Inverter, converter or both?

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Inverter, converter or both?

Postby kenaxelds » Fri Jun 17, 2016 6:42 pm

I'm looking to convert a cargo trailer for camping use, and stumbled on this site. First, let me say "Thank you." What an awesome community and supportive bunch!

I'm designing the electrical system I plan to use (I know...planning? My younger self would scoff at the idea) in my trailer. I'm trying to decide if I really have a need for a converter. I know I can get an inverter with a battery charger and/or I could get a converter with a battery charger, but do I really need both? I'd like to be able to charge the batteries from shore power or a generator when necessary.

Here's my general plan:
1) Have several deep cycle batteries (minimum of 200 ah, probably more)
2) Honda 2000 generator (for charging batteries when needed and possibly running air conditioner, if added later)
3) Pure sine inverter (2000W+) with charger (like this AIMS or this Magnum)
4) Looking to eventually add 200+ watts of solar panels (living in western Oregon isn't the best place for solar...I need a rain-powered generator)
5) I will most likely use 12VDC for trailer fan, lighting and charging of phones and other small devices
6) I'll use 120AVC for TV, laptops and...most other "stuff"

If the converter's job is to take 120V down to 12V, can't I just run my 12V items straight from the batteries (using a bus bar or something similar)? I'm sorry is this sounds like a silly question. While I have some experience with 120 VAC, I've never really played around with DC, but I see enough folks adding converters to their systems, I think I may be missing something :NC
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Re: Inverter, converter or both?

Postby Shadow Catcher » Fri Jun 17, 2016 7:52 pm

The converters primary job is to charge the battery and that includes from the generator.
There are a several aspects, the goes into, converter, solar, hydro electric. Goes outa, lights, inverter, TV, radio chargers... The third aspect is conservation.
12V is more efficient that converting from 12V to 120VAC, use LED lights do not use battery power for resistance heat appliances i.e. coffee makers...
Monitor your battery bank using a battery monitor Trimetric or Victron the measure the goes into and the comes outa.

Consider using a high voltage solar panel, it produces usable current at lower light levels. Ours was intended for grid tie system and puts out 72 V no load and in full shade 34V, requires MPPT controller.
Last edited by Shadow Catcher on Tue Jun 21, 2016 7:45 am, edited 1 time in total.
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Re: Inverter, converter or both?

Postby flboy » Fri Jun 17, 2016 8:12 pm

kenaxelds wrote:I'm looking to convert a cargo trailer for camping use, and stumbled on this site. First, let me say "Thank you." What an awesome community and supportive bunch!

I'm designing the electrical system I plan to use (I know...planning? My younger self would scoff at the idea) in my trailer. I'm trying to decide if I really have a need for a converter. I know I can get an inverter with a battery charger and/or I could get a converter with a battery charger, but do I really need both? I'd like to be able to charge the batteries from shore power or a generator when necessary.

Here's my general plan:
1) Have several deep cycle batteries (minimum of 200 ah, probably more)
2) Honda 2000 generator (for charging batteries when needed and possibly running air conditioner, if added later)
3) Pure sine inverter (2000W+) with charger (like this AIMS or this Magnum)
4) Looking to eventually add 200+ watts of solar panels (living in western Oregon isn't the best place for solar...I need a rain-powered generator)
5) I will most likely use 12VDC for trailer fan, lighting and charging of phones and other small devices
6) I'll use 120AVC for TV, laptops and...most other "stuff"

If the converter's job is to take 120V down to 12V, can't I just run my 12V items straight from the batteries (using a bus bar or something similar)? I'm sorry is this sounds like a silly question. While I have some experience with 120 VAC, I've never really played around with DC, but I see enough folks adding converters to their systems, I think I may be missing something :NC




Following is a schematic of the system I am currently installing in my CTC build. You can have more or less solar cells or batteries to suit your power needs... but I built a similar system in my last CTC and it worked great. I am using an inverter (DC to AC) and a converter (AC to DC) and have a Solar charging system as well. If you have any questions, I can try to answer. I do have a parts list for most of the major components. Almost all from Amazon.com.




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Don (Flboy)

Current Build CTC:
viewtopic.php?f=42&t=65498
Old CTC Build (sold)
viewtopic.php?f=42&t=50647
YouTube Videos of Finished Trailer:
https://www.youtube.com/watch?v=FASF-x9ofMY - Interior
https://www.youtube.com/watch?v=wb-pvBbyyBs - Exterior
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Re: Inverter, converter or both?

Postby noseoil » Sat Jun 18, 2016 7:58 am

Many of the people on this site have wrestled with the same problem. I'm just one of them who had to decide what to do & how to do it. My decision was to go with a PD4045 distribution panel for the system. It uses a converter to charge the battery & provide 12 volt energy, has 110 volt breakers for the shore power stuff, 12 volt fuses & does most of the electrical stuff in a small package. I run two inverters, one does the galley (2,000 watt) & one does the entertainment system (200 watt) in the cabin.

