Electricity in your Motor Home for Dummies

[londontavern]

A jolly good document but that memorable lady 'Ivy Watts' never got a mention and should not be fogotten.

 

[harrow]

V
I R the electricians triangle

and

W = V x A

https://www.electronics-tutorials.ws/dccircuits/dcp_2.html

 

[rockape]

I belong to an owners group and am amazed at how many basic 12v & 240v questions are raised.

My personal favourite was from a guy who asked why his 240v Micro wave and Electric kettle didn’t work when he stopped for a brew up in a layby. He was planning to demand the dealer fix this under warranty, but luckily someone posted the answer in time to stop him.

So with a little time on my hands, and for various domestic reasons unable to get away, I produced a word document on the subject to add to the "files" section of the group.

It occurred to me that some people in this group would be interested by some of the bits in it, hence this post.

It is not intended for the many experts in the group who know far more than I about such things, just to help any newbies (or oldies) who have electrical questions. Please treat it as such and be gentle with your comments.

How much power do indeed to run my MH hot tub??

 

[harrow]

How much power do indeed to run my MH hot tub??

A 15kg bottle of Calor gas

 

[r4dent]

but this did jump out at me: "Live and Neutral"

Good point - corrected in latest version

 

[r4dent]

Instead of just Watts being Volts X Amps, would it have been too complex for readers to explain V/I = R ?

If they don't know about Ohm's Law I see little point introducing the concept of resistance.

Most people know batteries are 12v and most appliance have a label with watts, but some people don't know how to work out the current.

That's why I did what I did.

I did not see an explanation of the fact that most of the 12v supply relies not on a positive cable feed and an negative cable return to complete a circuit, but on the -ve of the circuit being through the vehicle chassis. That therefore the negative connections must be kept in good order. This being a frequent cause of malfunction.

[Small point but current EU voltage is nominal 230v - but that allows from 220v to 240v I believe. I mention it in case someone thinks their equipment will not work]

Two excellent points, I've amended the document to include them.

Thanks for the positive comments

 

[r4dent]

A jolly good document but that memorable lady 'Ivy Watts' never got a mention and should not be fogotten.

Whoops - watt a mistaka to maka !

I also forgot about Charlie Watts (not sure who the other guy is!)



and, of course, Den & Angie.


On the plus side, those in the know will get the references to James

 

[phillybarbour]

Super any for many to read, I am surprised just how many new people think the 240v should work when they plug the kettle in anytime.

 

[wildebus]

Super any for many to read, I am surprised just how many new people think the 240v should work when they plug the kettle in anytime.

There is also a remarkable disconnect between the ability to store power and the desire to use power for a lot of folk.

In other words, the idea that all that is needed to use bigger appliances is to buy a bigger inverter, with no thought of where the extra power will come from.

 

[bullfist]

Some minor comments.

Don't know whether a brief description of difference between AC and DC may be beneficial or confusing (probably the latter).

Solar panel output table, very useful. Solar Panel buyers need to realise that they will get the expected power output only under a certain set of conditions (i.e. on the equator, directly under the sun).

Wiring in an extra battery. 99% of the time this will work, but can be a problem once one battery fails and the other is still good. That's why they recommend a separate fused output from each battery.

-steve

 

[Caderman]

Electricity in your Motor Home for Dummies new version

I belong to an owners group and am amazed at how many basic 12v & 240v questions are raised.

My personal favourite was from a guy who asked why his 240v Micro wave and Electric kettle didn’t work when he stopped for a brew up in a layby. He was planning to demand the dealer fix this under warranty, but luckily someone posted the answer in time to stop him.

So with a little time on my hands, and for various domestic reasons unable to get away, I produced a word document on the subject to add to the "files" section of the group.

It occurred to me that some people in this group would be interested by some of the bits in it, hence this post.

It is not intended for the many experts in the group who know far more than I about such things, just to help any newbies (or oldies) who have electrical questions. Please treat it as such and be gentle with your comments.

