Inverters

KD · Member

Inverters

Jaahn · Guru

Hi KD,

Man that is some big inverter. It will draw 300 amps or more at 12V. Can your batteries sustain this and your cables etc. Do you have a plan or just going bigger is better so you can run anything ??

Jaahn

KD · Member

Running split system aircon 5- 6 amps Plus the normal stuff Got 520 ah batterys @ 12v But thinking of going 24v inverter Generator good for 3300w Try to cut down generator run time if aircon running all night

Aus-Kiwi · Guru

Imo a good built in Onan or similar generator will be better option with good sound proofing ..Possibly lighter unless you go $$$ lith batteries ??

Barboots · Senior Member

A Powerstar W7 type China inverter will handle your "split and other stuff". I run an Aircommand Cormorant off one no worries... it pulls about what you quoted. Mine is a BitDeals 3000/7000. If I was using it full time I'd probably have shelled out for a Victron, but it would have been over four times the price.

Jaahn · Guru

KD wrote:
Running split system aircon 5- 6 amps Plus the normal stuff Got 520 ah batterys @ 12v But thinking of going 24v inverter Generator good for 3300w Try to cut down generator run time if aircon running all night

Hi KD,

Have you done the maths on this ? If you want to run the a/c all night on the inverter at say only 1000W average it will draw, say about 100 amps at 12V. That will give you 2.5 hrs to draw down your batteries to 50%. Or have you got a better way to look at it. confuse

Is the a/c unit an inverter model which will run down to a low cooling rate ?

Changing to 24V does not reduce the power required only the amps flowing at the higher voltage. hmm

Jaahn

KD · Member

Is there any other option to run aircon Apart from generator running 24/7 Is inverter type aircon , not install yet could change to better option.

Peter_n_Margaret · Guru

A VERY large (in RV terms) solar system with proportionally large battery bank plus a fuel cell.

It is still unlikely that you would need a 3.5kW inverter.

Or stay at home if you can not do without your air conditioning.

Cheers,
Peter

-- Edited by Peter_n_Margaret on Tuesday 13th of February 2018 10:27:13 AM

Aus-Kiwi · Guru

Book into caravan park for 240v ? A cold shower and good fan helps .

Jaahn · Guru

Hi KD smile

We are not trying to be negative here, certainly not me, but what you are asking for might need more research and thought.

I suggest you look at the threads on this forum about air conditioning motor homes and caravans. There has been some discussion on the topic including using battery storage. Also look at the input power of the various types of small a/c units, particularly how they turn down to the lowest setting and the power drawn then. Note startup power is important too for normal units.

However remember, to use stored power, first you need to make the power you need. Second you need to store that power to do what you want. Simple really ! hmm People do struggle with the concept though ! That free power from the sun takes a bit of hardware to capture out there.

Jaahn

KD · Member

Thanks Jaahn for positive feedback Solar, larger battery bank , inverter costs compared to keeping it simple with a generator @$25 per day fuel Guess this is the answer now l am looking for My goal is to run the microwave or kettle without turning aircon off , so l am up around the 3000w For the people who drive around Northern Aust without a aircon l salute you But not for me

robol · Veteran Member

Hi KD.
A few sugestions to consider.
Paint the roof with Thermalite which is mixed in a coat of paint and can be painted on with a roller or brush.
Cover the roof with plenty of solar panels, the more the better as they not only collect power but also shade the roof.
Plenty of insulation in the ceiling and walls.
Allow for an awning on both sides of motorhome, keeping in mind maximum width limitations. An alternative to a second awning is to fix a length of sail channel to the drivers side and run a shade sail through it which can be pegged to the ground.
Good curtains.
Cheers Rob.

Jaahn · Guru

Hi KD smile

As far as the inverter size goes you might be better to have one dedicated to the a/c of a closer fit power wise so it is as efficient as possible. Less wasted power. Then have another that runs the other stuff sized appropriately. cry

I do not have an a/c but i have read that there are smaller inverter models that will, after they get the bus down cooler then slow down the compressor/motor to save power and go down to about 30% power. So there is no starting and stopping which takes large lumps of current. And 30% is probably ok after the sun goes down if the place has been cooled before and enough during the night. Research it. None of the caravan a/c units seem to be advanced designs yet. Clunky old fashioned things !!

