help woth solar set up (1 Viewer)

[bobby]

hi people new motorhomer here.
my motorhome has a 85ah battery under the bonnet to power lights and pump inside. i have purchased a 185w 20a solar panel. i was hoping to get a set up with seperate set up to the existing already there so its less messing. i have purchased 2 x 12v 130ah leisure batteries a 4000w inverter 24v. i have had a scan around the forum but cant quite understand the set up i need to do.

the one im thinking is to lign the 2 x 12v batteries in series + to - and use the + and - left on each to power the inverter. then connect the solar panel same to either end of each battery. all the set up im after is to have it to power appliances such as tv/sky box microwave and maybe portable oven and charging phones ect obviously not all at same time.

can any one see any obvious things ive missed. i wouldn't mind also having a set up to alternator to do a charge whist the solar weather isnt up to it haha

thanks in advance

 

[MC 55 FUN]

Surely if you connect the batteries in series giving an output of 24v your 12v habitation appliances are going to go pop ?

 

[bobby]

Surely if you connect the batteries in series giving an output of 24v your 12v habitation appliances are going to go pop ?

the existing set up with the 12v 85ah battery has fridge lights pump all running off that so the seperate set up i am wanting to do is to run all other appliances from the new 4000w 24v inverter. so i could run tv ect from that without having to hook up.

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[Boringfrog]

So you are only using the batteries to power the inverter nothing else? Why did you go for a 24volt option?
Oh and welcome.

 

[bobby]

not quite sure just thought more volts the better maybe last longer?

 

[bobby]

yes just the inverter

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[Boringfrog]

Inverters are not very efficient, a 12 volt TV would be a better option. What other "devices" are you powering from the inverter?

 

[bobby]

Inverters are not very efficient, a 12 volt TV would be a better option. What other "devices" are you powering from the inverter?

i could still go for that though couldnt i? 12v tv/ low volt kettle/toaster/microwave. i assumed i would be able to stay off the grid a lot longer with that set up being solar powered and voltage 24v

 

[bobby]

i could possibly just do away with the 85ah battery swap for 130ah one and just do a 12v set up from the inverter. think the inverter should do a 12v set up to it too if not i cpuld send it back. it did cost 220 and its brandnew

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[DBK]

My instinct is to ask - can you get your money back on the 24 volt inverter?
It is possible of course to set the two batteries for 24 volts and some solar chargers will work at 24volts too. The problem is getting the 12 volts for everything else, which again can be done though it would need dual circuits splitting the load. The stumbling block would be how to charge them on the move or on EHU. I can't see a way around this but very happy to see how it might be done.
The simplest solution by far is to revert back to 12 volts with the batteries connected in parallel. Junk the inverter.

 

[MC 55 FUN]

the existing set up with the 12v 85ah battery has fridge lights pump all running off that so the seperate set up i am wanting to do is to run all other appliances from the new 4000w 24v inverter. so i could run tv ect from that without having to hook up.

Thing is that you're at risk of depleting your starter / vehicle battery & not being able to start the Moho.

 

[Boringfrog]

Here's my setup: 200 watts solar, 3 x 100ah batteries, 1400w inverter, gas for heating and cooking. Never need to be on EHU apart from Winter with little sun. Running 24 volts has no advantage I can see.

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[Camping Gaza]

your 12v and 24 circuits will not mix. don't even go there.

you will have to have your 24v inverter circuit totally isolated from the 12v circuit, even the negative chassis earth.

You can't just connect a solar panel directly to a battery bank, you need a solar charge unit

your solar charging circuit can only charge your 24v circuit and your isolated 24v battery bank (not your 12v hab battery) unless you can find a split voltage one (unlikely)

your inverter can only power your 240v sockets but these sockets will need to be isolated and ONLY connected to your inverter (when you hook up your sockets need to be connected directly via a changeover relay because of your 12v battery charging)

Unless you are confident with basic electricity and understand some basic electronics I would change that 24v inverter to a 12v one and have your battery banks and circuits running at 12v

 

[MC 55 FUN]

not quite sure just thought more volts the better maybe last longer?

Amp / hour capacity is key & far more important than voltage for off ehu use.

 

[bobby]

My instinct is to ask - can you get your money back on the 24 volt inverter?
It is possible of course to set the two batteries for 24 volts and some solar chargers will work at 24volts too. The problem is getting the 12 volts for everything else, which again can be done though it would need dual circuits splitting the load. The stumbling block would be how to charge them on the move or on EHU. I can't see a way around this but very happy to see how it might be done.
The simplest solution by far is to revert back to 12 volts with the batteries connected in parallel. Junk the inverter.

yes i could send the 24v inverter back its still in the box and arrived today. only issue is wouldn't having a 2 12v batterys in parallel connecting to solar power wouldnt that charge the batteries in equal?

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[bobby]

your 12v and 24 circuits will not mix. don't even go there.

you will have to have your 24v inverter circuit totally isolated from the 12v circuit, even the negative chassis earth.

