Battery Tender
 

As additional insurance against flooding and parasitic draw I installed a larger battery (600 cca) and a battery tender. Since winter hit the car sits a few weeks at a time without being driven and the battery loses charge. A few weeks ago I tried to start it with the battery a little low and flooded. Hopefully the larger battery and the battery tender will prevent this scenario from happening again. The battery tender is a great device because it automatically switches off to storage mode (no charging) when the battery is fully charged but resumes charging if battery charge drops. Unlike a "trickle charger", it will not cook the battery and can be left on indenfinitely.

Schumacher makes trickle chargers that automatically drop to a very low maintenance charge once the battery is fully charged. One model has the same connect/disconnect as your charger. In fact, I purchased one recently myself and will be using it as soon as the snow starts to fall. They also make one, also automatic, that straps to the side of the battery and is completely out of sight with only the connector for the A/C cord showing. I may eventually go for that one as well.

Good idea to go with the higher CCA battery as well. Mazda is now installing a replacement battery for the RX-8 that has 640 CCA. [There's a TSB on the new battery.] Of course, ya gotta pay for that one. :(

I once left a trickle charger on my ski boat for about 3 weeks (big mistake). When I tried to start it the battery exploded sending acid and bits of plastic everywhere. That charger said it went down to a small "maintenance charge" also. My recommendation, be sure the charger is rated as a "Storage Charger" before leaving it on for an extended period. This little charger monitors the battery voltage, charging only when the level drops, and its less than $30. Most storage chargers I found were much more. 640 CCA? The 600CCA battery I have is OE for the GTO and is almost exactly the same size as the original battery. I hope that since it was designed for a 400hp 6.0l it should be adequate for the 8 :).

So far, (two winters) I've had great results using an ICP solar cell type charger on my RX7 battery. (a Diehard that's probably five years old now) I just leave it connected all winter sitting near the garage window on the windshield of the car. I don't know the specifics, but supposedly, it won't overcharge, and the battery hasn't frozen and has easily started the car in the Spring.

Just kinda nice to not have to plug it in.

Great idea. What model number tender did you get? What battery did you put in?
I am gonna do the same thing.
Trickle chargers do have a good use. Where I live it can go as cold as -40 celsius.
A trickle charge in severe cold is not going to damage or cook the battery but will keep it warm so it doesnt lose alot of power, and the battery will charge up after start up faster as a warm battery charges quicker than a cold one.

Considering that the 8 has electronic power steering and the GTO doesn't, the 8 probably uses more power than the GTO.

By any chance do you know the weight of the stock battery and the replacement? Mazda had to be trying to keep the weight out front low when they severely undersized that battery.

bean438,

The charger I used is the "Battery Tender Jr." It comes with a permenant battery connected pigtail so it can be easily plugged in the charger. The battery is OE from the '05' GTO. It's an AC-Delco.

Beachdog,

I didn't notice any real difference in the weight of the batteries. The new one may be a little heavier but not by much. Mazda gave us a bigger alternator for the power steering requirements but went light of the OE battery. I don't think the OE Mazda battery is 600cca. It's probably closer to 400.

Right on thanks!
Now why not keep the OE battery and just use the Tender? ARe you saying that even at full charge the OE doesnt cut it for the 8??
My car sat in an attached garage for over 1 week. Outside temp around -30 celsius, indoor temp around -9 celsius.
I started it up today, and it died a couple of seconds after. Second start up no problem, but I notice in the cold the start up seems to take a real long time.

When I found my 8 it was sitting dead at the dealer. That's really not a good thing for a battery and I think it hurt mine because it seems to be dropping off quite a bit this winter . Here in Northern California (Napa Valley) it rarely drops below freezing so I can't tell you how the OE battery performs in sub-zero weather. My battery was a 50D20L - MF. If you have the same battery I doubt it is sufficient for your winters. Frequently cars destined to colder regions are equipped with batteries with more CCAs. Batteries are cheap compared to the inconvenience they can cause so I would recommend getting a good battery with a greater reserve than the OE. Keeping it charged will protect you from internal draws of the car but as I said I don't have to deal with the cold climate you do so I can't help you there.

Well for what it will cost vs the insurance it will give me, a battery tender, and new, better battery it shall be.

INteresting stuff, I checked out Tender's web site.
Dog, from what I read the chargers actually dont "shut off" when the battery is fully charged. They continue to charge but the voltage is dropped to maintanence levels.
They seem to act like trickle chargers except for the voltage fluctuation. Something to do with some kind of gassing level or something of the battery.
Anyway, what made you choose the jr. instead of the plus model?

tender jr rocks. doent shut off but does conditon. been using on bikes for years, never overcooks, and bike batteries are much less tolarant.

do agree that a larger cca bat is a better solution.

beers

I chose the Jr because it's what I used for my boat. It's the cheapest of the line and seems to do fine keeping the battery up. What's important in storage charging is amps. When the battery reaches full charge the current being applied to the battery by the Jr. is very very low.


Charger Description:

Battery Tender Junior's lightweight, compact size makes it ideal for those hard-to-fit spots. The trickled charger with a brain will assure batteries are maintained after charging and ready to go!

Fully automatic two-stage lead-acid battery charger. Perfect for all lead-acid, sealed maintenance free and gel cell batteries.

After reaching peak 14.4 VDC, charger automatically switches to 13.2 VDC float voltage.

When voltage drops below 12.6 VDC, charger resumes charging back to 14.4 VDC.

Output 12 Vdc @ 750 mA

Leave connected indefinately.

Solid state two color LED indicates stage of charger.

Spark proof

Reverse polarity protected

Safe secure, HOT CONNECT, polarized, color keyed, genderless connector system.

12 ft. output cord

5 year warranty.

Size: 3 5/16 X 2 5/16 X 1 7/8

thanks for reminding me I just hooked up my battery tender this morning...I love that thing