Lithium VS Lead

Is a picture worth a thousand words?

In this corner, weighing in at 24 lbs, is a 36V 12Ah pack of AGM lead acid. And in this corner, weighing in at 10 lbs, is a 36V 10Ah pack of LiFePO4.



The LiFePO4 pack consists of 12 40138 cells in series. The lead acid pack is three Werker 12V 12Ah batteries from Batteries Plus. In each pack, cells were fully charged and balanced. They were both discharged thru a 10A load until reaching the pack cut-off of 30V for the lead and 29V for the LiFePO4. Ambient temperature was 21°C.



The lead acid pack started just above 36V but voltage started to drop early on and kept falling until hitting a 'shoulder' at around 6.6Ah. The LiFePO4 pack started above 36V and stayed until 8.4Ah.

Voltage Support: Advantage Lithium.

The 12Ah lead pack provided just under 7Ah (58% of rated capacity), while the 10Ah LiFePO4 pack provided just over 9.6Ah (96% of rated capacity).

Power output: Advantage Lithium.

Discharge cycles: Lead acid should give somewhere between 300 and 500 cycles at 100% depth of discharge. Our LiFePO4 should give about 1500 cycles at 100% depth of discharge.

Discharge cycles: Advantage Lithium

Weight: 10lbs VS 24lbs Advantage Lithium

Overall value: Lead was $44.95 each for a total of $134.85. If we get 400 cycles of 6.93Ah, we're paying $.0486 per Ah. (A more realistic 300 cycles costs us $.0649 per Ah.) LiFePO4 at $48 each was $576. If we get 1500 cycles of 9.63Ah, we're paying $.0399 per Ah.

Overall value: Advantage Lithium

Smaller, lighter, more power for a longer period, no hazardous chemicals - what's not to like?!

LiFePO4 Battery Pack Management - Part 1

Welcome Back!

You just know that any day that starts with a good cup of coffee and new toys to play with is heading in the right direction! We’ve had a couple of these days in a row – here’s how they’ve unfolded so far:

The first part of the fun began when UPS brought the battery management board kit that we ordered from Gary Goodrum at TPPacks.com. He and others on the Endless Sphere battery forum designed a battery management board tailored to PSI and A123 LiFePO4 cells used in electric bicycle-sized battery packs.

It took a couple of minutes to remember which box the soldering irons were in, then the fun started. The BMS went together quickly and worked first time. Always a good sign!

The next piece of the puzzle happened along last week when our friends at UPS brought us a couple of boxes. Now we have a new batch of 40138 cells to use – and some new battery chargers to test.

Stay tuned for part two - the fun is just getting started!