Thanks - this indeed sounds like attaching the earth charger’s clamp before the current sensor would be a good idea. I tried attaching it either directly to the earth post or to some nut around the suspension mounting point, and there was no difference in results whatsoever (i-Stop still not working) - now I probably know why (see above)…
This Mazda pdf is very interesting to an OCD electronics engineer like me. Many thanks to Robbie for letting us see such a clear and well reasoned document. Even non-technical people should understand it given a bit of patience in reading it. I only noticed a couple of poor (confused?) translation points, and they are not significant.
At work back in the 1970s and 80s a small group of us did a lot of research into extending the operational life of our film camera batteries which were usually 12V 7Ah Ni-Cads. We were getting through large numbers of individual cells failing in a short time (mostly 10 cells or sometimes 11 made up a battery). There was also a lot published in places such as Electronics and Wireless World and a few professional bodies.
It turned out that the Ni-Cad equivalent of the EFB dendrite growth in that Mazda pdf was the main reason for failure, followed by loss of water from the electrolyte, both down to how they were charged.
The Ni-Cad crystal bridging could be cured with a shock pulse to burn it away, in our case connecting a big very low ESR capacitor (10,000uF 50V). Filled to about 20V it held enough joules to fix the offending 1.2V cell with one pulse. We experimented with assorted current limits (resistors or lengths of wire) to protect the capacitor, but in practice the joules were not sufficient to damage such a big beast if we gave it a decent rest to cool down inside.
Crystal growth could also be minimised by fast charging (half hour or less!) but this required very careful monitoring of the cell temperature. The Mazda run and conditioning techniques effectively do this by coulomb counting with a charge-current limit: for conditioning measure the SG to work out how much charge is required, then dump it in as quickly as possible without warping the plates or over-boiling the battery.
But before we could put our own Ni-Cad research into effect commercial specialised Smart chargers began to appear and these measured the internal resistance of the battery and looked at a history curve showing how the charging was progressing, many could also monitor battery temperature with an additional contact. Problem solved sufficiently to be economic; so we stopped our research as it was no longer required. And then the more predictable Ni-mh and Li-Ion cells took over from toxic unreliable Ni-Cad.
My conclusion from reading the Mazda pdf is that the occasional blue-moon Smart charge of an EFB Stop Start can be done, but one should definitely not consider it as a regular routine. As Robbie hinted at a few weeks ago. By all means use a Smart to put just enough into it to compensate for several weeks standing unused, simply to allow the engine to be started without taking the battery too low, but then it is highly desirable go for a drive of at least half an hour to allow the car’s own system to finish the job properly.
It seems to me that if the car is to be left standing for any length of time, it is a good idea to disconnect the -ve terminal, as the very low self discharge with these modern calcium based EFB batteries allows for up to a year before needing a boost, but the car’s dark current will kill it in just a couple of months.
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So, as the OP of this thread, I concluded (based for the PDF atttached - thanks !!!) that with my charger, it may be impossible to fill the i-Stop Miata battery (the one as per the picture) up enough for the i-Stop system to work. However - and this is a very important question, so I’d appreciate it if someone could try and help me find a possible answer to it - my Authorized Dealer do have this Mazda PDF, so they should be following the instructions contained there in and use a charger which is up to the job - right? But if so, why - with all 3 batteries replaced by them so far - after some 2-3 weeks since collecting my car from them, should the battery charge drop down below the charge minimum threshold, and the i-Stop system cease functioning again? It’s quite cold in Poland at the moment, but this has happened three times starting in the summer, when it was really hot?!!
What is EFB please???
Read it here from the experts
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M have you tried disconnecting the - battery terminal for a few minutes and then reconnecting it?
My stop start ceased working within 50 miles of new and was the same for several months. Only when I fitted my interior footwell lights and disconnected the battery did it start to work again. Worth a try as it will cost little in time and nothing in monetary terms.
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Slightly different situ here, as I have an open warranty case here and am afraid any DIY attempts could void the warranty. But I will keep you posted guys on any development; thanks for everybody’s input anyway!
I do not think it would be classed as a DIY attempt as it is a reasonable thing to do for many reasons other than your issue. Attaching a non compatible charger is more likely to result in a failed claim so I would keep that action from them just to be on the safe side.
But if this is how you feel then so be it.
