Recommendations (size & controller) (1 Viewer)

[barracudabus]

Happy Easter everyone,

Just sitting here in the van slowly using my battery off grid and have decided it's time for some solar power. We've got a 4kw system at home so we're already sold on the benefits but we're just looking for some recommendations on the size of system people think we would need.

- We're currently 2 adults + a 2 year old with another on the way
- Swift 590rs currently 1 leisure battery 110ah
- nearly fully LED but assume they'll all be converted soon
- I like my sport and f1 so the TV can be on in the background for long periods
- we've never used the 12v on the fridge but may do if it's practical and we have spare power
- trips away are unlikely to be more than a fortnight as the garden (veggies) would complain
- misses is a teacher so probably lots of 5 day / 1 week trips
- were happy off grid as we've got refillable gas system for cooking, heating etc
- I am looking at getting a DC step-up regulator for the laptop so may spend week days working from the van at country parks during the summer

Sorry I know that's a lot of info but wanted to avoid the "how long is a piece of string" responses

Also if anyone has any pointers or recommendations for systems or controllers we'd appreciate the head start.

And if people think that the single 110ah battery could be an issue feel free to speak up.

TIA

 

[suavecarve]

Pointers,
2nd battery is unbelievably worth your while getting. Get the same size if possible.
Get a 12 volt tv
Dont bother putting your fridge onto 12 volt and run it off gas all the time,

Solar panel size has to depend on where you are in the world and what the weather is like. Some people have 6 batteries some people have 80 watt panels.

Personally i have 100 watt solar panel, 2 x 110 batteries, 12 volt tv, away most of the time between april and october in south of france. Dont really watch tv and only charge phones cameras etc. No chance whatsoever of running out of battery.

Hope that helps

 

[suavecarve]

we also own 2 sets of 4kw on the houses. The benefits for motorhomes are not financial so much as convenience. Though we do like the financial benefits as we got in when it was 45 p a kilowatt. We liked the government that day. !!!
also got solar for water heating.

^{_{Subscribers  do not see these advertisements}}

 

[barracudabus]

We're UK east Midlands so weather OK, but clearly not south of France good

 

[suavecarve]

To give you some idea, south of france, summer, empty batteries full by 0800.
East midlands, april, empty batteries, nobody knows how long.
Just on that basis i would up your solar towards 200

 

[DBK]

You won't meet your needs with solar alone if you go off grid in the UK in winter. So it just comes down to compromise, more panels and at least another battery will help but if you want to use the rig in winter or just UK bad weather you might want to consider a B2B charger.

^{_{Subscribers  do not see these advertisements}}

 

[Urs4_2008]

To be sure of what you need, you would be better off first getting a battery monitor to measure normal usage / worst case usage.

But I can tell you what my experience is. We’re a family of four. One kid 7 another 11. We have a led tv which we almost never use, but it’s very efficient when we use it (about 12-20 watts). We use Webasto airtop for heating and running hot water and cooking on lpg.

We do charge ipads, phones etc every night. Normal usage with a bit of tv every day, all led lights a summer day is about 30 ah. A winter day not too cold would add about 24-30 ah more, total of about 60 ah.

Next, you have to decide how many days of no charging you want to be able to have power. Let’s assume you need 40 ah a summer day since you like to have the tv on in the background you would need, assuming 8 hours of sun, and solar panels angeled, a 100w panel, which simplified will yield 5 amps for a total of 8 hours = 40 ah. If you cannot tilt the panels double the wattage: 200 watts.

Assuming you want to make through a bad weather day, you need to replace 80 ah after 2 days of no charge. Given flat mounted panels you would need 400 watts.

Three days of bad charging you need to replace 120 ah, meaning 600 watts worth of panels.

Another thing is your battery. You should not go below 50% state of charge, meaning you currently can use 55 ah, meaning you can make it through one day before you need to charge. If you get another battery, you can make it through almost 3 days if you double your capacity.

A good tip; when getting new batteri, get two. The old one will bring down the new one.

All this are assumptions but you can take it from here

 

[barracudabus]

You won't meet your needs with solar alone if you go off grid in the UK in winter. So it just comes down to compromise, more panels and at least another battery will help but if you want to use the rig in winter or just UK bad weather you might want to consider a B2B charger.

Unlikely we'll use in winter for anything more than an overnight.

 

[barracudabus]

Thanks @Urs4_2008

The battery was new last summer so should be OK if I get a similar battery soon.

