Can i prallel first then series connect the two lipo's

[recumbent]

I purchased six, 8-s lipo's but would like to place three batteries on each side of panniers. 60 volts nominal to be plugged into the controler.

My panniers have a perfect tight sleave attached to the hard wall next to the rear wheel. Ideally I'd like to place three batteries in each pouch, in each pannier.

I hope this makes sense, it's mostly for weight balance.

Each 8-s pack is 30 volts nominal.

Can i parallel each bank of three cells, including the ballance leads?

Then series wire, (with a harness) the two banks together to make 60 volts.

 

[mwkeefer]

Actually that's how your supposed to build a pack...

Parallel into clusters of smallest cell count (ie, 5 or 6S) but highest AH count (ie: 2P = 10AH), then connect those into series configuration...

You also want to parallel the balance leads between packs in parallel when possible using either solder method or balance extenders like those from Gary Goodrum.

-Mike

 

[SilverSurfer]

This may seem like an idiotic question, but Im really curious, hell, I NEED TO KNOW! How do you balance 4 cells, in a 4p pack? Because, from what I can see of how a balance circuit is set up. And knowing how to make a battery pack. I cant see how a balancer can tell, or for that matter affect the state of charge in any single cell, in a paralell configuration. I am building a full 24s4p setup right now. two parts 12s4p one on each side of bike. And am planning to setup all my packs 12s with balancers, and hook into parallel after so I can do a full balance charge weekly.

One balance wire to pos side, one to neg side of each parallel set. How can the sensors tell which cell is in what state, and how can the balancer achive any single cell adjustment? God I must be a dork! I cant see it without some isolation diodes and crap. If you want to get the most of the pack, and maintian it properly, you NEED to balance it regularly dont ya? Is it properly balanced if once connected in parallel, the cells never get single cell attention?

Please, talk to me!

SS

 

[mwkeefer]

Silver,

Don't think of it as a 4S4P pack... think of it as a 4S1P 20AH pack - when properly paralleled, each of the balance taps would also be paralleled from the 4P configuration, these are connected to a balancer as if they were a single 4S pack of 20AH and then you balance.

If your going to ask next, but wait couldnt a failed block in the parallel cause failure of the surrounding cells? Yep it could, but monitoring the cells as a pack is good enough providing you don't over discharge or ove charge them as a pack.

Personally I would like balance taps at each P in the pack, atleast for cell level monitoring but really... cell level monitoring in our terms is more of "Parallel Strand monitoring".

Hope it helps!

-Mike

 

[tostino]

Parallel strand monitoring is as good as it gets as far as a bms is concerned. After you parallel many cells, in effect, they become one large cell.

It would add WAY too much complexity to a BMS, and even pack construction, to individually monitor and balance each individual cell.

 

[SilverSurfer]

Silver,

Don't think of it as a 4S4P pack... think of it as a 4S1P 20AH pack - when properly paralleled, each of the balance taps would also be paralleled from the 4P configuration, these are connected to a balancer as if they were a single 4S pack of 20AH and then you balance.

If your going to ask next, but wait couldnt a failed block in the parallel cause failure of the surrounding cells? Yep it could, but monitoring the cells as a pack is good enough providing you don't over discharge or ove charge them as a pack.

Personally I would like balance taps at each P in the pack, atleast for cell level monitoring but really... cell level monitoring in our terms is more of "Parallel Strand monitoring".

Hope it helps!

-Mike

Parallel strand monitoring is as good as it gets as far as a bms is concerned. After you parallel many cells, in effect, they become one large cell.

It would add WAY too much complexity to a BMS, and even pack construction, to individually monitor and balance each individual cell.

LOL OMG!!! I bought 16 sets of balancing wires and was just about to bury myself in a nightmare of balancing wires! I thought the individual cell state was vital to the whole, This is gonna be alot easier than I thought! Thanks you guys!