Solar Battery Management System (BMS) 

Do you have a link

i will like to get this for my 18650 14s 80p power wall, i am running my home whit this. so i will need to run 2 of this BMS on series? oh i am building 14 more packs so i can be on the 20k range what you can recommend ? by the way thank you for your work and jehu for be a O.C.D. Freak! On Building DiY Stuff lol

While it is possible to use two SBMS0 for a 14s 48V setup is not that elegant as there will be two SBMS0 each with is own LCD and is own current shunt both showing almost the same thing. Assuming those are 2Ah cells you will have a 160Ah 51.8V = 8.22kWh pack and that is not particularly large. Even a 20kWh pack can be on 24V as typical charge rate should be around 0.2C for long battery life and discharge is typically less than 0.5C. Since SBMS supports an external up to 500A current shunt that means loads of up to 12kW can be connected. One of the larger systems made with SBMS that I know of is an offgrid setup with a 8s3p LiFePO4 25.6V 900Ah = 23kWh and it has 3x 3000W Victron inverters in parallel for 9000W AC

Hi Dacian :) I have the SBMS 100. Great product, great support. Really smart developer. And this product is built to last. If I remember correctly I think the design was created with a 25 year life expectancy on the hardware. Pretty impressive. Keep up the good work. Thanks.

Thanks for the comment Anthony.

Hello, I think this might be the perfect product for our home. Been looking for a BMS / charge controller with adjustable battery charge voltage cut off. QUick question: if I have a 18650 Battery and I want a 12 v system and limit the charge to 4v for battery longevity, would you recommend running at 3s or 4s set up with this device? Many thanks and wonderful product!

For many / most people generating your own power can be more expensive than the Grid. You will need a huge power wall to run an ALL ELECTRIC home - especially in the winter time when there is no sun for many consecutive days and it is below zero outside. The average home consumes 30 kilowatt-hours per DAY !!!

I know I am kind of randomly asking but do anybody know of a good place to stream newly released series online ?

Also, only gives you 40% of stated Battery Capacity ... And my car would last a lot longer, if I only drove 1 mile per day !

I also recommend using new cells with my PCB kits, where is the confusion?

The ribbon cable ( balance leads ) connects all of the cells, on one battery board in parallel with all of the cells on the adjacent battery board...

Thanks for supporting the Solar BMS project. I recommend using LiFePO4 as those will be more cost effective over the life time in off grid type applications. LiCoO2 make sense if you are interested in a portable system as they have higher energy density but they will have higher cost amortization due to lower cycle life.

Thanks, yes, that was in my mind, but as I may find a lot of used 18650 by my job, I might go for this opportunity instead. Currency is becoming rare this days ... and I have plenty of time.

The passive cell balancing system used in the SBMS is the most advanced possible and can keep in balance a battery as high as 100kWh in capacity. Same type of cell balancing is used on all commercially available EV's including Tesla and their huge packs are perfectly balanced.

@@electrodacus There's really no point in keeping a pack in balance using a passive balancing system while the battery pack is in use since you'll get the exact same capacity out of the pack (assuming you are still using a monitoring system) regardless of whether the balancing algorithm runs (unless the cells are BADLY out of balance). A passive balancing architecture just burns off useful energy as heat. Unless you use an active balancing architecture, you really only need a battery monitoring system and manually top/bottom balance a pack every one or two hundred cycles or when the monitoring system reports that two different cell-layers are bottle-necking charge and discharge. A passive balancing system that can keep large packs in balance by voltage is wasting money on superfluous power MOSFETs and the associated thermal management. To get the most out of a battery pack without an active balancing architecture, top balance the pack and stop discharging when one cell-layer hits 3V (or 2.8V for LiFePO4). If manually balancing the pack at any point in its lifetime is not an option, that's when a passive balancing system that only runs during charging would be needed (in which case, the unit manually top balances the pack every charge cycle, but it has all the time in the world to top balance, so it wouldn't need excessively large power MOSFETs and thermal management). Honestly, the resources required for a sophisticated passive system could be used to make a sufficient active system, just add a flyback transformer and isolated mosfet drivers.

