Nissan Leaf Solar
- Thread starter Kirk
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Ampster
Renewable Energy Hobbyist
It depends on whether you will be using six modules 2P12S or seven modules 2P14S. Each module is 2P2S with a maximum voltage per module of 8.4 volts. You will need a BMS, a charge controller that can handle the total voltage of the pack.
My battery bank will, probably, use seven modules and be in a very small power shed outside my cabin. I've been told that these batteries are relatively safe, but fires have happened, so I was planning on keeping them out of the cabin. Each winter we have a day or two that gets down to zero F, each summer we get days with continuous 90 F plus and occasional 100 F plus. Should I get something that prevents the batteries from being charged when temps are too low or too high? Are most charge controllers able to be adjusted to not allow the batteries to be discharged past a certain limit and to prevent charging above some limit. I'm hoping to have sufficient capacity to only need the upper-middle range of discharge in order to have reserves for the worst meteorologic conditions and prolong the life of the batteries by allowing them to operate only in their most efficient range. I've been reading and watching Youtube (way too much) and have come to understand that this is a good strategy for designing a system. I welcome constructive criticism.
Ampster
Renewable Energy Hobbyist
Yes, you may want to add temperature control to your BMS requirement. Or even some kind of AC or DC heating element. Of course plenty of insulation in your battery enclosure.
Why are you using that instead of LiFePO4?
Ampster
Renewable Energy Hobbyist
Initially, I did not see the OP question as prospective. If he still has a choice I would recommend using LFP which can be purchased new for less than used Leaf modules. Then he can safely put them in the cabin.
Your replies are very helpful. I have my PV panels (six 325W panels), I'm inclined towards the Nissan batteries, I had planned a heating pad under the batteries, I was thinking of using a single or several small fans like the ones used on servers to move air through the enclosure in summer. I would use a line voltage thermostat to turn on the fans and a thermocube (check Amazon) for the heating pad. There will be large screened ventilation doors (insulated for winter). At this point in my planning I have no idea about BMS's, charge controllers and inverters. Just on general principles I'm inclined to being sure of getting a pure sine wave inverter because I don't know what I might choose to plug into an outlet. I will probably have a small fridge, LED lights, a TV and radio and I'll keep my phone and laptop charged up. I will use the TV as a monitor and use a bluetooth keyboard and mouse so the laptop will just be for computing power because I'm used to a desktop and don't care for the ergonomics of laptops. I'm a retired carpenter so I will inevitably use a power tool now and then.
Hope I'm not boring you but now it gets complicated. I have zoning issues which may prohibit my using a permanent array so I will arrange my panels to be quickly removable, my solar shed will be on wheels and the connection to my cabin will be through a generator receptical rated at 240V 30A. This would qualify as a large solar generator and I'm permitted by zoning to use a generator. Please don't even ask what kind of bureaucratic nonsense makes it easy to use a dirty generator but difficult to use clean solar power but I'm way too old to "fight city hall" and just barely smart enough to find a work-around.
Will Prowse recommends the MPP all in one units and I'm looking for 240V output to run through the generator connection and I'll wire the cabin with a small Square D load center and regular outlets and switches, probably won't need more than two circuits, maybe 3. The 5KW all in one unit is a bit pricey but building with components seems challenging. I think a smaller unit, if it had 240v, might do the job but I'm not sure. Most of the ones I've seen tested on youtube trip when you get close to their rated output.
Hope I'm not boring you but now it gets complicated. I have zoning issues which may prohibit my using a permanent array so I will arrange my panels to be quickly removable, my solar shed will be on wheels and the connection to my cabin will be through a generator receptical rated at 240V 30A. This would qualify as a large solar generator and I'm permitted by zoning to use a generator. Please don't even ask what kind of bureaucratic nonsense makes it easy to use a dirty generator but difficult to use clean solar power but I'm way too old to "fight city hall" and just barely smart enough to find a work-around.
Will Prowse recommends the MPP all in one units and I'm looking for 240V output to run through the generator connection and I'll wire the cabin with a small Square D load center and regular outlets and switches, probably won't need more than two circuits, maybe 3. The 5KW all in one unit is a bit pricey but building with components seems challenging. I think a smaller unit, if it had 240v, might do the job but I'm not sure. Most of the ones I've seen tested on youtube trip when you get close to their rated output.
With some silly zoning issues I'm allowed to use an external generator but I may not have a permanent solar system. My array will be quickly removable and all my equipment and batteries will be in a very small trailer that is mobil. The cabin will be "fed" through a generator cable to and from proper generator receptacles and plugs (240v30a). The regulation does not prohibit solar generators so my system will be mobil and I will not be forced to use a stinky noisy generator when I can use clean quiet solar.
loverofpeace
New Member
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- Apr 22, 2020
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New LiFePo4 cells will run you $500 including shipping for a 280ah 12V one. So $2k for a 280ah 48V one. How large of a bank are you looking to build up and how much are the Leaf batteries used?
