Critique my electrical diagram please

I see all these diagrams doing around with 2 inverters and I'm wondering if I couldn't get away with just the one. I'm looking at the Xantrax HFS Freedom which also charges and passes through mains AC. This is what I've come up with. Real interested to hear what you guys think of something like this. I'm fresh to the community so please keep that in mind.

I'd like to use those diodes but I can't find any for that load. At some point I may install a second alternator and run AC kitchen loads off that so it would be high. I could use a relay but I can't think of the right arrangement with the powering of the relay so I may not have any which mean I need to build in a manual switch protocol to avoid cross loading.

Sent from my SM-N920W8 using Tapatalk
Last edited:
The photo is not working, but I am unclear why you think you would need two inverters? The only place I can see a second inverter coming into play is if you wanted to charge the house batteries from the chassis batteries while driving down the road. The first inverter powers the second inverter/charger to charge the house batteries.


Robinson Fuso
Usually 2 inverters means one big inverter/charger (sized to charge the battery bank), and a separate smaller inverter for nominal AC loads (like TV, laptop, phones) that don't require 3000W or whatever. If this is your situation, I wouldn't worry too much about it. Size the inverter/charger appropriately for the battery bank, and add point-of-use inverters for small loads that don't make it worth turning on the big one.
Sorry. Photobucket had an issue with third party links it seems. I've fixed my post. I think it'll show up fine now. If not, this is the direct link. Promaster Electrical Diagram Rev 1.jpg

I'm not too worried about having a second inverter but just would prefer to mitigate it for cost and simplicity reasons. Just not sure if a wiring diagram like this would do that given that there are a lot of people out there smarter than me who installed two inverters. Two would indeed be to have AC and charge the battery whilst driving and on mains power with the same device.

Using a DC to DC charger would mean I still need an inverter and an AC charger. Three devices in other words. With an arrangement like this I've got the inverter/charger charge the battery whilst driving and on mains. Pass through mains if needed and provide AC from both DC sources (engine and house battery). That would provide the flexibility to install a second alternator later too. I'm just a little nervous about that three way connection where I've got diodes shown. A: I can't source any for high amp loads and B: putting in a manual switch would increase the margins of error. Is that my I haven't seen a setup like that in blogs?

Sent from my SM-N920W8 using Tapatalk
Last edited:
I'd put a fuse or CB between battery and BlueSea aux. box. I believe that 12 slot BlueSea is rated to carry 100 amp. A circuit breaker also acts as a quick disconnect for all the circuits in the aux....
A couple years ago when I was shopping Charger/Inverters I was all excited about the Xantrax Freedom. Series, after lots of research it seemed like too many people had issues with them. Many of them fail immediately and are replaced under warranty. I figured mine would be the one that failed one day after the warranty expired.
I ended up going with a small Magnum. I had to go with a modified sine wave one to keep it in my budget, but they have a much better track record.
Just my two cents, and this could have changed in the last couple years

Sent from my iPhone using Tapatalk Pro
Credit for the inverter->inverter/charger system goes to Dave Orton. He explains it and has a diagram here: The vehicle powered inverter provides 120V power while driving. This is used to heat water and air and also charge his house batteries via the charger in the second inverter/charger (it's inverter is off). The second inverter is used to supply 120V when parked and to charge using shore power (rarely needed).

Today's AGM house batteries last longer if charged using a specific voltage profile which is usually not what the vehicle alternator is delivering via a traditional combiner relay. The 2 inverter system overcomes this because the charger (in the second inverter) is running on 120V supplied by the vehicle powered inverter. This allows it's output charge voltage to be independent of the alternator voltage so the house batteries are charged according to their own voltage profile requirements.

There are some DC to DC chargers that also provide an independent voltage profile for charging the house batteries. Sterling power, Ctek and Kisae are some that I am aware of.

I can't see the drawing. Cable sizes and the location of fuses and/or breakers are typically what folks struggle with. Best systems will have a shunt and battery monitor that counts amp-hours to determine state of charge (SOC).


Tail-End Charlie
Screw Photobucket. The issue is that they no longer allow linking to pics (3rd party linking) on non-paid accounts. Fine that's up to them, but the way they went about it was shady and underhanded.

Clicking the link to view the pic opens it, but it's surrounded by Photobucket crapola which makes it a PITA to view on a phone.

Just upload the pic here, so it can easily be viewed.

Without actually seeing the pic - yes you can use an inverter to feed a battery charger. The issue that will normally be pointed out as a deal-breaker is the inefficiency of the whole AC->DC->AC->DC multi-step conversion.


In my opinion, the inefficiency is a non-issue. Using an alternator to charge a battery isn't very efficient to begin with and doesn't do a great job of battery charging. Adding more inefficiency, but getting better battery charging, is a worthwhile tradeoff in my opinion.

I have no idea what diodes you are referring to, and won't unless you upload the pic here, but I would guess that you are trying to use one inverter - fed by the engine battery for charging the house battery (and supplying AC while driving), and fed by the house battery while parked.

