Monitoring LiFePO4 Lithium Batteries

[ele2014]

Hi All,

Not sure what happened with my first post was probably because of the photo or because it was first post.
Anyway it was about Solar BMS SBMS4080 that is my design an you may want to know about that.
I designed that for my offgrid house but it will probably work great for boats.
Just seach for Solar BMS on google and you will get to my youtube channel.

I will not include a photo since that was probably the reason my first post was not listed.


PS: It seems it works now so the photo was the problem.
This Solar BMS is almost a replacement for the 12V / 24V solar charge controllers used with Lead Acid batteries just that this one is designed for 3 up to 8 cells of LiFePO4.
I needed to design this since there was nothing like this on the market and realy needed for my offgrid house.
I live offgrid since last year and use a 2.5KWh LiFePO4 GBS battery (8 cells 100Ah)
I charge them from 3x 240W solar panels and a small 300W wind turbine.
Monthly energy consumption is between 60 and 90KWh most of that usage is during the day directly from the solar panels for cooking just the difference is provided by the battery.
My Solar BMS is under development in Betta stage there is a 30 minute video about on my youtube channel. I only have one sample so for now I charge the batteries without a BMS and manually check them every time.
They do not get imbalanced much less than 1% / month because of the low charge discharge rates.
But the worst part is not knowing the SOC that will be solved when the Solar BMS will get installed.
You get more technical details if you search for the Solar BMS or use the links in my signature.
I will be happy to answerer any questions related to LiFePO4 battery charging or Solar BMS.

[campr]

Wow, cool. Do you think 2 of them could work safely in parallel?

Sent from my Nexus 7 using Cruisers Sailing Forum mobile app

[Maine Sail]

Originally Posted by electrodacus

Hi All,

Not sure what happened with my first post was probably because of the photo or because it was first post.
Anyway it was about Solar BMS SBMS4080 that is my design an you may want to know about that.
I designed that for my offgrid house but it will probably work great for boats.
Just seach for Solar BMS on google and you will get to my youtube channel.

I will not include a photo since that was probably the reason my first post was not listed.


PS: It seems it works now so the photo was the problem.
This Solar BMS is almost a replacement for the 12V / 24V solar charge controllers used with Lead Acid batteries just that this one is designed for 3 up to 8 cells of LiFePO4.
I needed to design this since there was nothing like this on the market and realy needed for my offgrid house.
I live offgrid since last year and use a 2.5KWh LiFePO4 GBS battery (8 cells 100Ah)
I charge them from 3x 240W solar panels and a small 300W wind turbine.
Monthly energy consumption is between 60 and 90KWh most of that usage is during the day directly from the solar panels for cooking just the difference is provided by the battery.
My Solar BMS is under development in Betta stage there is a 30 minute video about on my youtube channel. I only have one sample so for now I charge the batteries without a BMS and manually check them every time.
They do not get imbalanced much less than 1% / month because of the low charge discharge rates.
But the worst part is not knowing the SOC that will be solved when the Solar BMS will get installed.
You get more technical details if you search for the Solar BMS or use the links in my signature.
I will be happy to answerer any questions related to LiFePO4 battery charging or Solar BMS.

Can you please explain how this device deals with multiple charge sources, solar, wind, alternator, hydro, AC shore charger, some to 200A+..

Can it drive external HVC or LVC warning level relays plus a main bank isolation relay?

Can it be set up for a load bus (LVC) and charge bus (HVC) ?

It appears all "loads" are being run through the BMS? Is this an accurate interpretation?

If so how does it deal with starter motors, windlasses & bow thrusters... Some of these devices have in-rush currents into the four figures and 400A +/- short duration loads....

I read through everything but how it works, what it does, why it does it this way or that, and how it is wired into the system is not well documented. Perhaps I missed something?

[campr]

I've had a look at the kickstarter now, and a couple of things grab me as an issue:

• The project is only a dev board (i.e. there are no guarantees for it working right).
• I cannot see any additional outputs for switching HVC and/or LVC bi-stable relais, but the hardware design is open source, so you could add them. I expect it would switch off the load at a certain low-voltage point, and stop charging when Vmax is reached.
• I cannot see any way of them running in parallel, but I guess that functionality could be added by daisy-chaining them together and the units electing a 'master' who would do the cell-balancing, again, no ports for this brought out. This would also allow for increased loads.
• It is unclear to me as to which development environment is being used.

So in conclusion: It's not a commercial product, and for hacking it's use is limited because of the limited amounts of connections to be made to the outside world (for daisy-chaining or controlling relays for HVC and LVC).

