DC Power Connectors

[cuthound]

Another problem of having multiple inverters is that they will not necessarily be in synchronisation (unless they are designed to be and can sense each others output). This means that there may be up to 440 volts between inverters.

 

Therefore they would need to be placed so that it is not possible to touch any two inverters or the appliances connected to any two inverters.

[Chalky]

Another problem of having multiple inverters is that they will not necessarily be in synchronisation (unless they are designed to be and can sense each others output). This means that there may be up to 440 volts between inverters.

 

Therefore they would need to be placed so that it is not possible to touch any two inverters or the appliances connected to any two inverters.

 

Or more interestingly if they're not well filtered you'll get "pulsing" on the 12V supply. Since they'll run at slightly different frequencies you'll get a beat frequency generated as they go in and out of phase - called Hetrodyning. That'll cause some interesting issues...

[dor]

Going back to the OP, I am intrigued to know why you think a DC distribution system with local inverters would be a good idea? There must be something that led you in that direction. Particularly as you appear to be prompting a more Eco-friendly way of distributing power.

 

As has been clearly pointed out, this would be a very expensive and highly inefficient solution, so what prompted you in this direction?

 

I'm not trying to get at you, but I do find it strange that someone who clearly has ideas of ecologically sound off-grid power use should be looking at this as a way of going about it.

[ditchcrawler]

Looking at the OPs blog I don't think he has much idea about boats as he is talking about CC'ing on the Thames at Marlow, having a boat that is air tight, no natural ventilation, cooking by electricity, if that is the inverter he is going to plug in he won't need welding cables but busbars. He also claims that CO would wake you up and not kill you.

[Guest]

 

Or more interestingly if they're not well filtered you'll get "pulsing" on the 12V supply. Since they'll run at slightly different frequencies you'll get a beat frequency generated as they go in and out of phase - called Hetrodyning. That'll cause some interesting issues...

My new favourite word. Can't wait to use that in a conversation

[dor]

Just had a.look at his blog. What an extraordinarily naive man he is. So he is going to have a socket to plug his local inverter into to run his electric hob. I can't be bothered to calculate the sca of the cables he would need for this but they are going to be a bit on the large size!

 

Reminds me a bit about a boat report a few years ago of a guy building an all-electric boat. It's fine he said, I've done all the calculations, I'm a physics teacher. Yet another one who thought his xxx amp alternator produced a constant xxx amps.

 

Whilst I admire people who try and think up different ways, for someone who appears to have done quite a bit of reading up he still thinks he can ignore a lot of things. Does make it quite entertaining though, even if some of his ideas are potentially lethal. Close down all you heat-wasting ventilation cos it's ok, the build up of combustion products will wake you up in time.

[smileypete]

In some cases I agree, but to be honest can see no really abrasive comments here. To my mind people have taken the time and trouble to explain to the OP why the idea might be impractical. Their advice is offered freely and based on experience.

Don't forget that many of us are posting on phones these days which can make the posting style seem a little "abrupt" at times; a trait I have noticed on this and other forums.

People are trying to help/advise in their own way.

I was just replying in kind

 

Sometimes my problem is the opposite, I start editing my reply adding more and more detail to a until it's too much for the poor OP.

 

Close down all you heat-wasting ventilation cos it's ok, the build up of combustion products will wake you up in time.

I think in some ways loads of ventilation can be a poor substitute for some decent CO alarms and well maintained appliances.

 

I'd much rather CO alarms were required by BSS, so there's extra protection if vents get blocked or appliances leak CO for any reason.

 

cheers, Pete.

~smpt~

Edited December 25, 2014 by smileypete

[ditchcrawler]

 

 

I think in some ways loads of ventilation can be a poor substitute for some decent CO alarms and well maintained appliances.

 

I'd much rather CO alarms were required by BSS, so there's extra protection if vents get blocked or appliances leak CO for any reason.

 

cheers, Pete.

~smpt~

Actually its not a problem because what the OP doesn't realise is that for his BSS inspection he needs nether CO alarms or ventilation.

[Murflynn]

Anyway, not sure it matters since OP hasn't returned.

he prob'ly has, but is cowering in the corner dodging incoming flak.

