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Small Cabin Forum / Off-Grid Living / inverters, inverter w/chargers
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bronco_ed
Member
# Posted: 22 Aug 2017 16:39
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In looking to put together a system and possibly in incremental steps (if possible) I would like some help in understanding just how an inverter with a charger works.

I realize that some inverters have the potential to detect and handle multiple voltage 12,24,36,48 and convert to AC power.

However when it comes to charging... Would the inverter allow the use of an AC source to charge the batteries? (Can It be used as a charger without using solar)


Thank you,

-Ed

pizzadude
Member
# Posted: 22 Aug 2017 17:26
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Yep.
You can safely connect an AC charger to your bank in parallel with your solar connection.
I always lift one side of the fuse from the solar charger to prevent backfeeding the charge controller, though probably not necessary...

bronco_ed
Member
# Posted: 22 Aug 2017 20:22 - Edited by: bronco_ed
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I have to put in a good word for CNBOU, I emailed a question about the inverters/chargers they carried and i received a response in about 30 seconds.

We exchanged a few emails...

I left extremely pleased with the customer service.

They make a 1500watt inverter/charger in 48v however it is not listed on their site. I can order directly via email.

I think it may be cost effective for me to buy the inverter/charger over a
separate battery charger for the 48v batteries packs. (Although an actual charger may charge faster)


Is there a formula for figuring out how long a battery will take to charge at a given amount of amps? (Maybe I should start searching the site ;)


This would definitely allow me to move forward in steps...

Thanks

Steve_S
Member
# Posted: 22 Aug 2017 21:25
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And Inverter/Charger which can take in 120v or 240v from a generator is a better option... They have added modes for battery charging which car chargers do NOT. The kick is, to ensure the Inverter/Charger is capable of handling the batteries you use... not all do LiIon but I think all do FLA, AGM/Gel...

Often the Inverter/Charger combo is for RV's & Marine use that have "shore power" i9nput (ie a generator or grid power).

creeky
Member
# Posted: 22 Aug 2017 22:08 - Edited by: creeky
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I just got back from a Victron installation course. What a great program.

Edit.

Also. Remember to calculate your amps. If you have a 200 amp battery pack and discharge to half you have to replace 100 amps.

With lithium if you have a 15 amp charger you can expect 8 hours of charging time. There will be some losses. Not on the battery side but on the charger.

Victron chargers allow you to set charge voltage, time and max charge rate. So even a 30 amp charger can be set lower.

This is useful depending on your charge source. If your shore power is 15 amps at 120 you don't want to try to charge at 30 amps. If you have a small genny you don't want to run it flat out for 8 hours. Better to turn the charger down.

So match your voltage. Your amps. And your charging power source.

One thing about separate charger/inverter is if you do have one go down. You don't lose both.

Good luck.

Willie1959
Member
# Posted: 23 Aug 2017 08:17
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Been off grid for years rule of thumb is for every 100 amp hours of battery it will give you 1kw of power down to 50 % of discharge. I have a 600 amp hour battery bank so it will allow me to safely discharge 6 kw of power from full charge. I commonly turn on my heat pump at 4am to warm the cabin when it is cold . Get electric blankets they save batteries and money. Get an inverter /charger, personally I like Outback units they are fully Automatic , set your battery settings, max charge current for your charger and use the automatic start for your generator as well. Get a separate battery charger as well. I use a 24 volt forklift charger they are fully automatic and are built for industrial use every day. Do not be affair to use your generator its cheaper than batteries. I have three, two small units and an 4500 watt Onan for winter use. If you are at all handy get duel fuel units or have them converted as propane is cheaper than gasoline here in Ontario. .65 to .90 cents per liter vs premium fuel check KIJIJI I buy everything there

Willie1959
Member
# Posted: 23 Aug 2017 09:02
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propane facts

