“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
John Weiland wrote:Excellent!.....Thank you David B. Seems strange to me that they still wouldn't put the little plus and minus signs on the connectors....
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Gerry Parent wrote:
John Weiland wrote:Excellent!.....Thank you David B. Seems strange to me that they still wouldn't put the little plus and minus signs on the connectors....
If you look closely at your picture John, you can see a black + & - symbols just above where the wires exit the box.
.............
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
John Weiland wrote:
Now, with the panel laying on a cart angled mostly straight up and given a slightly overcast day at high noon (sunny, but a mix of wildfire smoke and high cloud haze), the open circuit voltage measured at 61.8 and the open circuit amps measured 5.8-5.9. More detailed specs are given in the screenshot below. Michael Q., am I correct in seeing on that spec sheet that the Vmp is ~54.7? Is there some way that I can set up my measuring approach to determine Vmp myself?
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
John Weiland wrote:Thanks for additional input Michael and David.... I'm sure learning a lot here. As I may have noted earlier, part of my interest in this project is to just get my head around EVs and battery power storage. I suppose like many, when it comes to drive systems like cars, trucks, and farm equipment, I tend to think in terms of gas, diesel, and internal combustion engines. This project is giving me a lot of insights into not only EV's but eventually power for the home that is off-grid or reduced-grid.
So I'm hoping I guessed right in purchasing a charge controller, a photo of which is shown below. It weighs 1.6 kg and seems to have the blessings of many of the reviewers, which I know is no guarantee, but may help. The specs *seem* to allow for the type of set-up that I'm looking for, but again as a newbie I'm grateful for the advice being provided here and hope it may help others on similar projects. The controller was a bit spendy, but if it's a good one it should pay for itself down the road. Additionally I feel (?) I may have gotten a decent deal on the panel (used) at $100....but again, time will tell.
Charging the 36V bank: Drawing on analogy here, when I'm concerned about my riding mower or tractor charging the starter battery properly, I often look at the voltage at the terminals when the engine is running vs. when the engine is off. I think when the charging system is working property, the 12V battery being charged registers about 14+V at the poles (charging) and something in the 13V range when not charging. Does this sound correct? By analogy, in order to see what the 36V bank in the golf cart *normally* charges at using the grid-based charger that came with the cart (I think it puts out 18A during charging), could I not also use a multimeter to see what the voltage is at the two main connection points within the cart? Would this allow me to see the necessary charging voltage and then, in some way, be able to see if the PV panel would meet that, even if the amps being pushed by the panel are lower than what the main (120V grid-based) charger normally provides?
Again, much thanks for the help being provided through this discussion!
David Baillie wrote:.... The problem lies in the working voltage of your solar panel. It's working voltage is lower than the absorption charging voltage of a lead acid battery. To get the best use out of that charge controller you would need say two panels in series to give you closer to 72volts coming from the array.
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
John Weiland wrote:
David Baillie wrote:.... The problem lies in the working voltage of your solar panel. It's working voltage is lower than the absorption charging voltage of a lead acid battery. To get the best use out of that charge controller you would need say two panels in series to give you closer to 72volts coming from the array.
Wow....I'm really swimming in uncharted waters for my knowledge base here. So David, would that Buck Boost charger that you linked rectify my problem and allow me still to use the single panel that I currently have? If so, I would just leave the Victron in the original packaging and return it, using the savings to get the proper charging module.
Also, am I thinking correctly that the absorption voltage is different if the batteries are, say, in a 50-60% charge state vs a 90 - 95% charge state? Because for our use pattern which is mostly very short distance/time and low load conditions and only used a few days per week, I'm wondering if it would still charge okay in good sunlight when the bank is near full, but require the wall charger if it gets to a lower state of charge. I realize much of this conceptualization is quite vague and subject to many variables. As I have not installed the panel yet, it's still possible that I could get a second panel and have them mounted in a manner in the yard to just provide a stationary charging station as an alternative. Thanks for this and any additional advice you can provide.
David Baillie wrote: So... if you are using a lead acid battery the absorb charge voltage is higher than the rated voltage of the battery. roughly speaking if its a sealed lead acid absorb voltage for a 36 volt bank would be 42.6. Your victron would do bulk charging but without absorb you would sulphate your batteries and they would have a shorter life. the charge controller I listed is a type that is being used in a lot of carts. I do not have first hand experience with that particular unit but it would be your best bet for a single panel cart mounted setup.
Michael Qulek wrote:
1) Could you please post the specs/pics of the batteries in this golf-cart?
