- My model of MX-5 is: ND2 RF
- I’m based near: __ESSEX
- I’m looking for technical help or recommendations on: __ALTERNATOR OR BATTERY?
Hello I’m hoping if anyone has got has got any help or information regarding my problem?
Like many over winter the MX5 saw little use and I found the only way I could start it was to use a battery booster. I put the battery on charge and it did get over 13v and started the vehicle. Today after leaving the car for a few weeks I tried to start the car again , and again it would not start , so again I had to use the booster.
I decided to give the car a good long run and today have done about 70 miles in it with no problems, or dashboard lights etc . On returning home I tried to start the car again , and again it would not start .
I decided to call the AA thinking my battery may be duff and it did show 11.5 volts , he also put a tester on the alternator which at idle show just over 12v , he seemed to suggest this was not high enough? The strange thing was when put under load , electric seats , lights etc the alternator was pushing more voltage into the battery .
Not knowing what a normal alternator voltage at idle is ? I now don’t know if I have an alternator problem, an alternator regulator problem or a battery problem , bearing in mind the car has only done 4000 miles .
Simon
How many years old is the car, and does it always sit unused over winter? If allowed to go flat even once, car batteries are halfway to the scrapyard.
You normally get about 14.4V with the engine running, so the battery AND alternator could be bad.
Battery voltage immediately after charging is artificially high as it includes surface charge. You only get a true reading after 24h, or after turning the headlights on for a couple of minutes.
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Hello Roger ?
The car is 3 and a half years old and does go unused over winter ( unfortunately) it has only done 4000 miles so I would be very annoyed if the alternator had gone .
Is it unusual for the alternator to push more volts under load ?
My money would be on the battery. As it looks like you need a new one anyway unless you can beg, borrow or steal one I would bite the bullet and buy one. Try Tanya: www.tanya.co.uk, they usually have stock of most sizes and types / warranty periods, Look for a YUASA.
Fit the new battery (next day Delivery!) and see if the problem goes away. If it’s still there then probably looks like a bad alternator as well. Batteries do not lkie long periods of non use and cold weather just makes things worse.
Invest in a Battery Conditioner, CETEK or similiar and leave it plugged in over the winter or anytime you are not using the car for a period.
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Are these batteries Gel mat or wet?
If Gel, its especially for the bin…even if wet it’s never going to get to 14.4 volts reliably again.
Like spoiled girlfriends, they won’t tolerate being ignored over extended periods and are attention seeking little madams.
I’m not advocating plugging a girlfriend into anything incidentally. 
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The car has the i stop ieloop thingy and currently has a factory fitted Yuasa battery, the owners manual says the battery needs to be an N55 s ( this mean’s nothing to me ) are there any alternative manufacturers? or could you tell me the specific Yuasa model number please?
Thanks
Your car should have stop/start and will have a capacitor. The battery for these cars is different to a normal battery as is the charging system.
It is most likely to be the battery but before buying a new one I would check the electrolyte levels then disconnect the battery (both terminals) and give it a long charge preferably with a charger that has some ‘intelligence’. You may consider taking it out and giving it a gentle shake during charging to get the electrolyte moving around between the plates. Once the charger has indicated that it is full put it back in the car and see if it has ‘recovered’.
The ‘correct’ battery for these cars appears to be only available from Mazda at a ‘reasonable’ cost. If you do a search there is another thread regarding this. Nd1 12v battery needed? - Technical Area / Electrics & ICE - MX-5 Owners Club Forum (mx5oc.co.uk)
If you do need a new battery and decide not to use the Mazda one please do come back on here and tell us if it worked out OK.
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Hi Malc, thank you , when you say the charging system is different could it be possible that my friendly AA man was confused by the alternator output? Also I contacted the battery suppler suggested by the other poster and they said the Yuasa battery had been discontinued and said their Enduroline 048 EFB would be a suitable replacement, have you any thoughts on this ? It seems from some of the reviews it has been successfully fitted to various later MX5 ‘s
Simon
If it has i-eLoop, it’s an EFB battery. They cost slightly more than normal ones and can cope with a bit of discharge.
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To date I have not seen anyone on this forum that has fitted a ‘non factory’ battery to the ND2. Personally I would only fit the Mazda one at the moment until someone you can ‘trust’ has fitted a different one and reported back.
The plates on our batteries have very little room between them and require a ‘special’ charging routine which requires very high amperage and constant higher voltages. The smart chargers appear to be able to keep our batteries in good condition but if they become discharged then I think we may be in trouble trying to charge them back up. This is why I suggested you ‘shake’ the battery to get the electrolyte moving about.
The system on our cars can get confused by ‘voltage’ as shown by some stop/start systems not working even when the battery is ‘full’. The quick fix is to remove the negative terminal for a few minutes and reattach. (Two of us have just had to do this to reactivate our stop/start after the winter lay up) Goodness knows what is going on under our bonnets these days. Doing the above may rescue your situation as well, it is free so worth a go.
Do please let us know how you get on as it is all new to us. Remember that the older cars had Panasonic batteries fitted by Mazda and history tells us that replacements were not a patch on the factory originals.
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The Westco replacement for the AGM battery on the NA has a good reputation. Mine did 7 years all-season use before the car was written off, which is as long as the original Panasonic lasted.
I did swap the OEM battery in a Mazda 6 with i-eLoop for a Bosch EFB equivalent. It worked just the same as the OEM battery, that is to say not very well. The problem is with the i-eLoop software and sensors throwing up “iStop not ready” and blaming poor battery health when there is nothing wrong. Disconnecting and reconnecting the battery fixes it for a while.
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That is interesting regarding the Westco battery, you appear to be at odds with most reports on here regarding it’s longevity.
Just a quick update, after reading some of the advice on here , I decided that I would try a new battery first . I rang my local Mazda dealer ( Romford) this morning to see which one I required and if I could order one , they said that they did not stock the required battery, but they could order one , but it would have to come from Europe and they were not sure when , I politely declined as I was not willing to wait.
I then found the Yuasa battery in stock at GSF car parts local to me and available for click and collect although it did cost me £160.00. The battery is now installed and fingers crossed all will be ok .
I’m sorry Malc , even though the alternative batteries were up to £30 cheaper, I decided I would leave it up to others to be the Guinea pig .
I have also shaken the other battery and put it on charge just to see if it’s worth saving.
Simon
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If you do not use the car much don’t forget to keep the new battery in tip top condition by popping it on the ‘smart charger’ at regular intervals. 2 weeks is my ‘rule’.
So pleased you are sorted.
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A far more fun way to keep your battery (and everything else) in tip top condition is to take the car out for a spin once a week for an hour or so. 
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