Hi. I just bought a Renogy DC-DC charger (it is the 50 amp charger) with MPPT. It says that the max PV for this charger is 25 volts. My pannels are 24 vots, but is says in the back of my solar pannels 29.4 volts (VPM 29.4v). Will this charger be able to charge my batteries with my pannels? Or it will NOT work, or even f**k my new charger... I don't want to burn (or else) my new charger... Tks. to you guys.
Renogy DC-DC charger with MPPT
- Thread starter Camginger
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sunshine_eggo
Happy Breffast!
It will not work and may f**k your new charger.
Voc must be under 25V AND there must be sufficient margin for cold temperatures. This means that the panel Voc must be under 22V depending on your climate.
I suspect you have 60 cell panels with a Voc around 35-36V.
Voc must be under 25V AND there must be sufficient margin for cold temperatures. This means that the panel Voc must be under 22V depending on your climate.
I suspect you have 60 cell panels with a Voc around 35-36V.
rodrick
Free energy enthusiast
You want to use the voc numbers on the panels adjusted for lowest recorded temperatures fore your area
voltage will go even higher in cold temperatures
look at the victron line of scc they have dropped in price and are better quality than most of the Chinese models
voltage will go even higher in cold temperatures
look at the victron line of scc they have dropped in price and are better quality than most of the Chinese models
rodrick
Free energy enthusiast
you need to decide how your panel layout is going to be done like how many series or parallel ect then size the scc with known specs including adjustments for temperature, midnight and victron have a site for scc sizing which will help you
mikefitz
Solar Wizard
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- May 28, 2020
- Messages
- 3,072
Check which version of Renogy DCC50 you have. The latest version can accept panel volts up to 50 volts.
This is the version currently sold in the UK.
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sunshine_eggo
Happy Breffast!
yodamota
Solar Enthusiast
looks like in North america, the 50vdc VOC is not a thing. All I see are 25VOC.
Tks for your answer. What does
''scc'' means?
Partimewages
Solar Addict
Solar Charge Controller
Tks.
Tomthumb62
Solar Wizard
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- Sep 25, 2022
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- 1,871
I finally rid myself of most of my Renogy gear, I think you dodged a bullet there. All my renogy gear gave me headaches.
I second a Victron Smartsolar charge controller. For example their 100/30 model can accept up to 100V input from the panels and output a max of 30A. Price is now $123 in the states, it was $209 when I bought it in September. Perhaps someone with Canadian connections can help you find a dealer there.
Victron also has DC-DC chargers. Here’sa good video of a guy who started with a Renogy DC-DC charger and then switched to a Victron one:
I second a Victron Smartsolar charge controller. For example their 100/30 model can accept up to 100V input from the panels and output a max of 30A. Price is now $123 in the states, it was $209 when I bought it in September. Perhaps someone with Canadian connections can help you find a dealer there.
Victron also has DC-DC chargers. Here’sa good video of a guy who started with a Renogy DC-DC charger and then switched to a Victron one:
2Big2B
Free Wheeler
Hey Eggo, maybe you can advise me, as I just can't seem to find the answer to what should be a common question.
What panel voltage is appropriate, coupled with a charge controller of course, that I should use for charging a "24v" LifePo4 battery pack? This is a rehash of my quest in using my existing Power wheelchair DIY (8S 12V 100AH x 2, in series), and 24v inverters. I probably really want a 400w portable 48v or 36v panel, like a Anker 625 100w 48v folding panel, that I can use with a cheap charge controller. - But they are too pricey, so I am investigating the cheapest, most practical other panel options. Try finding Used panels on ebay, with shipping. No such thing - all used are local p/u only.
I am handicapped with mobility issues, a southern exposure but a backyard that maybe I can make work. Its a tall order. I am basically trying to make a DIY Solar power station w/o investing in a fancy controller/battery unit that I don't need. I have most of it, I just need the right panel and controller to modestly get me through a week or two of offline grid.
If the LifePo4 charging voltage is 29.2v, 100% resting is 27.2v, with a minimum @ 25.6v, what single panel voltage should I be shopping for. Naturally I want compact, efficient and cheap as possible.
If total wattage is a secondary consideration, is there a single panel/cheap controller combo solution for what I want, or is that a fantasy?
For a "12v"LifePo4 battery pack? 12.8v - 14.6v ?
For a "24v" LifePo4 battery pack? 25.6v - 29.2 ?
Is there a sweet spot setting on the controller, say 80% SOC?
Can I simply find any panel combo to output > 30v and set high and low SOC params in the controller?
That is my quest!
I can't seem to find that discussion anywhere.
So far all I see are discussions of 12v and 24v, which doesn't seem to fit the LiFePO4 SOC profiles.
Perhaps my fundemental understanding of VOC stuff is lacking. Investigating.
It is probably in this Victron Configuration and settings user manual page that holds an answer...
OhOh, also, what if I charge @ 14.v on the poles of one of the 12v batteries in series, with a balancer to bleed balance both batteries, or is that just a stupid question?
