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Login to post Forums » Grassroots Motorsports » It's going to be 56 here today. (Miata AGM battery content)

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Jan. 6, 2012 9:05 a.m. 92CelicaHalfTrac SuperDork

I haven't driven the Miata since Thanksgiving. Figured i'd drive it today since it's going to be ridiculously nice out today.

HAH.

So after cranking the car for almost 2 minutes (it never starts quickly because... well.... because.) it finally starts just as the battery starts to fail.

Runs for 10 seconds.

Then stalls. Because the start up and idle control is not good.

Not enough juice to start it again.

So my questions:

1) Any special procedure to jumping an AGM battery? Or am i being paranoid and there's no difference?

2) If i replace the battery with something stronger in an effort to combat the drain from the ridiculously long cranking times this thing always has, is the "tune" on the Hydra unit safe? As in... saved to a ROM that will remain even if it loses all power for an hour or two?
Jan. 6, 2012 9:08 a.m. aussiesmg SuperDork

3) Fix the cause of the cranking issue.

Just saying....
Jan. 6, 2012 9:10 a.m. iceracer SuperDork

Jump starting is as usual. Just be sure you connect properly. Fixing the slow start and stalling problem will eliminate most of the battery problems.
Jan. 6, 2012 9:11 a.m. 92CelicaHalfTrac SuperDork

aussiesmg wrote:

3) Fix the cause of the cranking issue.

Just saying....

That's getting into another discussion involving Hydra-equipped cars and the utter lack of anyone local with the willingness/knowledge to tune one.

Appointment made for March, but i'm sure it'll get bumped a time or 7 again.
Jan. 6, 2012 9:15 a.m. 92CelicaHalfTrac SuperDork

iceracer wrote:

Jump starting is as usual. Just be sure you connect properly. Fixing the slow start and stalling problem will eliminate most of the battery problems.

Cool, thanks. :)

Alternatively, anyone have recommendations on batteries for a Miata?
Jan. 6, 2012 9:15 a.m. jrw1621 SuperDork

As for taking the car out on the road...have the local road already had salt applied to them this year?
If the answer is yes, then i would not take out the car, no matter how strong the temptation.

When you see, "never driven in snow" what I really want to know is, "never been subjected to road salt." For my car, even in the spring when the weather changes, I resist taking out mine until it has rained a couple of times heavily to wash all that damn salt away from the road.

If taking you car out today will get that damn white residue all over your car then do not do it.
I know many think, well I will just wash it before I put it back away. The problem here is the underbody. Everything gets that damn white residue and then things go to hell.
Jan. 6, 2012 9:19 a.m. 92CelicaHalfTrac SuperDork

jrw1621 wrote:

As for taking the car out on the road...have the local road already had salt applied to them this year?
If the answer is yes, then i would not take out the car, no matter how strong the temptation.

When you see, "never driven in snow" what I really want to know is, "never been subjected to road salt." For my car, even in the spring when the weather changes, I resist taking out mine until it has rained a couple of times heavily to wash all that damn salt away from the road.

If taking you car out today will get that damn white residue all over your car then do not do it.
I know many think, well I will just wash it before I put it back away. The problem here is the underbody. Everything gets that damn white residue and then things go to hell.

Point taken.

They salted the roads a week or so ago, use that liquid stuff though. Doesn't seem to get all over the cars i'm actually driving, luckily.
Jan. 6, 2012 9:43 a.m. aussiesmg SuperDork

That liquid brine is much worse on the car than the granulated stuff
Jan. 6, 2012 9:51 a.m. BoxheadTim SuperDork

92CelicaHalfTrac wrote:

Alternatively, anyone have recommendations on batteries for a Miata?

I had to buy one for my NA and got one from Batteries Plus. Seems to work OK, but like all Miata batteries it's not cheap.

The PO had battery drainage problems on my Miata as well, most likely thanks to the stupid alarm on the car so he wedged in a regular car battery that vented into the trunk. Oops.
Jan. 6, 2012 9:51 a.m. Keith SuperDork

Part of the problem is the fact that the car sat for a couple of months. That pulls down the battery. If it's going to sit that long, install a cutoff or spend $10 on a float charger.

Charging an AGM battery is different than a normal battery, but jumping is the same. The Hydra's tune will be fine.
Jan. 6, 2012 9:53 a.m. 92CelicaHalfTrac SuperDork

Keith wrote:

Part of the problem is the fact that the car sat for a couple of months. That pulls down the battery. If it's going to sit that long, install a cutoff or spend $10 on a float charger.

Charging an AGM battery is different than a normal battery, but jumping is the same. The Hydra's tune will be fine.

Thanks Keith.

That link says "not for use on AGM batteries," though. Do i ignore that warning?

Remove battery from car before putting on a float charger?
Jan. 6, 2012 10:00 a.m. BoxheadTim SuperDork

I have that particular charger. I ended up buying a battery tender - if you want the HF one you can have it for the cost of the postage.

