Solar and Lifepo4 Questions

[monsterdeer]

I have some solar and LiFePo4 questions. Situation: 4 100ah 12v lifepo4 low temp protection batteries in parallel. 4 100w solar panels in series plus another set of 4 100w solar panels in series and both sets are tied in parallel. Gives me about 80 volts and around 11 amps. MPPT 60 amp controller. Everything is fused/circuit breaker with bus bars to specs. Battery monitor with shunt. 2000w inverter. Batteries are stored in a battery box with between 2-4" foam plus reflective metallic sheeting. Battery box has a louvre to allow heat to escape in the summer. Dc relay hooked up with digital thermostat to shut off the solar panels from charging below 34 degrees. All parallel battery cables same size and length. All batteries were separately charged to full with a lithium battery charger before I hooked them all together. I used two high qlality voltmeters to make sure everything is copesthetic. QUESTIONS:

1. The solar panels in series/parallel connection produce 11amps. So why do I need a 60 amp controller? I can't see how 11amps input goes to 60 amp output. However, I can see how 80 volts gets reduced to around 12 to 13ish volts.
2. I bought a 20 amp lifepo4 battery charger to initially charge the batteries separately. So it does not produce anywhere near the .50c suggested charging rate for LiFePo4 batteries. Also, my MPPT only produces around 13.5 amps. So, how the heck do you have a way to charge at over 50 amps?
3. I bought 4 heated lifepo4 batteries from a "reliable" company. The first time it got real cold my two thermometers read 27 degrees but where supposed to be heated around 40 degrees. These 4 batteries were sent back. I am now paranoid of BMS heated batteries. So I bought 4 low temp protected batteries. Still paranoid, so I installed a 34 degree solar panel charging cut off relay. Now, it only cost $25, but I am thinking off putting another relay to disconnect the controller at 34 degrees. Is too much fail safe too much? In other words, are two relay cut offs bad?
4. My 2000 watt inverter has 3 110/120v outlets 15 amp outlets. So I ran 3 different 10 gauge wires to 3 15 amp 120v receptacles that have 2 usb ports each. I bought 3 inline 15 amp GFI protected cords one for each line. These GFIs cords are actually GFIs that connect to extension cords. Kind of iffy. Can you think of another way to put "proper" GFI protection in these "extension cords". Note, they don't sell 120v GFI receptacles with 2 USB ports. If they do, then they would be very very expensive.
5. My AC and microwave are wired directly to an in board generator that produces 120 volt. I once stupidly tried to run a 10 gauge 120 volt extension cord to an outlet to run my AC. Don't do this. Even if you had a soft start AC, the juice needed after the start will cause "damage". Believe me. It can be ugly. So I bought a 120 volt tower AC that uses 4 ice packs. Totally inconvenient. Any suggestions better than buying a portable tower AC?
6. I can not see anyway to hook up the 120 volt microwave to the system. Do I need to go through the converter or try to tie in before the generator. Each alternative sounds ugly.

 

[Rocketman]

#1 you have 800w of solar. The magic of mppt is
70v @11a becomes 13.5v @ 59 amps. Granted you will probably never see the full 800w - but you will get what you get.

#2 The .5C charge rate is the Max rate. My system can hit .35C if everything is running max - usually .2C is all I get - if just solar usually I am at or under .1C. Your battery will last longer at .25C (or below) rather than .5C - so that’s a good thing.

#3 I have my Victron shunt report the temp to my Solar charge controller and if below 38F it doesn’t charge. Plus my batteries have a heater under them, Plus if I try charging when the bms is colder than 33F - it will shut it down. - You do You.

(Remember you are the system engineer- it is your job for the system to run correctly. And KISS - keep it simple and serviceable (I always mess up on that last one).

#4 no help here…

#5 Air Conditioners are very tricky- I can run mine with a Micro Air EZ start on my Multiplus 12/3000 inverter - for about an hour then I either need to turn it off or start my Generator. Voltage drop and amp startups are also tricky.

#6. You need a transfer switch to switch from Shore/Generator to Inverter. (You may already have one for switching between Shore and Generator - you will need another).
My solution is inside my Victron Multiplus- it has an integrated transfer switch. There are lots of other cool features that work great - so if you ever need a new inverter/charger - look at a Multiplus.

Also make sure you have massive wires between the batteries and the inverter- they should be 2/0 (2-aught or 00) to handle a 2000 w inverter.

Good Luck

(Were my answers clear or did I miss understood something).

 

[Bop]

You (like many others) are confused by charge controller ratings...
That '60A' is NOT what it can take in from the panels, but what its maximum OUTPUT rating is...

