Camper with a twist

gobox

Hi folks,

Firstly, thanks for this forum of great information!

I have just signed up and have been looking for a bit, I have always been interested in solar power and have dabbled in it at small levels but the interest has been strong. For the most part I hate math, and that is usually the one thing that destroys my interest in some hobbies or work related items, and this solar thing seems to be very much math/formula related but I am jumping in anyway.

What I do want to have though is a system for my camping rig. The bits that I now have in place are batteries, four deep cycle 235 ah 6 volt batteries that aren't trojans but when they die will be. The other bits are three uni-solar 68watt panels, maybe not the best choice but too late now. I am in the process of calculating my loads, which will be the typical items found in campers; lights, etc, my largest draw will be a compressor fridge that when on draws 4.2 amps, and says to plan on
50amps for a 24 hr period at 30'C. As it is I can go three days before my batteries are around 12.2 volts which is usually about the length of time before moving and recharging.

I have a few ideas and considerations in mind, total watts from the panels will be low, 204watts, but the plan was to have an additional solid panel that can connect to the system and be mobile, reason is camping in the shade and putting the other panel out in the sun. With that comes some problems I think, one being the other panel with differing voltages perhaps, I am looking at the morning star trimark 45 mppt unit, will this unit deal with the two different panels? Or should I go with two separate controllers? Keeping in mind that when camped I may be in shade and the three unisolar panels will not be producing much.
My hope here is to extend my time in one place without a full recharging but it seems that a full charge is something that is required or the batteries will fail.

Should I hook the unisolar panels up in series or parallel? I want to say in series here but that may depend on if I go with one or two controllers??

The other problem I foresee is a lack of fully charging my batteries, but that I am not sure of. I guess this is the math part,, gulp,,, can this work??
I do have a few other bits that I havent mentioned yet, one is a a xantrex 600 watt pure sine wave inverter and xantrex link lite battery monitor, and at present I am not sure of where the monitor should be wired in.
Well there's a good start on my first post, I hope that I can get my system working, has anyone else done a system like this? Any help and feedback is welcome.

Thanks

Cariboocoot

Re: Camper with a twist

Welcome to the forum.

So what you've got now is a 12 Volt system with 470 Amp hours of battery and 204 Watts of panel, right?

I'm famous for saying this: You need more panel for that much battery.

If you're going for full charging ability from the solar, that much battery would want 732 Watts of panel. As it is, your peak charging current is probably around 13 Amps which is less than 3% of the battery capacity - far under the 5% minimum recommendation. If you're charging off solar alone now it's a wonder the batteries get recharged at all.

You might be better off to cut that battery bank in half and recharge it at a quicker rate, especially if you only use 50 Amp hours per day.

There's really no point in wiring the panels in series and using an MPPT controller unless you have long wire runs, which isn't likely on a camper.

Adding "mobile" panels to be set out when you're in shade is something that's quite popular amongst the camping set. The drawbacks are their vulnerability to damage and theft. The advantage is being able to keep the camper cool and charged.

As for mixing different panels, it comes down to how different they are. For parallel connections the Vmp ratings need to be close. For serial connections it's the Imp rating that matters. In this case where you'll have panels with two different orientations the MPPT controller could not handle both at once; it will likely pick the wrong "sweet spot" power setting. A single PWM type could be used, providing the panel Vmps are close. Again the mobile panel(s) might present issues with long wiring runs, necessitating their own controller of the MPPT type.

If you can get a good fix on your actual daily Watt hour needs it will make it much easier to tailor the rest of the system. That number will tell how much battery you really need, which in turn will dictate panels & controller set-up.

Hamfast

Re: Camper with a twist

I'm famous for saying this: You need more panel for that much battery.

Yup...He tagged me too... :cool:

gobox

Re: Camper with a twist

thanks for the welcome,
cariboocoot, the answer to your first question is I have no system yet, all I have are the batteries doing all the work and either getting brought up by a charger when home or alternator when driving, and these three unisolar panels, I am aware of not having enough panels and that is why I would like to use a mobile one, the dilemma is what would be the best way of doing it? If there is a way of making it happen using one controller would be the easiest, matching up another panel seems to be do able with so many options but I am not sure what has to match, the best " sweet spot" as you wrote:D

My original expectations were to have solar to allow longer stays in one spot, but then after reading many items on how batteries are maintained I am not sure in which direction to go, it all does depend on how this system will be used, and that is my problem.

