Solar decisions





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  1. #1
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    Default Solar decisions

    SORRY GUYS: I had laid out beautiful tables and links in order to make this post easily readable. Spent ages trying to get it all sorted only to find out that the tables had been removed and now there is no way to make this much better. Comon admins surly this can be sorted. If you need help give me a call. Images of the tables are one way to skin a cat!

    The time has come to add solar to my over-landing experience ... and WOW is there a TON of information out there. I apologize if this is a horribly long post. I have included a spreadsheet of the table including some current prices if you are interested.

    Side note: I am of the opinion that if you are going to do something, do it right the first time. Even if I have to do it in stages from an affordability perspective.

    This is the homework I have done and I don't necessarily want a recap of the many many excellent posts out there. I just what direction as to what I am potentially missing, and man am I confusing myself. I have compared several panels found on the web and have come up with a table to try to help me make the decision on which panels to get. This link has also been VERY helpful with the calculations I think I needed.

    Here are my restrictions though:
    1. I will be adding this system to the top of my Bundutec RTT and there are a few limitations here that I am aware of (see the manual in the link provided):
      1. The roof can carry 25kg
      2. Length is 2100mm and I don't want the combined width of my panels to exceed that.
      3. Width is 1350mm and I don't want the length of my panels to exceed that.

    2. I use a C-tek D250SE charger that I want to plug the panels into. There are 2 limitations here that I am aware of:
      1. Input voltage on the D250SE is limited to 23v
      2. Max input current is 25A

    3. My auxiliary battery will be a Blue Nove LiFePO4 108Ah (I am not sure if I should get the one with Bluetooth management included. the link is to the battery without the Bluetooth.)
    4. Later I want to add another LiFePO4 battery (like the one in point 3) but in a portable box that I can add to my system for over-landing (I.e. 1x battery per fridge) but also have the ability to move it to SWAMBO's Disco for when we shoot somewhere and I want cold drinks on the way.
    5. Multiple panels will be wired in parallel so I can maximize the amps while keeping the Voc low (under 23v)


    Here is the table that is helping me make up my mind about which panels I think I need:

    Click image for larger version. 

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    Is this understanding correct?
    So for running the 50l fridge and all the other accessories listed below, I think the calculation will look as follows:

    Total Expected Usage:
    Click image for larger version. 

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    Total Watts Needed over 24 hrs (excluding the 40l fridge) -
    1905.6 W

    To work out the amperage needed I divided 1905.6W / 12v and came to 158.8A

    Battery:

    108Ah Battery @ 80% = 86.4A
    convert to Watt-hours = 1036.8

    Huh? I thought I had a little understanding of what I needed but now I am all confused again.


    1. How will I ever be able to keep up with that load requirement?
    2. From my calculation, it looks like I will need double the capacity I have, and I havent even added my other fridge yet?
    3. How are you guys working out with something like an 80w panel and not moving for 2 - 3 days?
    4. Where have I gone wrong in these calculations?
    Last edited by AcidHawk; 2020/06/03 at 10:07 AM.

  2. #2
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    Default Re: Solar decisions

    Quote Originally Posted by AcidHawk View Post
    Huh? I thought I had a little understanding of what I needed but now I am all confused again.
    Off hand you need 150 watt solar panel , 105 amp battery and the ctek 250 dual charger and you should be fine.
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    Angry Re: Solar decisions

    AAAARRRRGGGHHHHH .. where did all my tables go .....

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    Default Re: Solar decisions

    Forum doesn't do table display, you must attach
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    Default Re: Solar decisions

    Perhaps also add your power requirements for fridge/freezer ect so that the knowledgeable people can assist.
    Bear in mind you can have two 80w panels with hinges folded onto itself. When driving powered from alternator, when stationary fold open solar panels, works for me, two 80w panels folded onto itself, however I have them folded inside back of bakkie, 9m cord, sunseeking when stationary, works a charm
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    Default Re: Solar decisions

    Let's wait for your tables to see what equipment you will use on the system apart from the fridge.

    But so far I can say having bluetooth monitoring either on a external monitor or directly on the battery is a super handy feature, so go for the Blue Nova with bluetooth.
    Last edited by bigboy529; 2020/06/02 at 06:54 PM.
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    Default Re: Solar decisions

    Quote Originally Posted by Johan Engelbrecht View Post
    Perhaps also add your power requirements for fridge/freezer ect so that the knowledgeable people can assist.
    Bear in mind you can have two 80w panels with hinges folded onto itself. When driving powered from alternator, when stationary fold open solar panels, works for me, two 80w panels folded onto itself, however I have them folded inside back of bakkie, 9m cord, sunseeking when stationary, works a charm
    I am busy with just such a setup.