[Groundhog]

Looking at the OPs blog I don't think he has much idea about boats as he is talking about CC'ing on the Thames at Marlow, having a boat that is air tight, no natural ventilation, cooking by electricity, if that is the inverter he is going to plug in he won't need welding cables but busbars. He also claims that CO would wake you up and not kill you.

 

He doesn't claim that. He claims that CO2 would wake him and he's right. It would. Where it goes wrong is as you say, with other gasses.

 

In a similar style to his blog post on the subject there's an experiment you can do at home. Breathe into and out of a bag filled with helium, you'll slip peacefully into death from suffocation without feeling the slightest shortness of breath.

[Murflynn]

just read OP's blog.

 

I should humbly apologise if my post seemed like criticism. This guy knows all the tricks and we are all ignorant twits.

The only reason we need ventilation is because of ill-informed boat surveyors, so clearly we can tell them to get stuffed next time the BSS exam comes round. It's only advisory anyway, innit?

And he is going to move up and down the Thames near Bisham Abbey and moor up wherever he can without cost. Brilliant - why didn't I think of it?

 

On the downside, he won't be burning diesel 'cos he can get sufficient waste engine oil and chip fat to fuel his engine/generator, so don't moor downwind of him.

For a guy whose business is in the energy field he knows sweet FA about DC electrics.

 

Frankly I think we should just let him get on with it and follow his blog for entertainment purposes.

 

 

DUHHH!!

Edited December 25, 2014 by Murflynn

[ditchcrawler]

 

 

The only reason we need ventilation is because of ill-informed boat surveyors, so clearly we can tell them to get stuffed next time the BSS exam comes round.

 

You can, as I said before its only advisory, they can't insist you do it, its your decision.

[Guest]

I was just replying in kind

 

Sometimes my problem is the opposite, I start editing my reply adding more and more detail to a until it's too much for the poor OP.

 

I think in some ways loads of ventilation can be a poor substitute for some decent CO alarms and well maintained appliances.

 

I'd much rather CO alarms were required by BSS, so there's extra protection if vents get blocked or appliances leak CO for any reason.

 

cheers, Pete.

~smpt~

Fair enough feller

[Scholar Gypsy]

I enjoyed his tax strategy:

 

"My fuel usage strategy is to firstly minimise/eliminate my fossil fuel consumption, and secondly obfuscate where ever possible my tax liabilities and my payment of them."

[eco-boat]

Thank you all for your comments.

I will be distributing DC power for LED lighting. I will also use it to power small inverters for the little stuff like phone chargers, shaver charger, tooth brush charger, laptop charger etc.

The suggested DIN connectors look as though they'll do the job.

I just wanted to see how far I could push DC. Cable costs have set a limit on that.

 

Respect to those who weren't derogatory.

[Guest]

Thank you all for your comments.

I will be distributing DC power for LED lighting. I will also use it to power small inverters for the little stuff like phone chargers, shaver charger, tooth brush charger, laptop charger etc.

The suggested DIN connectors look as though they'll do the job.

I just wanted to see how far I could push DC. Cable costs have set a limit on that.

 

Respect to those who weren't derogatory.

I once did similar, but eventually went for DC laptop charger/phone charger etc. It is definitely a more efficient way of doing things than using inverters and suffering inverter losses. Other problems with inverters include the quality of the sine wave, where some chargers will spit their dummy out unless you go for pure sine wave (expensive.)

Not meaning to lecture/belittle your ideas, but I regretted not listening to others on this subject.I ended up buying some things twice.

 

[Theo]

I think some of the responses illustrate why people get 'turned off' by CWDF... a bit more tact wouldn't go amiss

 

cheers, Pete.

~smpt~

I believe myself to be a sensitive person as regards detecting rudeness but I really think that this topic is a model of politeness. the facts are plainly stated as psters see them and there is no personal abuse. There is really no point in dressing up the fact that the multiple inverter idea is not a good one for all the reasons that have been given.

 

Back to the main point:

 

I think that the thinking behind the idea might be that the OP feels that a big inverter is likely to have a bigger quiescent current than a little one. I think that there is a case for not using 12V at all. If you invert and use 230V throughout there are no problems with cable sizing and voltage drop.

