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Bloody Car - Battery Help...


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On the way home yesterday I went to the petrol station, got back in the car and went to turn the key and all I got was a buzzing from a relay. Further inspection (after being jump started and going home) is that any switch (i.e hazzards) I press also buzzes which ever relay it uses, windscreen wipers are slow/stopping, car wont start, central locking etc. etc.

 

So I cleaned the battery connecters thinking it may be a bad contact (as I was able to be jumped ok) and still the same, checked the voltage on the battery and its at 14V :confused: now could the battery still be duff as the issue seems to be not enough power to turn over (hence the relays going bazzerk).

 

Any advice much appreciated(really don't fancy catching the bus to work again)

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Battery at 14V doesn't sound right at all, it's normally 12V max :huh:

 

Could something in the circuit be causing a surge anytime it's used/powered?

 

Maybe a fuse in your fusebox is 'half-gone' (not snapped enough to cut out outright, or with snapped ends close enough to arc)? I've had that happen to me years ago, and of course it took me donkey's to find the fault out.

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Battery at 14V doesn't sound right at all, it's normally 12V max :huh:

 

Could something in the circuit be causing a surge anytime it's used/powered?

 

Maybe a fuse in your fusebox is 'half-gone' (not snapped enough to cut out outright, or with snapped ends close enough to arc)? I've had that happen to me years ago, and of course it took me donkey's to find the fault out.

 

Will have a look later, gonna try another battery on there and see if that makes a difference.

 

Cheers

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For some reason 13.8v rings a bell. Is that the voltage when the car is running and charging?

 

No can only get it started with a jump, it was when it was off. I'm suspecting screwed battery as when it was running and I was at traffic lights my lights would flicker, so the alternator was doing all the powering, but as soon as it was switched off, it wouldnt start again, just sat there as if it was low power, slowly getting lower(lights slowly getting dimmer etc). But still had voltage accross the battery (must admit I didnt check the amps).

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A battery that is fully charged, with key off and no load on it should read from 12.4 to 13.2V in these sorts of temperatures. 12V indicates a very flat battery.

 

When charging 13.8V is the gassing point when the battery will start to evolve hydrogen and oxygen if it's a flooded cell one. Most cars will charge at somewhere around this - 14V or so.

 

If you are measureing the battery voltage with the engine off and you are getting 14V you have a stuffed voltmeter - it's simply not possible to get that sort of voltage. Find a new 9V battery from a smoke alarm or similar and measure that to see if if indicates between 9 and 10V as a check of the meter first.

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This is acopy and paste of an article I wrote for a car site... it may be of some help if a little long

 

Since there seems to be a lot of threads about dead/dying batteries in the cold weather I've hacked the guts out of one of my Focus Torque articles. I hope you enjoy a somewhat technical read but hope it will be useful to you and stop you getting stranded by the side of a cold snowy motorway somewhere.

 

The full article with a lot more info and details on checking a battery will appear in the next Focus Torque - so probably sometime in August at the rate articles get sumbitted.....Smile

 

Comments and suggestions welcome.

 

Winter Battery FAQ

 

What is it about winter and batteries? First sign of frost and cars fail to start left and right. Some kind of mystical magic? Well no - it's a fairly common issue and one that the motoring agencies are well aware of. Battery problems are responsible for something like a quarter of all breakdowns reported to the AA and RAC. Read on and you may avoid becoming a statistic...

 

How does a battery work?

 

Without wanting to get too deep into an explanation[1] a lead acid battery stores energy in the form of sulphuric acid. This is reacted with a pair of plates of lead - the positive plate is made of lead metal and the negative plate is made of lead oxide. As the battery flattens it converts the lead oxide to sulphate. By applying voltage to the battery you can reverse this and charge it back up again.

 

What's bad for a battery?

 

Heat and sulphation are the best ways to kill a battery. Heat causes excessive corrosion of the plates - remember they live in a tub of sulphuric acid and eventually corrode away. A battery fitted to a car in Florida lasts only half as long as one fitted to a car in Maine for example.

 

Sulphation occurs as a battery is flattened. If it stays flat for too long - just a few hours then the soft lead sulphate changes into crystalline lead sulphate. This crystalline form cannot be changed back into lead metal when it's charged. A sulphated battery will lose capacity and never recover it - the only safeguard is to fully charge the battery and keep it fully charged. Otherwise you will be able to store less power in the battery.

 

Sulphation from letting a battery go flat is the number one killer of car batteries.

 

Let's say it again - letting a lead acid go flat, by any amount will kill it within a few months. Always keep them fully charged and in use, otherwise charge them weekly with an automatic charger.

 

What does a battery do?

 

Car batteries are more properly known as SLI batteries - Starting, Lighting and Ignition. This reflects the things that a car battery is requied to do. Lighting and ignition are relatively easy to provide for. These won't be discussed further in this article.

 

Starting.

 

This demands a huge current and places a great strain on the battery. A petrol engine will take something like 250A to start - twenty times the current required by an electric fire. That's why the battery cables are so thick.

