Inverter vs Inverter Charger

In the course of planning a solar system with 3 -325watt panels and 4 225 amp hr 6 volt batteries, 2s 2p, I originally intended to install a 2000watt 12 inverter with an auto transfer switch. In the course of shopping and learning, a Victron 3000watt / 100 amp Inverter Charger unit was recommended. Lots of bells and whistles.  Another vendor recommended a Spartan unit of similar capacity but less bells an whistles and less $.  The 3000 watt capacity seems excessive for the battery bank but I have no experience with this. 
Our 2010 Winn. Vista is currently equipped with a 300 watt inverter and a converter of unknown capacity. 4kw Onan.  I will be installing a Victron battery monitor in the next few days. 
Is this overkill? Worth the ~ extra $350? Any thoughts appreciated. 
Thanks
Pat

Nice solar set up 3 big panels!

What is the load you'll be running? If you intend to run a residential fridge, microwave and misc. (tv lights, etc.) then I'd go with the 3000 W (pure sine, I would hope). Having the 100A charger is good for getting the batteries back up quickly. You should also use a automatic generator start module (unless it's one of the bells and whistles). With the AGS, the generator will start and charge the batteries automatically as a supplement to the solar when you don't have shore power - it will most likely also start the generator when your A/C wants to come on (sweet convenience).

You can always add more batteries when you want to (I'd suggest two more at some time - not knowing your intended load).

Your are on the correct path - don't pinch a penny at this point.

I think either inverter would work fine with the battery bank you're getting, but whether or not the Victron's extra thousand watts, or extra features would be worth the extra money is pretty subjective. Victron has a pretty good reputation though.

I don't know what the charge rate is for the Spartan system, but neither it nor the Victron charger will be able to charge at a 100 amp rate with your solar output...  from shore power and the genny's output yes, but the highest charge rate you're likely to see from 975 watts of solar is 50-55 amps on a good day.

Our coach came from the factory with an AGS feature, and we used to use it quite a bit. Since getting solar six years ago, however, it's never come on once. In fact, I've stopped enabling it, because our solar keeps the batteries charged so well that the AGS low voltage threshold is never reached. Pre-solar, I would have added an AGS system. Post-solar, I wouldn't, because it just doesn't seem to be needed anymore. FWIW

Kev

For those occasions when you have shore power what converter do you have.

Most inverger/chargers are darn good top end 3-stage chargers (can't speak to all but all the ones I've seen are) programmable set points on the charge side and more.

On the other hand not all converters are that good.    But some are. and that's how I choose.

My RV came with a Progressive Dynamics Wizard controlled converter (BEST!) so I use it and tend to disable the inverter's module. but it's nice having a back up.

Kevin thank you for your reply.

I don't know what the charge rate is for the Spartan system, but neither it nor the Victron charger will be able to charge at a 100 amp rate with your solar output...  from shore power and the genny's output yes, but the highest charge rate you're likely to see from 975 watts of solar is 50-55 amps on a good day.

I think this corresponds to one matter of my confusion. I thought the Inverter Charger would function as a charger controller for the solar panel array. After speaking with an Arizona Wind and Sun customer service rep I understand the charger function converts shore power or genset power to 12 volts to charge the batteries but does not function with the panel array power. This is not a commercial but; the Northern Ariz. Sun and Wind reps seem  knowledgeable and willing to help a newbie,  the Victron line  capabilities are impressive. I would still need a separate charger controller.

The figure of 50 to 55 amps ~630 watts follows my thoughts. Designers seem to size charger controllers based on the full capability of the panels under perfect test conditions. The Victron 150/60 states a max panel array of 850 watts. What is the chance of the 960 watt array producing 960 or even 850 and what is the potential harm?


Our coach came from the factory with an AGS feature, and we used to use it quite a bit. Since getting solar six years ago, however, it's never come on once. In fact, I've stopped enabling it, because our solar keeps the batteries charged so well that the AGS low voltage threshold is never reached. Pre-solar, I would have added an AGS system. Post-solar, I wouldn't, because it just doesn't seem to be needed anymore. FWIW

The owner manual devotes a large section to the Onan 4kw gen. I have not read it in detail and do not know if the AGS feature is there yet.

