The Electrodacus SBMS thread (SBMS0, DSSR50, etc)

[BiduleOhm]

His more detailed argument is that off grid users aren’t generally array limited and the benefits of his system are in the reduced fusing costs, safety of lower voltages, and reliability of being able to stick with solid state controllers with life-spans >30 years. MPPT requires the use of electrolytic capacitors which crap out after about 10 years give or take based on thermal cycles etc.

Pretty much everything in that is false. I am array limited (and money limited, panels may be relatively cheap but they aren't free, like thousands of $/€ not free, not negligeable IMHO...) and I'm probably not the only one. Also if you start including ecology in the equation it's clearly not a good idea to do that (more panels to compensate higher losses = more resources used).

And again, totally ignoring the wires needed for the low voltage high amperage. Copper is really expensive and often forgotten in the budgets.

Reduced fusing costs? I'd really like to know how if you can give more details please. Physics says it'll be the contrary, or else you're cutting corners and you don't really protect things correctly.

MPPT don't require electrolytics, you can do it without them, it's just a bit more expensive and you need more time spent on the design, but totally do-able. But even without that, electrolytic can last far more than 10 years, you just need the right type and use high quality ones (of course if you use the cheapest you can find in a back alley in China they'll not last long).

It’s still possible to use MPPT chargers with the SBMS, so long as they have remote on off switches that can be controlled by his SBMS so if using MPPT is important to your use case, go for it. In thirty years if your amortized costs are lower than Dacian’s system, you can call him up and give him an I told you so. I doubt he will care.

BMS main purpose isn't to be a controller, it's to be a safety device when the other things crap out. If it can only control the thing that crapped out and can't cut power itself then it's pretty much useless. For example: mosfets in your SCC have short-circuited, battery is in over voltage, what this BMS will do? nothing; it'll try to turn the SCC off but it can't so the battery will continue charging until the cells are destroyed.

Here you go. Measured comparison 9 years ago on a 130W panel (8/4/2011, Santa Barbara, Ca). I used a switch to connect panel either to charge controller or directly to lead acid battery. The battery had a constant load to keep battery voltage from rising (battery voltage range: 12.2 to 12.3V). It appears around noon time MPPT output degrades due to temperature? Ambient temps are around 22C.

MPPT: total amp hours = 63.8
direct: total amp hours = 58.6

MPPT gain = 8.8%

Thank you one million times, finally some real world data

So around 9 % which on my previous estimated system would translate to 1440 W of PV (16000 * 0.09) needed if the no MPPT solution was chosen. At 30 cts/W that's 430 USD which gives you a nice MPPT or two. And again when you add the costs of wires, fuses, etc... you'll save hundreds if not thousands so yeah, I don't see how it's more economical than using MPPTs.

Unfortunately Dacus is giving out false information to hype his product. 10 year life span of capacitors in a MPPT controller??? WTF? My CC is still going strong after 14 years of constant use. Clearly, MPPT has a performance gain over a direct connection, even in summer.

Yep, I tried to give him a fair chance actually, but got too much BS for me to take him seriously anymore.

While I think there are blindspots in his argument, and I think he tends to get laser focused on one particular use-case or factor and not fully acknowledge or consider alternative use-cases/design goals, I definitely don't feel that he is acting in bad faith or trying to hype his product. He is a very disarming and straightforward guy, and strikes me as very honest, even when I disagree with him or feel he is overlooking something.

I'm sorry but someone asked him and he ignored it, I asked him and again he avoided answering the question. And yes, conveniently ignoring everything else in the system while only talking about the SCC isn't a proper way to design a solar system.

I may be wrong (actually I really hope I am for anyone buying from him) but I personally don't trust him anymore. No hate or anything, just I don't trust him, that's all.

