Help with Inverter and/or Charger

[sbrown928@comcast.net]

Greetings,

I'm hoping to get some advice and guidance on getting an inverter and/or charger. My 73 Revcon has a converter and it's not doing my battery bank (2 batts) any good. I've figured I'm going to need about 1500 to 2000 watts but I just might be able to get away with 1000 watts. I also need a pure sine wave inverter. One think I have read, although not consistently, was that Xantrex is not as good as everyone says. Not trying to start a flame war here, I'm just trying to get the facts.

What I am after is an affordable pure sine wave inverter that I can tie into my existing outlets, what would you suggest as some of the more reliable and, again, affordable inverters?

Here's a little twist. I also need a battery charger. I would think that an all in one unit is going to be best as it kills 2 birds with 1 stone and includes the automatic switching. I am also more than willing to entertain separates. I'm not sure how to deal with switching in this scenario though.

Thanks.

Scott

73 Revcon 250

[tbutler]

You have posed an interesting question. As to brands, I think the main thing to look at is the control system. We have a Xantrex and the control system is complex and somewhat inflexible. That doesn't mean that the inverter itself is a bad inverter. It charges the batteries and produces current from them without problems. My main gripe is the interface with the automatic generator start function which may not be a concern for you at all.

One of your considerations in choosing inverter size is the battery bank available. The typical RV set-up is 4 6V batteries (Golf Cart type) connected in series and parallel to produce 12V current with good depth of charge (about 440 amp hours) for better service. People sometimes figure that 2 12V batteries will do the same thing but they don't. With two batteries, 6V or 12V, you will be limited in how much output you can get from an inverter. It won't do much good to have a 2000W inverter if it will only supply power for 2 hours. If you can't increase your battery bank, you might be just as well off with a 1000W inverter and limit your use of electric when on battery power.

I agree that an inverter/charger is the best system for keeping your batteries healthy. Most high end inverters also have charging capacity. They become an all-in-one battery interface with your electrical system.

[wolfe10]

In addition to considering battery bank size (in amp-hrs), the other consideration is what do you want to be be able to run off the inverter. That will tell you the watts you need AND also give an indication of whether you need a true sine wave inverter or one of the MSW units.

And particularly in a small coach, get to combo inverter/charger.

Brett

[sbrown928@comcast.net]

In addition to considering battery bank size (in amp-hrs), the other consideration is what do you want to be be able to run off the inverter. That will tell you the watts you need AND also give an indication of whether you need a true sine wave inverter or one of the MSW units.

And particularly in a small coach, get to combo inverter/charger.

Brett

Hey Fellas,

I have a small 2 12V battery bank. If the batteries and Walmart are to be believed then I have 200 amp hours in each of the 12 V batteries. I do not believe this but I don't know how I would verify how many amp hours the batteries actually have.

In any event, once these batteries are shot, the plan is to go with 2 6V batteries at about 425 amp hours. If I can figure out a good way to wire in 4 6V's, that would take it to 850 amp hours. I was hoping to avoid having this discussion as I've already figured out the wattage I want and what not but...

One reason I wanted a pure sine wave inverter is that I will eventually be getting a microwave, hence the wattage and sine wave. I don't have it now but I don't want to replace the inverter once I install it. I figure I won't be using the microwave often and won't really be used for long periods of time. I also have an LED LCD TV awaiting installation.

I'm trying to future proof the inverter.

I should note that I also have some cheap solar panels that will be going up for next season after I install a new roof rack for boondocking.

I hope this helps clear things up a bit.

So, can any inverter be wired into the coach so you can use any outlet or are you stuck using the plug in the inverter itself?

Scott

[wolfe10]

So, can any inverter be wired into the coach so you can use any outlet or are you stuck using the plug in the inverter itself?

Scott

Scott,

There are a number of ways, proper ways, to wire inverter output.

The one I like best, as it is totally idiot proof, is that the inverter IN 120 VAC has its own breaker in the 120 VAC breaker box. With pass-through feature, with the inverter sees 120 VAC in, it merely "passes through" the 120 VAC from the generator or shore power (does not invert from the batteries).

Inverter OUT 120 VAC is lead to a sub-panel supplying ONLY those circuits you want to be able to power from the inverter. Note: you also have to separate out the neutrals and grounds for those circuits you move from the main breaker panel to the sub-panel.

This keeps

[Cruzer]

Xantrex isn't the same company that it once was. The RS2000 and RS3000 inverters (I've had both) make nice true sine wave power and interface through a nice menu driven System Control Panel. However, they aren't as trouble free as the earlier Prosine (true sine wave) or Freedom (mod sine wave) inverters. Fans are particularly known to seize up. These units are made in China and are not field serviceable. They recently replaced it with a less expensive version, the Freedom SW3000 inverter. This too is a true sine wave and is less expensive. Again, it's made in China.

On the other hand, Magnum inverters are made in America and have an excellent reputation. Their pricing is fair and they are field serviceable so you can get parts for them. Many of the higher end coaches are going to the Magnum inverters rather than Xantrex. When my RS3000 goes I will definitely replace it with a Magnum MS2812.

One other neat trick pertains to energy management systems. An EMS typically sheds loads when on a 30 amp shore power feed to keep the total draw under 30 amps so that you aren't tripping the pedestal breaker all the time. About 90% of these systems are made by Intellitec. Precision Circuits also makes an EMS. But it's a better system with greater technology. One cool feature is that it can communicate with a Magnum inverter. That way the inverter can temporarily kick in to minimize having to shed circuits right away. For instance, with the Intellitec EMS if you are running your air conditioners and someone turns on the microwave for a few minutes the EMS will drop out the air conditioners until the microwave has finished. It'll then wait a few minutes and re-energize those circuits. That's typical load shedding. With the PCI EMS and a Magnum inverter the EMS will switch on the inverter to power the microwave rather than shed loads. If the loads are more extreme and the inverter can't make up the difference then the loads will shed as a second stage. If the EMS detects that the inverter has been running too long and the battery voltage is getting too low it will kick it out and shed more loads instead. Actually Magnum also makes an AGS module to start the generator if needed and can interface that as well. I recently removed my Intellitec breaker panel and EMS system and replaced it with the PCI system. I still have the RS3000 but when it goes I'll replace it with a Magnum and then I'll get that extra inverter boost functionality.

Magnum does make smaller inverters in both true sine and modified sine. The inverter/chargers feature 3 stage battery charging so you should have good voltage control in float mode to prevent battery boil-over and out-gassing. The inverter/charger will have an automatic transfer switch built in so that you can pass shore power through when inversion is not needed. Whenever shore power goes away the inverter will create (invert, actually) AC power from the DC battery power. Ideally you would locate whatever circuits you want to run on the inverter to a small sub-panel. Then feed the inverter's inputs from the main panel and send the inverter's outputs to feed the sub-panel. That way you won't overload the inverter with excessive current demands from air conditioners, water heaters, etc.