Power inverters?

[SOLID D22]

Well thats what im after, you know the 12v convert to 240v product.
Has anyone shopped for one or bought one, if so which brand do you recommend and what wattage is safe to use?
Iv seen heaps on e bay but iv got no clue how good they are compared to what i see in the shops.

Cheers.

 

[Old.Tony]

I've got two, and I'll be hitting Jaycar soon for a third and maybe a fourth - I'll be ditching the one I have installed in the van.

The general idea I have is to supply the inverter with power from the car, use the inverter to drive a decent battery charger, and charge the batteries with that. I have this exact setup in the caravan and will be building it into the tub as well. I also have an inverter inside the cabin under the rear seat, for those occasions when someone needs house power.

My problem though is that when I turn on my ignition, the aux power to the van kicks in and the inverter in the van starts. When I actually crank the engine over, the inverter shuts down for the second or so that it takes for the diesel to come to life and then power is restored.

However, this is enough to cause the stupid inverter to think it's running low on battery, and this inverter - as clever as this bloody thing is - has been set up so that if the battery is running low, it will squeal its stupid head off until you come along and reset it. If it's squealing, it's not supplying 240V - so the charging system in my van has a flaw.

That inverter is going, and I'm replacing it with something in the region of 300W continuous that doesn't do stupid stuff. I only need 105W (the Multi XS7000 C-Tek charger supplies a max of 7A @ 15V) plus the power required to run the CTek, assuming about 50W and then doubling the figure so there's "spare capacity".

That's the measure you could use. Look at what you need to supply (including, for battery chargers, some extra power for the "smarts" inside them) and then double it. Put together like that, you'd hardly ever stress it out and it should last a long time.

 

[SOLID D22]

Cheers tony, for now i will be charging my secondary batteries just through the alternator, i know its not going to be 100% but it is just till i get an inverter. I also want it for just in case power when im out in the bush, plus i just found this air mattress at the bottom of my cupboard, i totally forgot i had, its got its own air pump which works by mains power, its a bit bigger than a double bed when pumped up full and folds away nice and small, plus its really comfy, hence why i want the inverter now.

What prices should i be expecting?

 

[Old.Tony]

I'm looking at this 300W inverter from Jaycar which sells for $84.95.

You can probably get cheaper, but I'm not buying this one until I've bolted the thing onto 12V and emulated a start sequence with a quick-disconnect to see if the inverter barfs on me or just picks up where it left off.

 

[Jason]

I have a 300W inverter, it's great for most gear.

Don't bother with pure sine wave, it's not necessary for 95% of stuff.

Edit: The inverter that Tony linked to is the one I have.

 

[Leprechaun]

I've got two, and I'll be hitting Jaycar soon for a third and maybe a fourth - I'll be ditching the one I have installed in the van.

The general idea I have is to supply the inverter with power from the car, use the inverter to drive a decent battery charger, and charge the batteries with that. I have this exact setup in the caravan and will be building it into the tub as well. I also have an inverter inside the cabin under the rear seat, for those occasions when someone needs house power.

My problem though is that when I turn on my ignition, the aux power to the van kicks in and the inverter in the van starts. When I actually crank the engine over, the inverter shuts down for the second or so that it takes for the diesel to come to life and then power is restored.

However, this is enough to cause the stupid inverter to think it's running low on battery, and this inverter - as clever as this bloody thing is - has been set up so that if the battery is running low, it will squeal its stupid head off until you come along and reset it. If it's squealing, it's not supplying 240V - so the charging system in my van has a flaw.

That inverter is going, and I'm replacing it with something in the region of 300W continuous that doesn't do stupid stuff. I only need 105W (the Multi XS7000 C-Tek charger supplies a max of 7A @ 15V) plus the power required to run the CTek, assuming about 50W and then doubling the figure so there's "spare capacity".

That's the measure you could use. Look at what you need to supply (including, for battery chargers, some extra power for the "smarts" inside them) and then double it. Put together like that, you'd hardly ever stress it out and it should last a long time.