All I wanted to do is warn people here to not trust everything you're told and check the numbers and the general sense of something before buying; and then if it's good for you then no problem, go for it

 

[childcarepro]

There's a big reason pretty much everyone use MPPTs, and it's not in the table which compares only SCCs because it concerns the wires. When you start talking bigger installs than RVs (i.e. longer wires and/or higher powers) it's not practical and especially not economical to use PV arrays with the same voltage as the battery as then you need incredibly thick wires to have the same losses than a higher voltage installation with MPPTs.

I don't even need to do the math to know the cost of 300 A wires (or busbars more realistically, especially to be under 3 % losses) will be astronomical and would pay for a lot of MPPT controllers.

It's even more important in my case where I don't have infinite real estate to put panels to compensate higher losses of a low voltage system (and even then you need to pay for the panels too...)

I agree DSSRs are not for all use cases. I'm not even sure it's the best fit for ME, as I'm heavily invested in the Victron ecosystem. I may just use the SBMS as a BMS; I'm just a bit worried the Victron 100/50 + 24V 60-cell panels won't drive electrons into my battery approaching its 100% SOC (29.2V, 3.65V/cell) when there isn't enough sun. I could series connect, but partial shading kills a LOT of solar production.

What bothered me was how you casually accused someone of deceit based on 2 data points: ONE math error (copied and pasted into multiple boxes) and because he sells a product. The world is an ugly place because of people's opinions spreading and being conflated as fact, and I believe we as citizens can do better at treating other people with more respect.

 

[BiduleOhm]

What bothered me was how you casually accused someone of deceit based on 2 data points: ONE math error (copied and pasted into multiple boxes) and because he sells a product. The world is an ugly place because of people's opinions spreading and being conflated as fact, and I believe we as citizens can do better at treating other people with more respect.

I'm sorry for that, but I've seen that a lot in the past and there's actually a bit more than 2 data points but my main goal was to inform members there's some misleading info, so they better be be careful. It was probably poorly executed but I tend to be very direct when I like or don't like something so yeah, sorry if I have offended someone, that was not the goal.

 

[childcarepro]

This thread has taken on a religious fervor which is why I avoided joining this site.

You sound like you've never heard of the internet! You know EVERY disagreement on the forums gets zealous on both sides!

Here you go. Measured comparison 9 years ago on a 130W panel (8/4/2011, Santa Barbara, Ca). I used a switch to connect panel either to charge controller or directly to lead acid battery. The battery had a constant load to keep battery voltage from rising (battery voltage range: 12.2 to 12.3V). It appears around noon time MPPT output degrades due to temperature? Ambient temps are around 22C.

MPPT: total amp hours = 63.8
direct: total amp hours = 58.6

MPPT gain = 8.8%

1. Thank you for submitting data; beautiful chart, and data is always handy to have! A single 130W panel, how many cells?
2. My understanding is lead acid chemistry resists incoming electrons as it approaches full charge and requires a larger voltage differential to overcome, whereas LiFePO4 will accept electrons at equal voltage until full. Dacian specifically mentions LiFePO4 batteries, so your comparison may not be an apples-to-apples with Dacian's?

Unfortunately Dacus is giving out false information to hype his product. 10 year life span of capacitors in a MPPT controller??? WTF? My CC is still going strong after 14 years of constant use. Clearly, MPPT has a performance gain over a direct connection, even in summer.

1. It's great that you had a good experience with your capacitors, but Dacian is using ratings provided by Panasonic for theirs. Clearly they don't all fail immediately at the end of their life cycle! Just so you know, if I had a horse in this race, it's MPPT. I already BOUGHT a Victron SmartSolar and an all-Victron setup, just considering the possibility of simplifying my setup with a DSSR. But dang if some people aren't just trashing the poor guy!
2. The fact that there are unscrupulous people out there doesn't mean everyone you disagree with is a scoundrel. Have you seen his prices? He's not getting rich off these. (I appreciate his pricing.) He's simply making a case for those whose use cases are similar enough to his.

BTW, I'd better buy my SBMS quick before prices go up... seems everything @Will Prowse reviews gets jacked up in price!