OK guys - I really don’t know what to think about it. This thread - even though it looks like battery-problem oriented - has indeed been set up because using my automatic Bosch C3 charger, I could never give my battery enough juice to make the i-Stop system work… I tried everything and - after many eye-opening posts here (like the one with Mazda PDF link, which helped me realize my charger really isn’t up to the tasks, as it doesn’t check any of the Q&A section boxes), I was about to give up, and find myself another charger that would. And today - a week after all night charging and then driving the car with s-Stop system “not ready” - low, and behold: even it is quite cold outside and I only managed to make perhaps 3 kms from my home - it is working again! Now, go and figure - but while you do please share your thoughts with me…TIA
P.
From my experience you will never work it out!! 
I had a VW Golf with start stop and a Mazda 2 with start stop. Both always worked perfectly whether short journeys or not.
My current Volvo V60 with start stop is dependant on, temperature and whether the battery is any good or not.
12000 miles 2 years old and diagnosed today the battery is dead even though it starts the engine every time! EFB and not AGM.
I believe the ND is too?
Lets put it this way, if I ever have to buy a new one it will be AGM.
Have a read of this thread about CTEK chargers.
As the OP I thought I owe you some info from Mazda EU:
- AGM batteries are NOT used in Miatas due to their considerable weight
- A charger like my Bosch C3 aren’t suitable for Miata’s battery due to its charging current being only 3.8 A, while the battery should take something in between 7-12A - meaning it will never be fully charged with this little charger. ■■■■■■!
Piotr
PS. I stand corrected; AGM and Gel are NOT the same thing of course, and I was advised the above on the AGM ones
I can’t claim to be a battery expert but from what I’ve gleaned over the years, none of thst sounds right to me.
AGM and gel batteries are not the same thing.
AGM batteries should be lighter if anything, as their inherently higher CCA ratings should allow a smaller battery to be used.
First I’ve heard that 7 to 12 amps are necessary to charge a battery. So all the charger manufacturers are supplying chargers that won’t charge a battery?
I really don’t think so…
What I’m saying applies to conventional cars of course, I know stop/start cars are different as they have black boxes that control the way they charge and that muddies the waters rather.
First I’ve heard that 7 to 12 amps are necessary to charge a battery. So all the charger manufacturers are supplying chargers that won’t charge a battery?
Yes, absolutely! If No2 above was true then CTEK etc have been selling plenty of useless chargers!
JS
Well I do know that Gel and AGM are a different format, but a variation of a lead acid battery. Trying to explain the differences could be long winded.
Likewise, my understanding is AGM are heavier too but can be made into various shapes and sizes as they were originally invented (I believe) for the aircraft industry a while back.
So I have borrowed this explanation direct from the Varta website to assist all.
It’s bit of a read but well explained.
Gel batteries versus AGM batteries
Gel batteries are often confused with AGM batteries. What are the differences and what do the batteries have in common? Both types of battery are VRLA batteries and are equipped with a vent valve. The abbreviation VRLA stands for Valve Regulated Lead Acid Battery. With this closed battery type the hydrogen which is generated by the battery is recombined, so that topping up with distilled water as with wet batteries is not required. Apart from these common features, there are significant differences between gel batteries and AGM batteries.
Gel batteries
A gel battery has a similar structure to a conventional wet battery. The positive and negative electrodes are surrounded by an electrolyte. However, as the name suggests, the electrolyte is not in liquid form but rather is in the form of a gel due to the addition of silica. This provides greater resistance to vibration and the inclination of the vehicle. The encapsulated design facilitates handling and improves safety. If the battery is in an intact state, the user does not need to be afraid of leaking fluid. Therefore, in the trade, gel batteries are often referred to as maintenance free batteries.
AGM batteries
The abbreviation AGM stands for Absorbent Glass Mat. In an AGM battery, the electrolyte is completely bound in a glass fiber mat. AGM batteries are leak-proof and can also deal with inclined positions without problems. This, and their resistance to vibrations are the reasons why AGM batteries are especially favored for off-road and motorcycle use. In comparison with conventional starter batteries, AGM batteries can withstand three times as many charging cycles. The increased performance which is achieved by the structural features, is one of the main arguments for the use of an AGM battery. Long life, excellent performance and greater safety make AGM batteries the premium batteries for modern vehicles.