Without the worry of vandalism or theft how would you go about using the panels and batteries I have and have the ability to park in the shade and lengthen the time before needing a good charge up? Would you go with two controllers?, series?, one big portable pane?l, two? Unfortunately it seems silly to design a system with stuff already purchased but that is what I have, but I also have options on controllers and a panel or two of whatever would suit. I just dont have enough knowledge yet to decide on what to do.

Cariboocoot

Re: Camper with a twist

If you're charging those batteries off the alternator or a standard automotive charger they're not getting the full charge they need. You already know that, though.

So the first issue is do you need all that battery capacity? If you could recharge daily, how much would you need? The more battery you have, the more expensive it is to recharge them. You say that as it is you can go 3 days, so half the battery capacity would give you 1.5 days. The Unisolar panels would barely recharge that much.

Something that's just entered my head is the notion these Unisolar batteries have a very high (or is it low?) Vmp. If so, an MPPT controller is necessary for them no matter what. Do you have the actual panel specs?

It is possible, with the right panels, to have both fixed and "mobile" panels on the same PWM controller.

If you have only these panels and want to put them in the sun for extending your between-charge time I'd use the Morningstar 15 Amp MPPT controller: http://www.solar-electric.com/mosumpsochco.html Wire the panels in series (if the Voc is low enough) and then you should have no trouble running the higher Voltage through fairly long wires to the controller. It will take care of the rest.

These Unisolars are the flexible ones, right? So mounting them for moving could be a challenge. You'd have to think about what would work best for you in terms of practical storage and deployment. The only sure-fire way to prevent theft and damage is to watch them every minute, so that's something you have to think about too. On the plus side, you'll be able to adjust them through the day to keep them aimed at the sun (manual tracking) which will yield more over-all power than a fixed mounting system.

gobox

Re: Camper with a twist

Here are the panel specs:

Electrical Performance at Standard Test Conditions
(STC) (1000 W/m2, AM 1.5, 25°C Cell Temperature)
ePVL-68
Maximum Power (Pmax): 68 W
Voltage at Pmax (Vmpp): 16.5 V
Current at Pmax (lmpp): 4.1 A
Short-circuit Current (Isc): 5.1 A
Open-circuit Voltage (Voc): 23.1 V
Maximum Series Fuse Rating: 10 A
Limiting Reverse Current: 10 A


These will be mounted onto the camper full time and not be portable, but I did have a concern about the Vmp and voltage drop in general, thats why I was thinking of wiring in series, the mobile panel(s) will be a regular pv panel and not amorphous if I spelled that right and I haven't bought that yet.
I would like to keep the batteries because when we travel we will stop and stay somewhere for a while, and if its not suitable to set out the mobile panel due to worrying about theft we can still have the option of staying for a while. For the most part we camp in remote locations.
I guess I am asking for all the cake and I want to eat it all too:roll:

Cariboocoot

Re: Camper with a twist

Okay that Vmp is too low for charging. When the panels get hot it will go lower. Add the losses in wiring & charge controller and you could easily find they don't put out enough Voltage to bring the batteries to 14.4 Absorb, much less equalization Voltage.

The solution is to run the three in series through the 15 Amp Morningstar MPPT controller I linked to before.

Unfortunately this means your mobile panel will have to have its own controller. But it won't need to be an MPPT type if you pick a panel with a Vmp around 17.5-18 like the Kyocera 135 http://www.solar-electric.com/kykd135wa12v.html or 140 http://www.solar-electric.com/kykd140wasom.html . Larger panels than that tend to have too high a Vmp for a 12 Volt system. Two of those small ones would add 270 to 280 Watts to your existing 204 and about double the charging rate potential, meaning you could keep all four batteries happy given a spot of good weather.

The small panels are easier to handle too.

vtmaps

Re: Camper with a twist

Hi gobox, welcome to the forum.
It certainly is possible to have two different arrays with different types of panel all hooked up to one controller, but its tricky and will lead to all sorts of compromises. My advice is to get an inexpensive PWM controller for your permanently mounted unisolar panels, and a MPPT controller for your portable panels. If you go that route you will need a combiner box with fuses for the unisolar panels (three panels in parallel).

For the portable array, you may be able to get away without a combiner box (one or two series strings needs no combiner with fuses). The higher voltage of a series string will help with the voltage drop. You will need to educate yourself about the dangers of connecting and disconnecting those panels during daylight hours.

