12V battery's dead | Precautions for jump starting

[sethz]

Hello all. I had to leave the country unexpectedly to attend to a medical emergency of a faily member who lives overseas and came back 3 weeks later to a 4xe that has a dead vehicle that wouldn't start ( and I had to use the manula keys to gain access as the power locks wouldn't work). I am guessing that the 12V battery just died ( disclosure - I have an antitheft system that consumes some power, so I am guessing that's what drained my battery down).

What's the safest way to get this baby up and running again ? Charge the main battery using the 110V charger or should I get it jump started the old fashioned way ?

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[Tyler-98-W68]

I used a lithium booster, to jump my 4xe the one time the 12v went dead, then just leave the vehicle in accessory for 30 mins, once it times out restart it again, the onboard DC/DC charger will charge up the battery no problem

 

[mwilk012]

Just jump start it. The inverter requires 12v power to function, so you'll need that charged up.

 

[BigMaCro]

I used a lithium booster, to jump my 4xe the one time the 12v went dead, then just leave the vehicle in accessory for 30 mins, once it times out restart it again, the onboard DC/DC charger will charge up the battery no problem

Yeah, Tyler's the 4xe battery charging expert ?

With a dead 12v battery, the systems won't power on enough to even charge or use your L1 or L2 charger, for safety reasons. Doesn't matter how much delicious power is in that big battery under the back seat, its useless without 12v to run the BMS (battery management system). This is the case for all EVs and hybrids I'm familiar with. Not dissimilar to any car starting, really. The great news it it takes hardly any juice to power on the computers, so a little pocket sized jumpstarter is great for it. Then leave it in the ACC or RUN position for a while and it'll charge the 12V battery faster than any other charger you have.

Tips for the future:

1. Keep a little lithium jump starter power pack in your jeep for just this case (and more likely for helping others out!) those things are almost cheaper than decent jumper cables anyway, and you don't need another running vehicle!

2. According to the manual, if plugged into a L1/L2 charger for many days, it's supposed to intermittently wake up and check the SOC and charge if necessary, but I don't think we've witnessed that behavior. It's also supposed to do this to check the battery temperature and heat/cool it if necessary. While this occurs it *should* also charge the 12V battery if it feels like it.

3. In case #2 doesn't work, you could also connect a small NOCO or Battery Tender charger/maintainer. These are great for stored vehicles - I've got one on my WJ right now. One of those little solar panels plugged into the rear 12V socket should also work (make sure the fuse is set so that it's always on as described in the manual)

The Jeep manual says to disconnect it, then it says if you don't disconnect it, very confusing.

 

[sethz]

Thanks all. I was able to jump start the vehicle with a Lithium battery powered jump starter and instead of keeping the car in the ACC mode ( as advised by @Tyler-98-W68) drove teh car for an hour and kept monitoring the voltage of the 12V battery while I was driving and it kept fluctuating between 12.5-12.6V and never went above that. I came back home. locked the car and went back to the car an hour later and the battery was dead again !!! What could be the issue ?

 

[evo8904]

I would swap out the battery. Factory batteries are crap. I’ve had factory batteries die and leave me stranded in multiple vehicles from Toyotas, Rams and Hondas.

 

[Bmeister]

Thanks all. I was able to jump start the vehicle with a Lithium battery powered jump starter and instead of keeping the car in the ACC mode ( as advised by @Tyler-98-W68) drove teh car for an hour and kept monitoring the voltage of the 12V battery while I was driving and it kept fluctuating between 12.5-12.6V and never went above that. I came back home. locked the car and went back to the car an hour later and the battery was dead again !!! What could be the issue ?

Unless 12v battery tech changed on me in the past decade, check the no-load resting voltage (AGM 12v battery) with a proper meter; it should be 12.6v-12.8v. The float (maintaining) voltage is typically 13.6v-13.8v while the full charging voltage range is ~14.2v-14.9v; there is variance among different 12v batteries and of course the health of the internal plates is also a factor in readings.

IMHO, replace your 12v battery NOW before it gets bad enough that you won't even be able to drive it even after you do a jump start.

 

[sethz]

Unless 12v battery tech changed on me in the past decade, check the no-load resting voltage (AGM 12v battery) with a proper meter; it should be 12.6v-12.8v. The float (maintaining) voltage is typically 13.6v-13.8v while the full charging voltage range is ~14.2v-14.9v; there is variance among different 12v batteries and of course the health of the internal plates is also a factor in readings.

