Thursday, August 9, 2012

Converter, Inverter, Charger - What's What And Why?

    While reading the various RV forums, I come across a lot of misinformation about converters, chargers, and inverters. Well, I'm here to set the record straight! What's what, which you should use and why.

Old "Boat Anchor" Convert/Charger"
In the beginning (OK not the BEGINNING, per se) most RVs had a simple converter. This device took 120V AC power from your shore power cord (or generator) and turned it into 12V DV power for your RV. This typically ran your lights, water pump, furnace, fridge, etc. Some models began to come with rudimentary chargers. These were single stage, meaning they put out a set voltage. Usually the amps were very low, from 2 amp to 6 amp. Not really enough to fully charge your batteries, but it did help. Later on, they became much better adding 3 (or 4) stage charging at a much higher amperage. These could be "smart" chargers that would maintain a battery bank quite well without boiling the liquid out of them.

New PD4645 Replacement Converter/Charger
  I have one of these. It's a Progressive Dynamics PD4645. It directly replaced the charging section of my original Magnatek 6345. In addition it also replaced the DC fuse panel with a more advanced design that shows me, using a red LED, which fuses have failed. To be honest, after I installed the first one, it buzzed. A Lot. I called the company and they exchanged it for another one. This one made a "sizzling" noise. Not that it was burning out, just a sound. Called again, they sent another. This one was much better. Only when there is no load on it does it make any noise at all and then only on shore power. I now had brighter lights, cleaner power and a full 45 amp 4 stage battery charger. All for well under 275.00!

Installed Converter/Charger

The install was easy and it really only took about an hour to do. The existing door and hardware still fits and the box from the exterior looks stock. I highly recommend this update as it will be nicer to your batteries and adds some useful functions to your DC power center.

Now let's switch to the AC side of things. An inverter takes DC power from you batteries and turns it into household style AC power, similar to what you will get from an outlet at home. They can be had in many power ratings from tiny 25 watt versions up to big bruiser 8000 watt types. There are two major types. MODIFIED SINE WAVE and TRUE SINE WAVE. The Modified one is the most common and can be purchased inexpensively from many sources. It outputs AC current that is similar to what you get from the power company at home, but slightly different. The picture shows how it has "star steps" rather than curves. The rapid on/off doesn't get along with some devices. Most devices will work fine with this, there are some that will not and few that it can actually hurt. Be Careful! True sine wave models give power that is identical (or better!) than what you get from your power company at home. That's great and all, but figure on spending 2x to 3x the price!

Battery chargers come in so many flavors it would be hard to list them all! Obviously, their main function is to, duh, CHARGE BATTERIES. Mainly, they vary in the amount of power they can use to charge the batteries. Typically from trickle chargers at around 2 amps up to rapid chargers at 100amps. The more amps you have the faster your batteries will charge up to a certain point. After that, most battery manufacturers suggest tapering off the amps (and volts) to gently bring the battery up to full charge. I prefer using 3 (or 4 stage) smart chargers these sense the state of the battery, some even have a temperature probe to modify the charging profile based on the temperature of the battery. This makes for a very effective charging system. Now, "simply"  add some Solar Panels and you can have free power as well. OK, simply is probably an overstatement, but it's not all that hard.

Now, just to add some confusion, you can buy any combination of Converter/Charger/Inverter. So each function could be in the same box.

Hopefully, this will clarify the purposes and names of the often confused components. I know I was a bit confused at the very beginning!

Be Seeing You...Down The Road,

Rich "The Wanderman"
www.thewanderman.com


12 comments:

  1. having to call the MFG for replacements doesn't bode well for their quality now does it?

    ReplyDelete
    Replies
    1. Bill,
      There was nothing really WRONG with the converter, I just didn't like the sound it made when under no load. It did work quite well. They were nice enough to send me units until I got one that didn't bother me. That's customer service!

      Rich "The Wanderman"

      Delete
  2. I have a inverter in my newly purchased (2002) MH

    Do I really need to run the tv off the inverter and batterys when I can simply fire up the genny and accomplish the same thing??

    Thanx

    ReplyDelete
    Replies
    1. Anon,
      Nope, you can certainly fire up your big, noisy, fuel consuming generator to run low wattages of home entertainment hardware. You can also use a 3 pound sledge hammer to push in thumb tacks. It WILL work...but is a but overkill. The inverter allows you to run things quietly and that is a good thing, especially in places that limit generator usage.

      Rich "The Wanderman"

      Delete
    2. Inverters come into their own for "Quiet" 110volt power creation, ideal for those times when you're camping in places without electrical service and posessed of "no-generator use between" hours.

      Delete
    3. Matt,
      Silence is truly golden!

      Rich "The Wanderman"

      Delete
  3. I had trouble keeping Inverters and Converters straight until I finally created this little memory jogger:

    IDA is a CAD

    IDA = Inverter changes DC to AC
    CAD = Converter changes AC to DC

    Oh well, any trick that works

    ReplyDelete
    Replies
    1. Bob,
      What about one for a Charger? Same as a CAD?

      Hmmmm....

      Rich "The Wanderman"

      Delete
    2. I think charger would just be BC = Battery Charger :p.

      Delete
    3. Big Matt,

      I could come up with a lot of words that fit BC! ;)

      Rich "The Wanderman"

      Delete
  4. If you wanted to install an inverter in an older motorhome.
    I was thinking before the converter?
    terry

    ReplyDelete
    Replies
    1. Terry,
      I'm not sure I understand your question. An inverter takes 12V battery power and turns it in AC House-style current. The converter takes 120V AC House current and turns it into 12V DC for your RV house loads. Inverters get connected to the battery bank...as directly as possible since they draw large amounts of current (amps).

      Rich "The Wanderman"

      Delete

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