Although I bought this NB Icon some weeks back, I have only just got around to collecting it from a mates house ‘Darn Sarf’. It was fitted with a Lucas battery with vents but not connected to the pipework. A computerised battery test indicated ‘weak battery’ so I checked Halfords site with the reg number and selected a 5 year Silver Yuasa with vents, having used those batteries for a number of years with good results.
Trawling the web seems to suggest that it is the ECU itself which does the regulation, rather than the alternator and 14.6 seems acceptable but gassing threshold is usually about 14.4volts.
I know folk suggest Panasonic batteries but this was not an option in the time I had before the 500 + mile drive North to Orkney and this new battery was the one indicated. Am I likely to have problems with this fitment and can the ECU be programmed to regulate to a slightly lower, more normal voltage?
Ian
forgot to say, arrived home safely after great drive and had no issues with the battery.
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The ECU cannot be reprogrammed to adjust the charging voltage.
Have you get round to getting vent tubes to vent the battery if they are not there, either from a large pet shop re tropical fish, ebay or Autolink UK. If not you will probably get rust in the boot floor.
Our Suzuki Jimny has a similar voltage from the alternator to the MK2 and the battery lasts say 6 years.
Thanks for the swift reply,
All the tubing and grommet is there but the connector sleeves are missing - probably left in an old battery years ago. I have a lathe so can very easily make some from nylon or some such, unless there is something suitable kicking around the workshop. The Yuasa is 5 year guarantee and I’m ok with that but was concerned with such a high rate - above gassing threshold, that it might fall over well before that due to lack of electrolyte.
Regards,
Ian
In Halfords they have those little connectors with the batteries but they get lost after a week or so.
MK1 - MK2.5 MX5 charging rate is around 14.5 volts. I generally see 14.4 to 14.6 volts.
I found this on gassing thresholds…
‘Lead acid is reasonably forgiving when it comes to temperature extremes, as the starter batteries in our cars reveal. Part of this tolerance is credited to their sluggish behavior. The recommended charge rate at low temperature is 0.3C, which is almost identical to normal conditions. At a comfortable temperature of 20°C (68°F), gassing starts at charge voltage of 2.415V/cell. When going to –20°C (0°F), the gassing threshold rises to 2.97V/cell.’
It would seem that gassing may start when charging voltage up over 14.5 on a hot day for the UK.
Given that your charging voltage is at the correct level, I would not worry. It is definitely worth connecting up the vents but I would not expect there to be any venting as such, just a precaution. MX5s generally seem to have a good charging system with no problems unless alternator or other fault. MK2/MK2.5 regulation is controlled by the ecu but the actual regulator is still on the alternator itself. There is no adjustment.
The Yuasa you have fitted is recommended for the MK3 where confusingly the charging voltage is actually quite a lot lower. The main thing is to ensure that the battery is held securely in place in the boot - lots of ‘g’ force. If the original clamping system could not be used or is missing take time to improvise a system that is very secure and check it regularly. Lots of bashed rear wings and rotted out boot floors due to insecure MX5 batteries.
Most problems with MX5 battery drain are due to irregular use and parasitic drain.
The MK2 and Mk2.5 batteries are in a box in the boot floor so tend nor to move but it is still an MOT failure not to have the battery fixed down.
You may have to modify the existing bracket.
Thanks guys for the informative replies,
l’ve just found some solid nylon rod which is a good push fit in the battery holes, so just need to drill them and put a small slot at the inner end to make certain I don’t block the slit at the top of the hole and the rubbers will go over easily with a bit of silicone grease.
I’ll keep an eye on the tell tale on the battery top and yes, the bracket will need the angle part repositioning - no big deal really.
incidentally Drumtochty, i have a Sister in Kincardine O’Neil and often use the Cairn O’Mount Road. Good to know there are other MX-5 enthusiasts not far away (well, 250 miles plus a Ferry!). We are off next weekend to the Fortrose and Rosemarkie Rally and then Motormania in Grantown on Spey the following day but will be in the MG RV8. Looking forward to lots of MX fun next season!
Ian