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Tip 2#

A separate charger and inverter or a Combi device: what do you choose?

The idea behind combi devices
Over 30 years ago, as an alternative to the separate charger and inverter, the inverter/ battery charger combination was introduced. At first as non-sine wave units (modified square wave they called it) later as sine wave inverter combi’s. The marine and mobile users discovered the advantages of this then new concept. The disadvantage of separate devices was that they took up quite a bit of space. By combining a charger and an inverter into one device saves the user space and money, because you only have to buy one device in which the shore/inverter/onboard grid switching system is built in.

There are a couple of disadvantages of the use of combi’s. One of the disadvantages of combi devices is that the built-in switching system can be a serious limiting factor, especially when the combi is used in combination with a high power generatorset. When a high power generator set is used, a switch-over system has to be added to the system.

Moreover, when choosing a combi, compromises have to be accepted as not all functions are as good as if you would install a separate battery charger and an inverter. Combi's, for example, are sensitive to voltage fluctuations in the public grid. At an AC voltage below 190 volts, the charger is no longer charging, the low incoming voltage will be transferred to the AC users connected and the device may even break down because the relay cannot handle the power properly. WhisperPower battery chargers can handle grid voltages up to 100 volts and still continue to charge. There are also differences in efficiency, i.e. the DC to AC or AC to DC efficiency loss when converting energy. This is especially valid for combi's that are equipped with transformers. They heat up quickly and need a lot of airflow to dissipate the heat.

With a separate charger and inverter, the system efficiency is higher and the energy loss is lower. In general, a smaller battery capacity can be chosen, charge time is reduced and as a consequence, when a generator is used to charge the battery, fuel consumption will be less and maintenance intervals extended. A good thing is also the reduction of emission, the system is becoming cleaner and greener.

With a system consisting of a separate charger and inverter, the choice to select the right inverter and charger is wider in terms of power (with WhisperPower inverters up to 14 kVA) and the devices are designed to perform the function optimally, without interference. The super compact SupremePro battery chargers of 100 amp are a great choice. Read more details here about this product.

In general, the output voltage of both the charger and inverter is cleaner (especially with high frequency inverters) with less ripple pollution back into the battery, resulting in longer battery life and no “ flickering” effect in the DC system. In addition, in the event of an unexpected failure of a Combi, a major problem arises because the entire energy system is down. Especially when reliability and flexibility and system quality are paramount, choosing separate devices is the best choice.

Selecting the right combi
If you are looking for a compact energy supply to be installed in a vehicle or boat, or weekend house, where space is limited, the combi can be the right choice. Keep in mind, however, that the combi should be powerful enough considering the AC appliances. Some AC equipment is sensitive to the quality of the output voltage of the inverter. In addition, no-load consumption, inverter efficiency and audible noise level are important. The inverter should be capable to deliver sufficient peak power for inductive appliances such as fridge/ freezers, electrical motors, tools, compressors and, for example, luxury coffee machines. Important: take into account the distance between the battery and the combi. In inverter mode, a 12 V combi supplying 2000 Watt draws 180-200 Amps of current (more than welding current of a welding machine). Another point of attention in case a diesel of gasoline generator is part of the system to re-charge the battery, the generator should deliver sufficient power with an output voltage of sufficient quality.

Separate inverter – charger systems
Although a combination inverter/ charger offers advantages for the user in terms of space and budget, there is a growing number of users who prefer to install an A-class categorie inverter, for example, to power sensitive and high power equipment on an "on-line" basis. So 24 or 48 VDC (high power inverters are in general operating on these voltages) from a charger, solar array or a wind generator, is supplied to the inverter, which converts the incoming DC to a sine wave AC without. No interruption in the AC line out is needed. The WhisperPower SuperInverters of 4,7 and 14 kVA are designed for this purpose. For smaller systems the WP Sine wave inverters can be installed with a separate battery charger.

Choosing the right battery charger 
A battery charger is the most commonly used device in an independent power supply system based on DC with batteries as the power storage. Only a qualified battery charger with a constant voltage current limited charge behavior, in multiple charge stages, will charge a battery properly and up to 100%. Fully automatic, fast, with a perfectly managed charge cycle ensuring a full battery and a long lifetime.

When choosing a battery charger the following applies: if you have a small battery capacity, limited DC appliances and limited AC power to operate through an inverter ( Nespresso coffee maker, hot pot, cell phone chargers etc) selecting a combi could be a suitable choice. After all, you can always use one of the two functions, charging or inverting, one of the two functions.

In case of high AC power appliances (air conditioning, induction hob, heavy duty tools, medical equipment) we advise to install a separate charger and inverter – the power of the DC charger should be sufficient to charge the battery and eventually supply direct power to the inverter’s DC input. WhisperPower’s SuperChargers (DC PowerCube) and Supreme Pro chargers are designed for such heavy duty on-line power systems.


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