Hey Tony that doesn't seem to me not a very efficient way to charge your battery, why run the car to power an inverter to create 240V AC connected to an 8 amp 12 DC charger, when you have an alternator already producing 12V+ DC capable of 100+ amps?.

Back on the topic I've had a cheap Chinese 120W inverter thats about 15 years old, still works fine, so I don't think you need to get the most expensive for reliability.

 

[SOLID D22]

Cheers guys.

 

[Krankin]

You need to match the watts by what your demand is, plus at laest 25% on top.

Keep in mind the bigger output you use the greater the power consumption used from the supply batt, and these things are heavy on the juice the bigger they are.
you can get devices also, that will not let the supply source fall below a predetermined voltage so you dont harm the supply unit and, the good inverters wont operate below a certain supply voltage.

If u want to maintain your batts while camping etc, better get solar panels.

 

[Aido]

I use a 150w in the work van for charging cordless batteries so that they are ready to go when I get to a job (if you have ever used dewalt batteries you'll understand ). Works as it should and cost about $80 2 years ago from Autobarns.
Cheaper than buying a car charger from De-walt* and Makita and it can be used for charging phone and cameras as well.

You need to match the watts by what your demand is, plus at laest 25% on top.
What he said but also remember as a general rule of thumb that anything with a motor will spike and double its current draw on starting.

 

[SOLID D22]

For arguments sake lets say i need 300w to do what i need it to do comfortably, what if i get a 1000w inverter but never use more than the 300w for what i first intended, would the bigger inverter use more power even though im not using more watts?

 

[Krankin]

For arguments sake lets say i need 300w to do what i need it to do comfortably, what if i get a 1000w inverter but never use more than the 300w for what i first intended, would the bigger inverter use more power even though im not using more watts?

It should only use power enough to supply the output.
cant tell you what that will be as I've never bothered to check my own
, you'll have to put ammeter on to check,
and you wont be able to plug a 1000w unit into your cig socket but will need roughly batt size cable to cater for that size unit.

ie: my 500w unit has a max input draw of 70amps @ 12vdc, thus they are not very efficient but handy nonetheless.

Though IMO i would get one 50% larger than you need at the time of purchase.

Oh, and also they dont have RCD's on the output side so be very carefull or get an RCD outlet box.

 

[SOLID D22]

Rcd box it is. I was never going to have it plugged into my cig lighter socket anyway, i always intended having it hard wired with a fuse to the secondary batteries. I found some good priced solar panels at the battery shop, so im keeping them in mind for future purchases.

 

[KraftyPg]

Rcd box it is. I was never going to have it plugged into my cig lighter socket anyway, i always intended having it hard wired with a fuse to the secondary batteries. I found some good priced solar panels at the battery shop, so im keeping them in mind for future purchases.

Slightly off the original topic but be careful with solar panels I was reading a report the other day that of all the externally fitted accessories to vehicles these days solar panels are the most stolen item. It also stated that the majority of cases weren't just snatch and grab or opportunity grabs because thieves were targeting vehicles with the expensive panels that work better over the cheaper ones.

 

[SOLID D22]

Thanks for the heads up krafty, the panels i was looking at are the better grade panels too, their discounted but there still not cheap. As for items being pinched i have thought of that when i bought my engel, i have some chain and also sailor wire similar stuff that you would lock a bike with, and attach them to the car, first you make sure what its attached to cant be unbolted. As for the solar panel i dont know how that can be secured unless it has a hole for a padlock or something to attach itself onto, but either way its out during the day while im out with it and at night it can go in the car locked.

 

[Krankin]

Dont forget to get a Voltage Regulator for the solar panels,

unless the ones your looking at have one already.

 

[Old.Tony]

Hey Tony that doesn't seem to me not a very efficient way to charge your battery, why run the car to power an inverter to create 240V AC connected to an 8 amp 12 DC charger, when you have an alternator already producing 12V+ DC capable of 100+ amps?.

Basically it's because a car battery, in order to be charged to 100%, needs around 15V or so, and your alternator is regulated down to 14.4V (give or take a little). Your car battery will, because of this, only ever be charged to 70-75% of its actual capacity.

