Follow ups, Feedback and MORE questions

Submitted: Wednesday, Oct 16, 2013 at 03:18
ThreadID: 104739 Views:1906 Replies:4 FollowUps:7
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Hi all,
Back on the 23rd of July - thread 103384 – I asked about running an electric blanket off an inverter. The simple reason for asking the question was simply because both of us had not been well, we were committed to a few weekends working as volunteers and the experiment of running an electric blanket off an inverter was all about .... whether it had been done or could be done.
There were a number of responses and a number of somewhat entertaining responses and a few that did nothing to answer the original post (at all) in its pure form. As a follow up to the archived thread..........It can be done and the 150w SCA inverter ran one half of the double electric blanket on the second setting and achieved the desired result, which was to simply - take the damp and cold chill out of the bedding. Job done!!
I also asked about “Must See” places in Karijini N.P. thread 104371
BIG THANK YOU!! to the people that replied and offered “places to see” information!! Unfortunately we are unable to visit the area at any other time than this and we are fully aware that it WILL be HOT! We will be walking when the conditions permit and in the cool blast of the aircon when out travelling. Our thanks to Equinox for the stunning Karijini video (insert LIKE) we are now just three big sleeps away from heading off. It is also nice to hear from srddean, too!

Now to the always.
1/ Do I need a DC to DC charger to charge the (3) batteries in the C.T. when there is a 120 amp alternator under the bonnet and heavy cable between them?

2/ Do country moths REALLY know that they are NOT attracted to LED lighting. We have photographs that indicate they are.

3/ How can you test, without an oscilloscope, what the wave output is like from your inverter. Yes, it is sold as a “pure sine wave inverter”.

4/ Why is the coaxial cable for a 5 watt output UHF radio, the same as the coax for a HF radio with a 100 w output?

5/ How many people have followed Robin Miller’s “microwave off an inverter”? From thread 97743.

It is interesting to note that the inverter in Robin’s story, is the same as we have just bought as an upgrade.
A note to Robin, is the inverter still working to expectations and advertised specifications?
As an aside to this, we have followed his previous advice on fans in the camper and we run a small (150 w) inverter and a box fan. While the pedestal fan seemed to be a great idea, the box fan fits in better.
Safe travels everyone.
Wayne & Sally.
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Reply By: Sand Man (SA) - Wednesday, Oct 16, 2013 at 07:30

Wednesday, Oct 16, 2013 at 07:30
1/ Do I need a DC to DC charger to charge the (3) batteries in the C.T. when there is a 120 amp alternator under the bonnet and heavy cable between them?

No, you don't necessarily "need" a dc-dc charger.

Will the batteries benefit from a dc-dc charger?
Most certainly.
Although the alternator output should be adequate in an ideal situation, a long cable run to a camper is asking a lot. This is where a good dc-dc charger comes into its own.
With the charger placed in the camper, close to the batteries, it will boost the voltage level to the optimum amount to efficiently charge the battery bank and once charged, maintain the batteries in the best condition.

You can do no wrong in investing in a dc-dc charger.
I'm happy with my Ctek D250S Dual, with its solar port capability.
The Redarc BCDC1220 and BCVDC1240 units are also worthy of consideration but a bit more expensive than the Ctek.


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AnswerID: 519776

Follow Up By: Wayne's 60 - Wednesday, Oct 16, 2013 at 10:23

Wednesday, Oct 16, 2013 at 10:23
Hi Bill,

Thank you for taking the time to reply to my question about DC-DC chargers. I always wondered about the need for one and the value of a unit where the output is much lower than the alternator. We are not into the solar power area yet. on reading about the Ctek D250S Dual I can see the benefit.

Wayne & Sally.
FollowupID: 800042

Follow Up By: Member - Sn00py2 (NSW) - Wednesday, Oct 16, 2013 at 12:20

Wednesday, Oct 16, 2013 at 12:20
Hi Wayne & Sally,

If you rely on the alternator which will be charging your starting battery as well as the batteries in the camper trailer, you will get by to some extent. The alternator will read the average charge across all your batteries and charge accordingly. This could and probably will result in some batteries being over charges and others undercharged. Over charging can cause battery failure which you want to avoid. This will be complicated by the distance between the batteries in the CT and the alternator. The likely result is that you will overcharge your starting battery and undercharge your CT batteries.

With a DC/DC charger, the alternator will charge your starting battery as per normal and the DC/DC charger, mounted as close to the CT batteries as possible, will then charge the CT batteries properly. Yes you are correct in that the CTEC D250S output is only 20 Amps compared to the 120 Amps from the alternator. While the D250S will put up to a genuine 20 Amps into the batteries, charging direct from the alternator will be greatly reduced due to (a) voltage drop on a long cable run and (b) the charging amps"clouded" by your starting battery.

I use a D250S and my CT batteries get a full charge. The key is to make sure that you have heavy cables run all the way through to the CT. I use 70Amp cable for the job with Anderson connectors.

Hope this helps.

FollowupID: 800050

Follow Up By: Wayne's 60 - Thursday, Oct 17, 2013 at 03:00

Thursday, Oct 17, 2013 at 03:00
Hi SnOOpy 2.

Or is that SnOOpy also??

Thank you for your reply, it is an issue that I had not previously considered and we will follow up on that.
Safe Travels.

Wayne & Sally.
FollowupID: 800124

Reply By: Robin Miller - Wednesday, Oct 16, 2013 at 13:32

Wednesday, Oct 16, 2013 at 13:32
Some tricky questions Wayne.

As I have some cro's I never thought about ways to check if its sine.

Heres a cute trick though if you have a cheap (non RMS ) reading voltmeter.

