[rlw999]

I'm convinced my 12V battery is going bad in my 2020 Accord Hybrid, I first noticed it when I was setting up a new dashcam and it has a voltage monitor and after less than 10 minutes of running the car in accessory mode to set up the camera, the voltage was down to 11.6V. After taking the car out for a long trip and just parking it in the garage for a week, the voltage had dropped to 11.9V. And one time I was waiting in a parking lot for 20 or 30 minutes with the radio on, when I tried to start the car, I got presented warnings that pretty much every system was failing. I turned the car off, waited 10 minutes, then was able to turn it back on without incident, but I suspect that those warnings were from a low battery.

I could wait until it fails and then try to get Honda to replace it under warranty, but I'd rather be proactive and put in something better than the Honda OEM battery. I've been very happy with an Optima AGM battery in my other car, but when I looked up the Accord Hybrid with their battery finder tool, they said there's no match.

Has anyone fitted an Optima or other AGM battery on their Accord?

 

[Hunter Mike]

Fully charge your battery before jumping to conclusions. You said you’re convinced but what tests have been performed?

 

[rlw999]

Fully charge your battery before jumping to conclusions. You said you’re convinced but what tests have been performed?

The time it dropped to 11.9V in a week, I had just returned from a weekend trip with about 16 hours of total driving, including 8 hours driving on the way home. If that's not enough to fully charge it, then what is? I'm not going to plug into a battery tender every time I park the car. My other car with the 5 year old Optima battery stays over 12V after weeks of sitting in the garage.

While I don't drive the Accord much, when I do drive it it tends to be on longer trips (a couple hours or more), then it'll sit in garage for a week or two before taking it out again. I bought the car for commuting, but I no longer commute to work.

But assume that regardless of the state of the battery, I just want to put in a better battery because I think Honda OEM batteries are crap. I don't mind spending $200 on a battery if it makes it less likely that I'll be stranded after I leave the car parked at a remote trailhead for a week while I go on a hike/camping trip.

 

[Hunter Mike]

Feeling vs. facts, oh bother…

An AGM would probably be better, for you, since they can survive a full discharge vs. a SLA battery. If you allowed the battery to discharge that it wouldn’t start the systems its probably dead. Each time you drain a SLA battery you cut its reserve capacity in half. Interstate shows an AGM in their application guide.

Driving a modern car to charge a battery will rarely allow it to reach 100% SOC. CAFE is the only thing that matters.

 

[BrianMcCartan]

Common knowledge these batteries are failing in the 2018's,2019's,2020's allready. Combination of Honda batteries always being garbage in all their cars for decades and this hybrid model having vampire drain. We will be proactive with our 2018 before this coming winter and our 2019 before next winter. These things brick when the battery dies. Most get no warning it's coming. There are threads and posts all over the net.

Fully charge your battery before jumping to conclusions. You said you’re convinced but what tests have been performed?

The HV battery charges the 12V anytime the car is turned to ON. The engine charges the HV battery.

I'm convinced my 12V battery is going bad in my 2020 Accord Hybrid, I first noticed it when I was setting up a new dashcam and it has a voltage monitor and after less than 10 minutes of running the car in accessory mode to set up the camera, the voltage was down to 11.6V. After taking the car out for a long trip and just parking it in the garage for a week, the voltage had dropped to 11.9V. And one time I was waiting in a parking lot for 20 or 30 minutes with the radio on, when I tried to start the car, I got presented warnings that pretty much every system was failing. I turned the car off, waited 10 minutes, then was able to turn it back on without incident, but I suspect that those warnings were from a low battery.

I could wait until it fails and then try to get Honda to replace it under warranty, but I'd rather be proactive and put in something better than the Honda OEM battery. I've been very happy with an Optima AGM battery in my other car, but when I looked up the Accord Hybrid with their battery finder tool, they said there's no match.

Has anyone fitted an Optima or other AGM battery on their Accord?

A question to ponder.....Does the HV battery charge the 12V battery when in accessory mode or does it need to be in ON? But yeah, change that thing now.

 

[Hunter Mike]

Ok, I just ran some quick tests with a voltmeter/inductive ammeter. My overnight resting voltage was 12.71V, indicating a full charge. When powered up, the voltage immediately jumped to 14.5V and was steady, ICE on or off. Thanks, Brian. You are correct.

After one hour to let all systems shut down, I used the ammeter to measure draw and it was hovering around 600mA. A more accurate measurement would be with an inline ammeter but it's close. >0.5A parasitic draw is big, but normal for ~'12 and up cars. OP, if your car sits for 2 weeks without driving I am not surprised the battery was discharged. 11.9V after sitting a week is less than 40% charge for a FLA battery. Dropping below ~12.4V and it starts sulfating.

A modern car has more systems powered up when not in use so anyone who doesn't drive often needs to keep the car on a smart charger. Make sure it's hooked up properly to involve the meter on the negative terminal, not just on the battery terminals. RTFM! The other option, as I mentioned, is to get an AGM battery because they handle deep-cycling better. FLA batteries like to be fully charged all the time or they suffer damage during discharge.

 

[rlw999]

A modern car has more systems powered up when not in use so anyone who doesn't drive often needs to keep the car on a smart charger. Make sure it's hooked up properly to involve the meter on the negative terminal, not just on the battery terminals. RTFM! The other option, as I mentioned, is to get an AGM battery because they handle deep-cycling better. FLA batteries like to be fully charged all the time or they suffer damage during discharge.

My other car (it's a 2018, so not much older than the Accord) doesn't drop voltage that much while parked.

I can't plug in to a charger regularly even if I wanted to since I can't always park next to a power outlet. If I could, then I would have gotten a full electric car instead of a Hybrid.

The other option, as I mentioned, is to get an AGM battery because they handle deep-cycling better

Well yeah, that's pretty much why I started this thread, to see if anyone has replaced their 12V battery with an AGM battery. I checked Interstate as you mentioned them above, but the battery they recommend for the Accord Hybrid is the MT-51, which is not AGM. For the standard Accord, they have an AGM recommendation, but not for the Hybrid. It's the same with Optima, which makes me wonder if the DC-DC charger on the Hybrid is not compatible with AGM batteries.

 

[jackpine]

AGM batteries DO need a different charging algorithm than standard lead-acid. I will not attempt to install an AGM battery in my car, because they cost about twice what a lead-acid battery does and I'm not seeing many testimonials that say they last twice as long. The ads for them claim that kind of longevity but I don't believe them, and they ARE "maintenance-free", but that is a minor concern for me.

- Jack

 

[Hunter Mike]

...which makes me wonder if the DC-DC charger on the Hybrid is not compatible with AGM batteries.

IF, it puts out 14.5V consistently it would probably be fine. I'll do a drive sometime with my scan tool hooked up to see the charging profile, still a new car to me.

If.

AGM batteries like a higher charging voltage to be happy. My NOCO charger puts out 14.4V to a SLA battery but in the AGM setting it's 14.7V. If you don't charge it fully once in a while it won't be happy.

@jackpine, As with most things promised these days it's probably too good to be true. "Artificial sweeteners are good for you, Anna Nicole Smith married for love, and there are WMD's in Iraq!"