I normally leave the battery hooked up in the car or bike and just hook up the float charger. Works OK so far.
Jan. 6, 2012 10:14 a.m. ProDarwin SuperDork

I used to use a solar float charger. Too bad Japanese cars turn off the cig. lighter circuit when the ignition is off :(
Jan. 6, 2012 10:14 a.m. 92CelicaHalfTrac SuperDork

BoxheadTim wrote:

I have that particular charger. I ended up buying a battery tender - if you want the HF one you can have it for the cost of the postage.

I normally leave the battery hooked up in the car or bike and just hook up the float charger. Works OK so far.

Is it safe to use on an AGM?

Leave trunk closed is ok?
Jan. 6, 2012 10:21 a.m. mistanfo SuperDork

ProDarwin wrote:

I used to use a solar float charger. Too bad MOST Japanese cars turn off the cig. lighter circuit when the ignition is off :(

Fixed that for you. Had a few AllTrac Camrys that stayed hot.
Jan. 6, 2012 10:22 a.m. Chas_H New Reader

Disconnect the battery instead of using a float charger. I have a quick disconnect I use when the car is going to sit more than a few days. The AGM battery loses little voltage when sitting unconnected.
Jan. 6, 2012 10:22 a.m. BoxheadTim SuperDork

I don't have anything here with AGM batteries, but looking at the Battery Tender website you can interpret the words in their users guide that it should be OK to that one with AGM batteries. No idea about the HF one, though.

Leaving the trunk closed might be an issue with getting the wires in but if your battery is hooked up to the vent pipes I don't see any reason why it has to remain open.
Jan. 6, 2012 10:23 a.m. 92CelicaHalfTrac SuperDork

Chas_H wrote:

Disconnect the battery instead of using a float charger. I have a quick disconnect I use when the car is going to sit more than a few days. The AGM battery loses little voltage when sitting unconnected.

Now you're giving me bad ideas of putting a cut-off switch in the license plate panel.

Well, i've gotta charge it again first i guess. I think i have a small cheapo charger up in my garage somewhere
Jan. 6, 2012 10:35 a.m. Keith SuperDork

I've got a "schumacher" one that I've used on AGM batteries for years. I've seen it with different labels elsewhere, I just assumed the HF one was the same. Never looked too closely. AGM batteries do act a bit differently under charge, so it's possible that the electronics simply won't understand what the battery's doing. There certainly are float chargers that are suitable for AGMs. Look on the Sprockets side of the fence.

If you're going to charge that AGM, they prefer a slow rate of charge over a long time. 2A if you can.

Disconnecting the battery will deep-six your radio settings (which is part of what killed your battery in the first place), but the Hydra won't care (unlike a GM PCM). So that's the best choice if possible. I have battery cutoffs on most of my vehicles.
Jan. 6, 2012 10:52 a.m. Wonkothesane Reader

BoxheadTim wrote:

I don't have anything here with AGM batteries, but looking at the Battery Tender website you can interpret the words in their users guide that it should be OK to that one with AGM batteries. No idea about the HF one, though.

I have a BT Jr that I just got, and it specifically says in the manual and packaging that it's safe for use charging and floating an AGM battery. It does spell out not to use it with a "dry cell" battery, but I really wasn't planning on recharging any AAs with it, so that's not a big concern.

The HF one specifically says NOT for use on an AGM. Must be something to do with regulating the voltage for charging, like Keith said, the electronics probably just aren't set up for it. Seems to work fine on the water filled ones, though.

Incorrect charging is supposed to kill an AGM pretty quick, I haven't done it though, so you're mileage may vary..
Jan. 6, 2012 10:54 a.m. 92CelicaHalfTrac SuperDork

Keith wrote:

I've got a "schumacher" one that I've used on AGM batteries for years. I've seen it with different labels elsewhere, I just assumed the HF one was the same. Never looked too closely. AGM batteries do act a bit differently under charge, so it's possible that the electronics simply won't understand what the battery's doing. There certainly are float chargers that are suitable for AGMs. Look on the Sprockets side of the fence.

If you're going to charge that AGM, they prefer a slow rate of charge over a long time. 2A if you can.

Disconnecting the battery will deep-six your radio settings (which is part of what killed your battery in the first place), but the Hydra won't care (unlike a GM PCM). So that's the best choice if possible. I have battery cutoffs on most of my vehicles.

Cool, thank you Keith.

The radio settings would be a bit annoying (fairly high-end complicated setup), but one of those things that would probably only happen 1-2x a year.
April 13, 2012 9:44 a.m. 92CelicaHalfTrac MegaDork

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.
April 13, 2012 9:55 a.m. Keith MegaDork

Try a long slow charge. AGM batteries like foreplay, not just wham bam here's your charge ma'am It may come back.

There's an Autozone one that people have used. Me, I have an Optima yellowtop in both of mine. I used to have an Odyssey PC680 in the Targa car, that worked well but it doesn't have the reserve capacity of an Optima.
April 13, 2012 10:00 a.m. EvanB UltraDork

Maybe you should go megasquirt, my Miata starts right up
April 13, 2012 10:03 a.m. 92CelicaHalfTrac MegaDork

Thanks Keith, just ordered the Battery Tender JR and we'll see how that goes.

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