Not recommended due to Low Capacity

Hello!
I'm new here.
I've been watching a lot of the videos on youtube, and I recall in one of Will Prowse's videos he says that he doesn't recommend a certain type of battery anymore because there is a limited amount of useable discharge due to the voltage not matching with what the inverter or the charge controller is able to use.

I can't remember what video this was? He ended up changing his recommendations based on this and now I don't know what videos to follow.
Currently I am looking at some BLS batteries from china on aliexpress. They seem to have a good price but I don't want to find out I can't use their full capacity for some reason.

Can anyone help before I sink a lot of money into this?
Thank you,

I think he is talking about Lithium Titaneate Batteries or LTO their charge parameters are very funky compared to lifePo4. They can be used with a few select inverters though.
This video ?

I'm pretty sure that was in reference to a Tesla battery. He was having difficulty using the lower-end of the battery because his inverter would shut off before the battery pack hit its lower limit.

Yes, the more I think about it, I think he was talking about the Tesla pack that he had installed in his RV.

So I think I am moving forward with the idea of buying LiFePO4 cells from aliexpress, wiring them in series, and using Will's instructional videos and website as a guide.
I will be installing some heat pads, and my batteries will be mounted into a wooden box lined with removeable insulation. It get's down to-20C in the shed where these batteries will live, so I need to account for that.

Are there any other concerns I should be looking at as far as choosing these over lead acid?

I'm looking at the BMS: https://www.aliexpress.com/item/32891427621.html?spm=a2g0o.cart.0.0.fdc43c00dxquej&mp=1

What if I decide to double my battery bank by adding a second string is parallel? Can I just get another 8s BMS?

mrevesz said:

What if I decide to double my battery bank by adding a second string is parallel? Can I just get another 8s BMS?

Click to expand...

That's my understanding: one BMS per string of batteries. I welcome other input here if I'm flat-out wrong.

Hmmm.


I looked into it. Because I am building my own battery from prismatic cells I will have access to the terminals of each 3.2V cell. So what I can do is just parallel cell 1 from from the first battery with cell 1 from the second etc. Then I still only need one BMS for the whole thing. That's actually pretty cool.

I'm not sure if there is a downside to tossing in new cells into a bank after it has been in use for a few years. I grew up with people always telling me not to mix old batteries with new batteries, but I'm not sure if this applies here or not.

The down side to me would be that the new cell wouldn't have age related capacity reduction. lifepo4 cells are widely spec'd to have a life expectancy down to 80% of original capacity in 2000 cycles. Nothing intrinsically wrong with using a new cell in an old battery, but the new cell will effectively be limited to the same level of performance as the old ones by the actions of the BMS.

Cool so I have my panels installed as of today.
Next I am ordering parts for the battery and charger and all the other things I need along with it.

I am going to build a box in which everything that isn't the panels goes. Inside the box will be the charge controller, BMS, Batteries, Temp sensor, Battery disconnect, and finally the inverter.

Part of me wants to forgo paying all the money for all these components and use a automotive 200 amp battery disconnect and a thermometer and program an arduino, but.... I don't want the system to not work correctly and potentially self destruct so I may just stick with buying all these components.

This is the video that I am treating as my how to guide, and most of the things I'm buying are exactly what's in the video.

gnubie said:

The down side to me would be that the new cell wouldn't have age related capacity reduction. lifepo4 cells are widely spec'd to have a life expectancy down to 80% of original capacity in 2000 cycles. Nothing intrinsically wrong with using a new cell in an old battery, but the new cell will effectively be limited to the same level of performance as the old ones by the actions of the BMS.

Click to expand...

That's a good point. Now at least I will understand what the tradeoff is. It is for my dad, so I will suggest that he decide if he wants to double his battery size in the next year or so. We will have a good idea of what the system can deliver vs what his needs are by then as well.