Car battery question

I have been topping up my oil and had a look at my battery. On the top of the battery there are 4 circles with crosses in them like you could use a philips screwdriver to open them. Could anyone tell me whats under them and if they should be tampered with.

I'm getting into looking after my car and simple maintenance, as it all started to interest me. I now have to time to have a go a things I normally wouldn't have.

Thank you

Reply to
Tishtash
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A battery is a plastic box full of acid with plates in it. The circles provide access to the inside of the box. If you undo them and turn the battery upside-down you could pour the acid out. There's no good reason to do that though.

You can top up the battery through the holes, not with acid but with distilled water. I can't remember when I last did that though, I don't think it's really necessary. But car parts shops do sell the bottles of water (called "battery top up water").

I once partically rejuvenated a very old and neglected battery by pouring out the acid (which is pretty much just water if the battery is flat) and putting in some new sulphuric acid of the right concentration. But better to just get a new battery from Halfords.

Reply to
Ben C

"Tishtash" wrote

Are you sure there are not six?

What you are describing sounds like the caps to the cells, which contain the battery plates.

These are made of lead dioxide (positive) and lead (negative). The cells also contain an electrolyte H2SO4 (sulphuric acid) diluted with water.

By all means remove a cap and have a look (a penny piece is best for doing this) but keep the electrolyte off of skin and clothes.

Reply to
Knight Of The Road

There will also be 6 caps.

Reply to
Ian Stirling

Yeah, especially if you have a paper cut on your finger!

Reply to
redwood

Please remind me - which is the explosive situation - adding sulphuric acid to water or water to sulphuric acid? LOL

Reply to
Hooch

My mistake there are infact 6, just took a quick look. I going to go and undo the cas and have a look and see if any distilled water is needed. I have never topped up any of my batterys before and nothing has ever happened. Feeling a bit doubtful of tinkering with it. Like my dad said if it ain't broke then .... but when has that ever stopped curiosity :)

Reply to
Tishtash

Good luck, I think the acid is supposed to come to the level of the top of the plates.

Reply to
Ben C

"Tishtash" wrote

I

You shouldn't need to, a modern battery is maintenance-free and you will risk damaging it if you over-fill it. The electrolyte should just cover the plates but no more. Normally if a cell goes "dry" it means the battery has expired.

Reply to
Knight Of The Road

What a responsible, sensible, and great idea! Frankly I consider it a life skill mandatory in owner a car. I would start reading the Owner's Handbook (that comes with the car normally, if that is not lost!) as a first step. If you want more and wonder why things are done as they are, you'll need a little more thorough treatment, not specifically for your car (which may be too limiting) but good enough for whatever model you may change into in future. This short title is reasonably comprehensive, readable, and as good as many. I've found it useful:

"Haynes Glovebox Guide: Your Car"

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Servicing and maintaining the batteries are all there, of course. I wish you good luck in the pursuit of this new interest. And, don't forget to post your query here if you have any difficulty!

Reply to
Lin Chung

Car batteries are low-maintenance (or zero-maintenance) these days. Other than being kept fully charged, the only maintenance required is to keep the electrolyte (sulphuric acid) topped up.

Some batteries lose electrolyte fairly fast, usually as a result of the charging voltage being set on the high side. I check the level annually, and top up with distilled water if necessary (the acid itself doesn't deplete - just the water base).

If the battery has a clear plastic case, you should be able to see that the electrolyte level (in each of the 6 cells) is between the low and high marks painted on the case. You may need to rock the car firmly to make the electrolyte move in order to see the level.

If the case isn't clear, you carefully remove the plugs and have a look down the hole. There should be a plastic tube with slits in the sides ending at about where the electrolyte level is. If you can see a grid of grey/brown plates high and dry above the liquid electrolyte, then you definitely need to add distilled water (not acid).

If you need to top-up the battery, you should add water until the electrolyte just reaches the tube. You can see fairly easily when this happens because you should see the flat top of the liquid suddenly change to a curved, concave meniscus when it gets there. If in doubt, underfill rather than overfill, but make sure the tops of the plates are covered.

The electrolyte is very corrosive to metal, clothes and skin - even small droplets which might splash up. Eyes are especially vulnerable, so wearing eye protection is recommended.

Wait a half-hour or so after charging (or running the car) before removing those plugs because there can be an explosive mixture of hydrogen and oxygen inside, just waiting for a spark. The caps themselves have flame suppressors. Every year there are a few hospital admissions with severe physical and chemical eye damage from exploding car batteries.

John

Reply to
John Henderson

been thier , blast injuries are real painful

Reply to
Steve Robinson

From all the different threads on the subject recently, I've found it very interesting to understand exactly what a specialised component a car battery actually is.

I wasn't previously aware that it's designed to deliver a surge only, not a constant current.

As an electrician (not automobile) can anyone tell me roughly the peak current it takes to start a car engine?

Thanks

Reply to
John Burke

John Burke expressed precisely :

Perhaps 600amps peak, at 12v.

Reply to
Harry Bloomfield

It will vary enormously with temperature, size of engine, number of cylinders, type of lubricant, petrol or diesel etc.

It can be several hundreds of Amps.

Chris

Reply to
Chris Whelan

It does both, you can optimise for one or the other.

Depends on the vehicle, 100A-800A for most cars.

Reply to
Duncan Wood

Gawd, that's a monster.

Thanks.

Reply to
John Burke

I think you'll find it much less than that. Nearer 300 than 600 amps. AFAIA most car batteries are incapable of supplying 600amps. Mike.

Reply to
Mike G

Mike G expressed precisely :

Easy confirmation of the figure is to be had by checking the specified cranking current for your own battery, most modern battery specs. mention this figure these days. My own car spec requires a 725 amp.

Reply to
Harry Bloomfield

A car battery is designed to deliver a short burst of energy, then be quickly fully recharged. Its secondary purpose is to make up the current short fall when you sit ticking over in traffic with everything turned on and off course allow you to leave parking lights on for a short while.

Traction and leisure batteries are designed to discharge almost completely before they are recharged, but even so such use limits their working life.

Reply to
Harry Bloomfield

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