Hybrid & Aux Battery Problems

Hello!

I have a 2008 Prius w/ 128k+ miles & recently had my car throw a "Hybrid System Malfunction" light and shut off while on the highway.

History:
In January, I was having problems starting up the car, took it a dealership and they said the aux battery was low and quoted me at $400 to replace w/ an OEM.

I did some research and it was suggested to me to get the optimum battery from elearnaid.
Toyota Prius 12 Volt Auxiliary Battery with install kit for 2004 + including Plug in
Ran me $200 and my private mechanic put it in for $50. He told me when he went to replace the battery, he checked the old one and it was fine. I told him to put in the optimum anyway since the internet told me it was better and I'd already paid for it.

Problem solved.

Now:
I was driving my car, engine felt off (didn't feel like I had much power over 55mph), MPG is down to like 20 (from 45-50). "Hybrid System Malfunction" light comes on, car smells funny. And suddenly the engine just turns off while on the freeway.
According to mechanic/dealership codes being thrown are about low voltage in hybrid battery and aux and low power to transmission and possibly other things.

Mechanic tells me to take it to a dealership b/c of the hybrid system lights.


Dealership tells me both the aux battery and the hybrid battery are very low (aux is at 9v after 4 months).
First step, they want to replace the aux and see if that fixes everything.



So my question:
Should I try to get another Optimum battery since this one seems to be defective/not holding a charge? (I assume eLearnAid has some sort of warranty.)
Is it possible the Optimum Battery is not the problem and the Hybrid battery may have an issue that's drained it?
Should I just stick with the dealership through this process since it's getting complicated?

Do aux battery problems really have the ability to mess with my hybrid battery? I thought the aux battery just helped turn the car on (which I've had no problems with).

 

So it appears I'm just a moron.

I drive my car once a week for about 2-3 hours. Apparently this is not enough to maintain a charge in the aux battery and was most likely the cause of the first problem and the cause of this problem.

Does that sound reasonable?

Looks like I need to replace the battery and sell the car.

 

When I called eLearnAid, he told me driving that little qualified as abuse/neglect and thus it wasn't a warranty issue. Is it possible the battery was a dud?

I misunderstood the dealership originally (there were 5-6 codes being thrown), nothing to do with the hybrid system, they said that battery was fine.
Still haven't explained why I saw that original light "Hybrid System Malfunction"

 

It was a Yellow Optima Optima DS46B24R Optima battery direct fit replacement for Prius 2004 + , Prius V & Plug-in Prius with Instructions

How do I pursue getting the warranty replacement?
Do I just press the issue with eLearnAid or contact the manufacturer directly?
I don't see eLearnAid's motivation to lie to me, presumably the manufacturer is responsible for warranty issues.

And given I had no problems for several months, is it really likely to be a dud?

 

That is what I was concerned about. As I understand it the Aux battery just starts the car, it doesn't explain to me why the engine was struggling above 50 or why the engine just cut out on the free way.

As for eLearnAid, it's a tiny company (every time I call it's the same guy), my story is known. If it does qualify as neglect/abuse, I don't think he's gonna help me out.
But it sounds like I should maybe just have the dealership replace the battery with an OEM one in case there is a deeper problem that needs to be tackled.

 

Thanks for the recommendation, I greatly appreciate it.

 

I appreciate the sentiment and will look into it.

So are you of the opinion that driving a prius 2-3 hours a week is enough to keep the battery charged? Because I've talked to a couple different people and they all seem to think that this is what caused the dead battery, and that it really is my fault.

And again, if it was a bad battery, would it still last 4 months before having a problem?

 

For future knowledge:
What is the downward limit on driving enough to keep the battery healthy?
I didn't know this was something to keep an eye out on.

Would driving it for two hours once every 2 weeks be okay? 3 weeks? Once a month? [Renting a car at this point seems cheaper of course.]

My buddy says he's able to start his car after a month or two of not driving without an issue, but acknowledges its an old jeep without any fancy gadgets.