mrkelkel
1 mW
- Joined
- Feb 17, 2019
- Messages
- 17
Hi there. Long time reader, first time poster. I intend to connect and use a 20-cell Li-ion pack and a 24-cell LiFePo4 pack in parallel.
I've got a 24-cell LiFePo4 battery pack rated for 76.8V, 56Ah as the main pack in my electric moped. Recently I assembled a 20-cell Li-ion pack from some 18650 cells. It's rated for 74V, 30Ah, and I intend to make it my auxiliary pack.
In the quest for more speed, I upgraded my moped with a motor-controller combo from Mobipus with a rated peak output of 7.2kW. Thus, during full throttle acceleration, current draw from the battery pack is approximately 100A. Voltage drops on either the main LiFePo4 or auxiliary Li-ion packs are significant (~8V) but tolerable.
Still, more speed and harder acceleration is desired. The idea of connecting both packs in parallel popped into my head. In theory, the larger combined capacity of both packs would lead to less voltage drop, spreading the load across both packs and extending their lifespan.
Fully charged, the LiFePo4 pack measures at 86V, and the Li-ion pack measures at 84V. The plan is to use the main LiFePo4 pack for a while, then connect both packs when the main pack reaches 84V.
The cutoff voltages of the LiFePo4 and Li-ion packs are ~67V and ~64V respectively. I intend to leave a small safety margin, and disconnect the packs at 70V.
I realize that the chemistry of both packs are different, and my experience in this field is limited. Would any issues crop up if both packs are connected and discharged in parallel?
Thanks!
I've got a 24-cell LiFePo4 battery pack rated for 76.8V, 56Ah as the main pack in my electric moped. Recently I assembled a 20-cell Li-ion pack from some 18650 cells. It's rated for 74V, 30Ah, and I intend to make it my auxiliary pack.
In the quest for more speed, I upgraded my moped with a motor-controller combo from Mobipus with a rated peak output of 7.2kW. Thus, during full throttle acceleration, current draw from the battery pack is approximately 100A. Voltage drops on either the main LiFePo4 or auxiliary Li-ion packs are significant (~8V) but tolerable.
Still, more speed and harder acceleration is desired. The idea of connecting both packs in parallel popped into my head. In theory, the larger combined capacity of both packs would lead to less voltage drop, spreading the load across both packs and extending their lifespan.
Fully charged, the LiFePo4 pack measures at 86V, and the Li-ion pack measures at 84V. The plan is to use the main LiFePo4 pack for a while, then connect both packs when the main pack reaches 84V.
The cutoff voltages of the LiFePo4 and Li-ion packs are ~67V and ~64V respectively. I intend to leave a small safety margin, and disconnect the packs at 70V.
I realize that the chemistry of both packs are different, and my experience in this field is limited. Would any issues crop up if both packs are connected and discharged in parallel?
Thanks!