Appreciate this is an old post but thought worth a reply as I was referred to it by a recent article. I‘m always interested to learn more so read your guide with interest. I was puzzled for a while with your Hours = [ Nominal Capacity (Ah) *6 ] / Watts] formula , am I right to assume that your use of ‘6’ (rather than 12) reflects the fact that on some batteries you can only use 50% of the nominal capacity?
if so as it’s intended for newbies It might be helpful to explain that as it’s not unreasonable for newbies to think that a 100ah nominal might give 100ah usable. Also diffferent types of batteries provide different levels of usable power.
When starting out on my Campervan journey 4 years ago I was On a steep learning curve , especially on leisure batteries and electrics and so found advice from people with knowledge invaluable, so thanks for doing this. It might also be worth explaining that the amp hour table can be significantly affected by cloud, shade , angle of solar panel.

Electricity in your Motor Home for Dummies new version

I belong to an owners group and am amazed at how many basic 12v & 240v questions are raised.

My personal favourite was from a guy who asked why his 240v Micro wave and Electric kettle didn’t work when he stopped for a brew up in a layby. He was planning to demand the dealer fix this under warranty, but luckily someone posted the answer in time to stop him.

So with a little time on my hands, and for various domestic reasons unable to get away, I produced a word document on the subject to add to the "files" section of the group.

It occurred to me that some people in this group would be interested by some of the bits in it, hence this post.

It is not intended for the many experts in the group who know far more than I about such things, just to help any newbies (or oldies) who have electrical questions. Please treat it as such and be gentle with your comments.

 

[r4dent]

am I right to assume that your use of ‘6’ (rather than 12) reflects the fact that on some batteries you can only use 50% of the nominal capacity?
if so as it’s intended for newbies It might be helpful to explain that as it’s not unreasonable for newbies to think that a 100ah nominal might give 100ah usable. Also diffferent types of batteries provide different levels of usable power.

Yes that is exactly why I use 6.
The fact that basic lead batteries only give 50% of the nominal capacity is in a different part of the document.
Remember the target market is people who expect the 230v devices to work in laybys.
People who fit more technical batteries tend to know about their performance.
I tried to keep to basics.

 

[merl]

Yes that is exactly why I use 6.
The fact that basic lead batteries only give 50% of the nominal capacity is in a different part of the document.
Remember the target market is people who expect the 230v devices to work in laybys.
People who fit more technical batteries tend to know about their performance.
I tried to keep to basics.

Here we go again....
Lead batteries only give 50% capacity...
Not accurate and an all too common misconception. Sorry to criticise but this sort of off hand remark hinders when it comes to enlightening people.

 

[r4dent]

Here we go again....
Lead batteries only give 50% capacity...
Not accurate and an all too common misconception. Sorry to criticise but this sort of off hand remark hinders when it comes to enlightening people.

Please read the context. The document and the thread are entitled "Electricity in your Motor Home for Dummies".

The document was aimed at newbies who don't under stand why the micro wave doesn't work in a layby.

I still maintain that 50% is a valid rule of thumb for such people who may otherwise think a 100 ah lead battery will provide 100ah.

Please feel free to produce "The Truth, the whole Truth & nothing but the Truth about Electricity in your Motor Home". I for one, wold find it very useful.

 

[merl]

Ok, I'm sorry if you feel offended, I did include a 'sorry' in my post. Now, I'm going to say more, non of which should be taken as a personal poke because it's not meant that way, it's just me pointing out what I feel to be the wrong information that gets repeated time after time (hence the here we go again remark)
My post was a reaction to your post above NOT what you've written in your guide which I haven't read but I'm sure is very good.

