Re: solar 12v battery chargers
 

You can get short circuits between the plates from deposits or by the plates buckling from overcharging/overstress. This reduces the battery voltage.

I would not recommend cutting a car battery open unless you want to be covered in acid ;)

Re: solar 12v battery chargers
 

I empty'd the acid out first. I made my fiirst lead acid battery when I was about 17, got the acid and the different lead oxides from America Eccles up Ossy, carved the mould to cast the lead plates into a piece of oak, 90% lead 8% antimony & 2% tin. Used cedar wood for the separators, got 6 volts from 3 cells. Made each cell from 1/4" pespex.

Retlaw.

Re: solar 12v battery chargers
 

It does sound like the battery needs replacing if it goes flat because it's been stood for a while.

Solar chargers are a bit useless in this country, what you need is a wind generator :D

I'm sure I read that bump starting is not good for modern engines because of all the hi techy stuff in them.

BTW, it's an ammeter, not a voltmeter that needs using to test if current is being drained ;)

Re: solar 12v battery chargers
 

Thats if your testing the battery whilst it is still connected to the car electrics. My suggestion was to disconnect the + terminal and connect a voltmeter between the + terminal and the + battery post, that will show if there anything using juice when the ignition is off.

Retlaw.

Re: solar 12v battery chargers
 

Unless there is a fault somewhere else pulling current - that's where the ammeter comes in.

Re: solar 12v battery chargers
 

An ammeter shows current, and is not sensitive enough for small drains on the battery over a long period, whilst doing what I suggested, will give an instant reading on any juice being used that should'nt be.

I use both a voltmeter and ammeter to check if the alternator is working as it should, the output from the alternator should be around 13 to 13.5 volts, amps will depend on the regulator.

Retlaw.

Re: solar 12v battery chargers
 

Yes and to determine if juice is being used, you need to use an "ammeter".
It measures amps/current.

Whereas a Voltmeter is used to measure voltage and they do not like it when you try and draw current through them.

A Multimeter would have both functions on.

Sorry to be pedantic about which instrument is used but it's best not to risk damaging one. :D

Re: solar 12v battery chargers
 

That just goes to show how a little bit of knowledge does more harm than good, I said nothing whilst you wrongly suggested a volt meter should be connected as an Ammeter,

I cringed then said nothing while you mentioned cutting a lead acid cell open, (with or without acid still in there, residue will remain),

But to state that an ammeter isn't sensitive enough, Oh, please stop while I can remain polite, what do you suppose we, the professionals use to measure micro & milli-amps?

Please, Please, check your advice as much as you might believe it to be true, before you hurt somebody!

:(

Re: solar 12v battery chargers
 

Thank you Less. :D

Re: solar 12v battery chargers
 

Welcome.

Re: solar 12v battery chargers
 

Thanks less, I do know about milli & micro amps, mostly found in radio & television circuits, might be some used on the newer cars in the fancy circuit board they install these days, the reason I use a volt meter to test in the way I suggested, you can expect 12 volts on a car battery, but how the eck do you know what amps to expect, can be anything up to 60 odd amps and what use is your milliamp meter then, could end up with a fried meter, my biggest meter will only measure up to 10 amps.

As to cutting open car batteries, whats wrong with that, I've cut open several in the past, for the metal inside, it contains on average 12% antimony, I then mixed it with lead and 2% tin to make hardened bullets, of which I've shot many 1000's, in both rifle & pistol calibres.
And I've got the competition medals to prove it.

Retlaw.

Re: solar 12v battery chargers
 

Posted via Mobile Device
Btw an alternator should put out 14 to 14.5 volts not 13

Re: solar 12v battery chargers
 

Agreed Ian, but as the battery nears its capacity, the regulator turns the output down, if the battery is nearly full, then the voltage will drop to arround 13 volts, on a flat battery I've seen the meter hovering near the 14.8 volt mark, its the voltage that overcomes the battery's initial resistance.

Retlaw.

Re: solar 12v battery chargers
 

Not on most cars is does not. Only on stupidly expensive alternators like on mine with external "smart charge" (read expensive, I know I changed it a few weeks back because the slip rings had worn away :( ) controllers that might do that.

The voltage regulator on a car alternator tries to maintain a constant 14 - 14.5 Volts. In fact when the battery is low and you are pulling heavy current from lights, heated windows etc and the car is only at low revs you will find the voltage lower that it should be.

When the battery is fully charged the alternator will still maintain the same 14 to 14.5v. Stick your voltmeter on and see.