Willie1959
Member
# Posted: 23 Aug 2017 09:04
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Propane Consumption Rate
First thing to keep in mind is that the estimate given by the manufacturer for the gasoline run time can be used for propane also because it is just that; an estimate or guess. Propane only has about 10% less Btu content than gasoline gallon-to-gallon, so the estimate used by Yamaha for gasoline consumption will be very close for propane if not exact. The biggest mistake most "experts" make in opinionating that a propane or natural gas generator will lose power is based solely on these figures and not on any data they personally have. When figuring power output of any fuel, the size of the engine has to be a significant factor of the total equation. For instance, comparing a vehicle with a V8 engine to a generator with an 11hp generator attached can not be calculated the same. The characteristics of the fuels and how they mix with air, how far the piston is in relation the gasoline float bowl effects the power derived from the fuel among many other things. To presume that just because the btu content is less, it is less powerful, is erroneous.
But for those that want even more information we now offer some basic factors, round numbers and some good estimates to see how run time values of propane cylinders can be worked out:
BASIC FACTORS
It requires 2 horsepower to produce 1000 watts of energy per hour under load
Under load, each horsepower consumes 10,000 BTU per hour
Propane contains 92,000 BTU per gallon
Propane weighs 4.2 pounds per gallon
Cylinders are rated by their weight capacity of propane
Bulk tanks are rated by gallon
Cylinder Capacities in Gallons and BTU's
Size Gallon Capacity Total BTU Capacity
20# 4.8 441,600
30# 7.1 653,200
40# 9.5 874,000
60# 14.3 1,315,600
100# 23.8 2,189,600
200# 47.2 4,342,400
420# 99.1 9,117,200
Using these factors we can arrive at run times based on average load for any generator.
For instance:
How long would a 5000 Watt Generator with a 10 HP engine at 50% load run on a 20# propane cylinder?
10hp at 50% load would be using 5 horse power to generate 2500 watts of energy.
5hp x 10,000 btu would consume 50,000 btu per hour.
Using a 20# cylinder that produces 441,600 total btu, the engine consuming 50,000 btu per hour would run for about 8.8 hours.


BTU consumption chart based on generator/engine size and load
Generator Wattage Engine Horsepower Full Load 75% Load 50% Load
1850 3.5 35,000 26,250 17,500
4000 8 80,000 60,000 40,000
5000 10 100,000 75,000 50,000
7500 15.5 155,000 116,250 77,500
8000 16 160,000 120,000 80,000
10,000 20 200,000 150,000 100,000
12,000 24 240,000 180,000 120,000
Many people want to know what size cylinders they need based on their engine size. Here are some real conservative estimates of the vaporization rate of various size cylinders based on the outside temperature.
Vaporization Rates of Cylinders
Output in BTU's per hour - Vertical Cylinder 25% full - Minimum Cylinder Pressure 10 PSI

Cylinder Size
Outside Temperature 20
30
40
100
200
420

+60F 24,000 32,000 40,100 79,700 125,900 185,500
+50F 21,200 28,300 35,500 70,600 111,500 164,300
+40F 18,450 24,700 31,000 61,500 97,200 143,100
+30F 15,700 21,000 26,400 52,400 82,800 122,000
+20F 13,000 17,300 21,800 43,300 68,400 100,700
+10F 10,250 13,700 17,200 34,200 54,000 79,500
0 7,500 10,000 12,600 25,000 39,500 58,300
-10F 4,780 6,400 8,000 16,000 25,300 37,100
-20F 2,050 2,700 3,400 6,800 10,700 15,900
For the physical properties of each cylinder, click on the "Cylinder Size" above.
What does all this mean?

Well, if you went exactly by the chart, you would need a 420# cylinder to run a 14hp engine if it was 25% full and 40 degrees outside and keep a minimum of 10 psi in the cylinder. This is a worse case scenario. For instance, when a 20# cylinder is full it can run a 16hp engine for quite some time in 40 degree weather before there will be any freezing problem. But if you wanted to use up all the gas in a cylinder, it would have to be sized according to the chart.

Here is why. Propane is stored as a liquid under pressure and boils to produce a vapor that is drawn off at the top for the engine to use as the fuel. Because propane boils at -44° (below zero), the gas will freeze if it can not absorb enough ambient heat to compensate for the boiling process. The bigger the cylinder is compared to the amount of load, the warmer it is outside, the warmer the cylinder is kept, all are a determining factor in the likelihood of a cylinder freezing up.
If a sweat or frost line forms around the cylinder at the level of the fuel, this is a telltale sign that the cylinder over worked and is in the process of freeze up. If the gas does freeze, it will stop producing vapor and the pressure inside the cylinder will drop to as low as zero psi which will cause the engine to stop running.

To compensate for an undersize cylinder, two cylinders can be tied together using a tee check and pigtails. Some customers set the cylinder near the exhaust of the engine to help keep the cylinder warm and have no problem using smaller tanks on bigger engines. This practice needs to be carefully monitored so that the cylinder does not overheat and cause the relief valve to check off.



Typical propane fuel consumption for a 2000 watt inverter generator
A liter of propane is 1.1 pounds so propane at $1 per pound = .90c per liter
Propane at .65c per pound typical for 100lbs cylinder =.585 per liter
50% load 800 watts = .42 lbs per hour or .37 liters per hour
75% load 1200 watts = .86 lbs per hour or .73 liters per hour
100% load 1600 watts = 1.25 lbs per hour or 1.125 liters per hour

Willie1959
Member
# Posted: 23 Aug 2017 09:36
Reply 


When you buy an inverter look for one that has generator support . That allow you to use as a smaller generator and the inverter acts as a second generator.

