TOWING A TRAILER

Many 4x4 users tow trailers, from the fairly simple, to the very sophisticated and expensive versions.
A great number of these incorporate a leisure battery, and sometimes several.  Built-in fridge units are also not uncommon, and these can pull between 500-1000 Watts per day, depending upon size and several other factors. Keeping these batteries charged is a major concern for several reasons:

1. Limited access to Mains power
2. Little or no alternator charge available
3. Trailer is often left behind whilst the 4x4 goes on game drives

It is possible to help keep the battery charged by employing a solar panel – but anything less than 80W will not keep pace with the consumption of the average fridge.  Some fit the panel onto the top of the trailer, but it is better to make the panel ‘mobile’ with extended Panelflex wiring to the battery because this will enable you to keep the trailer in the shade – thus saving the fridge from extra ‘cycling’ due to standing in the sun. Also your panel orientation and angling will have a major bearing on the effectiveness of the panel’s output and this is easier done on the ground then on a roof or bonnet. (refer our article on Panel angles, orientation and charge times).

Employing the 4x4 alternator to charge the trailer when you are travelling from site to site will require a fairly powerful alternator such as the Maxamp range from Plan My Power– probably over 100A.  Most 4x4s already have an auxiliary battery (or two!) located in the vehicle, so there is very little spare charge capacity left for the average alternator to charge up the trailer battery.  Most battery management systems only cater for 2 batteries, so the trailer is not really catered for as part of the charging control system.

At Plan My Power we have helped many trailer towers by increasing alternator output and adding a multi battery management system such as the EBM150-3 /S which can help to ensure a decent charge to the trailer when being towed.  Adding an MXS Booster regulator into the system will also increase voltage to the trailer where a drop of 1V is not uncommon.  Inadequate cabling thickness is another common mistake between the Anderson plug and the alternator.

For those of you who tow a trailer when venturing into the Bush – and there are many of you, keeping the batteries in the trailer ‘topped up’ is a constant concern.
There are several reasons for this:

1. There is usually a voltage drop from the alternator to the trailer batteries
2. Wiring thickness is inadequate for this application
3. Insufficient alternator power
4. Inadequate battery management system

Sometimes, the more ‘upmarket’ (expensive) trailers have a built-in 12V fridge which can flatten the average auxiliary battery within 24 hours. Many users also run lights and other appliances from these batteries further curtailing their battery duration.
 In order to maintain battery power there are several options available:

1. Up the alternator output with a Maxamp stator or alternator
2. Install a Battery Management System that can read the trailer battery’s condition
3. Install an MXS Booster Regulator to assist in fast charging the trailer battery
4. Install a solar panel onto your trailer
5. Keep a 220V charger handy for when you are near Mains power
6. Improve your wiring thickness
7. Use a small (silenced) ‘genset’ for charging up the batteries

Remember that the average small 12V fridge will consume from 500-1000W a day - depending upon age, make, model, content, ambient temperature and the amount and duration of door openings!

An average 105.A.H battery can deliver some 800W when fully charged, which is about enough for a day and a half of use before you start discharging the battery beyond the manufacturer’s recommendations, thus shortening life expectancy of the battery.
A 100W solar panel will supply some 550W on a good day – barely enough, but helping to ‘stretch’ the battery into another day without further assistance from the alternator or other power source.

E.G. a ‘best case’ scenario: small fridge, good sunlight, minimal door openings!

Day 1: Battery 800W fridge consumes 700W and panel supplies 550W leaving 650W in battery.
Day 2: Battery now 650W, Fridge consumes 700W panel supplies 550W battery now 500W
Day 3: Battery now 500W, fridge consumes 700W, panel supplies 550W, battery now  350W
Day 4: Battery now 350W, fridge consumes 700W, panel supplies 550W, battery now 200W

Of course, if you have a bigger fridge, or smaller panel ,then the situation will deteriorate rapidly. If you travel everyday with the trailer, then obviously you will be able to get some surplus power from the alternator system, but the solar panel will probably not give you very much as it must face north at a pre-determined angle – so you might actually get less overall!

If you have power in abundance from your vehicle’s alternator - because you have upgraded with a PMP 4x4 ’Optimised ’ system,  and you go on regular game drives, then you might have enough power to top up the trailer battery by removing it and putting it in the vehicle along with the other auxiliary batteries (leaving the trailer behind). Don’t forget that ‘night drives’, with headlights and spotlights on full power, inevitably consume more power and thus leave less surplus for the auxiliary batteries.

Contact Plan MY Power for some free advice and a quotation

GOT A PROBLEM? GIVE ME A RING, OR DROP ME A MAIL:

GEOFF: 072 909 3832; 011 678 5101 or gawie@planmypower.co.za