I’m probably going to need a new battery soon. My car was laid up on a couple of occasions by the previous owner and the battery looks to have suffered from this. Although the car has never let me down, it has always sounded, on starting, like the battery is struggling a bit, especially if I don’t drive it for a few days, or it gets used for short runs. It’s only going to get worse now the cold weather is setting in.
The current battery is a Yuasa YBX3000 40Ah. Googling batteries for mk2 fives brings this battery up a lot, however reading many posts on this forum suggests I should buy the Panasonic one originally fitted because it is ‘vented’.
So my question is why do I need a vented battery? (It never crossed my mind to buy a vented battery for my 525i BMW when that needed replacing. It had its battery under the rear seat. Nobody was asphixiated over the three years I had that car). Is it something to do with corrosion?
And maybe the Yuasa is vented? I know Yuasa is a decent brand, used a lot on motorcycles and remote control devices like drones and rc aeroplanes.
Given that a new Yuasa battery is less than half the price of the Panasonic (which is out of stock at MX5Parts at the moment anyway) I need convincing that it’s essential for my five.
The vent is the little hole at the end of the case above the cell caps, so any vapour can escape.
Some cars have a small pipe which attaches to the hole and goes out under the car.
Some batteries are sealed some vented.
Expect someone else can tell us why, probably chemistry.
A good tip is to get a battery maintainer like a CTEK, it keeps the battery charged when parked up, I’ve found using that extends battery life by years, before they would die in 3 years.
Vented because the battery is in the boot with no air flow. Under the bonnet the acidic fumes blow away. In the boot they sit there and rot out the battery tray and inner wing. I would fit the Panasonic as fitted by Mazda. They know best!
Thanks - so how does the Panasonic battery dispose of the fumes that are generated? Is there some kind of venting system I need to attach it to? Excuse my ignorance, this is all new to me.
lead acid batteries suffer in terms of capacity and life expectancy if they are repeatedly allowed to fall much below 50% charge for sustained periods. The corollary to that is that a battery maintainer, i.e. a smart charger that can be left connected, is a very good thing for battery health if the car is left standing for weeks at a time.
A discharged battery is vulnerable to freezing, which can happen in winter if the car is left outside. Freezing will damage the battery more or less, the best preventative is to keep it charged.
I had a Mk2 that was a ‘lazy starter’ even with a fully charged battery. Much better when a corroded earth connection was sorted - on the performance frame (or whatever it’s called) IIRC.
Check the earth situation regardless. Earth straps can even be completely absent and the car might still start and run, but the danger is then that the earth current is running through some accidental and inadequate route that could lead to overheating and even a fire.
The vulnerability of batteries to being left in a low charge state can surprise people, but if your battery is going to be run down and left for a while it’s best to regard its usable capacity as half its actual rating. Car batteries can last many years in some cases, especially if in daily use, because the battery is almost always well charged. If you can park off the road and near enough a power source, a smart charger is well worth having and using.
As a non-expert, I’d speculate that venting away to the atmosphere is of most value on a battery that is prone to being in a low charge state, because when it is recharging from the alternator it will take a high current, producing a greater concentration of potentially explosive hydrogen. So lack of vent pipes and your type of use don’t go together well.
The Panasonic has two small vent pipes on the top, one each side. Originally there was a rubber hose that split into two at the top. One to each vent pipe and the single end went through a rubber grommet in the bottom of the battery well inside the offside wing.
I have recommended the Yuasa 5000 for the MK3 MX5 where is sits under the bonnet, so no venting required.
My only recommended battery for MK1 - MK2.5 cars is the Panasonic because of its proven worth and fitness for purpose particularly where car owned long term and left for periods of time without use.
Ideally the battery should be kept at 12.3 volts or above, so if not in regular use an optimate or similar smart conditioner required. The MX5 seems to have an excellent charging system so the gases that are created through overcharging are minimised. Venting is required because it protects the occupants of your MX5 cabin from the potential of noxious fumes resultant from an overcharging battery. People have died as a result of this although hopefully not in an MX5.
The other secret to long battery life is minimising parasitic current. That is the discharge when the car is not in use. Ideally around 25ma but can be significantly higher when inefficient alarms or faulty stereos involved. Easy to check by detaching positive from battery pole and connecting in sequence with a 5v bulb to start and gradually reducing if the current not sufficient to partially illuminate. A healthy level of parasitic current at say 25ma will not light any bulb and will not blow a cheap multimeter:-) Going through the reducing bulb voltage process first is highly recommended though, from someone who has tried to sidestep this with a cheap multimeter and blown a few fuses.
The Panasonic is an Absorbent Glass Mat(AGM) battery and aside from its well documented longevity, is better able to withstand charging cycles than other batteries.
