Inverter capacity Vs Battery capacity

Martin mate battery drain is the single biggest practicality limiting factor for inverters.

consider that whatever you draw from the 240V side in the way of current you are drawing 20 times that pluss losses from the battery on the DC side.

A 1500 watt inverter fully loaded will be drawing more than 130 amps from the battery.......that is about what the starter motor on a 4 cylinder diesel draws in normal starting.

So how long do you expect to crank that motor?

Inverters themselves have got very much cheaper and easier to obtain in the last few years, but the findemental pracitiality issue of......"where is the energy comming from" remains.

Now remember that ALL batteries work less efficiently the heavier the current drain.

You may have a 100AH battery when measured at the 10 hour rate, but when you hit it realy hard its actual capacity may be half that...then remember we don;t need to be deep cycling our batteries if we want them to last.

So that 100 AH battery realy has a practical capacity of may be 25 amp hours at high currents.

So that 1500 watt inverter...you'll get about 10 minutes out of it before you start to damage ya battery.

there are lots of people buying very large inverters for portable use......sorry the practicality is just not there unless you are carrying huge battery banks.

Th real practical case for 240V devices in campng / touring/ caravanning is getting less and less, as so many things run native on 12 volts now.

cheers

It is more about how long you wish to maintain a high draw via the inverter.
Your battery can deliver cranking amps (maybe 600 or 1,000A) for 30 seconds, so it could deliver 2,500W via an inverter easily, but not for 10 minutes.
Lead acid batteries also deliver less total power when it is delivered at higher rates too.

Dig out the specs for the battery involved (they should be available for a good deep cycle battery) and calculate the total power you want to draw over time.

Cheers,
Peter
OKA196 motorhome

Preferably do not use an inverter!
If you have to use one use it only for very short time and on low power items.

As previously mentioned it is better to use gear that runs on 12v instead, especially if you need to use it a lot.

If you have power tools you want to run on an inverter, then do not run it of the battery , run it of the running car engine or run a generator that produces 240V,

and if you want to run an aircon unit , definitely use a large generator over 2.5kW

Data from 1 inverter manufacturer suggests minimum requirements for 12 volt system :-

1500 Watts 200ah, 3000 watts 500ah. The ah ratings are C10, in other words 10 hour ratings. So using usual 20 hour ratings you will need approximately double the capacity.

Cheers

Thanks Bantam and others.

The reason for my query post starts with the "Navigator " requiring her cappuccino immediately upon arising before any thought or action could be contemplated for the day.

So we have a DeLonghi 1250 watt 240v cappuccino machine supplied by a Victron 24v 1200 watt(cont.) Inverter/Battery Charger attached to 2 x 200 amp.hr AGM VRLA batteries in series and 3 x 165 watt 24v Sharp solar panels. Probably 4 cups of coffee are made each day with say 4 x 1.5 minutes each of current draw.

The house batteries, new in Dec 2009, have died over the last couple of weeks - auto elec in Goondiwindi advises they are down to about 35% capacity. I would have expected a much longer battery life given that the batteries are always fully charged via the solar when the motorhome is not in use. I was wondering whether drawing 1,200 to 1,300 watts 4 times per day for 1.5 minutes each was too high a draw for these batteries ( cyclic or deep cycle batteries having fewer and thicker plates than high discharge rate = cranking batteries) and this may have need a contributor to what I consider a too early failure.

Probably drawing about 60 amps (at 24v) from the batteries whilst making coffee so is this likely to cause premature? battery failure ?

Cheers from Martin B.

Firstly you have to remember that batteries do not live for ever...and every high current drain ocurance takes a little off their life.

NOW.....contraversial statemant here......Deep cycle and in particular AGM is being pushed very hard onto travelers.....they may not be the best choice where batteries are hit hard and heavily recharged every day.

That is more a cyclic application like a cranking battery.

Remember a sealed marine cranking battery will cost half what a deep cycle AGM will......if you are hammering a deep cycle It will last no longer than a cranking battery.

Get the numbers off the existing batteries and google up the specifications..and consider their age.

It is documented fact that people are getting far less than the designed life span out of AGM batteries for a number of reasons....or many other batteries for that matter

I was reading a research paper the other day that claimed that long life stationary AGM batteries could have the life reduced from 15 years design to 60 days by excessive heat and as few as 10 deep discharges to 10.5 volts...while otherwise maintaining to spec operation.

I doubt very much that the coffee machine is killing ya batteries all on its own....but 60 amps will be a kick in the balls after supplying the ovenright load.

Have ya thaught about one of those little stove top perculators, and a $2 milk frother from Ikea.
A coffe machine might be comnvienient, but it does not make the smells and sounds that a little perc does...AND ya get a better choice of coffees.

cheers

Like Bill above my wife is also particular about her tea and coffee.

Maybe that cappaccino monster should be replaced with a billy on the fire and a packet of Nescafe Cafe Menu /Cappuccino at 63c a cup. It's not new it's been around for a while.

And ditch that monster or leave it at home. You will very quickly hate it after replacing batteries.

Or camp at a powered site.

Phil

They are probably the most expensive cups of coffee in the world.

I thought the concept of 'getting away from it all' was leaving this sort of stuff behind?

A stovetop coffee maker will probably make a good cup, albiet not a 'cuppacino' for about 50c.

Do you think a reality check may be required?

Sounds a bit like too much pandering going on. What do you get when the day starts?

http://www.fullriver.com/products/dclist.htm
A 120Ah Fullriver DC AGM has a CA rating of 900A for 30 seconds and can deliver 75A for 50 minutes.

90 seconds at 1200W (100A) is 2.5Ah at 12V.
That should not bother any reasonable battery.

Cheers,
Peter
OKA196 Motorhome

My friend has just fitted a 1500w contentious 240v inverter into his ute.

While camping over Easter we decided to give it a try out powering our Baby bottle etc. Sterilizer as we had our baby with us. We would normally use our little Honda genny for the 5 or so minutes it takes to run the Sterilizer but given his new inverter we thought why not give it a shot.

The Sterilizer draw's around 700W at 240V.

This equated to a 70Amp (measured by my Fluke true RMS clamp meter) load from his Inverter while the Sterilizer was running (5-6minutes max) with the car engine running and the alternator supplying the load. Without the engine running id hate to think what the load might have become as voltage drop started to kick in from the batteries.

The inverter didnt break a sweat and the housing remained stone cold.

There is no way i would run the inverter with any sort of load above a camera battery charger or phone charger connected without running the engine.

Travis.