Gavin,
You said last week that your car battery has lasted nine years! I suspect even half that long would be a miracle for many motorists. What makes a battery die sooner or live longer? Is there a secret?
Anon.
No secret, but plenty of robust science. Most cars still use old-fashioned lead-acid batteries, which are nowhere near the best design by any measure (weight, size, capacity, charging speed, reliability, longevity)…except one:
Even with just 12 volts, they can “discharge” a tsunami of amps like no other, and that is exactly what cars need to get started. A car’s starter motor has to turn all the moving parts of an engine and a heavy flywheel (which weighs plenty) – against friction and often gloopy oil – from stationary to a high speed rotation in a second or two.
That demands a huge “draw” of electricity. Say, 300 amps – enough to melt metal and drain a 50 ampere-hour battery from full to flat in six minutes!
Other “affordable” types of battery which are superior in every other respect cannot do that.
The moment an engine does fire up, the battery is out of business as the alternator is now being turned by the engine and is generating all the electricity the car needs…and recharging the battery, too.
The lead acid battery can go through this discharge and recharge cycle many thousands of times, indeed almost indefinitely because it works using what is known as a “reversible chemical reaction”.
Fully charged, it contains plates (like thin slices of bread with gaps between them) made of pure lead, completely submerged in electrolyte (a mixture of water and acid).
When electrical power is demanded, the acid reacts with the pure lead and starts to form lead sulphate, and the electrolyte becomes more dilute. This reaction is what generates electricity, and the battery is “flat” when the plates are almost completely lead sulphate and the electrolyte is almost pure water. The potential to generate more has gone.
But, by reversing the flow of electricity from demand to supply (charging the battery), the chemical process reverses. The acid leaves the plates and re-joins the water, returning to pure lead plates and the right mix of acid and water for the electrolyte when the battery is fully recharged. Ready to start the process all over again.
Three things can change that from an “everlastingly reversible process” into progressive battery ageing and failure:
Heat and/or Chemical Change and/or Structural Damage. Knowing what causes those, and avoiding them, is what makes batteries last longer.
1. Heat
Car batteries can cope with some heat, after all, any chemical reaction creates heat and batteries have to live in hot engine compartment.
Even the extreme chemical reaction caused by the starting download is usually brief and the heat is quickly dissipated. But prolonged cranking of the engine without pause during hard starting is another matter. That can generate enough heat to buckle the lead plates and cause them to touch each other, creating a short, which generates even more heat. That will quickly damage and destroy a battery.
Excessive heat is also caused by excessive load, for instance if the starter motor is jamming or by recharging too rapidly or too much (say if the car’s or the charger’s voltage regulator is faulty).
Loose or fouled connections at the battery terminals also generate heat and/or allow the battery to “leak” discharge even when not in use. This is made worse if the outside of the battery casing is dirty – wipe it clean regularly, especially near the terminals.
2. Chemical Change
There is a very precise balance between the amount of lead and the quantity and strength of electrolyte for the “reversible chemical reaction” to continue indefinitely.
Things that can upset that balance are evaporation of the water in the electrolyte (that should be regularly replaced by topping up with distilled water), allowing the electrolyte level to drop too low (leaving the top of the lead plates to oxidise in the air instead of being completely submerged), any impurities in the water used for topping up (distilled water only (!) should be used, even the cleanest drinking water will damage the balance), failing to fully recharge the battery for an extended period (some of the residual acid in the lead will become “fixed” and the plates will be permanently sulphated to some extent), and too often and for too long running the battery at a very low level of charge (for instance a faulty alternator) which also causes some permanent sulphation.
If a battery will remain unused for more than a week, it should be fully charged and disconnected from the terminals to avoid electrical leakage that will discharge the battery and cause permanent sulphation.
Fit a battery of the correct capacity for your engine.
3. Structural damage
This can be external, for instance damage to the casing from rough treatment when fitting terminals to the battery posts (never use a hammer!), or overtightening the battery clamp, causing distortion (which can misalign the lead plates inside) or cause cracks, which allow electrolyte to seep out.
Or it can be internal – from the constant bumping and shaking on rough roads in general use (even worse if the battery clamp is too loose and allows the box to bounce) which can cause the plates to come loose and either spill fragments of lead into the bottom of the box (eventually causing a short circuit between plates) or displace a plate so it touches another or no longer contributes to the circuitry and capacity (dead cell) of the battery.
Finally…
Fit a battery of the correct capacity for your engine. A 50AH battery might be able to start an engine designed for a 70AH battery, but it will work too hard and fail sooner.
Fitting twin batteries has the opposite effect – both have an easier life. They can last more than twice as long and you have back-up if one fails. Lead acid batteries will last longer if kept as fully charged as possible, and are never allowed to fall below half-charge (don’t keep trying to start until a battery is completely flat). Find and fix the starting fault…or ask for a push.
