Aircon from Inverter from Batter Charger

[rourkeh]

"Agility" to answer one of your questions, Is there a reason not to power a 16,000 BTU aircon from a Battery Charger -> Inverter -> Aircon?
It is possible to run an A/C unit from a house bank through an inverter. I have this set up on my boat for times when I want to run one 16,500 btu A/C unit at night and not run the generator. I have 1,000 ah of power in the house bank that makes this possible. Also as someone else mentioned the compressor start up draws a lot of amp load so I put Dometic soft start units on both my A/C units which helps get around this problem. Without the soft start units you are going to need a huge inverter.

[44'cruisingcat]

Originally Posted by Agility

I'm designing a boat to be used on Euro and US shorepower. I like the Mastervolt battery charger that accepts shore power at 120/60 and 240/50. If I use that to power an inverter, is it safe to run the battery charger and inverter all the time to power all the AC devices?

Is there a reason not to power a 16,000 BTU aircon from a Battery Charger -> Inverter -> Aircon?

Both the charger and the inverter have the wattage to support this with 2x room to spare.

Wouldn't this design be safer, since the power only comes in directly to the battery charger?

Wouldn't it be more robust since the inverter would take power from the batteries if there wasn't quite enough power from shore?

What am I missing?

16,000 BTU is about 4700 Watts. At 12 volts that's 391 amps. Do you have a battery charger capable of around 400 amps continuously?

IMO it would be much safer and more robust to simply plug your A/C directly to shore power. Having invertor cables handling up around 800 amps (on startup) and chargers handling 400 amps continuously seems risky to me.

[twistedtree]

Agility, what you are proposing is exactly how I'll supply 120V/60hz on my boat using word-wide shore power voltage/hz, and is how many other Nordhavns do the same thing. As you say, it's a poor-man's ASEA or Atlas power converter, and if the power levels are low enough it's a very good approach. You can plug into any flavor shore power, and always have 120V60hz on-board.

Things to watch out for, most of which have been covered, are:

1) If you lose shore power you risk draining your batteries down, perhaps very quickly. You probably should figure a way to protect against this. Most inverters can be programmed with a low voltage cut out so they shut down if the battery voltage gets too low. You could set this to a much higher than normal voltage so the inverter will shut down if the charger stops and can't maintain a high battery voltage. However, this will cause the inverter to shut off much sooner than otherwise (perhaps prematurely) when you are intentionally running off batteries. Also, when your inverter loads exceed your charger capacity (AC and cook top running) your battery voltage wil begin to drop and again risk shutting down the inverter. Hopefully with some experimenting you can find a setting that works for you.

2) You might consider doubling up the chargers. Then your inverter can't draw more than the chargers can supply, and the chargers will always have extra power to actually charge the batteries.

3) Consider making the boat 24V rather than 12V. It will reduce the size of the cables and cut all the current in half.

4) Efficiency is the price you pay with this double power conversion. Your 20% number is probably a good one, and it will generate heat where ever the equipment lives. Waste heat is the biggest complaint I've heard about ASEA and Atlas systems.

5) Speaking of efficiency, you might consider running straight off shore power when it's 120V 60hz, and avoid all the conversion losses. Most inverters have the bypass switch built in, so it's just a matter of wiring things up properly.

6) Again speaking of efficiency, keep in mind that your 30A shore power drops to 24A onboard once you factor in the 20% losses. At that point your are down to 2880W available to consume onboard.

[impi]

Originally Posted by Agility

I'm designing a boat to be used on Euro and US shorepower. I like the Mastervolt battery charger that accepts shore power at 120/60 and 240/50. If I use that to power an inverter, is it safe to run the battery charger and inverter all the time to power all the AC devices?

Is there a reason not to power a 16,000 BTU aircon from a Battery Charger -> Inverter -> Aircon?

Both the charger and the inverter have the wattage to support this with 2x room to spare.

Wouldn't this design be safer, since the power only comes in directly to the battery charger?

Wouldn't it be more robust since the inverter would take power from the batteries if there wasn't quite enough power from shore?

What am I missing?

We run 2 x 16000 BTU air cons on the boat as well as a 5000BTU next to our bed.
We use the genset to run all the units to cool the boat down just before tucking in for the night … turn off the genset and run the 5000BTU during the night to keep our cabin cool.
It really works well for us - Webasto units 220V - 50 hz

We run the unit through our two victron inverter chargers.

Sadly, I have to admit we made a huge mistake 'UPGRADING' our Deep Cycle Exide Gel batteries to AGM LifeLine batteries … there is no comparison - AGM LifeLine batteries are not proving to be anywhere close to the deep cycle gels which had a lot more voltage left in them after a night using the aircons. Still - it is great to have aircon running from the house banks at night!

[valhalla360]

Originally Posted by 44'cruisingcat

16,000 BTU is about 4700 Watts. At 12 volts that's 391 amps. Do you have a battery charger capable of around 400 amps continuously?

