|
We find that, in most cases, when problems occur with a DC compressor or solar fridge, the cause is usually related to the fridge's power supply.
Things to know about the power supply:
When we buy a 240-volt domestic fridge, we do not have to worry about the quality of the electrical supply. All houses are wired to a standard suitable for even heavy-duty appliances, so the current drawn by a domestic fridge will not affect the house's power supply. In other words, the power supply is sufficient to run the fridge.
This is not always the case in a 12 or 24-volt solar system. The fridge runs on the house batteries via the cables that connect to it. The cables that run to the fridge must, first and foremost, be of sufficient diameter to carry the fridge's load without the voltage dropping when the load comes on. The fridge circuit may also have an inline fuse, a switch, and several crimps, all of which can cause a poor connection.
- Poor crimp connections and a poor-quality switch may cause voltage drops in the cable, so even if the battery voltage reads correctly at the source, it may not read correctly at the end of the cable where the fridge is located.
- A battery that has been damaged by regular cycling will lose capacity as the lead plates corrode from deep discharges. Such a battery will show the following symptoms. (1) The battery will recharge quickly; a good battery should take several hours to recharge. (2) The battery may start to bulge at the sides of the 2 ends that are deformed. The battery is almost certainly no good. (3) The battery may become a little warm when being charged. A battery should not get warm if charged by a good charge system. (4) The battery voltage will fall very quickly under load, causing the fridge to become unreliable.
- Very occasionally, loose contacts may occur on the fridge, especially in motorhomes and caravans, due to the constant vibrations in the vehicle. Great care is taken to ensure this does not happen, if you have checked all other issues as described above then, check contacts at the rear of the fridge and if they appear to be a little loose, it might be a good idea to hot glue the contacts to prevent further movement.
- The solar system's battery capacity is too small. Sometimes the battery capacity of the solar system is ample to run the fridge through the summer when there is plenty of solar energy available; however, in the wintertime, when the weather is overcast, the battery may not last between sunny days. This can be solved by adding additional solar panels and using an MPPT-type controller so the battery remains charged even during poor weather conditions.
- A system with insufficient solar panels, for the demand on the batteries will distroy the batteries prematurely and cost more money long term, motor-homes are not always parked in full sunshine when the panels are fitted, the technicians often make the mistake of calculating the potential energy supply of the panels based on the best case conditions. When panels are in the shade, they cannot bring the batteries to full charge. That will also cause the batteries to fail. Some people will leave the fridge running 24/7, but if the vehicle is parked under a tree or in the shade of a building, it will only get sunshine for part of the day. Consider all these factors before looking for a fault in the fridge, because it will be the first appliance to stop working when the voltage drops too low.
Battery Voltages and what they mean:
In a 12-volt system, 11.9 volts is a dead flat battery, and 12.7 volts is a fully charged battery at rest. So the difference between a full and a flat battery is only 0.8 volts. It is easy to lose 0.8 volts to resistance in the vehicle's existing wiring.
We sometimes see a battery voltage of 13.7. This is when the battery is being charged by solar, the alternator, or a 240-volt charger. When all the charge systems are disconnected, the voltage should drop to 12.7 V at rest (nothing going in or out). A battery voltage below 12.7 indicates that the battery has not been fully charged yet or is no longer in very good condition.
If we see a voltage of 14.9 or thereabout, then the solar system is going through its final stage of the charging procedure. This should only happen for about 90 minutes per day. If that 14.9-volt voltage persists for more than 90 minutes, the system has a fault that can damage your batteries by overcharging them.
So if you suspect something is wrong with your batteries, be sure to check that the solar system is disconnected before checking the batteries. We have seen many "so-called experts" load-test the batteries while the solar system is still connected. The solar system will try to keep up during the load test, which can give a false reading. Naturally, they think that the batteries are in good shape. As soon as the sun goes down, the fridge experiences a low-voltage supply and will turn off once again, as the batteries are depleted through the night.
The fridge comes on regularly
A fridge that runs regularly due to the factors below will have a shorter life cycle, waste energy, and shorten the life cycle of the batteries.
- First of all, the fridge thermostat may be turned up too high. If the fridge has ice build-up at the rear, then the fridge temp is set too low. The fridge temp should be an average of about 4 degrees, which is hard to measure because the fridge may be 0 degrees at the back but say 6 degrees at the door. These measurements will also vary as the compressor cycles on and off and as items are added to or removed from the fridge. The best rule of thumb is to set the fridge to just around the freezing point at the coldest setting.
- The ventilation behind the fridge is not sufficient. Compressor fridges work by removing heat from inside the fridge and discharging it through a condenser. If the condenser cannot dissipate heat quickly enough, the fridge will keep running. Imagine the heat inside a motorhome could be 30 to 40 degrees in the sun when it is parked up. With little or no ventilation or air movement, the condenser is unable to get rid of the heat, so the fridge tends to run longer. Other causes of poor cooling could be a buildup of dust and dirt on the condenser, preventing it from dissipating heat.
- In very rare cases, the fridge may have lost gas. This will cause the fridge to run almost all the time, but the freezer temperature will not fall below freezing. Usually, this is caused by leaving the fridge off for long periods, which causes the internal pipes to corrode. It is always best to run a fridge 24/7 than to turn it off when it is not in use. Leave the fridge running at a very low setting.
- The door seal of the fridge may be damaged or misaligned, causing cold air to leak out and the compressor to run more often than normal. Place a torch in the fridge at night and check whether you can see any light coming from the fridge seal.
|
