| Author |
Message |
dangraham
Newbie
Joined: 07/10/2020
Location: ThailandPosts: 17 |
| Posted: 09:15am 15 Oct 2020 |
 Copy link to clipboard |
 Print this post |
|
I am in the process of reviewing and building the (150V 45A MPPT - roll your own) I feel this is a good way to follow the vast amount of information posted by other members. It will also allow me to qualify the information and have a viable test bed for experimentation with changes. This will eventually be used in another 48V application.
My primary requirement is for a similar controller but operating at higher voltages. I am still trying to establish the best converter topology to use, Buck, Boost or Buck-Boost etc and would love to know your input on the various considerations.
My current main power installation is as follows:
40* 180Ah LifePo4 battery bank ~120V – 148V
20Kw DC Generator, running 110A @ 148V
15Kw Selectronic Inverter
There is also an 8* 180Ah battery bank for the 24V power system & and a soon to be replaced dual 12V FLA power system for two engines & generator starting.
The system is currently working very well, I can run on battery all day happy as Larry, and the generator runs for ~1 Hour to charge the battery. Run times obviously depending on load, if using air con I may see the generator run two times in a 24Hr average. This is certainly better than the previous setup where the diesel generator had to be running continuously if air conditioner was being used, running a 20Kw diesel generator to supply a light load is not economical at all, now the generator runs at 80% load for 1 hour and it’s done.
I have recently purchased a load of solar panels, house installation is nearly completed, next will be this boat installation. I can fit 8* 335W panels on the roof of the boat, they will be horizontal, I need to feed this into the 148V battery.
Individual Panel Specifications:
Pmax 335W
Imp 8.91A
Vmp 37.60V
Isc 9.62A
Voc 46.20V
Initially I was considering 4S2P the panels and using the buck-boost topology, this would give the following:
Pmax 2,680W
Imp 17.82A
Vmp 150.40V
Isc 18.24A
Voc 184.80V
With this configuration the Vmp is very close to the nominal battery voltage, the thought behind using the buck-boost controller would be to take advantage of the situation when array voltage is lower than battery voltage, though the driving and inverted output may need more consideration. Panels being in a horizontal position on a boat that is constantly being moved by the wind means they will mostly be operating in sub-optimal conditions.
My other option is 8S1P giving the following parameters:
Pmax 2,680W
Imp 8.91A
Vmp 300.80V
Isc 9.62A
Voc 369.60V
This would allow for the use of the buck only topology but obviously much higher voltages to take into consideration.
I am not firm on what topology to use at this stage and would welcome your thoughts. The 8S1P parameters are within most commercial grid tie inverter DC specifications, most run up to 450V-500V
Please chip-in with your thoughts and areas of concern with both options, and what alterations to consider modifying the Poida 45A MPPT to operate at, input max Voc ~400V max I 10A, and outputs in the range of 120v-150V, 25A
Thanks in advance. |
| |
Solar Mike
Guru
Joined: 08/02/2015
Location: New ZealandPosts: 1122 |
| Posted: 12:06pm 15 Oct 2020 |
Copy link to clipboard |
Print this post |
|
High dc voltages and salt spray make for a less than ideal situation ??
Any circuit boards will require quite large track spacings and be properly sealed against moisture if you want to run 400V
Your PV combination 4S2P @150.4V is a pretty good match for a straight PWM controller, at a cell discharge level of 3.0V X 40 = 120, they will rapidly move to 3.3 x 40 = 132 and when 98% charged at 3.46 x 40 =138V. You may gain an extra 200W after losses moving to a Sepic buck, boost, but is it worth it.
On a boat having 2 parallel sets of PV maybe better suited to rejecting losses caused by sun shadow as you would have on a 8S combination.
Cheers
Mike |
| |
Warpspeed
Guru
Joined: 09/08/2007
Location: AustraliaPosts: 4406 |
| Posted: 08:31pm 15 Oct 2020 |
Copy link to clipboard |
Print this post |
|
Oh lot's of different aspects to think about here.
For a marine application, a set of series connected panels will always be current limited by the shading of only part of one panel. If you have a mast, sails, or whatever, some partial shading at times will be unavoidable. I am pretty sure that is going to be a severe limitation that will reduce the available current during periods of full direct sun.
These are going to be pretty hard shadows too, its not like soft partial shading from a far distant tree.
As Mike has already pointed out, salt spray buildup is probably going to cause you a lot of grief from both the corrosion aspect, as well as electrical shock hazard. I think I would be running all my panels in parallel at low voltage, or individually using eight individual boost converters.
Individual converters will offer a lot of redundancy, will current share, and each only has to deal with very manageable current and power. Its going to be more complex, but I would expect it to be more reliable in the long run, as any failures will only ever be partial.
A high voltage system for a house is an entirely different situation with none of the above problems.
In my own case, I have a 100v nominal system with 30 Winston Lithium cells.
