Battery indicator

The cynic in me suggests that that's exactly what they want you to do. I thought deep discharge was a good way of knackering batteries but probably not immediately. I know that they shouldn't be left deeply discharged for very long as that will knacker them.

-- Malc

I agree. It does sound a bit fatalistic. I can only imagine it means "if you have charged your battery and still get the following readings, then . . . "

Rob Graham

Robin is right. Normally on sealed "Maintenance Free" batteries, "built-in" hyrometers or "magic eyes" are designed to indicate a charge abouve 65%, a requirment for a recharge, and battery replacement because the electrolyte level is too low in that cell.

For more information on these hydrometers, please see Section 4.4 in the FAQ on

You can also use an accurate digital voltmeter to determine the State-of-Charge of a sealed battery after the surface charge has been removed.

Kindest regards,

BiLL........

Don't you just love 'maintenance free' things where you replace them rather than add a pennies worth of water...

At £85/hr, plus VAT ? Probably cheaper to buy a new battery...

[I have in my time used extreme violence to get through the top of a "sealed" battery in order to top it up - 24 months from new and the plates were already exposed.]

Heh heh - if you saw the prices BMW charge for supplying and fitting a new battery, a new car might be cheaper...

I had the misfortune to have allow them to supply one because of an alternator fault which required the car being towed to them. They charged for checking the old one, charging and supplying acid for the new one, and fitting. All in all, about 4 times the price of a top of the range from Halfords. And I'm pretty certain the old one was fine - it had showed no signs of problems before the alternator died. Nor could they give me the old one back so I could check it, despite being told to do so on the phone.

Since, as a low maintenance type it must have vents, it strikes me as sharp practice not making it possible to check the level.

I can imagine. A friend has a new Merc. He decided to have mud-flaps fitted - £20 or so each. Plus £180-odd for fitting !

He has also discovered that a local outfit who fit parking sensors are in fact subcontracted by MB to do exactly the same. Except MB want twice as much for the privilege.

In article , Bill Darden writes

What are these types of battery called? My van has one and I'd like to get a similar one for my car which needs a new battery. There is only the one pilot light for the battery is there a battery with a magic eye for each cell?

I've seen a battery capacity tester in the IEE magazine and I think Electrical Contractors News (ECN) which gives an Ah reading for 12V batteries. One would be handy if it also gave readings for 1.2, 1.5

3,6,9,12 and 24V batteries.

Delphi is the largest manufacturer of the SLI (Starting, Ignition and Lighting) car battery types known in the battery industry as "Maintenance Free". Please see Section 7.1.3 in the FAQ on

for more specific information about this plate chemistry (battery type).

I am not aware of a Maintenance Free battery with more than one built-in hydrometer, because of the increased manufacturing costs.

Kindest regards,

BiLL........

Strictly speaking, low maintenance types. They employ special techniques to condense electrolyte vapour back into the battery rather than just venting it to the atmosphere, as traditional types do. However, some can still be topped up with distilled water if needed, so go for this type if possible.

Those I've seen only have the one indicator.

A 1.2 volt cell won't be a lead acid, so would require different testing techniques.

I've seen these 'computer' car battery testers that don't use a continuous high discharge for testing - judging by the size of the cable. Perhaps they use a pulse method? Anyone know? And what's the cost?