Inverter/charger question...

[ilyafish]

...now from what i have been researching, and correct me if i am wrong, but an inverter/charger charges your battery bank as you draw power from it....correct?


because ultimately, my question being if i want to create a 120 volt system for everything, can i just buy a bank of batteries, and get a pretty hefty inverter/charger and use that as my power source? 

[belfert]

An inverter/charger cannot produce power.  It only converts power to/from 120 volt.

The inverter portion produces 120 volt AC power from 12 or 24 volt DC power, generally a bank of batteries, but it could also be the bus alternator.  The charger portion will recharge the batteries and provide 12 or 24 volt DC when plugged into 120 volt power like from a 120 volt generator or shore power.

[Nick Badame Refrig/ACC]

Hi Peach,

Did your tour turn out ok? Hope so after your couple of break downs...

This is the best way I can explain how inverter/chargers work.

What is an Inverter or Inverter/Charger?
An Inverter or Inverter/Charger is a device that converts direct current (DC) to alternating current (AC) to power a variety of equipment, including power tools, computers, appliances, pumps, audio/video equipment and more. Inverters and Inverter/Chargers utilize a vehicle's or boat's battery or separate user-supplied batteries to supply power to connected equipment. In addition, Inverter/Chargers provide reliable alternate AC power during utility power problems, such as blackouts, brownouts, overvoltages and surges. When utility power is present, Inverter/Chargers automatically pass through power to your equipment while simultaneously recharging your connected batteries. When utility power is absent, such as during a blackout in stationary applications or while driving in mobile applications, Inverter/Chargers automatically switch from utility power to battery backup power.

Important Inverter and Inverter/Charger Features
Conversion from direct current (DC) power to alternating current (AC) power
Mobile AC power source: portable and permanent-mount
Higher wattage models can power multiple pieces of equipment simultaneously
Peak surge wattage output to handle heavy-draw equipment start-up
Rated over 90% efficient to ensure more battery power is used to run connected equipment
Automatic low-battery shutdown feature ensures battery power is always available for vehicle start-up
Stable, micro-processor controlled output to help equipment perform at its peak
Built-in cigarette lighter/accessory plug or direct connection to batteries
Frequency-controlled output on most models accommodates the widest variety of equipment
Up to 200% of continuous output for up to 10 seconds on most models for extra power needed to start heavy-duty tools and equipment
Up to 150% of continuous output for up to 1 hour on most models to reliably support tools and equipment longer
3-stage battery charger on inverter/charger models recharges batteries faster than conventional chargers
Remote control compatibility via module on select models
Types of Inverters and Inverter/Chargers and Their Typical Applications
Inverters and Inverter/Chargers are typically used in mobile applications where utility AC power is not available. To understand their applications, you need to consider the different types of Inverters and Inverter/Chargers.

Compact/Lightweight Inverters
Compact/Lightweight Inverters are smaller with lower continuous wattage output for mobile business, traveling, camping/boating and trucking applications. They're ideal for powering laptop computers, cell phone chargers, game systems, DVD players and other low-wattage devices.

Heavy-Duty Inverters
Heavy-Duty Inverters are designed for industrial, service fleet, jobsite, trucking and camping/boating applications. They deliver peak surge wattage output to handle heavy-draw start-up of drills, saws, pumps, timing motors and other equipment.

Inverter/Chargers
Inverter/Chargers are reliable power sources for uninterruptible emergency backup applications. When utility power is present, Inverter/Chargers automatically pass through power to your equipment while simultaneously recharging your connected batteries. When utility power is absent, such as during a blackout in stationary applications or while driving in mobile applications, Inverter/Chargers automatically switch from utility power to battery backup power. Inverter/Chargers are designed for EMS, RV and other applications where reliable battery backup is necessary while on the road.


Nick-

[Jerry Liebler]

I'll add to Nick's excellent list.
   There are two major types of inverters, 1. True sine wave.   2 Modified sine wave.
The true sine wave types are more expensive, generate less radio and television interference, operate motor and transformer loads with less waste heat in the load (means longer life for the load).
The 'modified sine wave' types, should really be called modified square wave, have an advantage in efficiency for certain loads.  There are at least 2 'technologies' used to make the true sine wave types, 1. high frequency switching (PWM)  & 2. Multiple transformer.  The high frequency designs are lighter and smaller but may be unreliable with certain loads.  The multiple transformer types are very rugged and tolerate all loads well.  Send me an off board email for brands and models of the various types.
Regards
Jerry 4107 1120

[JohnEd]

What Belfert said.  The inverter doesn't "make" power.  It takes dc power from the battery and "inverts(converts) it to 120VAC" for your bus system to use ...or... it takes 120VAC from the pole and "passes" it thru to your 120 Volt system in the bus  for the bus system to use and at the same time it will divert some of the pole power to a built in DC charger for the batteries. 

A inverter feature you want to look for is the one called "power share".  That will provide a pass thru for the AC but will monitor the charge needed to recharge the battery and allocate the "most" power it can to the recharge without tripping the breaker on the pole.  Many inverters will try to pass thru all the power the bus ac system needs and at the same time go all out to recharge the batteries.  If the bats are low the result will be a current draw of more than the 30 amp max and you pop the pole breaker.  The inverter also has a max pass thru of 30 amps so if the pole doesn't pop the inverter will trip off the line.

If I am talking down to you I apologize...trying to help.  Anybody want to correct me feel free.