IMHO, replace your 12v battery NOW before it gets bad enough that you won't even be able to drive it even after you do a jump start.

The 12V battery is a brand new Odyssey Group 94R H7 battery that I purchased from NAPAless than 2 months ago. Looks like it was a bad battery and need to hit them up for a refund.

 

[Bmeister]

The 12V battery is a brand new Odyssey Group 94R H7 battery that I purchased from NAPAless than 2 months ago. Looks like it was a bad battery and need to hit them up for a refund.

Or an exchange. Look at whatever battery you get for a mfr date. Sometimes batteries sit for a long time and the voltage gets too low and damages the plates. Then when they get a charge it might barely pass muster initially only to leave the purchaser stranded weeks/months later. The AGM batteries are a robust design and can handle deep discharging but, if left discharged too long then longevity is out the window. Do a return/swap and please update the thread after you get it squared away.

 

[Tyler-98-W68]

Sounds like you have a bad battery. There is programming in the IBS (intelligent battery sensor) that once the battery voltage drops below 10v for any reason (when the vehicle is not "on") it will result in a no start condition which requires a boost pack to simply bring the voltage back up, i've shown this in my video of "boosting" the vehicle.

Its important to remember the 12v battery doesn't crank the engine. All it does is provide current to the HV battery which then uses the BSG in the engine bay to turn the engine over. The 12v battery doesn't get hit with a big power draw like on a regular 12v battery that has to crank an engine over.

 

[Hakan]

Just had same issue. 12v discharged in one day. Jumpstart and hooked up a charger overnight. Next day get to dealer.
Measured the battery and if failed the loadtest. Got a new battery on warranty.
Seems the 12v battery is so bad quality it after 1.5 years internally had broken down. Even if it could measure 12.6 volt after bering charged and left to rest an hour. Just applying a smaller loadtest current and voltage dropped badly.

This bad battery also explained some odd behaviours like FORM going active for 1 minute and then go away and other errorcodes coming and going. Too low voltage on 12V do funny things.

Just happy it happened at home.

Will follow the good advice to have a lithium jump starter in the car. Just searching for one with temperature spec that is as high as possible so it can be in the car a sunny hot day. Cheap Lithium do not like higher temersture ....

 

[Bmeister]

...Too low voltage on 12V do funny things...

Yes indeed. Most of the electrical problems I believe stem from a 12v battery that is either outright bad or at the bare limits where voltage is within range but it cannot handle much of a load. There are a significant things running off the 12v other than initiating the HVB to run the vehicle: TIPM/ECM/ECU, lights, HVAC fan, stereo, for example.

But, not all mfr batteries are bad, cheap crap. My WK2 GC is 12yrs old (in service 2010). The secret to longevity is placing it on a smart charger before parking for a couple days or longer. I did the same thing for a Harley; the original battery was 8+yrs old before I sold the bike with orig battery still in service.

Theoretically, the 4xe system should prevent the 12v battery from going bad for a long time.

 

[Tyler-98-W68]

The reason the battery in your WK2 has lasted longer is that it hasn't been subjected to extreme temperatures. Its under the passenger seat. When you take those parameters away its easy for a battery to last that long.

 

[Fudster]

I'll bite here, maybe get my arm handed back to me in my ignorance.

If you've got a dead 12V battery and enough power under the backseat of a 4xe to power a house--at least for a time--why isn't there a method to charge that 12V battery from the propulsion battery while the vehicle is at rest? Is there one?

Wait..let me get into that steel enclosed golf ball pickup machine at the driving range first before you reply. Thanks.

 

[Bmeister]

The reason the battery in your WK2 has lasted longer is that it hasn't been subjected to extreme temperatures. Its under the passenger seat. When you take those parameters away its easy for a battery to last that long.

I doubt that it made much difference. The WK2, JK, JLU were all parked in various unheated/uncooled garages (Michigan UP, Chicago, Chalreston, SC) repeatedly in extreme heat/cold cycles days/weeks at a time between use. The Harley was parked in an unheated shed during winter and subjected to frost. Small data points, but the fact is constant use/charging/float on a battery extends its life dramatically and I've been doing this for many years.

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