Forum Discussion
412 Replies
smkettner wrote:
jrnymn7 wrote:
Putting 45a into a 215Ah bank, it will remain in bulk until ~80% soc. A 50-80% would take about an hour and a half; voltage slowly rising from about 13v to 14.8v over that time period. Putting 45a into a 430Ah bank, it would remain in bulk until well past 80% soc, voltage slowly rising all the while. The only way to get to 14.8v rather quickly would be to use a very high C-rate, like 75a on a 215Ah bank.
You assume you get 45 amps at daybreak... you don't. Amps ramp up slowly with the sun and often can be at 14.8 before max output is even available.
To really get max, the battery needs to be a bit oversize or you need cloud cover to about 11am. Then with sudden clearing and full sun you will get max power into a low battery.
Hard pressed sometimes to even get down to 50% because each day you are closer to 95% to 98%+. So the 50-80 becomes 68-98 and you hit that 80% fairly quick.
I'm not assuming anything, but rather planning for a worse case scenario. As you pointed out, if charging didn't begin until near noon, AND if that was following a couple of bad days, resulting in a deeply discharged bank, then yes, a 50% cycle is quite possible.
Nevertheless, even a 70-80% on a 430Ah bank would take an hour, using 45 amps; voltage starting out somewhere between 13 and 14.8v, and ending still short of the setpoint. So I fail to see how 14.8v can be considered relevant for sizing.- These are 80Ah AGM 24HR3000 at my disposal:
- Rough pricing looks like it is better to go with a single 45-60A controller. Part of this exercise is get solar installed and the other is to educate myself along the way. I appreciate the input given whether I acknowledge your post our not.
The trailer will be a supplemental power source for my truck camper and also provide power to itself. I haven't decided if the interconnect between the two will be AC or DC at this point but the idea is to reduce generator use primarily to air conditioner operation. I will be experimenting with various capacities of like ganged batteries once installed to see how much reserve I can build each day verses discharge and expect this to be an ongoing project that changes as I learn, our needs change or I find a good deal... jrnymn7 wrote:
Putting 45a into a 215Ah bank, it will remain in bulk until ~80% soc. A 50-80% would take about an hour and a half; voltage slowly rising from about 13v to 14.8v over that time period. Putting 45a into a 430Ah bank, it would remain in bulk until well past 80% soc, voltage slowly rising all the while. The only way to get to 14.8v rather quickly would be to use a very high C-rate, like 75a on a 215Ah bank.
You assume you get 45 amps at daybreak... you don't. Amps ramp up slowly with the sun and often can be at 14.8 before max output is even available.
To really get max, the battery needs to be a bit oversize or you need cloud cover to about 11am. Then with sudden clearing and full sun you will get max power into a low battery.
Hard pressed sometimes to even get down to 50% because each day you are closer to 95% to 98%+. So the 50-80 becomes 68-98 and you hit that 80% fairly quick.CA Traveler wrote:
jrnymn7 wrote:
The unquoted part of what I posted was about the MS MPPT45 and it's derating at 45A as per the specs. At 45A it's not going to take hours to get to bulk charging.
CA T... said,
"No need to use 13V as the controller will ramp up discharged batteries to 14.8V for bulk charging."
Depending on the C-rate, it could take hours to get to 14.8v. (Better safe, than sorry).
Correct MS is better safe than sorry by protecting the controller against more than 45A output and over paneling.
Less quality controllers well.....
I was not zero-ing in on one particular controller, necessarily. Just using 13v as a realistic denominator for figuring out possible max amp output. I used it when showing the possible output of the eco-worthy, as well. It applies to sizing all mppt controllers, seeing as it's about Output Power vs. Vbatt.
Putting 45a into a 215Ah bank, it will remain in bulk until ~80% soc. A 50-80% would take about an hour and a half; voltage slowly rising from about 13v to 14.8v over that time period. Putting 45a into a 430Ah bank, it would remain in bulk until well past 80% soc, voltage slowly rising all the while. The only way to get to 14.8v rather quickly would be to use a very high C-rate, like 75a on a 215Ah bank.
So, to safely size any mppt controller, one must consider Max Power and Min Vbatt (+R). In the Op's case, 544w / 13v = 42a, regardless of which controller he decides to go with. It so happens, the Morningstar 45 will work, but two eco-worthy 20's may not, in full sun. And going with 3 eco-w's creates more problems than it solves; not to mention little, if any, cost savings, when all is said and done.- Bedlam,
You would be miles ahead to get one quality controller like the Morningstar TS45. Saw a listing for $369. No issues with balance, etc. You will have more than the difference between three EWs and one TS in connectors and wiring not to mention conservation of mounting space and simplicity. jrnymn7 wrote:
The unquoted part of what I posted was about the MS MPPT45 and it's derating at 45A as per the specs. At 45A it's not going to take hours to get to bulk charging.
CA T... said,
"No need to use 13V as the controller will ramp up discharged batteries to 14.8V for bulk charging."
Depending on the C-rate, it could take hours to get to 14.8v. (Better safe, than sorry).
Correct MS is better safe than sorry by protecting the controller against more than 45A output and over paneling.
Less quality controllers well.....- CA T... said,
"No need to use 13V as the controller will ramp up discharged batteries to 14.8V for bulk charging."
Depending on the C-rate, it could take hours to get to 14.8v. (Better safe, than sorry). - More than 2 parallel panels should be individually fused. Accepted practice is panel wiring to a combiner box with fuses and heavier wire to the controller.
- Since 250W frame panels are available for $200 have you considered that option?
