Replacement Batteries

Archives of Posts to the NZ MX5 List back in 2001
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Mathew

Replacement Batteries

Post by Mathew » Tue Aug 28, 2001 11:25 am

My poor battery is finally on its last legs (not bad for at least 7 years old-possibly 11) and I am resisting forking out a fortune for a mazda replacement. All auto electricians I have been to list the replacement for a mx5 as being a plain old unsealed, unvented battery. Is it really safe to use these seeing as Mazda supply a vented one?, and can I buy a normal battery and silicone the old batteries cap and vent pipe on to it to make it vented (or is there a major difference the the internals of a vented and non-vented battery).


Matt Avery
Deep Video Imaging Ltd
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www.actualdepth.com

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Gary Morrison
Need, more, 5-ing, time....
Need, more, 5-ing, time....
Posts: 100
Joined: Sun Jun 04, 2006 3:24 pm
Location: Wellington

Replacement Batteries

Post by Gary Morrison » Tue Aug 28, 2001 11:51 am

Matt,

Don't give up on your battery yet... how have you tried recharging it? I
have a small plug-pack type charger I bought from Repco... it gives about 1
amp charge current, ideal for the MX-5's sealed battery... you absolutely
DON'T want to charge it with the usual high current charger. After 8 months
of sitting unused I put mine on charge for several 24 hour sessions and when
it went back in the car the engine fired on first turn of the key... 11
degrees temperature... it has been started a dozen times in the past week as
the car has been shifted from bodyshop to alignment shop to upholsterer and
back... not a problem. And the battery is 10 years old!!!

If you really do need a new battery you can get the sealed ones from your
Mazda spares department, I think they've come down in price recently, and
they'll last twice as long as an "ordinary" battery.

Gary

carl.halvorsen

Replacement Batteries

Post by carl.halvorsen » Wed Aug 29, 2001 6:13 am

I agree Garry, I thought my battery was had it. I bought a new Mazda one at
the old price ( phew). I charged my old one up a couple of weeks later with
the 1 amp trickle and wonder of wonders it was back to normal again.

Carl

STANLEY, Murray

Replacement Batteries

Post by STANLEY, Murray » Wed Aug 29, 2001 10:10 am

Is the concern about using a normal battery charger on an MX5 battery a bit
overrated? My 91 car still has what I assume to be its original battery
fitted and it has gone flat twice in the 5 years I have had it. On both
occasions, I have put the flat battery onto my conventional battery charger
overnight, and it has been good as gold in the next morning. It normally
starts off with a high charging current and then settles back to around 4
amps. Am I missing something here, or have I just been lucky?

Cheers
Murray

Gary Morrison
Need, more, 5-ing, time....
Need, more, 5-ing, time....
Posts: 100
Joined: Sun Jun 04, 2006 3:24 pm
Location: Wellington

Replacement Batteries

Post by Gary Morrison » Wed Aug 29, 2001 11:06 am

RE: Replacement BatteriesTo give a complete picture of the battery issue I
offer this complete explanation written by an acquaintance in the San Diego
Miata Club. It should answer all questions.
Gary

NevadaBob's Miata Battery Story...
The battery in automobiles today is not far removed from the first lead-acid
storage batteries developed in 1859 by Gaston Plante for use in telegraph
equipment. An electrochemical process between the lead, lead dioxide and an
aqueous solution of sulfuric acid, is constant. What has changed in the
intervening years is the technology applied to better materials and advanced
production methods.

If you knew about battery maintenance in 1947, the same procedures would be
valid on automotive batteries in 1997. The liquid electrolyte, sulfuric acid,
must be maintained by addition of water to replace the liquid that is boiled
off during the charge and recharge cycles of normal use. The inevitable spill
of acid on or around the battery would have to be cleaned to prevent corrosion
of the metal. The battery posts would periodically need to be wire-brushed and
cleaned to remove the corrosion present there as well.

Of course we do have maintenance-free batteries now, but the maintenance still
seems to be required, and if you get 3 years on a car battery that seems
pretty good. If you leave the lights on, or the battery doesn't want to crank
the car over, just throw it on the battery charger for an hour or jump start
the car and drive it around for a while. If that doesn't work, toss in a new
one.

Along comes the Miata, and things change. As retro as the Miata was intended
to be in styling, the electrical problems that were common in the British
roadsters of days past, were not in the plan. Since the Miata was meant to
drive, and not to work on, the battery had to be as reliable as the rest of
the car.

In a normal lead-acid battery, the electrolyte is sulfuric acid in sufficient
quantity to cover the lead plates in each battery cell. This type of battery
is referred to as a wet or flooded cell battery. The main drawback to this
type of battery is the continued maintenance and possibility of spillage of
acid during maintenance or an accident.

About 1958, attempts were made to immobilize or fix the electrolyte in the
cell of the battery using various methods. One of these was to use silica gel
to bind the water present in the electrolyte solution into a jelly. Just
imagine a battery full of cherry JELL-O. These type of batteries are used in
many applications and are referred to as gel cells.

For the record, the Miata battery is NOT A GEL CELL.

