Basic Electrics for Motorhome and Caravan Owners (Part 2)

This is the second (and final) part of my introduction to basic electrical theory – for owners of motorhomes and caravans.  In this section we will look at watts (and we all know that solar panels are rated in watts) and also the connection of batteries in both series and parallel. But before we launch into all of that, let’s take a quick review of what we learned in part one…

(If you have not read part one, you can get to it by clicking here)

Volt = unit of measurement of electrical pressure (very similar to water pressure).

Amp = unit of measurement of the rate of electrical current flow in a conductor (much like measuring the flow of water in a hose).

Ohm = unit of measurement of a conductors ability to resist current flow (like measuring the resistance that a partly closed tap excerpts on the flow of water in a hose).

Remember, these are just new words for concepts you already understand!

Now, let move forward and take a look at watts…


Ok, so what are watts?

The short answer is that the “Watt” is a unit of work done over time. More watts, then more work is getting done quickly, less watts means less work.

So how does this relate to water?

Think of it this way … Say you had that 10,000 litre tank filled with water and you had a wide open valve going to a fire hose and you decided to have some fun and point the hose at all your mates standing 2 metres in front of you. I bet that you could knock them all over in no time and make a big mess at the same time.

Now suppose you only had just 100 litres of water and a small garden hose. Well the results would not be as spectacular.

I really doubt you could knock ya mates over with the stream of water from a garden hose and after a few seconds of drenching them, you would be dropping that hose and running away from some wet and angry friends.

The same is true with electricity. Lots of volts (pressure) and amps (flow) with little ohms (resistance)means a lot of watts worth of power. Low volts and low amps with high ohms means much less power. Increasing either volts or amps while leaving the ohms the same will increase watts. Here is a point of reference to help you gauge how much work a watt of electrical power is worth…

745 watts is equal one horsepower.

So horsepower is just another way of measuring work done – just as you can measure weight in either kilos or pounds. So that means that a 100 watt bulb is actually a little over 1/8 horsepower.

OK, so watts represents power (work over time) and to get lots of watts you need lots of volts AND lots of amps.

This is an important concept to understand when it pertains to the performance of your electric fridge, pump, light or even your power tools.

Just a little bit more math

The watt is represented by the letter P in electrical formulas (P is for Power)

Watts are equal to the number of Volts times the number of Amps  (V x I = P)

or

The number of Amps times the number of Amps times the number of Ohms (I x I x R = P)

or

The number of Volts times the number of Volts divided by the number of Ohms (V x V / R = P)

In a commercial wattmeter, volts and amps are measured and simply multiplied automatically for you.

So how does this relate to the solar panels we have bolted to the top of our caravan/motorhome roof? Well as we add more panels, we are adding more watts of solar. Because of the way we will connect these extra panels (in parallel – more on this in just a moment), we will be leaving the voltage the same, using the extra watts to boost the current (flow of electrons into the battery) and charge our battery more quickly.

About Batteries!!!

Batteries  aren’t rated in AMPS or Watts; they are rated in Ah, what is that?

Well they are actually rated in amps (sort of) that’s what the “A” in Ah is for.

The hour part of the amp hour rating is simply that, its how many amps a fully charged battery can provide for a solid one hour. At least that is the theoretical meaning (reality is a little different)! So a 100 Ah battery should provide (in theory) 100 amps steadily for exactly one hour. So what if you change the load resistance (electric tap) so that it only draws 50 amps?

Well, that battery would supply 50 amps now for 2 hours since it is flowing out only half as much as before.

Think of those trillion trillions of electrons coming out half as fast. It will take twice as long to get them all out.

It works the other way too. If you draw 200 amps out of your 100 Ah battery then you would exhaust the battery at twice its rated capacity and it will be flat in just half an hour!

So the amp hour number is simply a measure of capacity or size. It’s just like comparing a 10,000 litre water tank to a 500 litre tank! You know that the 10,000 litre tank will last longer dumping out at the same rate.

So you now have some practical information here. You can see why a 200 Ah battery will run your microwave for twice as long as a 100 ah battery.

Let’s take a look at how we can connect multiple batteries…

Batteries in Parallel

Here is another interesting bit of information. When you parallel two similar batteries (done by connecting plus to plus and minus to minus) they each help each other handle the load so that you now have double the capacity. So two 100 Ah batteries in parallel act like one big 200 Ah battery. With batteries in parallel we are not changing the voltage at all – we could add 100 batteries in parallel and still have just 12 volts .

battery_series_parallel1

Three similar batteries in parallel are triple and so on… Usually this is done for cost, availability, space or handling reasons (just try lifting a 1000ah battery). Reminder – paralleling a battery doesn’t increase the voltage. The voltage remains the same. It is just like having two water storage tanks side by side and combining them to flow from a single tap.

