It's going to be 56 here today. (Miata AGM battery content)

92CelicaHalfTrac wrote: Let's bump this because i'm half-assed thinking about getting this thing on the road sometime this summer. Maybe. I'm guessing at this point that the battery is 100% toast and it's likely that i'll need a new one. 1) Good guess? 2) I'm pretty much guaranteed to spend $100-$110 for a new Miata battery, aren't i... Seems some people are using Deka EXT9s. Anyone have experience or input on doing this? $50 cheaper, seems to be just as strong if not stronger, lighter, smaller.

If you go with the EXT9 let us know how it goes. Everyone seems to recommend the 12, but the 9 seems like it should work on our little engines. I've been considering that battery for the duece. That or a teeny tiny lithium one. Indecision has kept me from doing anything.

92CelicaHalfTrac wrote: Alternatively, anyone have recommendations on batteries for a Miata?

I put an Optima yellow top in mine. Before, I used to have trouble starting the car if it sat a few weeks or a month, and I'd have to loosen the supercharger belt to get it to start. This time I let it sit all winter, and it fired right up. Not the lightest or smallest battery, but plenty of long-term sitting capacity, and plenty of throw-over muscle for the blower.

Don't know about the Hydra, but the Link I have (which is older and less sophisticated) was fine through lots of full rundowns.

Bumping.

I pulled the battery and put the Battery Tender Junior on it on.... Saturday i think.

Still solid red, charging.

And now i'm seeing quite a few people on the internet saying that the Junior doesn't work right with AGM batteries. Any thoughts on this? I'll be pretty pissed if i spent the money on this thing if it's not suitable for my needs.

The BT Jr has an output of 0.75A. You're trying to charge a car battery with it that has a capacity of a several hundred amps. Do the math .

I have the next size up (BT Plus) and that charges the AGM battery on my Kawasaki fine.

Tim i'm sending you an email.

I've got an Optima yellowtop (D51R) in my Miata, because the Hydra (at least my 2.5) is very intolerant of starting when the voltage is even a tad lower than normal. I've thought about a lightweight one, but without fixing the Hydra's starting issue, I don't dare.

The Optima basically fixed all my starting problems until my 2-year-old son left the door ajar for a couple days and it only showed 8 volts. I thought it was dead (my Sears smart charger, which claimed AGM support declared that it had a shorted cell), but a friend loaned me his "vector" charger, and after running it through a couple of 24-hour desulfation cycles it came back to life. Black & Decker owns Vector now, and I'm probably going to pick up one of those chargers for myself.

Amazon has good prices on the Optimas, but it becomes tricky to exercise the warranty on the battery if you should need to, because they want you to return it to the place you bought it from.

codrus wrote: I've got an Optima yellowtop (D51R) in my Miata, because the Hydra (at least my 2.5) is very intolerant of starting when the voltage is even a tad lower than normal. I've thought about a lightweight one, but without fixing the Hydra's starting issue, I don't dare. The Optima basically fixed all my starting problems until my 2-year-old son left the door ajar for a couple days and it only showed 8 volts. I thought it was dead (my Sears smart charger, which claimed AGM support declared that it had a shorted cell), but a friend loaned me his "vector" charger, and after running it through a couple of 24-hour desulfation cycles it came back to life. Black & Decker owns Vector now, and I'm probably going to pick up one of those chargers for myself. Amazon has good prices on the Optimas, but it becomes tricky to exercise the warranty on the battery if you should need to, because they want you to return it to the place you bought it from.

Hrmmm, well that's good food for thought, thank you!

My Hydra 2.5 seems rather intolerant of starting in general.

I'm going to let this one go until Saturday, then see how it starts the car. There's no date codes or anything on the battery so i have no idea how old it is. It is NOT the OEM, though.

On the other hand, i have a $50 coupon at Advance which means i can get a new AGM for $60.

Definitely going to price out the Optima though.

A new AGM for a Miata for $60 sounds like a good deal. The one I got at Batteries+ here (only place around that had one in stock) was about $100...

BoxheadTim wrote: A new AGM for a Miata for $60 sounds like a good deal. The one I got at Batteries+ here (only place around that had one in stock) was about $100...

Yeah it's $110, but i spent $100 with them in March to get a $50 coupon off my next purchase over $100.

So that works out. I was going to use it on some Rancho 9000XL shocks for the Cherokee, but i have other codes i can use for $30 off each of those.