Information for car owners, caravanners, motorhomers and campers. All you need to know about batteries, battery chargers, solar panels/battery chargers, towing/trailer/caravan electrics, inverters and how to work out the size of leisure battery you need .
What's the difference between an engine starter battery and a leisure battery?
A leisure battery is designed to deliver a lesser current over longer periods which is often referred to as 'Cycling', or 'Deep cycling'. Leisure batteries are constructed differently to starter batteries to withstand the many cycles of discharging and recharging. It used to be inadvisable to use a leisure battery for starting purposes, but many leisure batteries are now 'Dual purpose'. A starter/engine battery is designed to give a quick surge of maximum power when you turn the ignition key and is not suitable for 'Cycling' purposes.
What does the 'CCA' rating mean?
The power the battery can deliver for a given time under certain conditions is usually referred to as its CCA (cold cranking amps). There are various different methods of measuring the CCA, but the most popular standard in the UK is the SAE (Society of Automobile Engineers) method.
Ampere-hour ratings (Ah)
The ampere-hour rating given to a battery (more relevant to leisure batteries than starter batteries these days) denotes the amount of energy that can be taken from the battery before the terminal voltage falls below 10.8 volts. This test is usually carried out over a 20 hour period (20 hour rate). Thus a 50 ampere-hour battery can be discharged at 2.5 amps for 20 hours before the voltage drops below 10.8 volts (i.e. 20 x 2.5 = 50). With leisure batteries ampere-hours is often abbreviated to amps (e.g. 85 amp leisure battery).
Tip!
Battery maintenance
Never leave either a starter battery or a leisure battery in a discharged (flat) condition as this will cause the battery plates to 'Sulphate' rendering the battery useless and also invalidate any warranty. Lead-acid batteries must be left in fully charged condition, ideally disconnected from the vehicle, and when left idle for long periods a top-up charge should be performed periodically (the use of a fully automatic battery charger is recommended). These rules apply to all types of lead-acid batteries. Most modern lead-acid batteries require very little, or no topping up. However, if on inspection (remove all filler caps), the electrolyte level has dropped beyond the top of the battery plates top-up with de-ionised water to a level of about 1/4" above the battery plates in each cell (12 volt batteries have 6 individual cells). NB: sealed for life batteries canot be topped-up.
Battery removal & re-fitting
When removing a battery disconnect the earth (-) terminal first and the live (+) last.
When re-fitting the battery connect the live (+) terminal fist and the earth (-) terminal last.
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What's the difference between a basic battery charger, a standard battery charger and a smart battery charger?
The 'Ring Basic' range of 12 volt battery chargers are suitable for lead-acid batteries (not Gel), have LED display to show charge progress, but will require supervised charging, i.e. they are not automatic.
The 'Ring Standard' range of 6 & 12 volt battery chargers are suitable for most types of lead-acid batteries incuding Gel. All have LED display to show charge progress, are fully automatic and have fast/slow charge selection.
The 'Ring Smart Charger' range have all the features of the standard range, but with the additional features below:
What if it's not sunny?
Our range of 'Sunsei' solar batter panels/batterychargers do not need bright sunlight to function - only daylight. The solar charger will maintain your battery/batteries effectively even on cloudy or rainy days.
Smaller panels, such as the 135mA and 400mA, supply a small trickle charge, cannot damage the battery and do not require a regulator.
Larger panels, such as the 1200mA, do require to be fitted in conjuction with suitable voltage regulator, such as the 'Sunsei' charge controller.
The simplest method of working your power comsumption is as follows:
watts divided by volts = current in amps.
Thus on a 12 volt electrical system a 120w pump will take 10amps (i.e. 120 watts/12 volts = 10).
So what power battery do I need?
Based on the above equation if you wanted to run the pump for 4 hours you would need at least a 40Ah battery. However, we would recommend allowing a 20% safety margin (i.e. 20% of 40 = 8), so we would recommend a battery of at least 48Ah.
And what Wattage inverter?
Obviously this depends on the wattage of the appliance you want to run off it, but again we would recommend a safety margin, i.e don't run a 300w appliance off of a 300w inverter, use a larger wattage inverter such as a 400w or 500w. Make sure the inverter is situated in a well ventilated area so that it doesn't overheat and remember that most quality inverters will have in-bulit battery protection, meaning that when the battery voltage falls beyond 10 volts the inverter will automatically cut out. This automatic cut-out system may shorten the theoretical running time the appliance, but the idea is that after using your appliance you will still be able to restart your vehicle.
How long will the inverter run for?
Say, for instance, you plan to use a 300w inverter to run 240 volt appliances it follows that the equation becomes 300watts/12 volts = 25 amps when the inverter is used o its maximum rating. Most quality inverters have an automatic cut-out facility which will operate before the battery gets too low on charge and ensuring the vehicle will still start. Although this facility is extremely useful it will also cut down the running time.
