ND battery under-spec'd?

[TrackAttack]

I do understand the 124 is an MX5 base, but I doubt it uses Mazda electronics or software. Its the same principal is the BT50/Ranger, and the electronics are very different between those 2 also. To keep on track this is speculation, as we like speculation...

Red_Bullet, because I also don't have an ND, and I'm not about to test a customers vehicle to prove/disprove this. Just adding an idea, and defending my line of work. My evidence would be to get an answer from the horses mouth so to speak.

I think would definitely use the Mazda's locking system. The functionality is identical.

I stand corrected, I was not aware they were so similar but alas, a little bit of research goes along way. Perhaps this is adding to the headaches then?

[OMY005]

All this speculative talk about different keys maybe causing the car to wake up and drain more current from the battery...

Why doesn't somebody stick an current-meter in the circuit and look what really is going on. I have an current-meter but no ND. Having some evidence might be useful to resolve this speculative thread once and for all.

When I get a chance I'll do this with mine with the key fob transponder inside the car, outside but close by, and out of range (how far?).

Andrew.

[bruce]

Any spare/service keys left in either cars?

[RBH58]

Any spare/service keys left in either cars?

Nope

[wleung]

Boy -some people don't seem to understand anything about design and engineering...

Lol... I'm happy for the (almost blind?) faith in the field of Engineering, but we still have to be rational about things. Volkswagen & Takata come to mind: Engineers are humans too.

Anyway, if we get into semantics, it's not really a 'design' issue as the battery clearly works for a significant number of people. It's probably some problem in the manufacturing or supplier process that has yet to be detected and solved.

The car is also not manufactured in high numbers like the Corollas, so they can't afford to change things as often to improve manufacturing capability. I think an eager mechanic or mx5 fan will find out the root cause though.

I think people have already suggested:
1) Battery fault that's not always detectable (since your dealer has taken one measurement at a point in time).
2) Alternator fault that's not always detectable (since your dealer has said it was in-spec during their inspection).
3) Abnormal power consumption when car is off. (wonder if anyone has tried to compare mA's drawn when the car is off).

I'll add another:
4) Maybe a poor connection somewhere? Bad grounding, and alternator doesn't charge when driving? I'm guessing that'll give an error code though.

[wleung]

Whilst I know little about the Fiat, I do doubt it registers anything on your ND. It will be looking for a very specific signal, which another Mazda can transmit, but it would be like using the wrong key so the car would see it and determine it to be wrong, whereas with the Fiat it shouldn't even transmit across.

I'm super curious about this and next time I'm chatting to a Mazda Brainiac from MA, I might just ask about the possibility of keys registering and waking a car up if they are for another car.

If the car actively looks for the key due to some event, then it's not always necessarily another Mazda that wakes it up. It could be other brands that integrate a similar product.

I've often wondered how modern transponders work, and how different models differ (e.g. Mercedes S-class one wouldn't be the same as the one in my 3). My older BL2 Mazda3 requires me to push a button before the car attempts to detect my key, so if I was the Engineer, there's no real need to waste power pinging for the key until someone pushes the door button.

Also - note that Mazda may not design the transponder system, but perhaps only integrate it. My Mazda transponder has the words "Mitsubishi" finely printed on it, and I'm positive that I've seen a different brand of car use the same type of key.

An interesting aside: Anyone else notice how the Mazda entertainment screens are identical to the ones in the Mercedes C-classes? I reckon they source them from the same manufacturer.

[OMY005]

All this speculative talk about different keys maybe causing the car to wake up and drain more current from the battery...

Why doesn't somebody stick an current-meter in the circuit and look what really is going on. I have an current-meter but no ND. Having some evidence might be useful to resolve this speculative thread once and for all.

When I get a chance I'll do this with mine with the key fob transponder inside the car, outside but close by, and out of range (how far?).

Andrew.

I've got myself a multi-meter now so I'll try and check it this weekend.

Andrew.

[OMY005]

All this speculative talk about different keys maybe causing the car to wake up and drain more current from the battery...

