Hello everyone!
So i bought a HCH2 a few months ago knowing the battery was on its way out, still useable, but lots of charging. Finally went out about a month ago. So i turned off the HV batt with the switch behind the seat after it drained the 12v battery that was in there. I figured it was time for a new 12v anyways so i replaced it and flipped the switch and it was fine for about 2-3 weeks when it finally left me stranded. Super weird how it did it i thought. It started with abs light and steering going out, then a.c. and radio then all the lights on the dash lit up, was driving fine still other than heavy steering. Then it started what seemed like loosing power to the engine and trans, trans felt like it was going in and out of "gears" and the instrumentation was acting like a horror flick, until the whole thing finally died.

I think, cool, ok the ima battery just drained the 12v time to get a replacement. Did that installed it a couple days ago got the 12v charged up as well.

Today, finally actually driving it more than around the block, IMA battery was working amazing way better than when we bought it (understandable). Get to where i am going just fine (about 10 miles or so) and then on my way back about a mile into the drive the Christmas tree of lights start coming on, the radio and a.c. died, and then horror film instrumentation. Luckily it didnt kill then engine and i made it back.

oddly the first time it left me stranded the IMA light was on the red battery light was on (12v?) And check engine light. This time the only light that was on and has been the whole time was the red battery light. No CEL or IMA. Where do i go from here? I have read about possibly a dc-dc converter?

Oh also it is at 11.5ish volts while the car is running from the 12v battery. (Obviously not where it should be)

 

Oh sorry it is a 2006 HCH. With almost 117k miles.

 

When your red battery light is on, your 12V is not charging. Expect to be stranded in short order.

If you have an IMA light, CEL or any other trouble light, Step #1 is ALWAYS:

CHECK THE EFFING CODES!

I really don't understand why people think that any meaningful diagnostics can occur from a wall of text.

When a light comes on your dash, your car is saying, "I have something to tell you. Please ask."

People arrogantly criticize modern mechanics for being nothing more than code monkeys. The simple fact is that an expert mechanic from 30 years ago that could fix a car with nothing but his wits and mechanical awesomeness would have ZERO chances of fixing modern cars. When a car has a dozen or more computers monitoring and controlling various systems, there's just no way to reasonably expect a person to hold that much information about even a single car, let alone different models or brand.

If you've run your brand new 12V battery flat more than 2-3 times, you've either ruined it or likely dramatically shortened its life. Starter batteries don't react well to deep discharges.

In case you missed it... CHECK YOUR CODES. I vigorously recommend O'Reilly Auto Parts. You can always go somewhere else, but your best chances are with someone that uses better equipment. O'Reilly uses Bosch brand code readers. I've witness them read codes that are typically only readable by dealer or other professional grade equipment. MAKE SURE YOURE VEHICLE IS RUNNING WHEN THEY CONDUCT THE TEST. SOME TRY TO DO IT IN ACC OR ON, AND BEST RESULTS ARE WITH THE CAR RUNNING. If they fight you or refuse, insist then that it's done with the ignition in the ON position, NOT ACC.

If you get a snooty "I hate hybrids" person that claims they don't do this for hybrids, refer them here:

https://www.oreillyauto.com/store-services

And ask them where it says anything about hybrids.

Get back to us with the codes, and we can help.

 

Thats just the thing! There are no codes! Thats why im stuck lol

 

So you've had them checked at O'Reilly, paid a shop or used a professional grade code reader? Pending and historical codes don't show CEL or IMA light, but they are there.

Replace your (-) battery cable and the braided ground straps between the engine and CVT and their adjacent mounts.

Check ALL fuses. One of the under-hood fuses can definitely cause this.

 

I have thought about replacing both terminals, so ill do that, the nagative cable and that braided strap! Ill also check the fuses! Thanks!
I cant get the car to a shop anymore idk how far i can actually drive before it does that, and im not super close to anything. But ill get into that tomorrow and put the battery on a tender and hopefully have an update tomorrow! Thanks!

 

Ok so i replaced the terminal for the ground side on the battery, didnt replace the cable but i did check the continuity of all of the grounds that you mentioned and they are all grounded. Checked all the fuses under the hood, all good. And checked the battery while it was ou,t it was low (to be expected since it wasnt on the charger last night.) At 12.05v. Put everything back together and started the car, And its running at 11.55v still. The big fuses at the top right of the fuse box were weird showing 175 and 125 and I think a 135 in there too. I am however missing one of those big fuses, second from the top all the way to the right, it has 5 prongs. So i still am dumbfounded as to where to go from here?

 

We're talking about a 13 year old (-) cable on a honda. "grounded" doesn't mean anything. Resistance means everything. We live in AZ, and my wife's insight was having trouble with the aftermarket cruise control because the (-) cable was causing a massive voltage drop under load. There were ZERO signs of corrosion, and the car is pristine having never been exposed to a humid environment. You'll have confidence in your (-) when you've replaced it. Same with the ground straps. These are notorious issues with Honda. If they've never been replaced, they're step 1 in 12V diagnostics.

The 5 prong things - I believe those are relays, not fuses.

Not sure what you mean by 175, 125, 135. I can't thing of a way those numbers are meaningful.

Did you check continuity of all fuses (not just visual)? Did you check both fuse boxes under the hood?

 

I have replaced the negative cable on the battery and the other 2 grounding straps off the trans and the passenger strut tower. It helped but only slightly. Went from 11.5v with no a.c. to 12.19-12.22v and 11.9v with a.c.. Where should i go from here?

 

Do you EVER see it higher than 12.6? Honda handles charging weirdly, and those numbers can be normal if you're seeing spikes at other times.

Get a Voltmeter and monitor it continuously.

Does it change when you turn your lights on?

And is your 12V light still on?