump start if both batteries are dead since the main and aux are connected in parallel when you’re not in an ESS event. Some great info, including jump start procedures off of just the Aux battery.

 

I do have the Aux battery, but it is a 48 volt battery (E Torque)  in the rear versus the small 12 volt battery under the fuse box that you had.  I have been wondering if I will be able to eliminate the 48 v battery when it finally fails (7 year warranty).  The Alternator is also different in that it operates as both an alternator and a motor (for ESS). It may need to be changed as well.

[SonoranWanderer 720]

I also carry the NoCo GB70. A few thoughts to add:

 

• To @theksmith's point, these units do not work when they are too cold or too hot. This limitation is due to the Lithium battery technology. They completely fail at -4f, but their full capacity is no longer available below 32f. There's a fade (out) curve as the battery's internal temperature drops from 32 to -4.
• These devices are designed for "old fashion", single battery, standard engine and drive train vehicles. Using them on modern cars with multiple batteries and/or dual motors (electric and ICE) requires special procedures that are vehicle specific. These booster / jumper cable procedures have to come from the vehicle manufacturer, not the battery booster manufacturer. This also means the "generic" instructions in the booster's manual are incorrect for your vehicle and will (likely) result in failure.
• Debugging start issues in modern cars is unfortunately more complex than our beloved "old fashioned" vehicles (1). Case in point, my wife's 4xe will not start the ICE if the 400v battery has any technical fault. Jeep's driver exposed indicators in the dash are not clear about this, although some details are in the book in the glove box that nobody bothers to read, especially once you are in a stressful broken state.
  • @Curly not sure if the e-torque has the same or similar start issues or constraints as the 4xe. The 4xe doesn't even have an alternator. The HV battery's IBCM supplies 12v power for house loads, ECMs, and charges the 12v battery.
• While you can use many boosters as a USB battery, I do not recommend doing this if the main purpose of the booster is to jump start a dead vehicle. As a booster, the device needs it's full capacity, especially the smaller units. Also the "act as a USB battery" circuits in these devices is ancient, supporting only the oldest, very slow USB charging standards. These things don't support QC, PD, etc.
• Like all batteries, booster lithium batteries lose charge naturally over time. Don't forget to top-off charge regularly, lest the fade be below the threshold to boost when you most need it.

 

 

On 6/14/2025 at 5:46 AM, 4x4tographer said:

I ended up “deleting” my Aux battery after I went through a few main batteries that were killed by a bad Aux.

 

Modern vehicles require modern diagnostics and maintenance. Some people delete their Aux battery in JTs and JLs with ICE only drivetrains, but there's a small catch (trade-off) to choosing that option, more stress on and a shorter lifetime for your main battery. The aux battery is part of the larger architectural design change in these engines (systems) that also includes the ESS system, and a "smart" alternator. If I were to delete the aux battery in my 3.6, I would want a hard-wired (not Tazer) solution to permanently disable ESS and also to replace the OEM alternator with a standard (always on) high output unit (2). Instead I (modern maintenance) regularly test my aux and main battery condition and replace each or both as each's CCA approaches minimum thresholds.

 

=====

(1) My high school four-banger (Pinto) used to throw a rocker arm if you pressed the skinny pedal too hard. From the moment of pop and lost power, I'd just put on some gloves, pop the cam cover, pry up the cam shaft and slip the rocker arm back on the push rod, replace the cam cover and be on my way. Can you imagine trying to do a "hot repair" like that in a pentastar? The whole procedure on the side of the road took me like 15 minutes.

 

(2) Irrespective of the auxiliary battery, the OEM / "smart" alternator replacement for the v6 is on my to-do list because of my various aftermarket auxiliary loads. I want my 14.4v in addition to my MTV.

Edited June 17, 2025 by SonoranWanderer

[4x4tographer 3,667]

8 hours ago, SonoranWanderer said:

Modern vehicles require modern diagnostics and maintenance. Some people delete their Aux battery in JTs and JLs with ICE only drivetrains, but there's a small catch (trade-off) to choosing that option, more stress on and a shorter lifetime for your main battery. The aux battery is part of the larger architectural design change in these engines (systems) that also includes the ESS system, and a "smart" alternator. If I were to delete the aux battery in my 3.6, I would want a hard-wired (not Tazer) solution to permanently disable ESS and also to replace the OEM alternator with a standard (always on) high output unit (2). Instead I (modern maintenance) regularly test my aux and main battery condition and replace each or both as each's CCA approaches minimum thresholds.

 

In my application I killed the ESS years ago via a Taser, so no additional strain on the main since there are no ESS events. Though Joe did give me a device to plug into the tow harness that disables the ESS system without the need for a Taser - I just haven't connected it yet to confirm it works.

 

With the aux/tow package I have the HD alternator as well, so not worried there. 

 

Eventually, I'd like to go with a Genesys dual battery solution. 

[SonoranWanderer 720]

22 minutes ago, 4x4tographer said:

 

In my application I killed the ESS years ago via a Taser, so no additional strain on the main since there are no ESS events. Though Joe did give me a device to plug into the tow harness that disables the ESS system without the need for a Taser - I just haven't connected it yet to confirm it works.

 

With the aux/tow package I have the HD alternator as well, so not worried there. 

 

Eventually, I'd like to go with a Genesys dual battery solution. 

 

I have the aux/tow package, it's a bigger alternator than the non towing but it's still a "smart" one. The smart alternator reduces the output voltage as it decides the battery (both batteries if you have them) has enough charge, unlike traditional alternators that have a level voltage output.