The Little Green indicator thing on some batteries

stephennoble

stephennoble

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One of the batteries on my boat is a leisure battery (I dont know exact specification) of 70AH. On the top is a clear plastic sight which from past experience shows green to indicate (may I assume) all is good to go. I am interested in what it does? Also I have just taken the battery off the boat and checked the water level, the water was just about at the level of the electrodes and below the little plastic indicator bar. The Little Green thingie was green. Once I had topped up the water the Little Green thingie went black. The battery has been on a slow 2A charge now for 12 hours. Thats all the information I have and any incite into the world of batteries would be interesting. :encouragement:
 
stephennoble said:
One of the batteries on my boat is a leisure battery (I dont know exact specification) of 70AH. On the top is a clear plastic sight which from past experience shows green to indicate (may I assume) all is good to go. I am interested in what it does? Also I have just taken the battery off the boat and checked the water level, the water was just about at the level of the electrodes and below the little plastic indicator bar. The Little Green thingie was green. Once I had topped up the water the Little Green thingie went black. The battery has been on a slow 2A charge now for 12 hours. Thats all the information I have and any incite into the world of batteries would be interesting. :encouragement:
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Some varaition in the way these "Magic eye" things work. Best to check for your particular battery brand

Generally green is Ok. Electrolyte level Ok and charged.

Yours is probably showing black because the top up water has not mixed with the acid yet and that's the indication for " not fully charged"

Charge it at a decent rate and you should find it will go green eventually.


Pretty useless gimmick anyway esp since they only look at one cell.

IMHO best ignored.

Check the electrolyte level in the classic way and top up if/ when necessary.

Monitor state of charge with a hydrometer or by rested open circuit volts.
 
Last edited:
stephennoble said:
One of the batteries on my boat is a leisure battery (I dont know exact specification) of 70AH. On the top is a clear plastic sight which from past experience shows green to indicate (may I assume) all is good to go. I am interested in what it does? Also I have just taken the battery off the boat and checked the water level, the water was just about at the level of the electrodes and below the little plastic indicator bar. The Little Green thingie was green. Once I had topped up the water the Little Green thingie went black. The battery has been on a slow 2A charge now for 12 hours. Thats all the information I have and any incite into the world of batteries would be interesting. :encouragement:
Click to expand...

It needs a lot more than 2amps to charge it. You need it to get to the gassing level and then the black will change to Green.
 
I am not an expert but I thought only maintenance free batteries had the "Green windows". However, you may have topped up with too much water and covered the "flag" inside. If you are very careful you could suck out the water with your hydrometer to lower the level and see if you can then see the green flag on the one cell. Be careful of sparks if you have been charging as there will be hydrogen gas around.
 
Big John said:
I am not an expert but I thought only maintenance free batteries had the "Green windows". However, you may have topped up with too much water and covered the "flag" inside. If you are very careful you could suck out the water with your hydrometer to lower the level and see if you can then see the green flag on the one cell. Be careful of sparks if you have been charging as there will be hydrogen gas around.
Click to expand...

There are several batteries with the green window and some are not sealed and so can be topped up.
 
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