Two years ago, I began a project to upgrade our TC batteries from AGM’s to LFP’s. Our complete TC DC system upgrade includes 320 W STC of PV on the roof, a Victron MPPT charge controller, a Victron DC-DC charger, a Victron Smart Shunt, and the 2x 100 Ah Battle Born LFP batteries.
I’ve been very happy with the specs and performance of the 2x 100 Ah Battle Born LFP’s, but I’ve occasionally wondered if their performance lives up to the hype and meets the specs. Over the past ~30 days, I’ve been slowly discharging the batteries in the TC with an ~3.5 W load. They hit the 200 Ah discharge target yesterday, so mission accomplished.
However, although programmed for 200 Ah of battery capacity, the Smart Shunt indicated there was still 17% of capacity left, and the 12.70 V voltage display also suggested ~17% remaining capacity. These values suggest the low-load capacity of the batteries is 200 Ah / 83% = 241 Ah.
The discrepancy is explained by a battery behavior phenomenon known as the Peukert Effect, and the smart Shunt is smart enough to factor this into its SoC calculation. In this example, the battery capacity is higher than rated due to the very low load. I used the battery specs and data below to calculate the Peukert Exponent for this example to be 1.04 — very close to the 1.05 value I have programmed into my Smart Shunt. 😎
So, these two batteries weigh about 64 lbs. together and can deliver 200 Ah. It would take three or four Group 27 AGM batteries (~190 — ~250 lbs.) to match this performance.
All in all, I’m quite pleased with these batteries!
Safe travels,
Jim / crewzer