John

[ilyafish]

yea i currently have an inverter, and i THOUGHT that an inverter/charger is what you guys are saying, but when i took a trip up to walker coach to pick up a hitch, one of the guys said 'get an inverter charger so that it charges the batteries back up as you use power' and i thought it was interesting cause like i said, when i originally researched them, i thought that how they worked was exactly how you guys said they do, and i was just making sure i didnt miss something.  ah, that would just be too perfect wouldnt it?  haha


now with that being settled, comes 2 questions.  ultimately, i want to have a house battery bank.

the inverter i have now is a 3500 watt modified sine.

question 1:

is it feasibly possible/a good idea to have the 120 volts created by my current inverter (hooked up to the start batteries) used to strictly run to the inverter/charger (hooked up to the house batteries) as i drive therefore giving it the ac voltage it needs to charge the batteries back up.

question 2:

what should i be looking at for a house battery bank?  aka....how many volts per battery....i know alot of people use 6v....is there an advantage of getting a bank of 6v than 12v for example?  and is there a rule of thumb like....for every kilowatt of continuous draw per hour....how 'much' battery(s) do i need?


i just basically dont want to park for 8 hours and then after sitting there for 3 have my house battery bank dead.

[John316]

We have a bank of 4 Trojan deep cycle batteries (make sure the batteries are deep cycle because starting batteries are designed for a quick draw, not for continuous use). We use 2 four thousand watt trace inverters to charge the batteries and to invert to 120, which we use in the bus. A 20 kw EPS generator is our power to charge the batteries when we don't have shore power. The trace inverters have the capability to sync up with shore power (to get the wavelengths synced) and then to limit how many amps the inverters pull. John Ed was right on when he said that the inverter will use as much as it can to charge the batteries, while powering your "house" at the same time. In addition if you are using more power than is available from shore power, the inverter will pull the extra from the batteries to make up the difference. For example, if you are plugged into a regular outlet and are pulling 15 amps and you are using a total of 25 amps inside your bus, then the batteries will supply the extra that is needed.
 

HTH Just my .00000002

God bless,

John

P.S. I just read your last post, we were typing at the same time. Our Trojans are 8D wired to make 24 volt. We can last on that setup for maybe two days if we have light loads. I would also keep your starting batteries and your house batteries completely separate, other than maybe a cut over switch to jump your starting batteries (provided they are the same voltage) if your coach doesn't start. I know Sean, with his Neoplan, had a way rigged so he could charge off of his alternator (we aren't that sophisticated yet  ).

[Jerry Liebler]

Be very careful if you want the feature John316 described.
"In addition if you are using more power than is available from shore power, the inverter will pull the extra from the batteries to make up the difference. For example, if you are plugged into a regular outlet and are pulling 15 amps and you are using a total of 25 amps inside your bus, then the batteries will supply the extra that is needed."
Limits your choice to a very few model of Trace inverters, for example SW 4024 and SW 2512, that use the multiple transformer technique to provide true sine power.
Regards
Jerry 4107 1120

[JohnEd]

What Jerry said.  The feature where the inverter supplements the shore power with phase matched power from the inverter is a really sophisticated and expensive(to me) feature.  There are two features that sound the same:  In modified sine inverters the power share feature limits the power consumed to charge the bats so the load on the 120 AC circuit doesn't  push the total amp draw over 30 amps and trip the breaker on the pole.  Nice feature!  Only in the True Sine inverter can you get the AC from the pole supplemented by AC generated from the inverter while you are connected to the pole.  As Jerry said "only a Trace of certain model can do that".  Magnum is coming out with a True Sine inverter that will have that feature and probably be cheaper than the Trace but it still isn't in manufacture and available.

im,

To me your Question # 1 didn't make sense.  I can only guess at what you really intended. My first thought was "you need to draw me a schematic of what you mean" and I am not being hard nosed with that.  I just need more and more clear info.

I think the bats you want are 6 volt "Golf Cart" bats hooked up for 12 or 24 volts.  The advantage is that if you loose a cell you are throwing away half as much bat as you would if you had 12 volt bats.  With a good inverter's multi level charger hooked up to your bats and a trickle maint charge always applied and your bats equalized on a regular sched those bats should last 6 or 7 years.  Let them sit dead only one time and they are trash no matter what type you purchase.  4 ea 8D bats seems to be the "normal" complement.  That would be roughly 8 each  6 volt golf cart bats.  That is a gross simplification as you need loads identified and amp hours of each bat and an understanding that you will never discharge the bat to more than 50% so you have to double the bat amp hours as listed and it gets thick here....8 6's and your inverter will tell you when you have depleted your bats and you have to start the genny and replenish.  To properly monitor your bats and their performance you NEED the Link 2,000.  And that takes care of another pesky $500.

HTH,

John

[pvcces]

iminaccess, three of the possible Trojan batteries that could be used are liquid lead acid golf cart, L16 and 8D. The golf cart is rated to store about 1 1/3 KWH, the L16 is rated to store about 2 1/3 KWH and the 8D is rated to store about 2 2/3 KWH. For figuring capacity, just add up all that you have to get a total.

The less expensive batteries probably should not be discharged more than 50% of their ratings before recharging. Some of the more expensive deep cycle batteries are rated for the number cycles of discharge at 90% discharge.

In using an inverter, you should allow at least 10% of your battery power as loss in the inverter, so just deduct that number from your battery capacity for 120 operation. In order to figure out how long the batteries will last, you need to tally up your uses of power using the rating on the appliances. If the ratings don't give watts, multiply the amps by the volts to get an approximate value.

You will find that heating and cooling are very demanding loads and should be avoided on a battery bank, if you're interested in making them last.

Your coach charging system should be able to recharge all of your batteries when under way. Most coach generators put out plenty of power for this work. Our 12 volt one is 3 KW and the 24 volt ones go something like 5 KW.

Everything depends on what you want to do with your coach; this post was just to fill you in on some of the numbers and uses.

For what it's worth.

Tom Caffrey