 

Diesels are even worse. They have to run glowplugs for a short period and then start an engine that demands even more current. A diesel needs something like twice as much current as the same sized petrol engine.

 

If you look at your battery you will find a set of four markings on most modern ones. You will have a type code, which specifies the battery size. Something like 063 or 042 will be common in a Focus - the first one is a diesel, the second a petrol size.

 

You will also have three other figures - a CCA value, a RC value and an Ah value.

 

CCA is Cold Cranking Amps and is the most important. It measures the maximum amount of current a fully charged battery can deliver at -18C (which is 0F). As batteries get colder, they can deliver less power. This is why batteries always seem to fail as winter comes around. They were tired and weak in summer but the warm air kept them going. A battery can deliver three and a half times as much current in the summer compared to a cold winters night.

 

The first sign of poor starting is usually a reluctance to crank and a greater variance on cranking speed. Your battery should always be able to turn the engine over smartly and should do so willingly - if it has to spin up to speed then there is something wrong.

 

If you have a clicking sound like a demented dwarf with a football rattle coming from the engine bay then you have a flat battery. The click is the start motor solenoid engaging, which then put such a load on the battery that the voltage collapses. The solenoid releases, the battery recovers and then it goes click again and the voltage collapses etc etc.

 

When buying a battery you must....

 

1. Get the right physical size and post connector - one of these sizes

2. Get one that is AT LEAST the same number of CCA. If yours is marked 400CCA then you want one from say 380CCA or higher.

3. Get one of about the same RC and Ah. If you had an RC of 75 and an Ah of 50, then you could go as low as RC of 65 and Ah 40 without real issues. If you have to choose between slightly low RC and Ah and a low CCA then pick the low RC and Ah.

 

So what to do?

 

Well there are a few things. The first is to realise that batteries are consumables - you have to buy new ones. Although they can go for a long time, a car battery is built to deliver current, and that makes them fragile. I'd replace any battery that is more than five years old - check the date punch on the top. This is especially true for diesels - a diesel typically will suddendly fail dramatically with little warning.

 

The second one is to look after it. If you have a flooded wet cell battery, with caps that unscrew you must check it regularly - at least every month. If the level is low, (look at the markings on the side of the case) then it must be topped up. You MUST NOT use tap water - the chlorine and copper ions in the water will kill any battery dead in a short period. Use battery topup water from a car spares place. The good news about flooded wet cells is that if you do maintain them they are among the most robust and long lived batteries, as well as the cheapest to buy.

 

Never let it go flat and stay flat. This leads to sulphation and will kill it. If it does go flat it must be charged on an appropriate three or hour stage automatic charger. Otherwise you will be buying a new battery. If you leave your car for more than a fortnight without using it, you should charge the battery on the car to stop it going slowly flat as well.

 

There is not a lot you can do about it getting hot. BMW and Volvo have for years relocated the batteries out of the hot engine bay and installed them under the rear seats, but that's not possible on smaller cars. It is possible to get an insulated jacket and the jacket for the Ford Ka should fit the petrol Focus batteries. If you have a diesel then the Mk1 and Mk2 Mondeo battery jacket should fit with a little scissor work. Why Ford don't provide a jacket for the Focus is beyond me.

 

Testing the battery.

 

To quickly test the battery you need to put the dashboard display into the test mode - search the forum for the instructions and then step through to the battery voltage mode. The display will read something like b12.5 indicating 12.5V

 

NOTE: for every 7C below 15C, you should subtract 0.1V from the readings below. So at 1C, you should subtract 0.2V from the numbers, at -6C take off 0.3V etc. This is necessarcery to allow for the temperature effect on the battery.

 

With a fully charged battery with ignition on, all lights off you should have at least 12.4V If not, fully charge the battery off the car and try again. If it still will not hold at 12.4V then the battery is probably past it's lifespan.

 

Start the car. Watch the voltage carefully. It should stay above 9.2V while the starter motor runs. If it doesn't then the battery has capacity issues and is likely to fail soon.

 

As soon as the car has started and the idle is steady, the voltage should climb to 12.0V (probably higher) If it doesn't do so within 30 seconds then that also indicates capacity problems, OR an alternator issue.

 

Increase revs to a fast idle - about 2000rpm. If the battery doesn't climb to at least 13.5V then there is probably an alternator issue and the battery is not charging properly.

 

If your battery fails any of the above tests, I recommend you get it tested at an auto spares shop. Ask them to do a charge test and a heavy discharge test.

 

Buying a new one.

 

Batteries come in all shapes and sizes. The Mk1/1.5 Focus have the same tray for the petrols and diesels and you can install a diesel battery into a petrol Focus. This gives you more starting capacity which means the battery is stressed less and will last longer.

 

As well as getting the right size you need the right chemistry. Basic batteries are wet cell lead/lead chemistry, sometimes called lead antimony or Pb/Sb or sometimes Sb/Sb.