I had a 100Ah 8s GBS LiFePO4 battery and used that for 4 months with the SBMS but cell balancing disabled. Battery started perfectly top balanced and after 4 months of normal offgrid usage about 50% of battery capacity used every day the cells where 2Ah out of balance meaning than when the highest cells was fully charged the lowest cell needed additional 2Ah to get fully charged. So basically 2% of battery capacity was lost over 4 months of normal use or around 0.5% per month. Now if the cell balancing will have been enabled on SBMS then charging will have been done just during the day when charge current was above 1A that is most of the day as more than that will typically get in to battery while charging. Now the cell balancing is around 150mA so that means all all energy for cell balancing comes from PV panels directly and not from battery so cells that are higher and need balancing will see a charge current that is 150mA smaller than the other cells so no energy is extracted from any battery. Say charge current is 10A then some cells will see full 10A and the higher cells will see 9.85A. Based on the GBS example the cells will only need about 3 to 4h of cell balancing over a full month to be maintained fully balanced. All that energy "wasted" for cell balancing that will not be much is directly from PV panels so say the 0.5Ah per month for the 100Ah battery means say 24V x 0.5Ah = 12Wh /month that will be 144Wh over a year and say over 10 years that will be 1.44kWh and at a just 2 cent/kWh cost amortization for PV panels that will be around 3 cent total over 10 years period (actually nothing as there will be plenty of excess energy from PV in an offgrid application). While this 2.5kWh is a small battery even a 2.5kWh will only cost 30 cent in wasted energy over 10 years period and you will not want to manually balance your pack energy few months for less than $1 in 10 years :) You will also need that energy when you do the manual cell balancing so not even a few cents of savings. Same will be the case for anything other than restive cell balancing (it is just not economical).

Both

kit.com/jehu/jehu-s-diy-powerwall-pcb-project

Yes SBMS will start to balance when two conditions are meat. One is a minimum charge current about 400mA for SBMS40 around 1A for SBMS120 and SBMS0 will depend on external current shunt ans settings and the second condition will be a delta of at least 10mV between cells. This way cell balancing can be done for up to a few hours each day allowing a small cell balancing current to keep in balance even very large battery packs 20kW to 100kWh are not problem for SBMS. The above are just default settings user can chose to have cell balancing at any delta between cells and even do cell balancing during discharge (not that will be very useful in many setups).

You connect many batteries in parallel

@@jehugarcia I see, tyvm.

If each BMS does only 100 Amps then you would design three different 4S1P batteries and then connect those three batteries in parallel using 3 @ 100 AMP FUSES ...

Yes it can handle 3s that is the minimum configuration but anything between 3s and 8s is possible.

electrodacus , thanks I’ll go for a 120A, my rv diy is a 240amph 👍🏻👍🏻

You also need to now that PV panels need to match the battery voltage so just 32 or 36 cell panels will work efficient with 3s or 4s

@@electrodacus Ill go for the 40A So, my 2x100w solar pannel system will work if understand. In an other way ..can we imagine to use it too, with an other dc input like the engine alternator 14v..? My 3s battery is a 12.6 v max

Yes your 2x 100W will work with a 3s and SBMS40. Since your battery is 240Ah you can maybe add more panels in the future up to 6x 100W with SBMS40. Is not economical at all to use the alternator as a source of charging the battery as it is very expensive. Pv panels have a cost amortization as low as 2 cent/kWh over their lifetime but each kWh you get out of your alternator will cost you at least 1 liter of fuel that will be at least around $1/kWh. So if you drive your vehicle will use about 1 liter more of fuel for each kWh you get out of the alternators it is the same idea as using the air conditioning increases the fuel consumption as it is adding more load to the motor. Even if you do not care about the cost you will need something like a battery to battery charger as that will know when engine is off not to charge your lithium battery and drain the small starter battery and also limit the current else alternator will push as much as possible and get damaged from overheating as it was designed for charging just a small Lead Acid starter battery.

While it is not elegant and normally do not recommend two SBMS0 can be used in series for a 48V system. But a single 7s 24V with up to 500A will allow for 12kW max size inverter and not sure how many will need more than 12kW.

No ...

No bms usually only balance once any cell hits 4.3v

@@jehugarcia have you tried smart BMS before.? do undervolting or can i set 4 volts on max voltage settings. ?

Any number of parallel cells will be no different from a single large capacity cell so if your system will be 24V so 7s with those sort of cells then just one SBMS will be needed likely you will want the new low cost SBMS0

@@electrodacus Thank You very much for your response AND advice. Looking forward to the future of your product.

Huh ?

Not likely

Usually no, but it all depends upon how each one functions ...

The SBMS is not PWM as constant voltage charging is not desired or needed with Lithium in stationary offgrid applications. The new low cost SBMS0 can be used for a 14s or 16s system but is not very elegant to have two SBMS0 so I do not normally recommend this. Most people will be happy with a 24v system as the 500A max current shunt allows for 12kW loads and that I think is fairly high and should be good for 95% of people.

