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anyone wanna help me convert my 12v diagram to 24?

starchy

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Jan 8, 2021
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i'm not sure what an appropriate rate for this kind of service is but i am willing to pay. i'm just kind of burnt out on iterating this thing and would love to just follow a diagram that i know will work. attached is my most recent iteration of the 12v system i was gonna pursue.
 

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A few notes:

1)You will need a 24V inverter What size inverter will it be? Efficiency?
2) I assume you will have 12V loads. What is the total DC load?
3) Fuses are needed on each string of solar panels
4) I can not calculate wire and fuse sizes without more info.
5) The original diagram showed negatives going to the fuse lugs of the Lynx. That is incorrect.

1632446558826.png
 
Ask a you shall receive.
This one is free.
Code:
dc_domain {
    legend {
        {} { braces deliniate a functional block }
        label {} { label followed by empty braces means there is no connection to this functional block }
        label { label not followed by braces means the connection to the functional block has already been defined }
        . { label containing "." indicates a canonical name }
        * { comment }
        nnn|NNN| { fused busbar position where nnn is the wire guage and NNN is the fuse rating in amps }
        nnn|UUU| { un-fused busbar position where nnn is the wire guage }
        <- { uni-directional current flow }
        -> { uni-directional current flow }
        <-> { bi-directional current flow }
        pos { positive }
        neg { negative }
        eg { equipement ground }
        * some items are basic enough to not require further definition, for example "200A_t_fuse"
        * some items are drawn in-line if there obvious, for example "scc"
    }
    main {
        pos {
            2/0|UUU|<->disconnect<->200A_t_fuse<->batteries.pos
            006|100|<-scc<-dpst_breaker<-panels.pos
            2/0|200|->inverter.pos
            006|100|->24_12_buck_converter->fuse_block.main.pos
            014|015|->shunt.pos
        }
        neg {
            2/0|UUU|<->shunt<->batteries.neg
            006|UUU|->scc->dpst_breaker->panels.neg
            2/0|UUU|<-inverter.neg
            006|UUU|<-24_12_buck_converter<-fuse_block.main.neg
            006|UUU|<->scc.eg
            2/0|UUU|<->inverter.eg
            2/0|UUU|<->chassis_bond
        }
    }
    fuse_block {
        main {
            pos
            neg
        }
        branches {
            pos {}
            neg {}
        }
    }
    panels {
        pos { panel_in_series<-panel_in_series<-panel_in_series<-panel_in_series }
        neg { panel_in_series->panel_in_series->panel_in_series->panel_in_series }
    }
    inverter {
        pos
        neg
        eg
    }
    scc {
        battery {
            pos
            neg
        }
        pv {
            pos
            neg
        }
        eg
    }
    shunt {
        neg {
            bat
            aux
        }
        pos
    }
    dpst_breaker { * double pole single throw breaker
        panels {
            pos
            neg
        }
        scc {
            pos
            neg
        }
    24_12_buck_converter {
        bat {
            pos
            neg
        }
        aux {
            pos
            neg
        }
    }
}
 
Last edited:
In a camper van / RV I'd never walk away from 12 V. Cable runs are short and most runs on 12 V to begin with.
 
