Well yes, my hybrid battery is basically failed, but why would that also affect the 12v? I know you can run without the hybrid battery technically. My reason for saying AGM is because you mentioned that the voltage that honda keeps the battery at is basically under charged and hence wear out lead acid faster if I understand what you said earlier correctly. So would an agm be better and last longer, and maybe avoid what I and the poster are facing?

 

The hybrid battery can deteriorate to the point that reliable 12V charging is no longer possible. The HV system powers the DC-DC converter. The battery is a big electron sink from which the DC-DC draws when the IMA motor is producing too little or too much voltage.

The hybrid battery can deteriorate to the point the battery is isolated from the car. When that occurs, you flip off the master switch and try to run it between about 1500 and 3500 rpm where the IMA motor output and the DC-DC converter get along. You will not get 12V charging outside that range.

I wouldn't waste the $ on an AGM. The 51R has 40% more capacity than the 151R... might last 40% longer for less $. AGM might last longer, but it will definitely cost more.

 

So did replacing the 12V battery fix your issue?

 

You either have a failed 12V, or your IMA battery has deteriorated to the point that it won't reliably charge the 12V or both. Get your 12V load tested.

 

How exactly are you getting the 51r in there? That definitely seems like the way to go, but it is significantly wider and removing the brackets alone does not seem to be enough, and I can't find any pictures. According to the low test, the battery only does 280 cca

 

It fits very easily, but there is less clearance at the ends. You have to remove all the plastic shrouds and base from the 151R. Once that's done, you have no issue installing the 51R in its place and clamping it down.

 

About to take it to an automotive store and see if they can do it.

 

If they can't, they're idiots, or you have some unique kind of HCH2. I did it on both of mine. It was trivial.

You may run into them being unwilling to do it since it's not the correct battery for the car, AND this may not fix your problem because your charging may be disabled due to the failed HV battery.

 

Well the battery is at about the time it needs to be replaced anyway. And since it's significantly larger, it should last longer even at a degradation. I only got 280CCA in the current one, and thats 40 degree weather. Thanks for the information.

Edit: Well I could add water, but I doubt that would much fix my CA being at 280. In 0c weather, it would start half as slow. A 51r regardless should even last longer even degraded, it would still be a 151r new. I also hope it fixes my weak power steering and excess recalibrations which only go away after a few hundred miles drive.

 

Yeah. 5 years is a good run. Just want to keep perspective about it being fixed or not.