 

N

[ditchcrawler]

Thank you all for your comments.

I will be distributing DC power for LED lighting. I will also use it to power small inverters for the little stuff like phone chargers, shaver charger, tooth brush charger, laptop charger etc.

The suggested DIN connectors look as though they'll do the job.

I just wanted to see how far I could push DC. Cable costs have set a limit on that.

 

Respect to those who weren't derogatory.

Well I am glad you are still here as others have said there is lots of advice available on here, its up to you which you chose to listen to, that's a decision we all have to make when we conflicting views and suggestions.

[dor]

I will also use it to power small inverters for the little stuff like phone chargers, shaver charger, tooth brush charger, laptop charger etc.

 

 

You might like to be aware that small MSW inverters are notorious for destroying small switched-mode power supplies such as used in stuff like phone chargers, shaver charger, tooth brush charger etc. I also have direct experience of it. Hence I try and run most things off 12V, otherwise through main PSW inverter (tooth brush gets only gets charged when something else is using the inverter!).

[Chalky]

I am intrigued to know why you think a DC distribution system with local inverters would be a good idea?

 

It's actually not that un-common for electric drive systems. The DC distribution is at between 300 - 600 V for cars and about 6kV for ships. Absolutely deadly if you don't know what you're doing.

[Paul C]

Thank you all for your comments.

I will be distributing DC power for LED lighting. I will also use it to power small inverters for the little stuff like phone chargers, shaver charger, tooth brush charger, laptop charger etc.

The suggested DIN connectors look as though they'll do the job.

I just wanted to see how far I could push DC. Cable costs have set a limit on that.

 

Respect to those who weren't derogatory.

 

I missed the first round of "advice giving" but with the 2nd post, I can recommend that even with low power devices such as phone chargers, laptop chargers etc that the inverter is sited in one place (near the batteries) and power is distributed via 230V AC, not by using long runs of 12V DC. The reasons are already given, and are the same: Ohms' law. Once you get away from miniscule current draw devices such as phone/shaver chargers, then what one might call a "medium" current draw (the likes of a laptop charger, for example) will create a voltage drop significant enough to possibly trip the inverter into an undervoltage condition in a worst-case scenario of lowish SOC of batteries (and no charging option - late at night, can't run engine, no solar, etc) and the laptop being used + needing its battery charged. You may as well use slightly thicker 230V cabling so it could be used for any/multiple 13A devices, given a suitable inverter running it. This will save having to re-do the wiring later on.

 

Not read the blog but not sure of the practicality of electric cooking on a boat. (Might be tempted to read blog).

[Paul C]

Update: yes, as suspected, after looking at the blog electric cooking is going to either hammer the batteries/inverter, require a large/expensive battery bank and inverters, or require the engine or generator being run to allow cooking. If "eco" is to be considered, then the efficiency of running an engine or generator, to generate electricity, to heat a hob up, to cook something is going to be approx. half that of cooking on gas. Given the likely difficulty in obtaining free veg oil, I reckon he'll end up burning diesel - therefore no more eco-friendly than gas.

[dor]

 

It's actually not that un-common for electric drive systems. The DC distribution is at between 300 - 600 V for cars and about 6kV for ships. Absolutely deadly if you don't know what you're doing.

Fair point. It's the voltages that is the issue on a boat though rather than type of waveform and I was just referring to DC v AC in their normal voltages.

 

Interesting that ships use 6kV DC for distribution; what is the advantage in that situation using DC over AC?

 

Now wouldn't it be interesting if 600V DC was the standard distribution voltage...

Edited December 28, 2014 by dor

[Murflynn]

We used 120V DC for some refinery circuits. Cables as thick as your arm which needed to be mounted on heavy structural steel bracing to counteract the twisting effect (remember the right - or was it left - hand rule for DC motors we learned at school).

[Guest]

We used 120V DC for some refinery circuits. Cables as thick as your arm which needed to be mounted on heavy structural steel bracing to counteract the twisting effect (remember the right - or was it left - hand rule for DC motors we learned at school).

Flemming's possibly?