Having preached the virtues of the Panasonic and I have always had one on my irregularly used MK1, the other half has a cheap and cheerful, VENTED, lead acid battery on her more regularly used Eunos. It is nearly six years old but touch and go as to whether it will survive another winter.
Unfortunately a young mother and child were gassed by a faulty battery fitted to under the seat in a Porsche Cayenne (in Florida, 2016). Less risk of that in a MX5, but highlights that a battery in an enclosed space can emit fumes that will likely corrode the body work.
Having said that, I have a regular battery in the boot of my NA, after a fairly new Panasonic gave up the ghost due to lack of use during lockdown. When the car is in the garage, its parked with the boot lid open.
If your battery (including “Sealed” or “Maintenance-Free” ones) has small holes at each side or on the top, these are for venting battery gasses and must be connected to the tubes.
During normal charging and discharging, some gases escape via valves and the vent holes. Maintenance-free just means that most of the gasses generated by the charge/discharge cycles are re-combined within the battery and you don’t have to top-up the electrolyte. In normal operation some gases escape via pressure-release valves (vent holes). Even fully-sealed batteries have emergency valves to prevent over-pressurisation in fault conditions. These gases are acidic and potentially explosive, so if a battery is located in (closed) passenger/luggage compartments (like the NA and NB MX-5s) rather than the (open) engine bay, the gases must be vented to the outside.
A new battery will likely have transit plugs fitted.
Google “car battery vent hole” and “car battery maintenance free”. if you want more info.
Another vote for the Panasonic. They fit the NB correctly and have the breathing capability needed. Considering how long they last they are worth the investment. Try your main dealer as they sometimes have offers on. In addition buy a smart charger. I have the CTEK MXS 5 with the battery extension lead - works well.
Thanks for all your replies, lots of great info in there.
I took the Yuasa battery out last night and sure enough there is some light surface corrosion under where it sits. I took the liner out and there’s no sign of it on the boot wall so looks like I’ve caught it early. I will treat the corrosion with Hammerite Kurust and then spruce it up with a lick of paint.
No sign of a vent tube but the little white spigot to fit it to is there. I’ve ordered one and will start the hunt for Panasonic battery on Monday.
In the meantime, I trickle charged the Yuasa battery overnight and It’s holding at 13.1v three hours after coming off charge. It has vent holes, so I’ve ordered a couple of vent tubes off ebay and will attempt to cobble something together with them as a temporary solution. Can’t be without my mx-5 driving fix for too long!
There are many good batteries available that will fit a NB. I go for the largest Ahr rating and cranking current spec. that will fit in the boot space . I currently use a BOSCH vented ,lead acid battery obtained from Tayna and have had excellent service. It is important to fit the small diameter vent pipes (illustrated in this topic earlier) However I always fit a plastic tray underneath the battery base, should there be any liquid escape. Usually a cut down 5 litre oil container makes a suitable item although I understand that MX5’s originally had a tray to fit the Panasonic type. If you use your car throughout the year then it is a good idea to use a " intellegent" trickle charger on a regular basis.
In my case I will put the car on SORN until the spring so I take the battery out and bench charge using a small charging device as mentioned earlier in this forum
I agree. I use a CTEK on my 2011 MX-5 and my wife’s 2011 Mazda 2 and very occasionally on my 2016 Skoda Yeti 1.2TSI. All of the cars don’t do much mileage as we are both retired. But I love cars! .
Both Mazdas have done around 30000 miles and the Skoda around 18000 miles. The MX-5 is only used for runs of >30 miles whereas the Mazda 2 does more local running - to the leisure centre and shopping etc.,
The Yeti does mixed motoring.
The Mazda 2 battery was changed yesterday as it was failing to hold its charge for very long despite using the CTEK. I had no complaints about paying £80-00 for a Varta battery to replace the original 10.3/4 year old one!
Perhaps I should get the MX-5 battery tested?
There are only two batteries I recommend and use, either the OE gel Panasonic or the Bosch S4 or S5, make sure the breather vent tubes are on, for all the MK 1’s and 2’s.
M-m
The go to battery for Ducatis like my 999 is the Yuasa AGM.
Great build quality, made in the UK! High CCA for turning over big high compression pistons and sealed reliably enough that the battery is installed on its side as standard.
I also have one in my stop/start 320d
I’ll have to investigate these. Do the Bosch batters need a male tube connector. I fitted a Yuasa battery in the Jag (also boot mounted), but Jaguar provide tube connectors that can be swapped from car to car. Current have some no brand battery put in by the MX5 garage who welded my Mk1 (it was in so long, the Panasonic battery went flat and was ruined)…
I had originally brought a new Panasonic to replace this in 2018, but the 2020 lockdown ruined it. It won’t hold charge now for more than a week., even if disconnected from the car.
