Best DIY 48V Lithium setups and sources right now?

[davidshelton]

So my AGM's are a couple of years old now and I want to donate them to a community project in the area so I am thinking about taking the leap with Lithium so I can learn about the tech before selling systems for my customers. I would like to get about 6-8kWh useable out of them and we'll be giving offgrid living a shot. I have just started researching options. Our energy needs average 4-6kWh daily so pretty small system. I will use the grid as a backup and I also have my trusty Honda gennie just in case. I mostly install Midnite Solar and Outback product and don't plan on changing my system much except for adding some PV.
I would love your thoughts and advice for sourcing a DIY setup from the US.
cheers!

[mike90045]

>   I would love your thoughts and advice for sourcing a DIY setup from the US.

I would not do DIY Li battery setup.  I don't have the patience to babysit them, and the few DIY BMS systems that exist, don't inspire me.

[davidshelton]

Doing some more research, it seems CALB cells are a fairly low cost way to go. I am not about to be making up hundreds of 186500 batteries even with a kit nor even striping down old laptop batteries and then building packs from the good cells and adding balancers and BMS etc etc. So I am already not DIY but don't want to pay the premium for a pretty box aka integrated solution.
So far Electriccarpartscompany.com seems to have good pricing on the cells. Not sure about the balancers or BMS. I am definitely looking for something reliable as I have to wait for weeks if not months to ship replacement parts down so I need a reliable BMS and a spare on hand.

[ClassicCrazy]

Doing some more research, it seems CALB cells are a fairly low cost way to go. I am not about to be making up hundreds of 186500 batteries even with a kit nor even striping down old laptop batteries and then building packs from the good cells and adding balancers and BMS etc etc. So I am already not DIY but don't want to pay the premium for a pretty box aka integrated solution.
So far Electriccarpartscompany.com seems to have good pricing on the cells. Not sure about the balancers or BMS. I am definitely looking for something reliable as I have to wait for weeks if not months to ship replacement parts down so I need a reliable BMS and a spare on hand.

Go to main page and do a search for lithium and or Calb batteries.  There have been some detailed discussions in the past on using those and various charging schemes. I tried bottom balancing with no other protection and don't recommend that . It might work with some other safety measures. Seems like there have been various BMS solutions over the years so you will have to do some careful study to figure out what is available.  Read up on the discussions and that will give you a lot of information . 

There are ready made lithium packs with all the BMS built in available now too .

Larry

[RossW]

Seems like there have been various BMS solutions over the years so you will have to do some careful study

I've been using LFP for 4.5 years now and really happy with the entire setup.
Well before I even got the lithium, I built cell monitors that show me exactly what each cell in my battery is doing.
I consider "monitoring" perhaps the single most important thing you can do to any battery bank, not just lithium. Spot a developing problem early and fix it rather than have to deal with the consequences of a failure later.

With whatever form of cell balancing you choose to use (including none!), cell monitoring gives you the continuous confidence everything is ok.

I run all my loads through an inverter, so the LVD in the inverter is my "failsafe" against over-discharge.
Automatic generator start by the inverter, if battery volts or SoC ever get low (but still well before the LVD) means I've never got close to disconnect, and as such I consider a battery management system with LVD more of a liability than a benefit.

My charge sources all have a capped high voltage that is below the safe limit of the pack.
I have an alarm should voltages get close to that. It's only gone off once, and that was due to a deliberate act to test it.

I consider a battery management system with HVD more of a liability than a benefit too! (in my installation anyway)

I have 900AH @ 52V (around 40kWh of usable capacity) in my bank and am super happy with every aspect of them.
(I do have suitable HRC DC fuses in each bank as the ultimate disaster protection)

[Matrix]

Check with mcgivor  and Raj174 over at Northern Arizona Wind & Sun Solar Forum.  I believe they are both doing something similar to what you are wanting.

http://forum.solar-electric.com/discussion/353773/instalation-up-and-running#latest

[davidshelton]

Seems like there have been various BMS solutions over the years so you will have to do some careful study

I've been using LFP for 4.5 years now and really happy with the entire setup.
Well before I even got the lithium, I built cell monitors that show me exactly what each cell in my battery is doing.
I consider "monitoring" perhaps the single most important thing you can do to any battery bank, not just lithium. Spot a developing problem early and fix it rather than have to deal with the consequences of a failure later.

With whatever form of cell balancing you choose to use (including none!), cell monitoring gives you the continuous confidence everything is ok.

I run all my loads through an inverter, so the LVD in the inverter is my "failsafe" against over-discharge.
Automatic generator start by the inverter, if battery volts or SoC ever get low (but still well before the LVD) means I've never got close to disconnect, and as such I consider a battery management system with LVD more of a liability than a benefit.

My charge sources all have a capped high voltage that is below the safe limit of the pack.
I have an alarm should voltages get close to that. It's only gone off once, and that was due to a deliberate act to test it.

I consider a battery management system with HVD more of a liability than a benefit too! (in my installation anyway)

I have 900AH @ 52V (around 40kWh of usable capacity) in my bank and am super happy with every aspect of them.
(I do have suitable HRC DC fuses in each bank as the ultimate disaster protection)

Thanks for the detailed response! What was the SOC range you could play in without any individual cell reaching a critical low or high voltage? Did just using balancers keep the pack working together in harmony? Setting the LVD of the inverter within the bottom end of the operating voltage range good enough?

[RossW]

Depending on the day - we're a month into spring now, and if we've had a decent day previously, my banks are down to about 80% SoC at sunrise and back in float by around 10am. As the days get longer and the nights get shorter that gets even better.

