Hello,
(all batteries I'll mention in this thread are LiFePO4)
Current setup
I have 2 x 12V batteries that are about 1 year old. I also have 2 x 12V batteries that are pretty new. I have a 24V system consisting of 2 batteries in series, which are then hooked up in parallel to another 2 batteries in series, i.e. 2S-2P. Each series is composed of 1 old and 1 new battery.
Considering changing to...
My question is will it be better to change this to parallel first, then series. The reason Is that I've read this is best practice when batteries are mixed age; I'll elaborate my understanding:
Disadvantages of parallel first, then series
1) if a bank is affected or disconnected somehow, the entire system goes down. Right now I can disconnect 1 series while the other series continues to function, so there is redundancy
2) checking individual battery voltages: individual battery perofrmance can be measured in series when the system is being discharged/charged and an underperforming or overcharging battery can be identified immediately. In parallel, each battery must be removed from the bank individually to be tested.
Expansion in the future seems to tilt in favor of going parallel first...
Adding more batteries in the very near future is not a concern however if I was to expand by adding 2 more batteries in the not so near future, it seems I will have to go parallel as the older batteries will certainly have a higher internal resistance and less capacity, and will cause the issues mentioned above.
Looking for your feedback.
Thanks!
(all batteries I'll mention in this thread are LiFePO4)
Current setup
I have 2 x 12V batteries that are about 1 year old. I also have 2 x 12V batteries that are pretty new. I have a 24V system consisting of 2 batteries in series, which are then hooked up in parallel to another 2 batteries in series, i.e. 2S-2P. Each series is composed of 1 old and 1 new battery.
Considering changing to...
My question is will it be better to change this to parallel first, then series. The reason Is that I've read this is best practice when batteries are mixed age; I'll elaborate my understanding:
Why Parallel First, Then Series is Better if batteries are mixed age......or am I wrong?
- During Discharge:
- Parallel First: The older batteries contribute less current due to their higher internal resistance, and the newer batteries pick up the slack. The system remains stable because each parallel group balances internally.
- Series First: Both batteries in a series pair must pass the same current. The older battery’s voltage drops faster, reducing the performance and stability of the series pair.
- During Charging:
- Parallel First: The newer battery in each parallel group absorbs more charge, while the older battery absorbs less. This prevents overcharging of the older batteries and ensures smoother charging for the group.
- Series First: The older battery’s higher resistance causes its voltage to rise faster, triggering an early cut-off and leaving the newer battery undercharged.
Disadvantages of parallel first, then series
1) if a bank is affected or disconnected somehow, the entire system goes down. Right now I can disconnect 1 series while the other series continues to function, so there is redundancy
2) checking individual battery voltages: individual battery perofrmance can be measured in series when the system is being discharged/charged and an underperforming or overcharging battery can be identified immediately. In parallel, each battery must be removed from the bank individually to be tested.
Expansion in the future seems to tilt in favor of going parallel first...
Adding more batteries in the very near future is not a concern however if I was to expand by adding 2 more batteries in the not so near future, it seems I will have to go parallel as the older batteries will certainly have a higher internal resistance and less capacity, and will cause the issues mentioned above.
Looking for your feedback.
Thanks!