Here's volts, amps, plus some opinion and observations regarding the NOCO GB70 Jump Starter...

Test vehicle: 2008 JK, 0w-40 oil, cold @ 55 Deg F ambient. M25 fuse pulled to disable the fuel pump and prevent starting.

GB70 Jump Starter data

• Normal battery disconnected and GB70 reverse polarity protection bypass engaged to power up the output leads.
• 12.1 V before cranking (at full charge it read 12.3)
• ~230 A peak (momentary at initial cranking)
• ~135 A during cranking for 4 seconds
• 10.0 V cranking, just before stopping
• 11.9 V after cranking

Normal battery data (Odyssey Group 34, 850 CCA)

• 12.6 V before cranking
• ~250 A peak (momentary at initial cranking)
• ~145 A during cranking for 4 seconds
• 11.3 V cranking, just before stopping
• 12.5 V after cranking

Opinion and observations
The normal starting battery data is for comparison. The Odyssey is a beast, here's a link to some testing on it: https://www.jk-forum.com/forums/jk-w...9/#post4244462 .

10V while cranking at 55 deg F with the GB70 seems decent. There's some headroom for colder temperatures. Even though cranking was slightly slower than with the Odyssey battery, it was plenty fast.

The GB70 didn't feel any warmer after cranking. Based on the output voltage, it apparently uses a series 3 cell lithium battery. Even with the bypass engaged, it wouldn't accept any reverse current -- leading me to speculate it had some schottky diodes on the output. That would also explain the full change terminal voltage reading ~0.3 volts lower than expected for a 3S LiPo battery.

The 2008 JK FSM specs the starter at 150-200 running amps with a warm engine. Neither the voltage or peak amps are given. It's interesting that the amperage measured here while running the starter on a cold engine are slightly less than 150 -- maybe it's the 0w-XX oil or maybe the clamp-on amp meter was reading a little low.

The GB70 looks like a good quality unit with plenty of internal protection. As with most things like this, some of the specs are unusable or unrealistic. The only use for numbers like 2000 A and 15700 Joules 3S (3S means over 3 seconds, and 15700 Joules 3S equates to 5233 watts for 3 seconds) is wondering how they were derived.

The GB70 detail cut sheet is here: NOCO GB70.pdf

Cheers

 

Thanks for the info. I had just looked into the GB40 for this past weekend but decided to wait. Might save my money and step up to the GB70.

 

Check out AutoZone.com -- There was (and is) a 20% online discount over $125 plus free shipping. Don't ask me how many hours were spent finding the best price...