A couple of overcast days sees the batteries getting down a bit. I had to start the generator the other day because I was going interstate for the day, batteries were down to 40% at 6am and I had doubts we'd get any useful sun - and I'd just made modifications to the generator on the weekend so wanted to be here when (if) it had to run. Ran the genset for an hour, brought the bank back up to 53% before I left. Of course we had enough sun then to have reached full charge during the day and I need not have bothered.

The inverter will autostart the genset at 30% SoC or 48V (3.0V per cell), both well within what I'd call "safe" limits. It's only done that a few times in the last 18 months, and has worked flawlessly.

I have simple balancers that maintain equal cell voltages all the time (not just "top-of-charge balancing"), and monitor their state to remain confident everything is doing as it should.

[mike90045]

....Ran the genset for an hour, brought the bank back up to 53% before I left. Of course we had enough sun then to have reached full charge during the day and I need not have bothered......

Wife calls the generator "Cloud Repeller"  If not raining, clouds usually clear 20 minuets after starting it up !

[ClassicCrazy]

....Ran the genset for an hour, brought the bank back up to 53% before I left. Of course we had enough sun then to have reached full charge during the day and I need not have bothered......

Wife calls the generator "Cloud Repeller"  If not raining, clouds usually clear 20 minuets after starting it up !

Ha ha - yeah  - often works that way doesn't it !

Larry

[Gavin]

Seems like there have been various BMS solutions over the years so you will have to do some careful study

I've been using LFP for 4.5 years now and really happy with the entire setup.
Well before I even got the lithium, I built cell monitors that show me exactly what each cell in my battery is doing.
I consider "monitoring" perhaps the single most important thing you can do to any battery bank, not just lithium. Spot a developing problem early and fix it rather than have to deal with the consequences of a failure later.

With whatever form of cell balancing you choose to use (including none!), cell monitoring gives you the continuous confidence everything is ok.

I run all my loads through an inverter, so the LVD in the inverter is my "failsafe" against over-discharge.
Automatic generator start by the inverter, if battery volts or SoC ever get low (but still well before the LVD) means I've never got close to disconnect, and as such I consider a battery management system with LVD more of a liability than a benefit.

My charge sources all have a capped high voltage that is below the safe limit of the pack.
I have an alarm should voltages get close to that. It's only gone off once, and that was due to a deliberate act to test it.

I consider a battery management system with HVD more of a liability than a benefit too! (in my installation anyway)

I have 900AH @ 52V (around 40kWh of usable capacity) in my bank and am super happy with every aspect of them.
(I do have suitable HRC DC fuses in each bank as the ultimate disaster protection)

Hey RossW wanted to thank you for the post - I am brand new to home solar - bought a cottage with an off grid  Midnite system of 24V with a gen backup. Currently using LA but I have a 10 year old (1974) Dodge Dart which is powered by about a 30kw (50x180AH) lithium pack. I bottom balanced the cells a couple times and don't overcharge so never an issue. Have been thinking of replacing the lead acid with my lithium pack at cottage and going to ICE in the Dart. Seems the solar set up already has a charging high voltage cutoff and a low voltage GEN start point so not sure there is any real need for any other BMS system. I certainly have never needed it in my car. The cells can each be overcharged past 10v before there is an issue (now this from fooling around with individual cells) and on discharge they merely die if over discharged.

Any advice from someone actually using Li would be appreciated.

[ClassicCrazy]

I would at least put some low voltage cutoff protection on your lithium . I tried bottom balancing some lifepo4 with no other protection. It was an experiment and to learn but I made some mistakes. Putting individual cell monitoring would be very decision - I probably would not have had the problems I had if I'd been doing that.

Larry

[Matrix]

It seems to me that this whole Lithium Battery idea should be getting of age enough that there are some reputable commercial BMS systems to chose from.  When will (or has any reputable company) started marketing a BMS or various BMS options so that one could skip the whole DIY route?   I would not be confident making my own or contacting a Chinese manufacture to make one up to my specs,  but I would have no problems following directions.

I also see Trojan has jumped into the market,  but I have not heard much buzz about them.

[ClassicCrazy]

There are lots of BMS these days on Aliexpress. Depends what voltage and current you need.
Here is one type
https://www.aliexpress.com/item/8S-24V-lifepo4-bms-waterproof-same-port-with-balance-18A-25A-35A-45A-60A-discharge-current/32873151474.html?spm=a2g0o.cart.99999999.259.49883c00oZk5OG

Or this one
https://www.aliexpress.com/item/8S-to-24S-Lifepo4-li-ion-Lithium-Battery-protection-70A-100A-150A-200A-300A-smart-bms/32962595842.html?spm=2114.search0604.3.29.1acf2612yAmLbn&ws_ab_test=searchweb0_0,searchweb201602_3_10065_10130_10068_10890_10547_319_10546_317_10548_10545_10696_453_10084_454_10083_10618_10307_537_536_10059_10884_10887_321_322_10103,searchweb201603_16,ppcSwitch_0&algo_expid=3eb8c1c3-71fd-42e0-adb6-af0d8d55833d-4&algo_pvid=3eb8c1c3-71fd-42e0-adb6-af0d8d55833d&transAbTest=ae803_5

Larry

[Matrix]

But would those be considered Reliable and Safe over time.  Especially if left unattended say at a cabin.  Perhaps I am over thinking it and any simple BMS would pretty much suffice.  I am not ready for Lithium just yet,  but wanting to wrap my head around it because it seems some other chemistry besides LA is going to be in my future (probably in a lot of folks futures).