 

[BiduleOhm]

2. My understanding is lead acid chemistry resists incoming electrons as it approaches full charge and requires a larger voltage differential to overcome, whereas LiFePO4 will accept electrons at equal voltage until full. Dacian specifically mentions LiFePO4 batteries, so your comparison may not be an apples-to-apples with Dacian's?

That's a good point. I wonder if we would be able to see a difference between lead and LFP batteries.

1. It's great that you had a good experience with your capacitors, but Dacian is using ratings provided by Panasonic for theirs.

Is there a link to the datasheet in question?

 

[Cal]

You sound like you've never heard of the internet! You know EVERY disagreement on the forums gets zealous on both sides!



1. Thank you for submitting data; beautiful chart, and data is always handy to have! A single 130W panel, how many cells?
2. My understanding is lead acid chemistry resists incoming electrons as it approaches full charge and requires a larger voltage differential to overcome, whereas LiFePO4 will accept electrons at equal voltage until full. Dacian specifically mentions LiFePO4 batteries, so your comparison may not be an apples-to-apples with Dacian's?


1. It's great that you had a good experience with your capacitors, but Dacian is using ratings provided by Panasonic for theirs. Clearly they don't all fail immediately at the end of their life cycle! Just so you know, if I had a horse in this race, it's MPPT. I already BOUGHT a Victron SmartSolar and an all-Victron setup, just considering the possibility of simplifying my setup with a DSSR. But dang if some people aren't just trashing the poor guy!
2. The fact that there are unscrupulous people out there doesn't mean everyone you disagree with is a scoundrel. Have you seen his prices? He's not getting rich off these. (I appreciate his pricing.) He's simply making a case for those whose use cases are similar enough to his.

BTW, I'd better buy my SBMS quick before prices go up... seems everything @Will Prowse reviews gets jacked up in price!

I just have a single 130W panel on my motor home, which at that time cost about $400 to $500. At that time MPPT was a very smart choice! My MH roof has a lot going on, and more than one panel is difficult to fit. The Kyocera panel contains 36 cells.



As I mentioned above, the lead acid battery remained around 12.2 to 12.3V during the entire test. I didn't want the battery to go into absorption mode. Current is throttled back during absorption. I don't see why this test results can't be applied to LiFePO4. LiFePO4 charges at 13.3V, while I tested at 12.3V. Charging at 13.3V reduces MPPT gain over direct by 1V/12.3V = 8%.

8.8% / 1.08 = 8.1%

The 8.8% gain at 12.3V reduces to 8.1% when charging LiFePO4 at 13.3V.

Regarding capacitors. I have a 60 year old oscilloscope that still works! It has similar caps that you and Dacian say should fail in 10 years. I understand the concept of capacitor ripple current and what it does to electrolytic caps. It's an industry norm to derate capacitor ripple current to a safe level. Scare tactics shouldn't be use in promoting a product.

Regarding "But dang if some people aren't just trashing the poor guy!" Not trashing him. Just responding to a request for MPPT vs. Direct solar measurements as well as the comment about a 10 year cap life span.

I actually got involved in this thread/discussion because I may purchase one of his units. I'm looking for info. No hype please!

 

[childcarepro]

I just have a single 130W panel on my motor home, which at that time cost about $400 to $500. At that time MPPT was a very smart choice! My MH roof has a lot going on, and more than one panel is difficult to fit. The Kyocera panel contains 36 cells.

The 8.8% gain at 12.3V reduces to 8.1% when charging LiFePO4 at 13.3V.

You'll find a LOT of us are still trying to figure this out, as Dacian's approach is unfamiliar to most of us. If I understand his table correctly (see previous posts), without voltage matching using MPPT or PWM, whatever the current and voltage the panel is at based on conditions, that current gets passed along at the battery's voltage (~13.5V for LiFePO4). Your 36 cell 12V panel is better suited for MPPT than for direct connection, as more voltage drop/loss of power would occur compared to a 30-cell 12V panel which would be better matched to the 13.3-13.5V of the LiFePO4.

