Just a total noob willing to built a 8S from Amy Wan

[damon6sdl]

Hi All! And before I start, thanks a lot for the whole informations available here. Would probably never have even thought about what's below without this forum.

So... I'm building a van. Not really a van tho, being a 11meters long truck. Reaching the battery discussion, it seemed quiet clear to me that I'd go for Lithium. But prices are just.... Brrrr. Here's what I've been offered: 25,6V/150AH 3,84KWH Lithium Battery - Powerbrick+ and integrated BMS. About 3000€ so 3300$.

It doesn't "look" too hard to build. At least in videos. So I've been reading again and again to see what you guys seem to mention as the reference of Chinese market for now. And found Shenzhen Luyuan Technology Co., Ltd and their "EVE 280AH LiFePO4 (LFP) 3.2V Cells Battery (New Version LF280K with 6000cycles, Fully Matched)--Genuine Grade A".

I've been talking with Amy for a while, and am just waiting for the cells availability. I said I know nothing about balancing and therefore would need the most matched ones possible.

I thought about going for 560 AH but It's probably way too much, so I'll start with 8S for a 24V 280AH battery.

About the BMS, she was offering JBD BMS 8S 100A. But as a noob, I saw 100A is way below 280 (it probably has nothing to deal together...) so I said I'd need the JBD BMS 8S 300A. But in fact I have no clue.

I said I need everything: She added insulating materials and a box. Busbar and nuts are included.

Asking about the maximum charging current and discharge current of the BMS I need... I said "If I got it well, it could be 5-95 but probably safer and better to go 20-80?" Yeah, if it wasn't obvious yet, consideer I know nothing. I've been reading and that's all.

So i'd like to have your opinion guys, on the choice of the LF280K fully matched. the fact I'll not balance them. The fact I'm just a noob scared to go for a project he wont be able to do. Do you guys know about this BMS? Do you guys feel like my 300A BMS request makes sense or it's just dumb AF? About the right answer to give for the charging/discharging current? Will I need anything specific to build with the materials listed there?

Thanks a lot if you took the time to read. Thanks even more in advance if you take the time to answer!

Bat

 

[time2roll]

If you plan to drain a 280 battery at 300 amps you get less than an hour of run time. 100 amp gives you three hours run time.

Most likely the 100 amp will power the microwave through the inverter. If you need to run an air conditioner, microwave and hair dryer at the same time then the larger 300 BMS is needed along with a larger inverter.

 

[Bud Martin]

OP: How many KW-Hr are you using per day?

 

[damon6sdl]

OP: How many KW-Hr are you using per day?

We made a simulation of 4 176.10 Wh/d

Most likely the 100 amp will power the microwave through the inverter. If you need to run an air conditioner, microwave and hair dryer at the same time then the larger 300 BMS is needed along with a larger inverter.

We'll neither have a microwave nor an air conditioner. The most powerful stuff we might use are an hair dryer or a soup mixer, but most likely not both at the same time

 

[Rednecktek]

Well rough numbers say a 24v battery with a 100a BMS should allow you up to a 2400w inverter. If your inverter is smaller than that then a 100a is plenty.

 

[damon6sdl]

Well rough numbers say a 24v battery with a 100a BMS should allow you up to a 2400w inverter. If your inverter is smaller than that then a 100a is plenty.

Yes it's under, it's Victron Phoenix Smart 24/2000. Thanks, that's already one thing solved!

 

[Rednecktek]

We made a simulation of 4 176.10 Wh/d

Well, 280Ah at 24v gives you about 4900Wh of battery after factoring in efficiency losses and fudge factors. You Your system will work if you can guarantee you will get enough sun and panel output to fully refill your batteries PLUS whatever you use during the day. You're going to want to increase your battery capacity quite a bit and/or find a way to significantly cut your usage down. At 30a of current you're looking at 800w of panel for 7 perfect hours a day. If your BMS allows up to 50a of charging then you'll need 1200w of panels for 4 hours per day.

What's the maximum charge rate on that BMS? That will determine how much panel and amperage you can use to refill those batteries.

 

[John Frum]

Well, 280Ah at 24v gives you about 4900Wh of battery after factoring in efficiency losses and fudge factors.

280 amp hours * 3.2 volts nominal * 8 cells * .9 depth of discharge = 6,451.20 watt hours.

 

[Rednecktek]

280 amp hours * 3.2 volts nominal * 8 cells * .9 depth of discharge = 6,451.20 watt hours.

*.85 efficiency and fudge factor losses = About 4900w, give or take. I was napkin mathing in my head here. 24v * 280Ah = 6720Wh *.85 = 5712. Stupid maths fail!

OK, so a day and a half perfect world efficiency. I sit corrected.

 

[John Frum]

inverter watts hours is
280 amp hours * 3.2 volts nominal * 8 cells * .9 depth of discharge * .85 conversion factor = 5,483.52 inverter watt hours.

 

[damon6sdl]

Thanks for your explanations guys! I actually have the solar panels already, went on 1600W. Also that simulation we made was quiet high as I wanted some margin