The tap will run twice as long but the pressure will be the same as with one tank.


Batteries in Series

Now suppose you stacked one big water tank on top of the other and connected them together. The weight of the water would be double so the pressure would double. This is the same with batteries. If you hook two batteries up in series, (plus to minus) the voltage will double. Three will triple and so on.

In the case of motorhomes and caravans, batteries are connected in series to get the desired system voltage. For example, a caravan might have two large 6 volt batteries connected in series to give 12 volts. A large motorhome might have two large 12 volt batteries connected in series to provide 24 volts (it is just as valid to connect four 6 volt batteries in series to give the same 24 volts).

It is also common (particularly in very large motorhomes) to use a combination of series and parallel to create banks of batteries that are then connected together to give a very large capacity. Once connected, these banks of batteries (electrically speaking) look like and act like, one huge battery.

Quick review of what we have learned…

  • Watts is “Work being done” (just like horse power).
  • Watts can be calculated by multiplying volts by amps (P = V x I)
  • Batteries in parallel – voltage remains the same – AH capacity increases.
  • Batteries in series – voltage increases – AH capacity remains the same.

Here is the full version of Ohms law in the format that I used when I was learning it as an apprentice electrician.

Here is how it works…. Look at the inner circle, use the coloured quarters as a “to find”.  For example – to find WATTS, look at the blue P – WATTS inner section. Any of the formulas in the three blue outer sections can be used to find watts.

ohmslaw1

Conclusion

Congratulations you have now learned the basics of electrical theory. But this is not just a theory, I use this stuff every time I am installing, fault finding or repairing anything electrical. Understanding this stuff is not difficult and a basic grasp can be of enormous help when designing, installing and repairing caravan and motorhome electrical systems.

I hope you have both enjoyed reading and learned something from this tutorial. As always, you are invited to comment by using the “Leave a Reply” box below. Thanks for reading.

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39 Responses to “Basic Electrics for Motorhome and Caravan Owners (Part 2)”

  1. Motorhome and Caravan Info Australia » Blog Archive » Basic Electrics for Motorhome and Caravan Owners (Part 1) Says:

    […] and Caravan News Australia « Installing Solar Panels on a Motorhome or Caravan Basic Electrics for Motorhome and Caravan Owners (Part 2) […]

  2. Rob & Rose Says:

    You know the best part of this bus/motorhome caper is that I’m actually using some dusty little brain cells that haven’t seen the light of day in years. Keep this good basic info coming! My mind is a sponge!!!

  3. Ron Says:

    Great info for beginners, it really helped me to understand the basis. Thanks and enjoy your travells.

  4. Pamela Says:

    I am 69 and have never ever understood electricity with its watts and amps and volts, I just know that I would not ever want to be without it for very long. I am a solo and intending very soon to buy a motorhome and I definitely want to have solar power. After reading some of your articles about the process (I am now totally exhausted) have some concept that there is a very definite need to get the whole thing right!! I will be buying a used motor home (have sort of set my heart on a “Coaster”) and was wondering if rather than looking for one already with solar panels which I would have no idea about, would it be better to get a bus without and then get exactly the right system added? Any advice would be very appreciated I am feeling a bit daunted by the whole process.
    Regards Pamela

  5. Hobo Says:

    Hi Pamela,
    Firstly – well done for wanting to get out there. It is and awesome country to explore and you will have a fantastic time.
    I tend to agree with your thoughts on adding a full system rather than dealing with something that may or may not have been done right.
    The only issue may be that if the motorhome has not ever been used away from 240v – it is very likely to have appliances that are not well suited to being powered from solar. For example the fridge … if the vehicle has no solar, then the fridge will either be a three-way (gas) (of which I am not a fan) OR a standard 240v household fridge – these are not suitable for use on solar power due to the power requirements. A fridge running from solar needs to be a low-voltage compressor type (preferably a Danfoss compressor type).
    If the reason for wanting solar in your motorhome is to allow for free camping – I suggest having a look at my article on setting up a motorhome for free camping. You will see from this that there is a lot more to consider that just the power side of things.
    I am very happy to help and provide any advise I can – just ask.

