EPDM Coatings
rvupgradestore.com Composet Products Custom Yacht Interiors

Author Topic: Battery size to support 2kw inverter  (Read 17409 times)

Rvliberty

  • ---
  • Posts: 87
Battery size to support 2kw inverter
« on: December 16, 2011, 10:52:35 PM »
It was suggested to me that to put in a 2kw magnum inverter one should have at least 440 amphours of battery capacity. Has anyone done this with 220 ah or less? Any issues?
Alan Howell
2012 Winnebago View 24J
Bellevue, Wa

Just Lou

  • ---
  • Posts: 8125
Re: Battery size to support 2kw inverter
« Reply #1 on: December 16, 2011, 11:06:22 PM »
If you intend to use anywhere near the 2K output of the inverter you will need at least a 400 ah battery bank.  You will also need a good 3-stage charger if you draw down your batteries very often or expect fast recovery when you do.

Decide what you want the inverter to drive, size it accordingly, then figure out the battery capacity required to make it happen.
'97 Bounder 34V (F53 w/tag), '99 Honda Accord EX

SargeW

  • Forum Staff
  • ---
  • *
  • Posts: 6404
  • Life is better on the road!
Re: Battery size to support 2kw inverter
« Reply #2 on: December 16, 2011, 11:49:50 PM »
Lou is right on. Also if you plan to dry camp a lot, you may want to consider 6 volt batteries as opposed to 12 volts. Sixes are better at taking a deep discharge and coming back strong more often than most 12V.

As Lou said, it really comes down to what you plan on powering with your inverter......
Marty--
2017 Tiffin Allegro Bus 40SP
Cummins ISL 450 HP/Powerglide chassis
Visit our new travel blog! http://www.mytripjournal.com/rvnchickTNG
Support your local Police Officer, Fire Fighter and Military!

Rvliberty

  • ---
  • Posts: 87
Re: Battery size to support 2kw inverter
« Reply #3 on: December 16, 2011, 11:54:01 PM »
I am already planning on 6v conversion. I would love to add another set to get 440ah but having a hard time finding room in a winnebago view 24J. Suggestions?
Alan Howell
2012 Winnebago View 24J
Bellevue, Wa

Ernie n Tara

  • ---
  • Posts: 3295
  • Life is Good - Together
Re: Battery size to support 2kw inverter
« Reply #4 on: December 17, 2011, 09:04:12 AM »
I've no idea where you might put the batteries, but to put this in context;

a. Two thousand watts at 12V = 167 amps draw.
b. A 440 AH battery is good for about 50% of that (assuming good golf cart batteries or equal) each charge/discharge cycle or 220 Amps for one hour (0r 110 A for two hours, etc.).
c. This reduces to about 1.4 hours at full drain. Actually, allowing for 90% efficiency in the Inverter, more like 1.25 hours.

The above is why 440 AH is recommended. Obviously, you won't (I hope) try to run at 2,000 W all the time, but if you use any significant part of it, you need the big batteries. Note also that most inverters will be most efficient when producing full power, so it behooves you to properly size the inverter, not oversize it.

Hope this clarifies the problem,

Ernie
Ernie 'n Tara

2011 Winn Journey 34y
2012 Jeep Rubicon - Dozer (orange - kinda)
2006 Jeep Wrangler

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 61051
  • RVer Emeritus
Re: Battery size to support 2kw inverter
« Reply #5 on: December 17, 2011, 12:01:59 PM »
Even 1000 watts is tremendous load on the batteries - about 90 amps continuous.  That's similar to cranking your engine continuously  and you know you couldn't do that for long on just one battery, so two is a bare minimum. But I suspect your typical use will be more like 300-400 watts, e.g. computer, tv, sound system, satellite, etc.  You can probably manage with two batteries and 220 AH if that's your most common loading. But then, you wouldn't need a 2000W inverter either, and a smaller one will be more efficient at lighter loads.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Lou Schneider

  • Forum Staff
  • ---
  • *
  • Posts: 7410
Re: Battery size to support 2kw inverter
« Reply #6 on: December 17, 2011, 12:11:27 PM »
The other problem in trying to draw a lot of current from deep cycle batteries is they aren't made for that kind of use.  Deep cycle batteries have thick plates with limited surface area and are suited for long, slow discharges.  You can't draw out all of their energy over a short period of time.  The plate surface will get depleted and the battery voltage will drop, making the inverter shut down from low voltage long before all of the battery's charge is used up.

