Inverter Warning

[DVR]

Hi DVR, I'd use the term "no brainer" to refer to the morons that run their 3 way on gas as they travel and fuel up, due to the fact their fridge has been poorly installed and wired this is the path they use.

You'd have more chances being trapped in a burning car with a fire started by 12 volt than electrocuted by a 600watt invertor in the tub. The 3 way is on the way out now, due to the reduction in price of solar and soon Lithium compressor is the way to go.

No more sordid milk or hot beer to worry about too. Have you a link to these electrocution claims?, I've never heard of it.

Cheers

Hi John, Just google "3 way fridge on inverter" this and others will come up
http://www.exploroz.com/Forum/Topic/96669/Running_3-way_fridge_in_220v_mode_off_inverter_while_driving.aspx

This is just one of the pages I found. The dangers are discussed through out the replies (as well as good 12V solutions) but the final reply sums it all up the best.

And your right, not running on gas while traveling is a no brainer.
Also.

 

[Old.Tony]

Part of what he talks about is concrete but there's also reliance on what-ifs.

His spec for cabling is also grossly inadequate. "6mm solar" ? No chance. Not over the distances we're talking. I use 21mm2 cable. It's fused. It's active when the ignition is on ONLY. It's connected by screw-in connectors (not ciggy lighter, he's dead right about their reliability). The only thing connected is the fridge and my inverter sits immediately beneath my fridge, no extension cable required.

I take the issue about an accident seriously though. I can't predict when that sort of thing will happen, so my little relay circuit is going to be upgraded - I'm going to build a circuit that will stop working when the vehicle goes off more than a certain amount from level (indicating a roll-over) or when a certain amount of impact is detected. Sound safe enough?

Note that the biggest difference between 12V and 240V operation is the bypassing of the thermostat under 12V. Even if they claim the heating elements draw the same amount of watts (see below), over an extended period this is not the case: without a thermostat, the 12V operation continues mercilessly, whereas once the thermostat determines that the fridge has cooled sufficiently, the 240V operation - and thus the draw from the car - ceases.

Given the efficiency of the insulation in the fridge (and I know this for a fact, because I have an ammeter sitting on top of my brake controller in the cabin that monitors the power going to my fridge) the inverter actually draws power for a very small amount of time while driving.

12V heating elements: in a word, they're rubbish. A 150W element might draw 150W (about 12A) but it seems to produce vastly less heat than a similar 150W element under a higher voltage. They can't be the same element, either. The heat produced by a heating element using DC power can be calculated by the formula V2/R = watts. This means that under 12V, you need a fairly low resistance element to produce similar heat to that used by 240V. In numbers, for a heater producing 150W: 12V requires 12 * 12 / R = 150 or 144/150 = R = 0.96Ohms.

Fundamentally, it works the same for AC current although the values are averages based on the RMS values of the power. 240V requires 240*240/R = 150 or 57600/150 = R = 384Ohms.

I still prefer the 240V method, but I am switching over to 12V operation for the time being. Because my fridge isn't an AES model there's little point in having the circuit disable the 240V side and enable the 12V side, but I'll build that in anyway. My next fridge though will be a compressor fridge so it doesn't really matter, and the inverter will be tossed.

 

[happy john]

The 3 way seems to present a problem to qualified Auto Electricians, sadly most are unable to wire a fridge in a van properly. I followed a elderly gent into a servo and told him he had no lights on the van.

On inspection the trailer plug was a molten mess, the sparky used 5mm wire through the aux of the plug to a fridge that consumed 22 amps. The poor bloke had to have the tug and van towed back home on their first trip in a 60k van.

Tony, I have seen folk use the extra protection you spoke about in the event of an accident via one of these.http://www.rvpartsexpress.com.au/rv-electronics-fridge-switch.html
You just need to modify the time delay circuit by ajusting a trimpot, and have it inline from your power supply to the inverter.

Cheers

 

[happy john]

Tony, What failed in your Aldi Inverter?, I am using up to 600 watts without a problem and about to hard wire it behind the seat. For the price should I replace it?.

 

[Old.Tony]

The Aldi inverter is a cheat, it's not 600W in a single outlet - it's really a pair of 300W inverters all the way from the 12V input on the circuit board to the outlets on the other end. With the circuit only capable of handling 300W (rather than the 600W I was expecting), putting a 380W load on it was asking for trouble and that's what I got.

