Battery tenders and 3.6 eTorque?

amstel78

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Perusing the owner's manual, it mentions nothing about trickle charging the battery; just how to jump start. I'm assuming (it better be since my tender has been connected since yesterday) it's fine to connect the charge leads directly to the 12v wet cell under the hood? I'm asking because I'm really not sure how the lithium battery ties into the whole circuit as far as charging goes.

From what I understand, the BSG charges the Li-Ion battery under the chassis, which in turn charges the 12V led acid battery used for the old school starter. Running things in reverse by having a tender connected to the 12V battery, will the circuitry top up the lithium battery or is it isolated in this instance?

I often don't drive for a week at time and my garage being poorly insulated, I usually leave whatever vehicles I have in there connected to a smart battery tender. Just don't want to blow up my brand new JLUW in the process lol...
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VNT

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Good question for folks who use trickle charging, will follow this thread.

I have my two Wranglers in back yard for winter under covers with Battery tender hooked up to keep the 12v main and ESS batteries charged.

Not sure what if anything the charger would do for the 48V, have to ask my freind what they do at the dealer for units sitting on the lot.
 
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amstel78

amstel78

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For what it's worth, my charger is in float mode so it definitely topped up the 12v battery. Nothing appears out of the ordinary and the car starts and drives just fine. What is interesting is the battery gauge in the cluster; right after coming off the tender, it shows 14.3v. I always thought this gauge displayed the output from the alternator/generator and dropped if the battery was charged?

I guess another concern is, if the circuitry doesn't allow bidirectional flow of power from the 12V to the 48V side, if the Jeep sits parked for a long enough time, what happens to the Li-Ion battery? Those batteries shouldn't be discharged completely otherwise it'll just kill the cells.

Edit: @JeepCares - is there any way you could find out from engineering about the use of a tender, and/or how to maintain the Li-Ion battery for extended periods of non-use?
 
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neil

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I plug my 12a odyssey charger into my wife's 3.6 w e torque.

I don't believe this does anything for the 48v battery other than next time you start it it does not have to work as hard charging the 12v.

Li-Iion can go months/years in a storage state. Different formula, different care. I actually have a programmable DC charger that will charge a 48v, your tender can't and won't. I don't believe jeep has stated this 48v is user serviceable.
 
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amstel78

amstel78

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I plug my 12a odyssey charger into my wife's 3.6 w e torque.

I don't believe this does anything for the 48v battery other than next time you start it it does not have to work as hard charging the 12v.

Li-Iion can go months/years in a storage state. Different formula, different care. I actually have a programmable DC charger that will charge a 48v, your tender can't and won't. I don't believe jeep has stated this 48v is user serviceable.
Lithium ion batteries do have a pretty long shelf life as long as they're kept at roughly 50% charge capacity in a temperature stable environment. It's usually the charge and discharge cycles as well as running the battery below a certain voltage threshold that kills them prematurely.

I'm curious as to what sort of chemistry Jeep uses; is it Li-ion, Li-poly, or something else? Anyway, my concern was less about the actual lithium battery but whether or not it was safe to trickle charge the wet cell 12V via a tender with that lithium battery somewhere inline with the circuit.

Knowing if a tender can also keep the lithium battery from dropping below its minimum voltage threshold would be a bonus.
 

neil

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It's safe. I've actually hooked up and charged with several chargers on her battery with no issues.

I would like to know chem as well, but alas.

Charging the wet does nothing for the 48v other than the possibility of taking the load off of of charging a 12v post crank.
 
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amstel78

amstel78

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Noticed something strange today. Took the Jeep off the tender, started the engine, and watched the cluster voltage readout start at 13.1 and climb to 14.2v. I then drove around the block to do a chalk test on my tires. After returning, I went to check the 12V battery with a meter. It read 12.5V with the engine off. I'll have to wait an hour to make sure the computers and CAN bus have all gone to sleep before testing the battery's resting voltage again.

That said, resting voltage should be closer to 13.2V right after coming off the tender. If it stays at 12.5V after several hours, then either the battery is shot, or there's a load. I doubt the battery is bad otherwise my tender would have indicated and not gone into float mode.

For those with eTorque motors, what does your cluster battery voltage readout usually indicate after 30 minutes to an hour of engine runtime?
 
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