Batteries require a lot of TLC. If they receive care then they will serve you for years – with good holding charge capacity.
Types of battery
- Flooded – These batteries have a conventional liquid electrolyte (Lead-acid). Standard types have removable caps so that de-ionised water can be added. Standard flooded batteries are cheap and if they are kept topped up they are not overly sensitive to high charging voltages. Sealed batteries have fixed valves to allow gases to vent during use.
- Gelled Electrolyte – The electrolyte is a jelly and so will not leak. The electrolyte cannot be diluted such that over-charging must be avoided. These batteries may only last for 2 or 3 years in hot climates, although with good care they can last for 5 years.
- Absorbed Glass Mat (AGM) Batteries – The electrolyte is held between the plates absorbed in a fine boron-silicate mat. Like gelled electrolyte batteries they will not leak acid but they can withstand more careless treatment and are less sensitive to overcharging since they are designed to retain vented gases. AGM batteries can also stand for 30 days in a totally discharged state and still be recharged successfully. The major drawback to these batteries is that they cost between 2 or 3 times as much as flooded batteries.
At least annually thoroughly clean the battery tray, terminals and connectors and smear the latter with petroleum jelly. Unless sealed for life, remove the battery vent plugs or strips and shine a torch into each cell to check the liquid level, which should cover the top of the plates. If the plates are exposed, top up with distilled or de-ionised water ONLY. A digital voltmeter is the easiest way to check the voltage across the battery terminals.
The following chart is an approximate guide to the state of a battery. Green indicates a good level of charge and is key to a long-lived battery. Orange shows that you should charge your battery soon to avoid any damage or loss of power. If your battery has been left in red for a few days you may have already permanently damaged it. You can see from the above that batteries require a lot of TLC. If they receive care then they will serve you for years – with good holding charge capacity.
Charging sealed batteries
Some batteries, often called ‘maintenance free’ or ‘sealed for life’, have cells that have no filler caps, and which are not intended to be topped up with water. It is important that such batteries are not allowed to ‘gas’ since this will reduce the level of the electrolyte in the cells, which cannot be topped up.
It is known that ‘gassing’ commences when the voltage at the terminals of the battery rises above a level that for most batteries is around 14.1 Volts. Below this voltage, there is negligible gassing. It is therefore important with such batteries that the voltage at the battery terminals is kept below this value.
Such batteries are preferably charged with an automatic or voltage-controlled battery charger. Sealed batteries can be charged with care using a normal battery charger but this then requires the use of a multi-meter.
Maintenance-free batteries frequently appear to be completely sealed. However, like standard batteries, they do have openings for the release of gases.
Choosing a battery charger
A proven and good charger is well worth paying out for, and an example is the C-Tek range, and the one used by most caravaners is the MULTI XS 3600.
The MULTI XS 3600 is a switch mode charger with pulse maintenance for lead-acid batteries 1.2Ah to 120 Ah and is one of a series of professional chargers from CTEK. It represents state-of-the-art technology within battery charging. A MULTI XS 3600 will prolong the service life of your battery. This carries out the following charging operations :-
Bulk – Charging where 80% of the energy is returned. The charger delivers an almost constant current until the battery voltage reaches maximum level.
Absorption – Charging up to almost 100%. The charge current falls and the voltage is kept constant at the maximum level.
Pulse – Maintenance phase, where the charger delivers a pulse if the battery voltage drops. Charging varies between 95% and 100%. The battery receives a pulse when the voltage reduces keeping the battery in good condition when not in use.
Automatic Modes – This charger begins charging with an almost constant current (0.8A or 3.6 A) until maximum voltage (14.4 V or 14.7 V) is reached. The charger changes mode at this point. (Necessary for sealed batteries) It locks the voltage at maximum level and allows the current to drop. The MULTI XS3600 switches automatically to pulse maintenance charging when the current drops to 0.4 A. The charging cycle restarts if the battery voltage drops to 12.8 V or 12.9V.
If the charger lamp and the maintenance-charger lamp are flashing alternately, the reason for this is due to:
- An interruption during charging, due to a loose connection or because the battery has ceased to work.
- The battery has become sulphated. If the lamps flash for more than 30 minutes, this indicates that the battery is dead and needs to be replaced.
- If there is an interval of more than 10 seconds between the flashes, this indicates that the battery has a high self-discharge rate and may need to be replaced.
There is an additional feature incorporated, that on mains failure or unplugging, the C-Tek will ‘remember’ what it was doing and resume its settings when the mains power is restored.
From the above information, you can see why it is perhaps the best charger to have. Leaving this charger permanently connected could make your battery last for years. I have replaced the on board factory fitted charger with the C-Tek, and the battery is six years old.
From the above information, you can see why the C-Tek chargers are perhaps one of the best makes, and if you can afford it, buy the C-Tek MXS 7000 for about £80. This charger has a better performance specification than the 3600.
Article Provided by Pete of the BO, CaravanTalk Author