Ask a you shall receive.
This one is free.
Code:
dc_domain {
    legend {
        {} { braces deliniate a functional block }
        label {} { label followed by empty braces means there is no connection to this functional block }
        label { label not followed by braces means the connection to the functional block has already been defined }
        . { label containing "." indicates a canonical name }
        * { comment }
        nnn|NNN| { fused busbar position where nnn is the wire guage and NNN is the fuse rating in amps }
        nnn|UUU| { un-fused busbar position where nnn is the wire guage }
        <- { uni-directional current flow }
        -> { uni-directional current flow }
        <-> { bi-directional current flow }
        pos { positive }
        neg { negative }
        eg { equipement ground }
        * some items are basic enough to not require further definition, for example "200A_t_fuse"
        * some items are drawn in-line if there obvious, for example "scc"
    }
    main {
        pos {
            2/0|UUU|<->disconnect<->200A_t_fuse<->batteries.pos
            006|100|<-scc<-dpst_breaker<-panels.pos
            2/0|200|->inverter.pos
            006|100|->24_12_buck_converter->fuse_block.main.pos
            014|015|->shunt.pos
        }
        neg {
            2/0|UUU|<->shunt<->batteries.neg
            006|UUU|->scc->dpst_breaker->panels.neg
            2/0|UUU|<-inverter.neg
            006|UUU|<-24_12_buck_converter<-fuse_block.main.neg
            006|UUU|<->scc.eg
            2/0|UUU|<->inverter.eg
            2/0|UUU|<->chassis_bond
        }
    }
    fuse_block {
        main {
            pos
            neg
        }
        branches {
            pos {}
            neg {}
        }
    }
    panels {
        pos { panel_in_series<-panel_in_series<-panel_in_series<-panel_in_series }
        neg { panel_in_series->panel_in_series->panel_in_series->panel_in_series }
    }
    inverter {
        pos
        neg
        eg
    }
    scc {
        battery {
            pos
            neg
        }
        pv {
            pos
            neg
        }
        eg
    }
    shunt {
        neg {
            bat
            aux
        }
        pos
    }
    dpst_breaker { * double pole single throw breaker
        panels {
            pos
            neg
        }
        scc {
            pos
            neg
        }
    24_12_buck_converter {
        bat {
            pos
            neg
        }
        aux {
            pos
            neg
        }
    }
}
awesome! ty! do you know if there's a way to convert this to a flowchart?
 
A few notes:

1)You will need a 24V inverter What size inverter will it be? Efficiency?
2) I assume you will have 12V loads. What is the total DC load?
3) Fuses are needed on each string of solar panels
4) I can not calculate wire and fuse sizes without more info.
5) The original diagram showed negatives going to the fuse lugs of the Lynx. That is incorrect.

View attachment 66020
oh awesome. thanks! inverter? idk, i guess i'm gonna sell my 12v one and buy this one? https://www.amazon.com/dp/B07JQKQQTP/ref=redir_mobile_desktop?_encoding=UTF8&*Version*=1&*entries*=0

the panels are 100 watts each. pic attached. someone on another thread told me to just keep the existing wire sizes but downsize the ones to the inverter to 2/0, from memory. i'll have to find the post...
 

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oh awesome. thanks! inverter? idk, i guess i'm gonna sell my 12v one and buy this one? https://www.amazon.com/dp/B07JQKQQTP/ref=redir_mobile_desktop?_encoding=UTF8&*Version*=1&*entries*=0
OK....you want a 3000W inverter.
The inverter you linked to is probably about 85% efficient so at full load it will draw 3000W/.85=3529W. That means if the batteries are low it will be drawing 2529W/24V=147A. You never want to run a fuse or breaker right at its trip point so the fuse should be at least 147A x 1.25 = 184A. Round that up to a 200A Fuse. For 200A 2/0 sounds about right for the wiring to the Inverter.

However, the battery cabling and fuse may need to be larger in order to also handle the DC loads: What is the max current you will see from your DC loads?

Note: The Giandle inverter you are looking at is low cost... but you get what you pay for. I had the exact same model and it struggled to start a microwave. I also had problems where it would stop working and I had to power it down and then back up for it to start working again. I ended up swapping it with a 3000W Victron MultiPlus (yes.... I went to the other extreme...but I only regretted it at the moment I had to pay for it..... ever since I have been happy I did it.
 
BTW: The in-line fuses for the panels should be at least 5.7A x 1.55 = 8.8A....round up to 10A.

The wire running to the controller needs to be the larger of the following:
1) Fire safety calculation: large enough to handle 8.84 x 4 = 35A (8AWG)
2) Voltage drop calculation: large enough to have an acceptable voltage drop for 5.5A x 4 = 22A, I do not know how long your run is so I can't help much with this)
NOTE: I use the Impp for voltage drop calculations because that is closer to the normal operating condition. However, I will sometimes bump it up one size just to make sure all conditions are covered.
 
OK....you want a 3000W inverter.
The inverter you linked to is probably about 85% efficient so at full load it will draw 3000W/.85=3529W. That means if the batteries are low it will be drawing 2529W/24V=147A. You never want to run a fuse or breaker right at its trip point so the fuse should be at least 147A x 1.25 = 184A. Round that up to a 200A Fuse. For 200A 2/0 sounds about right for the wiring to the Inverter.