 

Maintenance free batteries cannot be filled with water, and are often called Low maintenance or lead/calcium or Pb/Ca or Sb/Ca. If you totally flatten one of these you may never get it to recharge. They are nearly as good as the wet cells and never need topping up. You can swap a wet cell for a low maintenance one without problems if it is not a calcium variant.

 

Newer batteries on the market are the maintenance free Silver Calcium cells. (Ag/Ca or Ag/Sb or Ag/Pb) These use small quantities of silver and calcium metal to increase battery life by resisting corrosion and almost all parts places will try and sell you one of these instead (because they cost more money of course....). Don't. Unless you already have one in the car and it was factory fitted, OR dealer fitted when your original battery failed, then DON'T. The charge voltages are a little different and you will not correctly charge the new battery with the result it will fail significantly faster.

 

And remember - when buying a battery remember that only rich fools can afford to buy a cheap battery. Cheap batteries fail early - get a quality name and pay the extra. Chloride, Exide, Varta, Bosch, SonnSchein (European) and Yuasa are all good names to get. Ford's Motorcraft range is also a good choice as is the Black Battery that Halfords sell. (but beware salesmen especially trying to upsell in Halfords - they have explicit instructions to try and foist a Silver Calcium cell onto you. Resist!)

 

Battery safety

 

When working around batteries there are certain safety issues.

 

Wear goggles at all times. Opthalmic hospitals see tens to hundreds of acid burn injuries a year - if it can happen to them it can happen to you.

 

Acid - all batteries contain sulphuric acid that in a charged battery can blind you. If you get acid splashed in the eyes flush IMMEDIATELY with copious quantities of water holding the eyelids open. In the absence of water any drinkable liquid such as milk will suffice. SECONDS count in terms of saving eyesight - DO NOT call for an ambulance first - administer first aid and then dial 999/112. Continue flushing if possible until the 999/112 operator directs you otherwise.

 

Batteries must stand upright or they will leak acid with the exception of AGM and gel cel batteries.

 

Explosion - All but AGM or gelcel VRLA will generate hydrogen gas in normal use. A spark from shorting a terminal out, cigarettes etc can cause a battery to detonate. The explosion is not high, but it flings hot acid everywhere. For this reason batteries inside the passenger compartment/luggage space must not be of the types that can evolve gas.

 

Short circuit. A shorted battery can deliver thousands of amps which will melt spanners, watchstraps, rings etc. Always dicsonnect the battery terminals and remove jewellery when working on a car electric system.

 

Charge voltages

 

The typical charge regime for a battery is a charge to about 75% full which is the bulk phase, then a 25% charge to fully charged whcih is the absorption phase. After this float charging is used to prevent discharge.Car alternators are designed to run absorption charge only as they cannot deliver the current needed for bulk charging. The charge voltages for absorption and float charging are listed below.

 

Sb/Sb 14.5V 13.15V

Sb/Ca 16.4V 13.1V

Ag/Ca none VRLA 16.0V 13.1V

Ag/Ca VRLA 14.9V 13.6V

GelCel 14.1V 13.2V

 

Note the wide difference in voltage ranges for these typical chemistries.

 

Typically to charge a calcium battery to 95% which is what car electrical systems aim for, you want 14.8 to 15.1V - the target of 16.4V blows the bulbs and only gives an extra 5% capacity.

 

If you were to replace a Ca/Ca calcium battery with a normal wet cell Sb/Sb then ti will fully charge and gas hydrogen like crazy as it overcharged. On a hot day it may even boil the electrolyte and you will get hot acid coming out the overflow caps.

 

Conversly if you replace a standard wet cell battery which is normally charged at about 14V with a calcium it will never charge fully and the battery will die early from sulphation as it will never get more than about 60% charged. I've reworked the regulator on three of my relatives cars after they were stranded on a cold Monday morning after the car had been fitted with a maintenance free battery the week before. 48 hours of sitting slowly discharging through the alarm and clock had dropped the battery so low they wouldn't start.

 

Gel cel and some AGM systems use lower voltages than this - 13.9V. These will never charge even a wet cell system - that 0.1V is crucial. Put a gel cel battery on a system that expects a Ca/Ca though, and the 15V could explode a gelcel with ease. Fortunatly there is not much free acid in these but it's not a good place to experiment.

 

[1] For the chemists the cell half reactions are below.

 

Anode Pb(s) + SO4 <-> PbSO4 + 2e e=0.356V

Cathode Pb(IV)O2 + SO4 + 2e <-> PbSO4 + 2 H2O e=1.684V

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I had the same problem on a motorcycle - turned out to be the rectifier / regulator.

Wonder if it could be the same thing ?

 

Can be. Usually the regulator pack fails and gets hot as the battery discharges through it - that's an easy way to find it. Otherwise you need a current meter to find usually.

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Thanks for all the replys, bought a new battery and it seems to be running fine, there does not seem to be any ground leaks, if its flat by the morning or in a few days then I know its more serious but its running for now.

 

Many Thanks

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