Four 200AH cells Vs. Eight 100AH cells

[TheGriz]

Hi Folks,

My goal is a single 200AH capacity LiFePO4 4-cell battery pack. I am seeing 200AH prismatic cells on AliExpress at reasonable prices. Is there a downside to using single 4-cell 200AH battery pack, rather putting two 100AH 4-cell packs in parallel? Specs are comparable between 100AH and 200AH cells.

If using a single 4-cell 200AH battery pack, what is a recommended BMS???

Thank you folks for your anticipated insight and help!

Mike

 

[ghostwriter66]

NO difference at all in performance -- BUT from where i sit -- with less batteries less moving parts -- less connections to go wrong ...

Look at the CHARGERY BMS ....

 

[TheGriz]

NO difference at all in performance -- BUT from where i sit -- with less batteries less moving parts -- less connections to go wrong ...

Look at the CHARGERY BMS ....

Thank you. I was thinking the same as far as fewer cells equals less components to go wrong.

 

[tictag]

I minor point to add I guess, but the 8-cell battery would weight more (terminal nuts, cases, busbars etc).

 

[cass3825]

An argument could be made there is some inherent redundancy in having 2 100Ah packs. If a cell goes bad in one of the packs, you still have 100Ah of capacity to get by on. If a cell goes bad in your single 200Ah string, you’re SOL. “Two is one, & one is none.”

 

[Supervstech]

... why not 8 200Ah cells... mmmm. Redundancy...

An argument could be made there is some inherent redundancy in having 2 100Ah packs. If a cell goes bad in one of the packs, you still have 100Ah of capacity to get by on. If a cell goes bad in your single 200Ah string, you’re SOL. “Two is one, & one is none.”

 

[TheGriz]

... why not 8 200Ah cells... mmmm. Redundancy...

Ahhh....more power! MORE POWER!!!

 

[Supervstech]

“What the heck is a jigawatt?”

 

[ghostwriter66]

An argument could be made there is some inherent redundancy in having 2 100Ah packs. If a cell goes bad in one of the packs, you still have 100Ah of capacity to get by on. If a cell goes bad in your single 200Ah string, you’re SOL. “Two is one, & one is none.”

Have you ever actually seen one of these go bad? It takes quite a bit to make it stop working ...

 

[cass3825]

Have you ever actually seen one of these go bad? It takes quite a bit to make it stop working ...

I haven’t, I’m just not a fan of having a potential single point of failure. OP asked for downsides of a single pack, just giving him one.

 

[TheGriz]

I haven’t, I’m just not a fan of having a potential single point of failure. OP asked for downsides of a single pack, just giving him one.

Appreciate comments from both of you. Yes, when I was working in the defense industry, we did ALL we could to preclude SPFs. At the same token, the technology has advanced and minimized the risks of failure. Thanks for both posts.

 

[Steve_S]

Appreciate comments from both of you. Yes, when I was working in the defense industry, we did ALL we could to preclude SPFs. At the same token, the technology has advanced and minimized the risks of failure. Thanks for both posts.

Rule of Three ! Primary, Backup & Redundant backup for primary critical systems.
BTDT and still do it. 3 ways to heat, 3 ways to get my water, 3 ways to make power. Life off-grid, can never be too prepared especially in potentially hostile environments.

 

[Steve_S]

My goal is a single 200AH capacity LiFePO4 4-cell battery pack. I am seeing 200AH prismatic cells on AliExpress at reasonable prices. Is there a downside to using single 4-cell 200AH battery pack, rather putting two 100AH 4-cell packs in parallel? Specs are comparable between 100AH and 200AH cells.

It really is one half dozen or another. But there are some great deals on cells right now that are reliable & have good rep here. Now look at a couple of the good vendors like Deligreen, Xuba, RJ etc (which people have dealt with & reviewed here) price out the cost of 100AH & 200AH cells from the same manufacturer CALB, Winston = $$$. Blueyes from CATL or EVE are much less.. so apples to apples. What does 8 100AH cells cost vs 4 200AH cells ? Both will only need one BMS *BMS should be sized to max load Amps possible by inverter + margin for safety.

The discharge & charge RATE capacity of larger cells is relative as well. 1C discharge from 200AH cells = 200A, from 100AH cells = 100A for example. But if you parallel up two 100AH packs, it equates to the same output collectively (provided the packs are properly paralleled) Also, don't forget, each pack should be fused appropriately for the loads being put on it (max rating of inverter Watts ÷ Volts DC = Amps) ie: 2000w÷12vdc=166.66A

Now just to add a wrinkles:
- Bigger cells weight more, so S&H will increase of course.
- Larger, take more space too, obviously.
- Costs decrease between sizes the larger you go ! so calculate the total useable capacity in kWh per dollar. 12vdc X 100AH = 1200kWh (kiss formula) of course it's different if you use 80% only and there are other factors but for $ comparison, KISS is best.
- worst wrinkle. Buying more "smaller" cells ie 50AH and building multiple smaller packs with lighter (cheaper) bms for each may actually be cheaper but then you get 4 packs for 200AH version 2 packs with 100AH cells or one pack with 200AH cells. dang nabbit ! hehehe fricken options.

Good Reference on wiring your batteries is here: https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

 

[TheGriz]

It really is one half dozen or another. But there are some great deals on cells right now that are reliable & have good rep here. Now look at a couple of the good vendors like Deligreen, Xuba, RJ etc (which people have dealt with & reviewed here) price out the cost of 100AH & 200AH cells from the same manufacturer CALB, Winston = $$$. Blueyes from CATL or EVE are much less.. so apples to apples. What does 8 100AH cells cost vs 4 200AH cells ? Both will only need one BMS *BMS should be sized to max load Amps possible by inverter + margin for safety.

The discharge & charge RATE capacity of larger cells is relative as well. 1C discharge from 200AH cells = 200A, from 100AH cells = 100A for example. But if you parallel up two 100AH packs, it equates to the same output collectively (provided the packs are properly paralleled) Also, don't forget, each pack should be fused appropriately for the loads being put on it (max rating of inverter Watts ÷ Volts DC = Amps) ie: 2000w÷12vdc=166.66A

Now just to add a wrinkles:
- Bigger cells weight more, so S&H will increase of course.
- Larger, take more space too, obviously.
- Costs decrease between sizes the larger you go ! so calculate the total useable capacity in kWh per dollar. 12vdc X 100AH = 1200kWh (kiss formula) of course it's different if you use 80% only and there are other factors but for $ comparison, KISS is best.
- worst wrinkle. Buying more "smaller" cells ie 50AH and building multiple smaller packs with lighter (cheaper) bms for each may actually be cheaper but then you get 4 packs for 200AH version 2 packs with 100AH cells or one pack with 200AH cells. dang nabbit ! hehehe fricken options.

Good Reference on wiring your batteries is here: https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

Ahhhh...KISS principle and wrinkles in same paragraph!!! What's a sane man to do? Seriously, all good stuff...thanks.

 

[DENWA]

8 cells can be either 12V 200Ah or 24V 100Ah. Your choice if future plans change

 

[wbwoodward]

Higher voltage (24 vs 12) = less voltage drop in wiring; another thing to consider.