Bought a new Group 26 (P/N 26R72J) battery from Kragen in August '09. Seems to have "gone bad" just recently. I had changed the thermoswitch to the FC type (97°C) 9 months ago. The change has resulted in much more frequent 10 minute fan runs after driving. Here's what battery history looks like on our '94 (bought new 9/1994):

OEM battery lasted 48 months/38,572 miles.
1st replacement lasted 88 months/28,653 miles. (Mazda 36/60 dealer battery)
2nd replacement (current battery) has 19 months/4100 miles on it.
FC thermoswitch installed 9 months/1850 miles ago.

With engine off, battery measured 12.1 volts. But it failed to start the engine.

The current battery has failed to start the engine twice now; once about 2 months ago, and just yesterday. I used a battery charger on it at a 2 amp charge rate the first time, which seemed to work out OK. But now, although charging seems to work once again, the green "Charge Complete" indicator on the charger doesn't light after 24 hours at 2 amps.

The battery voltage after charging drops to about 11 volts when starter is cranking, the engine's alternator puts 14.3 volts across the battery when engine is idling, and voltage on the battery after about 2 hours off the charger is 12.9 volts with engine off. All that looks OK, IMHO.

I checked dark current, which measures about 13 mA.

Since the RX-7 alternator is rated at 100 amps, and it seems to be charging at a good voltage, one would think it could easily keep the battery charged; we do very little night driving, have a stock alarm and stock audio system, etc. Only the fan run-time has gone up during the last 9 months.

The current battery is rated at 670 CCA (at 32°F). Don't know the storage capacity in amp-hours. But it is the same case size as the two previous ones.

Question: Do I have a battery gone bad randomly, or is this the natural result of excessive battery usage caused by the much more frequent fan operation due to the FC thermoswitch?

 

I dont think the fc thermo switch is completely to blame. The extended run time is not to long to severely discharge a battery that is in good condition.

My opinion with batterys is, you get what you pay for. The first battery's you had were purchased from the Mazda dealer and were OEM the third one is a cheap alternative and it did not last. What I would do is pony up the extra dollars and buy another OEM one or buy a quality name brand battery from a reputable dealer.

Also, I see the amount of miles driven the the last 19 months is alot less that the previous years. Do you connect a battery tender when the car is parked? That might help to alleviate your problem as well.


John

 

Not sure if this is helpful, but 2 weeks ago I started my car after having it sit over the winter for about 4 months. Before starting it up I checked the voltage on my battery and it was sitting close to 10.1 V. So I'm not sure if you're car didn't start because of the voltage. Unfortunately I didn't measure the amps. The car started right up with no hesitation, and afterwards I put it on the charger as a "just incase". My battery is an optima red top.

 

Sounds like the battery is fine but there is a poor connection somewhere. If you are getting 12 volts at the battery it is fine.

 

I agree that better quality generally costs more, but I paid $79.95 at the Mazda dealer in 2002 and $88.94 at Kragen in 2009, so I think the battery quality is probably not that much different between the two. Hopefully the battery is not "bad," just overused due to short trips and the fan running so much. I will make it a practice to do a slow charge every couple of weeks when the car isn't being driven.

FWIW, the OEM battery saw a driving rate of 807 miles/month, the 2nd was driven 326 miles/month, and the current one 216 miles/month. The one that lasted the longest was the 2nd one. (The big drop from 1st to 2nd was caused by wife retiring from her job.)

Could be... but the engine started right up after charging the battery... maybe a "marginal" connection?

 

^ As far as prices of batterys they have gone up considerabily due to the increased cost of the raw materials. Ie. Lead.

FWIW, Where I work we have many pieces of equipment and vehicles, close to 40 batteries in total. When we use the "cheap" brands we almost always end up replacing them in 1 or 2 years. If we use a known name brand you can double that. I do want to add that i do not have any experience using that brand battery though so maybe the quality is different.


Isn't there a "kit" to help keep voltage drop to the starter at a minimum?




John

 

"Could be... but the engine started right up after charging the battery... maybe a "marginal" connection?"

this is exactly it. This is a very common problem I have seen many many times. There is nothing wrong with the battery. You need to throughly sand/clean the main battery connections, starter connections, grounds, etc... This will solve your problem.

 

Eh, it doesnt look to be a quality battery.
It would be more affected by this i think.