My situation is different, as I've ordered 24V 60-cell, not 72-cell panels, so I worry about MPPT not having enough of a voltage differential for my 24V LiFePO4 battery. But I'm resisting series connecting because it's nearly impossible to get some shading when camping (unless you're camping in the desert, and that's not my scene).

Regarding capacitors. I have a 60 year old oscilloscope that still works! It has similar caps that you and Dacian say should fail in 10 years. I understand the concept of capacitor ripple current and what it does to electrolytic caps. It's an industry norm to derate capacitor ripple current to a safe level. Scare tactics shouldn't be use in promoting a product.

I don't imagine your oscilloscope is under the same kind of stress or even temperatures that capacitors in MPPT's are.

I'm sure 99% of people on this forum are nerds and therefore spreadsheet-makers. I make a sheet with two options for almost every major decision – tech purchase or business – you weigh out the pros and cons, calculate cost savings, expenses, etc. Don't tell me you don't (NERD)! IMO he's doing exactly what WE ALL DO to compare two options (sometimes I make 3 scenarios, worst, realistic, and best case; I know, I need professional help). BUT since you suspect his motives, you interpret his innocent little spreadsheet as scare tactics to make sales. You know what REAL scam artists use to sell stuff? Not spreadsheets, they use testimonials. (Not everyone who uses testimonials is a scam artist, but ALL scam artists use testimonials.)

Our POV colors how we see the world, and being 100% certain is no guarantee of being right: everything – from sports to religion to politics to brands – has diametrically opposed positions/adherents, with both sides equally certain they're right; and clearly at least one group has to be wrong!

I remind you, the DSSR is a $37 piece of kit, not a $250 MPPT controller he's "hawking." Of course I don't know if he was making the DSSR 5 yrs ago; they may have been integrated into the SBMS, which was, and still is, a great deal as a BMS IMO.

I actually got involved in this thread/discussion because I may purchase one of his units. I'm looking for info. No hype please!

Same here, just looking for information. If you read my other posts, you'll see I'm NOT decided on my Victron SmartSolar 100/50 or switching to the DSR. But I couldn't stand idly by while someone was being insulted without being given a chance to defend himself.

 

[Cal]

But I couldn't stand idly by while someone was being insulted without being given a chance to defend himself.

Let him speak for himself. Please ask him to join the conversation. I've got a few questions for him that need an answer before purchasing his unit.

Your 60-cell panel sounds a bit sketchy for a 26V battery. Do you have a full spec for that panel? I'll do some calculations.

 

[childcarepro]

Let him speak for himself. Please ask him to join the conversation. I've got a few questions for him that need an answer before purchasing his unit.

I don't know him, never talked to him. Watched a couple of videos including this famous MPPT vs direct charging.

Your 60-cell panel sounds a bit sketchy for a 26V battery. Do you have a full spec for that panel? I'll do some calculations.

I know, right? I thought I'd learned enough, and I thought I was being pretty clever order 24V panels for a 24V battery rather than having to series connect 12V panels. I knew there had to be a voltage differential and that there IS higher voltage than nominal on panels, but I had no idea when I was ordering all my gear it wouldn't quite be enough except in full sun.

EDIT: direct link didn't work. Download link is on this page: https://www.newpowa.com/products/newpowa-200w-24v-monocrystalline-high-efficiency-solar-panel

 

[Cal]

Take a look at the I-V curves. The 75C curve starts dropping around 25V. For sure MPPT won't work well at 75C. A direct connection will have trouble at 75C also. You should be OK at 50C with MPPT.

 

[LB3]

Thanks for your detailed response. Since posting that, my project has progressed and evolved a bit.

Most importantly, I've moved from trying to control/display things directly from the SBMS to creating a data link between the SBMS and an Arduino. That gives me far more flexibility (and pins to tie into). It solves both the LED and the external display questions, and opens up a whole world of possibilities. Had to write my own code from scratch but I have it all working.