Why doesn't somebody stick an current-meter in the circuit and look what really is going on. I have an current-meter but no ND. Having some evidence might be useful to resolve this speculative thread once and for all.

When I get a chance I'll do this with mine with the key fob transponder inside the car, outside but close by, and out of range (how far?).

Andrew.

I've got myself a multi-meter now so I'll try and check it this weekend.

Andrew.

Hooked up the multi-meter this afternoon for a few quick tests. And it seems to draw about 0.07A whilst unlocked or locked with the key in and out of range. This jumps up-to about 1A for a few minutes after unlocking. Unfortunately I managed to blow the fuse in the multi-meter by opening the door and don't have a spare fuse yet, so my testing was cut short.

Andrew.

[Red_Bullet]

Great work! 70mA is very little idle current draw. (About 0.84 watts(.07*12)) What is the AMP Hour rating of the battery?

Some quick back of the beer coaster calculations on a small battery 45AH :

45/.07=643 hours or 26.78 days to completely discharge a fully charged battery.

Assuming 30% charge left required to start the car. 70% used by idle current drain.

0.7*45/.07=450 hours or 18.75 days

It's a really bad idea to fully discharge a lead acid Car battery, they really don't like it. After a couple of full depth discharges AH capacity can be reduced substantially. This might explain why the battery is unable to last a reasonable time between charges.

[RBH58]

Mine just had an 8 day break and there was JUST enough juice to fire it up. If it hadn't started first time I'm not sure it would have.

And even the best case scenario of 19 days is not very good. I think one month is a reasonable (if low) expectation. So the battery is clearly under spec'd for the car.

[TrackAttack]

Also - note that Mazda may not design the transponder system, but perhaps only integrate it. My Mazda transponder has the words "Mitsubishi" finely printed on it, and I'm positive that I've seen a different brand of car use the same type of key.

That is correct, however I would assume (dirty word again) that it is a design spec, and components outsourced. Mazda PATS keys and transponders have changed manufacturer many times, and often change back. Back in the BK/GG days, the first of the flip keys, we had draws full of remotes, and would always look at the remote manufacturer to check if it was programmable to a vehicle as it could be siemens, Mitsubishi etc. etc.

With the dark current test, make sure you latch the bonnet catch so it thinks the bonnet is closed

[RBH58]

Mine’s dead again after 14 days idle. City Mazda thinks 14 days is acceptable! Mazda Australia have been contacted. Waiting for a response which will publish here.

Dialog on miata.net has reported that Mazda America seem to be conceding “a problem” and are looking at a possible fault in the RF’s cruise control circuit. They are advising drivers to turn the cruise control off before shutting down. miata.net members are currently testing for parasitic drain with/without the CC turned off. Seems the RF got a different setup for the CC.

Any other RF owners getting flat batteries?

[RBH58]

From miata.net overnight. Someone decided to test the Cruise Control On/Off theory...

”I measured the battery current in my 2017 RF CS. The culprit does indeed seem to be the Cruise Control. If I turn CC off such that the indicator in the instrument cluster goes out, then the battery current falls to about 10mA after some time (about 20 minutes I think, I didn't time it exactly). There are small fluctuations, I think from the blinking LED in the instrument panel.

I tried with AKE on/off, car locked/unlocked, hood open/close, windows up/down, but none of that makes any difference to the final current. It seems to be just the Cruise Control. So looks like best thing is to make sure you turn off CC when parking.”

[JBT]

Any other RF owners getting flat batteries?

I was talking with a guy from this forum with an RF and he is also getting the dying battery issue.

[RBH58]

Any other RF owners getting flat batteries?

I was talking with a guy from this forum with an RF and he is also getting the dying battery issue.

They did a survey on miata,net and 50% (26) of the (52) RF owners that responded had experienced flat batteries after 12-14 days idle. It's definitely an issue but seems to be isolated to RFs. Got mine in Feb. I've had to jump start it 4 times.