Have at the moment 2 x 200W Renogy solar panels installed in parallel with a 100/30 MPPT. Iâve decided to add one more of the same, so in total 3 x 200W. My question is do I need to change the (already made) parallel connection of the 2 x 200W solar panel to a single connection and then connect those to the third solar panel in parallel or can/should I keep the parallel connection and connect the third panel in parallel? Just attached a drawing of the panel positioning and the cables to understand my messy question a bit better. I am not even sure that my calculations are right.
All advice would be appreciated.
Hi. Your pic on the left is the correct way. Isc is getting up there, but should make it under the 35A limit of your 100/30.
Alternatively you could put them all in series and remain within the 100/ limit. Selective shade tolerance not so good doing that.
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Hi JonC, thanks for your answer.
On the left drawing I will lose 2,22A because of my 100/30 MPPTâŠat least if I understood well all topics and websites Iâve red before. Am I right?
And I donât get it either how to fuse this PV array/MPPT combo on my Lynx Distributor DC because the smallest mega fuse is 60A. Would a 60A fuse be okay? 
Your 30A mppt is rated into Battery V. Letâs say 14.4V under charge, so a max of ~430W. No matter how you wire the panels. Itâs quite normal to âoverpanelâ like this, the mppt may flatline for more of the day, and will perform better in poorer light.
Fuses are to protect the wires. If you really canât find a smaller fuse then max out the wire size between the mppt and Lynx. Spec sheet for that mppt sez the terminals can handle 16mm2(AWG6).
I red about it that there is no smaller than 60A mega fuse exist. And Lynx Distributor compatible only with mega fuses and no midi fuses.
My MPPT is approx 20 cm away from the Lynx Distributor and connected with 16mm2 cables because - as you mentioned it as well - 16mm2 is the max cable size that the 100/30 can handle. Will it be safe with a 16mm2 cable?
It seems a 100/30 MPPT and a Lynx Distributor DC is not the best combo thanks for the smallest 60A fuse and a 16mm2 size limitations of the cable. Should I buy a 100/50 instead? Can a 25mm2 cable fit into it? Would it be a better/SAFER combo in this case?
The 100/50 model has 16mm2 wire capacity too. That suggests that your unit should be fine with a 60A fuse. Google 40A mega fuses, they should be readily available, just maybe not Victron branded.
Oh. So that does not make sense to switch to 100/50 just because of the limited wire size butâŠ
âŠI think that 100/30 is not compatible with Lynx Distributor DC because in its specifications it says minimum 35A, maximum 40A. However the 100/50 has 60A.
So if I donât find a 35A or 40A mega fuse nowhere, it is better to switch to the 100/50 MPPT.
Opinion?
40A Mega fuses definitely do exist
Another option is to bolt a MRBF fuse terminal to the end of the lynx.
When connecting more than 2 panels in parallel, it is important to check the datasheet for the panels reverse-current limit.
- One time the forward current as reverse current is always possible (2 panels parallel)
- Two times the forward current as reverse current - most panels do not support this, hence you shouldnât parallel more than 2 for safety reasons. (It is possible to use external diodes to savely operate more than 3 of those panels in parallel)
The datasheet of the 200W Renogy solar Iâve found doesnât mention this, so you should check with the Manufacturer or use external protection diodes in any case.
The reverse current through a defective String may be the sum of all other strings - which may set the defective string on fire, if its reverse current rating is exceeded:
Thanks Alan, Iâve already found and ordered one 40A from Hella. Found it on autodoc app.
Did you see my drawings? My setup is on the left drawing. 2 panels are in parallel (both of them have their own 15A Renogy fuses on the +), then the 3rd one is connected in a separate parallel to the other two. Like a main parallel and a âsub-parallelâ connection. I am not sure I understand what youâre saying. I thought I somewhat understand what I am doing until I red your post.
