Batteries

Technical Guidance - Batteries

For sustainable power, you need to use deep cycle batteries.

Deep Cycle Batteries are very different from starting batteries.

They have much thicker lead plates and are measured in Amp-hour capacity. Vehicle Starting batteries are measured and rated in cold cranking amps (CCA ).

The best deep cycle battery type for off road travel is AGM (Absorbed Glass Matt).

How do I know the Capacity Level of the batteries?

The easiest is a Battery Monitor that measures battery voltage and amps flowing into and out of a battery. The Battery Monitor displays the percentage of battery life remaining and the amp-hours remaining. You don’t need to understand all the calculation process, just read the percentage capacity remaining.

The Alternative is the battery voltage. However, this has to be measured when the batteries are rested with no load. Typically for AGM batteries, 12.6V represents close to 100% capacity and 12V is approx 25% capacity. This is just a general guide and changes from battery to battery and battery type.

How long will the batteries last?

The manufacturer quotes a typical service life of 300-1200 cycles.

It can be longer and it can be shorter depending on how deep each discharge cycle is.

The deeper the discharge of the batteries on each use the less the cycle life.

The recommended depth of discharge is less than 50%. At this level, 600 cycles is typical which is 3-4 years use for most people, probably longer.

How do the batteries charge?

It is important to have 4 ways of charging when off road:

1. From the vehicle whilst driving
2. From a solar panel (s)
3. From a generator
4. From 240V at a powered site
   
   There is now a new 5th way to charge:
5.  Fuel cells

Are there any difficulties with charging from the vehicle?

There are significant issues in charging from a vehicle.

Deep Cycle (AGM) batteries need multi-stage charging to properly charge the batteries. If the charge voltage is less than at least 14V, then the batteries will never get to full capacity and there will be equalisation or sulphation issues as well as low capacity.

Battery management systems from most 4WD shops are a simple "common up" and charge system with an isolator. They protect the vehicle's starting battery but are virtually useless for charge management particularly with newer vehicles.

Some vehicles (eg. many common rail diesels) even reduce the voltage further (to near 13V), when the ECU thinks its cranking battery is charged and the engine bay is hot !

The best solution is a battery booster combined with a multi-stage charger.

How easy is it then to set up solar panels?

Solar panels are best set on their own simple stand pointing at approx 38 degrees upright in the direction of the sun. It is better to have 2 or 3 smaller panels than one large panel. This allows you to set the 2-3 smaller panels at angles to each other to get a more even power as the sun traverses the sky. It also makes them easier to handle and less like to break through "twisting of the large frame".

The other important factor for solar panels is to keep the back of them cool. So open panels with a simple folding leg is the simplest and the best.

Do you install the solar panels on the roof?

We install solar panels on the roof of the our off road Kimberley Karavan and they can be installed on most caravans. These are angled on either side so they are not in the same orientation. However, the caravan may be parked in the shade and the capacity limited. The advantage is that they are constantly charging.

What is involved with a generator?

A Generator is easy to setup and run. The disadvantages are the noise, carrying fuel and topping the fuel up. If the generator runs out of fuel, there will be a large power spike which can "blow" electronics if there isnt a surge protector. This even happens with the high quality inverter type of generator like the Honda EU10i and 20i. Generators need to be stored in a safe environment as the fuel vapour will escape.

What type of battery charger is best?

The best type of charger is the intelligent Multi-stage chargers. The capacity depends on the model purchased but is typically 10A to 40A. The higher Amp rating reduces the time to charge on 240V. Multi stage chargers are generally “connect and forget” chargers. Once the charger has completed its charging cycle, it drops to a safe “Float” voltage to maintain the batteries charge. It monitors charging voltage, current and time to make a truly smart decision about when to stop charging. The output of the charger is also perfect for all sensitive DC applications like computers and mobile phone chargers.

Can you use an Inverter? How does the Inverter Work?

There are 2 types of Inverters. An inverter converts 12V power from the battery into 240V AC power. The highest quality type is a high power (1500 to 1800W) pure sine wave unit. 

As a guide, this is nearly the AC power from a Honda EU20 generator. At high loads, an inverter will drain the batteries quickly. However, they are perfect for running certain devices in the bush. For example, the Panasonic SD251 Bread-maker will use only 53Ah and take less then 2 hours to make a 1 kg loaf of bread. The microwave can be used to reheat those stews and other tasty leftovers very easily.

The second type of inverter is a Modified Square Wave 500W unit. It will run the laptop computer, phone charger etc. All these devices convert the power back to DC again (though generally not 12V DC) It won’t run devices that use an AC motor directly or use an AC “clock”. 

Are there problems with remote power quality?

Generally mobile power supplies have problems with power surges. Typically, this can "blow up" battery chargers and other electronic devices even if they are otherwise quite robust.

A recommendation is to use a power surge filter. These typically are $300 and are quite compact.