However, the battery cabling and fuse may need to be larger in order to also handle the DC loads: What is the max current you will see from your DC loads?

Note: The Giandle inverter you are looking at is low cost... but you get what you pay for. I had the exact same model and it struggled to start a microwave. I also had problems where it would stop working and I had to power it down and then back up for it to start working again. I ended up swapping it with a 3000W Victron MultiPlus (yes.... I went to the other extreme...but I only regretted it at the moment I had to pay for it..... ever since I have been happy I did it.
not sure about my max current from dc loads. i'll look into it. dc appliances will be a few lights, a small fridge, a small vent fan and a fresair air cooler.

also i'm not sure about that circuit breaker i have on there. it's just what vanlifeoutfitters use on their diagram (attached) i used as a springboard for mine (also attached w/ wire gauges and amp sizes added). looks like these:

 

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Last edited:
also i'm not sure about that circuit breaker i have on there. it's just what vanlifeoutfitters use on their diagram (attached) i used as a springboard for mine (also attached w/ wire gauges and amp sizes added). looks like these:
I assume you are talking about the breaker between the panels and the solar charge controller. For the configuration you have, that should be at least a 35A or larger DC breaker. The fact is, only a dual pole disconnect is needed there, not a breaker. It just happens to be easy and relatively low cost to use a dual pole breaker as the disconnect.

The original Van Life diagram did not have parallel strings of panels like shown on your modified diagram. With more than 2 parallel strings, there needs to be in-line fuses or breakers on each string. With your configuration, they need to be 10A. (Note: This could also be done with a combiner box to hold in-line breakers)

1632527705110.png

It is interesting that the Van Life diagram also incorrectly showed the negative going to the fuse lugs in the Lynx.
 
not sure about my max current from dc loads. i'll look into it. dc appliances will be a few lights, a small fridge, a small vent fan and a fresair air cooler.
Lets assume 30A for your DC load. That means you will need the Victron 24/12-30 dc-dc converter.
Lets assume the converter operates at 90% efficiency.... that means you will need (30/.9)/2 = 16.7amps feeding it. Adding that to the 147A for the inverter and we get 164A. That means you should have a battery fuse rated at 164 * 1.25= 205A.
I would recommend a 225A battery fuse and 3/0 wire to/from the battery (4/0 if you can't find 3/0). You could squeak by with 2/0 wire and a 200A fuse, but technically that is too small.
 
I just noticed that you have 1200W of Panels but your 150/35 controller will only let through ~28V x 35A = 980W. (Less if the battery is empty and at 24V) However, this still may be OK.
- Panels rarely produce to their ratings so you may not get to 980W anyway.
- You will get better cloudy day production than if you had only 980W of panels.
- Your power will ramp up to the 980W sooner and stay their longer on sunny days than it would if you only had 980W of panels.

A question: Will all 12 panels be in the sun at the same angle and no shading?.
 
I just noticed that you have 1200W of Panels but your 150/35 controller will only let through ~28V x 35A = 980W. (Less if the battery is empty and at 24V) However, this still may be OK.
- Panels rarely produce to their ratings so you may not get to 980W anyway.
- You will get better cloudy day production than if you had only 980W of panels.
- Your power will ramp up to the 980W sooner and stay their longer on sunny days than it would if you only had 980W of panels.

A question: Will all 12 panels be in the sun at the same angle and no shading?.
yeah i haven't actually bought that scc yet. tho i do have 3 of these (attached) i could use? (from a previous iteration of the build)

same angle, yes. all level w/ one another. this is for my exteneded body ram promaster. yes, it can technically accommodate 12 panels. 3 in a row w/ 4 rows. they go a bit over the sides but beyond the actually end of the van, which is sort of egg shaped.
 

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yeah i haven't actually bought that scc yet. tho i do have 3 of these (attached) i could use?
Yes, those could be used, but I do not have any experience with them.

On RV installs, one problem is that you never know what is going to happen with shading in the campsite you end up in, Consequently, it is wise do your panel arrangement and install assuming the worst.