WHY?

Safety ...

www.kickstarter.com/projects/electrodacus/solar-bms-and-digital-mppt-for-pv-electricty-and-h electrodacus.com/

there is a card there

@@poiiihy Now there is. It wasn't earlier.

3s-8s I don’t know much of the Prius pack

Yes it will work with a 6s Tesla module but that is not a 24V module just a 22.2V nominal so you will only be able to use the totp 30% or so of the capacity because most 24V inverters will shut down around 21V to 22V so you will need to find an inverter that can be set to use lower voltage at least able to handle 20V in order to use more of the available capacity or if you just use DC loads that are happy with as low as 20V then that will be fine.

the higher end Magnum inverters say they will go as low as 18v. Haven't used one yet, but I will on my next project with 6S tesla modules.

What model of Magnum ? As most of their inverters will not work with lithium as they do not provide a remote ON/OFF port to integrate with a BMS. Victron, Cotek, PIP2424 and a few others support a BMS and so can work with Lithium batteries.

@@electrodacus It looks like their MS (MS4024 etc) and RD series inverters all support the lower voltages required for 6S tesla modules to have full capacity available. You would know better than I do, if they support your devices. I don't own one yet and haven't looked in to much detail. For me personally, on/off control is not necessary. These inverters can be set to whatever LVD voltage you prefer to protect your batteries. And any high quality charge controller can be set to stop charging at whatever voltage you choose. I have been running my Off-grid system like this for two years. I'm using all Schneider gear with my 10 7S modules. Admitedly the charge controllers aren't made for lithium, but they get the job done. The batteries have remained balanced, so active balancing isn't really what I'm looking for. I do want a bms that keeps an eye on the balance and disconnects the battery to prevent catastrophic failure (fire) if for some reason the charge controller fails to stop or one string does get out of balance and might discharge to low.

A lithium battery needs a BMS and LVD protection is done based on the lowest cell voltage say 3V for those Tesla /Panasonic NMC cells and the total pack voltage has no relevance. If the inverter has no support for remote ON/OFF so that a BMS is able to turn off the inverter when the lowest cell gets to LVD then it can not be used with a Lithium battery. The MS4024 is an extremely old design and can only work with Lead Acid batteries as it has no simple remote ON/OFF for a BMS and has no simple way to DIY that as they decided to use a momentary switch for ON/OFF instead of traditional mechanical ON/OFF switch. As for most inverters that include all Victron and Cotek that remote ON/OFF port is nothing more than two wires in parallel with the ON/OFF switch and then the switch is left on the OFF position and then the BMS with just a simple optoisolator will turn the inverter ON by shorting those two wires that are at battery voltage level say 24V and shorting them will result in a 10mA or so current. Same is true for any charger you will want to use the BMS will need to have ON/OFF control of that so it can turn it off. Not many charger have that option but the new Victron SmartSolar MPPT have that remote port and is compatible with SBMS. Running a Lithium battery without a BMS is just asking for problems and I know my word is less valuable as I design and sell the SBMS but it is still true. So the main idea is that LVD and HVD on Lithium is based on lowest or highest cell voltage and the pack voltage is useless and only works for Lead Acid. Cells will always drift without active cell balancing and while having a BMS will still protect the pack you will need to do manual cell balancing at least every few months so is not worth the trouble when the cell balancing circuit cost almost nothing. I had run my 8s 24V 100Ah GBS LiFePO4 battery for 4 months with cell balancing disabled and by the end of the period there was a 2Ah delta between the lowest and highest cell so about 0.5Ah per month or 0.5% per month capacity loss due to unbalanced cells. Batteries are expensive compared to a BMS so is just not wort damaging the battery just to save a small amount on a BMS. The SBMS0 is 120USD and has cell balancing (can keep even a 100kWh battery balanced) and is also a energy monitor so it calculates the SOC accurately so you know how much energy you have left and also has an energy counter so you know how much energy you got out of battery every day and also over the life of the system (that is separate and permanent even if battery is removed).

Charge controller + BMS is a pretty decent value, but as just a BMS, I agree.

More? Some money

@@jehugarcia there is a crazy merchandising behind this, but very little science

i want electric tracter for agriculture pupose . i am from india help me.

No comment 😖🤢

Nope

It is cool that Rich put that out there for everyone to see. It looks like the only real way to have a catastrophic failure is to overcharge them. And I was thinking the same ;^)