The Importance of Battery Maintenance

A 12 volt battery is an important part of the WFP system. If well maintained as part of an efficient system a good quality leisure battery can last 12 – 18 months or more. Why then do so many people have issues with low battery voltage? Why is a battery often the forgotten part of the system? Poorly maintained and worn batteries can mean:

  • Poor and erratic flow rates
  • Shortened battery life
  • Lost work due to down time
  • Replacement costs

The aim of this blog is to show that a regular battery maintenance routine can aid efficiency, avoid breakdown and extend the life of your battery.


WFP systems commonly use deep cycle leisure batteries. These batteries have lead cells that contain sulphuric acid. In a good condition battery with good charge the sulphur will be in a liquid state. When the battery is under load the sulphur reacts with the lead cells to create current that is passed to the terminals to supply the pump. As current is taken from the battery the sulphur changes from a liquid to a crystal. These crystals can stick to the lead cells, resulting in a fall in both the current (measured in amps) and the voltage (measured in volts).


Most leisure batteries can be discharged to between 30% and 50% of their capacity. Capacity is the amount of amps the battery can store. For example, if we assume a new 85AH battery is fully charged and is capable of a 50% discharge, then it has 42.5 amps of available current before the battery will need recharging. The available capacity will be lower with a worn battery or where it is not fully charged. A battery can also discharge up to 5% of its capacity a week even when not connected (this is called parasitic or self discharge).

What can also happen is that the sulphuric acid becomes weaker and less effective, and as a result it becomes watery. This then means the battery is more likely to freeze or be affected by low temperature. For this reason battery charge will last for less time in colder weather.

NOTE: Capacity (current) is monitored by measuring the voltage: the lower the voltage, the lower the amps or available capacity.


A 12 volt leisure battery is made up of six lead cells. Each cell has a maximum (full charge) point and a minimum (discharged) point.

The maximum voltage per cell is between 2.1V and 2.3V, so a well maintained battery in good condition will have a full charge of between 12.6V and 13.8V. It is recommended that at the start of each working day the battery voltage be as close to 13V as possible in order to maintain its condition and prolong its life.

The minimum voltage per cell is 1.75V, so a fully discharged battery will have a voltage of 10.5V. At this stage crystals harden onto the lead cells and attach permanently. Once the cell is damaged it will not hold a charge as well or for as long. A sure sign of a worn battery is a big voltage fall-off as it comes under load from the pump. Generally if the volts fall by more than 0.5V the battery is not holding a charge. Also it will run down quickly – in some cases in less than an hour. It is therefore recommended that the battery not be allowed to discharge to below 11V.

Voltage Collapse

Once a battery reaches its maximum discharge point both volts and capacity (amps) will go into free fall, ie a voltage collapse. This sounds dramatic and, in terms of your battery, IT IS. What happens is that, rather than a gradual fall in voltage as the current is discharged, the volts literally drop away to nothing in an instant. At this point the battery will be beyond recovery.

Low Battery Cut Off

New batteries can be expensive. However, there are also hidden costs with a poorly maintained battery as it ultimately affects the WFP system's capability to clean quickly and effectively.

To aid battery maintenance, Spring controllers have a built-in battery protection system that measures the voltage across the battery terminals for accuracy. When the voltage drops to 11V the display shows the message “bat” as a warning. When the voltage drops to 10.5V the system automatically turns off the pump.


To maintain a battery in good condition for as long as possible it should be placed on mains charge once the voltage falls to 11V. As the battery charges, the sulphur crystals attached to the lead cells revert to their liquid state. However, if the battery is left too long no amount of charging will clear the cells.

Restoring the battery to 13V prolongs its life and makes the working day easier (and potentially longer!) The best way to do this is overnight with a mains charger as long low amp charging is the most effective way to get the lead cells back to a good condition. Split relays are useful for adding some charge but the battery will still need a mains charge every second or third day.

In Summary

Maintaining the battery through regular recharging via a mains charger is essential. A poorly maintained battery will degenerate and need replacing in a matter of weeks, with a dropping-off in performance of the WFP system at best and a WFP system at a standstill with a battery beyond repair at worst.

In terms of the protection it affords your system, it is a no-brainer: it is time well spent and ultimately money saved.