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sunshine_eggo
Happy Breffast!
A good rule of thumb for any system is array Vmp > 1.5X system voltage, so for 24V, you need at least 36Vmp. The reason you want to shoot higher than peak voltage for Vmp is solar cells get very hot, and that heat reduces their operating voltage, so you need additional voltage margin to ensure you can get to peak battery voltage.
Panel Voc is about 25 higher than Vmp. Voc is what you use to make sure you don't blow up your controller. Easiest way is with the NEC table:
If your record low is 0°F, you multiply the array STC Voc by 1.18, and that's your temperature adjusted Voc. That value MUST be under the Voc limits of the controller.
No. Trying to target SoC based on voltage is nearly impossible.
36V
Pretty much. If you acquired 2X 100W panels from amazon, those tend to be "12V" panels with a Vmp in the 17-20V range, so two in series would get you there (I wouldn't sweat 34 vs. 36V in this example).
They do, pretty much perfectly. You can't get hung up on the slight voltage differences. LFP are essentially "drop-in" replacements for lead acid with a few additional needs that should be met by the LFP BMS.
Yes, that would work, but it would likely take forever to get the second battery charged. It would be far more practical to move the charger to the other battery
Charge voltages aren't mandatory, and they can be problematic if set too high. 14.6/29.2V are likely to trigger over voltage protection due to a single cell being out of balance. It's often easier to pick a lower absorption voltage and run for longer. You can get fully charged at 13.8V/27.6V with a 2 hour absorption in most cases.
If charging with a generator, you want to go for the higher voltages for more efficient generator use. If you're charging from solar, and you have the time, the lower voltage may be more practical/convenient.
Panel Voc is about 25 higher than Vmp. Voc is what you use to make sure you don't blow up your controller. Easiest way is with the NEC table:
If your record low is 0°F, you multiply the array STC Voc by 1.18, and that's your temperature adjusted Voc. That value MUST be under the Voc limits of the controller.
No. Trying to target SoC based on voltage is nearly impossible.
36V
Pretty much. If you acquired 2X 100W panels from amazon, those tend to be "12V" panels with a Vmp in the 17-20V range, so two in series would get you there (I wouldn't sweat 34 vs. 36V in this example).
They do, pretty much perfectly. You can't get hung up on the slight voltage differences. LFP are essentially "drop-in" replacements for lead acid with a few additional needs that should be met by the LFP BMS.
Yes, that would work, but it would likely take forever to get the second battery charged. It would be far more practical to move the charger to the other battery
Charge voltages aren't mandatory, and they can be problematic if set too high. 14.6/29.2V are likely to trigger over voltage protection due to a single cell being out of balance. It's often easier to pick a lower absorption voltage and run for longer. You can get fully charged at 13.8V/27.6V with a 2 hour absorption in most cases.
If charging with a generator, you want to go for the higher voltages for more efficient generator use. If you're charging from solar, and you have the time, the lower voltage may be more practical/convenient.
2Big2B
Free Wheeler
Thank you!
The technical aspects can be confusing. To get to where I am trying to get to there are a lot of confusing restraints and false notions.
I see what you mean about expecting to use voltage to determine SOC on LFP, given its flat curve, compared to flooded lead acid. That is a given. But I don't have any practical knowledge or full understanding of how two 12v panels in series can accomodate charging an LFP that charges at 29.2v.
Yet " If you acquired 2X 100W panels from amazon, those tend to be "12V" panels with a Vmp in the 17-20V range, so two in series would get you there". I am still trying to wrap my head around that.
Are you saying that with the right charge controller I could get away with a pair of matched 12v panels?
Or I can mimimalize to a single 36v panel and a simple charge controller?
That's what I really want or a foldup portable... Simple. In Case of Emergency, Break Glass... Otherwise it stays stowed away in a closet.
sunshine_eggo
Happy Breffast!
Yep.
"12V" panels are panels one needs to charge a 12V battery with a cheap PWM controller. Note the quotes. It's a label applied for this reason, not because the panel in any way puts out just 12V.
"12V" panels tend to have a Voc in the 20-24V range and a Vmp in the 17-20V range. This is just how it is.
By putting two "12V" panels in series, you would get a Vmp of 34-40V and a Voc of 40-48V - Some will fall outside these values, but this covers the vast majority.
There's really no such thing as a "36V" panel. Yes, you'll find panels that output 36Vmp, but those are actually "24V" panels - again, note the quotes.
"24V" panels (36Vmp/45Voc) tend to be heavy as shit. I have a bunch of 285W panels that are a solid 50# each. Newer models are a little lighter, but none are light.
Given your physical limitations, I recommend that you acquire two quality flexible panels and construct some PVC frames for them. They will be very lightweight, and since they aren't a permanent install, they should last much longer than a typical installation on an RV or van as those live in the sun their whole lives.
Cheap Dual Flex Panel Mobile/Tilting Stand
Here’s a super lightweight and cheap adjustable stand design that I use for 100w flex panel pairs. Each unit costs
diysolarforum.com