Adding more batteries keeps the current drawn from each battery within usable limits.  Most deep cycle batteries deliver their rated capacity over a 20 hour discharge cycle.  Most are also rated for a 4 hour discharge at reduced capacity.  A 2 hour discharge is really pushing them.
« Last Edit: December 17, 2011, 12:13:55 PM by Lou Schneider »

jje1960

  • ---
  • Posts: 1531
  • Jim
Re: Battery size to support 2kw inverter
« Reply #7 on: December 17, 2011, 12:41:55 PM »
Still have not decided how to add/change in the spring with ours.  I know the 6V batteries are great, just not sure if it's cost effective for what we need.  I've got what came with the trailer, single car battery, 12V now.  It's not enough to run the 32" flat screen on the inverter, amp draw exceeding even fully charged.  It's either just add another 12V or switch to 4 6V batt's, again, still looking into what's best.
Jim
2011 Ford F350 DRW 6.7 Diesel
2011 Cougar SRX

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 61051
  • RVer Emeritus
Re: Battery size to support 2kw inverter
« Reply #8 on: December 17, 2011, 12:55:05 PM »
Excellent point, Lou! A 220AH battery bank has nowhere near 220AH if the amp rate is high. For example, a 6v golf cart battery that can deliver 220AH over 20 hours is only rated for 185 AH over 5 hours. This example is from the Trojan battery spec tables.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Rvliberty

  • ---
  • Posts: 87
Re: Battery size to support 2kw inverter
« Reply #9 on: December 17, 2011, 01:13:47 PM »
Thanks to all for your inputs.  This is a big help.  I was told that Magnum Energy recommends 440 ah for a 2kw system but did not know why.  The input about running the inverter at near peak demand to get the best performance may be why I have seen several people talk about using a couple of smaller, task specific inverters.

Most of the time the draw will be in the 300-400 watt area as indicated, but I do want to be able to run the coffee pot and even the microwave for short periods of time (a few minutes at best) without using the generator.

I would love to go to 440 ah if I can find a place on a 2012 View 24J to stuff the dang batteries.  So far my only choice is an exterior storage area but I think it will need to be reinforced, or the dinette bench in the slide out (and I will have to use AGMs).  I am averse to putting that much weight on the slide as well as constantly flexing the wiring.  I have looked under the coach for a place to build and mount a separate battery box, but I have yet to find one.

Again, thanks for the valuable input.  Further suggestions are greatly appreciated.

Alan Howell
2012 Winnebago View 24J
Bellevue, Wa

Molaker

  • ---
  • Posts: 5766
  • We don't camp. We tour.
    • Pumpkin and Us
Re: Battery size to support 2kw inverter
« Reply #10 on: December 17, 2011, 09:34:39 PM »
Using Ernie's posting
Quote
a. Two thousand watts at 12V = 167 amps draw.
keep in mind the amperage required for up to 2 kw and select wire size from the batteries to the inverter appropriately.  The further the distance, the bigger the wire size.
Tom & Joyce and Ditto the "don't tell her she's a dog" Westie
U.S. Navy (Ret)
2014 Winnebago ERA 70X 24' class B Sprinter chassis

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 61051
  • RVer Emeritus
Re: Battery size to support 2kw inverter
« Reply #11 on: December 18, 2011, 08:37:59 AM »
My best advice is to use a 700-1000W inverter with two batteries and use the generator when you need more power.  There are coffeemakers that will run on 1000W (usually the smaller 4 cups models), or get the type with an insulated carafe and just run the generator while it brews and then turn the genny off.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

SCVJeff

  • ---
  • Posts: 1075
Re: Battery size to support 2kw inverter
« Reply #12 on: December 18, 2011, 10:21:12 AM »
The OP did mention Magnum in his post, so he might be looking at a combo (MS or PS series)to save space. At least on those you can specify the size of the stack, as well as back the charger off to almost anyplace you choose.
_______________________________
Jeff - WA6EQU
Santa Clarita, CA.
'06 Itasca Meridian 34H, CAT C7/350