 

Not to be nit picky, but I've used optima batteries in every car I've owned for the past 12 years now. I've never had one die on me yet (knock on wood), and they are maybe $30 (red top) more than a typical OEM replacement.
You should also double check your connections as mentioned above, and use anti-corrison coating on them as well. Make sure when you tighten your connections they do not wiggle at all. When I bought my FD I was able to lift the ground connector of the terminal so that was one of my "immediate fixes". I also recheck my connections every other oil change. If you haven't already you might look into adding some grounds to your vehicle.

good luck!

 

The brand of battery doesnt make a difference in this case. He is obviously having other problems, which like I said earlier is a connectivity issue. The only differences you will notice really in battery quality are mostly weight and size, if they vent harmful gases, and their output. Just because a battery isnt an optima or oddessy or some other name brand doesnt mean its bad at starting a car.

 

You do not know what your talking about. Please stop spreading misinformation. Im sure you think if a sweet big yellow top was sitting there it would start right up, right? Haha.

 

A cheap battery will not handle deep discharge/long periods of non-use as well as a quality one will.... OP has hardly driven the car over the past few years...

Sub-par materials, might be the reason they are cheap, eh?
voltage is not the only factor...

And did i ever say anything about optima being better?

This was my guess based on what the OP described, and due to lots of electronics background....
no need to go off on me for no apparent reason...

 

Can only speak from my experience but never had issues after switching to the Miata, and later FC thermoswitch with the fans. IIRC I bought the current battery about 6 yrs (72 months) ago and it's still in there.

 

215 miles/month = 58 miles/week. Sufficient to keep the battery charged, I would think.

 

I have the Pettit switch and I have had the same issue. I replaced my "Werker" brand battery just a few months ago with a good "Silver" one from Advance Auto Parts. Has the "PowerFrame" logo on it. The fans running after shut down without driving some real miles in between will result in a slow start after the 1st stop, and no start after the 2nd stop. I was considering the IRP alternator or maybe a better battery? I just installed a Koyo N-flow so the fans don't come on as much but they still run after shut down if the temps are high enough.

 

The stock FD alternator is rated at 100 amps. On my car, idling in daytime provides 14+ volts to the battery, plenty IMHO. I don't think a bigger alternator would charge faster, and faster might not be good anyway. Seems like your "driving some real miles in between" is one of the only two ways to keep the battery charged; the other is using a charger on it between uses, in lieu of long drives. A battery with more storage capacity than a Group 26 (like a Group 24) would take longer to discharge, but also take longer to fully charge. And if more energy is being withdrawn than input to it, the battery will still eventually require external charging or a long drive.

 

I have an FC thermoswitch. Also have the best Craftsman battery I could buy. It's working fine. Although I keep it on a trickle charge if I don't drive the car for a while.

 

I think the trickle charger is the ticket.

 

Pulled Mazda's Cooling Fan Mod out of our '94. Recently checking battery voltage after undoing the mod, I constantly get a full 12.6 volts, or fully-charged indication. (Was anywhere from 12.4 down to 12.1 volts with the fan mod installed.)

 

How many times do I need to tell you it is the electrical connections? Quit wasting your time/money and just clean/resurface all connections in the starting circuit. Like i said before, 12v at battery means its fine. So, if it is always seeing 12v your problem is most likely a corroded connection.

All other advice on this thread is completely off base, or a bandaid fix.

 

I can't speak for the others but my issue is certainly not the electrical connections.

My battery is new, my connections are mint and clean as is the entire car.

I would like to know more about removing the fan mod. What are the positives of having the fan mod? I'm sure Mazda made the mod for a reason.

 

How do you know the connections arent bad? They look clean? Many times they look fine when in fact they are not. Just saying, not that it is actually a problem on your car. Cant comment on your setup since I have no info and this isnt your thread. If your battery does not maintain voltage after shutdown, you have a draw somewhere on the car. Could be anything from a security system light or a boost controller wired up incorrectly or anything inbetween.

At any rate, all of that does not pertain to the OP's problem, since he is consistantly maintaining 12v at the battery.

Oh and if you want more info on the fan mod, just search this section. TONS of info on it over the years. Just gotta find the good threads. Try the faq to start.