I'm 73 and not used to being new at anything. However, there are language issues that I don't have solved yet. You guys are speaking in amp-hours and I'm thinking in watt-hours. I'm pretty sure those two things are translatable. If I've got the math right a 280ah 12v battery is 3.36kWh which is nearly (but not quite) as much as 7 Nissan Leaf modules which is 48v producing 3.5kWh. I can buy a Nissan Leaf battery for $1800 with 48 modules from which I could construct two 12v batteries and and six 48v 3.5kWh batteries for a total of 21kWh not including the two little 12v units which could be combined for a 24v battery if I preferred. If I disregard the two 12v the remaining 48v batteries would cost about $300 each. I have someone who would like half the batteries so I can get 48v 10.5kWh with a spare 12v battery for a total of $900. of course it's not that simple as I still have high and low voltage charge controls, high and low temperature sensors and controls and BMS to think about and not of it's free. for comparison that's $1.8k for 437ah 48v one (with the two left over 12v units). LFP $7.15/ah, Nissan $4.12/ah That seems too good to be true but that's why I'm here, to learn what I'm getting wrong BEFORE I spend the money. Thanks for the help.
Ampster
Renewable Energy Hobbyist
I think in Watt hours. In 2016 I bought a Nissan Leaf pack for $1500 so $1800 is not a bad deal. The capacity was only 80% so in your case that is still a good price of $100 per kWh.
What does that 80% refer to? I see these percentages in the ads and know that it has something to do with being used up but what is used up, the number of cycles usefully left in the batteries or the voltage or wattage or amperage...? I can't associate the word capacity to anything meaningful to me. I've seen many G1 Leaf packs rated 60% and G2 Leaf packs rated at 70%. My math says that 6/7=86 which means that 60 is 14% less than 70, but the prices were 1800 and 2500 and 18/25=72 so the 1800 is 28% less than 2500. I would expect the capacity difference to correlate with the price difference but it doesn't.
Additionally I look at wrecked Leafs and wonder how best to judge the batteries with very few clues. I am beginning to understand the importance of how the batteries are maintained during the life of the vehicle. The number of miles on the odometer is of some importance but I've heard that somewhere in the world Leafs are used for taxis and their drivers have learned how to extract amazing efficiency for years from their batteries and far exceed the life expectations for them. This all seems like juggling with more than three balls.
Also, the higher the voltage of the battery the proportionately less a reduction in ah results in a loss of kWh? I used to be very good at math but that was a very long time ago and I'm "rusty".
Just do the math.
volts x amps = watts
12 volt 100Ah battery has 1200 watt hours.
80%
12 volt 80Ah battery has 960 watt hours.
Ampster
Renewable Energy Hobbyist
I was referring to 80% of capacity. Depending on how you want to measure it Amphours or Watthours. It is hard to know how many cycles are left. When buying a pack it is hard to do a test unless the seller lets you take the lid off. Even then only measuring internal resistance is the only rest that can be done quickly. A full charge/discharge would take hours and need access to power.
I just bothered to read the power bio under your post and you might not know everything but I'd guess you know enough. So then I went back and re-read all your posts above, feeling stupider and stupider as I went. The conclusion I've come to is that the biggest piece of work that I have left to do is to come up with the right questions; I'm pretty sure you've got the answers and I just need to know how to ask what I want to know. As you are beginning to use LFP's and you've been using Leaf modules can I assume that both can be good ways to go, especially for a rather small system? Am I correct that used Leaf batteries are significantly cheaper than new LFP's. Cheap is doubly important to me because it's part of my nature and because I'm retired on a rather tight budget. I have a very tiny cabin in the woods which I would like to be slightly civilized. I have a composting toilet, a very large water tank, and abundant sunshine. I also have a nasty bureaucracy to deal with (mentioned above). I could probably make do 3/4 of the year with a quiet little inverter generator but I would not enjoy that much. I would like to have a water line from my tank to the cabin with an on/off switch on the pump. I would also need heat tapes to protect the water tank and the line to the cabin and the lines in the cabin With that I will keep a small cistern in the loft full the water that will just be for washing dishes, cooking and brushing teeth etc. I'd like to power a cellular based security system. I'll have wood heat and electric for A/C, the smallest 115v mini-split. I will probably watch tv, listen to the radio and browse the internet via laptop. I know nothing about some of the things I've heard about such as using a phone for a wifi hotspot. When 5G comes in around here perhaps I'll be able to stream movies. That sounds perfect to me and I hope that is doable. I'll require some outlets both indoors and out so that I can run something like a saw or compressor once in a while.
I'm hoping that I will be able to stay there for 4 days in a row occasionally in the winter during hunting season without worrying that I'm using too much battery (no A/C in winter should help) and I'm hoping I can afford a system that is sufficiently robust that it will long outlast me. My wife can then enjoy it and my sons will get many years of use.
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