--vtMaps

edit: I just saw Cariboocoot's post. He recommends against a PWM for the unisolar. Trust him.

gobox

Re: Camper with a twist

That looks like a good option, ease of carrying and set up is a good idea, thanks. Just so that I understand,, if there are two panels that have different Vmp, the mppt controller will use the lower voltage to charge?
Are there any other options that you can think of?

gobox

Re: Camper with a twist

vtmaps wrote: »

Hi gobox, welcome to the forum.
It certainly is possible to have two different arrays with different types of panel all hooked up to one controller, but its tricky and will lead to all sorts of compromises. My advice is to get an inexpensive PWM controller for your permanently mounted unisolar panels, and a MPPT controller for your portable panels. If you go that route you will need a combiner box with fuses for the unisolar panels (three panels in parallel).

For the portable array, you may be able to get away without a combiner box (one or two series strings needs no combiner with fuses). The higher voltage of a series string will help with the voltage drop. You will need to educate yourself about the dangers of connecting and disconnecting those panels during daylight hours.

--vtMaps

edit: I just saw Cariboocoot's post. He recommends against a PWM for the unisolar. Trust him.

Hi vtmaps,
I missed your post before responding but you do bring up something that I havent read about and that is fuses at the combiner box at the panels ( I may know those as a junction boxes if thats the same thing? ) is this something that is needed and why? Where can I read about that?

Cariboocoot

Re: Camper with a twist

gobox wrote: »

That looks like a good option, ease of carrying and set up is a good idea, thanks. Just so that I understand,, if there are two panels that have different Vmp, the mppt controller will use the lower voltage to charge?
Are there any other options that you can think of?

No.
The MPPT controller in this case is to enable the low Vmp panels to be used by stringing them in series. 16.5 is just too low for any system really.

No controller can match mismatched panels. If the Vmp (or Imp) is off, power is lost going in to the controller.

MPPT controllers don't like panels pointing in different directions; they won't find the right power point. PWM controllers don't care; they just pass whatever current is being produced by the panels.

Cariboocoot

Re: Camper with a twist

gobox wrote: »

Hi vtmaps,
I missed your post before responding but you do bring up something that I havent read about and that is fuses at the combiner box at the panels ( I may know those as a junction boxes if thats the same thing? ) is this something that is needed and why? Where can I read about that?

Individual fuses on panels are necessary whenever there are more than two parallel connections. If you were to use all three of the Unisolar panels they would have to each have a fuse. This is because if one of them shorts the other two can push 2X the maximum current through it and possible cause a fire. With all three in series to the MPPT controller this is not an issue.

Likewise if you have to of the Kyoceras in parallel it won't be a problem because either panel can take the full short-circuit current of the other if something should go wrong.

gobox

Re: Camper with a twist

Cariboocoot wrote: »

Individual fuses on panels are necessary whenever there are more than two parallel connections. If you were to use all three of the Unisolar panels they would have to each have a fuse. This is because if one of them shorts the other two can push 2X the maximum current through it and possible cause a fire. With all three in series to the MPPT controller this is not an issue.

Likewise if you have to of the Kyoceras in parallel it won't be a problem because either panel can take the full short-circuit current of the other if something should go wrong.

Thanks Cariboocoot,
I just finished reading something about that and it makes sense.
Is there a particular way to wire three panels in series? I will do some research.

BB.

Re: Camper with a twist

If you are tight for space and need more power... You should look at replacing those panels with poly-crystalline (very efficient), or mono-cyrstalline (more or less the most efficient "standard" silicon) panels.

The crystalline panels will generate almost 2x as much wattage as the thin film panels per square foot (yes--that would cost you a fair amount of cash--and crystalline panels are covered with 1/8 tempered glass--so they may be less impact resistant vs the thin film).

-Bill

Cariboocoot

Re: Camper with a twist

There's only one way to wire panels in series:

(-)PANEL(+)---(-)PANEL(+)---(-)PANEL(+)

calbiker

Re: Camper with a twist

As I see it, you got two options for the 3 panels you're mounting on the roof: PWM or MPPT, a $20 controller (ebay) or a $150 controller. If you go pwm, the panels are connected in parallel, mppt panels are connected in series.

The main drawback to pwm is your panel voltage is a little low. In your case, it's not such a big deal. While camping, due to your big load, battery voltage will always be below 13V. That means the panels will have enough voltage overhead to provide a good charge. You may have problems when it's real hot, but then you're probably in the shade and those panels won't be much use anyways.