I also obtained a suitably-sized heatsink and some thermal-transfer adhesive tape I'll be using to attach it. Hopefully that works out as I intend.

Project has been progressing slowly as I work through snags re: my custom enclosure, and my bus bars. Progress is being made... I'm also very distracted with another geeky but non-solar project, perhaps of interest to people here but very much off-topic. :D

Explain your Arduino project more please? I’ve been envisioning using an Arduino to read the SBMS to manage loads. Ie turn the thermostat up when the battery gets low or wake a bitcoin miner when there is excess power, etc...

 

[childcarepro]

Totally missed this post earlier.

This right here ^ is how I feel as well (though as I already mentioned in the other thread, I think you are misunderstanding the point he makes about 60 cell panels)

Series connecting 60 cell panels WILL give MPPT SCCs have plenty of voltage to work with, but it would have two negatives:
1. Partial shade on either panel would wipe out power from both (and that's a whole lot of surface area!)
2. Plus the heat loss from the voltage conversion (in a shading video from AltE store, output wattage only 89% of input)

Personally, I think he may be overstating the case to a degree, and I'm skeptical that the whole rest of the industry got it wrong, but he does make a compelling argument and the logic seems mostly sound (with a few caveats). Its a complicated subject, and I plan to do my best to keep an open mind until more experiments or at least experiences begin to trickle in, or until I pony up the cash to do my own testing. I do want him to be right because it would be cheap and easy to go with DSSR20's instead of MPPT, and I like the simplicity.

I didn't take it as saying everyone's wrong, but rather in the right use case (cheap 60 cell panels + LiFePO4 batteries), his solution is better from a $/W long-term cost amortization standpoint.

The biggest outstanding questions for me is how would the two compare over the full range of seasons and conditions, and in partial shade conditions.

Agreed; I think this is an important question to answer, as a LOT of people are setting up vans with solar, so it's not the narrow niche it used to be. I think a LOT of people would be grateful if someone bit the bullet and did some A/B comparisons (hello, @Will Prowse?):

- 30 cell 12V panels + 4S LiFePO4 batteries OR 60 cell 12V panels + 8S LiFePO4 batteries
- MPPT SCC vs SBMS0 + DSSR
- cold panels vs hot panels (Will's done this for other videos)
- full sun vs overcast/off angle sun

I think 36/72 cell panels would so heavily favor MPPT, it wouldn't even be interesting.

Any takers? Ahem. @Will Prowse immediately comes to mind, with his history of excellence, know-how, and existing testing setups?

 

[childcarepro]

Your 60-cell panel sounds a bit sketchy for a 26V battery.

Thanks for looking at that for me. But someone on the Victron forums dug up section 3.3 in their SmartSolar manual: minimum Vbatt + 1V, so 29.2V + 1, and minimum number of cells: 72. So much for the best laid plans... My options are not to completely rethink my panels (it's a 25' motorhome, I don't think I can fit 72 cell panels), series connect them (don't like); or going with direct charging and losing my Victron charge monitoring.

Also, I found a great video on 60 (20V nominal) vs 72 cell (24V nominal) panels that sheds a LOT of light on the differences, and she specifically states you can't charge a 24V battery with a 60 cell panel because they're 20V nominal panels, not 24V.

 

[LB3]

Let him speak for himself. Please ask him to join the conversation. I've got a few questions for him that need an answer before purchasing his unit.

Go join his forum. It’s much more active than it used to be.

 

[Dzl]

Totally missed this post earlier.