If you have 3 of those controllers and room in the RV, you could consider putting all three in so if some of the panels are shaded there is no chance of it impacting the others. You could put 2 parallel strings of 2 in series on each of the 3 controllers. One added benefit of doing this is that since no controller has more than 2 in parallel, you don't need the in-line fuses. The second benefit is that the combined capability of the 3 controllers is significantly greater than the 970W of your panels.

The other thing to do is to put a blocking diode on each serial string. That way if one string is weak, it does not pull down the others.

Finally, make sure there is a bypass diode on each panel.

 
BTW: There are several workable combinations using your EPEVER controllers

1632591505964.png1632591596305.png
* Max String Voltage:
The EPEVER has a max voltage of 100V so I would not go more than 3 in series. This will leave plenty of headroom for cold temperature voltage rise.

* Min String Voltage:
Since you are looking at a 24V system, you need at least two in series in order to have enough voltage to charge the battery.

Here are the most obvious combinations
1 EPEVER - 12 panels on a single controller
  • Use 4 sets of 3 in series. (OK for shading and needs in-line fuses)
    Note that the 1200W rating for the panels is slightly higher than the 1040W capability of the controller.
    Most (all?) MPPT controllers can be over-paneled like this but you should make sure the EPEVER can.
2 EPEVERs - 6 Panels on each controller
  • On each controller use 3 sets of 2 in series. (Good for shading but needs in-line fuses)
  • On each controller use 2 sets of 3 in series. (Not quite as good for shading but does not need in-line fuses)
3 EPEVERs - 4 panels on each controller
  • On each controller use 2 sets of two in series (best for shading and does not need in-line fuses)
Note: There are many other asymmetric arrangements, but I am not sure there is any advantage to them.
Note: In all cases, proper use of bypass and blocking diodes will help minimize the effects of shading.
 
Yes, those could be used, but I do not have any experience with them.

On RV installs, one problem is that you never know what is going to happen with shading in the campsite you end up in, Consequently, it is wise do your panel arrangement and install assuming the worst.

If you have 3 of those controllers and room in the RV, you could consider putting all three in so if some of the panels are shaded there is no chance of it impacting the others. You could put 2 parallel strings of 2 in series on each of the 3 controllers. One added benefit of doing this is that since no controller has more than 2 in parallel, you don't need the in-line fuses. The second benefit is that the combined capability of the 3 controllers is significantly greater than the 970W of your panels.

The other thing to do is to put a blocking diode on each serial string. That way if one string is weak, it does not pull down the others.

Finally, make sure there is a bypass diode on each panel.

so, like, these?


installed where the inline fuses are? also, i guess i'll need waterproof fuses? like this?


i think will prowse mentions that these epever scc's will play nice together but maybe it's worth it to flip 'em and just buy one that'll accomodate 1200 watts. is there one you'd recommend?
 
BTW: There are several workable combinations using your EPEVER controllers

View attachment 66270View attachment 66271
* Max String Voltage:
The EPEVER has a max voltage of 100V so I would not go more than 3 in series. This will leave plenty of headroom for cold temperature voltage rise.

* Min String Voltage:
Since you are looking at a 24V system, you need at least two in series in order to have enough voltage to charge the battery.

Here are the most obvious combinations
1 EPEVER - 12 panels on a single controller
  • Use 4 sets of 3 in series. (OK for shading and needs in-line fuses)
    Note that the 1200W rating for the panels is slightly higher than the 1040W capability of the controller.
    Most (all?) MPPT controllers can be over-paneled like this but you should make sure the EPEVER can.
2 EPEVERs - 6 Panels on each controller
  • On each controller use 3 sets of 2 in series. (Good for shading but needs in-line fuses)
  • On each controller use 2 sets of 3 in series. (Not quite as good for shading but does not need in-line fuses)
3 EPEVERs - 4 panels on each controller
  • On each controller use 2 sets of two in series (best for shading and does not need in-line fuses)
Note: There are many other asymmetric arrangements, but I am not sure there is any advantage to them.
Note: In all cases, proper use of bypass and blocking diodes will help minimize the effects of shading.
ok, i guess i'd go w/ the second one, 2 sets of 3 in series since they'll already be arranged in rows of 3 up there.
 
it doesn't appear to mention overpaneling on the .pdf i found so 4 sets of 3 in series on one epever may be out.
 

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