What size Power Resistor do I need to pull down lithium cells?

[agpfl]

Since your goal is to just get the voltage the same across all your cells, why not charge each cell to the highest voltage cell then connect your BMS and let it top balance for you.

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[JaxPilot]

Originally Posted by Sergio

JaxPilot, Your math is correct, just make sure you mount those resistors to a heat-sink surface or keep a fan running on them.

WooHoo! Winner winner, chicken dinner! Every time I see CGTech's signature, I think to myself "Man, am I glad I don't have to take that test!" Congrats to the board, you have created a more knowledgeable human being.

Originally Posted by Sergio

Since You are only dealing with about 16A, a simple bosch style 12v/40A automotive relay will work for switching the load.

Just so happens I have 5 of those on the shelf, after reading a ton of your other posts on wiring and voltage reducers and such.

Originally Posted by Sergio

The JLD404AH will work, it is just not quite as precise as the JLD5740 with its 10v range setting. Make sure you set the JLD404AH to 3 decimal places.

I thought the 404 would be the best choice for keeping track of the amp hours used in the cart, is that still the case? Would the 5740 be better for the battery pack management, and the 404 in the cart?

Originally Posted by agpfl

Since your goal is to just get the voltage the same across all your cells, why not charge each cell to the highest voltage cell then connect your BMS and let it top balance for you.

agpfl, the only issue I am finding, after investigating your suggestion, is that I cannot find a charger that will limit voltage to 4.0V, which is the max continuous allowed for my cells, with a 10s 4.1V pulse specified. They are all 3.6, 3.7, or 4.2.

[cgtech]

Originally Posted by Sergio

bronsonj, unlike an FLA battery, a lithium battery will deliver the AH stored regardless the discharge rate.

While this is not "perfectly true", it's much closer to true than how a lead battery is rated (dishonest, in my opinion). The lithium is much more "honestly" rated in regards to it's discharge rates. (That's how a 100ah lithium pack whips a 170ah lead pack)

Also, don't worry about the "quiz", many here have far more knowledge than I, and it's just there to get people to think about the curcuit they are trying to understand (and an "easy" chart to relate the figures to). You are doing great.

[JaxPilot]

Well, I started draining the first paralleled cell. Stayed up checking on family in Beaumont, TX, and recorded these numbers. Going to bed, so I'll miss the next several readings.

Start: 3.86
+2H = 3.76
+4H = 3.66
+6H = 3.60

[JaxPilot]

Originally Posted by JaxPilot

Well, I started draining the first paralleled cell. Stayed up checking on family in Beaumont, TX, and recorded these numbers. Going to bed, so I'll miss the next several readings.

Start: 3.86
+2H = 3.76
+4H = 3.66
+6H = 3.60

+8H = 3.55
+14H = 3.32
+15H = 3.29

Starting the next cell, going to have a buddy bring some more resistors and either drain cells faster, or build several sets of power sinks and do multiple cells at the time.