Six 24V batteries in parallel vs 12V in series parallel - actual benefits?

[themdreams]

I'm a solar noob and in the early planning stage of a solar setup on an RV, using a 24V LiFePo4 battery bank setup (I already decided that I will want to go 24V vs 12V for the bank). Planning getting 6 batteries to get to 300Ah, at least initially.

I understand that putting batteries in series is usually not the preferred way to go as this could, in theory, lead to unequal charging at some point. Using 12V batteries to derive at a 24V battery bank I would obviously have to put two 12V batteries in series to get my 24V. Then again, that's only 2 batteries in series, not like 3 or 4 on e.g. a 48V system. Putting that series in parallel should be a non-issue since that is recommended anyway and would the same with the 24V batteries.

Therefore, given the above, what would be the real benefit of spending more on a 24V battery? If I want the same Amp hours I would need to get the same amount of batteries and the rest (step-down converter etc) would be the same as well. Sure, wiring the batteries together would be slightly cheaper, I guess, but I doubt that would offset the $50 premium on e.g. a Battleborn 24V battery compared to the 12V as it's only the short stretches for connecting the batteries. Weight would be slightly increased with the 24V ones as they are heavier but I consider that a non-issue as long as there are still AGMs etc out there that weigh a ton in comparison. Finally, expandability should also not be a relevant factor since that again would only add another series to the parallel setup on 12V batteries.

What am I missing? Why is seemingly everyone going with 12V batteries even on a 24V battery layout/setup?

Thanks for any insight!

 

[John Frum]

6x 100ah@12vdc = 300ah@24vdc
6x 50ah@24volts = 300ah@24vdc
You can't cut a 24vdc battery in half to make 12vdc batteries but you can combine 12vdc batteries to make a 24 vdc battery.

 

[John Frum]

You will want to look at section 3.3 - https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

 

[Steve_S]

DO the Math and think about your space too...

8 Pcs 3.2V 105Ah EVE US$ 552.48 Delivered DPP
8 Pcs 3.2V 202AH CATL US$ 1,081.20 Delivered DPP
8 Pcs 3.2V 280Ah EVE US$ 938.36 Delivered DPP.
SOURCE Known Good Vendor Luyuan: https://szluyuan.en.alibaba.com/productlist.html
Sister company of Xuba.

Add your 8S BMS + box/case/frame + 1 fuse per battery pack and voila.

 

[themdreams]

6x 100ah@12vdc = 300ah@24vdc
6x 50ah@24volts = 300ah@24vdc

Thanks for your reply but I'm not sure I follow. Isn't what you write exactly what I wrote above?

You can't cut a 24vdc battery in half to make 12vdc batteries but you can combine 12vdc batteries to make a 24 vdc battery.

Of course I cannot divide a 24V battery to get 12V, at least not with a sealed one. But that's also not what I'm saying above. I'm well aware that I need a step-down converter to power the 12V circuit of the rig.

My question is very simple: why does everyone use 12V batteries even when putting two in series to get to 24V? Why not "not-series" and go with 24V batteries from the get go, in parallel? With your visualized math (which I only had put in words) it's clear that the result is the same with respect to the amount of batteries needed and the resulting Amp hours.

Thanks for the link as well. But that just confirms what I wrote and understand: try to avoid putting batteries in series and, when putting in parallel, make sure to wire them correctly, e.g. diagonally.

 

[themdreams]

DO the Math and think about your space too...

8 Pcs 3.2V 105Ah EVE US$ 552.48 Delivered DPP
8 Pcs 3.2V 202AH CATL US$ 1,081.20 Delivered DPP
8 Pcs 3.2V 280Ah EVE US$ 938.36 Delivered DPP.
SOURCE Known Good Vendor Luyuan: https://szluyuan.en.alibaba.com/productlist.html
Sister company of Xuba.

Add your 8S BMS + box/case/frame + 1 fuse per battery pack and voila.

You are using battery cells as examples but I mentioned I would be using Battleborn batteries, i.e. finished/sealed packs that also include a BMS.

However, you made me check the dimensions of the 12V and the 24V Battleborn LiFePo4 batteries and - it's exactly the same. So again, apart from the already mentioned higher weight there seems no obvious impact using the 24V for a 24V battery bank setup compared to the 12V batteries. But I guess I'm missing something...

 

[John Frum]

Thanks for your reply but I'm not sure I follow. Isn't what you write exactly what I wrote above?

Yes just more succinct.

Of course I cannot divide a 24V battery to get 12V, at least not with a sealed one. But that's also not what I'm saying above. I'm well aware that I need a step-down converter to power the 12V circuit of the rig.

The point is that if you are considering battleborns, the 12 volt battery has better form utility than the 24 volt battery.
Please consult the wiring unlimited doco that I linked previously.

 

[JoeHam]

You are using battery cells as examples but I mentioned I would be using Battleborn batteries, i.e. finished/sealed packs that also include a BMS.

But I guess I'm missing something...

I think Steve’s point is that you would spend $6000 using Battleborn for a 300Ah setup or you could DIY a 280Ah pack for maybe $1200 with a BMS added.

