reviewing Tesla auto 48 volt battery purchase

[Sebastian Mitchell]

I was thinking of buying Li Ion batteries for my solar/generator fed inverter charger. currently I have two lead acid banks @48 volts. I know of chaps buying car batteries and tearing them down only to stack them back up into 48-56 volt stacks and buying a BMS for each battery they created. I looked into the workload of the process and the cost. I don't get it? why go thru all the BS. I found 48 volt Tesla Auto batteries with Tesla developed BMS already built into the battery. upon researching this, the newer cars they make have 15 such 5 KW battery packs in one huge unit to power the auto. just two of those would be a massive upgrade for anyone. and they are plug and play. Am I missing something? why are guys buying auto packs they have to put so much work into??

 

[cinergi]

My take: this was the cheapest way to get Lithium* batteries until recently (e.g. with these 280Ah EVE LFP cells). It was "all the rage" starting several years ago. These days, I see people convert AWAY from Tesla to LFP for various reasons (biggest ones being voltage compatibility with inverters as well as the safer chemistry of LFP).

 

[Sebastian Mitchell]

I have never heard of LFP... I will investigate. I see a 48 volt continuous discharge 240 amps 240 AHs bank of LFP's cost 2212.00 US on sale. On sale is important. And the product is sold in 3.2 volt cells, so you have to run them in series to add up to 48 volts just like any other battery. So the Voltage compatibility comment is BS. Lets see.. I can buy two Tesla model S 24 volt 5.3 KWH 18650 cells for 1400 each + 2800.00. connect in series for 48 volt at 5.3 KWH. lets compare apples to apples. 48 volts 5.3 X 1000/120 volts= 441.6 AHs . . . the Tesla batteries are the wEENER in my books... lol. you know what, buy a written off Tesla S model and salvage 85 KW battery Pack... Im looking for new information. some one who is smarter than me.. I need to learn. move forward. Anyone try out those salt water batteries??

 

[cinergi]

I have never heard of LFP... I will investigate.

LFP = LiFePO4 or Lithium Iron Phosphate. That's the chemistry of the popular prismatic rectangular cells many of us are buying these days.

 

[Mudd]

I have never heard of LFP... I will investigate. I see a 48 volt continuous discharge 240 amps 240 AHs bank of LFP's cost 2212.00 US on sale. On sale is important. And the product is sold in 3.2 volt cells, so you have to run them in series to add up to 48 volts just like any other battery. So the Voltage compatibility comment is BS. Lets see.. I can buy two Tesla model S 24 volt 5.3 KWH 18650 cells for 1400 each + 2800.00. connect in series for 48 volt at 5.3 KWH. lets compare apples to apples. 48 volts 5.3 X 1000/120 volts= 441.6 AHs . . . the Tesla batteries are the wEENER in my books... lol. you know what, buy a written off Tesla S model and salvage 85 KW battery Pack... Im looking for new information. some one who is smarter than me.. I need to learn. move forward. Anyone try out those salt water batteries??

Most everybody buying these Eve cells are buying them from China. They take about two months to get here give or take if they don't fall off the boat. 32 cells 280ah would probably run you in the range right around 3K. That would give you 560 amp hours at 48 volts.

 

[cinergi]

I have never heard of LFP... I will investigate. I see a 48 volt continuous discharge 240 amps 240 AHs bank of LFP's cost 2212.00 US on sale. On sale is important. And the product is sold in 3.2 volt cells, so you have to run them in series to add up to 48 volts just like any other battery. So the Voltage compatibility comment is BS. Lets see.. I can buy two Tesla model S 24 volt 5.3 KWH 18650 cells for 1400 each + 2800.00. connect in series for 48 volt at 5.3 KWH. lets compare apples to apples. 48 volts 5.3 X 1000/120 volts= 441.6 AHs . . . the Tesla batteries are the wEENER in my books... lol. you know what, buy a written off Tesla S model and salvage 85 KW battery Pack... Im looking for new information. some one who is smarter than me.. I need to learn. move forward. Anyone try out those salt water batteries??

$2800 in Tesla for 10.6kWh versus the $3100 I paid for 27.6kWh using EVE 280Ah cells (all prices excluding BMS etc). Which one wins?

 

[Ironman]

Would you not have to re-configure the battery to lower voltage? I'm getting second hand info from my daughter who says she thinks hers is 400v.

 

[cinergi]

Would you not have to re-configure the battery to lower voltage? I'm getting second hand info from my daughter who says she thinks hers is 400v.

The entire pack is ~400 but you'd use the individual modules which make up that pack which operate at a lower voltage. That said, the voltages are a bit non-standard and it can be difficult to get the inverter/charger systems to get the full capacity out of the battery.

 

[snoobler]

Tesla batteries are made from 6S modules with a 15-25.2V operating range. These are the modules folks use. Most inverters cut at out 21V and may alarm at higher voltage. This means the bottom 20% of the module is not usable at all - not bad from an operational life perspective, but bad if you ever need that extra 20% in an emergency.

Furthermore, you need to cut the peak voltage to 24.3V for improved cycle life. At that point, you only have 60% of the capacity as usable to get life cycles comparable to LFP.