Hello!

As the title of this thread says, I have a question about possible alternator upgrade and/or capacitor install.

My friend has an RX-8 that he got around 2003/2004. He bought it because of the ease of access to the vehicle. He's in a wheelchair and didn't want to mess with the van or getting in and out of regular car door style vehicles.

How he gets in and out of the car, he slides the motorized seat forward, takes the wheels off his chair, then puts them in the back seat along with the chair frame, then slides the seat back. He's been doing this since he got it.

The issue that brings me around to my question is when he doesn't have to go anywhere for a while, ie: vacation, the car sits parked for a week or two. The battery then is unable to start the car due to being drained. This happened just a couple days ago after he had two weeks off during the holiday break. The battery right now is showing just over a year and a half old. It charged back up find and hasn't given him anymore problems since Monday.

What I am wondering is that since he pretty much only drives the car to and from work, which is a 5 mile run one way (car only has a little over 30000 miles on it!), is the battery not getting enough of a charge from the alternator? I would think it's doing ok as it is starting the car in normal driving conditions.

What I have researched is that a stock alternator is around 100 amps.

Would a larger alternator help to keep the battery charged?

Another option I thought of was perhaps installing a capacitor to help with the power issue. Only places I have seen capacitor use is for audio systems.

I've also thought of perhaps a second battery installed in the trunk that just powers the seat motor.

I did install a trickle maintenance charger connection to the battery, so when he does park it for while, he can plug the charger in when he knows he won't be going anywhere for a while.

Any thoughts and suggestions on this would be greatly appreciated.
Thanks!

 

The RX-8 has a high amp alternator already but the RX-8 draws some milliamps when sitting so depending on the exact battery he has, more than two weeks of sitting is pushing it. I would suggest a better battery with longer reserve time or a trickle charger.

I use the NOCO G750 float charger but they offer many different models. My buddy has the G7200 which is great for recovery and boosting.

https://no.co/products/charging/multipurpose

And they make accessories to make hhoking it up.

I have this which will be mounted in the empty slot next to the DCS switch when I get around to it. Right now I have a pigtail plug installed right on the battery which is also convenient. My battery is relocated to the trunk as well.

 

Trickle charger would be a good option, they can be had for cheap. I would also check the so called vampire current of the electrical system, there might be a short that is draining power while the system sits.

Is it similar to the original battery, or did he get a good replacement? Some rx8s came with undersize batteries, and there was a technical service bulletin where they replaced the, with larger units. How many CCA in the current one? Does he have the stock battery box? Mazda says it delivers fresh air to the battery to reduce temp. Batteries and heat don't mix.

 

I have a pigtail for a float trickle charger installed on the battery right now. I will probably have to wire it so that he can get easy access to it without having to try and lift the hood.

9krpmrx8, You say you are mounting that charger inside the passenger area? That really might be the way to go and would be really easy for him to plug it in.

Battery size I don't know off hand. Next time I am at his house, I'll take a look. I do know that he takes the car to the dealership to get it serviced, so they may have taken care of that recall.

His car is all stock. He hasn't done any modifications to it.

 

Yes the plug will mount next to the steering wheel where the DCS (traction control) button is, there is a blank there (pictured above). Right now I just plug it into the pigtail that is installed on the battery and close the trunk.

A phantom draw is possible but really two weeks is about the limit from what I have seen from a stock spec battery and I have stored a few RX-8's at my place for years at a time for friends on deployment, etc.

But see what battery he had and what the reserve capacity is, because that will tell you a lot.

 

Sorry for not being much of help!
I currently have yellow top Optima battery, its almost 2 years old now.

I let my car sit in the garage and start it every 3 weeks. She fires right up.
I also have my 1000 watts amp and sub connected and haven't had any issues as of yet.

Maybe, there is a short somewhere or the battery has deteriorated over the years.

 

After looking at those, I might have to buy a couple for myself :D

The interior plugin would really work well for him.

 

That is due to the reserve capacity of the Yellow Top (when they work as designed that is). I went thru two Optimas in two years, worst battery I ever owned and then I started seeing issues with them popping up all over.

This happened to a Jeep buddy. He heard a loud "pop" and found this.

 

Myself and two other locals use different model Odyssey batteries and they have been great. This one would be the factory replacement.

Odyssey PC1400 battery


Compare the specs to something common like this Group 35 Duralast which would be what would be recommended if you went to buy a battery.

http://www.autozone.com/1/products/1...ld-35-dlg.html