I can think of a few ways to rig something like that, and I can think of a few possible problems as well.

Right off the top of my head...using a single inverter/charger won't work because an inverter charger can't both suck power in via its battery connection and simultaneously push power out its battery connection. It can do the inverter thing (power in from battery) or do the charger thing (power out to battery) - but not both at the same time.

Let's see the diagram and we can figure out how to do what you want.
Didn't know that about photobucket. Haven't been too active on forums in a while. Sucks that they went that way. How that that hasn't distracted from the intention of this thread at all.

Should be attached below. Added a fuse on the DC out to the fuse box as suggested but it's not shown on this version of it yet.

I've got experience with this on motorbikes (the missing dude thing was an oversight) but on this the equipment is a lot more expensive so looking to just manage with an inverter/charger. I read Dave Orton's and other inspired blogs. Just wonder if that complexity can't be mitigated with a design like this.
The diodes could be replaced with switches too but like I said that would add a margin of error. I also like relays but would need a switched power arrangement which I can't think off.

I take the point on Xantrex and will look into it a bit more.

Sent from my SM-N920W8 using Tapatalk
Last edited:


Tail-End Charlie
The error in the diagram is the separate "DC in" and "DC charge" connections to the inverter/charger.

There is only one DC connection on an inverter/charger.*

There are two AC connections, "AC in" and "AC out", but DC has only one connection - "battery".

As I said, the DC connection can be either...

In (drawing power from battery and suppling power to AC out (operating as inverter))


Out (drawing power from AC in and supplying pass through power to AC out and to battery (operating as charger))

...but not both at the same time.

So as Verstad just more or less said - the diodes and manual transfer switch won't work.

Hence Orton's dual inline inverter setup - one "inverter only" (fed by engine battery) to supply AC to a second "inverter/charger" so the inverter/charger can operate in battery charger mode to charge a house battery.

But that dual inline inverter setup is a bit goofy if you ask me. The rationale behind that setup is based on a couple things, one of which is outright false.

The first reason behind Orton's dual inline inverter setup - which he mentions on his page - is that you aren't supposed to mix different lead-acid batteries when charging. This is false. Lead-acid batteries have to be identical (type, size, brand, age, etc.) if tied into a full-time battery bank. If only tied part-time during charging, they don't.

The second main reason for that setup is so that the charger section of the second inverter can do a better job of charging the house battery than simply charging the house battery from the alternator via ACR or split-charge relay. Well, that's a good reason. However, I don't think it's a good enough reason to justify the added complexity. The "alternator->engine battery->relay or ACR->house battery" setup is simple, reliable, proven and automatic, and will get the house battery charged. Eventually. If you drive enough hours.

And there's the rub. One of the reasons for Orton's setup - again stated on his page - is to limit the load on the alternator. So you can charge from the alternator and it will take a long time. Or you can feed a good charger from an inverter fed by the alternator to get a more precise charge to the battery, which should take less time. But if you limit it too much, it won't save enough time to make the whole complex rig worth the bother.

Ultimately, Orton has other reasons (supplying various AC loads), which might justify the complexity of the dual inline inverters, but I wouldn't go about it the same way...

If the second inverter (from the house battery) is big enough to supply the AC loads from the house battery, then I would just rig it to do that all the time.

Then the only issue to be solved is charging the house battery. The most common way to do that is either, A) a split-charge relay, B) Automatic Connection Relay (ACR; split-charge relay with a brain) or, C) B2B (battery to battery) charger.

The B2B will do the most precise job, and cost the most. If it's big enough, it will even do it faster. But lead-acid batteries are not precise electronic devices. They are sloppy chemistry experiments in a plastic box. Great precision in charging normally isn't required.

*[There are of course exceptions to every rule. Some inverter/chargers do have additional DC connections. Commonly they might be for something like "solar in" or "battery bank #2". But none have the ability to both suck battery power and push battery power simultaneously.]
Thanks for the review. Looks like I overestimated the inverter/ charger's capabilities. That sucks. Could have sworn it had a secondary DC output but guess not. Maybe a bad time of year to design this. :-(
I understand what you're saying. I do like the idea of providing a decent charging profile to the house battery. I may have to rethink my AC needs though.
I see CTEK offers a DC system which looks interesting also.

Sent from my SM-N920W8 using Tapatalk
Let's try take 2. I've decided to get rid of AC needs and keep it simple. I do like the idea of those Sterling chargers though so I've added that.
Not sure if I'm providing too many fuses. Might be able to get rid of the one between the switch and the battery.

Sent from my SM-N920W8 using Tapatalk
Am attaching an power system schematic I did for a project I am working on. It's overkill for what you are trying to do but it should give you an idea of how an integrated system is put together.
The entire system is based on Victron components and has a control/monitor panel that interfaces with all the components. I did not tie the system into the vehicle alternator/battery system.
Victron has a buck/boost converter specifically designed for that function.

I am not affiliated with Victron in any way, they just make good stuff.

Hope this helps,