Most of my charging is done with a 100 watt solar panel mounted on the roof, but I just have a single group 27 AGM battery in the galley. So far we've never run out of power.
Build log: viewtopic.php?f=50&t=60248
The time you spend planning is more important than the time you spend building.........

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Re: Inverter, converter or both?

Postby kenaxelds » Sat Jun 18, 2016 9:20 am

Shadow Catcher wrote:The converters primary job is to charge the battery and that includes from the generator.

I was hoping to use the inverter to handle charging duties. It sounds like there’s a few good ones that can handle the job. Using higher voltage solar panels is a great idea!


flboy wrote:I am using an inverter (DC to AC) and a converter (AC to DC) and have a Solar charging system as well. If you have any questions, I can try to answer. I do have a parts list for most of the major components. Almost all from Amazon.com.

Thanks, Don. I’ve seen your build(s) and the schematic. Nicely done. You have a converter to handle charging, plus an inverter. I know I’ll need an inverter, and if it’s charging the batteries for me, I don’t quite understand what the converter will be needed for. I’m not saying it doesn’t have a purpose, I just don’t know what that purpose might be, if that makes sense.

noseoil wrote:Many of the people on this site have wrestled with the same problem. I'm just one of them who had to decide what to do & how to do it. My decision was to go with a PD4045 distribution panel for the system. It uses a converter to charge the battery & provide 12 volt energy, has 110 volt breakers for the shore power stuff, 12 volt fuses & does most of the electrical stuff in a small package. I run two inverters, one does the galley (2,000 watt) & one does the entertainment system (200 watt) in the cabin.

I like the idea of using two inverters (big and small). I can see how that would limit what amp draw when you can just turn on the small inverter for small jobs. I’ve already got a 150 watt inverter that can (just barely) run my CPAP. I just can’t decide if a inverter/charger combo is worth the money or if I should go the converter/charger route.

Welp, I have three votes for a converter. I still don’t have a great grasp on the “why” of it, but with the internet at my fingers, there’s no excuse. It just means I need to do a bit more research.

Thanks, gang!
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Re: Inverter, converter or both?

Postby MtnDon » Sat Jun 18, 2016 2:06 pm

Most commonly used inverters do NOT incorporate a battery charger. You do find inverter / chargers such as the ones you linked to. I believe you will find most TD's and small trailers do not use inverter / chargers. Partly because of the cost factor when looking at the better brands.

The thing the PD4045 provides that is nice is the breakers (AC) and fuses (DC). As well it is a charger and is used to supply DC when connected to a campground power system.

An aside... how many batteries and what type are you planning on? And are you planning on using the full capacity of those 2000 watt inverter / chargers? To pull 2000 watts of AC from a 12 volt battery system needs something like 450 amp hours minimum IMO. With too small of an amp hour capacity 12 volt lead acid batteries suffer from severe voltage drop. What AC devices do you plan on using?


Also... there is a huge difference in quality between an AIMS inverter and a Magnum. Huge difference.
Our 6x12 deep vee nose cargo trailer camper conversion... viewtopic.php?f=42&t=58336

We have a small off grid cabin we built ourselves in the NM mountains; small PV solar system; 624 watts PV, Outback CC & inverter/charger ... http://countryplans.com/smf/index.php?topic=2335.0
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Re: Inverter, converter or both?

Postby MtnDon » Sat Jun 18, 2016 2:30 pm

Personally, I really like a quality inverter / charger; Magnum, Outback, some Xantrex are the ones that come to mind. The chargers built into those are among the very highest quality.

Question for you... will your use be mainly dry camping, no camprground hookups? An inverter / charger makes best sense to me in boondocking use. Add a quality fuse box for the DC circuits. Bluesea has some. Midnite Solar has some very good breakers for DC. Plus install a small AC breaker set for the AC side.
Our 6x12 deep vee nose cargo trailer camper conversion... viewtopic.php?f=42&t=58336

We have a small off grid cabin we built ourselves in the NM mountains; small PV solar system; 624 watts PV, Outback CC & inverter/charger ... http://countryplans.com/smf/index.php?topic=2335.0
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Re: Inverter, converter or both?

Postby flboy » Sat Jun 18, 2016 10:12 pm

An inverter takes 12VDC (Some may take 24 or 48VDC) and makes AC 110VAC. It is called an inverter because it does the opposite (inverse) of a converter that converts 110VAC to 12VDC.

The Converters usually also charge the battery. That is the main purpose of having it if you have batteries. I have not seen an Inverter that charges a battery. If it does, it is wasting power converting DC to AC to convert back to DC to charge the battery? That would be strange?