You can't just connect a solar panel directly to a battery bank, you need a solar charge unit

your solar charging circuit can only charge your 24v circuit and your isolated 24v battery bank (not your 12v hab battery) unless you can find a split voltage one (unlikely)

your inverter can only power your 240v sockets but these sockets will need to be isolated and ONLY connected to your inverter (when you hook up your sockets need to be connected directly via a changeover relay because of your 12v battery charging)

Unless you are confident with basic electricity and understand some basic electronics I would change that 24v inverter to a 12v one and have your battery banks and circuits running at 12v

the set up i would be happy with is having it seperate to the existing one. just to run sockets from the inverter. i have a small fuse breaker box that is connected to to an inverter already that runs the ehu i cpuld just switch over when i needed to ehu

 

[bobby]

the set up i would be happy with is having it seperate to the existing one. just to run sockets from the inverter. i have a small fuse breaker box that is connected to to an inverter already that runs the ehu i cpuld just switch over when i needed to ehu

what would be the advantage of the 12v set up to the 24v set up? i hoped having a seperate off the grid set up with 24v 130ah would run everything i needed instead of 1 12v battery. suppose the other option would be to swap the inverter and get 12v inverter and have it running pararell so i would have 260ah

 

[DBK]

I think you need to look at typical MH electrical setups.
It is quite easy to setup two batteries in parallel so they share the load, you will find diagrams on line how to do it if someone doesn't post a link here. But as already mentioned, you need to use a solar charger such as the Victron 75/15. I'm sure you intended to but just in case there is any doubt connecting the panel directly to the batteries will fry them.

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[bobby]

sorry forgot to mention it does come with solar charge unit. i want to get this set up seperate to the existing as i do know it needs a full rewire at some point but want to get out on that open road and enjoy as much as i can this year. next year i will strip it back amd rewire everything.

 

[autorouter]

You came to this forum for advice, and here's mine.

Return the 24V inverter and get a 12V version.

I'm assuming here that your motorhome is not one of those huge rigs based on an HGV, that is running on 24V anyway. If so, a 24V inverter is exactly what you want.

You will have all kinds of unnecessary problems in the future if you try to mix 24V and 12V systems. In terms of power, the input and output of a 12V and 24V inverter are identical.

Most motorhomers stick to 12V, and connect one, two or more batteries in parallel to get more storage capacity.

The only upside of a 24V inverter is thinner cable to connect batteries to the inverter.
Possible problems? Your engine alternator will be 12V. If you want to charge the batteries from the engine alternator, your batteries will be wired up in series as 24V.
If you want to charge the batteries from a mains charger, you will need a separate 24V mains charger.

All your habitation items will be 12V. Your leisure battery will therefore need to be 12V. If you want to charge your leisure batteries from the solar panels, you'll have problems if it's also charging 24V batteries.

If you were powering a totally isolated place, like a beach hut or an allotment shed, then it's true that it makes little difference whether it's 12V or 24V. But as soon as you have a vehicle involved, you need to align the voltage with the vehicle voltage to head off any avoidable problems in the future.

Also while you still have a choice, it seems to me that a 4000W inverter is maybe a bit over-optimistic for a pair of batteries. Unless you have a definite requirement for this power, I'd think about a smaller one, 3000 or even 2000 watts, even if you have to be careful what appliances you switch on at the same time.

 

[bobby]

cheers i will send the inverter back. the solar panel i purchased the guy said it could either charge 12v or 24v batteries in series. i will look at getting a 3000w inverter if you think that is better option to what i would be powering in the motorhome. would a wind turbine power off the 12v set up as that maybe a plan for future.
thanks for your replies

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[bobby]

also the set up im after at the minute is this being totally seperate from the habitat that is there. so the inverter would only be used to power the sockets for tv toaster ect and be solar powered. i would buy a charger to top batteries up in low solar weather and revert from using alternator to charge

 

[JJ]

You must do it the way you want to but...

I agree with Mr Autorouter.

Keep everything 12 volts.

I use a dual solar charger... it charges the leisure batteries AND the engine battery. You set how much charge you want to go to each battery.

My (small) inverter is hardwired to the leisure batteries. Only use it for a food mixer and charging a couple of (older) devices.

I make toast by gas.

I charge all other devices from 12 volts.

I wouldn't dream of getting a 3000 watt inverter ever. Loads of bother for what? Making toast and hair drying? (I live on my own and "wear" my hair very short.)

Mind you... I haven't been doing this motorhoming lark all that long...

I didn't start until I was 20.

JJ

 

[hilldweller]

What are your expectations off your 4000W inverter ?

You are buying 2 x 135Ah batteries - OK.

4000 / 12 = 350 AMPS. You have 270Ah of which you can use only 135Ah.
135/350 = 23 minutes but batteries don't work like that, you would get 15mins.

Now do you see the problem. You just can't equate 3000W in a van to 3000W in your house, it all goes pear shaped when you do.

You want heat, burn gas, it's so much more efficient to store heat in gas form.

The batteries store the same energy in 12 or 24v configuration, stick to the norm of 12V.

We have a 300W inverter and it used very little, everything is run off 12V. Only the ebike batteries need 240V and then only 100W or so.

It's a steep learning curve but with your new found friends you'll get there.