I think a new battery will be the first addition

^{_{Subscribers  do not see these advertisements}}

 

[Urs4_2008]

Thanks @Urs4_2008

The battery was new last summer so should be OK if I get a similar battery soon.

I think a new battery will be the first addition

My pleasure

Forgot to add: I have 800 watts of solar. And I’ve just returned from easter vacation in the Norwegian mountains. Minus 22c at night. Started with 100% battery at 6 pm. Used about 20% of 200 ah during the night (40 ah), which the 800w solar flat mounted replaced by noon, because of sunny weather.

 

[SandraL]

There are 2 types of solar contoller. PWM and MPPT.
The mppt is better in low light conditions, just when you need the power.
Think of cheap and much better, cheap and dear.
I would suggest a solar controller capable of dealing with 250 watts and installing a 125watt panel, leaving option to get 2nd panel later if required.
We have votronic duo 250 conntroller (mppt) which also trickle charges starter batt and 250 watts of solar panel and find this enough.
Initially we had 125 watt panel which was fine in summer, but in autumn we struggled so added another 125 panel.
A second leisure battery would also be ideal if he sun doesnt come out to play.

 

[Lenny HB]

I would have thought for your requirments 300 - 400 watts of solar and 300 a/h of batteries would give you enough power for 3 season use. A good quality MPPT solar regulator like the Victron or Votronic will make a considerable differance to solar output in conditions other than bright sunlight. If you have an modern AES fridge with a S+ terminal the Votronic regulator can switch the fridge to 12v when there is enough solar avalible.

^{_{Subscribers  do not see these advertisements}}

 

[Urs4_2008]

I have a lot of experience using Victron with their Bluetooth option, and app support. Go for the biggest Victron you can afford (as big as you have space for panels on the roof)

The Victron models are named ie 100/30. First number is maximum input voltage and second is maximum charge amperes.

In my motorhome I use the 150/70 model. Quite big but very good

 

[tacr2man]

You might find following sites useful :
http://www.bimblesolar.com/offgrid/12v/260W-budget-kit-mppt-mounting-used
https://www.batterystuff.com/kb/tools/calculator-for-load-specific-run-time.html
@barracudabus

 

[Urs4_2008]

Thanks @Urs4_2008

The battery was new last summer so should be OK if I get a similar battery soon.

I think a new battery will be the first addition

Recommendation anyway is change both. It’s mostly not age but usage which is important when connection a new battery to an older one. Has the older battery seen 50% or less SoC many times? Ever been about empty? You can try to too charge both old and new battery, let them sit with no connection for 24 hours and measure the idle voltage. If it’s near the same, it could work. But that test doesn’t tell the whole story.

Maybe after a steady, low draw for a few hours the older battery drops a lot quicker than the new one, taking the newer down with it. You will get about the combined total of the worst battery

I’ve done this myself once, and I believe the newer battery got the life expectancy of the old battery, failing sooner than it should have.

^{_{Subscribers  do not see these advertisements}}

 

[Urs4_2008]

From a previous thread, a bit more detailed explanation:

Simplified info regarding solar systems on RV:

1) How much power do you consume pr day?
2) How many days of bad charging conditions will you need?
3) Can you mount the panels at an angle towards the sun?
4) Spend the extra money to get a quality MPPT charger. More efficient.
5) If you spent the money for a quality MPPT charger, connect the solar panels in series to up the voltage in the drop cable and thereby reduce the cable loss / inefficiency.
6) If you get a PWM controller (cheaper) all panels must be connected in parallel, will require thicker cables from panels down to charger, and a bitt less efficiency in the solution.

More panels / capacity is better as you will get more charging in less than optimal conditions as long as you have the means to buy them.

1) Your actual power consumption:
A good battery monitor (ie. Bogart Engineering Trimetric TM2030-RV http://www.bogartengineering.com/products/trimetrics.html or the Victron BM700, 702 or 712) mounted in advance will give you statistical usage history, which will help you to determine optimal solar setup based on your actual needs.

Ie. the battery monitor might show that your regular usage when boondocking is 25 amp hours pr day. If you're running lead acid of some sort, they should not be run down below about 50%. If you want to be able to be boondocking for 3 days with bad weather (no sun) in a row, you will need 25x3=75 amp hour battery. But since you're aiming for not running it below 50%, you will need 75ah x 2 = 150 ah battery capacity. Most RVs has space for about 2 x 95ah batteries. In my experience even cheap batteries work just fine, as long as you have a good charging solution and keep them topped up at "all times".