In any case... sometimes folks confuse the two. :thumbsup:
Don (Flboy)

Current Build CTC:
viewtopic.php?f=42&t=65498
Old CTC Build (sold)
viewtopic.php?f=42&t=50647
YouTube Videos of Finished Trailer:
https://www.youtube.com/watch?v=FASF-x9ofMY - Interior
https://www.youtube.com/watch?v=wb-pvBbyyBs - Exterior
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Re: Inverter, converter or both?

Postby GuitarPhotog » Sat Jun 18, 2016 11:05 pm

I had to look, but there ARE inverter/converter combo's. They seem to be pretty expensive in the sizes the OP seems to be talking about.

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Re: Inverter, converter or both?

Postby jml79 » Sun Jun 19, 2016 2:43 am

flboy, if you indeed have an MPPT charger and a bunch of 20w panels, you need to change how your panels are wired. The point of an MPPT charger is to use a high voltage input and using a buck converter drop that efficiently to a proper charge voltage. I use 4 40w panels. Each produces 2.4 amps at a nominal voltage of 16.6v but the reality is actually higher, more like 19v at peak sun. Wired in parallel like yours I get a max output of 19v @ 9.6A = 182 w but I would lose almost 15% to conductor loss over 50' at 9.6 amps. Wired in series the panels make over 80v but at a much lower 2.4 amps. With this setup I lose less than 5% with a 50' cable and charge my batteries much faster. Overall the gain during peak sun is almost 20% and my panels provide a usable charge almost 2 hours longer than before.
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Re: Inverter, converter or both?

Postby flboy » Sun Jun 19, 2016 8:07 am

jml79 wrote:flboy, if you indeed have an MPPT charger and a bunch of 20w panels, you need to change how your panels are wired. The point of an MPPT charger is to use a high voltage input and using a buck converter drop that efficiently to a proper charge voltage. I use 4 40w panels. Each produces 2.4 amps at a nominal voltage of 16.6v but the reality is actually higher, more like 19v at peak sun. Wired in parallel like yours I get a max output of 19v @ 9.6A = 182 w but I would lose almost 15% to conductor loss over 50' at 9.6 amps. Wired in series the panels make over 80v but at a much lower 2.4 amps. With this setup I lose less than 5% with a 50' cable and charge my batteries much faster. Overall the gain during peak sun is almost 20% and my panels provide a usable charge almost 2 hours longer than before.



I am using 5 100W panels for 500W.. I must have made a typo on the schematic. The MPPT should work fine with this, that is what it was designed for. My cables from the solar cells to the MPPT controller are less than 8 feet. The 5 th panel I put on was to cover for any inefficiencies. I only needed 4 100W, but instead of spend all the extra $ on the higher cost 24VDC or 48VDC inverters and converters to squeeze a few amps more out of 4 cells , I put on 5. The panels was $124.. A much more cost effective solution for me in this case.
Don (Flboy)

Current Build CTC:
viewtopic.php?f=42&t=65498
Old CTC Build (sold)
viewtopic.php?f=42&t=50647
YouTube Videos of Finished Trailer:
https://www.youtube.com/watch?v=FASF-x9ofMY - Interior
https://www.youtube.com/watch?v=wb-pvBbyyBs - Exterior
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Re: Inverter, converter or both?

Postby kenaxelds » Sun Jun 19, 2016 9:43 am

Thanks, all, for the great responses and questions!

MtnDon wrote:The thing the PD4045 provides that is nice is the breakers (AC) and fuses (DC). As well it is a charger and is used to supply DC when connected to a campground power system.

An aside... how many batteries and what type are you planning on? And are you planning on using the full capacity of those 2000 watt inverter / chargers? To pull 2000 watts of AC from a 12 volt battery system needs something like 450 amp hours minimum IMO. With too small of an amp hour capacity 12 volt lead acid batteries suffer from severe voltage drop. What AC devices do you plan on using?

Hey, Don. You've already been a huge help (I got a lot of great ideas from seeing your 6x12 build). I was planning on running two 6V golf cart batteries in series at the start. Because I expect this build to start small and grow (and I haven’t fully decided what the final state is going to be yet), my power needs aren’t as well defined as they should be, but here’s what I’m guessing I’ll be running at the end:

On AC:
1) About a 19” TV with built-in DVD player
2) Laptop computer
3) Small Refrigerator
4) Hair drier (obviously not mine, lol...but a big reason for the large inverter)
5) Possibly a toaster or toaster oven (we don't really use a microwave for anything)

On DC
1) Stereo
2) Water pump
3) Interior and exterior lights

I can get my lovely bride to live without an indoor shower, but living without a hair dryer? I'd rather attempt it :)

MtnDon wrote:Personally, I really like a quality inverter / charger; Magnum, Outback, some Xantrex are the ones that come to mind. The chargers built into those are among the very highest quality.