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[bobby]

i need to understand the ah and volts better being a multi joiner with 18v lion 3ah 4ah 5ah 6ah bats you would think id just get it but not quite sure. i think the 12v option is what i will aim for. just the guy who sold me solar panel said it could be connected to 12v or 24v in series. as long as i can set up the 12v batterys 130ah in parallel and still have them charging decent via solar think im on to a winner. failing that il swap my 85ah bat under bonnet with the 130ah and just have the solar and inverter on a 12v set up. it does need a new rewire definitely to be perfect set up as stàted in other posts but will be at a later date.

so im going to send 24v 4000w inverter back

if im going for the 12v option.
and wanting to power.
microwave
tv
sky box
phone charge
maybe small oven
and small devices which inverter should i be buying.
we have gas heating so wouldnt really need blow heater but do have one.

its great this forum for motorhoming and is perfect for finding put anything and opinions
thanks again

 

[hilldweller]

microwave
maybe small oven

There are your battery killers. Microwave crops up regularly, people do use low powered ones off battery. For the inverter usually you aim for twice the wattage of the microwave for start up surge, so in the region of 850W and double it giving a 2000W microwave.

I don't know what "small oven" is in terms of watts, but "oven" usually means a long time so very dodgy.

No way could you run a fan heater off batteries.

 

[DBK]

I think you really need to rethink your approach. A 185W solar panel isn't going to produce enough energy to recharge your batteries after any serious use of a microwave oven and certainly not even a small electrical oven. For everything else an inverter around 500W would probably be enough but the price of inverters has come down a lot now and you can get a 1500W pure sine wave inverter for around £150 now which might be worth going for so you are fairly future proof.

However, I suggest you incorporate the 12 volt batteries into the vehicle charging system using a thing called a split charge relay which will charge them when the engine is running but disconnect them from the vehicle battery when the engine is stopped so the vehicle battery isn't drained. The solar panel output can just be connected to the leisure batteries directly. The controller will sort out what to do itself. With this setup you stand a chance of arriving at your destination with the leisure batteries fully charged and if the sun is hiding you can always run the engine statically to give them a boost. This is also the only way you would be able to run a microwave or any other high load device when it is cloudy.

I did a thread about fitting an inverter here: https://www.motorhomefun.co.uk/forum/threads/fitting-a-1500w-inverter.156023/
The link at the beginning takes you to another thread where there was a bit of discussion about different models which might also be useful. The one I fitted is showing unavailable now but there lots of similar ones - very similar in fact - I think they are all probably more or less identical under the case.

Edit: This is the one I fitted but I paid less I seem to recall. Worth shopping around.

Amazon product ASIN B01M7U05U4

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[Wissel]

A microwave will probably kill 2 leisure batteries quite quickly (far too much power draw at once). Plus the wiring it would need could be a real issue.

I have 4 x leisure battery and a very sturdy set up with smart chargers, solar etc - no way I'd try running a microwave of them.

It can be done. Someone I know build a van, with a great electrical system in it, designed to power his microwave. Again, he had 4 x battery, plus huge cables and a lot of very pricey Victron trickery.

Edit - Thought it might be useful to give an idea what draw the things listed would put on a battery.

microwave - say 850w - so 850/12.5v = roughly 70Ah draw. So if a 140Ah "could" supply this amount of power it would theoretically be dead in an hour. In reality the battery would probably last half this time.
tv - Say the TV consumes 20w and its on for 5 hours a day. So 20 x 5 = 100w/12.5a = 8Ah
sky box - I'll guess same as TVish, so again, 5 hours per day = 8Ah
phone charge - I'll guess around 10w and only needed for about 2 hours ago. So 20w per day/12.5v = about 2 amps used

Electric oven or heater - stick with gas.

So TV, sky box and phone would probably only use around 20Ah per day (unless on for longer). With 2x 140Ah batteries you'll have roughly 140Ah that can be used (shouldn't drain a normal leisure battery past 50%), so this would probably last quite a few days (and solar charging will really help).

 

[peterc10]

There are plenty of very good 12V TVs out there. LED TVs use low voltages internally so it is daft to use an inverter for them. Same with phones nearly all of which use 5vdc USB chargers. Again buy a dedicated USB point for your 12v system or just use an adaptor which goes into your 12v power outlet.

 

[SuperMike]

also the set up im after at the minute is this being totally seperate from the habitat that is there. so the inverter would only be used to power the sockets for tv toaster ect and be solar powered. i would buy a charger to top batteries up in low solar weather and revert from using alternator to charge

Kettles, ovens, microwaves, toasters, anything that has a heating element and solar do not mix. Yes ok for a very short period, but even a 700w kettle will suck via the inverter a huge number of amps that the battery will only be able to supply for a short period and will take ages to put back with solar. You need to completely rethink this, for example the kettle on gas hob, if you have one.

We have 400w of solar and in the south of France on a super sunny day, I have seen 25A charge on the panel. Now, that will keep up with Managements medical requirements and will do, down to about a 10A charge, but after that I'm on a looser. And remember you will only get maximum charge for a couple of hours as the sun goes past its zenith, other than that it's going up or coming down.

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