I could use a hand

[Dkl87]

Hello, new to the forum,
I will try to keep my post simple
I am looking for advice on bms for a future project, I am in Philippines and trying my best to source all parts through a shopping site and in future source the materials through alieexpress or alibaba but in the meantime .... trying for a milkcrate design as my first battery
Here is the list of items I plan on purchasing
Volt meter

https://shopee.ph/product/102891893/6450422941?smtt=0.188612690-1631263215.9

500 watt sine wave inverter

https://shopee.ph/product/301705550/4550428304?smtt=0.188612690-1631263290.9

Bms ( need help figuring out which one )

https://shopee.ph/product/215434955/8339924608?smtt=0.188612690-1631263337.9

Batteries I will use Lifepo4 Battery 4 unit LiShen 3.2V 202ah ( trying for a simple 12v setup

https://shopee.ph/product/225699792/5952049998?smtt=0.188612690-1631263521.9

The only 2 areas that I need help with is

1.How do you add a simple wall charge plug device I have a bluetti ac50s I think it is called and it plugs into the wall to charge ( trying to source parts through shoppee website/app )

2. Which is the proper bms to use ( using the shoppee website/app

https://shopee.ph/product/225699792/5952049998?smtt=0.188612690-1631263521.9

Additional info, I am in mainly using this for brownouts , meaning power companies shut down quite frequently, and while I like the ac50s I am limited to running the 40 to 50 watt fan for only 8 hours. Any and all help is appreciated

 

[Diysolar123]

first thing is to make sure you write down what your goals are... to support a larger load or a longer runtime, or both!

the bluetti ac50s looks like it can actually provide up to 300W AC which is much more than your 50W fan so why buy another AC inverter?

If you need to run your 300W load for 8hours, well, that would be a 2400Wh load.
or you could run a 100W load for (2400 / 100) = 24hours!

The bluetti only has 500Wh of capacity so you will need at least 2000Wh more from your batteries.
Your four batteries in series to make a 12v battery pack will yield 12 * 202Ah = 2424Wh if you drain the pack completely, so that seems like its enough for the scenario I mentioned, only you know what load you want to actually run.

maybe a few simple things to help you out, you should think about:
-You already have an inverter, the bluetti, why buy another one unless you "need" more power.
-The BMS is just to protect the battery which is a good idea, what size BMS you need is dependent on the current you plan on drawing. A 300W load at 12v would be around 300 / 12 = 25Amps which is not much at all, get a 50A BMS and you will be fine.

-your bluetti can take external power from a battery pack or solar panel...it does not know the difference it just wants at least 12VDC on its MC4 input connector and will draw at most 10A. This is the easy way to get a longer run time out of the bluetti as it states it can both charge and disharge at the same time.

You will need a way to charge your lifepo4 batteries from your wall power, there are lots of lifepo4 battery charges that would just run off your wall power when it is available.

so you would have:
the wall VAC charging the lifepo4 pack with a charger when its available ==> the lifepo4 pack feeding into the bluetti via the MC4 ==> the bluetti generating your 120VAC.
When power goes out the bluetti thinks the lifepo4 pack is still providing power and will use that to generate 120VAC.

and all of this is just me guessing what you "really" need ;-)

 

[Dkl87]

first thing is to make sure you write down what your goals are... to support a larger load or a longer runtime, or both!

the bluetti ac50s looks like it can actually provide up to 300W AC which is much more than your 50W fan so why buy another AC inverter?

If you need to run your 300W load for 8hours, well, that would be a 2400Wh load.
or you could run a 100W load for (2400 / 100) = 24hours!

The bluetti only has 500Wh of capacity so you will need at least 2000Wh more from your batteries.
Your four batteries in series to make a 12v battery pack will yield 12 * 202Ah = 2424Wh if you drain the pack completely, so that seems like its enough for the scenario I mentioned, only you know what load you want to actually run.

maybe a few simple things to help you out, you should think about:
-You already have an inverter, the bluetti, why buy another one unless you "need" more power.
-The BMS is just to protect the battery which is a good idea, what size BMS you need is dependent on the current you plan on drawing. A 300W load at 12v would be around 300 / 12 = 25Amps which is not much at all, get a 50A BMS and you will be fine.

-your bluetti can take external power from a battery pack or solar panel...it does not know the difference it just wants at least 12VDC on its MC4 input connector and will draw at most 10A. This is the easy way to get a longer run time out of the bluetti as it states it can both charge and disharge at the same time.

You will need a way to charge your lifepo4 batteries from your wall power, there are lots of lifepo4 battery charges that would just run off your wall power when it is available.

so you would have:
the wall VAC charging the lifepo4 pack with a charger when its available ==> the lifepo4 pack feeding into the bluetti via the MC4 ==> the bluetti generating your 120VAC.
When power goes out the bluetti thinks the lifepo4 pack is still providing power and will use that to generate 120VAC.

and all of this is just me guessing what you "really" need

I am trying go build my pack similar to the ac50s
But bigger batteries your input for the bms is perfectly solid advice , the inverter to me is simple to do.
The part I am needing help with is finding a piece of hardware to attach to the batteries , that will have a outlet plug , so I can get a wall charger to simply plug into that outlet to charge the battery
I am uncertain if this exists or if I need to use a solar charge controller to do this for me etc... lol

Basically trying to copy the idea of how simple it is to charge the ac50s ,

My goal is to have something similar to the ac50s just a lot longer runtime

Then I can donate the ac50s to family members who can benefit from it

Could I use this and put different connectors on it and have it safely charge it?

 

[chrisski]

The BMS you linked is for Lithium Ion cells. Over voltage protection is way to high at 4+ volts per cell. Should be around 3.65. I think the version you linked is for cells like the 18650.

I do have the Lithium Iron Phosphate 30 amp Version of that BMS, but I still would not recommend it. Overvoltage is 3.75 volts, too high above 3.65, and temperature protect cuts off charging below 32F, which means my batteries could be charged below what they are specked for which is bad. I set my charge voltage pretty low hoping to prevent Rey away cells, and I won’t use this in anything close to freezing temps. I do wish I could monitor daya from the battery via Blue Tooth, but for around $20 delivered to my door, that’s asking too much.

For cells bigger than 100ah like yours are, I would get a BMS that has a software that you can monitor and has adjustable limits for over/under voltage and over current. The one I purchased for my bigger pack the Overkill BMS does that. This is the same one that will recommends.

Not sure what you would use to charge it from an AC outlet. Things like RV converters with adjustable voltages like Powermax or an Iota Converter with the Lithium Charging chip may be good. You probably want a higher amperage converter to not have to take forever to charge.