This all seemed straight forward when I started and now It seems the more I learn the more I don't know.
Thanks,
Pat

One consideration seldom mentioned in choosing an Inverter is its standby current draw. This is the amount of battery power used by the inverter just to have it on even when not powering a load. Generally the bigger the inverter (in watts), the larger the standby current.

This wasted power lessens the power available from your battery bank and must be replaced by your solar panels.

Tom's right. I didn't think of that, because our coach has a large residential fridge, and it's always drawing more power than the sleep (I.e. standby) threshold for our inverter. The 50-55 amps I mentioned comes from experience. We've got a 960 watt array, with 8 gauge wire running from the panels to a rooftop junction box, 4 gauge wire going from the junction box to the solar controller and 2 gauge wire going from the controller to the batteries, so there's very little voltage loss.

We've got an Outback Flexmax FM-80, 80 amp solar controller, but I could have gotten by with a 60 amp controller. I say that, because the most power we've ever seen generated by our solar array is 56 amps. It's normal to see 50 amps, mid day. You're going to want an MPPT controller (vs a PWM controller) because MPPT controllers have the ability to convert excess voltage to amps. PWM controllers can't do that. When it comes to recharging with solar, it's all about putting amps back into the batteries.

Your planned array is similar to the size of ours, and I think you'd be fine with a 60 amp solar controller. There a a few good brands out there, including Outback and Morning star - probably others too.

Kev

NOTE: Pat, I forgot to mention that we see 50+ amps mid-day, because we tilt our panels. If they were flat on the roof, like yours are going to be, I think the max we'd see would be roughly 35-40 amps, on a good day. I think you can expect to see that too.

Heli_av8tor said:

One consideration seldom mentioned in choosing an Inverter is its standby current draw. This is the amount of battery power used by the inverter just to have it on even when not powering a load. Generally the bigger the inverter (in watts), the larger the standby current.

This wasted power lessens the power available from your battery bank and must be replaced by your solar panels.

Click to expand...

As Tom wrote about the inverter standby current draw.
Blues Driver,
A 2000 watt inverter, just being on, not powering any 120V devices typically will pull 1.5 to maybe 3 amps.  Note, that 2amps is 48 amp hours (AH) in 24 hours, which is about 25% of of the total usable capacity of your battery bank.

A Winnebago Vista is an entry level RV.  As such the converter probably is not top of the line so may very well be a single stage charger.  This doesn't matter if you are charging from shore power.  However if you charge from the generator you really want a 3 stage charger. 

With almost 1000 watts of solar to charge only 400AH of battery you probably won't need to charge from generator very often. 

I wrote "only 400AH of battery".  Nothing wrong with 400ah of battery, it is not easy to add more than 4 golf cart batteries to most gas motorhomes.

Yes, a 3000watt inverter is over sized for 400AH of battery.  But you are not likely to use the full 3000 watts of capacity. 

For example the microwave will pull about 140 amps of 12V DC (1600-1700 watts).  I have a 4 slice toaster in our RV and it pulls about the max my 2000 watt inverter will handle 170-180 amps of 12V. 

Blues Driver said:

Kevin thank you for your reply.

.........The figure of 50 to 55 amps ~630 watts follows my thoughts. Designers seem to size charger controllers based on the full capability of the panels under perfect test conditions. The Victron 150/60 states a max panel array of 850 watts. What is the chance of the 960 watt array producing 960 or even 850 and what is the potential harm? .................

This all seemed straight forward when I started and now It seems the more I learn the more I don't know.
Thanks,
Pat

Click to expand...

There is no way that I can imagine 960 watts of solar getting more than 60amps at the solar controller..  To even come close you will have to tilt your solar panels toward the sun at noon on a perfectly clear summer day (no haze what so ever in the sky).  There is also the consideration that you will have some power loss from the solar panels to the solar controller.  How much loss depends on how the length and size of the wire coming from the panels to the controller.  It is pretty easy to use a wire size (some what small) so you loose 5% or maybe even as much as 8%-10% in the wiring and connections. 

This all seemed straight forward when I started and now It seems the more I learn the more I don't know.

Click to expand...

For some educational reading:
http://www.marxrv.com/12volt/12volt.htm  This is pretty basic so may be covering what you already know. 

For some pretty technical info about batteries and solar and charging.  http://www.jackdanmayer.com/rv_electrical_and_solar.htm