[Plankton]

New battery was showing over 14v (December)when new but seamed to drop it's charge to just below 13v before use and as time went on with the battery not getting a lot of use but still being topped up with a charge it's now charging to 13.5v and before it's left the house it's at 13v. When hooked up to the system it shows around 13v and after a couple of hours usage drops to 12.7v.

My initial thought was there was something wrong with it?

Sellers reply was- The battery voltage for a good working performance is anything between 12.3 - 13.5. So really if it drops below 14V this should not be a problem. But i take your point on the incorrect advert for the battery. I can only apologize for this. 

My reply- A good battery shouldn't drop voltage in a short space of time after being fully charged.

[Ian Sheppard]

In Honesty a 0.3v drop over a couple hours is about what can be expected of a battery  under load from the pump.
After a few months use the lead cell will see some sulphation and a slight reduction in how much charge the cell can hold. It is good that the battery is being regularly charged as this will help extend its life. Also the longer a battery can be left drawing low amps the better as this low & slow current charging boosts the cell condition.

Most battery manufacturers say that 11V is the critical point as at 11V the battery capacity (amps) is mostly used. In gerneral terms you can use between 30 - 50 of the battery amps capacity so for a example a 100AH will have up to 50 amps of usable current,
 
The sign of a really worn battery is to see a sudden volt drop as it first comes under load. EG if you see it go from 13V to 12.5V or lower almost straight away.

The 0.3v drop over a couple hours is OK

[Plankton]

Thanks Ian.
I spoke to the suppliers technician this afternoon and he explained that the charger or split relay will put out a higher voltage to charge it and when removed from charge the battery will experience a slight drop within a few minutes due to the charging process. 
I did say to him that I may have been over analysing it. Customers eh!

[Spruce]

Thanks Ian.
I spoke to the suppliers technician this afternoon and he explained that the charger or split relay will put out a higher voltage to charge it and when removed from charge the battery will experience a slight drop within a few minutes due to the charging process. 
I did say to him that I may have been over analysing it. Customers eh!

The battery needs time to settle once it comes off charge. It is recommended that you will only get an accurate indication of the battery state of charge when a battery has been left idle and the voltage to stabalise and that takes about 4 hours.

A fully charged battery will read between 12.7v and 12.9v when fully charged.

I often watch my volt meter gauge after I switch the engine off. The charging voltages drops very quickly from 14.5/14.6v using the van's alternator. It drops quickly until it reaches the mid 13 volts and then takes longer and longer to drop lower. Once stabalised, I have only seen the voltage at 12.9v on a couple of occasions in the morning. I've never seen it higher than 12.9v. Its usually at 12.8v.

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