I've since bought a 600W single outlet Powertech unit which means it ought to handle 600W without trouble. I'm having an issue with it as well, though - and I'm not sure why. The first unit cooked internally - I was lucky it didn't catch on fire.

I'm building a circuit with a voltage/current monitor in it where the connector goes to the fridge inside the van, so that I can see what it's actually getting/using right at the fridge, whether the fridge is on 12V directly, or 240V via inverter.

 

[happy john]

Cheers Tony, I think for the price I'll look at the Projecta 600 watt. I'm getting a Lithium powered chainsaw for the scrub so I make no noise and have no stink of fuel. I'm sure it won't go near 300watts to charge one, alas the specs have no charging power usage to go by.

 

[Boogieboots]

HJ, I bought a Makita chainsaw, only because that is what all my other cordless gear is( drill, angle grinder, blower, fan, lantern/torch, vacuum). It is 36 v, taking 2 18 v batteries and I can't recommend enough. Same charger and batteries for the rest of my gear and as you say, so quiet and no need for an extra can of stinky fuel. I have a 300 W pure Sin inverter from ebay (Giandel I think) and that charges my batts easy. I will post my photos shortly, they are on my phone.

 

[Boogieboots]

This was the firewood I cut with half the charge of my chainsaw. The batts are 4AH. This is WA Goldfields timber out near Noresman so we are not talking soft pine.

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[Boogieboots]

Will post these on the other thread you posted on too for others that are interested

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[MANNING]

I bought a Makita chainsaw

That's the goods Bb. How much did that one set your back?

 

[Boogieboots]

About $370 ish if I recall. I already had the batteries and charger. Of all the cordless tools the one advantage of the Makita gear is the ability to use 2 18v batts so you don't need to invest in a new charger and batteries. Other brands may follow this lead. They now make a 350mm brushless saw that also uses 2 18v batts that looks like an absolute cracker

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[happy john]

Very helpful info gents, if Tony had not looked into the inverter more we'd be none the wiser to it's false claims. Mine is fine but I use it for short bursts, I think running a heating element in a 3 way for hours may be a load most cheap inverters cannot maintain. I'll look at this Projecta and give it a go, for $139 I'd rather start with a new one and they seem to get a good review.
Cheers

 

[Old.Tony]

I've considered buying one of these - I already have the lawn mower, hedger and whipper snipper, so the battery and charger are already here. Lawn mower is the older brushed-motor type but when the ground is soft and my Honda HRX217 wants to play submarine, the Ryobi just goes to work. Generally get to do my whole front yard (22m x 13m minus a concrete path and a driveway) on a single charge.

As for the Ryobi chainsaw, they've now added a chain brake (didn't have one originally) and the brushless motor is a big step up. You'll notice that the One+ 18V chainsaw does NOT have a chain brake so it's something I'd steer clear of. The chain in the 18V version is also less capable, with only half the cutting teeth of the 36V version and a shorter (250mm - 10in) bar compared to the 36V (350mm - 14in).

An inverter would easily provide power for the chargers. Even if they had a 1 hour charger, the 36V 5Ah battery is just 180W, allow 50% for overheads = 270W and still not much to worry about.

Where you'd get into trouble with an inverter in a portable solution is trying to power one of these. Yes it's got a 400mm bar and it's technically around 3hp, but providing 2300W of 240V AC via an inverter has other issues - like current draw from the battery being up near 200A - you could start a 4cyl car with that power draw, don't use a deep cycle for it! Even your common generators (Honda Eu20) can't supply the power needed.

So for small operations (recovery, opportunistic grabs at firewood etc) a cordless job is ideal. 18V probably not, despite its cheaper price (and the fact that I have half a dozen 18V batteries and 3 chargers) because you'd want to cut wood, not rub it to death. Stihl make a good unit but its power isn't far in excess of the Ryobi 36V brushless unit so if you already had some Ryobi gear, going Stihl wouldn't make sense, but if you were just starting out - Stihl make a good range of cordless gear.

You can't really charge the thing via an inverter in the cabin. It's not that the batteries give off gas, but your cig lighter is rated to 10A, and 270W (the guesstimate from above) is about 22.5A so you'd do a fuse in rather quickly. The highest charge rate (allowing an amp for losses) is about 80W in the cabin. If your charger does that, then you should be fine, otherwise it's in the tub with some heavy cabling!

 

[bobys]

My fridge draws about 380W under 240V. Aldi sell a 600W inverter for just $59 and I thought superb, let's do it - so I did. It worked fine.
Cheaper isn't always the best.

