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Beginner battery questions re setup (& more!)

gaveupontv

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Joined
Jun 5, 2023
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60
Location
Sacramento Ca
Yesterday I bought 4 CATL 3.2v 302ah from solarsupplyhouse. I pre-ordered them, they should actually be in stock in a week or so. Chris (good guy to deal with) said he'd keep me up to date regarding if the schedule sped up or slowed down. I also got a battery box and connection kit. I followed Will's advice and got a OverkillSolar BMS 120a with the bluetooth module. Everything else is Renogy (panels, 60 amp CC MPPT, Renogy One moniter). I understand Renogy is not really top of the line, so I'll be getting different brands after this depending probably on advice from others. I purchased a 1200 watt Victron invertor with all kinds of potential features, most of whom I know nothing about. I plan to get the $200 Victron shunt (don't remember if this comes with monitor screen, if not I'll get that too) I don't have tons of money, so I'll have to use the Renogy 60 amp CC, and I don't know if it makes a difference who makes the PV's but I'll stick with them for now too. Renogy has motion detectors and door/window switch which I am very interested in getting working with the Renogy One, I'm in a bad area (another project needing attention) and my trailer had been broken into a year ago and EVERYTHING stolen, propane bottles, batteries, bedding, tools, even the cushions and the toilet. On a trip to McDonalds of 1 hour, I came back to find someone had cut the lock to my new Honda generator and taken it. This was Saturday.
Back to the subject at hand- my batteries soon to arrive. I have a lab power supply (think its 5 amp) and I was planning on getting a Victron charger
Its about $200. It has 30 amps, is "intelligent" with single outlet. I guess it charges the entire pack at once. It sounds like it should work but if anybody has a better charger could you suggest one?
I would think top or bottom balancing (you just pick ONE not both?) would be done before batteries are assembled or is it all done after taped together and bus bars attached?
Can anybody point me to information either written or video of the whole setup? I'll keep looking for one here, it seems its partially covered in multiple places and I pick up something in everything I read or watch. I watched Will bottom balance (empty cells NOT below a certain voltage with heater gun) so the batteries fill up equally.
I don't know what I don't know right now. Even one of (the many) questions I asked would be helpful or a pointer of where I can learn more would be great. This is pretty much all new, but I have a lot of tools (even a oscilloscope that I've never opened) and its all very interesting. I'm sure there is everything I need to know on this site (somewhere)
Thanks in advance!
 
Please consult the top balancing guide. Please take the time to read it and follow the recommendations where appropriate.


Bottom balance typically for EV applications or situations where you never fully charge and regularly discharge to empty - not typical. most want to charge to full and use what they need, thus top balance.
 
That is just what I'm looking for, sunshine_eggo. I'm hoping that my battery, a 300 amp hour battery will be enough to get me through the night for my computer and occasional microwave and air fryer use. If I have to, I'll get another generator (I've got a big one, if I need it) I just bought another 2 panels for a total of 8.
 
That is just what I'm looking for, sunshine_eggo. I'm hoping that my battery, a 300 amp hour battery will be enough to get me through the night for my computer and occasional microwave and air fryer use. If I have to, I'll get another generator (I've got a big one, if I need it) I just bought another 2 panels for a total of 8.

It really depends on how much you use them.

Air fryers are typically 1000W-wish
Microwave is 1.6X rated, i.e., a 1000W microwave will CONSUME 1600W.
Computers are highly variable. Gaming units tend to gobble LOTS of power. Typical consumer laptop is < 60W.

300Ah * 12.8V = 3840Wh

Run the air fryer for 3+ hours
Run the microwave for 2+ hours.
 
I have a quick question that I think I know the answer to but I'll ask it anyway. I have a 60 amp charge controller and I have 2 strings of 3 panels in series. The 100 watt panels are slightly more than 5 amps each and the voltage is just under 25 volts each. Since each string is 5 amps and volts add to about 75 volts, the 2 strings should be 10 amps at 75 volts, correct? I decided to add another panel to each series string so I will have 2 strings at 5 amps each (still) and about 100 volts. My CC will handle 60 amps and 150 volts, so I'll now have (still) 10 amp total and 100 volts, well under the limit. I believe my fuse is 60 amps (haven't put in yet). I won't ever get close to 60 amps so should I have a lower amp fuse, or do I really need a fuse at all? I'm going from 3S2P to 4S2P
 
Your calculations are correct for the INPUT, but your understanding of ratings is incomplete.

MPPT Amps are OUTPUT.

Your 60A controller is limited to something like:

60A * 14V = 840W

So, if you put 800W (4S2P) on that controller, you will be near the limit and close to 60A output.

You should have wire rated for 60A between the MPPT and battery as wells as a 1.25*60A = 75A fuse/breaker protecting the (+) wire.
 
You're right, I didn't do the calculations right. I now have 8 100 watt panels up (since yesterday) i get around 400 watts from 6 panels, I figured around 550 watts for 8 panels. 550 /14 =39 amps. Did I do something wrong in that calculation?
I'm getting my 4 CATL cells today. They are rated at 302 amps. I won't get my charger https://www.amazon.com/Victron-Ener...sprefix=victron+30+amp+charger,aps,242&sr=8-3 by
charger unti later today or maybe tomorrow so I have to learn how to set my cells/battery right away. I got the overkill solar BMS that Will advised to get, and I will follow the battery sticky on the numbers to set my CC u for.
 
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