Massive battery drain during install

Gl00mybear

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Hi Everyone,

I just installed my A129 Duo tonight with the HK3 hardwire kit on my 2019 CRV. Everything went pretty well, but when I went to turn my car on to drive it back to the garage it wouldn't start. TLDR: my battery dropped from 12.2V to 6.8V over the course of about an hour. This is probably a massively stupid question, but is it more likely this was a result of us having the car on ACC power for an extended period of time, or do I have a short circuit somewhere? Or would a short circuit have had a bunch of sparks and melting wires?

We'd used a voltage tester towards the beginning of the install to check for battery versus running power, and I got 12.2V from the battery fuse (#33, driver's seat sliding) and a minute later 11.8 from the ACC fuse (#22, daytime running lights). That seemed like a big dip to me, but I chalked it up to not being directly connected to the battery. After we got the fuses connected and the front unit turned on, we started working on cabling for the power cord and rear camera connection. I think that was about 45 minutes to an hour, and I don't believe we had ACC mode on, but the shop was a bit noisy so I may have missed the signs of more things being on. I doubt the AC was running but I won't bet my life on it. Doors were open most of the time, however.

Anyhow, I went to turn the car back on after we got the wiring done, and the instrument panel was going a bit haywire. It took us a few minutes to diagnose the low battery, and after we hooked the charger up to it we reconfirmed the taps were oriented correctly (we did pretty much exactly what Anthony Mo did in his dashcam install video).

So, is it feasible that running an unknown number of accessories for about an hour could drain a battery that much? Is it possible that we did something that would have caused a short circuit and a power drain? Are both feasible? Or do neither of these make sense and I just have a haunted battery?
 
As you have a Honda I recommend using the fusebox 'option connector'.

This is a dedicated port in the fusebox for connecting accessories under a smooth safe way.

It has full details including the plug and pin outs.

 
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'So, is it feasible that running an unknown number of accessories for about an hour could drain a battery that much?'

Yes.

You would be surprised how much all the various things add up. Look at the car's manual and the list of circuits and there is the computers running the car.

My neighbour has a Honda and I was surprised how small the battery is, 47AH. It doesn't take much to drain that.


Secondly, you have another issue. Your voltage at the start of the job of 12.2v is too low. I would basically consider that as a flat battery. At the very least I wouldn't want to be in a remote area.

If the starter battery is 4 years old it is on borrowed time. It may start the car but they do lose about 20% of their capacity per year.
 
I'm leaning towards a marginal battery being, at least, partially at fault. 12.2V is getting pretty close to the low end for being a full charge (12.6V is generally considered a full charge), plus going to 11.8V almost instantly suggests a failed/failing cell. A load test will confirm that pretty quick. Sounds to me like a new battery might be in your future pretty soon.
 
Thanks for the replies, everyone! I think you're right that I've got a new battery in my future; it charged up to 12.2V last night, and was down to 11.9 four hours after taking it off the charger. Then I ran the engine for 10 minutes doing configuration on the dashcam, and it's stayed at 12.3 ever since (5 hours ago).
 
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