Say you want a nominal 12V bank.
You could just wire a single string of four cells aka 4S, each at the same AH capacity you want for the bank as a whole.
However, there's zero redundancy there, if one cell goes bad, you no longer have 12V.
Next option, 4S2P is pretty standard, first wiring 4x 3.2V cells in series to get to nominal 12V,
then paralleling two of those strings in order to increase AH capacity.
This gives you easy redundancy. Each half of the bank is still 12V, so if one cell dies, you just split the bank,
see which half has the bad cell by checking for lower voltage, and carry on with the better half, which is now a 12V bank at half capacity.
If you wire using 2P4S instead, first wiring 2x 3.2V cells in parallel to get to nominal 12V,
then paralleling two of those strings in order to increase AH capacity,
you'd no longer be at 12V if one cell dies, you'd have more work to break down the bank, maybe far from home, to be able to identify the bad cell(s) and then reassemble to a single 4S bank.
For even greater redundancy, 4S3P or 3P4S means if one cell fails, you still have 2/3 of your AH capacity at 12V. The former has the above advantage over the latter.
However, getting up to 4+ strings, it is generally recommended to go "parallel first", with say 6P4S rather than 4S6P. Apparently lots of **individual cells** in parallel is not a big problem to get to higher total bank AH capacity,
but going past three **strings** in parallel can lead to balancing issues. I believe that is true, even with a proper balanced wiring scheme using buss bars in place, as per "Method 3" here: http://www.smartgauge.co.uk/batt_con.html
In theory of course this issue can be accommodated simply by choosing larger AH capacity cells as your basis to start with, but for the sake of this discussion let's assume there are good reasons for the owner using a greater number of smaller cells.
Another easy solution would be hardware that allowed for an independent per-cell charging regime, so high-accuracy top-balancing with the xSyP bank still assembled, was as easy as just pushing a button. But again, for the sake of this discussion, let's assume that's just a pipe dream.
So finally, first question for the hive mind:
Do **you** think going "parallel first" with 6P4S is better than 4S6P? Why, what factors (other than convenient redundancy as discussed above) are involved?
If a specific context is required, let's posit aluminum-cased prismatic cells, each 20-25AH, with a target of 120-150AH total bank capacity at 12V nominal, so still relatively easy to handle at around 45-50lbs.
Q2: What would be your configuration of choice, using the same total 24-count of those same-sized cells, to go to a 24V bank at half the AH?
Q3: A nominal 48V bank (now getting into propulsion territory), 30-38AH total?
You could just wire a single string of four cells aka 4S, each at the same AH capacity you want for the bank as a whole.
However, there's zero redundancy there, if one cell goes bad, you no longer have 12V.
Next option, 4S2P is pretty standard, first wiring 4x 3.2V cells in series to get to nominal 12V,
then paralleling two of those strings in order to increase AH capacity.
This gives you easy redundancy. Each half of the bank is still 12V, so if one cell dies, you just split the bank,
see which half has the bad cell by checking for lower voltage, and carry on with the better half, which is now a 12V bank at half capacity.
If you wire using 2P4S instead, first wiring 2x 3.2V cells in parallel to get to nominal 12V,
then paralleling two of those strings in order to increase AH capacity,
you'd no longer be at 12V if one cell dies, you'd have more work to break down the bank, maybe far from home, to be able to identify the bad cell(s) and then reassemble to a single 4S bank.
For even greater redundancy, 4S3P or 3P4S means if one cell fails, you still have 2/3 of your AH capacity at 12V. The former has the above advantage over the latter.
However, getting up to 4+ strings, it is generally recommended to go "parallel first", with say 6P4S rather than 4S6P. Apparently lots of **individual cells** in parallel is not a big problem to get to higher total bank AH capacity,
but going past three **strings** in parallel can lead to balancing issues. I believe that is true, even with a proper balanced wiring scheme using buss bars in place, as per "Method 3" here: http://www.smartgauge.co.uk/batt_con.html
In theory of course this issue can be accommodated simply by choosing larger AH capacity cells as your basis to start with, but for the sake of this discussion let's assume there are good reasons for the owner using a greater number of smaller cells.
Another easy solution would be hardware that allowed for an independent per-cell charging regime, so high-accuracy top-balancing with the xSyP bank still assembled, was as easy as just pushing a button. But again, for the sake of this discussion, let's assume that's just a pipe dream.
So finally, first question for the hive mind:
Do **you** think going "parallel first" with 6P4S is better than 4S6P? Why, what factors (other than convenient redundancy as discussed above) are involved?
If a specific context is required, let's posit aluminum-cased prismatic cells, each 20-25AH, with a target of 120-150AH total bank capacity at 12V nominal, so still relatively easy to handle at around 45-50lbs.
Q2: What would be your configuration of choice, using the same total 24-count of those same-sized cells, to go to a 24V bank at half the AH?
Q3: A nominal 48V bank (now getting into propulsion territory), 30-38AH total?