A cheap non-rms one will not read AC voltage correctly , its is calibrated so that it will read approximately correct on normal 230Vac , it will read quite differently on pulse waveforms.

For example I have both types of meter and they read about the same on my 1kw sine wave unit.

When I put the 2 meters onto my 150w Powertech can non-sine inverter my true rms meter reads 245vac and my cheapie reads 218v.

Note when doing above readings its best to have no load connected. A load moves the output waveform from very pulsee towards more of a square or stepped square wave and the cheap meter reads a little more towards the reading of a ture rms meter.
Also do not expect same readings as me as there are different implementations of pulse based inverters and their load management.

Remember a "Square/pulse wave" item generates more harmonics that is higher frequencies and more hash and noise in radios.

A "Square/pulse wave" also will rattle a transformer a lot more , and cause more nasty noisies in senstive Hi-Fi gear.
( My microwave has a hernia off my 1.5kw square wave inverter and its panels rattle)

Not all things work on pulse waveforms - but thats a little product specific.

The same coax is ok because the losses are very low and not enough to heat or damage the cable when 100w is used.

If there 2 piles of money, 10 bucks in one and 1000 bucks in the other and you are allowed to pick up just 1 -- then thats why moths go to even LED lights of the correct anti-moth color if no other brighter light source is around.

Agree with everyone, not really necessary.

There are specific circumstances where DC/DC is more efficent though.
I.E. I don't use a genny or solar but sometimes when camping run the engine at idle to re-charge and a DC/DC can be more efficent then.

My inverter microwave stills works the same as I recorded how long it took to heat some water and its still within 10%.

To be fair though I don't use this combo very much.

Robin Miller

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Follow Up By: Wayne's 60 - Friday, Oct 18, 2013 at 03:30

Friday, Oct 18, 2013 at 03:30
Hi Robin,

Please accept my humble apology for including you in my,
"A "one reply to all" is here ....... Thank you :-)" reply.

I asked specific questions of you and you responded to them and I appreciate that you responded to them.

Thank you!!

Q1. I have a better understanding of the DC-DC charger scenario than I had before. Thank you!

Q2. Like a Moth to a Flame, good title for a song. Thank you for the addition anecdote :-))

Q3. Thank you for the suggestion to test the compatibility of an inverter and I am aware that modified inverters do cause "noise" in some appliances. I did say to Sally that you appeared to be an engineer because of the information and structure of your replies to questions asked on the forum. The issue with the alternator looking at the (one) battery and then over charging it - courtesy of snOOpy2 is an angle not previously considered.

Q4. Simple answer to a simple question. Though it has always been said that with regards to wiring, bigger IS BETTER.

Q5. :-)

Thank you again for your comments.

Wayne & Sally.
FollowupID: 800197

Follow Up By: Robin Miller - Friday, Oct 18, 2013 at 08:20

Friday, Oct 18, 2013 at 08:20
Hi Wayne

I didn't see the other comments till you noted them - to comment , there is very little likely hood of overcharging any battery by your car alternator - I could think of a couple of extreme senarios but really not a concern - not charging the CT battery quickly enough on short runs is probably the only downside.

I love to do tests and if you like to play with that stuff and re-assure yourself get one of these , and a cig socket extension cable.
(can't believe the price)

When plugged into your cig lighter socket you will see how as the car warms up the charge voltage drops - the cars management systems are designed to not overcharge its battery and thats why they last for years.

Plug your 12v meter into the CT and take extension coord back to car so you can read volts when driving as a test.

The above item is quite accurate for its cost.

Yep , been an engineer in this stuff forever - almost retired (well until Vic decided to build more new trains in Dandenong. )
Robin Miller

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FollowupID: 800203

Follow Up By: Wayne's 60 - Saturday, Oct 19, 2013 at 03:59

Saturday, Oct 19, 2013 at 03:59
Hi Robin,

Time and tide are against me/we/us at this point in time.

From both of us at this point in time, a VERY brief ......................Thank you!!

You are one of a number of Explor Oz forum members that we follow.

Safe travels.
Wayne & Sally.
FollowupID: 800294

Reply By: Member - Duncan W (WA) - Wednesday, Oct 16, 2013 at 15:56

Wednesday, Oct 16, 2013 at 15:56
Wayne I know next to nothing about electrics so I'll not comment about that BUT LED's and moths that's another thing.

In September in the Gascoyne the moths and bloody big beetles were prolific and were definately attracted by my white LED strip light. Ended up with beetles throughout the back of the Troopy and in my drawers.

On my Fluro I have the yellow filter fitted and that has helped in the past so I presume the yellow LED's would do the same.

Now if you can find a way to keep flies away you'll be a marvel and thank heavens they disappear at night.



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Follow Up By: Wayne's 60 - Friday, Oct 18, 2013 at 03:44

Friday, Oct 18, 2013 at 03:44
Hi Dunc,

A big thank you for your reply, and your qualifier for replying to only one of my questions is greatly appreciated!

We may have to pack some yellow cellophane to wrap the brighter lights with. We are all good with having extra protein, though the appeal diminishes when the protein is trying to "limp wing" out of your dinner :-)

BTW, flies disappear at night because they are driven off by the MOZZIES. :-))

We look forward to bumping into you on a WA track, sometime soon.

Wayne & Sally.
FollowupID: 800198

Reply By: Wayne's 60 - Thursday, Oct 17, 2013 at 02:57

Thursday, Oct 17, 2013 at 02:57
Hi All,

As always, the Explor Oz Forum Crew have delivered information .... where others have not done so well.

A "one reply to all" is here ....... Thank you :-)

Safe travels.

Wayne & Sally.

AnswerID: 519841

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