The solar controller for it was easy, my biggest headache by far has been the battery management system, and monitoring and protecting the thirty individual cells.
I have been at this for almost three years and still not entirely satisfied with my battery control and monitoring system.
Cheers, Tony. |
| |
dangraham
Newbie
Joined: 07/10/2020
Location: ThailandPosts: 17 |
| Posted: 08:39am 16 Oct 2020 |
Copy link to clipboard |
Print this post |
|
Fatal error: Uncaught PDOException: SQLSTATE[HY000]: General error: 1366 Incorrect string value: '\xE2\x80\xA8\xE2\x80\xA8...' for column 'Message' at row 1 in C:\inetpub\wwwroot2\TheBackShed\forum\PostMessage.php:59 Stack trace: #0 C:\inetpub\wwwroot2\TheBackShed\forum\PostMessage.php(59): PDO->exec('Insert into thr...') #1 {main} thrown in C:\inetpub\wwwroot2\TheBackShed\forum\PostMessage.php on line 59 |
| |
dangraham
Newbie
Joined: 07/10/2020
Location: ThailandPosts: 17 |
| Posted: 08:43am 16 Oct 2020 |
Copy link to clipboard |
Print this post |
|
I can post the error message but not my post LOL. |
| |
dangraham
Newbie
Joined: 07/10/2020
Location: ThailandPosts: 17 |
| Posted: 08:53am 16 Oct 2020 |
Copy link to clipboard |
Print this post |
|
I agree that high voltages in a marine environment are not ideal. Therefore, I would be intending to use an IP67 enclosure with passive heat sink cooling for whatever solution I decide upon. The controller would be located in the bowels of the boat where there is very little chance of spray etc, but the marine environment is definitely a challenge for electrical devices.
I am also considering the possibility of running the two 4S1P strings separately, and instead of mounting the panels horizontal I could have one string tilted port and the other starboard. The boat moves a lot so it's difficult to say if this is worth the effort, if the sun is shining on the bow this would be worse than horizontal, so probably a non-starter.
The 2x 4S1P strings to simple PWM is a good idea, this will probably be the lowest cost and easiest to implement.
I also Like the idea of 8x individual panel controllers, there are no masts or rigging because it’s a motor vessel, so I would need to look at the cost of individual boost converters. As long as the total cost is under $1000US then it’s worth the effort, not sure how efficient they would be if operating outside of MPPT range?
The shadows from my friends sailing vessel from the boom cause sever reduction in yield. When in the marina and boom is moved away from panels he averages 1.2KW/h daily, when the boom is covering a panel this drops to ~0.3KW/h
I don’t really want to bring a shed load of solar cables down from the wheel house roof to the engine room, 2 pairs are ok 8 pairs is getting a bit messy. So then there is the possibility of having the controller located on the roof under the panels and only bringing down 1 pair for the battery connection and possibly a comms cable. This then means the controller is located in the harsh environment.
Noting is ever easy as they say! That’s why it’s so good to discuss these thing before cutting into the boat.
Regarding BMS’s, I know what you mean. My 24V pack has https://123electric.eu/products/123smartbms-gen3/
This has been constantly problematic, the primary cell board with the Bluetooth radio draws a lot more current from that cell, plus I hate Bluetooth. I have been tweaking the charging cycles to try and manage the problem but that cell is always constantly lower. They only have 0.5A balancing current and my charger is 60A, they spend most of their time near float. I will be replacing this with an active balancer soon.
The 148V pack has this BMS,
https://www.elithion.com/lithiumate.php
Probably overkill for what I need but I did not want to take any chances with the power levels involved, charging at 148V 110A is fairly serious business and didn't want to rely on a Chinese BMS to prevent and fires etc. They have 5A balancers and with a few days of commissioning & testing I managed to tame things down and prevent overshoot.
I just decommissioned a set of Winston 12V from another boat and was quite shocked at how bad the cells were inside! Are you running individual cells of the 12V batteries? |
| |
Warpspeed
Guru
Joined: 09/08/2007
Location: AustraliaPosts: 4406 |
| Posted: 09:04pm 16 Oct 2020 |
Copy link to clipboard |
Print this post |
|
I have north facing panels tilted to look sixty degrees above the horizon.
Also an east west virtual tracker, again looking sixty degrees above the horizon east/west.
I also have some flat panels looking straight up.
If I had to make a choice for best all around performance, it would be the flat panels.
I lose a bit when the sun is low in the sky, but in clear sun there will be a massive mid day peak, ideal provided there is enough battery capacity to absorb all the available current while its available.
In total cloud and an evil grey light, it does not matter which way the panels face, but straight up is always very slightly better.
Monocrystalline panels have higher output in blue sky direct sun (silver panels)
Polycrystalline panels seem to work slightly better in cloudy diffused light (blue panels)
In the tropics I would guess Mono's might be best, at higher latitudes probably Poly's.
Don't really know, I am not a sailor.
Cheers, Tony. |
| |
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.