Rvliberty

  • ---
  • Posts: 87
Re: Battery size to support 2kw inverter
« Reply #13 on: December 18, 2011, 12:05:04 PM »
SCFJeff

I am looking at the Magnum MS2012. What are you referring to with the size of the stack?
Alan Howell
2012 Winnebago View 24J
Bellevue, Wa

SCVJeff

  • ---
  • Posts: 1075
Re: Battery size to support 2kw inverter
« Reply #14 on: December 19, 2011, 12:55:44 AM »
Sorry... I should have said battery stack. I'm around giant UPS systems and really big battery banks in news and satellite trucks allot and we slang the terms sometimes. I have an MS2012, and installed another 6 in some new news trucks I just bought it's a great unit. But if you really want to know how your batteries are performing , make sure you get the BMK option with it. You will have a much easier time managing your loads with a smaller battery bank.
_______________________________
Jeff - WA6EQU
Santa Clarita, CA.
'06 Itasca Meridian 34H, CAT C7/350

Rvliberty

  • ---
  • Posts: 87
Re: Battery size to support 2kw inverter
« Reply #15 on: December 19, 2011, 08:39:29 AM »
Thanks Jeff
Alan Howell
2012 Winnebago View 24J
Bellevue, Wa

John From Detroit

  • ---
  • Posts: 19801
  • ^My New Home^
    • Diabetics Forum
Re: Battery size to support 2kw inverter
« Reply #16 on: December 19, 2011, 09:17:03 AM »
Minimum battery bank to support a 2KW inverter is 200 amp hours (At the 20 hour rate)

Recommended minimum is twice that (400 amp hours)

Suggestion is two pair of six volt golf car batteries in series parallel.   Or more
Nothing adds excitement like something that is none of your business
My Home is where I park it.

SCVJeff

  • ---
  • Posts: 1075
Re: Battery size to support 2kw inverter
« Reply #17 on: December 19, 2011, 09:32:55 AM »
That's assuming he can or would run it at full load.
_______________________________
Jeff - WA6EQU
Santa Clarita, CA.
'06 Itasca Meridian 34H, CAT C7/350

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 61051
  • RVer Emeritus
Re: Battery size to support 2kw inverter
« Reply #18 on: December 19, 2011, 10:24:49 AM »
The point is that if it is ever run at anywhere near full load, a two battery bank (180-220 AH) is going to be insufficient. The voltage will fall rapidly and likely will cause the inverter to shut down within a minute or two or three. And doing so will impact the batteries life span as well.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Rvliberty

  • ---
  • Posts: 87
Re: Battery size to support 2kw inverter
« Reply #19 on: December 19, 2011, 11:05:41 AM »
The only time a really high draw would be used is the microwave and that would only be for a few minutes. It is a 1000w microwave. The specs say the peak draw is 1500w input for the 1000 w output. I am not sure how long the 1500w draw would be (constant or just start up).  I need to put a kill-o-watt on it to see. I really want 440 ah but still trying to figure out where to put the dang things.
Alan Howell
2012 Winnebago View 24J
Bellevue, Wa

Lou Schneider

  • Forum Staff
  • ---
  • *
  • Posts: 7410
Re: Battery size to support 2kw inverter
« Reply #20 on: December 19, 2011, 02:05:59 PM »
1500 watts is about right to get 1000 watts out.  There's nothing that will cause a peak load like a motor starting up.

Of course, that 1500 watts is only at a full 120 volts.   Reduce the input voltage because your batteries can't deliver a full 12 volts while loaded to 125-150 amps and the current draw and output power will drop proportionately - the power at the square of the voltage reduction.