Basically- a 60A charge controller on '12v' nominal (12.7 x 60= 762w) with most manufacturers rating it at '750w', the same charge controller on a nominal 24v bank is rated at '1500w', and on a 48v battery bank at '3kw/3000w'
The MPPT charge controller basically is an 'electronic transformer' for DC (with some fancy stuff added to keep the panels in their 'happy zone' ie Maximum Power Point) your panels have two sets of voltages and current limits- one is Voc (voltage open circuit) and Isc (current short circuit) and the other is Vmp and Imp (respectively Voltage and Current maximum power)
MPPT is Maximum Power Point Tracking- and is exactly what the label says- it tracks the panels output to keep the total wattage outputted the highest it can...

I can't see how 11amps input goes to 60 amp output. However, I can see how 80 volts gets reduced to around 12 to 13ish volts.

Its all in the wattage...
80v x 11A = 880w total input..
thats fed into the MPPT controller, it does it magic electricity stuff inside, and out comes 13.8v at 63.76A (880W/13.8V = 63.76A)

(in practice they aren't 100% efficient, so it will limit at around 60A- however MPPT is one of the most efficient electronic devices around, with many achieving over 98% efficiency!!!)


If the panels are only running at 60v instead, then (assuming they are lower rated panels with a lower Vmp and higher Imp) you could have the same 880w coming in at 60v at 14.66A
If the panels were rated at 100v, then it would still be the same 880w, at 100v and only 8.8A
In every case, the output is the same 13.8v at 60A...

The thing is that the manufacturers specify the 'ideal wattage (usually that 750w/1500w/3000w for a 60A controller at '12v/24v/48v'- some (not all) can be considerably 'over panelled, but in good conditions, you won't get a increase in output power- put 1000w of panels on you 12v 60A charge controller and although you increased the panel input by 25%- the output stays.... 60A at 13.8v... (because it is the maximum OUTPUT limit I mentioned before...)

There are advantages in overpanelling if you get a lot of poor weather conditions- a 1000w array on a 60A charge controller will output its full 60A even in poor weather conditions, where if it was only on 750w, it couldn't pull enough from the panels to achieve that full 60A power output, and it can also achieve a higher total daily generated output than the 750W array- but its maximum will always be that 60A OUT...

 

[Bop]

I'll try and cut the other questions down more quickly lol...
2. You have 4x 100ah batteries- so their total capacity (often marked as C or CA in the specs) is 400Ah total- 0.5C is 0.5 x 400 = 200A- yeah your 20A charger isn't going to cut it to get to 200A/0.5C
(20<200 lol)
3. Don't know why people buy LFP when they live in cold conditions- LYP (LiFeYPO4) can be charged at full current down to -20C/-4F and reduced current down to -40C/-40F ie no heated batteries needed...
4. Not a yank, so I'm more familiar with the '230v' single phase used in 'TROTW' (the rest of the world ie 220v, 230v and 240v are all '230v nominal) but I am pretty sure that you could find GFI's (RCD's to us) that are 'panel mounted' and put them in an enclosure??? ie forget all the extension cords and put in a proper 'household wiring system' except run off an inverter instead of the mains... (thats the accepted practice for permanent installations)- the ideal solution would be put a 'changeover switch' in the generator output cables and use that to select either the genpack or the inverter and use the existing wiring throughout- less messy than extension cords lying everywhere...


This is a fusebox from Australia (mine at the old house actually)- each of the MCB's (Miniature Circuit Breakers) is a RCD that protects the entire circuit... (the five up the top right with the 'test' pushbuttons under the breakers toggle...)- we dont have 'GFI outlets'- all outlets (and lights, and A/C) are protected by their respective breakers in the fuse box...


5. it's all just a case of appropriate wiring sizes - my little 'tower' A/C (proper compressor type I use in the caravan, bought new circa 2007), is barely capable of running on 2.5mm^2 and that is maxing out the power cable... (10A at 230v nominal)- the split cycle at the old place was wired in 4mm^2, as was the old 'window rattler' AC I had at the rented place before that- putting either of those last two on any 'extension cord' would have had that cord glowing... even the one below is right at the absolute limits on a 'heavy duty' extension cord here...

6. you said you have 3 120v/240v outlets on the inverter- you will need to disconnect the microwave from its existing wiring to the generator and connect it to the 120v part of the inverters output (hard wired or plugged in???)- but the changeover switch sounds a lot easier and safer...

If you don't know this bit, then can I STRONGLY suggest getting someone who knows what they are doing in- Mains voltage (even the 110/120v nominal that the US uses) can kill you dead- anything over 60v has the potential to kill you if the current flow is through your heart...

 

[monsterdeer]

I enjoy getting educated. It is great to not have to pay tuition!! So much to know--so little time.....

 

[monsterdeer]

I initially wanted to run mini circuit beakers in a box--I have no room to install a proper breaker box with GFI breakers . But I never could find any GFI mini breakers. So next I looked into installing 3 mini breakers and swap out my current receptacles to GFI receptacles. But I never could find any GFI receptacles that also had 2 USB ports. I know I can just install the GFI receptacles and then just use a USB adapter to give me USB ports but then I lose one of the outlets from the two outlets on a receptacle. I run a lot of USB powered items in 2 out of 3 receptacles.