This is second time posting here and I hope someone can help. I want to build a 48v off grid battery bank with about 300 to 500 amp hrs. I have watched all of Wills videos and now have the confidence to build my own battery. Will mostly talks about 3.2v LiFePO4 cells at 100 amps. I see that there are other amps like 150 and 200 amps. Are these higher rated amp batteries better than the 100 amp ones when making a 2 battery bank at 300 or 400 amps? Here is the link for the 150 amp batts. 32 150 amp batts for under $100.ea. https://www.aliexpress.com/item/400...chweb0_0,searchweb201602_9,searchweb201603_53
LiFePO4 questions
- Thread starter pdus
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I am sure others will have different opinions. Consider some day in the future when things are not working as they were when they were new. What if a cell goes bad? To keep it simple, I will talk about a 12v system with 3p4s 100ah cells. If your battery were built so that you could split it into three 12v sections, you could easily find the bad cell. You could also isolate that series string of 4 cells and run on 2/3 capacity while you sorted out a solution. You can could also replace that one cell with less cost than a cell 3 or 4 times that large.
Without using larger cells you can also more easily build 1/3, add 1/3, add 1/3, etc. Also at a later date, grow it by another series string and have the capacity of that string the same (or nearly the same) as your other strings.
Those are some reasons I would choose to have smaller cells rather than larger cells. Larger cells might also have some advantages that I am not aware of.
Without using larger cells you can also more easily build 1/3, add 1/3, add 1/3, etc. Also at a later date, grow it by another series string and have the capacity of that string the same (or nearly the same) as your other strings.
Those are some reasons I would choose to have smaller cells rather than larger cells. Larger cells might also have some advantages that I am not aware of.
Someplace I heard or read that I can not connect too many (more than 2 or 3 ) batts in parallel. If this true and I want 400 amps at 48 v. I will have to connect 2-100 amp cells in parallel X 16 to achieve 48 v. at 200 amps and build 2 banks. Correct?? Or does it matter how I assemble the cells to get 400 amps?
Max Bender
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The 150-200aH prismatic batteries are better only in the sense that they have a greater capacity than the 100ah prismatic ones. Therefore, what is 'better' depends on (A) whatever your power consumption will be and (B) whether the batteries will be sufficiently charged. More to consider is that prismatic batteries have an aluminum shell and must be handled with care so as to avoid dents, dings, gouges, and perforations. Also, placing prismatic batteries side by side leaves no space between them to provide for cooling. And lastly, prismatic batteries have tiny terminals.
Thanks for your input. In this case I can build the battery at it's final resting spot and not have to move it. As far as the small terminals, I guess I will buy a inch pound torque wrench and be very careful. The price per amp hour is hard to resist, 150ah cell for $98.33 or 65.56 per 100 amps. free shipping plus discounts.
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
@pdus have a look here:
https://www.ev-power.eu/BatteryPacks/
and here:
http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/ <--- golden info in there !
KISS applied is always best. keeping it simple & using 16x100AH cells will give you 48V/100AH, 16x200AH = 48V/200AH and so on.
Cells CAN be as big as 1000AH but so is size & cost of course (sit before looking !!! )
The bigger the pack, more unwieldy (size & weight) and potential for possible problems arises.
BMS will have to be a 16S for this configuration, 1 BMS per pack.
16x150AH = 48V/150AH pack @ $1,573.28 based on the price you show. X3 for 450AH = $4,719.84 (48 cells) which when buying volume can drop the price. Do some price comparing and number crunching. Shipping costs & taxes / duties and/or tariffs can also seriously affect the overall cost too.
BTW, 16x 160AH cells comes in at roughly 93 Kilograms / 205 lbs.
https://www.ev-power.eu/BatteryPacks/
and here:
http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/ <--- golden info in there !
KISS applied is always best. keeping it simple & using 16x100AH cells will give you 48V/100AH, 16x200AH = 48V/200AH and so on.
Cells CAN be as big as 1000AH but so is size & cost of course (sit before looking !!! )
The bigger the pack, more unwieldy (size & weight) and potential for possible problems arises.
BMS will have to be a 16S for this configuration, 1 BMS per pack.
16x150AH = 48V/150AH pack @ $1,573.28 based on the price you show. X3 for 450AH = $4,719.84 (48 cells) which when buying volume can drop the price. Do some price comparing and number crunching. Shipping costs & taxes / duties and/or tariffs can also seriously affect the overall cost too.
BTW, 16x 160AH cells comes in at roughly 93 Kilograms / 205 lbs.
Max Bender
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Hmm. Sixteen batteries @200ah each.... four banks of four batteries in each bank.... two banks wired in series to produce a 24v @200aH bank and another two banks wired in series to produce another 24v @200aH bank and then those two 24v @200ah banks wired in parallel to produce 400ah @48v.... did I get that right?
Max Bender
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Considering the cost of those batteries as well as your approach to their handling and placement, I think you'll be fine. But also use copper buss bars if you can and try to avoid drawing more current than the terminals can handle.