Question for you... will your use be mainly dry camping, no camprground hookups? An inverter / charger makes best sense to me in boondocking use. Add a quality fuse box for the DC circuits. Bluesea has some. Midnite Solar has some very good breakers for DC. Plus install a small AC breaker set for the AC side.

Yes, the trailer will be used almost exclusively for boondocking. I don’t ever plan on using it in a campground or RV park, but there's always that possibility. I had planned on adding fuses for DC, but I didn’t really considered breakers. I’ll look into it. Yeah, those Magnum inverter/chargers are lovely...but ouch. It hurts my wallet just to look at them. Of course, I haven't heard anything but positive comments about the quality. I'd rather have something reliable, at the end of the day.

flboy wrote:The Converters usually also charge the battery. That is the main purpose of having it if you have batteries. I have not seen an Inverter that charges a battery. If it does, it is wasting power converting DC to AC to convert back to DC to charge the battery? That would be strange?

Yeah, the inverters in my OP also have quality battery chargers built-in and can switch between providing AC power from shore/generator to battery-powered AC, depending on if AC power is available coming into the system. Unfortunately, any time we charge batteries from AC then use AC devices later, we lose efficiency with converting from AC to DC, then DC back to AC, whether we use a converter or inverter to charge the batteries.

Since I know I can charge batteries from an inverter, the question was more about why do I need a converter? Since I won’t be using shore power or anything other than my battery system to run DC, what exactly is the converter going to do for me?

Maybe I’m looking at it all wrong, though. Maybe it’s better (cheaper?) to use a converter with built-in charger to take care of my batteries. Then I can get a inverter without a charger built-in and lower the total cost.
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Re: Inverter, converter or both?

Postby MtnDon » Sun Jun 19, 2016 9:54 am

Since I know I can charge batteries from an inverter, the question was more about why do I need a converter? Since I won’t be using shore power or anything other than my battery system to run DC, what exactly is the converter going to do for me?


IMO, given the proposed use pattern a converter is superfluous if you have / want to use an inverter / charger.

FYI, the charger in an inverter / charger takes AC input and uses that to charge. The unit has a built in auto switch so it never uses DC to produce AC when there is an AC source (generator / shore, whatever) connected. The AC input passes directly through to the AC output. I am not sure about the units linked to, but some inverter / chargers have programmable DC output in the charger section. That is the amps to the battery can be limited to suit the battery or the use.
Our 6x12 deep vee nose cargo trailer camper conversion... viewtopic.php?f=42&t=58336

We have a small off grid cabin we built ourselves in the NM mountains; small PV solar system; 624 watts PV, Outback CC & inverter/charger ... http://countryplans.com/smf/index.php?topic=2335.0
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Re: Inverter, converter or both?

Postby kenaxelds » Sun Jun 19, 2016 12:41 pm

MtnDon wrote:IMO, given the proposed use pattern a converter is superfluous if you have / want to use an inverter / charger.

FYI, the charger in an inverter / charger takes AC input and uses that to charge. The unit has a built in auto switch so it never uses DC to produce AC when there is an AC source (generator / shore, whatever) connected. The AC input passes directly through to the AC output. I am not sure about the units linked to, but some inverter / chargers have programmable DC output in the charger section. That is the amps to the battery can be limited to suit the battery or the use.


Thanks again, Don. I've been working my way through your cabin build for the last week or so (I think I'm only about halfway through it). Having the photos and descriptions together is just SO awesome to see. I appreciate it.

As for the converter question, I think you just surmised what I was suspecting but couldn't verify. I converter sounds great if I need to run my 12V systems from AC power, but I don't think I'll have much opportunity to do that. I've learned that I definitely want to be able to program the charger on the inverter to maintain good battery health. A month ago, I was pretty ignorant about solar and RV power systems. I'm definitely learning, but I still have a long ways to go. (I plan to make "superfluous" my word-of-the-day.)

I appreciate everyone's candid comments and ideas. Thank you, all!
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Re: Inverter, converter or both?

Postby flboy » Mon Jun 20, 2016 7:16 am

I am still a little confused. What type of inverter do you have that charges a battery? I know the have all in one inverters/converters /chargers.. but I have never heard of an inverter that charges a battery. Typically the inverter runs off the battery? Just curious. Thanks.

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Don (Flboy)

Current Build CTC:
viewtopic.php?f=42&t=65498
Old CTC Build (sold)
viewtopic.php?f=42&t=50647
YouTube Videos of Finished Trailer:
https://www.youtube.com/watch?v=FASF-x9ofMY - Interior
https://www.youtube.com/watch?v=wb-pvBbyyBs - Exterior
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