50% maximum discharge makes little sense, would 60% be so much worse? Would 40% be so much better? The fact is that damage gets worse the deeper you discharge, Period. But you also get more capacity so it's a trade off.
I've used the smoking analogy before which I'll repeat.
No fags is best
Chain smoking is worst.
A rule of thumb saying "30 a day is ok" is the battery equivalent of the 50% rule.
One fag ain't going to kill you and 1 deep discharge won't kill your battery either but I've actually seen a 'knowledgeable' poster on another forum saying that it would, so deeply has this 50% nonsense been regurgitated over and over.
Sorry but as you see I don't agree when you say that 50% is a valid rule of thumb and, if you have suggested the same in your article then I think you should consider changing that part for something else possibly with a chart plotting cycles Vs depth of discharge (they can be easily found for virtually all leisure batteries) which says a thousand words.
Anyone who can understand the nominal capacity calculation which you included shouldn't have a problem grasping the graph and I guess actually factual and helpful to not only the newbie but for most/many not so newbies too.
You've taken the time and effort to write your article and I praise you for that but don't keep regurgitating the same old crap mate, you're better than that.

 

[trevskoda]

WEll that was on a plate.

 

[merl]

WEll that was on a plate.

Thanks for the positive comment Trev , I must admit I usually take your input as the acid test

 

[Caderman]

Yes that is exactly why I use 6.
The fact that basic lead batteries only give 50% of the nominal capacity is in a different part of the document.
Remember the target market is people who expect the 230v devices to work in laybys.
People who fit more technical batteries tend to know about their performance.
I tried to keep to basics.

Ok, I'm sorry if you feel offended, I did include a 'sorry' in my post. Now, I'm going to say more, non of which should be taken as a personal poke because it's not meant that way, it's just me pointing out what I feel to be the wrong information that gets repeated time after time (hence the here we go again remark)
My post was a reaction to your post above NOT what you've written in your guide which I haven't read but I'm sure is very good.

50% maximum discharge makes little sense, would 60% be so much worse? Would 40% be so much better? The fact is that damage gets worse the deeper you discharge, Period. But you also get more capacity so it's a trade off.
I've used the smoking analogy before which I'll repeat.
No fags is best
Chain smoking is worst.
A rule of thumb saying "30 a day is ok" is the battery equivalent of the 50% rule.
One fag ain't going to kill you and 1 deep discharge won't kill your battery either but I've actually seen a 'knowledgeable' poster on another forum saying that it would, so deeply has this 50% nonsense been regurgitated over and over.
Sorry but as you see I don't agree when you say that 50% is a valid rule of thumb and, if you have suggested the same in your article then I think you should consider changing that part for something else possibly with a chart plotting cycles Vs depth of discharge (they can be easily found for virtually all leisure batteries) which says a thousand words.
Anyone who can understand the nominal capacity calculation which you included shouldn't have a problem grasping the graph and I guess actually factual and helpful to not only the newbie but for most/many not so newbies too.
You've taken the time and effort to write your article and I praise you for that but don't keep regurgitating the same old crap mate, you're better than that.

A rule of thumb.= A rough and useful principle or method, based on experience rather than precisely accurate measures.
it is in that context that r4dent and many others ( E.g 12volt Planet) use 50% and imho is entirely appropriate in the context it was used. If you don’t find it useful then that’s your call.

 

[andromeda]

Well done. Looks good.

I did not read to the end as I do know most of it from schooldays.

Just a couple of suggestions:-

Instead of just Watts being Volts X Amps, would it have been too complex for readers to explain V/I = R ?

I did not see an explanation of the fact that most of the 12v supply relies not on a positive cable feed and an negative cable return to complete a circuit, but on th-ve of the circuit being through the vehicle chassis. That therefore the negative connections must be kept in good order. This being a frequent cause of malfunction.

[Small point but current EU voltage is nominal 230v - but that allows from 220v to 240v I believe. I mention it in case someone thinks their equipment will not work]

These are not criticisms of an excellent paper, just possible adjustments, but up to Editor's discretion as to being to complex.[Wink]

Geoff

Sorry Geoff you lost this airhead at your first paragraph

 

[trevskoda]

Thanks for the positive comment Trev , I must admit I usually take your input as the acid test

Must admit its well past the cell by date.