You can test your panels without purchasing a pwm controller. Connect the 3 panels in parallel directly to the battery. Measure charging current as a function of battery voltage. With increasing battery voltage, there will be a point where charging current starts to decrease. That's the point where panel voltage headroom is lost. If battery voltage is greater than 12.8V then pwm is good enough. If less than 13V then use mppt. Be sure to use adequate sized cables for the test.

Cal

BB.

Re: Camper with a twist

For measuring current--if you are not using a true battery monitor--I would suggest getting a "cheap" DC Current Clamp Meter (Sears has this "good enough" clamp meter with AC/DC current and DMM function for ~$60).

Just clip on ONE wire and take a reading (you should play with the meter and understand how ZEROING works--I use my car battery/head lamps/etc. to make sure I was using the meter correctly. DC current meters tend to drift from zero within 10's of seconds to minutes--So you first hold the meter "in the area", zero it, then clip on the wire to measure--Make sure you only clip on one wire, if you clip on +/- wires (hot+return) together, the sum of the current is zero amps).

-Bill

gobox

Re: Camper with a twist

BB. wrote: »

If you are tight for space and need more power... You should look at replacing those panels with poly-crystalline (very efficient), or mono-cyrstalline (more or less the most efficient "standard" silicon) panels.

The crystalline panels will generate almost 2x as much wattage as the thin film panels per square foot (yes--that would cost you a fair amount of cash--and crystalline panels are covered with 1/8 tempered glass--so they may be less impact resistant vs the thin film).

-Bill

These panels are new but havent been set up yet so I really want to try them out without swapping plans. A couple of reasons I got them was for the weight, trying to keep the weight low where they will be placed, for the three I am looking at 28 pounds, I also was lured into them for the amorphous concept, I wanted a panel that was a no worry panel, stick it on the roof and thats it, no angling or moving of the panels. At the time I was not educated in the battery world so all I was looking for was a system to extend my times camping without doing a charge of some kind, and these will do that, but then the batteries get wrecked. I guess they were a bit of an impulse buy. I believe they will serve a purpose well, but not the complete recharge purpose.
Now I am looking at a good option on the mobile set up, and definately seems like what cariboocoot recommended sounds good.

gobox

Re: Camper with a twist

Cariboocoot wrote: »

There's only one way to wire panels in series:

(-)PANEL(+)---(-)PANEL(+)---(-)PANEL(+)

Wow thats complicated! Ok so its nothing special, but I had to ask, in this solar stuff you never know if its a more complicated thing, like the diagrams for wiring up four six volt batteries into a twelve volt parrallel set up, you just never know, thanks.

gobox

Re: Camper with a twist

calbiker wrote: »

As I see it, you got two options for the 3 panels you're mounting on the roof: PWM or MPPT, a $20 controller (ebay) or a $150 controller. If you go pwm, the panels are connected in parallel, mppt panels are connected in series.

The main drawback to pwm is your panel voltage is a little low. In your case, it's not such a big deal. While camping, due to your big load, battery voltage will always be below 13V. That means the panels will have enough voltage overhead to provide a good charge. You may have problems when it's real hot, but then you're probably in the shade and those panels won't be much use anyways.

You can test your panels without purchasing a pwm controller. Connect the 3 panels in parallel directly to the battery. Measure charging current as a function of battery voltage. With increasing battery voltage, there will be a point where charging current starts to decrease. That's the point where panel voltage headroom is lost. If battery voltage is greater than 12.8V then pwm is good enough. If less than 13V then use mppt. Be sure to use adequate sized cables for the test.

Cal

I am leaning towards using a morning star mppt controller with the three panels, I like that set up, but you are the second to say that when it gets hot these panels will have issues, what do you look at for that? I know these have a bit of a following in Australia, there are some companies that mount these on their very expensive expedition campers and swear by them, I am not very knowledgeable on them.
That test sounds interesting, so I am looking for a point where the voltage starts to drop off? Or will it just be a steady volt?

gobox

Re: Camper with a twist

BB. wrote: »

For measuring current--if you are not using a true battery monitor--I would suggest getting a "cheap" DC Current Clamp Meter (Sears has this "good enough" clamp meter with AC/DC current and DMM function for ~$60).

Just clip on ONE wire and take a reading (you should play with the meter and understand how ZEROING works--I use my car battery/head lamps/etc. to make sure I was using the meter correctly. DC current meters tend to drift from zero within 10's of seconds to minutes--So you first hold the meter "in the area", zero it, then clip on the wire to measure--Make sure you only clip on one wire, if you clip on +/- wires (hot+return) together, the sum of the current is zero amps).