    Gavin

  6. Daryl stone Says:

    Thank you so very much for your commonsensical approach to what can be an absolute nightmare trying to get consistent and accurate info from “solar specialists” ,I have just purchased a 1968 bedford looks very similar to yours { not quite as easy on the eye as yours yet } however I have been trying to get info from previously mentioned “solar specialist ” with not much joy , apart from how much money they can relieve me of , so my question to you is I am thinking 5@200w 12v panels +5@200 ah batteries , 5kva generator what regulator, inverter , shunt/s would I be looking at, I am also hoping to have my gen cut in when batteries are low, I know it seems a s@#t load of power however I would rather have to much than not enough I will be dry camping using 240v fridge, washing machine, 30″led tv dvd, aircon, so on ,any advise, diagrams, HELP would be greatly apriciated , hope to see you out there somewhere in the not to distant future regards Daryl

  7. Hobo Says:

    Hi Daryl,
    Thanks for the posting. It sounds like you have quite an electrical system planned for your bus. I see nothing seriously wrong with what you are suggesting – but here are a few comments…

    1. I would recommend that if at all possible you convert the house electrical system to 24v instead of 12v. You are planning a fairly large system and this is very difficult to do successfully at 12v. Example – at 12v your theoretical maximum charge from 1000w of solar is 83amps – you will find your choices of regulators very limited at this current. If you wired them as 24v (in pairs) the current would be a more reasonable 41amps – a Plasmatronics PL40 or PL60 would manage this current well. The cable required to carry 83amps at 12v would be massive.

    2. Five times 200ah batteries is probably over-kill. If you go to 24v (as you should) then 4 X 200ah should be heaps.

    3. I assume you know that you can not run aircon from solar – you will have to run the generator for that – 5 kva should be fine.

    4. With this size system you are going to need a very large multi-stage battery charger – 80 – 100amps.

    5. A single 200amp shunt will be all you need to track the system.

    6. You will need and DC-DC converter to convert the 24v to 12v for the few things that need 12v (phone changers etc). 15 – 40amp depending on what you intend running from 12v.

    Good luck and please let us know how it progresses and what you decide on.

    Cheers

    Gavin

  8. Daryl stone Says:

    Hi Gavin thanks for your rapid response and thanks for pointing out the 24v system I read one of your articles that mentioned you where having trouble with your 12v lighting did you sort that out? was thinking of running a 4000w inverter do you think that is to much not forgeting I have a 12yo son that likes his xbox , are you running a 12v fridge? I am thinking of running a household aircon inverter drawing 7.64 amps running current with 2 head units on it drawing 5.7 amps, do you think I would be better going for 4@250w 24v panells thanks again mate for your help and willingness to share your knowledge regards Daryl

  9. Hobo Says:

    Hi Daryl,

    I did have a minor issue with a couple of LED lights that I made myself. I think the problem was one of design.

    The aircon currents you are quoting are at 240v – when brought down to 24v you have to multiply this current rating by 10 (or 20 if you decide to go with 12v). It is simply not possible to run aircon from a solar/battery bank. Take a look at my latest article (that you inspired me to write) http://hobohome.com/news/?p=557 – this should give you a good idea of why 24v is the way to go with a system the size of what you are planning. It also shows the maths to work out how much current the aircon system would use if connected to the inverter.

    To use 24v you either need to install panels in pairs OR use 24v panels (which tend to be a little cheaper than 12v ones).

    G

  10. Daryl stone Says:

    Thanks again Gavin I will definatly go 24v, and read the article , I dont want to be a copy cat however the moke set up is nothing short of brilliant so I started looking at mokes HOLY CRAP wish I bought 10 of them 25 yrs ago when I was in Darwin , thanks again man ill keep you in the loop and send some photos when there is something worth looking at cheers

  11. Pete Says:

    Good Day to you Gavin,
    Thanks for the enlightenment. I always knew electricity was like water (only it bites), but never understood the meanings or methods. Thanks for a great description
    Pete

  12. don Says:

    Nice article, working through your site, need to get a handle on inverters and voltage converters

    cheers don

  13. richard Says:

    Hi Gavin
    You need a paypal account so people can pay you for a hour per dollar consultation
    Seriously….I’d pay for an hour (more than likely more tham once) on the phone to you to help with issues
    you obviously know a lot about more than electrics when it comes to caravaning.I’m 35 and would love to learn from the horses mouth (so to speak)
    If I put a 240 volt lcd (standard shop stuff)in my (soon to be bought older van) how can i work it when away from power or can i buy a special or power adapter to make this work, plus fridge /light /ac plus many more questions.
    searching the net gives so many answers and most are rubbish. love the site even though I just found it.
    Set up your paypal mate i don’t think anyone on this site would mind paying for your expert advise
    regards
    Richard

  14. Hobo Says:

    Hi Richard,
    Thanks for the comments. I do undertake private consultancy contracts for people altering or building motorhomes and caravans. It always works out more cost effective to get it right the first time and to have an independent person view plans and diagrams BEFORE they implemented.
    Feel free to email me if I can be of any help.

