Auxillary 12v battery charging procedure

[jasusa]

Hi,

I want to charge my TCH 2008 aux 12v battery using external charger, I would like to know:
1) If I can connect the charger without taking of the battery ?
2) I heard if you take off the battery everything needs to be reset and programmed - smart key fob, TPMS, I do not want to get into this as I want to do it myself.

Can I use an AGM battery charger similar to Schumacher XCS15 directly with the battery installed in my car (without disconnecting) ?
I will ensure not to turn on the vehicle while it is charging.

Here is what happened:

I have 2008 Camry Hybrid (TCH), it was left for about 3 weeks with 15 minutes start every 6 days, but somehow, the aux battery still discharged.
When I came back everything was dead (reading on the multimeter showed 0.84v).

I followed the TCH manual and got the vehicle jump started,
1) Making sure voltage doesn't exceeds 14 volts while jump starting.
2) Removed the jumper cable.
3) Ran the vehicle for about 45 minutes and some 40 miles.
4) Measured the voltage in the morning and it is still at 11.48 V when in power off position.

It looks to me that I need to recharge the aux battery with an external charger to bring it to full charge, but since it powers all the computers, I do not want to disconnect and lose the settings.

Please suggest what is the right approach to charge the battery.
The charger has AGM mode with all the protections to save battery, is it safe to connect to the battery while battery is still connected to the car ?

Please help!

[ukrkoz]

1. 12V battery has none to do with startting; it's auxiliary back up for electronics
2. it is a deep cycle battery. you can possibly choose to fork for a deep cycle charger.
3. no, you can charge it "in situ". without removing
4. i charged mine with a regular charger. it took FOREVER to do that though. those can take a lot of charge in. took me good day and a half to get to green light on charger.
5. smart folks hook up a small 12V back up battery, parallel to the main one, if they need to remove it for replacement or such.
6. in case yours is d-e-d, dead, best replacement is yellow top Optima from Sam's. best price around. does not have hydrogen vent provisions though , with tubes. has only evacuation plugs. you can attach tubes to them, if you want to, with some resin. your call. OEM deep cycle is much more expensive dealership item. shy of $300.
7. you can use regular battery instead, but I'd not recommend this. there's good reason they put deep cycle one in.
8. after fully charged, battery should show above 14V on voltmeter.
9. temp sensor you simply peel off and place onto a new battery. just in case. hope you can still charge it.

[jasusa]

Thanks ukrkoz,

I was able to get an AGM battery charger, it had 10A and 15A mode. I do not have a spare 12v battery pack, and didn't want to reset the TPMS / Computers and Smart Key fobs, so I charged with vehicle off and battery installed/connected.

I chose 10A to deep/slow charge the battery, it took about 7-8 hours to come to 100%, the voltage now reads at 12.85 V when engine is off and ACC is off, when engine is running it is 14.20 V.

I will continue to monitor the reading for next 3 weeks of usage to determine, if the battery is able to retain charge.

Will keep you posted, I used Schumacher XCS15 charger it has AGM mode and it has 10A / 15A mode as well.

If you use the regular slow charger, it will not charge, I heard 2A charge take forever at least 10A of current is need to charge AGM and < than 14 V. This charger maintained current at 12.80 volts, so I am hoping that my battery will not have been further damaged.

This was the first time it got drained, I am hoping this should get it back to work, will keep you guys posted on my battery revival .

Thanks !

[ukrkoz]

you are welcome and glad it worked out.
I mentioned that there is no need to remove battery to charge it.
Well, cheap I am, my regular charger worked, only took a while. Now you have a charger that you will use once in 7 years.

[jasusa]

Yup, I didn't remove the battery, I wasn't sure if it should be charged when installed, that's why I confirmed here
Hmmm, may be not 7 years, but when I go on next vacation , you never know.

-Jas