    Except it'll be a single 120w with the option to add a second.
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    Default Re: Solar decisions

    Quote Originally Posted by Garthox View Post
    I am busy with just such a setup.

    Except it'll be a single 120w with the option to add a second.
    Careful with large single panels. Rather have 2 x 80W hinged together. And make them portable.

    To me being forced to park in the sun to keep beer cold makes no sense at all
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    Default Re: Solar decisions

    Quote Originally Posted by Dungbeetle View Post
    Careful with large single panels. Rather have 2 x 80W hinged together. And make them portable.

    To me being forced to park in the sun to keep beer cold makes no sense at all
    Some have a different approach. Like me for example

    I have a 260W single panel mounted on the roof which is out of the way and because of the size does not need sun tracking, for my setup anyway. Used to have 2x 80W panels which I changed for my current setup which I am over the moon with.

    I want cold beers, so if it means that I have to park in the sun, then so be it.
    If Force is not the solution, not enough of it was applied....

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    Default Re: Solar decisions

    Also without cranking any numbers I can tell you now that a 80 Watt panel will not be nearly enough for two fridges. Even with just one fridge and battery you will only be marginally ok.

    I have 2 x 85Watt panels hinged as suggested above. This keeps my battery (a 150Ah running a 90L NL dual) full during the day, provided I move them no less than 3 times to follow the sun. It is good to provide extra capacity in terms of energy storage as well the energy source.

    If you drive an hour or so a day and only open the fridges when absolutely necessary, your will be ok with leaving the panels flat without following the sun trajectory. The rest, your alternator will take care of.

    Being able to see what your battery does in terms of amps in and out is 80% of the battle won. The Bluetooth feature sounds worth it if not too expensive.

    I went a much simpler route and merely installed 2 volt/amp meters on load and source side. Now while they are faaar from being able to accurately provide your battery's true state of charge, it allows me at any given time to see if my load amps is exceeding the source amps and I can move the panels and take preventive action.

    Depending on what your budget is, you could also consider 2 cheaper deep cycles and rather invest in a proper battery monitor such as the one from Victron. That alone would set you back just north of R3k. There are 3 models of which two also has Bluetooth.

    My panels are mounted on runner slides. So I can slide them out and open them, and I can even detach them with 2 small levers on each slide.

    They slide beneath my RTT load bars on the canopy.

    I'll look for some photos.
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    Default Re: Solar decisions

    Quote Originally Posted by jelo View Post
    Forum doesn't do table display, you must attach
    This was most frustrating ... I had links to all the solar panels as well as to the manuals of my devices... what a waste of time.

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    Default Re: Solar decisions

    Quote Originally Posted by Garthox View Post
    I am busy with just such a setup.

    Except it'll be a single 120w with the option to add a second.
    My thinking around having more than one (3x 90w in my case) is that if I wire them in parallel and one stops working the other 2 will continue. The fairy light analogy was explained to me here. if one stops working you don't lose all power harvesting capabilities.

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    Default Re: Solar decisions

    Quote Originally Posted by AcidHawk View Post
    My thinking around having more than one (3x 90w in my case) is that if I wire them in parallel and one stops working the other 2 will continue. The fairy light analogy was explained to me here. if one stops working you don't lose all power harvesting capabilities.
    You have to wire in parallel with the Ctek. But judging from your original post you already know this.

    This will give you 270 Watts and a quick search revealed that the max watts the unit can take is 250W Just make absolutely sure about this.

    And they don't sommer stop working. Panels are very robust.
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    Default Re: Solar decisions

    Photos of my setup.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Nico Swart

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  21. #15
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    Default Re: Solar decisions

    Quote Originally Posted by Pietsweis View Post
    Some have a different approach. Like me for example

    I have a 260W single panel mounted on the roof which is out of the way and because of the size does not need sun tracking, for my setup anyway. Used to have 2x 80W panels which I changed for my current setup which I am over the moon with.

    I want cold beers, so if it means that I have to park in the sun, then so be it.


    My approach is also to permanently mount panels and compensate by upping the size a bit. My thinking is no matter where you camp, a large part of your rig will be in the sun for a large part of the day, unless of course you camp under a solid roof. I guess this holds more true for caravans and trailers with mounted panels than for vehicles.
    Since I can remember, we only once camped at a place where mounted panels on the caravan didn't work, that was last year June at Mapungubwe where we camped under a massive baobab tree where we were in the shade during the entire day.
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    Default Re: Solar decisions

    Quote Originally Posted by Die SwartKat View Post
    Also without cranking any numbers I can tell you now that a 80 Watt panel will not be nearly enough for two fridges. Even with just one fridge and battery you will only be marginally ok.