 

No argument that bad connections can cause a no-start problem. But in my case the problem was that the consistently short runs coupled with regular 10-minute after-runs of the fans were gradually discharging the battery. I think that is proven by the fact we have had no problems starting the car since I removed the fan mod. And by voltage measurements. 12.0 volts on an unloaded battery is not necessarily an indication of full energy storage. On both my (previous 1990) Miata and on our RX-7, a full charge gives 12.6 volts. We were having trouble at 12.1 volts (unloaded). Could have been connections, but I am much more comfortable with the fan mod out of there. The current configuration gives an engine-running medium radiator fan speed (with A/C off) if coolant temp is above 100-104°C, and high-speed if A/C is on at > 100-104°C. And no fan running after ignition is turned off. I agree with Dale Clark that this is a better configuration than stock FD fan switch with fan mod in.

 

Yes, Mazda had a good reason. The combination of a 225°F fan thermoswitch and the resulting high under-hood temperature was bad news for lots of things... risk of deteriorating rubber maybe causing fire, fuel boiling, short vacuum hose and coolant hose life, etc. If you have the stock FD thermoswitch, removing the fan mod is a bad idea. The unmodified stock fan control system and the modified fan control system truth tables are shown in post #22 of Dale Clark's "All about the Fan Control" thread.

With the OEM stock system before the Mazda fan control mod was added, the radiator fans ran only with the ignition ON, and fan speed varied as shown in the upper table. With the fan mod installed, the fans ran as shown in the lower table, and would run after engine shutdown (ignition OFF) for 10 minutes, if the fan had been running with engine running.

With the FC thermoswitch installed and fan mod installed, the only difference from the lower truth table is that in the coolant range (100 - 104°C) when fans' speed would normally have been low, they run at medium speed. This is because the 97°C fan thermoswitch is now closed, grounding the second fan motor coil return and activating the higher fan speed. But the fans will still run for 10 minutes after each engine shutdown where they had been running with ignition ON.

With the FC thermoswitch installed and fan mod removed, i.e. put back to OEM stock configuration, the only change from the last paragraph is that the fans will no longer run after engine shutdown. Since the higher fan speeds keep the engine cooler while running, running them after shutdown is no longer as advantageous as before; the coolant is not as hot as with the FD thermoswitch. (At least that's my theory, and for sure it is much easier on the battery.)

The left three pics in posts #67 of Dale's article linked above show the engine compartment's fan mod cable assembly removed (which was tucked under the four cooling fan relays). I found the easiest way to remove it was first to remove the bracket holding the relays (two 10 mm bolts), which allowed me to lift up the bracket with its relays and pull the mod cable out & up. Then the mod cable was removed, the stock cable was plugged back in, and the bracket re-mounted.

The right two pics in post #68 of Dale's article show the entire fan mod cable "assembly" after removal from the cabin. One portion of the cable (blue connectors) is mounted behind the PCME on a plastic partition. When it is removed and the control box is removed (one 10 mm nut) from the ECU bracket, there will be one blue connector still mounted on the partition. That connector is removed and joined to the hanging blue connector above it.

There will still be two wires connected to the other portion of the fan mod cable assembly, and the rest of that assembly is routed behind the metal wire guide on the firewall below and behind the glove compartment. One of the white fan mod connectors is visible below the wire guide and will now be disconnected. The other end of that cable extends up high to the OEM connector, and also has to be disconnected. Then the fan mod cable must be removed from behind the wire guide.

I removed the two 10 mm wire guide mounting nuts to loosen it enough to thread out the cable; that was tricky because of the two wires from the other portion of the cable assembly. Those wires could be cut, but I chose not to do that.

Lastly the two white connectors remaining in the car at the firewall need to be connected. The upper one "floats," and is difficult to reach. I used a long pair of bent-nose pliers to grab and hold the upper white connector while pushing up on the lower one to mate them. It took a while but eventually "clicked" the locking tab.

That was it for me, except taking pics. I now make a practice of opening the hood for faster underhood cooling, if the fans are running just before shutting the engine down.

 

Thank you for taking the time to respond so informatively. It makes more sense now. I'll probably end up leaving the fan mod since I live in South TX. I'd rather have to charge the battery and have the engine compartment cool off better. I hear the fans running on many cars after shutdown and I know it won't hurt, other than the battery. My S60R did the same thing and I think it's good for a turbo car since they tend to have some high under hood temps.