2) How many days of bad charging do you need?
When it comes to recharging this used capacity, lets assume the 4. day is a sunny day, you will need to recharge the used 25ah x 3 plus the usage the 4. sunny day, meaning 100 ah that will need to be replaced on the 4th day. Assuming summer time (8 hours of charging), great conditions, angled panels - you will need to replace (charge) 100ah / 8 hours = 12,5 ah pr. hour. Maximum output for a 100 watt panels is about 5 amps. This means that 3 100watt panels will yield 15 amps pr hour of sun, which is a bit more than the 12,5 you need. When running lead acid you will always need to put more ah into the batteries than you take out, so this is quite optimal.

3) Can you mount the panels at an angle?
But most of us isn't able to angle the panels, meaning that you will need about 40-50% more panels to get the same production when mounted on a flat roof. Worst case; 300w x 150% = 450 watts. Rounded up will be 5 100 watts panels. 5 panels in series will generate in excess of 110 volts, which will demand a charge controller which supports this high voltage. (Be careful when handling this or get some help). An option to reduce voltage a bit is to go for 6 100 watts panels, running 3 in series paralleled with another 3 in series. This will generate a voltage of ~70, which many MPPT controllers will handle. But to do this, you will need an even number of panels (2, 4, 6, 8 etc). 600 watts of charging (if angled etc) can generate as much as 50 amps+ charging current if the batteries are depleted. So a Victron 100/50 would be a great option in this scenario. Charge current will be limited to 50 amps. Remember to put charger very close to the batteries

4) PWM / MPPT charge controller
PWMs are cheaper, but need similar voltage from the panels to the batteries meaning parallel panels. MPPT a bit more efficient, and often supports much higher input voltages meaning support for serial connected panels. Bogart engineering has an excellent PWM controller, and Victrons are great for MPPT.

5) 6) parallel/ serially connected panels
Panels should be identical. If you have a controller supporting high voltages then connect the panels in series to up the voltage and reduce cable heating and efficiency loss. Keep cable runs as short as possible. If the panels are equal voltage but different capacity then parallel is required. If the voltage is different but capacity is equal, then series connection is recommended. But save the trouble and get identical panels

Either this, or reduce usage, or accept another way of charging if you will need more days without sun or lesser sun charging capacity.

 

[Richard n Ann]

Happy Easter everyone,

Just sitting here in the van slowly using my battery off grid and have decided it's time for some solar power. We've got a 4kw system at home so we're already sold on the benefits but we're just looking for some recommendations on the size of system people think we would need.

- We're currently 2 adults + a 2 year old with another on the way
- Swift 590rs currently 1 leisure battery 110ah
- nearly fully LED but assume they'll all be converted soon
- I like my sport and f1 so the TV can be on in the background for long periods
- we've never used the 12v on the fridge but may do if it's practical and we have spare power
- trips away are unlikely to be more than a fortnight as the garden (veggies) would complain
- misses is a teacher so probably lots of 5 day / 1 week trips
- were happy off grid as we've got refillable gas system for cooking, heating etc
- I am looking at getting a DC step-up regulator for the laptop so may spend week days working from the van at country parks during the summer

Sorry I know that's a lot of info but wanted to avoid the "how long is a piece of string" responses

Also if anyone has any pointers or recommendations for systems or controllers we'd appreciate the head start.

And if people think that the single 110ah battery could be an issue feel free to speak up.

TIA

I would leave the battery for now, if it's not getting too discharged over night as it is, it's not a problem. Judging by what you have said you'll be using, I would fit 200w of solar with an mppt Votronic duo controller.
We've got 150w and it's plenty big enough for charging phones, led lighting and TV in the evening. By midday (in summer) the battery is 100% again

 

[Minxy]

Your TV use will be the defining factor I suspect ... a TV can draw a lot of power if left on for a long time, even a lower powered one, so see what it draws and double it, that's the minimum you'll need.

^{_{Subscribers  do not see these advertisements}}

 

[Urs4_2008]

Your TV use will be the defining factor I suspect ... a TV can draw a lot of power if left on for a long time, even a lower powered one, so see what it draws and double it, that's the minimum you'll need.

It will be a big factor. Event one of the best led 12v tv will use about 19 watts (24 inch) Amazon product ASIN B00OQ3E6F2
8 hour usage will need about 13 ah.