Of course do those other things suggested also to reduce the heat load.

Jaahn

-- Edited by Jaahn on Wednesday 14th of February 2018 02:18:59 PM

KD · Member

The 2 inverters are a good idea Will look into going that direction Also gives me a back up if one fails The split system idling should draw around 700w insulation a must as well

T1 Terry · Guru

KD wrote:
The 2 inverters are a good idea Will look into going that direction Also gives me a back up if one fails The split system idling should draw around 700w insulation a must as well

Ummm...... Inverter air conditioning will use roughly the same peak power as a non inverter unit, maybe even more, while pulling the temp down, then it reduces the amount it draws on a percentage of load. This second phase is the one that uses less power because the unit does not run the compressor at full load and then off, then start up at full load again, they start up soft, ramp up to full load until the temp comes down and then reduce the load while still running.

A lot of people get caught with that one when sizing their inverter, the over all average is less and the start up requirement is only full load power and no added start up current, but you still need to allow for the full load power.

A Projecta IP2000 will run a roof top rattler, a microwave, a 2.5kW split system air con under full load, an air fryer, all but the biggest power user kettles or toasters, coffee machine, milk frother ........ but really only one at a time, the W7 will run the air con plus any of the other high power units at the same time, but you might be asking a bit much to run too many of them at the same time though wink

As far as batteries to power the air con from an inverter all night, this was the very thing that got me into lithium battery research in the beginning. As long as you don't expect to run a 2.5kW unit on full noise and dial in 16*C while it's 40*C plus outside, lithium batteries can do the job and quite a few people we have installed systems for actually do run their air con on economy mode all night set at around 23*C.

You do need a method of replacing the energy used from the battery and that requires either a serious solar installation or a combination of solar and either alternator charging or generator charging. The advantage in using quality lithium cells in a properly set up installation is you can belt the charge in as fast as you can produce it, percentages of capacity aren't really an issue when it comes to RV charging capacity, 50 amps per 100Ah of capacity is considered standard charge rate by the manufacturers. Not many RV owners could reach 200 amps of charging current to recharge their 400Ah battery, but if they could it would be recharged in 2 hrs and that is what you need if you want to recharge via a generator and solar combined, a battery pack that can be fast charged until full.

T1 Terry

-- Edited by T1 Terry on Thursday 15th of February 2018 07:48:45 PM

KD · Member

Thanks Terry I need to look into lithium batterys and charging Good to know what l am trying to do is achievable Is there a lithium battery you would recommend

T1 Terry · Guru

KD wrote:
Thanks Terry I need to look into lithium batterys and charging Good to know what l am trying to do is achievable Is there a lithium battery you would recommend

Lead me not into temptation :lol:

After my wife got the golden handshake from her IT job she bought me a workshop and established a business in Mannum SA because she was sick of me filling the house yard with my experimenting and spending her hard earned money without a return. Her business is called T1 Lithium, being an IT person the web site is next to none existent, a bit like the mechanics car and builders house thing. But there is a phone and email address I believe, so that is one option, we aren't the only people who build custom systems but probably the one with the most field tested systems and systems that have been in constant 24/7 use for over 7 yrs now and still going strong.

I'll put in a warning here about drop in 12v lithium batteries connected in parallel, lead acid batteries have problems using this method but lithium batteries will not share the load and charging between the individual 12v batteries resulting in a less than ideal set up that will die an early death.

Also, there is no such thing as a lithium battery compatible charging system unless it incorporates a link to the batteries BMS or cell monitoring/voltage control functions and as yet there is no universal language used for communication between the battery BMS and charger, each is proprietary based so all the same brand and series model equipment must be used.

I know I'll get into trouble for this post but you did ask biggrin

T1 Terry

KD · Member

Thanks Terry I need to look into lithium batterys and charging Good to know what l am trying to do is achievable Is there a lithium battery you would recommend