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Your Car Battery
What do you need to know?
An awful lot depends on your car battery. A healthy battery brings the car to
life on a cold morning – you’re safe, warm, and on your way. A dud can mean a
cold wait, unhappy passengers and missed schedules – and the AA attends over
500,000 battery-related breakdowns each year. Not much of a choice really – but
how to make sure the battery is up to its job? Here are some guiding notes.
Battery care
Car batteries suffer if heavily discharged, damaging the cells as well as
failing to start the car. So, if the charge warning light comes on, or if the
battery seems very sluggish on starting, get the system checked as soon as
possible.
If the battery has removable vents (maintenance-free batteries may be sealed,
and low-maintenance batteries may not be easy to open) check the electrolyte
level. Top up to cover the plates with distilled or deionised water – de-frost
water from the ’fridge is ok provided it’s absolutely clean. With maintenance
free or low-maintenance batteries, topping up should only be necessary every
year or so: have the charging rate checked if much water is being lost.
Corrosion of the battery terminals can cause starting problems. Before removing
either battery lead make sure any radio and security codes are noted as given in
the handbook, and the engine must be stopped. Remove the negative lead (Black -
) first, then the positive (Red + ), and just lightly scrape the battery posts
and the inside of the terminals. Coat the faces with petroleum jelly and
re-attach, tightening firmly but not over-straining the fixings. Re-enter any
codes.
Battery choice
Modern car batteries have a life expectancy of around five to seven years, but
it’s pretty much impossible to predict when the end is getting near. So, the
options are to soldier on until it fails, or change it at say five years – and
the latter is probably the best option. At least this gives you the chance to
choose a suitable battery at your convenience. But what to look for?
The basic voltage, current rating and size of battery will be given in the
dealer’s catalogues, and these must of course be right for the make and model of
car. There will then be the choice of battery make, capacity, grid type and
warranty life. These factors will be reflected in the price, as generally the
higher capacity and longer warranties go with the more expensive brands. In most
cases they’ll be worth paying for – particularly in the case of a diesel where
cold-start current demand will be higher than for the same sized petrol engine.
Maintenance-free batteries will use lead-calcium for both grids, and this is
nowadays a widely sold type of battery. An alternative, sometimes cheaper type
is the "hybrid" lead-calcium/lead-antimony low maintenance batteries, or the
older style plain lead-antimony battery. There are good and bad examples of each
type, but in our tests the lead-calcium/lead-antimony battery performed better
overall than the others.
Having selected a make and type, look for the date of manufacture, or ask the
dealer to check it, if it’s not shown. Batteries don’t improve in storage. If a
calcium battery is more than a year old, or for other types say six months, look
for a newer one, or at least check that it has been recharged within the last
three months. And weigh the warranties. A three or four years’ warranty
indicates a greater degree of confidence on the part of the manufacturer.
Battery safety
A car battery is a very dangerous box of tricks. Most things can hurt you if you
do something wrong, but a battery has got more ways of damaging people than you
might expect. Don't go near them unless you know what you are doing and take
proper precautions.
Batteries can:
- Explode. Charging a battery releases hydrogen – this gas is explosive and the
slightest spark can cause the battery to explode, given the right mixture of gas
and air. Ventilate well.
- Burn. Metal jewellery, watchstraps, rings, hand tools or wires can get red hot
instantly if batteries short-circuit. Be very careful around the terminals, and
disconnect the earthed (negative) lead first. Note security codes before
disconnecting.
- Corrode. The sulphuric acid will severely injure eyes or any skin it contacts
with. Never tip or drain a battery; take great care to avoid contact with the
acid.
- Poison. Both the acid and the lead are toxic and a battery must be treated as
hazardous waste. Dispose only at an approved battery disposal site.
- Injure in lifting. They are heavy and often awkwardly positioned and difficult
to grip. Take great care lifting and putting down – dropping one is a serious
hazard.
- Damage the vehicle. Make sure the battery and the leads are never fitted the
wrong way round. Secure the battery properly, without over-tightening the
clamps.
If you ever need to jump-start a car, follow the instructions precisely – these
will normally be printed on the jump lead bag.
Conclusions
- Look after your battery, it’s important.
- Buy a good one. Get a lead-calcium/lead-antimony "hybrid" type, with a long
guarantee period, and make sure the capacity and cold-start current are right
for your car.
- Check its age when you are purchasing – we are calling for all car batteries
to be marked with the date of manufacture, and preferably a "sell-by" date.
- Take care near batteries.
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