Not what I have in mind. The question was can I run as many 48v batts as I want or is it true that anything over 3 is a problem. If yes, then a build of 2 cells at 100 amp each X 16 = 48v. with 200 amps. Then build 2 of these and get 48 v. with 400 amps. Total of 64 100 amp batts
You said "16x100AH cells will give you 48V/100AH, 16x200AH = 48V/200AH and so on. " If I want 400 amps at 48v. I will need 4 48 v. batts. Is it OK to run 4 or more in a series? I read or heard that may be a problem? Maybe with the BMS? That is why I wanted to use 150 batts to build a 300 amp mank or 200 amp cells to build a 400 amp bank.
ghostwriter66
"Here - Hold my Beer"
DELIGREN right now has (8) 200aH 3.2V Grade A - delivered - for $880 ... if you search on this forum you can find tons of info on these
Max Bender
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Oh hey, if you go with 200aH batteries, that same store also sells CALB LiFePo4 ones. Four orders of four in each order would cost around $2800. They can be wired for 48v @ 400ah. CALB batteries are a little bit larger and heavier than Prismatic batteries but much more rugged. Not only that but the CALBs are ribbed so there there's a space between the batteries when placed side by side, and the terminals are about three times larger than those on Prismatic batteries. I have a set of 200aH CALB batteries from that store and not only do they come with copper buss bars, the packaging is superb.
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
Putting batteries in Series increases Voltage. Putting them in Parallel increases Amperage.
TBH the best / simplest is to build 2, 48V/200AH packs, consisting of 16x200AH configured in series, then put the completed packs in Parallel to get the 400AH total capacity. *edit: I put 8X200 instead of 16x200
The cells themselves in series to make a pack are no problem at all. A pack can also have the cells in series & parallel internally as well. The BMS dedicated to the pack is configured accordingly. The "Pack" is your complete battery, including it's BMS. The Pack, depends on the BMS which decides if the pack can be made serial or parallel within a "bank" (bank, being the assemblage of packs) due to it's power handling method. Many BMS' are set for specific voltages, others have various voltage capability but their capacities vary along with that. Then there are BMS' which handle the voltage & amperage externally via relays, which can handle higher surges and allow for bigger & varied bank configurations..
Series Cell Pack. from ev-power link provided previously
This is my 24V/400AH pack. It is 16 cells configured as 8S2P internally, the BMS is a Chargery BMS8T
weighs 150 lbs, 24" long, 12" wide, 10" high
for 48V/400AH this would need 32 200AH cells and use a 16S BMS
weight would be around 300 lbs 24"x24"
TBH the best / simplest is to build 2, 48V/200AH packs, consisting of 16x200AH configured in series, then put the completed packs in Parallel to get the 400AH total capacity. *edit: I put 8X200 instead of 16x200
The cells themselves in series to make a pack are no problem at all. A pack can also have the cells in series & parallel internally as well. The BMS dedicated to the pack is configured accordingly. The "Pack" is your complete battery, including it's BMS. The Pack, depends on the BMS which decides if the pack can be made serial or parallel within a "bank" (bank, being the assemblage of packs) due to it's power handling method. Many BMS' are set for specific voltages, others have various voltage capability but their capacities vary along with that. Then there are BMS' which handle the voltage & amperage externally via relays, which can handle higher surges and allow for bigger & varied bank configurations..
Series Cell Pack. from ev-power link provided previously
This is my 24V/400AH pack. It is 16 cells configured as 8S2P internally, the BMS is a Chargery BMS8T
weighs 150 lbs, 24" long, 12" wide, 10" high
for 48V/400AH this would need 32 200AH cells and use a 16S BMS
weight would be around 300 lbs 24"x24"
Last edited:
perfect, Thank you.
Max Bender
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A bank of two 3.2v batteries @100aH with each battery wired in series would produce a bank of 6.4v @100ah. Sixteen of those banks wired in series would create a bank of 102.4v @ 100aH, and wired in parallel would create a bank of 6.4v @1600aH - a total of thirty-two batteries. The way you have it [a build of 2 cells at 100 amp each X 16] is already thirty-two batteries, and then you say you want to build two of them. Are you planning on buying two orders of thirty-two batteries? Have you at least made up your mind on whether you want 100aH or the 150aH batteries that you showed when you started the thread?
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
I made a typo there. It is 16x200AH in series = 48V/200AH pack. not 8x200
D
Deleted member 4428
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DThames and Max bender make valid points for paralleling batteries. Here are some benefits of series connection. I have done both.
Fewer cells = fewer chances of cell failure or imbalance
Fewer buss bars and cabling = less resistance
A single BMS is possible= each cell is monitored and less electronics to fail
If a single cell fails it is possible to: remove it, install a temporary jumper cable to fill the gap and limp along at 45 vdc nominal. DO NOT do this unless you can reprogram the voltage set points of your charge/discharge equipment to accommodate the 3.65 voltage loss when charging and 2.5 volt loss on discharge. This works for Lead Acid batteries, but the voltage loss was only 2 volts nominal
Back in the day, I removed Lead Acid batteries from GTE telephone company central offices. I rarely saw paralleling.
Every electric forklift I ever owned or saw was a series battery.
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
32Pcs 3.2V 206Ah Lifepo4 Battery US $5,604.05 + Shipping
BLS Store: https://www.aliexpress.com/item/4000220354358.html?spm=2114.12010615.8148356.59.64935c0422QXPr
BLS Store: https://www.aliexpress.com/item/4000220354358.html?spm=2114.12010615.8148356.59.64935c0422QXPr
Max Bender
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BLS sells a set of four 200aH batteries for $699. Four orders (sixteen batteries) costs $2796. Four batteries wired in series will produce a 12v @ 200aH battery bank, times four equals four 12v @ 200aH battery banks. Two of those banks wired in series will produce a 24v battery @200aH. Two more of those banks wired in series will produce another 24v battery @200aH, and those two battery banks wired in parallel will produce a 48v battery bank @400aH. Four orders - sixteen batteries divided into four banks divided into two banks combined to create one bank .
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