First Tests With My New Inverter.

[Rohorn]

Hi ....I posted a while back asking forumites for advice /experience with biggish inverters. I said I wanted to run a wet and dry vac on board, eventually a micro wave, or SWMBO was gonna quit. My thesis was that by using a vac with variable speed control, I could cushion the start-up surge and get away with a 1.5 kw inverter.
While briefly in UK, bought a Skytronic 1.5kw (alleged surge to 3kw) mod sine wave unit from TLC for 234 pounds including vat, which, in haste, was the best price I could find. Thing looks OK, but spidery font used on label betrays oriental origin.
OK, the beast (the inverter, not SWMBO) is now downstairs in my garage hooked up with 25 mm section cable to 4 x 110a/h leisure batteries and a serious charger (its on wheels) to simulate my diesels running.
The results are as follows.
1) With 1000 watt miele variable speed vac, cautiously switched on at 300 watt setting.....bad hunting, oscillating amps consumed, clearly not happy. Same with all intermediate settings
2) Same vac, brought up to full speed..... smooth and nice, consumption 5A at 230vac , and 80 amps at 12v.
3)) take deep breath, switch on miele vac set at full speed. Perfect, momentarily showed 100amps, then back to 80.
4) Plugged in new 1300 watt vac, no vario.....perfect, settled at 100 amps dc and 6 amps ac.
5) Plugged in old 8oo watt micowave, rated at 1050 watts draw....perfect. 80 amps dc. Made nice cup of hot Bovril to simulate life aboard.
6) Plugged in ghetto blaster...pretty horrible on LW MW and SW, but FM not so bad, but still miserable. Almost the same when GB is plugged into regular mains, but with inverter running nearby, so there is rf as well as mains spikes.
First Conclusions :- my thesis that a variable speed control would allow me to use a minimally sized inverter was rubbish. The thing works anyway. I suspect that more elaborate microwaves with microprocessor controls will not work, seeing what happened with the vario speed vac and the ghetto blaster.
Life expectancy? Reliability at sea? Your guess is as good as mine
Hope this is useful.....Cheers....R

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[Gypsy]

Great to hear the results of your tests. Real and objective tests with measurements! When you first switched on the uwave could you see a surge in the DC current? How are you measuring the DC current? Not questioning the results, just interested.

Thanks for the useful info


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[TonyBrooks]

Many thanks for that.

Now we have something more objective to compare vendors claims with.

Tony Brooks

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[steve_cronin]

Similar experiences with mine....

..which is now fully installed on Mary Flavin through a source selector, RCD,earthing plate, isolating switch and mega fuse.

One thing I would modify if I were you is the size of your cable. The 25 sq mm c/s cable isn't rated for the load you will be putting on it. 35 sq mm or even 50 is more like it.

Steve Cronin



<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[Rohorn]

Hi....Thanks for your comments....
First, I forgot to say the ambient temperature was 16.5 degrees, which is hardly Greek summer, so the cooling fan didn't even think of switching on. I'm not serious enough to institute a heat test in my draughty garage, so there's still a question mark over performance in the Aegean.
Second, for the record, the 12v standby current is almost exactly 1 amp. so if one forgets to switch it off, it won't be catastrophic. However, my house rules for it's use will be:-.... only when at least one diesel is running, and with the battery switch on "both", and THEN a special red key switch kept by me. I regard having 220v on board at sea as a serious prospect. With the (late) Honda generator raving away in the cockpit, there was no doubt what was going on. The inverter is silent and clean and less of a hassle....but I suppose, potentially more lethal because of it.

The above measurements derive 1) from a genuine 30 year old Avometer, for up to 10 amps either dc or ac., and 2) the 10-led bar-chart display on the front of the inverter which shows
a) battery voltage in 0.5 volt steps from 10 to 15 v and
b) dc amps in steps of 20 amps from 0 to 200
Regarding the uwave, the surge on the ac side shown by the avometer didn't have the needle hitting the stop, and I don't have a more precise way of looking at the dc surge. Lend me your storage scope and I'll give it a try! These were just tests to reassure myself the system worked, before loading the lot in the van and taking off for Paros next month.
Cheers....R

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[Gypsy]

Thanks for the extra info/comments. All useful. Nice to see the Avo still giving good service. Mine is tucked away in the workshop at home but she gets a bit of work now and then. I have a Link 10 battery monitor fitted in OzSea which is a great piece of kit. It has a digital display of course and whilst it does react reasonably to current surges it doesn't tell you can't really be sure of the maximum momentary current - you have highlighted my sad lack of a storage scope on board. I also have a clip-on DC digital meter which I find very useful for tracking the current draw of various items and to check loads on various key cables.

You are right about guarding the key for the switch. I use a small inverter on board for notebook PCs and "stuff" and it is amazing how easy it is to just suck that current right out of those big batteries even at 5-10A. I found that running the PC became the next largest consumer of AH after the fridge. Too much e-mail and mucking around with digital photos!
Cheers
Ray




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[Rohorn]

Re: Similar experiences with mine....

Hi Steve...you are right of course about cable section...this was for my functional test in the garage. I used bare 7 strand 2.1mm copper household earthing cable, 25mm total section, amazingly cheap here. I am very tempted to use the same stuff on the boat, doubled up, and soldered together at the battery-clamp contact points and all stuck inside plastic tubing, painted red or black!!
Tinned heavy power cable really costs, (especially coloured) and I although I accept the necessity for tinned light cables which might otherwise corrode through in the marine atmosphere, this non-tinned heavy stuff , if tinned at the contact points, could survive pretty well.... As always, it's the ha'porth of tar syndrome.
Cheers....R
Cheers.....R

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[CharlotteRusse]

Re: Similar experiences with mine....

The variable power controls of your vacuum (or a light dimmer) work by choping off part of the AC sine wave cycle. Your modified sinewave inverter doesn't output a sinewave (hence the name) and this is probably what causes the hunting on your vacuum at the lower settings, the controller can't reliably find the zero crossing point. You need a true sinewave converter for things like variable speed drills and vacs to work properly, but a 1.5Kw one would be rather expensive.



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[Rohorn]

Re: Similar experiences with mine....

Hi....yes, I didn't fancy paying out for a true sine wave unit, and in fact the old vario speed vac on the boat was originally bought to give the (late) honda generator an easier life. Now that the Honda has been replaced by an inverter I thought the same would apply. I find that even the new wet and dry vac (1300 watts without vario) starts and runs like a dream...... Interestingly, my Metabo drill variable speed seems unaffected...works OK. I don't know why that should be...I thought all universal motor speed controls worked as you say...thyristor chopping off the sine wave.
One other characteristic of the inverter is that it doesn't always latch on first time....one has to switch it off and on again a couple of times. My small one does the same.
Thanks for you comments....Cheers....R

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