Inverter

[LOG]

Frank, throughout this thread you keep coming back to running the inverter with the alternator with the engine running. Why don't you just tell us what you want to operate with the inverter with the engine running?

[Frank Dumlao]

Log, I want to run everything except the AC for now...and maybe if possible with Solar and a Micro-Air “Easy Start” installed on my AC I may be able to run Everything including the AC...will that be possible? If not, say why.

[LOG]

First off, I am not an electrician. But, it is possible to run coach air conditioning in a motorhome while running down the road. There are motorhomes that are currently doing that very thing. The thing that they seem to have in common are large alternators or engine driven generators, large inverters, and large battery banks. Two group 31 batteries would only be considered a large battery bank if someone compared it to one group 24 battery. In other words, in my opinion, what you are trying to accomplish is going to be limited by the size of your battery bank. Now, without the air conditioner, your 220 amp alternator, 3000 watt inverter, and two group 31 Lifeline AGM batteries will power the other appliances you mentioned while running down the road. And, for a short rest stop, without the engine running. And, you will need to use energy management, the same as if in a campground and on shore power. You will probably not be able to run large draw items such as electric water heater and microwave oven at the same time.

[Sbrownstein]

Bottom line is that the alternator doesn't run the inverter, it doesn't even know there is one. What it does is try to keep the battery voltage above some setpoint, generally 14.2 to 14.5 while the engine is running. If it sees the battery voltage sinking, it will try but eventually, if you are drawing enough (200 amps or so) the voltage will sag lower than 14.2 volts. No harm, just like trying to charge a dead battery. In that case the alternator is trying to backfill what you are drawing but will come up a little short. No problem, if the load drops it will catch up.

I can't imagine running an electric water heater with the alternator! AC, well you can try. 2000 watts is about what the AC needs...might work, might not!

Personally, I run my 5500 watt generator under those circumstances and give my inverters a rest. Besides, I have a 50 amp coach...

[LOG]

Originally Posted by Sbrownstein

I can't imagine running an electric water heater with the alternator! AC, well you can try. 2000 watts is about what the AC needs...might work, might not!
...

I agree about the water heater and the AC. However, the OP said everything. The water heater will draw about 10 or 12 amps. But, it will heat up fast and then cycle. It will not have a large start up draw like an AC. I personally would not do it. But the OP asked if it was possible. On my coach, 2000 watt inverter and 225 amp batter bank, the water heater and AC are not on the Inverter circuit.

[nothermark]

Originally Posted by Frank Dumlao

Log, I want to run everything except the AC for now...and maybe if possible with Solar and a Micro-Air “Easy Start” installed on my AC I may be able to run Everything including the AC...will that be possible? If not, say why.

More or less what SBrownstein said. The problem is your power budget. Your alternator has to supply a reasonable amount of power to the vehicle to run it then you want to load it further to run the house loads. The continuous duty loads like A/C's will both overload the alternator thus sucking more fuel via the engine and shortening alternator life. Your battery charge level will drift down at a rate depending on the amount of overload. Bigger batteries will just slow down the drift. You are better off running your generator and letting the engine alternator take care of the engine.

[harryn]

Originally Posted by Frank Dumlao

Log, I want to run everything except the AC for now...and maybe if possible with Solar and a Micro-Air “Easy Start” installed on my AC I may be able to run Everything including the AC...will that be possible? If not, say why.

Not sure if this answers your question or not but perhaps it helps with the thought process.

The MB upfitter manual I think recommends that "auxiliary power demands" be limited to 40 amps, although some people do set them up for 80 amps.

40 amps x 12 volts = about 400 watts
80 amps x 12 volts = about 800 watts

Those numbers are possible at cruising speed, not at idle.

[harryn]

It is also possible to purchase an auxiliary alternator that fits on the opposite side of the engine. It goes in the location where the secondary air conditioning compressor would go for rear air conditioning on the roof if you had that option.

The auxiliary alternators can provide 200 amps, sometime more if driving down the road.

200 amps x 12 volts = 2000 watts

Depending on how much stuff is on the roof of your van, sometimes it is possible to get from 200 - 400 watts of solar panels up there. That can "contribute" to the total power available for use, but not at the 100% availability of power that can be provided by the engine.

