Hey everyone, I need a quick sanity check on a small setup I’m putting together for a VW Multivan.
The van has a factory 12V 100Ah flooded lead-acid battery (resting around 12.6V). I want to use a portable EcoFlow 110W panel (Voc 21.8V, Vmp 18.4V, native MC4 connectors) paired with a SmartSolar 75/15. The customer also insists on a physical BMV-712 monitor inside the van.
The tech support at the shop is refusing to approve the order. They claim this low-voltage panel will cause the MPPT to constantly cut out or fail to start. Their logic is that since the battery sits at 12.6V, the MPPT needs 17.6V to trigger (Vbat + 5V). They argue that once the panel goes under load and drops to its working Vmp of 18.4V, any heat degradation or slight cloud cover will drop the voltage below the threshold and stop the charging. They are pushing me hard to buy a cheap PWM controller instead.
But isn’t the Vbat + 5V condition only for the initial morning startup? My understanding of the Victron algorithm is that once it fires up, the running requirement drops to Vbat + 1V (so around 13.6V). With a Vmp of 18.4V, shouldn’t I have plenty of buffer even on a hot day or when the battery gets to 14.4V absorption?
Am I misunderstanding how the Victron MPPT algorithm works, or is the shop support wrong? I really want to stick with the MPPT to get the most out of this small 110W panel.
While not well explained by the supplier they are not wrong.
When the panel gets hot from being in the sun it’s voltage will drop and disappointment will be expressed. (In other words the sticker on the panel is being very optimistic) Real world conditions will alter that information.
If you can try and convince them to buy two to run in series and get a higher voltage to ensure consistent charging there will be much happier customers.
If you cannot get them to buy 2 you are definitely better off with a PWM. (You will actually get a higher yeild as an FYI)
Thanks for the great insight
Since the client strictly wants a single-panel setup due to limited storage space in the Multivan, running two smaller panels in series is unfortunately out of the question.
But what if I drop the EcoFlow and look for a different single 100W-120W panel that has a higher native voltage? For example, a panel with a Vmp of around 21V to 22V and Voc around 25V to 26V (like some 36-cell or 40-cell heavy-duty panels).
If a panel like that drops about 15% in the summer heat, a 21V Vmp would slide down to around 17.8V. That should still keep it comfortably above the 15.4V minimum running threshold needed for the MPPT during the 14.4V absorption phase, right?
Would switching to a higher-voltage single panel solve the heat issue and make the SmartSolar 75/15 a reliable choice again?
Alright, after looking at what is actually available in stock, I am down to two final paths. I want to lay them out here and get your final opinion on what would be the simplest, most efficient, and most reliable setup for the client.
Option 1: The 2x 60W panels in series with the SmartSolar MPPT 75/15. The efficiency would be great, but I just realized a huge hardware catch. These specific 60W EcoFlow panels are the newer Type-C version, meaning they output via a DC5521 barrel jack instead of native MC4. Running them in series would require buying clunky DC5521-to-MC4 adapters for both panels, chaining them together, and having the client deal with delicate barrel plugs on the wet grass or dirt every day. It sounds like a massive mechanical failure point for a portable camper setup.
Option 2: The EcoFlow 160W folding panel paired with the Victron 20A PWM controller (this is what the shop lady ended up putting in my cart). The massive advantage here is that the EcoFlow 160W has native, heavy-duty weatherproof MC4 connectors right out of the box, so it is 100% plug-and-play with the extension cable I already have, no extra adapters or fragile plugs needed.
I am trying to balance the Victron ecosystem benefits (since the client already has the BMV-712 smart monitor in the cart) against the pure practical simplicity and ruggedness of the wiring.
If you were building this for a customer who just wants something robust and easy to use, which combo would you choose as the best compromise between reliability, ease of installation, and efficiency?
Just for some additional insight, im using a 75/15 together with a foldable 100W panel (Polaroid SP100 35.6Vmp) to keep both starter and house battery charged in my 4x4. The setup is a few years old by now, the panel was folded and unfolded many times and also twisted/warped over time due to the sun/heat. Ive never seen over 80W from that panel, even when new. Nowadays its peak is at about 60W. Part of that will be age, but also that its almost never placed at a good angle to the sun.
As for the connection, i dont like MC4 on mobile panels since you either need to deal with their locking tabs regularly until they break off, or you remove them straight away, which both leads to a major benefit of the connector being disabled. I like to use XT60-S for mobile panels
Nice VOC. I agree those foldable ones don’t age well and never perform. Convinience aside.
The mc4s are a pain unless you have the tool for them they are like 1 or 2 $ so include one in the kit if there aren’t any. Xt60 is definitely easier and easy to check their condition.
I can’t say for sure as i don’t know the client. And ultimately you have to live with your decision. For me on paper though with voltage of panel closer to the battery voltage the pwm wins every time. And in this case simplicity of set up and use for the client.
Thank you so much to both of you gentlemen for your invaluable advice and real-world experience. I truly appreciate your time, and it helped me immensely to confidently finalize this setup for the client.
I am going to add here, it depends on the pwm charger as not all are suitable for lithium (or programmable) and how cheap it is and also the battery that is being managed by the bms.
I can see why the 75/15 mppt would be preferable as it is more easily programmable for lithium
