mmrmnhrm Posted July 22, 2009 Report Share Posted July 22, 2009 Wondering what the "correct" way to test a 12V battery for charge-holding ability is. My car's dropped over 10% on the mpg numbers this summer, and at 3 years old, I'm guessing Honda's tiny 12V battery is biting it, but the dealership claims it's still way above spec (388CCA actual, 290CCA spec). All they did was hook some sort of meter to it without disconnecting it from anything else. Is this normal, or (as I suspect) was my hybrid battery pack, which charges the 12V battery, "boosting" the reading? Quote Link to comment Share on other sites More sharing options...
CRed05 Posted July 22, 2009 Report Share Posted July 22, 2009 Not sure about hybrids. But on regular cars you dont have to disconnect it from the car. I dont think your car will charge the battery when its not running. Does it still have a regular car battery alongside the hybrid batteries? If so its probably time to replace it. 3 years is about the average time for a battery, but if the CCA is still good it should still be ok. But I dont see how Cold Cranking Amps would hurt your mpg. Quote Link to comment Share on other sites More sharing options...
Dave1647545494 Posted July 22, 2009 Report Share Posted July 22, 2009 I would disconect the starting battery in a hybrid to test it any autoparts store can test it for you free Quote Link to comment Share on other sites More sharing options...
mmrmnhrm Posted July 22, 2009 Author Report Share Posted July 22, 2009 Chris, at least in the 2nd gen Civic hybrid, there is a regular (albeit rather small) 12V battery to handle "legacy" type equipment... headlights, turn signals, Garmins, etc. It pulls energy from the 158V hybrid battery pack, which in turn is charged while braking or "forced regen" when the car sucks energy from the gasoline portion of the crankshaft to dump energy into the NiMH pack. At least in this design (dunno about Toyota's HSD), there is actually no alternator at all. The reason a dying/dead 12V battery would fsck up my mpg numbers is that it would constantly be calling for juice out of the hybrid battery, which in turn would be sucking it from the hybrid motor coupled to the crankshaft. Unfortunately, while my dash would light up like a Christmas tree the moment someone wrong was detected within the hybrid battery/electronics, there isn't jack to say whether or not the 12V is operating normally, since it'll always read 13.8V (or whatever Honda set the float voltage to) courtesy of the hybrid battery. Dave, I went to Autozone yesterday for a check, and they couldn't find any specs on the thing. Apparently since the 12V battery doesn't start the engine the way a regular Civic does unless there's something really wrong (or it's frostbitten nipples cold), the necessary info was never loaded into their system Quote Link to comment Share on other sites More sharing options...
Dave1647545494 Posted July 22, 2009 Report Share Posted July 22, 2009 have autozone test it at 290cca or stop by NTB we offer free battery tests as well you even get a cool little printout when its done Quote Link to comment Share on other sites More sharing options...
CRed05 Posted July 22, 2009 Report Share Posted July 22, 2009 Interesting. I guess in that case I would take the battery out and have it tested. I remember back when I worked at Sears Auto Center that we had handheld testers that we would test the battery while it was still in the car, but also had stand alone units to test batteries more thorough and outside of the car to see if they charge properly, hold charge etc. It would take a few minutes but that should tell you for sure. Quote Link to comment Share on other sites More sharing options...
Guest Removed Posted July 23, 2009 Report Share Posted July 23, 2009 loaded testing is IMO, the best way to test it.. i have a 125amp loading tester to test batterys.. after being charged..or the car ran. shut everything off, and burn the head lights for 1 minute to take the surface charge off of it.then load test it.. i hate these little testers that dont load the battery and guess at it. granted some of the info they give you is nice, but did it load test th battery? granted it trying to read battery volts when your cranking it, but that only really test starter draw on the battery. some starter dont draw more the 50 or so amps. Quote Link to comment Share on other sites More sharing options...
mmrmnhrm Posted July 23, 2009 Author Report Share Posted July 23, 2009 Think I'm going to dig out the radio reset code and swing by Billingsley tomorrow evening so they can pull and deep-cycle test... the gist I'm getting is that what Honda did was, at best, checking surface charge, and with the hybrid module possibly dumping power from the 158V pack to the 12V, taking the 12V out is the only sure way to know I'm getting a good reading So assuming they say it's marginal or fails (it's entirely possible to start this car with a crap 12V), what's a good deep-cycle battery these days? NTB house brand? Interstate? Optima? Reason I spec deep-cycle rather than fast-discharge is that, again, all 12V power in the car derives from the hybrid system instead of an alternator, so the 12V doesn't get hit unless there's something seriously wrong and it's gotta last, or it's frosted runny nose cold. Quote Link to comment Share on other sites More sharing options...
Dave1647545494 Posted July 23, 2009 Report Share Posted July 23, 2009 ntb house brand is interstate with our sticker Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.