48V LiFePo4 battery 16S2P or 2P16S

Ogre said:

I am twinning the (brand new) cells though because the cost of a second BMS and then the BMS master unit would add another $1000 to the cost of the system.

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I have the same philosophy because I use a $600 contactor based BMS from Orion (Orion BMS JR2) it is a scaled down automotive grade BMS.

Ogre said:

Auto manufacturers hadn't really figured out how to use lithium technology economically. Tesla Roadsters were one of the first (if not the first) automotive applications of lithium batteries and that was 2008.

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Exactly. That has been my point all along in this discussion with regard to most automotive manufacturers other than Tesla. In 2005, Tesla was just a startup and not many people paid attention to them. Today, In California they are the second largest selling brand behind Toyota. They actually sell more EVs than Toyota.

Ampster said:

@Ogre
I agree with the concept that matched cells are better. I agree with @RCinFLA that DIYers do not have the equipment to match cells like the the OEMs do. I also believe that one can have a cost effective pack by using Grade B cells and using them conservatively. The laws of physics when applied to a risk management strategy can help a DIYer find that happy medium. I do not believe perfect should be the enemy of good.

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I'm specifically taking issue with the stated goal of matching the highest capacity with the lowest and then the 2nd highest with the 2nd lowest. Here is a research paper that tests this fairly thoroughly with LFP cells. One of the unexpected issues they found that the current between the parallel cells as they rebalanced themselves could easily exceed 1C for several minutes. They tested 18650 cells with a capacity difference of up to 20%.

Ampster said:

I have the same philosophy because I use a $600 contactor based BMS from Orion (Orion BMS JR2) it is a scaled down automotive grade BMS.

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I specifically chose a Rec BMS (Rec Q specifically) because it is compatible with a Wakespeed WS500 alternator controller via canbus and also Victron compatible. This way the 48V 100A alternator will not load dump if the BMS disconnects because the BMS will tell the Wakespeed to power down the alternator before it disconnects. Also, pertinent BMS data will be available via my Victron Cerbo GX