Inverter/charger or Inverter & Charger each has some benefits. Separate also has some benefits. Which is better? Which would I choose? Inverters and chargers are actually two different items. Some manufacturers have built chargers into inverters and these units, depending on their design have some advantages over separate units. However, some inverter/charger combinations are not adjustable and are only suited to Lead Acid battery profiles. In this case, it may be time for an upgrade or replacement.
DC to AC
As previously discussed inverters change DC current stored in your batteries to AC current. AC current is used in modern appliances, like your television or microwave. Inverters are rated in watts output. My inverter is capable of 750 watts output and only used to power the entertainment systems in the RV. Other than 110v outlets for the televisions, we have one outlet hooked to the inverter, located in front of the passenger seat. Every other 110-volt outlet is not hooked to the inverter. Several devices still work however on DC from the battery, like my furnaces. The second circuit not hooked to the inverter includes my microwave, air conditioners, and other 110 volt outlets.
If I had a second inverter or a bigger inverter, the second un-powered parts of my RV could be operated from the battery – if the battery were big enough.
I also have one (and should have purchased two) portable inverters. I plug the portable inverter into a DC cigarette style outlet. Items plugged into the portable inverter are for small AC devices work, like a computer.
One of the things about my diagram to note is that the battery only powers the inverter if there is no AC power.
Both chargers (solar and generator) operate on a program ideal for lead-acid batteries. My inverter/charger and any inverter/charger I would buy will have three charge phases which are very good for lead-acid batteries. Bulk, absorb and float. Each phase of charging limits the output according to the needs and desires of the batteries. Bulk and absorb putting out the most amperage and float contributing to “topping off” the charge to slowly achieve 100%… full charge. Both chargers also have a maintenance mode called equalization.
The reason that I should have purchased two portable inverters is that both my wife and I could use one each. My 750-watt inverter is rarely tasked to produce anything near 750 watts. More frequently it operates at way less than 100 watts. However, the operating costs, in terms of power used, typically are equal to the power distributed multiplied by two. That is to say, my 750-watt inverter consumes lots of power. Just by having the switch on, in standby mode, it consumes lots of power. If instead, I used two portable units rather than my bigger inverter is that the portable units less wasted operating power.
Inverter with built-in Charger
One good thing that my inverter does is that anytime outside AC power is on, regardless of source, shore power or generator, it switches modes and charges my battery. Thus it is an inverter/charger. The charging ability of my inverter/charger is valuable to me. If I didn’t have that, I would need a separate charger to accomplish this task.
My charger will also work in parallel with my solar charger so that both charge the battery at the same time. The charger portion of my inverter is rated at 45 amps (rarely if ever puts out more than 35 amps). The solar charger is rated at 50 amps and has never put out more than 40 amps. Used together, they have never exceeded 45 amps in my observation. One of the reasons I have never observed larger outputs is that if the sun is bright on my panels, I don’t turn on my generator.
My solar charge controller is way more flexible in charge profiles and includes a mode ideal for lithium batteries; my 750-watt house inverter does not. Lithium batteries can accept much higher charge rates (more amps per hour) than lead-acid batteries over a longer duration. Typically lithium batteries will accept charge rates up equal to the battery rating. A 100 amp hour battery could be charged at 100 amps in one hour. For an even greater extended battery life, charging at half this rate would be a good idea. Charging a 100 amp-hour lead-acid battery at 100 amps for one hour would destroy the battery. Lithium batteries don’t need tapering off on the charge rate. Lithium batteries also don’t care that they are fully charged.
My 750 watt inverter/charger is set up for lead-acid batteries and would treat lithium batteries incorrectly. In essence, it would be confused. Lithium batteries hold a very constant voltage for most of the discharge cycle only losing voltage toward the end of discharge. This would confuse the inverter charger and it would never put out a high amperage rating to the lithium batteries to recharge them at a fast rate.
If I was satisfied with my inverter, (which I am not) I could add a secondary dedicated charger that would have the profile necessary for lithium batteries. Thus I would be breaking the inversion and charging task into two parts. This might be a good idea, even if I were to replace the inverter with a dedicated inverter and a separate dedicated charger.
An inverter plus a separate charger, both large would cost less than getting a new inverter/charger of the same abilities. This would be the way to go, with the exception that some more advanced inverter/chargers can be described as smart chargers, just like my solar charge controller.
Intelligence varies between brands, but a few smart features include an ability to automatically limit charging from small power AC sources which would give priority to user-selected devices over re-charging the battery and also the ability to combine the output of the battery with the output of a small power AC source to run a larger demand device (or a combination of more than one device) from a limited power source that would normally not be able to keep up with such a demand.
All this being said, I am ready for a new “smart” inverter/charger.