Charged?

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mick

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My 85ah service battery has a little cell which shows green when the battery is charged. The cell is not showing green at the moment even though I have charged the battery and the cells read fine when checked with an electrolyte tester. The battery is 4 years old. Should I replace it?
 
Some people like hydrometers but personally I prefer a digital voltmeter (multimeter)
Let it rest for 24hours after charging and then measure the volts. If it is 12.7 or more it's fully charged. Then check it over a period of days and weeks. It will fall fairly quickly at first and then more slowly but a good battery will still show at least 12.6 after a month and 12.55 after two months.

I guess that a four year old one will naturally fall a bit short of those figures but a reading of 12.5 is always going to be OK especially for a domestic battery. 12.2 is about half charged and 11.7 effectively flat.

The important thing probably about your hydrometer readings is that all 6 cells read the same. If one is lower than the others or falls more quickly than the others then it a bad omen.

If money no object replace it for peace of mind but otherwise keep it for another season but check it again in the spring as sometimes batteries can fail quite suddenly. I've had them perfectly OK one day and as dead as a dodo the next! So no amount of testing is fool proof.
 
Buy a replacement and keep it on board (if you have the space). When your old battery starts to fail swap them over. Always good to have a fully charged spare around in case of an emergency.
 
Those little green cells are a waste of time. Take no notice of it. If your battery shows a heathy voltage after resting from charge it is probably OK. Vic's figures above are a good guide...
 
[ QUOTE ]
Always good to have a fully charged spare around in case of an emergency.

[/ QUOTE ] But you must remember to charge it regularly or you will be throwing money away.
If you are going to keep a extra battery onboard it must be securely fixed somewhere safe so it might as well be integrated into the system as a second domestic battery which will be charged automatically.
 
The 'little green eye' works by floating a green pill into view when the electrolyte density has been increased by adequate charging. If the voltage shows the battery (strictly speaking the cell containing the green eye) is well charged but the eye is not green, wait a while and if you can, move the battery around enough to slosh the liquid around. Sometimes the eye is slow to respond to re-charge. If it does not show green after a day, or perhaps two, the reason is the liquid level is down below the bottom of the green eye device: for one of two reasons; either the case is leaking, or the electrolyte has been lost by gassing. If that is so, the battery has been consistently overcharged and/or charged at too high a voltage.
This battery is on its way out, and unless you tackle the over-charging/over-voltage problem, the next battery will soon follow it.
I am no expert on batteries or charging systems: it has been experience, good and bad, that has been a great teacher!
 
[ QUOTE ]
The 'little green eye' works by floating a green pill into view when the electrolyte density has been increased by adequate charging

[/ QUOTE ] I wondered how it worked but I guess it is pretty obvious once you know. The one in swmbo's new car is the first I have come across.

Only works on one cell which is a bit of a disadvantage but as you say if the electrolye has fallen a bit it wont work at all.

Once batteries get towards the end of their lives they seem need topping up even if the charging it properly regulated so it may indicate that it's life is now limited. I'd still charge it and monitor it to see if I could get another season out of it though.
 
Top it up...

Batteries with the green "magic eye" device are usually sealed, maintenance-free types. However, if you can access the electrolyte for testing, why not just top it up? The most likely reason for the green indicator not showing is that the electrolyte level has dropped a bit.

As an aside, my domestic bank uses sealed, maintenance-free batteries with "magic eye" indicators. A few years ago, the batteries stopped showing green even when fully charged. Concerned that the electrolyte might be very low (as charging is usually at higher voltages controlled by an Adverc regulator), I cut a hole in one to see how much electrolyte was left. To my surprise, there was plenty of electrolyte covering the plates - these sealed batteries generally seem to have a good reserve of electrolyte. The batteries are now 8 or 9 years old and just starting to lose capacity.
 
Re: Top it up...

I agree you should stop looking at the little green eye. A battery is fully charged when you know you have put something in the order of the rated AH capacity into it over a reasonable period of time. Make sure if you can there is enough electrolyte.

The battery is dead when it will not do the job you want it to do. ie provide a reasonable amount of power to your services for a reasobale time and will also start your engine if needed in an emergency.
If it will do those things it is fine. After all with back up battery sytem surely it would not be a disaster if the battery dropped dead. People don't seem to worry about there car battery until it drops dead and there is no back up.
A spare battery? No it will just start to get old as soon as you buy it so wait till you need it.
olewill
 
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