-Bill

I have a xantrex link lite battery monitor, not hooked in the box still, I have just scanned the instructions so dont know much about it, I was wondering where the optimal location would be for the shunt, is there a "usual spot" that works or just follow the directions??
That clamp meter has been recommended many times, do you feel like its a tool that you couldn't live without? I do think they are neat though, pretty much magic isnt it?

BB.

Re: Camper with a twist

The Battery Monitor will work fine for you... Normally one end of the shunt is attached to the negative side of the battery (bank), and the other end of the shunt becomes or is attached to the common negative bus/frame/earth ground (as needed).

You want all battery current to flow through the shunt so you get accurate readings.

Regarding the DC Current Clamp Meter--Actually, I lived and worked about 40-50 years without one. Normally, I would find a length of wire and measure the voltage drop on in (2 volt or 200 mVolt full scale on meter). Worked "well enough" for most everything. In my engineering lab, I did have a very nice Tek DC Current Probe (around 12 amps max) that worked really well for measuring signals on disk drive read/write heads (again, in the olden days when those signals were accessible outside the HDA) and getting a current profile for the 12 volt spindle motor startup for power supply design.

Today--I would just go with the DC Current Clamp meter--Basically use it like standard DMM without having the whole issue of clipping leads into a power circuit to measure up to 10 amps of current. Much easier, many times safer, and you have an upper limit of 400 amps or so without the voltage drop of the shunt in the DMM.

If you don't need to measure DC current--I would not get one just to replace a good DMM I already have--But, I would get an AC/DC current clamp meter instead of another/first DMM. It is really handy.

Regarding installing a small system, Kevin from Calgary has a nice thread with some Youtube video with two panels, a battery monitor and a small MPPT charge controller.

-Bill

calbiker

Re: Camper with a twist

There's kind of an ideal design for a "12V" panel that's connected to a pwm controller. The panel has 36 cells and has a max power point voltage of about 17.6V at room temperature. Exposing the panel to the sun causes panel temperature rise and voltage drops. Your panel has a Vmp of 16.5V. It's a bit low for pwm use. But, as I mentioned before, your battery voltage is also low. They may compensate each other out. The alternative is connecting the panels in series (this raises operating voltage to 3 times Vmp) and using MPPT.

Regarding my proposed test to determine if your panels will work with a pwm controller. It sounds like you want to go with mppt. I don't want to write up a detailed test procedure if you are not going to do the test. Let me know if you're serious and will then provide further details. To answer your question, you're looking for the battery voltage when current starts to decreases. In pwm mode, charging current is about 3% lower than the panel's short circuit current (Isc = 5.1A max). At max irradiance, the pwm current should be 0.97 * 3 * 5.1A = 14.8A. You will see something less due to lower irradiance. If irradiance remains constant, this current will stay constant; even as battery voltage increases due to charging. There comes a point in time where charging current no longer is constant, but starts decreasing. The system has lost its voltage headroom. Of interest, what's the battery voltage when current starts to decrease.

Cal

gobox

Re: Camper with a twist

BB. wrote: »

The Battery Monitor will work fine for you... Normally one end of the shunt is attached to the negative side of the battery (bank), and the other end of the shunt becomes or is attached to the common negative bus/frame/earth ground (as needed).

You want all battery current to flow through the shunt so you get accurate readings.

Regarding the DC Current Clamp Meter--Actually, I lived and worked about 40-50 years without one. Normally, I would find a length of wire and measure the voltage drop on in (2 volt or 200 mVolt full scale on meter). Worked "well enough" for most everything. In my engineering lab, I did have a very nice Tek DC Current Probe (around 12 amps max) that worked really well for measuring signals on disk drive read/write heads (again, in the olden days when those signals were accessible outside the HDA) and getting a current profile for the 12 volt spindle motor startup for power supply design.

Today--I would just go with the DC Current Clamp meter--Basically use it like standard DMM without having the whole issue of clipping leads into a power circuit to measure up to 10 amps of current. Much easier, many times safer, and you have an upper limit of 400 amps or so without the voltage drop of the shunt in the DMM.

If you don't need to measure DC current--I would not get one just to replace a good DMM I already have--But, I would get an AC/DC current clamp meter instead of another/first DMM. It is really handy.

Regarding installing a small system, Kevin from Calgary has a nice thread with some Youtube video with two panels, a battery monitor and a small MPPT charge controller.

-Bill

I read Kevins thread and watched his videos, thanks for pointing it out, he is doing things similar to what I am thinking of doing.
That other stuff you were talking about, well sorry, all over my head there, never had any training in electrics like that.

