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Help me with the maths, I can't get my head around this..

Fingers

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I'm looking on Ali express for 8 li iron (lifpo4) 12volt 200ah batteries, but wow how they have gone up in price.
So I'm now looking for alternatives, one of which is a used Growatt li ion 5kw 48 volt battery pack that's on ebay.

But how do I compare the two?

Li iron: 4 batteries=48volt, and as there's 2x lots 200ah becomes 400ah? 48v x 400ah=19.2kw? or is that 400ah ./. 48v=8.3kw? :poop:

Growatt Li ion: 5000watts ./. 48v =104ah?


I'm going to make a jpg file out of this so I don't for get how to do it :)
Thanks for your help.
 
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I'm looking on Ali express for 8 li iron (lifpo4) 12volt 200ah batteries, but wow how they have gone up in price.
So I'm now looking for alternatives, one of which is a used Growatt li ion 5kw 48 volt battery pack that's on ebay.

But how do I compare the two?

Li iron: 2x4 batteries=48volt, and as there's 2x lots 200ah becomes 400ah? 48v x 400ah=19.2kw? or is that 400ah ./. 48v=8.3kw? :poop:

Li ion: 5000watts ./. 48v =104ah?


I'm going to make a jpg file out of this so I don't for get how to do it :)
Thanks for your help.
what is the nominal each battery cell (Ali express)? voltage and Ah. Do your math to get to 48V and its Ah.
Then, compare to Growatt 48V - 5kW.
 
Two battery connected in series doubles the voltage, keeps the same amp-hour. Two battery connected parallel keeps the same voltage, doubles the amp-hour. If three battery then triple. And on with 4,5,6 .
Starter batteries are rated in cold cranking amperes. Deep Cycle Storage batteries are rated in amp-hours. Seller using watts is trying to con you.
 
when are folks going tobfinally to NOT BUY BATTERIES ON ALIEXPRESS ?

do search here
I agree Aliexpress has it's con artists, but I see the same batteries sold on UK ebay as they sell on Aliexpress, only twice the price.
As everything is made in China we have to look in that direction. Would "made in China.com" be good place to look?
 
The math is easy, but getting accurate numbers to start with is difficult. Especially on AliExpress.
For series:
4x12v=48v
So, 4x200ah 12v = 48v 200ah

With 8 200ah 12v batteries you can build 2 of those, or create a 2p4s configuration. Depending on the limitations of the batteries.

That will give you 400ah @ 48v or 19.2kwh

The 5kw 48v gw is probably saying 5kwh.

All that said, I would advise against lithium ion, as they can be extremely dangerous. Not to mention none of the voltages will actually be 12v or 48v even nominally.

I would look at the popular brands around here and try to get them from a reliable source. You will probably not receive true 200ah batteries from AliExpress.
 
I agree Aliexpress has it's con artists, but I see the same batteries sold on UK ebay as they sell on Aliexpress, only twice the price.
As everything is made in China we have to look in that direction. Would "made in China.com" be good place to look?
alibaba is a whole different ballgame to aliexpress.
still gotta be careful, but do a search here and you'll find a number of proven cell suppliers
 
4x12v=48v 4x200ah 12v = 48v 200ahThat will give you 400ah @ 48v or 19.2kwh
Ah, bingo. I wasn't too far off then, I thought what I had written was total pig swill, lol. Time to take a jpg :)

We only have 2.7kw of solar panels, and as we use power through the day for laundry etc, I can see that 4x 12v 200ah batteries is all we could realistically charge. Now I know that I really do have to get some panels facing east (back of my house), the only place left to put them.

Thank you all for your help.
 
8 li iron (lifpo4)
FYI - it's Lithium Iron Phosphate which is abbreviated as LiFePO4.

Growatt li ion
Be careful. Li-ion and LiFePO4 are not the same thing. Did you actually mean Growatt li iron (using your original abbreviation) or do you really mean Growatt li ion (ion vs iron). There's a very big difference in batteries due to that little r.

Back to your original question:

8 12V 200Ah batteries is 8 x 12.8V x 200Ah = 20480Wh. Compare that to the 5000Wh Growatt (which is probably actually a 5120Wh - 48V 100Ah LiFePO₄ battery). You were going to build 2 48V 200Ah batteries. So you need to buy 4 of the 48V 100Ah Growatt batteries for the same capacity.

48v x 400ah=19.2kw?
Actually 48V x 400Ah = 19.2kWh. But it's really 51.2V, not 48V. So 51.2V x 400Ah = 20480Wh.
 
FYI - it's Lithium Iron Phosphate which is abbreviated as LiFePO4.
Yup, that's what I said, li iron, lifepo4. :)
do you really mean Growatt li ion (ion vs iron).
Yup, that's what I said Growatt li ion. I was going to buy it out of desperation, and house it in a purpose built brick battery house. I have decided no to as it's a lot of trouble for next to no return.
Actually 48V x 400Ah = 19.2kWh. But it's really 51.2V, not 48V. So 51.2V x 400Ah = 20480Wh.
Thanks but the extra power isn't going help much :)
I was really going for ball park figures; I don't see the point in precision given that the UK weather is predictably unpredictable.
 
A LiFePo battery is a lithium ion battery. There are many Lithium ion battery chemistries. They are all lithium ion batteries.
 
I have deleted this entry about 24volt batteries, as the inverters the I have looked at require 1kw of solar maximum; which is way too small.
 
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A LiFePo battery is a lithium ion battery. There are many Lithium ion battery chemistries. They are all lithium ion batteries.
Hang on a minute :) lithium ion are the old batteries that explode, and lithium iron is the newer safe liFeP04 batteries, right? :)
 
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45 degrees from the horizon, humm, yes that would be orange, but only onece in a day :)
 
To follow this equation on from 48volt to 230volt, how would I do that?

Li iron: 2x4 batteries=48volt, and as there's 2x lots 200ah becomes 400ah 48v x 400ah=19.2kwh ..........230v ÷ 19.2kwh=11.9kwh?
Is this the correct math formula?

This is very ball park (if anywhere near the correct formula) but this is what I need to know.

Thanks
 
19kwh%230v=83ah @ 230v

Kwh are the same, but there are system losses. You also need to keep in mind the recommended charge profiles for the battery type, especially if it isn't lfp.
 
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