    I have 2 x 85Watt panels hinged as suggested above. This keeps my battery (a 150Ah running a 90L NL dual) full during the day, provided I move them no less than 3 times to follow the sun. It is good to provide extra capacity in terms of energy storage as well the energy source.

    If you drive an hour or so a day and only open the fridges when absolutely necessary, your will be ok with leaving the panels flat without following the sun trajectory. The rest, your alternator will take care of.

    Being able to see what your battery does in terms of amps in and out is 80% of the battle won. The Bluetooth feature sounds worth it if not too expensive.

    I went a much simpler route and merely installed 2 volt/amp meters on load and source side. Now while they are faaar from being able to accurately provide your battery's true state of charge, it allows me at any given time to see if my load amps is exceeding the source amps and I can move the panels and take preventive action.

    Depending on what your budget is, you could also consider 2 cheaper deep cycles and rather invest in a proper battery monitor such as the one from Victron. That alone would set you back just north of R3k. There are 3 models of which two also has Bluetooth.

    My panels are mounted on runner slides. So I can slide them out and open them, and I can even detach them with 2 small levers on each slide.

    They slide beneath my RTT load bars on the canopy.

    I'll look for some photos.


    In my opinion opting for lead acid in the place of lithium just to add a good battery monitor, will be like taking 20 steps backwards. The info provided by the Blue Nova on board bluetooth will be enough for now, if OP wants more in future, he can always add a Victron monitor at a later stage.
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    Default Re: Solar decisions

    Quote Originally Posted by Die SwartKat View Post
    You have to wire in parallel with the Ctek. But judging from your original post you already know this.

    This will give you 270 Watts and a quick search revealed that the max watts the unit can take is 250W Just make absolutely sure about this.
    Thanks for the warning. Melt, the CTek National Brand Manager from Enertec said the D250SE is rated for up to 300W which I confirmed here

    Quote Originally Posted by Die SwartKat View Post
    And they don't sommer stop working. Panels are very robust.
    Thank you for this ... this is good to know. Wiring in parallel also keeps the Voc below the limitation of the D250SE though of 23v.

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    Default Re: Solar decisions

    Quote Originally Posted by bigboy529 View Post
    In my opinion opting for lead acid in the place of lithium just to add a good battery monitor, will be like taking 20 steps backwards. The info provided by the Blue Nova on board bluetooth will be enough for now, if OP wants more in future, he can always add a Victron monitor at a later stage.
    Maybe yes, maybe not. It is all about the numbers.

    How long are those lithium batteries guaranteed for and what do they cost? Batteries needs replacement at some time and then you spend that money again.

    A battery monitor is for life and I've had great results with normal VRLA batteries for years now. In fact, I've never had aux batteries give me less than 5 years and I have been running dual battery setups since 2001. But you need to look after them. I buy the same batteries everytime as I have come to trust them.

    OP should crank the financial numbers and decide.
    Last edited by Die SwartKat; 2020/06/03 at 11:26 AM.
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    Default Re: Solar decisions

    Quote Originally Posted by AcidHawk View Post


    1. How will I ever be able to keep up with that load requirement?
    2. From my calculation, it looks like I will need double the capacity I have, and I havent even added my other fridge yet?
    3. How are you guys working out with something like an 80w panel and not moving for 2 - 3 days?
    4. Where have I gone wrong in these calculations?
    80 watt panel will theoretical provides 80/14vx7hx.9eff= 36 Ah , if you move it around the catch max sun

    The tables are there if you use reply. A fridge draws about max 50 Ah per day or 600watts in hot conditions, depends also how you uses it, and a cell phone not nearly as indicated. LED light consumption you can ignore. 160 watt panel can give you easily 160watt/14v x 6h x .9eff from the ctek, about 60 ah at peak charging. An hour or so charging from the alternator will see you through easily.
    Last edited by JLK; 2020/06/03 at 11:51 AM.
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    Default Re: Solar decisions

    Quote Originally Posted by AcidHawk View Post
    Thanks for the warning. Melt, the CTek National Brand Manager from Enertec said the D250SE is rated for up to 300W which I confirmed here



    Thank you for this ... this is good to know. Wiring in parallel also keeps the Voc below the limitation of the D250SE though of 23v.
    Happiness!

    The site I was on did state the D250SE, but I supposed the 250W limit referred to the previous model D250S like I have.
    Last edited by Die SwartKat; 2020/06/03 at 02:14 PM.
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