Brilliant insight OldTony. Something that not many people would have thought to check on.
Well done mate and thanks for sharing
Cheers Steve

 

[Czechmate]

On the 12 volt vs 240 volt heating elements thing:

With a simple resistive load only heat and light are produced.

so if a 12v 150w element is actually using the rated 150w of energy, the only way for it to not heat as efficiently as a 240v element is if the element is producing significant light also

The difference you notice oldtony, is more than likely due to a lot of 12v stuff being nowhere near the rated wattage

Im a sparky so im lucky enough to have a kyoritsu DC clamp current meter so i can quickly and easily test everything for their current draw, fridges, solar panels, inverter etc

Unfortunately they're about $500 or id recommend everyone on here get one for testing their 12v setups

 

[Czechmate]

http://www.kew-ltd.co.jp/en/products/detail/00035/

 

[Czechmate]

If anyones going to buy one of these online be very careful, there are a lot of fake chinese made Kyoritsu meters for sale online

If you're not experienced it can be hard to tell until you take it to a meter calibrator

 

[GunMentalGrey]

As for the Ryobi chainsaw, they've now added a chain brake (didn't have one originally) and the brushless motor is a big step up. You'll notice that the One+ 18V chainsaw does NOT have a chain brake so it's something I'd steer clear of. The chain in the 18V version is also less capable, with only half the cutting teeth of the 36V version and a shorter (250mm - 10in) bar compared to the 36V (350mm - 14in).

I have the older (blue) 18v one+ chainsaw. I didn't buy it, but found in council clean up and was surprised when I popped in a battery and it worked. It doesn't need a chain brake as the chain runs really slowly and pretty much stops immediately the trigger is released anyway. Not sure if the newer versions run the same speed though.

I wouldn't recommend one to buy, but it's been handy cutting smaller bits for firewood and pruning duties at home.

One that has anyone powered a standard Ryobi 18v charger off an inverter successfully? As I've now got a range of one+ stuff it would be handy to take a charger along in the cravan to charge batteries for lights, fan, chainsaw or whatever else seems like a good idea.

 

[bods]

I have the older (blue) 18v one+ chainsaw. I didn't buy it, but found in council clean up and was surprised when I popped in a battery and it worked. It doesn't need a chain brake as the chain runs really slowly and pretty much stops immediately the trigger is released anyway. Not sure if the newer versions run the same speed though.

I wouldn't recommend one to buy, but it's been handy cutting smaller bits for firewood and pruning duties at home.

One that has anyone powered a standard Ryobi 18v charger off an inverter successfully? As I've now got a range of one+ stuff it would be handy to take a charger along in the cravan to charge batteries for lights, fan, chainsaw or whatever else seems like a good idea.

You would be ok running a charger off an inverter. Just have a look at the bottom of the charger and see if it has either an amp or watt draw and make sure your inverter is appropriately sized. Alternatively, ryobi do a 12v car charger, whether they are any good or not I couldn't say.

On the chainsaw topic, they now do a standard one or a brushless one in the 18v one+ range. The standard one apparently has a push button chain oiling setup, whereas the brushless one is automatic. They aren't cheap though, even for the "skin only" without batteries...

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[Old.Tony]

+1 for Bods' advice. I've used my One+ 18V charger in the car before, had no drama at all. It's not actually high wattage - one of my chargers (I have 3, thanks to the number of 18V kits I've bought) states on the bottom that it's a 55W device - you could use a ciggy lighter outlet (10A) and one of those can inverters to provide the juice for it without any worry at all.

I really can't see an 18V - even brushless - chainsaw having a huge amount of power. If you're talking actual power (Czechmate will know this very well) an 18V unit drawing 2 amps is using just 36W of power - that's around 1/20th of a horsepower. My Stihl MS180 (which I checked while I was getting firewood ready for winter, has an 050 chain now instead of the 043) is rated at 1.5Kw or 2Hp, and even at 36V and 4A we're only talking a quarter of a horse power (36 * 4 = 144Watts) at the most. I think common sense is going to rule and if I do get a cordless saw, it's going to be for emergencies only, the Stihl will stay in the ute.

I have a habit now of sharpening the chain - 3-4 swipes with a hand tool (exactly this one) that does both the tooth and the rake at the same time. I do this after every tank of fuel. Needless to say, you really don't want to put your hands anywhere near my chain even when it's off - it bites hard!