What’s your definition of a fuel-guzzler?
Hello Gavin,
From a general point of view, how can one tell if a car is a fuel guzzler? The car size? The engine cc? If so, what engine size do guzzlers start from? Are all SUVs fuel guzzlers? Thanks.
Muriuki G
The dictionary defines gas guzzlers as “large cars with high fuel consumption”. What does ‘large’ mean? What does ‘high’ mean?
Clearly, the term is not specific. The description is emotive and usually scornful, but is it not an objective measure between those vehicles which are “guilty” and those which are not? GG doesn’t even have the catch-all merit of something like BMI (Body Mass Index) which is used to determine whether a person is fat or thin.
That measure can create lots of anomalies and be unduly judgmental, but it is at least a specific number and it is based on solid science.
A better definition of gas guzzler should perhaps be “any vehicle which consumes much more fuel than necessary for the job it is generally used to do.”
That way it is not just the size of the car body or the cc of its engine that makes a particular model a paragon of virtue or a disgraceful indulgence.
A big 4WD estate which is used predominantly or just quite frequently to carry several passengers and lots of luggage/equipment in off-road conditions will need a big engine to do that job. It will certainly “guzzle” fuel and therefore be at the current dictionary’s mercy, but it might not deserve the social opprobrium that gas guzzler can imply.
A smaller and more fuel-frugal vehicle simply could not do the job properly…nor pull a horsebox or a big speedboat nor rush several people to hospital nor carry enough water to save a house from burning down or enough equipment to be a field service workshop
But the same big 4WDs used predominantly (even exclusively) on tarmac trips and for tasks which smaller, lighter and more fuel economical cars could do just as well suggests the wallet and the self-image of the owners has over-ridden rational economy or anything David Attenborough or Greta Thunberg have to say. Gas Guzzlers that fall into that category should perhaps be Christened “Gloaty McGloatface”.
What could be happening to my car at the carwash?
Gavin,
Nowadays after I take my car to the carwash, the doors thereafter indicate unlocked on the dashboard although physically they are locked… meaning I cannot use my remote to lock the car. What could be the problem? Also, the dashboard shows the handbrake is engaged even if I’m driving and I have not engaged it.
Kindly advice. Anon.
If any electrical problem arises immediately after a carwash, the prime suspect must be water… getting into places where it does not belong, in this case among the electrical on/off contacts that trigger or disconnect warning lights. If the problem “goes away” when errant spills have had a chance to self-dry, that would confirm the diagnosis.
The electronic and computerised gadgetry on modern cars gathers information from all over the vehicle, but that data is usually processed quite centrally, in sealed boxes high up and well inside the car, where water is most unlikely to reach. An auto electrician will know where the contacts and processors are likely to be, and/or how to find them. The odds are that a sharp “phwooo” (that’s a blow of breath) or a dry cloth will cure the problem…this time. A hair-drier might be a bit OTT but effective in hard-to-reach places.
The handbrake light is probably suffering from the same malaise. There is also a possibility that it is binding to some extent, and while the lever operates normally, it is not fully releasing the cable or hydraulic link all the way to the rear wheels. Check the temperature of your rear wheel rims to be sure.
If your valet uses a pressure washer, a word about where not to saturate in future might help prevent recurrence.
Dust and dirt can also cause a similar problem, but usually the other way around, by falsely breaking rather than falsely making electrical contact. Other possibilities depend on how sophisticated your car’s drive-by-wire systems are, and which ones react when something irrationally turns on or off
Your example illustrates a dilemma of modern motor technology. Computerisation of virtually every function of cars has hugely improved efficiency and economy, performance, comfort and convenience and has also given us a whole raft of additional information perks.
Today’s car dashboards make the Nasa Space Centre used for the first moon-shot look primitive. Hyper high tech is brilliant, and drivers might have enough multi-tasking eyesight and brain-space to use and even enjoy the results when cruising along smooth and orderly highways. Not so good if you are on hair-trigger alert for ambush speed bumps and potholes while dodging donkey carts and untrained and unchained motorcyclists, nor if your motoring involves frequent pummeling from rock-and-roll road surfaces and dousings of lava dust or fording floods and rivers.
Car computers are now remarkably reliable, but being additional to the basic mechanical functions they manage, they do constitute another thing that can (and sometimes does) go wrong. Of course, old-fashioned mechanical controls can also fail, but with those you have a better chance of knowing what they are, where they are, and being able to fix them…somehow.
The car I use for rough safaris in remote places was selected for a number of attributes. Prime among them was that it has zero computerised gizmos.
So count your blessings that your problem has only upset a warning light, and you can still start, stop, turn and get in and out with a key. Some unfixable computer glitches are less forgiving, and then the only tool of any use is a mobile phone – to get you towed to a safe place, and to get a replacement part sourced, paid for and delivered to wherever you are. BY DAILY NATION