[harryn]

There are three methods of pulling power from alternators to charge up batteries:
- More or less an uncontrolled one, just a wire connecting the batteries together and perhaps an auto disconnect switch.

This sort of works, but there is not any limiting of the current and it doesn't provide a path to correctly charging the house battery pack.

- Battery to Battery charger

These provide a controlled amount of current flow (maximum anyway) from the alternator / chassis battery to the house battery.

They are available in various current ratings and you just buy the version you like.

- The other approach works very well but is too controversial for this crowd.

Assuming that you purchase the 40 amp version, it will attempt to pull 40 amps from the alternator and charge the house battery. The actual current will depend on the state of charge of the house battery as this varies depending on charge state.

[harryn]

Originally Posted by Frank Dumlao

harryn, thank you for your response. I just ordered a Go Power ISW3000 to be installed in my RV. Mid State RV here in Georgia is going to do the complete installation. I know the Go Power ISW inverters are new on the market but I read they were good. I hope I did the right thing...thanks again to all members that made a comment!

I read the manual and specs on that inverter. It is kind of difficult to tell from the information provided if it can run inductive loads (motors) or not.

Usually inverters that can run heavy inductive loads (motors) cost about $ 1 - 1.50 per watt and those that cannot cost about $0.50 per watt.

In other words, a 2000 watt inverter that is really a solid 2000 watt inverter, capable of running a heavy motor will cost closer to $2000 - 3000.

Inverters designed for running a microwave might cost 1/2 of that.

[kellylipp]

Originally Posted by Frank Dumlao

How many amps does the Sprinter alternator send to the house batteries while the engine is running or driving(charging)?

With relatively discharged batteries I would see around 70A from the alternator into the batteries while driving.

I think one can worry this all to death but with a pair of decent batteries and the engine running I think you can power a reasonable load say up to 1500W for a reasonable amount of time without smoking anything! I had the MSW 1200W magnum in previous rig and have the PSW 1000W magnum in my current rig and run one at a time 750W coffee maker or 750W toaster with no problems. Wiring in my coach is 2/0 from batteries to inverter.

Had 2000W PSW Magnum in fifth wheel with four heavy duty 6V batteries. That was a goer. Ran microwave easily. Would not have done that for long with only two batteries, but again using reason you will be fine.

As for install: does your current coach have an inverter? Easy if so not so easy if not.

[Jheiser]

I know this post is rather dated but I thought I cold add some value to the discussion.

For the past 2 years I have run the following in my 2009 Sprinter ERA. I currently have 525 ah worth of house battery storage, 400 watts of solar on the roof and a 5000 watt inverter. I also have an onboard Onan 2500 generator that I seldom use. My setup provides power to my 120V ac refrigerator, microwave, water heater, coffee maker, blender (occasionally), wife’s blower drier and curling iron, computer, phone and camera chargers and 120v ac TV and I might have missed a few things. Regardless, over the past two years I have not had any issues with not having enough power. Most times we are disconnected and remote and like I said power is not an issue.

We have had NO alternator issues - the house batteries will also charge from the alternator if we have no sun and when we are heading down the road at night. The secret is knowing what your power consumption is, what’s your biggest power consumer and how often you plan to use the biggest power consumer. We can actually run our AC for anywhere between 1/2 hour to 45 minutes straight off the inverter. The trick to inverters is if for example your refrigerator runs off ac, when it starts it will require more than once it’s started and running - it peak watts. If that peak is 1500 watts and your inverter can only handle 1000 watts peak and supplies a steady 750 watts you would need a bigger inverter. Another example is most air conditioners have between 2500 and 3500 peak watt s at start up but sett down and run some as low as 500 watts depending on the size and efficiency of the unit.

In order to determine how many watts your 200 amp alternator could handle if directly connected you need to do some math - watts = amps x volts. For example say you really only have 180 usable amps for your directly connected inverter. 180 x 12 = 2160 watts.

[festrvl]

Hard to believe that it's taken this long to mention solar charging in this scenario. Seemed like a no-brainer from the start.

[Jlo11111]

I have a 2000W inverter with 200ah lithium. Everything (except the AC), including the microwave, water heater, fridge, etc. runs just fine off of battery power. My van has a 180W alternator. As long as you have adequate battery capacity to should be fine.