IMO it would be much safer and more robust to simply plug your A/C directly to shore power. Having invertor cables handling up around 800 amps (on startup) and chargers handling 400 amps continuously seems risky to me.

I believe your amp calculation is off.

We have a 12,000btu unit and while running, it draws around 9 amps at 120v which would translate to around 110-120 amps 12 volt factoring in some losses. The jump to 16,000 btu would only take you up to around 150-160amps. A big charger admittedly but they are not hard to find in that size.

I believe your error is the A/C unit is essentially a heat pump. The electricity doesn't "create" cold, it pumps it from the water to the interior air. Hence it is much more efficient than your calculation suggests. (I'm sure someone will correct my explanation of thermodynamics)

[BambooSailor]

On my last boat I actually did what you plan. The difference was that I used separate charger that accepted wide range of A/C voltage/frequency, even from low quality sources, as often found around the world. I used cheap Xantrex 2000W sinewave inverter (Xantrex PROwatt SW - back then I could have bought something like 10 of them for the price on one mastervolt charger/inverter) and used it to power 16000 btu aircon unit (Webasto FCF) that starts slowly and therefore does not need big starting current. It worked like a charm, even in reverse cycle heat mode. My 2 cents...

[BumbleClan]

Hello:

I am new to the forum, and just want to check if anyone used "Chilipad" before, and what's the experience.

This is a mattress padding with circulating water, and the water is cooled or heated by a semi-conductor heat pump. It runs at 110/220 VAC, and very small current (80 or 800 mA), so can be run off an inverters. In fact I suspect it runs on DC, but you need to open the box to modify it, and that voids warranty. The web site is Cooling Mattress Pad (also Heats!) ~ ChiliPad

I live in a hot country with no marina docking. The only way I can run aircons would be using generators, and this Chilipad may be the answer for me.

Sorry for jumping in this forum on Air Conditioning, but it may be an interesting alternative.

[FlyingCloud1937]

The.

REAL ANSWER is, the one that runs the least amount of time to fulfill your load requirements.

It's really that simple.

First you must apply the Law of Conservation; to attain that realm.

That law is steeped in use as well as performance.

Performance is a design criteria.

Now to achieve the design, is the real issue.

Lets say you have to run your AC generator, every-time you run your AirCon. The start up load of the Air-Con is 2-4 times the running load.

Why not have a Hy-bred system that is DC based/with an engine driven AirCon.

Then marry that with a bat bank and an inverter with an DC Gen, that is auto-start. It will require 2 compressors.

By program the bats run the AirCon until they can't, then the gen starts and takes over the AirCon and charges the bats.

Lloyd

Originally Posted by Agility

I'm designing a boat to be used on Euro and US shorepower. I like the Mastervolt battery charger that accepts shore power at 120/60 and 240/50. If I use that to power an inverter, is it safe to run the battery charger and inverter all the time to power all the AC devices?

Is there a reason not to power a 16,000 BTU aircon from a Battery Charger -> Inverter -> Aircon?

Both the charger and the inverter have the wattage to support this with 2x room to spare.

Wouldn't this design be safer, since the power only comes in directly to the battery charger?

Wouldn't it be more robust since the inverter would take power from the batteries if there wasn't quite enough power from shore?

What am I missing?

[valhalla360]

Originally Posted by FlyingCloud1937

The.

REAL ANSWER is, the one that runs the least amount of time to fulfill your load requirements.

It's really that simple.

First you must apply the Law of Conservation; to attain that realm.

That law is steeped in use as well as performance.

Performance is a design criteria.

Now to achieve the design, is the real issue.

Lets say you have to run your AC generator, every-time you run your AirCon. The start up load of the Air-Con is 2-4 times the running load.

Why not have a Hy-bred system that is DC based/with an engine driven AirCon.

Then marry that with a bat bank and an inverter with an DC Gen, that is auto-start. It will require 2 compressors.

By program the bats run the AirCon until they can't, then the gen starts and takes over the AirCon and charges the bats.

Lloyd

In theory a hybrid system would be great. The problem is mating a generator and an inverter to run an air/con is an expensive proposition since since you move into the realm of specialty equipement.

There are a number of options but all get pricey very quickly for a small cruising boat:
- If you just wire up a generator and invertrer in parallel, you will likely fry your air/con as the 60hz will likely be out of phase. There is an inverter that can take shore power/generator power, match the phase and combine but last I checked, it was several thousand.
- You could try to go pure DC but then your air/con and generator are are specialty items. The cost goes up and servicing becomes an issue. Plus you still need an inverter if you want to run other AC loads.

[rjtrane]

Flying Cloud's idea has merit. But, using two compressors would be an A/C nightmare to engineer and maintain.

Instead, stop just short of the double compressors and use "off the shelf" items readily available:

1. Build the biggest battery bank within the budget and space/weight limitations. LiFePo if desired would be preferable and more economical over the lifetime of the battery.
2. One or two inverters (2 for 220v/60 Hz) with plenty of capacity for your AC and A/C needs.
3. Variable speed, DC generator with auto start/stop.
4. Alternator(s) from drive engine(s) to battery.
5. Some solar as space/budget allows. Ditto wind.
6. Dedicated shore power charger that works on ANY world shore power.

