Battery Charge

Cedric · Mar 21, 2012

Which is the more accurate method of determining the state of charge of a battery - using a hydrometer or a volt meter across the terminals.

I have just bought a new battery and before installing decided to check if it was fully charged. Readings from two different hydrometers showed that it was only half charged. Took it back to the supplier for them to check. They put a volt meter across the terminals and got a reading of 6.2 volts and said that the battery was fully charged. I am not convinced.

Your comments will be much appreciated.

Sid.

gene bender · Mar 21, 2012

Sure it read 6.2 but there was not very much cranking power the hydrometer is the sure way to know if its fully charged.

El Toro · Mar 21, 2012

Your specific gravity should be in the 1.260-1.280 range if it's fully charged. Put your battery charger on it over night to see if the readings rise. Hal

Indiana Ken · Mar 21, 2012

There are various charts showing the battery voltmeter readings versus state of charge. I have one taped to the back of my voltmeter. The reading will vary based on the type of battery. The following example is from a Yuasa catalog and is what I use - for 6 volt batterys simply divide by two.

Battery Type: State of Charge - Voltmeter reading

Maintenance free: 100% = 13.0 volt : 75% = 12.8 volt : 50% = 12.5 volt
Lead antimony: 100% = 12.7 volt : 75% = 12.5 volt : 50% = 12.2 volt
Lead calcium: 100% = 12.6 volt : 75% = 12.4 volt : 50% = 12.1 volt

The problem with the voltage measurement is that one needs to know the battery type. Conversely, many modern batterys do not have removeable caps to allow checking the gravity.

Typically I find batterys will check about 75% charged from the store. Yesterday I bought a lawn tractor battery from Mendards straight from the "on sale pallet" - it checked around 75% - I always charge before placing in service.

rustyfarmall · Mar 21, 2012

(quoted from post at 06:14:23 03/21/12)
There are various charts showing the battery voltmeter readings versus state of charge. I have one taped to the back of my voltmeter. The reading will vary based on the type of battery. The following example is from a Yuasa catalog and is what I use - for 6 volt batterys simply divide by two.

Battery Type: State of Charge - Voltmeter reading

Maintenance free: 100% = 13.0 volt : 75% = 12.8 volt : 50% = 12.5 volt
Lead antimony: 100% = 12.7 volt : 75% = 12.5 volt : 50% = 12.2 volt
Lead calcium: 100% = 12.6 volt : 75% = 12.4 volt : 50% = 12.1 volt

The problem with the voltage measurement is that one needs to know the battery type. Conversely, many modern batterys do not have removeable caps to allow checking the gravity.

Typically I find batterys will check about 75% charged from the store. Yesterday I bought a lawn tractor battery from Mendards straight from the "on sale pallet" - it checked around 75% - I always charge before placing in service.

Those are some pretty good guidelines, but dividing the figures in half for a 6 volt battery would place a fully charged battery at only 6.5 volts, and in reality a fully charged 6 volt batter SHOULD be at 7 volts or even 7.2 volts.

teddy52food · Mar 21, 2012

I always put the charger on a new battery before installing unless I know the tractor is going to be used for a while with a good charging system. You can have a battery showing voltage that has no power to the starter, so go by what the hydrometer says.

pete 23 · Mar 21, 2012

A six volt battery, (lead antimony) which has been sitting for over 24 hours without charging should read 6.3 volts. The 7.2 voltage mentioned is the normal charging voltage of a fully charged battery. If you put it on a charger for any length of time you have to remove surface charge to check no load voltage. Usually this only takes about 15 seconds like with the lights on or putting a 50 amp load on for few seconds. A 6 volt with 6.2 volts is not fully charged. It is like a gallon can of water that is two cups low. Sure, if it only takes one cup to start your vehicle you are fine, but if it doesn't start right away and need 8 cups you are up a creek. You are two cups short. Next thing is, that part of the plate that is not charged begins to harden and if left that way for any length of time it will not take a charge .

jeffcat · Mar 21, 2012

Just want to throw in a few more key strokes worth. Harbor Freght has those load meters for about $10to15 dollars on special. They are the best way to tell what is what with a battery. They check voltage and amps "load" all at once. I let my unit test "COOK" for about 30 seconds. If it still in the green zone you have a good HOT battery. These will also check your charging system too. Just flip the swich and your amp gauge will almost peg and the motor will load down. Now just remember my unit is the 50Amp unit and the newer ones are 100 Amp. I use my 50 maybe ten or twelve times a year and it is fantastic. I also have an old round face unit from the late 50s and it is also 50 Amp. Hope I helped. Jeffcat

Battery Charge

Cedric

Member

gene bender

Well-known Member

El Toro

Well-known Member

Indiana Ken

Well-known Member

rustyfarmall

Well-known Member

teddy52food

Well-known Member

pete 23

Well-known Member

jeffcat

Well-known Member

Similar threads