    Cheers
    Gavin

  15. Mark Says:

    Hi Gavin,

    First off, we have just purchased our first caravan (actually our new home). a 23′ Jayco with a 200w panel & heavy duty 110Ah marine battery.

    3 way 180 L seperate fridge freezer, 900 w micro wave, an aray of 12v lighting, smallish 240 v LCD TV, a couple of laptops & mobile phones.

    For a week now I have been scouring the internet to get some understanding on how the battery & solar panels equate.

    We are planning to head west, in the near future, & what to make the most of the solar power sytem.

    Thank you for the 2 tutorials, as this has helped.

    Look forward to reading your other blogs to gain a futher insite as how to best utalise & improve the quality of our travels. Any further advise would be appriciated

    cheers

    Mark

  16. Barbara Cooper Says:

    Just found your articles — very interesting. I remember from school a long time ago I didn’t understand electricity and my mind is still a fog. We have solar panels on our caravan roof which were set up by Jayco through a regulator and 2 12v gel batteries. My husband connected a line from the batteries to the outside of the caravan with an anderson plug which we can connect to our aux battery in our landcruiser to top it up during the day. we run engel fridges in the wagon. We have now purchased portable panels of 120watts to connect to the aux battery with alligator clips. If we connect an anderson plug to the portable panels and plug it into the caravan will it assist the caravan batteries to charge and do we connect it via the regulator on the panels or bypassing it.

  17. Hobo Says:

    Hi there,
    Either method will work ok.
    Connecting a second set of regulated panels to the caravan is ok – but not the best solution. Depending on the type of regulator fitted to each set of panels, they may conflict with one another and cause one regulator to prematurely enter the ‘float’ state.
    Assuming you have the capacity on the caravan regulator – The best option would be to bypass the inbuilt regulator on the portable panels and connect them via the caravan regulator.
    This could be done by having two connections on the portable panels – one that is regulated (for use in the vehicle) and the other that is unregulated for connecting to the caravan regulator (of course you would only use one connection at a time).

    I hope this helps.

  18. Michael Says:

    I have a Danfos 12 volt compressor fridge rated at 70 watts or 5.8 amps. What size solar installation would I need on my van to cover this plus 6 5 watt down lights and a water pump?

    Great articles.

  19. Hobo Says:

    Unfortunately this is not enough information to make any kind of sensible estimate.
    Need to know:
    * What size is the fridge?
    * Is it a fridge Freezer or just a fridge?
    * Is the fridge upright or a chest type?
    * How many hours per day do you estimate the down lights will be used?

    Happy to provide advise – just need more info.

  20. Eriksom Says:

    Thanks, your efforts are very helpful. I just started to build my motorhome (see in http://www.4x4brasil.com.br/forum/frota-4×4-brasil/112829-casa-4×4-ou-como-dizem-motorhome-4×4.html ,sorry, all is in portuguese), and I hope to meet you along the world in some years. Now, I’ll go to read all other articles from your page, because I hope to get my motorhome ok at the end of 2013. If you come o Brazil, call us.

  21. Hobo Says:

    Thanks. We visited Brazil about three years ago – absolutely stunning place, we loved it. Hope to make it back some day.

    Cheers

    Hobo

  22. Doug Watson Says:

    Excellent articles. Thankyou

  23. Peter Hartley Says:

    Hi Guys
    WE are only 2 months into setting up our van for free camping when I stumbled across your site. I will read every word on your site given the time but let me thank you for explaining electrics in terms that make sense .I have written down all the formulas and will re-read these over and over again until they are lodged in my head. Finally at 54yo I have a basic understanding of electrics.

    Kind Regards Peter

  24. Hobo Says:

    Hi Peter,
    Glad you find the site useful.
    Feel free to ask any questions, I’m very happy to help.