Did Kevin ever get back to update if it works well or not?

gobox

Re: Camper with a twist

calbiker wrote: »

There's kind of an ideal design for a "12V" panel that's connected to a pwm controller. The panel has 36 cells and has a max power point voltage of about 17.6V at room temperature. Exposing the panel to the sun causes panel temperature rise and voltage drops. Your panel has a Vmp of 16.5V. It's a bit low for pwm use. But, as I mentioned before, your battery voltage is also low. They may compensate each other out. The alternative is connecting the panels in series (this raises operating voltage to 3 times Vmp) and using MPPT.

Regarding my proposed test to determine if your panels will work with a pwm controller. It sounds like you want to go with mppt. I don't want to write up a detailed test procedure if you are not going to do the test. Let me know if you're serious and will then provide further details. To answer your question, you're looking for the battery voltage when current starts to decreases. In pwm mode, charging current is about 3% lower than the panel's short circuit current (Isc = 5.1A max). At max irradiance, the pwm current should be 0.97 * 3 * 5.1A = 14.8A. You will see something less due to lower irradiance. If irradiance remains constant, this current will stay constant; even as battery voltage increases due to charging. There comes a point in time where charging current no longer is constant, but starts decreasing. The system has lost its voltage headroom. Of interest, what's the battery voltage when current starts to decrease.

Cal

No! BUT thanks you, I will go with an mppt controller, just dont have the smarts to figure out how to test them, sometimes once I get into it I can figure things out but this stuff is a bit too complex for me yet, I am a firm believer in the KISS method.

In thinking about things a bit I may consider reducing the battery bank and get a more complete charge into the two remaining batteries, makes sense to do it that way, I am going to spend a bit more time looking into it but to get the initial set up going I am going to go with the morning star 15 mppt, and then do some load calculations and bug you guys some more.

BB.

Re: Camper with a twist

From August of 2011:

kevinhenrycalgary wrote: »

It works great. Not a single glitch. If memory serves me correct I think I had it pumping in 11+ amps to the battery in optimum test conditions. In practical use I have a hard time drawing the battery bank down below 90% and it only needs to be putting in a couple of amps. Seems I can park in the shade for a week and it still charges.

-Bill

Shadowcatcher

Re: Camper with a twist

I am in a some what similar situation, a camper/teardrop trailer. I have a 185W panel on the roof but high voltage so I used a Morningstart MPPT. I also have a Unisolar flex panel that put out about 40V but found a STECA PMW that will handle 47V input voltage. Part of this equation is also conservation, i.e. using LED lights.

gobox

Re: Camper with a twist

I have been trying to get my head around how to get my batteries fully charged using two separate systems. If there are two sets of panels and two controllers going into one bank of batteries how does that work? Does the battery bank go through a full cycle charge and how do the controllers do it if they can??
Is it doable to have this work?

Cariboocoot

Re: Camper with a twist

There really isn't much problem from connecting two charge controllers to the same battery bank. It works best if they're the same controller of course. So long as the Voltage set points are the same (or at least very close) and the Absorb times "agree" it works.

Morningstar (and some others) makes a dual charge controller that does the opposite: charges two separate battery banks from one array.

frankson

Re: Camper with a twist

vtmaps wrote: »

For the portable array, you may be able to get away without a combiner box (one or two series strings needs no combiner with fuses). The higher voltage of a series string will help with the voltage drop. You will need to educate yourself about the dangers of connecting and disconnecting those panels during daylight hours.

I understand caution around live wires, but was wondering if there's anything else you might also be referring to here,
too, for instance is there any possible equipment damage risk to panels or chargers, etc., with frequently connecting &
disconnecting panels while they are producing elec in daylight sun?

Cariboocoot

Re: Camper with a twist

frankson wrote: »

I understand caution around live wires, but was wondering if there's anything else you might also be referring to here,
too, for instance is there any possible equipment damage risk to panels or chargers, etc., with frequently connecting &
disconnecting panels while they are producing elec in daylight sun?

Yes. DC likes to arc. Pulling any kind of connector under load can cause an arc that will burn the connector, increasing its resistance or even damaging it to the point of needing replacement. Fortunately it's easy to cover panels which will drop their output to levels low enough to prevent problems. For battery connections you really do want a proper DC disconnect; even with the inverter "off" it can draw power, especially on "cold" start up (caps need to energize).

And while we're at it, when disconnecting charge controllers the panels should be removed first then the batteries. Reconnect the other way.