Upgrading to Lithium Batteries

rdg1rdg1 Registered Users Posts: 26 ✭✭
Hello all....
I an looking at replacing my 8-12V 100aH AGM batteries with lithium.  I have a 48v system.
2800w solar,
Flex-power 3648 system

My question is... What are the experiences folks have had with the 48v 200aH batteries or is there an advantage of 12v/24v in series/parallel?

Thanks for any and all info.

BTW, this is an off-grid application in BCS, (battery stores are not just down the road and round the corner....).


Comments

  • Wheelman55Wheelman55 Registered Users Posts: 185 ✭✭✭
    edited September 23 #2
    I’m not an expert. I’m using the Discover AES 48 volt Lithium batteries and am very happy with them. 

    By BCS I assume that you refer to Baja California Sud?  If so you don’t need to worry about sub freezing temps. Just make sure to keep the batteries out of direct sun for the heat part. 

    FYI I’m on the Rio Grande near Big Bend National Park. Not quite as hot as you but still pretty hot. 

    I’ve got my batteries and electronics in a 10x10 foot insulated shed. I put a small Mitsubishi mini split in the shed which keeps the batteries cool.

     I calculated that the efficiency gained by keeping the batts and electronics at 75 F more than makes up for the energy to run the split. The batteries and gear should last longer as well. 

    Something to keep in mind when switching from FLA is that you can use a smaller AH battery with Lithium. 

    The batteries that I use are 130 AH @ 48 volts, and I would guess that one of these would replace 200 AH of FLA. 

    Keep in mind that the Lithium batts charge up faster than FLA and the Lithiums are just as happy at partial charge than at full charge. 

    Best of luck with your project. 

    Building Off-Grid in Terlingua, TX
    14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048, Mini PDP, MPPT 80-600, SCP. 3 - Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries
  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Are you going to "build your own batteries" out of raw cells and install your own BMS (battery management system)? With this type of system, the cells are generally connected in parallel then in series... that way the BMS only has "one set of sense leads" per "parallel group of cells).

    There are folks that run "naked" Li Ion cells (no BMS)... But I would suggest that you don't do this. The //BMS is there as a last resort to prevent over current/over or under voltage/etc. from damaging or ruining the cells.

    I guess you are going to use LiFePO4 chemistry (lithium Iron Phosphate) or similar? These cells do not store as much energy as the same size Li Ion banks based on other chemistries... But Lithium iron phosphate batteries are on of the "safer" types (generally, almost impossible to set these cells on fire).

    If you are going with "all in one" batteries (i.e. 12 volt with integrated BMS)--Then usually you would put them in series (for 48 volts), and parallel for additional AH capacity.

    Make sure you have fuses/breakers on the battery bus. Lithium batteries can output a huge amount of current into a short circuit.

    -Bill "not a battery expert" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • littleharbor2littleharbor2 Solar Expert Posts: 1,756 ✭✭✭✭✭
    rdg 1
     I'm up the road a ways in Northern Baja. I recently switched to LiFePo4 individual cells. I am very happy with them. My bank consists of 16 230ah. cells in a 2p8s configuration. for 460 ah. @ 24 volts nominal.I'm still babysitting Flooded Lead Acid batteries for my neighbors. What a crude and messy form of power storage compared to Lithium. I have some friends using 12 volt, 100 amp hour drop in lithium batteries. They have 6 of them in a 2s3p set up for 24 volts. The issue I have found with their 6 batteries seems to be, while having 6 BMS running in 6 batteries they are getting shut downs of one or more individual batteries, causing full shut down of the whole system. I cant put my finger on why this is happening but it has become a problem while they're gone for the summer. I found I can Jump start the pack by putting 24 volts onto the Outback charge controller and bringing it back to life. That being said, My battery bank of individual cells have not given me one bit of trouble so far. Another benefit to building your own battery bank is it is a lot cheaper.
    Hope this helps in your decision making and isn't making it more difficult.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

  • bajariderbajarider Registered Users Posts: 2
    Weather you build your own or buy a pre-built battery, I would suggest you use a 48volt battery. Putting mutiple batteries /bms units in series is poor practice. The individual bms units cannot communicate with each other and because the current has to pass-through each bms it invites problems like what Mike describes above. BWOE, if you have 4 12v battery in series and are charging and one battery reaches the fully charged limit the bms in that battery will shut down to protect the battery. But this also stops charging to the other 3 batteries in  series.

    Since you have a 48volt system buy 48volt batteries. Ideally ones that have data ports and can communicate with each other to work as a single unit. There are a number of options from wall mount to server rack to stand alone units. I've setup several installations for my neighbors. Some wall units directly from China and now a couple using some batteries from Amazon. All seem to be working as advertised. When my arm batteries die they will be replaced with server rack batteries probably from Signature Solar as they now support closed loop communication with my schneider gear.

    You will want to be sure that you charge controller and inverter settings are correct. 
  • rdg1rdg1 Registered Users Posts: 26 ✭✭
    Thanks to all that replied.

    Wheelman - you have a very nice battery but quite a bit above my budget for a part time home with questionable security.

    BB - I will NOT be building my own battery, lol.  I am thinking of Lithium, (LiFePO4 chemistry), 2-48V 100Ah in parallel, (to start).  That way it is fairly easy to add additional Ah if needed.

    Littleharbor2 - I don't think I want to learn enough about battery construction to feel confident in building my own, (a wise man knows his limitations, hahaha).  That being said, do you think I will have an issue with 2x48 in parallel with both batteries having an internal BMS?  I can see how it would be problematic with 4X12V batteries in series for a total of  48V.

    Bajarider - I agree with your comments concerning possible problems with batteries in series to get up to 48V.

    I am leaning towards the 48V 200Ah setup, (2x48V 100Ah n parallel).  Just need to do a bit more research before writing that check.

    Thanks again for all the great advice and words of wisdom.  This forum never fails to impress me.
  • littleharbor2littleharbor2 Solar Expert Posts: 1,756 ✭✭✭✭✭
    rdg1 said:
    Thanks to all that replied.

    .

    Littleharbor2 - I don't think I want to learn enough about battery construction to feel confident in building my own, (a wise man knows his limitations, hahaha).  That being said, do you think I will have an issue with 2x48 in parallel with both batteries having an internal BMS?  I can see how it would be problematic with 4X12V batteries in series for a total of  48V.



    Since I've yet to pinpoint what is the cause of my friend's battery issue. I really don't know how to answer your question. If your battery's Mfg. says it's OK to parallel two 48 volt batteries then go for it. My friend's battery Mfg. says is ok to series wire and parallel his.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

Sign In or Register to comment.