In 1985, when the Miata was taking shape in Irvine, a new battery technology
was being used in military aircraft. The paramount considerations of power,
weight, safety, and reliability were the selling points of this new type of
battery. The new technology was AGM or Absorption Glass Mat. This technology
was an evolution of previous battery technologies, including gel cells.

In AGM sealed batteries, the acid is absorbed between the lead plates and
immobilized by a very fine fiberglass mat. This glass mat absorbs and
immobilizes the acid while still keeping the acid available to the plates.
This allows fast reaction between the acid and plate material. The intimate
relationship of the electrolyte-filled mat and the lead plate, allows the
construction of a smaller battery, using less electrolyte and metal plates.
This means a smaller battery with nearly equal power ratings to a wet-cell
battery of larger size and weight.

This Miata battery uses the AGM technology and is manufactured by the
Panasonic battery division of Matsushita Battery Industrial of Japan. The
Panasonic battery can only be purchased through Mazda dealers.

A replacement battery is also offered by a company in Anaheim, virtually in
the shadow of Anaheim stadium. WestCo (1-800-214-8040), offers a battery of
the same AGM technology as the stock battery.

The WestCo battery has a rating of 475 cold cranking amps (CCA) to the stock
batteries' 440 CCA. As far as capacity, the WestCo is 35 amp hours vs the
stock 32.

The Panasonic battery is vented to the outside of the trunk through a small
rubber hose. This vent removes the hydrogen gas that can accumulate inside any
battery during use. The amount of hydrogen developed during the use of an AGM
battery is quite small when compared to a wet-cell battery. The WestCo battery
does not have any vent, as it is sealed. WestCo claims the gas generation is
so small, that venting is not required.

The only real difference in the two batteries is price. The Panasonic battery
can be obtained for about $129 at Mazda dealers. Of course, this does not take
into account any discount for being a San Diego Miata Club member. Check the
newsletter for participating dealers. Due to the original classification of
this battery for shipment, it can not be shipped via UPS.

WestCo sells their battery through many of the vendors of Miata accessories,
such as Dealer Alternative, Moss Motors and Imparts. They also sell the
battery direct through their Anaheim facility. For $84.95, minus the 5%
discount for Miata Club members, the WestCo battery is very enticing.

The only real difficulty with the WestCo battery is the terminal posts. The
posts are reversed, as to polarity, when compared to the Panasonic battery.
This will cause an interference with some aftermarket power antennas, due to
the length of the battery cables, so check with WestCo first. Several club
members use the WestCo battery with no problems.

How will you know if you need a new battery? With most cars, a jump start and
driving around will bring a low battery back. Try that with a Miata and
chances are you will think the battery is history. Not so fast!!

One of the differences with the AGM battery compared to the wet-cell battery
is the recharge rate. That is, how fast you can put energy back into the
battery. With a wet-cell battery you can "quick charge" it at about 20 amps or
more. Usually this is when you would boil the electrolyte right out of the
battery. The AGM batteries require a lower charge rate, for a longer time
period. If your battery will not crank the engine, you should charge the
battery at a rate of 1 amp or less for 18-24 hours. If you try and charge it
like a wet-cell battery, you will destroy the battery.

Those of us who enjoy our Miatas everyday-it's our only car-usually don't have
a problem with the battery going flat, unless we leave the lights on. Those
who only get the opportunity to drive their Miata on weekends sometime will
encounter a low charge on the battery. This is due to the constant electrical
load, known as dark current, on modern automobiles. The memory for the clock,
radio stations, engine computer all take small amounts of power from the
battery. Those who add alarm systems, etc. might have a greater dark current
than stock.

WestCo has a small battery charger for the Miata for those who drive their car
infrequently. The EZ-12R is a 1Z2 amp charger that will automatically maintain
the charge in the battery. The advantage of this charger is you can leave it
plugged in and it will not overcharge the Miata battery.

Some people might think that the easier solution would be to put a
conventional wet-cell battery into the Miata. Indeed there are battery
manufacturers who sell wet batteries for our beloved roadster. Before you go
down this road, consider the dangers involved.

The generation of hydrogen gas in a wet-cell battery is much greater than in
the AGM battery. Even those batteries that are vented still have the problem
with all that liquid in the trunk. The potential for corrosion in this area is
very great. Battery acid on your luggage and clothing would not be too cool
either. In a rear end collision, the potential for the battery to crack open
and spill, or possibly explode, should not be discounted. When you consider
the cost of a good wet-cell battery is nearly that of the WestCo battery, the
justification for putting a wet-cell battery in the Miata really makes no
sense. It is false economy.

Some manufacturers are even pushing wheelchair batteries for replacement in
the Miata! I don't think I like the connection.

Overall, the original Miata battery and the WestCo replacement are quality
products that fit the Miata like a string-back driving glove. This is the
first car I have owned where the only battery maintenance I perform is to dust
the top of the battery every year. Several club members have batteries that
are 6 or more years old that are still performing well. When you factor this
into even the non-discounted price of the Panasonic battery, that is only $21
a year. About the cost of 1 tank of supreme unleaded.

-Anthony Wilde, San Diego Miata Club.

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