Series connecting 60 cell panels WILL give MPPT SCCs have plenty of voltage to work with, but it would have two negatives:
1. Partial shade on either panel would wipe out power from both (and that's a whole lot of surface area!)
2. Plus the heat loss from the voltage conversion (in a shading video from AltE store, output wattage only 89% of input)

1. Not exactly wipe out, but I get your point, shade has a disproportionate affect on output. Bypass diodes help with that, still trying to understand the particulars.
2. I'm not sure this is worth worrying about too much. We are probably talking about at most 1-2% difference. Here are a couple example efficiency curves (from Outback and Morningstar, two top tier companies). Doubling voltage (from 17v to 34v with a 12v battery) made a difference of <1% with the Outback controller. Multiplying the voltage by 500% made about a 2% difference with the Morningstar. Victron does not release an efficiency curve, but I've read its pretty flat and in the mid 90's. For optimum performance Victron recommends a Vmp of roughly 3x the battery bank voltage.

My options are not to completely rethink my panels (it's a 25' motorhome, I don't think I can fit 72 cell panels), series connect them (don't like); or going with direct charging and losing my Victron charge monitoring.

I think you already understand this but the wording of the above makes me want to double check. Your options are not Parallel (planned) and Series (what you don't want to do). With 6 panels you have the option of 6P, 2S3P, 3S2P, 6S. With your current controller you really just have one option 2S3P which will give you 3 parallel strings of 2, and pretty close to optimal based on Victron's advice. You lose some shade tolerance but retain some.

Alternatively you could go with 3 x DSSR20's for your 6P config (well technically 2P x 3). Cost roughly $120, but you could resell or return the ~$325 Smartsolar, and possibly the GX and Smart Shunt as well (since the SBMS0 has its own Shunts, SOC, and energy in/out monitoring) which could save you considerably more and give you the 6P array you want. Personally I wouldn't be inclined to rework my whole system for 6P (and partial shade optimization is a big consideration for me), but it does seem like that is where your priorities are at, so it may be worth considering.

 

[BiduleOhm]

As I mentioned above, the lead acid battery remained around 12.2 to 12.3V during the entire test. I didn't want the battery to go into absorption mode. Current is throttled back during absorption. I don't see why this test results can't be applied to LiFePO4. LiFePO4 charges at 13.3V, while I tested at 12.3V. Charging at 13.3V reduces MPPT gain over direct by 1V/12.3V = 8%.

8.8% / 1.08 = 8.1%

The 8.8% gain at 12.3V reduces to 8.1% when charging LiFePO4 at 13.3V.

Ok, so I agree, you can transpose that to LFP

I don't imagine your oscilloscope is under the same kind of stress or even temperatures that capacitors in MPPT's are.

Actually they are probably in similar ambient temps if not worse (60 years means it most probably use vacuum tubes which get very very hot). They also used older tech caps who didn't last as long as the ones we can get now. Secrets (well not really secrets actually... ^^) to make something durable in electronics are: over spec and use top tier brands.

I think 36/72 cell panels would so heavily favor MPPT, it wouldn't even be interesting.

But that's the point, you don't use low voltages when you use a MPPT because you can use higher ones, it would make no sense otherwise. Of course if you compare a direct connection with a MPPT where you'd keep the panels in parallel instead of putting them in series the MPPT will have more losses, but that would be like putting a V8 in a Smart... not really useful.

 

[sremick]

Explain your Arduino project more please? I’ve been envisioning using an Arduino to read the SBMS to manage loads. Ie turn the thermostat up when the battery gets low or wake a bitcoin miner when there is excess power, etc...

The SBMS will be inside of an enclosure. I'd like a secondary display to show some key data that's visible even when the enclosure is closed. I'll also have an RGB LED that indicates various statuses that's visible from a distance (and in the dark). I can also incorporate other data from other sources... such as temp probes. The temp will then trigger a variable-speed fan, that won't come on at all until it hits a certain temp then will ramp up as the temp gets higher. Alternatively, I have a heating pad that kick in if things get too cold... that'll be handled by PID code.

I have other ideas spinning in my head. One is showing the ideal direction to point the solar panels based upon GPS location and digital compass. Another is showing a weather forecast, but that might be getting ridiculous. The Arduino makes all this possible, however.