    Gavin

  25. Mike Says:

    Hi Hobo,

    I found this very informative. Great effort & thanks.

    Mike, Adelaide Oz

  26. Peter Says:

    Hi Hobo

    A very good friend put me on to your site as we are contemplating the “three way” fridge purchase versus the 12 volt with solar panels.
    Thank you for spending the time to explain everything in a way that can be understood.

    I will no doubt be using your site again for further reference.

    Cheers Peter WA

  27. barry Wilson Says:

    hi Hobo
    Just to let you know of a new way of escaping the high prices of DC refrigeration I have just installed a new Samsung 320 Ltre 240 volt Digital Compressor Fridge Freezer in our motorhome.
    It is still to early to give you a full report on it but so far it looks very promising .I’m running it with a 750 W pure Sine Inverter and it would run easy on a even smaller one .Cost of the Fridge with 10 year compressor cover was only $675.00 and very low power draw. When compared to the price of 12/24 Dc Fridges it is a real bargain.
    I have Plenty of Solar and storage so its ok for me to go this way but I’m thinking this may be the best way for most large Rigs. I will keep you informed how it goes once back on the road
    Doc

  28. Luke Says:

    Thanks so much for your generosity in sharing your learning and experience. I am an electrician and though I have heard similar analogies you win by a country mile in articulating things to facilitate understanding. So glad I stumbled across your site.

  29. Leon Says:

    Hi,
    Thank you for all your very helpful and easily understood information.
    Kind regards
    Leon

  30. Leon Says:

    Hi, I have some questions regarding 12v vs 24v systems. I noted your rules about motor-home electrics, i.e. always keep the systems similar. I also prefer the benefits of 24v (cables sizes etc)

    I was wondering, My Fiat van has a 12v system with too much electronics to even consider changing. It’s got a 140 amp alternator. What is the implications of using a dual battery system and either a seperate 12v solar charger or a 12v to 24 v converter to charge the 24 v batteries in combination with a solar system? I would like to harness excess alternator energy when travelling on the open road.

    So far I’ve got 4 6v 250 amp carbon deep cycle rex batteries. I plan to get 4 x 327 watt BenQ solar panels and use a Giant 2400w charger/inverter combination. The system I am planning is comparable to a friend’s bus system, but he has a 24v alternator.

    Just BTW I go from Melbourne to Sydney on 64 litre diesel when travelling at between 80/90 km/h.
    Thank you
    Leon

  31. Hobo Says:

    Hi Leon,
    It would not really be a good idea to install a 24v house system in a 12v vehicle. It would be more costly, and could be dangerous (if for example you accidentally got 24v on the 12v vehicle system – now that would be costly!).
    With regards to using the alternator – there is no access energy. The alternator only produces the energy that is required – if it is required to produce more, it will put more load on the engine and the fuel economy will go down. However, that is not a reason to avoid using the alternator. I always like to arrive at a camp spot will full batteries, so I make use of the vehicle alternator most of the time (Our bus has controls to allow me to manually control the amount of alternator current used to charge the house batteries).

    The best plan for an inverter/charger is to install the smallest inverter you can. The issue with installing an unnecessarily large inverter is that they are very inefficient when running at low load. For example a 1000w inverter supplying a load of 950w could be around 95% efficient (so draw 83amps @12v). A 2400w inverter supplying the same 950w load is likely to be around 70% efficient and thus draw 113amps to do so.
    As a rule of thumb, the closer an inverter is to its full load capacity, the higher its efficiency. You will see efficiency for inverters specified as “up to 95%” or “peek efficiency of 95%” – this is because at lower loads their efficiency is fairly unimpressive.

  32. Leon Says:

    Hi Hobo,
    Much appreciated for the information. So I’d appreciate your comments when you have time on 3 matters.
    1. A have a brand new dual battery system (which came from my Landcruser which died). So how do you suggest I wire this?
    2. I would like to run an induction cooker which uses max 2000 watts. Which size inverter (Pure sign wave) would you suggest?
    3. Size of cable from the dual battery system to the batteries?
    Thank you
    Leon

  33. Hobo Says:

    Hi Leon,

    Not sure what you are asking in #1

    #2 – if there will be no other loads on the inverter, as 2500w inverter should do the trick. Make sure it is “Continuous Rated” at 2500w (NOT just surge).
    #3 – Depends on the length of the cable and the current to be carried.