Michael Qulek wrote:
Flooded lead-acid likes to be charged best at ~ 1/8th of C. Since C is 225Ah, then it wants 225Ah/8 = 28.1A of charging current. Your panel is 327W, so it's output at about 42V (bulk) is 327/42V = 7.8A. Don't confuse the bulk setting with the actual bulk voltage. With controller set to 44.5V max, it will start charging a depleted battery at about 40-41V. As it reaches full charge, the voltage will go up to 44.5V (you set that). As the charging cycle approaches full, the controller tapers off the amps as it reaches max voltage. So, you are likely to see max amps at a somewhat lower voltage of around 40V or so. The MPPT controls all that.
2) So, your single panel is really only capable of putting out ~8A, whereas, your battery wants 28A. Four of those panels, maybe wired 2S2P, would provide the charge density you need.
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
Eugene Kenny wrote:I see I'm late to the party. At any rate, glad to see your system functioning.
Just a few tidbits to add, if I may;
I've been completely off-grid for 4 years now. My solar storage bank is basically 48 Volts nominal (4x110Ah 12V deep cycle FLA's (flooded lead acid) batteries, all connected in series. I have six 12V (nominal), 100W rated panels, also connected in series for an average open Voc of 133.8V (each PV produces, on average, 22.3Voc each. I use a Victron Blue 150-35 controller. (the same controller you initially purchased).
I see your panel is rated at 64.9Voc (open circuit voltage). So, connecting two of these identical panels in series should yield approx. 129.9Voc, which is well under your controller's 150v maximun input voltage. Obviously, connecting three (or more) like PVs would exceed the controller's 150V maximum input voltage - and may even damage it.
The Victron 150-35 would've been OK with your 36v (nominal) system, but much better with two, series connected PVs. BTW, the Victron controller has 4 charging stages - Bulk, Absorb, Float and Equalize. It is also compatible with Lithium Ion.
Lastly, testing a PV's maximum current output (Isc=Short Circuit), is self explanatory; Shade the PV from direct sunlight first, then Just connect a short 12" 10 gauge jumper wire across both PV's output terminals. Once connected, uncover the PV and aim it directly at the sun. Use a DC capable clamp meter ( https://www.amazon.com/AstroAI-Multimeter-Auto-ranging-Resistance-Capacitance/dp/B08MTCMWLB/ref=sr_1_3?keywords=dc%2Bclamp%2Bmeter&qid=1694491992&sr=8-3&th=1 ) around the jumper wire. A must-have tool when tinkering with electrons!
David Baillie wrote:[...... When you have a cold day and the panels have not yet started producing the initial voltage easily goes over the VOC. Most MPPT Controllers can shed extra amps but not extra voltage. ....
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
David Baillie wrote:Eugene, A good rule of thumb for max working voltage on controllers is panel string VOCx1.25. When you have a cold day and the panels have not yet started producing the initial voltage easily goes over the VOC. Most MPPT Controllers can shed extra amps but not extra voltage.
David Baillie wrote:I have replaced 4 controllers for people for that very reason, all in winter. Its less of an issue with the new high voltage controllers but the 150 and 135 volt units are susceptible to it. Blue smoke of death is not good...
Cheers, David
John Weiland wrote:
David Baillie wrote:[...... When you have a cold day and the panels have not yet started producing the initial voltage easily goes over the VOC. Most MPPT Controllers can shed extra amps but not extra voltage. ....
David, more excellent information. Can you elaborate on this effect? Why, between a cold or warm weather situation with the panels receiving the same solar input, would the cold panels crank up voltage without producing amps (if I'm interpreting this phenomenon correctly)? Again, forgive me my rudimentary understanding of the forces involved, but without amps, what contributes to controller burn-up without the involvement of amperage? Thanks!....
Trust me reading a manual is not typical! I am convinced half of my skill set in solar design is due to actually reading the manuals and following what they suggest. Having said that there is a lot of missing info that can only come from talking to their tech support people....Eugene Kenny wrote:
David Baillie wrote:Eugene, A good rule of thumb for max working voltage on controllers is panel string VOCx1.25. When you have a cold day and the panels have not yet started producing the initial voltage easily goes over the VOC. Most MPPT Controllers can shed extra amps but not extra voltage.
Yes, I am aware of the voltage variations of PVs, based on changing ambient temperatures. My 5 YO panels have noticeably aged, losing at least 0.03-0.06% output (the typical voltage increase when cold, for fresh panels).
David Baillie wrote:I have replaced 4 controllers for people for that very reason, all in winter. Its less of an issue with the new high voltage controllers but the 150 and 135 volt units are susceptible to it. Blue smoke of death is not good...
Cheers, David
Odd, I've not heard of anyone around here (or via the web) that has negligently toasted a Victron controller. The Victron Owner's manual is crystal-clear regarding maximum voltage inputs - that said, I suspect most owners do read the manual.
Christ is Risen!
Mark Miner wrote:This is getting off in the weeds, but the panel voltage as a function of temperature is a published coefficient on the datasheet, so you can accurately predict your peak open circuit voltage in cold. This is a better method than a rule of thumb, and I still put a little margin on the result for safety.
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
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