Comparison of the characteristics of gel batteries and AGM batteries
Gel batteries score highly with their low electrode wear, which results in a longer service life in comparison with conventional lead-acid batteries. However, due to their increased internal resistance gel batteries cannot produce high cold start currents within short intervals. A second disadvantage is their susceptibility to temperature fluctuations.
AGM batteries have been specifically designed for vehicles with automatic start-stop systems and increased power demands. AGM batteries are recommended for all drivers who operate a large number of electrical devices and driver assistant features or who simply require greater starting and supply reliability through an extremely high performance battery. The positive features of AGM batteries include:
- Leak-proofing
- Position tolerance
- Vibration resistance
- Greater Safety
Even if the casing is damaged or broken, the acid remains bound in the glass mat. An uncontrolled escape of battery acid can therefore be largely ruled out.
When is it worth buying an AGM battery?
The high, constant cold start current makes an AGM battery the right choice for vehicles with start-stop technology and recovery of braking energy. Even vehicles with simple automatic start-stop systems and increased power requirements benefit from an AGM battery. The large number of charging cycles increases the service life and therefore cost-effectiveness. Conventional gel batteries are designed for use as supply batteries, but not as starter batteries and certainly not for cars with automatic start-stop systems or vehicles with a large number of electrical consumers. AGM batteries are the modern answer to the need for more dependable energy, environmental compatibility and reliability.
These were very basic checks with a cheap battery tester. When testing my NC’s battery the next day after having it on a maintenance charger (Aldi/Lidl specials) it showed fully charged. Doing the same with my daily drivers battery, an hefty type stop/start battery it would show in a discharged state.
So it got me thinking do I need something better for the higher capacity battery. Both are Yuasa batteries BTW?
My experience…
Well in answer to your question yes.
I had a cheaper charger which was “Okay” for my MX5 tried it on my Volvo with start stop.
It said it was charged but in reality it never was.
Hence why I invested in the CTEK MSX 5.0.
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My experience with an Aldi/Lidlington special is that it was great for my Ducati’s AGM Yuasa but while it will eventually charge the £400.00 truck-sized Yuasa AGM in my stop/start 3 series diesel, it takes forever to do it, so something with a higher available amperage would be an advantage.
The MX5 NC2 2.0 has never needed charging, even during Lockdown 1 and that was the only time the BeeEmm has ever needed it, so not really an issue.
Guys - I’m completely lost. Have just finished topping up the battery in my wife’s Yaris (her usage scheme being very similar to mine in the Miata), and the Bosh C3 only needed one hour to complete! While trying to achieve the same in my car, it lit the Battery Full" light after over 12 hours the previous night - and I still don’t have my battery really full (well - at least the i-eloop screen keeps showing grey around the battery icon and i-stop is still inactive after some 40 km ride).
Just what gives?!! I understand that a battery requiring up to 10A charging current would take a much longer time to fully charge than the Toyota one, which doesn’t even have the Stop/Start system - but shouldn’t it finally charge uo after so many hours?!!!
The description is in Polish unfortunately, but you will understand the specs of this one: https://allegro.pl/oferta/prostownik…ant=9927624465. Should I try and buy it, or push my Mazda Service really hard first to properly diagnose the alternator charging capacity and/or look for a possible current leak to the earth of my vehicle (short circuit of some kind)?
I “think” that I know what you are asking.
Firstly, I also believe we have all been a bit guilty of over thinking these things this year.
Clearly your Bosch C3 does the job on the Toyota battery quite quickly. So just stick with that for that car.
I assume you are worried that you may have a defective charging system on your ND? I doubt that very much in my opinion.
Start/ Stop systems are rather complicated to say the least.
I can confirm that the CTEK MS 5.0 does a great job in keeping things all charged up if needed across the board for many batteries and in particular AGM, EFB types.
Likewise, I can say that if anything will be defective it will be the battery itself 9 times out of 10.
If you are concerned have a full battery test done and take advice from your dealer first and they can put your mind at rest.
Can’t really comment on the charger you mentioned but if it was me I would buy one specific for start/stop as I mentioned above.
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The battery charger you posted the link for seems to cover your needs, buy it.
Connect up as per RR instruction, if all that fails it surely must be the car (systems) at fault. Assuming everything nice and tight, connection wise?