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 61051
  • RVer Emeritus
Re: Battery size to support 2kw inverter
« Reply #21 on: December 19, 2011, 04:12:35 PM »
I can tell you from experience that you need about 300+ AH to run a 1500 watt microwave. 220 AH just won't hack it - the voltage drops too quickly. I coupled a 12v, 105AH AGM in an adjacent bay to a pair of 6v golf cart batteries (220 AH) under the step so we could run a big microwave or 1200 watt coffee pot in a previous coach. Yeah, combining different battery types and sizes is generally a no-no, but I felt I had the technical knowledge to evaluate the status and performance and so went ahead. It worked fine. The microwave ran long enough to reheat a dish or a cup of beverage, which is all we wanted from it on inverter. We ran the generator if we had a sustained need for microwave or convection cooking. That's what the genset is there for.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

SCVJeff

  • ---
  • Posts: 1075
Re: Battery size to support 2kw inverter
« Reply #22 on: December 19, 2011, 11:10:15 PM »
The point is that if it is ever run at anywhere near full load, a two battery bank (180-220 AH) is going to be insufficient. The voltage will fall rapidly and likely will cause the inverter to shut down within a minute or two or three. And doing so will impact the batteries life span as well.
Agreed.. But the OP also said he (probably) doesn't have room for additional batteries, and would need to manage his loads. He just can't use it to max load.
_______________________________
Jeff - WA6EQU
Santa Clarita, CA.
'06 Itasca Meridian 34H, CAT C7/350

YaddaYadda

  • ---
  • Posts: 69
Re: Battery size to support 2kw inverter
« Reply #23 on: December 24, 2011, 09:15:59 AM »
We crammed six 6volt batteries and a 2000w Xantrex inverter/charger into our now departed 2004 W/I Sightseer 27C:  Two 6v under the entry stairs and four 6v on a slider tray in an adjacent compartment that was divided into two sections and well ventilated.  Four batteries in one section and the Xantrex in the other.  A Link 1000 display/readout installed inside.  Worked very well for occasional microwave use and our generator re-charged the batteries to 80% in maybe 20 minutes.  I forget specifics.

Wyotraveler

  • ---
  • Posts: 134
  • NW Wyoming
Re: Battery size to support 2kw inverter
« Reply #24 on: December 24, 2011, 04:48:43 PM »
I use a 1500 watt inverter on our ranch. Easier to use than a portable generator, especially in the winter when it seems those generators won't start at 20 below zero. However, I use #2 wire and battery clips and leave my PU running when I am using electric power tools. The 1500 watt inverter runs electric drills, saws etc very well.  Not sure I would want to use one in my TT.
2013 Monaco Monarch
2012 Jeep Wrangler Sport
AC6CV ex-W8RUR since 1954
ARRL 35 WPM certificate 1st Radio tel/telegraph cert.

jje1960

  • ---
  • Posts: 1531
  • Jim
Re: Battery size to support 2kw inverter
« Reply #25 on: July 31, 2017, 05:55:45 PM »
Still have not decided how to add/change in the spring with ours.  I know the 6V batteries are great, just not sure if it's cost effective for what we need.  I've got what came with the trailer, single car battery, 12V now.  It's not enough to run the 32" flat screen on the inverter, amp draw exceeding even fully charged.  It's either just add another 12V or switch to 4 6V batt's, again, still looking into what's best.

Well, been a bunch of years since this thread, fun looking at the original idea and where we ended up though.  Ended up with a 2K inverter, 4 AGM Optima batteries, 220Ah.  Anyone 'thinking' of doing the plunge should do it!  We love it.  Our stops now do not require starting generator, use microwave, TV, Direct TV, coffee maker, charging the Ipad's, phones, Maxxair ceiling fan.  Single battery days over and it's really great.  These are over night stops while traveling, even started playing with running the fridge on the inverter while under way connected to the tow vehicle.  Reasonable investment has really paid off with some added  comfort.  I have forgotten to turn off the converter once or twice.... (Gary said that would happen....) All good, have that routine down now.  Use 100W solar suitcase now as well, definitely using the generator less during the day to keep the batteries charged while not on shore power during the day.  Still 36mos to go to retirement and more dry camping, however definitely have learned a lot and thinking of adding two more batteries for longer stops.  Just our experience, not an off grid full time solution for sure!
Jim
2011 Ford F350 DRW 6.7 Diesel
2011 Cougar SRX

 

Hosted by Over The Network