This Explorist guy on YouTube explained it pretty clearly that if the short circuit current on the (entireâ:thinking:) array is greater than the âmaximum series fuse ratingâ listed on the panelâs sticker then MC4 fuses must be used on the + right before the cable splitter. With connecting 2 x 200W panels in parallel exaclty this has happened so I put 2 x 1 Renogy 15A diodes on the + of both. The 3rd panel didnât get any diodes because it is a 1 x 200W lonely panel. Should the last panel also get a diode? If so, why? Being that one alone it is not greater than the âmaximum series fuse ratingâ. Now I am totally confusedâŠ
wire the panels in series not parallel if they look same direction and have now shadows.
This will help the MPPT to start with low sun light due to higher voltage and reduce wasted energy due to less amps.
Else put blocking diodes in front of each panel.
But this will reduce voltage by appr. 1,5V. Delaware you risk to damage your weakest panel by back current.
Itâs on the top of my RV but this is a totally separate system from my RVâs own system.
This additional setup is with:
- 3x200W solar panels
- 15A MC4 diodes
- solar panel DC isolator
- 100/30 MPPT
- Lynx Distributor DC
- smart shunt
- battery isolator
- LiTime 280Ah battery (no bluetooth)
- 3000W, but 1500W continuous power pure sine wave inverter.
I want to remove this addidional system when/if I sell my RV in the future.
So for sure some part of the panel will be in the shadows often.
I donât want series if itâs not a âmustâ.
The one and only reason I would build these panels in series it would be only the safety.
Cable length, actual junction points or if that looks like 2 paralleled setups paralleled again dont have any physical impact.
If you tie up all the â+â and all the â-â in whatever meaning, itâs just a parallelâd setup.
I like to confuse people 
No, just kidding. The issue iâm talking about is a safety thing. When you parallel panels, situations may occur, where the current of all paralleled strings could flow reverse through a single (defective) string.
This may be a potential risk of fire and can be avoided by using protection diodes that only allow the current to flow in forward direction through any string.
However, Iâve read that you plan to add fuses to the strings as well. If you choose them to be close to the panel current, that will also surpress any excess reverse current here and effectively protect the wiring from overloads due to doubled current from panel 2 and 3.
The fuse would still allow MORE than a single panels rated forward current (obvisously it needs to). If you now would have connected multiple panels in series, this may lead to the issue that one defective panel could cause the destruction of the panels behind, until the fuse blows - but since you have a single-panel-string setup there, that is not the case.
So, ideal the fuse would be in the range âmaximum forward currentâ < fuse < âmaximum reverse currentâ in order to protect all the remaining panels like a dedicated string diode would do.
As mentioned, your datasheet does not outline the acceptable reverse current of the panel.
Hereâs an example of a panel that could savely be used in a â3-Parallel-String-Setupâ without any external protection - because the two other strings could produce a reverse current of 28A max, while the panel supports a reverse current of 30A.
If you would do a 4-Parallel-String-Setup here, the reverse current could be above 30A, hence a fuse somewhere between 15 and 30A per string is required then. (or a diode)
This is a very often neglected figure, because it only is relevant for 3+ parallel and only starts to become an issue if single panels start malfunctioning. So, systems may run for 10, 15 years without issues, and the other day, light up like a christmas tree 
Hi,
Assuming your system is 12V, you should (with three 200W panels) be looking at a 50A MPPT solar charge controller. The 30A controller will be limiting the maximum power by quite a bit. For your application, putting all three panels in parallel (as in your LHS drawing) would be the best option. The panels are diode protected so a fuse for each panel is not essential but is recommended.
You will lose a lot more than 2.22 A. The three panels will be capable of supplying around 50A to your battery but the MPPT controller will limit the current to a maximum of 30A.
Connected as a test just as shown on the RIGHT picture. It seems I am losing more power than gaining. The battery drains quicly as hell. Not sure what to do if I want to keep the setup of the right drawing for some time for testing it. What the hell is happening? Something drains so fast my lithium battery without ANY load connected. 
The right hand configuration is useless and renders the new panel ineffective.
Can you explain please why?
Your two existing panels are in series and will produce around 40.2V at the maximum power point. This is above the max voltage the third panel can produce so the third panel will contribute nothing to the overall power output. The left hand configuration should be used.
Also, looking at the screen shot, it seems there is only one panel connected to the MPPT controller.