Selecting proper inverter and inverter recommendations

Thread Starter

bigjoncoop

Joined Feb 1, 2019
123
Hey my fellow diy'ers,

I'm currently in the process of Designing and building a portable solar generator. I'm going to be using brand new reclaimed 9s pouch cell packs.

Each pack is:

CAPACITY : 2890mah / 2.9Ah
NOMINAL VOLTAGE : 32.85V
FULLY CHARGED : 37.8V
FULLY DISCHARGED : 25.2V

Also each pack has its own BMS w/ balancing
*** not feasible to split packs up ***

My plan is you put 15 or 20 packs in parallel. Every 10 packs is just over 1kwh

So my question is:
* What type of inverter should I use? 36v or ???

* Should I use a large Buck or boost converter to change the voltage first?

* What size inverter do I realistically need in order to run a small flat screen TV, some fans, some low voltage LED lights etc... 600w, 1000w, 1500w etc...?

Initially I think I'm just going to use it without solar but want to implement solar charging in the near future. If that has to be taken into account when choosing an inverter. Most likely going to use 100w/150w solar panel...

Do they happen to make an AIO solar charge controller / inverter? Just curious...

I'm an electrician by trade and Electronic hobbiest / battery guy for 20+ years

FYI- doing this on a extreme budget!.!.! Looking to purchase a cheap / reliable inverter and eventually MPPT solar charge controller. My mother lives in Florida and doesn't have people to help her, and she doesn't like the idea of a generator so I figured this would be perfect for her.
 

nsaspook

Joined Aug 27, 2009
7,470
Exactly those packs.

I've boughten 15 so far and all were at 30+ volts and fully charged and discharged perfectly fine with capacity real close to factory spec.
Sometimes you hit the Jackpot.
I guess the next question is, what type of cycle lifetime will you get under realistic usage? Daily cycles, emergency power or what type of expected usage?
 

Thread Starter

bigjoncoop

Joined Feb 1, 2019
123
Sometimes you hit the Jackpot.
I guess the next question is, what type of cycle lifetime will you get under realistic usage? Daily cycles, emergency power or what type of expected usage?
Emergency. Building it for my mother that lives in Florida for hurricane season so she has backup power if need be. For now just going to build it and put a Lithium-Ion charger in it, but eventually maybe soon put a solar charge controller in it and get her 100 or 200 watt foldable solar panel for times that she's out of power for a couple few days...

Any suggestions on what voltage input inverter? Am I okay using a 36 volt inverter since that's the nominal voltage of my battery pack or will it not work since the voltage of my pack fully charged is higher than that? And if so should I use a buck converter step the voltage down the 36 volts or use a boost converter and boost it up to 48 volts and use a 48v inverter?

And those battery 9s Packs from batteryhookup.com are brand new, so it says in the description... all the battery packs were 2 volts below the minimum voltage of the BMS and just needed to be jump started for 30 seconds in order for the bms to kick in again... I've been having really good luck so far
 

nsaspook

Joined Aug 27, 2009
7,470
You can find wide-range 20 to 50 volt pure sine inverters that will operate at 36 volts.

My question is how actually useful this device will be beyond the initial battery energy. 100-200 watts of panel will only extend the initial duration, it won't keep the bank fully charged unless the power drawn is rationed to a low level.
 

Thread Starter

bigjoncoop

Joined Feb 1, 2019
123
Like I said in my previous posts, I mainly plan on using this as just battery backup the solar thing is an afterthought. My primary goal at the moment it's just a build a box with batteries and inverter and built-in charger so that way it's always ready to go in case of a power outage.

*** I understand that people want to be helpful, which is fine... but please answer the question that was asked as well as voicing your concerns.... seems to be the trend on every other thread on all forums ***

So what you're saying is I can use a 36v inverter with my battery pack being @ 38 volts fully charged?

And for your second statement. So if 200 watts is not enough solar power to charge up this case in a day or two in the south Florida sunlight then why do so many people build these portable solar generators? Honest question. I was under the assumption that you can get a decent amount of charge in strong sunlight in one or two days
 

nsaspook

Joined Aug 27, 2009
7,470
People voice their concerns because we are not robots answering questions with very few of the facts needed to design or recommend something realistic.

There is a lot of 'IF' in the realistic Solar power equation.

 

Thread Starter

bigjoncoop

Joined Feb 1, 2019
123
@nsaspook

I completely understand. I really do. That's why i mentioned "but please answer the question that was asked as well as voicing your concerns"

I REALLY DO APPRECIATE EVERYONE HERE TRYING TO HELP PEOPLE. AND I MEAN NO DISRESPECT. but i am absolutely not the only person that feels this way. i see people expressing this same issue constantly...

i appreciate everyone's comments and info. that's how we learn. but i have to say that's 80% of my threads and any other ones i read here or at any forum people tend to just completely ignore the original question , and it doesn't get answered until page 2 with no real reason to be that way. GRANTED there are absolutely some questions asked which need more info to even start to answer or are just dangerous sounding....

i asked what input voltage range inverter i needed since i am working with a odd voltage. would a 36v inverter work when my pack will be 38v fully charged or would i be better off stepping my battery voltage up or down to "normal/regular" voltage and yet here we are with still not a clear answer... 8 hours and 7 posts later and here i am typing this. When i asked the same question (copy/paste) in a different forum site and got a clear answer on the first post.

So if anyone has a option on if I should just use a 36v inverter with my 38v fully charged battery and 32.85v nominal or step it up to 48v or down to 36v or etc... i would love to here your advise. Again my goal is not so much using solar to recharge the battery but just to use it as backup power if need be.
thx u
 

nsaspook

Joined Aug 27, 2009
7,470
@nsaspook

I completely understand. I really do. That's why i mentioned "but please answer the question that was asked as well as voicing your concerns"

I REALLY DO APPRECIATE EVERYONE HERE TRYING TO HELP PEOPLE. AND I MEAN NO DISRESPECT. but i am absolutely not the only person that feels this way. i see people expressing this same issue constantly...

i appreciate everyone's comments and info. that's how we learn. but i have to say that's 80% of my threads and any other ones i read here or at any forum people tend to just completely ignore the original question , and it doesn't get answered until page 2 with no real reason to be that way. GRANTED there are absolutely some questions asked which need more info to even start to answer or are just dangerous sounding....

i asked what input voltage range inverter i needed since i am working with a odd voltage. would a 36v inverter work when my pack will be 38v fully charged or would i be better off stepping my battery voltage up or down to "normal/regular" voltage and yet here we are with still not a clear answer... 8 hours and 7 posts later and here i am typing this. When i asked the same question (copy/paste) in a different forum site and got a clear answer on the first post.

So if anyone has a option on if I should just use a 36v inverter with my 38v fully charged battery and 32.85v nominal or step it up to 48v or down to 36v or etc... i would love to here your advise. Again my goal is not so much using solar to recharge the battery but just to use it as backup power if need be.
thx u
Look here: https://forum.allaboutcircuits.com/threads/selecting-proper-inverter-and-inverter-recommendations.166540/post-1470672
You can find wide-range 20 to 50 volt pure sine inverters that will operate at 36 volts.


Every conversion is a lossy process so finding an inverter that works in your expected voltage range is a power saver. My experience with battery operated devices in this power range leads to deep skepticism for a low-cost, high performance solution.

https://forum.allaboutcircuits.com/threads/project-solar-wind-pic-controlled-battery-array.32879/post-1448225
 
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