That is a significant savings for a fairly easy amount of effort.

 

[curiouscarbon]

Those 280 Ah cells are so tempting! They need to be compressed for best reliability. After buying two battleborn, I stopped and switched to DIY LFP packs with BMS. It’s just much more economical.

 

[ghostwriter66]

DO the Math and think about your space too...


8 Pcs 3.2V 280Ah EVE US$ 938.36 Delivered DPP.
SOURCE Known Good Vendor Luyuan: https://szluyuan.en.alibaba.com/productlist.html
Sister company of Xuba.

Add your 8S BMS + box/case/frame + 1 fuse per battery pack and voila.

Hmmm . I think your prices are a little off ... I ordered 8 Pcs 3.2V 280Ah EVE yesterday and paid US$ 740.00

Then i ordered 32 more and paid 2941.36 ....

(and no - i didn't even have to play the race card - LOL)

and i ordered from SHENZHEN BASEN TECHNOLOGY ... ALEX CHEN ... who happens to be a nice girl to talk to ...

 

[Deleted-User]

ALEX CHEN ... who happens to be a nice girl to talk to ...

Ahhh..so you played the sex card! I'll work on my falsetto.

 

[Steve_S]

Hmmm . I think your prices are a little off ... I ordered 8 Pcs 3.2V 280Ah EVE yesterday and paid US$ 740.00

Then i ordered 32 more and paid 2941.36 ....

(and no - i didn't even have to play the race card - LOL)

and i ordered from SHENZHEN BASEN TECHNOLOGY ... ALEX CHEN ... who happens to be a nice girl to talk to ...

Prices I listed are With Delivery DPP
I just looked at Shengen Basen an 8x 280AH = $878 USD with delivery ? DPP ??
LINK: https://www.alibaba.com/product-det...ml?spm=a2700.icbuShop.41413.13.757248c2OHmLBk

And Ghosty, why are you caring about prices, you are buying for an Oil Company for their use... Should be buying American Assembled Packs to support the American Economy ! Especially given all the Love the US Government has for it's Oil Companies with subsidies and property tax free lands etc... Make them buy Battleborn, Relion, SimpliPhi or similar US Products and support US Workers & Companies ! You cannot say the Oil Companies do not have the money....

 

[ghostwriter66]

Prices I listed are With Delivery DPP
I just looked at Shengen Basen an 8x 280AH = $878 USD with delivery ? DPP ??
LINK: https://www.alibaba.com/product-det...ml?spm=a2700.icbuShop.41413.13.757248c2OHmLBk

And Ghosty, why are you caring about prices, you are buying for an Oil Company for their use... Should be buying American Assembled Packs to support the American Economy ! Especially given all the Love the US Government has for it's Oil Companies with subsidies and property tax free lands etc... Make them buy Battleborn, Relion, SimpliPhi or similar US Products and support US Workers & Companies ! You cannot say the Oil Companies do not have the money....

Not sure whats listed but MY invoice was about $150 cheaper -- w/ delivery ... (they made have made a mistake - or maybe its one of my 1000 cousins - (I crack myself up) ...

The oil industry is dying - about 50% of the folks I use to work with are gone -- every dime we save keeps someone else working ... sure its great for the avg driver - and those prices should drop even more - but the accountants say not so much for the companies - which means - do more with less ppl ...

I have been taking allot of training on large DC circuitry since it all deepness on who comes out ahead on 04 NOV ... either the oil industry will continue -- OR - it will be disseminated, price of fuel will jump 3.00 more a gallon - and allot of petroleum engineers are going to wish they had studied solar and wind ... don't get me wrong - not a fricking chance in history that this GREEN stuff is going to work the way that some of these politicians thinks - but they are willing to spend your money proving it won't ...

 

[Steve_S]

Petro will continue but will also continue it's downward trend regardless of who get's to be POTUS, it's global and no matter what one country says, the rest are doing... One thing if Biden get's in, he's already clearly indicated funding being made available for workers transitioning from Petro Industries to other industries like RE. Wind, Solar, Sea Turbines and more are just growing & growing worldwide... Texas has lot's of Wind Turbines....

TBH, I am quite surprised you can scattergun shop for batteries like you do. If I was your companies Asset Management person, I'd shut that down ASAP. Really, you could have developed a longer term ongoing relationship with a vendor or two and got preferential pricing overall due to the amounts your company orders every year.... In fact, if you look back over the past 12 months at how many cells you've purchased, add it all together and then got quotes based on 1000 cells, you'd be looking at significant dollar savings, PLUS the shipping cost would be seriously lower too.... You could ask the Top 3 Vendors to submit quotes for batches of 250 cells with shipping and see what happens... (better be seated).

PS: I happen to know of folks (companies) buying in Batches of 500 and they GET DEALS ! I cannot say how good but GOOD ! Batches are going to 2 African Nations, 1 South American and one in Zealand. I was actually pondering restarting one of my companies to offer pre-assembled battery packs but good sense kicked in as I would not be able to do it for too long and I have other things I have to do in the short time I have.