This is a system that is easier to use than most "normal" ones found on yachts. No switching is ever required during use. All AC is inverted and always readily available. No resetting the clock on the microwave - EVER!

[roetter]

Originally Posted by valhalla360

In theory a hybrid system would be great. The problem is mating a generator and an inverter to run an air/con is an expensive proposition since since you move into the realm of specialty equipement. There are a number of options but all get pricey very quickly for a small cruising boat: - If you just wire up a generator and invertrer in parallel, you will likely fry your air/con as the 60hz will likely be out of phase. There is an inverter that can take shore power/generator power, match the phase and combine but last I checked, it was several thousand. - You could try to go pure DC but then your air/con and generator are are specialty items. The cost goes up and servicing becomes an issue. Plus you still need an inverter if you want to run other AC loads.

The Victron Multi Plus ones have power assist and another one that I forget the name for. Works like this.
Your generator or shore power runs through the inverter/charger. You set the maximum amps the shore or generator can supply.
When power comes in it will be passed through. The charger will be running at full amps.
Once the used amps come up to the maximum shore or generator amps the charger throttles back.
If the required amps go higher than the shore/generator can supply, the charger goes to zero and the inverter adds additional amps. Very good for inrush systems such as AC motors or dive compressors. The generator can be quite small yet you are still able to start a big load.

[valhalla360]

Originally Posted by roetter

The Victron Multi Plus ones have power assist and another one that I forget the name for. Works like this.
Your generator or shore power runs through the inverter/charger. You set the maximum amps the shore or generator can supply.
When power comes in it will be passed through. The charger will be running at full amps.
Once the used amps come up to the maximum shore or generator amps the charger throttles back.
If the required amps go higher than the shore/generator can supply, the charger goes to zero and the inverter adds additional amps. Very good for inrush systems such as AC motors or dive compressors. The generator can be quite small yet you are still able to start a big load.

Have the Victron units come down in price recently? They are a great idea but last time I checked, we could run the generator for several years for the cost of a Victron.

[roetter]

Originally Posted by valhalla360

Have the Victron units come down in price recently? They are a great idea but last time I checked, we could run the generator for several years for the cost of a Victron.

I paid $1800 for a Multi plus 3000. There are 3 significant savings you get from paring a Multi plus with a generator.
1. You can reduce the size of your generator quite a bit as it will not stall on the high inrush currents to start the AC compressor motor. The smaller generator will cost less, which can be spent on the Multi plus.
2. Because the generator is not oversized, as when sized for the high inrush currents, it will be better loaded and live a lot longer. If the generator is running a low loads for long times you will get bore glazing and it will die a premature death.
3. You are saving weight and space on your boat.

[s/v Jedi]

Hear hear, somebody who understands this!

People who buy "cheap" take a long time before they realize they actually spent more than those who buy the good stuff

Originally Posted by roetter

I paid $1800 for a Multi plus 3000. There are 3 significant savings you get from paring a Multi plus with a generator.
1. You can reduce the size of your generator quite a bit as it will not stall on the high inrush currents to start the AC compressor motor. The smaller generator will cost less, which can be spent on the Multi plus.
2. Because the generator is not oversized, as when sized for the high inrush currents, it will be better loaded and live a lot longer. If the generator is running a low loads for long times you will get bore glazing and it will die a premature death.
3. You are saving weight and space on your boat.

[botanybay]

Yes, I am doing the same on a bit larger scale...

Victron isolation transformed (automatic voltage selection 240/120) at 3600 watts

Victron skylla-i 100 amp @28v charged

Victron quattro 8kva

6kva 50hz / 8kva 60hz westerbeke generator currently 230v 50hz configured.

Mode 1) 32 amps 110/60hz, 16 amps 208 60hz, 16 amps 240 60hz, 16 amps 230 50hz input

Battery charger makes 100 amps at 28v consuming 3500 watts max

Inverter makes 230/50hz to 8kva continuous (average over time less than battery charger can provide)

If generator running can add an additional 5kva (80% of 6kva)

Mode 2) 110/60hz, 240/60hz, 230/50hz input

3600 watt Isolation transformer to shore input of quattro

Available power 8kva + 3.6 kV a

Battery charger off.

Generally run in mode 1, there is an efficiency hit but boat is running native voltage and frequency.

If need higher peak than inverter can handle then either start the generator or switch isolation transformer output from charger to inverter.

Interestingly max power has shore power to charger and generator to the inverter at the same time.

Most of the equipment on the boat is 50/60 hz comparable and will run down to 208 and be within spec, the microwave and washer/dryer being the exceptions.

Currently installing system which is requiring a significant upgrade to the DC infrastructure. Upgrading the ac system to modern specs (already had elci's but having to add some additional circuit protection for new equipment)

Overall a fun project, hope to have fully operational before first club cruise of the season (easter)