Westco dead again.

If the same vehicle continually has dead-battery problems with replacement batteries I'd start to suspect the vehicle rather than the battery. High phantom current draw? Defective charging circuit? Cables? Starter with higher-than-expected current draw? I had the latter problem with a VW diesel which caused a long troubleshooting sequence as the battery looked good then bad then good.

AGM batteries don't like to sit for weeks without being disconnected, don't like to be charged when low from a Miata's alternator, and don't like cold weather. They're OK if you drive everyday or keep them on a battery tender (trickle charger) between drives and never let them get low.

My advice is NOT to bump start the car or get a jump from another battery, because then the Miata's charging system will cook the Westco and ruin it. Instead, try charging it at 1 or 2 amps for a couple of days, and see if that revives it. If not, as Dr. McCoy always said, "He's dead, Jim."

I gave up on Westcos after killing two of them through personal ignorance. I bought a wet-cell Super Start from O'Reilly, and even in cold weather it spins the starter faster than any AGM. It's taller than OEM, so I also needed a new tiedown rod. It vents through the OEM tubing, with some larger tubing as adapters. Many of us who don't drive our Miatas every week, or have no patience with the extra care required for AGMs, will be better served by wet batteries.

This is the first time a Westco died in less than 3 years.

I had sort of the same problem! 2 year old glass mat battery. It died due to an after market under hood courtesy light switch stuck on for several days. The battery was completely flat. Overnight charging got just enough into the battery to get a slow crank with (fortunately) a start. The battery had higher than normal internal resistance, and after additional charging still dropped lower in voltage than it should under a starting load. Replaced with another glass mat battery. I'm fortunate in that we have a local multi-generation family owned battery, starter, and alternator shop that carries batteries for Miatas.

I don't think there was any drain on the battery. There's an MK Battery about 12 miles from where I live where I get the Westco. I'll return the battery and get a replacement for full credit, I'm sure. Hopefully this afternoon.

Dark current on a stock NA Miata is no more than 20 mA, just the radio presets, clock, and stored ECU error codes. Aftermarket alarms, of course, can add any amount from very little to a dead short.

Top posting becayse you did.

D> There usually is some drain, called "dark current". Such things as

Ooops. Of course I have radio presets and clock. That can't account for a dead battery after 3 weeks of sitting. After all, I've gone away often for that long and not had a problem. I think it was a bad battery from the get-go. MK battery replaced it without a problem. They didn't even bother to test the old one.

Most domestic AGM batteries regardless of brand seem to be made by East Penn Manufacturing, including Westco. Ditto for many brands of wet batteries.

Got home today to find a message from the guy at MK battery. He said they tested the battery I returned and that it was OK and that I should have the car checked. Meanwhile, the new battery is fine and is cranking with more power than the old one (just bought Jan. 9, remember) ever did. I'm inclined to think tha old battery wasn't properly charged in the first place and that leaving it for 3 weeks (including some sub-freezing weather) killed it. Opinions?

Like I said, AGM batteries may not be the right choice for cars that aren't driven frequently, especially in cold weather, unless they're kept on a maintenance charge or disconnected while idle. I never had a problem until I started working from home.

OK. So you think it would be adequate simply to disconnect it next time I go away for 3 weeks in the winter?

That's what I'd try. You can buy a "battery saver" that will automagcally disconnect the battery if the voltage falls below the level necessary to start the engine. I don't know how well they work.

I just use a 1-amp trickle charger all winter. Works great! Battery does not freeze at 40 below, and maintains a full charge.

Stuart H.

I'm beginning to hate 12v batteries! So far in the last two months or so. Batteries on lawnmower, leaf vacuum, Miata, and yesterday, the emergency

15kw generator battery gave me trouble! (Slow charge, and then sort of OK until next time.) Not to mention that two of the computer backup units had bad batteries! It was not worth the trouble to replace the backup ups batteries, just replaced the whole thing. Replacement batteries cost almost as much as a whole new unit. The Miata battery (earlier in the thread) was still usable, but did not have much over 50% rated capacity available. (Replaced) During the Christmas holidays, my wife's 05 Impala battery failed and had to be replaced. Quit in the W-Mart parking lot. No one around at about mid-night in the W/M automotive section, and the correct replacement battery was not on the ready rack. Jump started the 05 to get it home, and got a new battery the next day. This afternoon, my old Garmin GPS complained about a "Low Memory Battery" (with new AA batteries yet!) There must be one of the coin cells inside. There must be a conspiracy going to keep the battery Mfrs afloat!