The reason for doing this is that once the battery passes about 3/4 charge and is being fed by about 15V (which won't happen with your car regulator), the battery fluid starts to gas - hydrogen and oxygen are released and the electrolyte in the battery diminishes. To avoid having to maintain the battery every week, don't charge it up as much so that it doesn't fizz/gas - and that's why your alternator/regulator does it like this.

Can't save the full answer, continuing in another post

 

[Old.Tony]

... continued ...

The problem when you're away from power is as I've described elsewhere. A 100Ah battery with 70% charge gives you 20Ah before you should stop drawing power from it - because you shouldn't let the battery fall below 50% charge.

By using an inverter, and a C-Tek charger (which is truly intelligent, it's not a cheapy that claims to be smart), I'm getting 100% charge at the cost of higher maintenance, but I'm also getting 50Ah of usable capacity.

I also have a solar panel on the van, which is great for dribbling in 4Ah in full sun, but we usually average about 2Ah off it, thanks to clouds, trees and the like. It's not enough, with a fridge that draws (average continuous consumption) 2.5Ah all day (5A, on a 50% duty cycle).

 

[dwayne]

hey old tony, what size fridge are your power figures refering to? just curious as i have a 57l combi engel and am just having a 105ah battery installed as we speak and i was trying to figure out how many hours use i would get before needing to fire up the car? bit worried i have gone too small on my aux battery. bloke at battery world also told me the d40's have a voltage reduction system of some sort built in that stops the alternator pumping out a good voltage to recharge batteries until you are up too a considerable speed eg.60kms an hour or so? is any of this true??? sorry its off topic

 

[Old.Tony]

The fridge in our van is a Waeco CR140, 12V/240V only 140 litre. It will draw up to 7A if it needs to, but generally draws 5 to 5.5A. It depends on the ambient temperature as to whether or not it has to cycle more often.

Your Engel would be similar to the MT60 Engel I have in the back of my Navara. It's rated at 4A draw, but I've put a datalogging multimeter on it and only seen it draw 1.5-2A during cycle. They're bloody amazing. Assuming 2A on, and 50% duty cycle, that averages to just 1A per hour, and with a fully charged car battery -> inverter -> charger -> 105Ah battery) you'll have 52A of capacity = 52 hours.

If you charge the 105Ah battery directly from your car (no inverter + charger) you should expect 70% capacity, so 20% usable capacity = 21Ah or 21 hours of running time.

I suppose it says something for using an inverter + charger!

I'm not sure if the D40s use a voltage reduction until a certain speed is reached. Can't see the point of it, if engine RPMs are high enough to crank over the alternator just let it go - and the engine isn't going to blink at spinning an alternator over. Mine doesn't even blink at the air conditioning compressor.

You might be well served to check your voltage at idle. If you're only putting out 13V or so at idle, you aren't going to charge the aux battery very far at all. However, you could feed power to an inverter etc and charge the battery that way - even at idle.

This is one of those occasions where throwing money at the problem DOES fix it. Throw it the right way though: get yourself a C-Tek charger. I haven't seen a better one on the market, anywhere. Even the top-of-the-range one I bought from Jaycar pales next to my C-Tek 7A charger.

Just a small note about our solar panels - I bought another one, 80W monocrystalline, mounted it in parallel to the 64W that was up there. Improved things immediately. Waiting for summer to see how it performs when we've got decent sunshine - we're expecting about 5A off the 80W panel in addition to the 4A we got from the 64W panel.

If you do the math, you'll wonder where the error is - it's because solar panels are measured at their open-circuit voltage (about 17V) for their "rating". They're regulated down to a manageable voltage (mine sit at about 16V) so 80/16 = 5A and 64/16=4A. A regulator circuit reduces the voltage further to properly charge the battery but the amps don't get boosted back up. My amp readings come from my internal battery monitor, which monitors current power draw, accumulated power used and current voltage. Handy tool.

 

[Leprechaun]

I know the alternator output in our Jeep is controlled by the ECU. it has a AGM battery, and takes approx 5 minutes before putting out the 14V+. My D40 cranks out 14.7V right away and at idle.