The battery back up pump, being a second line of defense may be something that is never, or at most rarely, called upon to work. That should not be regarded as being harmonious with not needing to be reliable or powerful. In fact the day that the battery back up pump is required to function is the day that it needs to be as reliable as the mains pump even though that day may be only one in a thousand. If it fails on that day then the whole land is at risk of being ruined.
Below is a list of features that you should look out for when selecting your battery back up pumping system – I have prepared the list with an explanation of each feature wo that you will be able to make an educated evaluation of the systems that you are considering : –
1. The pumping rate of the battery back-up pump.
Surprisingly it is perfectly valid for a battery back up pump to have a lower pumping rate than the mains pump. Whereas a decent mains pump will typically delver 2.5 liters / sec to an 8ft head a back up pump will suffice with a pumping capacity of 1 – 1.5 liters / sec.
The reason a battery pump can serve as back up to a main s pump that is more powerful than itself is that it simple pumps for longer during each cycle, so over the course of an hour or a day or whatever it pumps the same total amount of water.
2. Battery capacity.
This is measured in Amphours. An amp hour is a unit of energy stored in the battery that allows the battery to discharge one amp of electricity for one hour, or two amps for half an hour, four amps for a quarter of an hour etc.
Battery capacity is far more important than the pumping rate of the pump as it determines the total volume of water that will be pumped on a single charge.
An 100 amphour battery will pump around 5000 liters of water to an 8ft head and batteries with greater or less capacity will pump a pro-rata amount.
3. Battery type.
The battery should have the ability to be discharged quickly without damage a property known as high torque. Ups batteries and marine and leisure batteries typically have the desired level of torque to serve this function, but no so car batteries which would have damaged irreparably if they were discharged fully and quickly.
Features to look for in a charger are: –
– ability to (automatically) boost or trickle the battery as needed
– ability to 'sense' when the battery pump is operating so that an alarm can be activated automatically by the charger. This allows the home owner to be alerted as soon as the back up system is activated rather when the battery is flat and it is too late to do anything about it.
– A test mode to test the operation of the back up pump and the alarm
– The ability to be connected to the burglar alarm telephone connection (if you have one) that way you can be alerted, or your keyholders can, even if there is no one at the property. This can save valuable time in getting the root problem fixed before the battery gets flat.
These are the main features to look out for and to compare between different models, armed with this information you can make a valid comparison of the options that may be presented to you rather than just looking at the price and thinking that all systems must be the same.
At the end of the day you should be aware that a battery back up pumping system is a means of buying time to get the mains problem fixed, it is not a solution that you should regard as being a semi-permanent replacement to the mains pump .
The information given above is just a general overview. Click the link if you wish to ask the author a question about pumping systems or any aspect of your cell conversion project.
This is the third article in a series which closely examines every aspect of waterproofing systems for cellar conversion projects.