can someone please explain what pump calibration dose

[spruce]

Battery charging is a little more complex that sticking a volt meter across the positive and negative terminals. @Dragbag

Before any testing is done to find a true state of battery charge the battery should rest for 4 hours. This is to let the voltage across the cells stabilise completely.

A fully charged battery will read 12.7v or higher.

12.5v = 75% charged

12.4v = 50% charged

12.2v = 25% charged

12v or less = discharged.

For best battery longevity you should never let your battery drop below 50% charged. I aim for 75% and higher.

You will notice that there are only very small voltage differences between the different state of charge readings. Having a little gadget going from green to red just isnt accurate enough.

I have a VSR on my van (voltage sensing relay). The van went out this am with a fully charged leisure battery. We didn't do much work as I wasn't feeling too good so we were back by 14.30. The volt meter is reading 12.8v when I looked a few moments ago. I have just put the charger on the backpack so have also plugged in the leisure battery charger. It senses that the battery is nearly full and is just charging the leisure battery with 0.9 amps.

It will do that for about an hour and then revert to float charging which are fractions or pulses of charge to keep the battery maintained at full charge. It can be left of for months like this.

BTW, there is nothing wrong with putting your battery charger onto your leisure battery as soon as you get home. The battery charger will cover any voltage discrepancy across the cells.

 

[spruce]

There's another side to battery charging @Dragbag.

A battery charger needs to charge at a higher voltage output than the battery is to 'push' charge back into the battery.

My intelligent charger will charge my leisure battery at 13.9v. When my van's alternator is charging the battery it will charge initially at 14.2v and as the battery becomes more fully charged the charge voltage will creep up to 14.5v.

When I switch my van's engine off the voltage across the terminals will drop very quickly but will slow down as time goes on. This is the voltage across the cells stabilising.

It works the other way as well. You don't have a split charge relay. When you are out cleaning windows your battery will show a lower voltage because it is under load. Once you switch your pump off the voltage will climb slowly until it stabilises after 4 hours. It might be a few % points higher than when you first switched the pump off.