  34. Leon Says:

    Hi Hobo,
    I may have to give you some background on 1 and 3.
    Re 1 I was considering your reply to have a manual switch, or should I simply just use the abilities of the dual battery system?
    With regards to 3;
    As I mentioned my vehicle is 12V. I do have some understanding of the benefits of 24v, i.e. smaller cables and less loss upon conversion to 240v and transmitting 24v. If I do use 24v, I’ll not earth any of the 24v systems, but run separate negative cables. This way I planned to overcome the issues with earthing two different voltages.
    In my setup the auxiliary batteries (weighing up to 240 kg) should be best fitted over the rear axle. However the distance will be around 4 metres (maybe longer say 5 m) from the alternator. If I could charge this as the 12v cabling will be huge, not to mention costly.
    The only alternative option is to position the batteries behind the driver, a distance of around one metre, but this will mean putting lots of weight on one side of the vehicle and impacting the design somewhat. (So I would appreciate it if you can give me your recommendation of cable size for the two options)
    Thanks again

  35. Leon Says:

    Cable sizes I am acquiring about is for 12V, say 4 to 5 metres vs around 1 metre for the current coming from the dual battery system via the alternator. Which is the appropriate fuse (amps) size to use with this?

    My apologies, I am a bit all over the show. Sorry 🙁

  36. Hobo Says:

    Hi Leon,

    I would strongly advise against using a 24v house system in a 12v vehicle. The chances of something going wrong are quite high and the results would be catastrophic! It is very hard to keep negatives away from the ground – some appliances even connect the negative to the chassis of the device (a Waeco fridge that I had a few years back did this). I’ll talk about cables sizes in your other post.

  37. Hobo Says:

    Hi Leon,

    To work out cable sizes we need to know a few things…
    1) The length of the cable (which you have included here).
    2) The current that the cable will carry (so what size is your alternator)?
    3) The maximum voltage drop permitted (for this 2% is a good rule).

    Regarding the fuse, I would suggest a self-resetting circuit breaker of a value around 60% of the rating of the alternator if the alternator is not hot rated. This can be increased to 100% of the rating of the alternator IF the alternator is hot rated.
    A hot rated alternator is designed to deliver its full rating all of the time. Most alternators are NOT. They are designed to replace the current used in starting the vehicle (so say 50 amps for about 10 minutes) then slowly reduce the output to meet the requirements of the (normally small) load of the vehicles systems. Running an alternator that is not hot rated at near full load for an extended time will result in the magic smoke being released. The self resetting MCB will prevent a large current being drawn from the crank battery when the house battery is relatively discharged (first thing in the morning for example) AND prevent overloading a the alternator.

  38. Karl Says:

    We recently purchased a Mercedes-Benz Sprinter cargo van which, I believe, runs off 12v (although I have to check). If this is the case, as with Leon above, would you recommend just staying with 12v, or is there an easy way to convert the entire vehicle to 24v without spending an absolute fortune and spending weeks doing it?

    I was planning to have 2x 200W (+maybe also a 1x 100W) 12v panels, plus the alternator (unknown amperage, I think 120A but will have to check) via VSR, connected to 2x 240Ah house batteries. We will be living in the van full time “off the grid” and powering a few devices such as 12v fridge, LED lights, water pump, 1500W inverter (only used on rare occasions), 12v USB outlets to charge phones, and a DC-DC charger for our notebook computer.

    Cable length from the panels on the roof to the battery bank inside will be around 3.5m maximum, so thickness shouldn’t be too much of an issue. The inverter and fridge will be on the opposite wall of the van, so will need cables around 4m of cables to run neatly across under the bedframe to each device.

    All the other devices, LED lights, fan vent and USB outlets, are low draw, so they shouldn’t need super thick cable even though they’ll need to run a bit longer (5-6m) to neatly connect to everything.

    Do you see any issues with how this setup works? Thanks

  39. Hobo Says:

    Hi,
    With a vehicle the size of a Sprinter 12v is fine and it would be neither a good plan nor economical to change the voltage.
    For a van this size the general rule for sizing the solar is “as much as you can squeeze onto the roof!”. Solar is very cheap these days and there is just no good reason to put less on the roof.
    Look at the Victron blue solar series solar controllers – with Bluetooth now built in, they are a great option – they also support series connected panels – this vastly decreases the cable size requirements.
    At 1500w the inverter is perhaps too large for the setup – but if you don’t use it often it will be fine. I would strongly recommend adding a good quality battery monitor (Victron BM702 or the like).
    Looks good!

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