Hello all, I just bought a 2004 civic hybrid with 187k miles for cheap from a friend. I'm debating whether to clean it up and give to my niece, or clean it up and sell it. The car is not throwing any codes and drives well, but the 12v battery is weak from sitting for 2 mos. I've also read a little bit about "balancing" the hybrid battery pack. The PO tells me the hybrid battery pack was replaced by Honda under warranty, but I think that was about 5 years and probably 50k miles ago.

Questions:
Can I remove the 12v battery to place on a battery charger with desulfator? Will the removal of the battery make it throw codes? Can I just hookup the desulfator charger to the battery while it's still in the car without fear of damaging any of the hybrid battery pack stuff?

Is there a way to "balance" or otherwise cycle the hybrid battery without having to purchase a special charger?

Thanks for any input!

 

1) Yes, but don't bother.
2) Shouldn't
3) Yes, but don't bother
4) No

Concerning 1 and 3 - If the 12V is more than 2 years old, just replace it. It's about $100, and the reliability will be better than any you'll get from charging. Furthermore, desulfators are spotty at best. Sure, you may swear by them, but I have attempted recovery of about 2 dozen 12V batteries using just about every method including desulfators. ALL of my data is based on discharge testing, NOT voltage, i.e., I discharge the battery to measure the actual capacity. At best they restore to about 50% of rated. I just had a a 3 year old Exide come back from being very weak to about 60% of new rated capacity... and then it dropped a cell sitting on the float charger at 13.5V without warning.

If you've never measured the actual capacity of a battery following your "reconditioning/recovery" efforts, i.e., discharge it at 25A until 10.5V to confirm the reserve capacity rating, you have ZERO data on which to base your claims. Getting a battery or cell to recover so that it holds voltage is trivial. Getting it to deliver anything near its rated capacity is very challenging.

The quality of all brands of modern automotive lead acid batteries is in the crapper - particularly the Johnson Controls batteries made in Mexico (multiple brands, including Optima, and about 80% of the batteries sold in the U.S.). They aren't worth the effort to recover when they get spotty, and the reliability of a new replacement - even though they aren't what they used to be - is better than what you get with any recovery efforts.

EDIT: If it comes with a 151, see if you can get a 51 in it. 51 have about 40% more capacity than a 151, they can generally be made to fit, and they cost about $10 difference (sometimes cheaper). I've done it on an HCH2 and a Fit. It's also common practice on a G2 Insight. It's also very possible the HCH1 already has one by default...

 

Thanks S Keith! I'll leave the battery in the car and give it a full charge. It looks relatively new, so I'm hopeful it will be good with a full charge.

 

The 12v battery is very weak- after 8 hours of charging, it settles down to 10.6 volts. I think I can get it replaced for free via the PO, but that may take a few days. The car seems to start and drive normally, even with the low voltage on the 12v battery. Is it ok to drive it this way, or should I keep it parked until I can get a new 12v battery in it? I've got a jumpstarter battery pack, so the car dying on me isn't my concern, my concern is that I don't want to damage the hybrid battery pack, or anything else on the car, by driving it with a bad battery.

Thanks!