The generator set at max 800 watts so when a 1500 watt load comes on the inverter will add the extra 700 watts from the battery bank until the load shuts off.

creeky
Member
# Posted: 23 Aug 2017 19:27
Reply 


Willie. You're right. The better inverters will load share. For bigger systems a useful feature. Not available with the lower cost inverter/chargers. Never had it myself. Limited utility in small systems really.

Still. Part of what you pay for. Outback. Schneider. Victron. All have this feature.

100ah at 12v = 1.2kw. At 24 = 2.4kw. At 48v = 4.8kw.
Keep an eye on that voltage. And of course, ;) lithium batteries give you more useful power per amp.

Thx for the great info on propane. Learned a lot.

Willie1959
Member
# Posted: 23 Aug 2017 20:07
Reply 


Kind of curious about lithium battery longevity and our cold weather -35 c at my location near Apsley Ontario, Jack lake . current system is 24 volts . I have been using Surrett and Crown batteries first batch lasted 10 years, been off grid since 2000. Was looking at salt water but only good to -4c. I have only ever discharged my batteries to 50%, on an average night the only go down to 90%. I have a fridge and a few yard lights on . I was told size the battery bank to last 5 to 7 days back in 2000. Just replaced all batteries last year and added another 1500 watts of PV, looking to add another 1000 watts. Are the chevy volt batteries Lithium?

Ontario lakeside
Member
# Posted: 24 Aug 2017 22:21
Reply 


HEy Willie

Creeky helped me get set up with one of his systems. I just posted a video walk through that may be of interest.
https://www.youtube.com/watch?v=ZfilBtej3t4&t=4s

Im just north of havelock.

creeky
Member
# Posted: 24 Aug 2017 22:51
Reply 


Definitely look at Ontario's video. His build is really nice.

The Volt battery modules are NMC lithium. They do have to be Plus 5 C to charge. You can go to 0 but 5 to 35 C is best. You can discharge right down to -25.

I don't find the battery heating a problem. They don't off gas so you can put them places you couldn't do lead. And I heated my lead batteries. The derating that occurs as lead gets cold. 10C was the coldest I would let my batteries get.

Couple things. Lithium is at least 20% more efficient than lead charging. More the closer to done you get. So it takes quite a bit of getting used to. There is almost no "absorb" period. Your batteries go on bulk drinking every electron. When they hit absorb, which takes awhile, the amperage drops by 1/2 immediately. In 15 minutes you're at 0 amps.

You've got lead. You know how crazy that is.

As for longevity. As long as you keep your batteries warm when charging. They will last 2-3 times longer than lead.

You realize your experience of 10 years is an anomaly. I was talking to an RV mfct Monday. He was talking about how expensive lithium is supposed to be. And still is some places. I asked him how often he replaced his batteries (commercial coaches and work/research vehicles). 1.5 years was the answer.

Lithium just has too many advantages. Cost per cycle. Lifespan. Charge/discharge efficiency. Etc etc.

I went 5 days multiple times last winter. Didn't use the genny once. I tell ya. Its pretty freaky. You've got 60% of your battery left but the forecast next day is for sun. So you run the dishwasher as you go to bed. Ya don't do that with lead. smile.

Really does change the game.

bronco_ed
Member
# Posted: 25 Aug 2017 00:25 - Edited by: bronco_ed
Reply 


Ontario thanks for sharing nice walk through on the video...

In terms of inverter w/charger @48V, charges at 5amps are these designed more for supplementing panels rather than an actual charge of depleted battery? (20/90)

bronco_ed
Member
# Posted: 25 Aug 2017 00:32 - Edited by: bronco_ed
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Ontario, what is the course of action should a cell begin to display out of your "target" range?

bronco_ed
Member
# Posted: 25 Aug 2017 00:42
Reply 


Quoting: creeky
When they hit absorb, which takes awhile, the amperage drops by 1/2 immediately. In 15 minutes you're at 0 amps.


I flew RC helicopter for a bit(or at least tried)The RC hobby is lithium. When the controller flashed red you best get it down quick or gravity will do it for you ;)

creeky
Member
# Posted: 25 Aug 2017 18:47
Reply 


Ya. Fortunately with SESS you're not in the air ... I've never managed to get below 43.5. And I'm set to 40 before disconnect.

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