The keystone for this was creating a data link between the Arduino and the SBMS... if I couldn't figure that out, nothing else was going to happen. In my prototype setup after a lot of trial and error I was able to figure this out... in some ways, it was nowhere near as complicated as Damian suggests in the manual with that complex formula/function, but there were still a lot of little nuances to sort out, such as running the serial link through a magneto-isolator due to different voltage levels/sources between the two devices, and some timing/buffering issues. Damian also failed to mention that there's actually one more byte in the data packet than he says there is, but I was able to figure that one out after not too long when I dumped the raw stream and noticed the pretty shifting pattern and was like, "I bet there's an EOL in there too". :D Ultimately I was able to get it all working and could separate out every bit of data from the SBMS serial data packet, so I could then use whichever ones I wanted on the Arduino and do whatever I want with them.

This is all still very much in the early stages, but is going to happen. The prototype is an ugly monster on my workbench that really needs to be torn apart and redone... I'm waiting to do that when my e-ink displays arrive (wanted to go with that to reduce battery drain for the external display). Once I settle on all the inputs and outputs, I can decide exactly which Arduino variant to go with for the core... it's dependent on how many I/O lines I need, and the ultimate code size. I have a few on hand already to play with. But I really need to sort all this out before I nail down the final layout of components on the mounting board inside the enclosure... can't do that until I know all the things I need to mount and how big they are. I'm aiming to pack things tight as this is a portable kit and so size matters. The size of the enclosure is now set in stone and I'm already going to have to do some work-arounds to accommodate the location of the handles, which I failed to account for.

 

[Cal]

Actually they are probably in similar ambient temps if not worse (60 years means it most probably use vacuum tubes which get very very hot). They also used older tech caps who didn't last as long as the ones we can get now. Secrets (well not really secrets actually... ^^) to make something durable in electronics are: over spec and use top tier brands.

This Phillips scope actually had transistors, mounted in sockets. Back in the '70's wife and I decided to check out Europe. Moved to Germany and got a job with Bosch working on fuel injection (Jetronic). Bosch sold off their old scopes to employees and I purchased one. Later on I took it back to the US with me. The scope actually got retired this year when I purchased a Siglent. It was about time for an upgrade!

 

[BiduleOhm]

Ah ok it's more 50 than 60 years, I was really surprised while reading the first part of the sentence as transistors were pretty rare and expensive in the 60's ^^

That's pretty cool; far more durable than most of today's crappy consumer stuff ?

 

[childcarepro]

I think you already understand this but the wording of the above makes me want to double check. Your options are not Parallel (planned) and Series (what you don't want to do). With 6 panels you have the option of 6P, 2S3P, 3S2P, 6S. With your current controller you really just have one option 2S3P which will give you 3 parallel strings of 2, and pretty close to optimal based on Victron's advice. You lose some shade tolerance but retain some.

I was actually going to parallel connect pairs of 2 panels, then connect the 3 parallel pairs using my factory Winnebago Zamp solar 3 input combiner which wires them in parallel, for a net 6P connection. That was before I found out 1) my 60 cell panels are nominal 20V, not 24V, and 2) therefore not recommended (unless in series) for the SmartSolar. If I keep the SmartSolar and Victron monitoring, I would have to do 2S3P and lose some shade tolerance. I would have to avoid trees like the plague (or COVID-19) when we camp!

Alternatively you could go with 3 x DSSR20's for your 6P config (well technically 2P x 3). Cost roughly $120, but you could resell or return the ~$325 Smartsolar, and possibly the GX and Smart Shunt as well (since the SBMS0 has its own Shunts, SOC, and energy in/out monitoring) which could save you considerably more and give you the 6P array you want. Personally I wouldn't be inclined to rework my whole system for 6P (and partial shade optimization is a big consideration for me), but it does seem like that is where your priorities are at, so it may be worth considering.

This is the other option I was considering, allowing me to stick with my original plan of 6P. But then I lose the Victron solar charge monitoring, but I would have Electrodacus's monitoring, which isn't quite as slick. Though better than a LOT of other solutions, I would venture.