Recommend solar controller for LiFePO4 batteries

john61ct

Active member
Yes as stated many times, that will help for shading, and with Victron's pricing model that does not add much cost, just a bit more space & wiring pain.
 

w15p

2019 144 HR 4x4
Wouldn't connecting panels in series (say 3 100W) with a single MPPT controller (eg a 75VDC/15A Victron) give the same shading benefits (all modern panels I've looked at have bypass diodes)?

TIA.
 

Airtime

Well-known member
I have to say, more often than not, unless you are completely out in the open, there is partial shade. We go to forests often and there are trees all over and the shadows hit the panels differently all day. Even if you park in a clearing, you only have a few hours of full sun when the sun is directly overhead. Otherwise trees shade some of the panels. The vehicle also has a tall Air Conditioner on top and it shades some of the panels at various times of the day. I guess it depends where you go. Even if only one corner of a panel is shaded, it basically produces nothing.
My understanding is that the shadow of even one leaf will shut down a panel. I guess there are some situations where one panel is 100% clear and the other partially shaded, but seems rare. I'd say that over the past couple decades, my situation has been >95% either
1) At the coast, or driving, zero shade
2) In the forest, whether the redwoods or say an Oregon State Park - almost 100% shade

If I add the desert SW travel I want to add in the future--likely zero shade. Exceptions may be the period when a shadow is creeping across the van as the sun moves.

I guess I can experiment with it both ways, any MPPT solar controller I pick would work either way for my 2-3 panel array. Just re-wire on the roof and try it out.
 

gltrimble

2017 170 4x4
In my opinion wiring your solar panels in series is the better choice 99% of the time including:

Full sun
Full shade
Overcast skies
Fog
Rain
Early morning
Late evening
Variable conditions

Wiring your panels in Parallel will be of benefit 1% of the time when:

One panel is shaded and the remaining panels see full sun.
Your spouse, child, or favorite pet is sunbathing on one of your solar panels.



 
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markxengineering

Active member
Total of six Renogy Eclipse 100 watt panels with a tolerance of -5/+1000 watts. And this was a cloudy day at 9 AM.
Am I the only one confused here? How can a 100 watt panel output 1000 watts? Is there a datasheet showing that tolerance?
 

Zundfolge

Always learning...
Am I the only one confused here? How can a 100 watt panel output 1000 watts? Is there a datasheet showing that tolerance?
I'm just as confused. No math that I know of allows that picture to be true...

Also, that's not a screenshot, it looks like a picture of a phone off of a website. What's going on here?
 
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john61ct

Active member
Partial shading really knocks out most of the panel output.

Yes one leaf, even road dust can make a huge difference.

A 1:1 ratio will give each panel its own optimized MPPT adjustment.
 

gltrimble

2017 170 4x4
I'm just as confused. No math that I know of allows that picture to be true...

Also, that's not a screenshot, it looks like a picture of a phone off of a website. What's going on here?

One day early ....April 1. And yes the screenshot is from the Victron website.
 

jvvjvv

2008 V6 Dodge 2500 Agile
John..........campground closed........Coronavirus.........so ran the gen set 1 hour and then drove 70 miles or so. SOC constantly rising. When it got to 100% the controller went to 0 output. So it’s "trying" to do the right thing. ??? Never reset, stays in float.

Anyway, the 100/30 smart Victron will be here tomorrow........good old amazon.........I now understand the 2 controller set up, but already wired for one controller.......(within my pay scale to R n R the controller)......no way for me to get on roof and butcher the installers wiring. Maybe a future project???


As far as panel output in general............watching my readout pretty much daily for 3 years or so, highest I ever saw was 83 watts, with a 100 watt panel. Midday summer Florida.
 

HarryN

Well-known member
John..........campground closed........Coronavirus.........so ran the gen set 1 hour and then drove 70 miles or so. SOC constantly rising. When it got to 100% the controller went to 0 output. So it’s "trying" to do the right thing. ??? Never reset, stays in float.

Anyway, the 100/30 smart Victron will be here tomorrow........good old amazon.........I now understand the 2 controller set up, but already wired for one controller.......(within my pay scale to R n R the controller)......no way for me to get on roof and butcher the installers wiring. Maybe a future project???


As far as panel output in general............watching my readout pretty much daily for 3 years or so, highest I ever saw was 83 watts, with a 100 watt panel. Midday summer Florida.
That is a very reasonable result. Keep in mind that the panel "official rating" is based on solar conditions in the high desert during the winter.

Since you have the 100/30 coming and are wiring changes are difficult, install what you have and make the best of it. There are plenty of similar installations out there.

1 - 2 hrs of gen a day plus the solar will cover a lot of ground.
 

john61ct

Active member
With a lead bank, do the ICE charging first before insolation starts, Bulk stage up to say 80-85% SoC, wasteful to go longer.

Then the solar is ideal for finishing up, takes 5-6 hours because the bank CAR is plummeting.

LFP all that's not relevant, can refill in 60-90min if you have the amps
 

john61ct

Active member
And yes actual panel output is rarely close to the theoretical rating.

That's why a 75/15 is actually fine for 260-300W @12Vnom

Note that just tilting the angle to follow the sun can double the daily yield.
 

robzr

Member
makes up for the say 15% or so lost conversion efficiency compared to more modern MPPT models.
Is this true? Seems incredibly high for what is effectively an intelligent buck converter. Kisae advertises > 98% MPPT tracking for the DMT-1230/DMT-1250 series; this site says most modern MPPTs are around 93-97% (in the context of home systems). FWIW the Kisae DMT is also a buck/boost, so it can take 10.5v on the input and boost it.. this also lets it take ~12.0 on the input from the alternator and boost it to 14v+ to charge LiFePO4. Super happy with my Kisae DMT-1250 if it's not clear already.

Rob
 

robzr

Member
No, never superior as a general technology.

But a wonderful overall design functionality implementation will beat a crappy one, independent of that factor.

Bogart happens to make great stuff that overrides the lower efficiency.

The original founder Ralph Hiesey moved on years ago, and the new lot stopped innovating.
My understanding is that MPPT is effectively a PWM (high frequency switch) with an inductor to store the change that a straight PWM controller effectively wastes when it's pulsed off. I can certainly imagine that a high quality PWM could, in some conditions, exceed a low quality MPPT design, but it seems like the general view is that MPPT is a newer, more refined and superior technology. Really curious what you think makes straight PWM superior?

Rob
 

john61ct

Active member
Apples to apples.

Stating the actual measured difference between PWM and MPPT, both being good quality state of the art dedicated solar chargers.

So 10-15% advantage from MPPT generally.

Is that what is surprising to you?

The next part, is that because Bogart created such a fantastic SoC meter, and uses that to control the output of the two add-on SCs, so that they very accurately get a lead bank to true 100% SoC

as per their mfg endAmps spec rather than guessing based on AHT or something else

which is **very** rare, both for shore chargers and SCs

never yet implemented for DCDC

My point is that that critical advantage IMO makes up for that (specific) loss of efficiency.
 

klompen

Member
Very interesting thread (much of it over my head), but I read and absorb what I can because I plan to switch to LFPO once my 200Ah AGM has lived it's full life.

The discussion about the downside of maintaining high SOC has me wondering whether I should continue my practice of always plugging in when my rig is parked. My Sportsmobile is equipped with a Magnum 2000 inverter/Converter. My impression was that it was designed to maintain the battery properly, but now you have me wondering. Have I overbought this, or misunderstood what you guys said?
 

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