[ele2014]

I will try to answer again since I made an answer (long and detailed) and included a link to a photo and was not published because of that.

The Solar BMS has a optically insulated serial port so is able to communicate with external things like a computer another BMS smart relay.

You can see this solar BMS exactly like a 12V / 24V Lead Acid solar charge controller everything is integrate in one box it just works with Lithium batteries.

It has 10x 20A connectors in front and multiple are used for current sharing since the PCB will not be able to take more than that from a single point.
First two are positive for the solar PV panel so max 40A next 4 are for Battery and last 4 are for load max 80A all just positive terminal the negative terminal is connected outside and common for battery PV and load.
Then there is on the right a 6 pin connector with 3 pins for insulated USART port (serial communication) then 3 pins for external temperature sensor.
Next is a 10 pin connector for individual cell monitor and balancing.

You can use multiple Solar BMS in parallel on one battery but then SOC will not be correctly calculated unless I make one master the other slaves and the slaves send the charge and discharge data to master (not implemented at this moment)

For my use with 24V battery 8s LiFePO4 1000W solar PV and 2000W load is enough.

Yes this is not a commercial product it was done because there is nothing like this available and I need for my offgrid house.
I worked as an HW engineer in R&D for Siemens Automotive for a bit over 6 years is a decently made unit.
Also there is a main IC that takes care off all things related to battery including overcurrent protection and SC the only thing I do is add an ARM cortex M0 microcontroller capacitive touch buttons and a graphic LCD to display the data form the main battery IC (individual cell voltage and current) and program the main IC with custom parameter over 30 parameter including current limits and battery voltage thresholds.

Probably the best way is to watch my youtube video is a 30 minute one explaining the hardware and software functionality.

And as for input it can accept anything that is constant current limit to less than 40A that includes solar PV panels a CC charger no wind turbine since that need electromagnetic breaking and that is not implemented.
The load overcurent protection is set at 96A for one second default(time can be changed in seconds) and short circuit is set to 128A 200ms can be changed to 196A if necessary to work with inductive loads.

Hope I answer most of the question and I can post this.

[sparrowhawk1]

Hey Maine sail, I followed your link to the mini BMS and the controller and I know you do this professionally so probably don't want to go into too many details about the exact wiring but can you tell me where I can get a solenoid to disconnect for high voltage and one for low voltage or does the controller do that? and if anyone can provide info on how to connect it all up it would be much appreciated. Thanks again. And what do you think of the BMS made by EV power? Seems like a neater installation to me

[senormechanico]

Here's a 12 volt / 100 amp relay which ought to work for you.

Intellitec 01 00055 100 Amp Battery Disconnect Relay New | eBay

[sparrowhawk1]

Thanks. I just reread all the posts on this thread ( my brain hurts) and see that main sail is using a 70 amp DPDT relay for balmar and solar HVC. But I need a link to research it. I currently have a 1000 watt inverter but was thinking in the future I might get a 2000 watt pure sine. With all my solar and the better batteries I would like to be able to use extra electricity produced to cook with.

[svAricia]

Not sure why CruzPro is not being mentioned anywhere, I have their VAH110 battery monitor with amphour counter and alarm/generator start, plus NMEA 0183 output.
I am planning to use it for my new LifePO4 bank.

CruzPro VAH110 Three bank digital Volts/Amps/Amp-Hour Monitor

[sparrowhawk1]

Originally Posted by svAricia

Not sure why CruzPro is not being mentioned anywhere, I have their VAH110 battery monitor with amphour counter and alarm/generator start, plus NMEA 0183 output.
I am planning to use it for my new LifePO4 bank.

CruzPro VAH110 Three bank digital Volts/Amps/Amp-Hour Monitor

Thanks. I didn't see a price on the linked page. I can afford the batteries but it looks like all the monitoring and balancing and shunting devices and switches are going to put it out of my budget. But I will continue to spend a couple hours each day researching.

[svAricia]

Originally Posted by sparrowhawk1

Thanks. I didn't see a price on the linked page. I can afford the batteries but it looks like all the monitoring and balancing and shunting devices and switches are going to put it out of my budget. But I will continue to spend a couple hours each day researching.

I think the price is $328 which includes 450amp shunt, I got it on special for $199 if I remember correctly. You'll also need BMS like the HousePower mentioned earlier.

[s/v Thea]

Sparrowhawk1,

I use the mini BMS, the one built for EV vehicle conversion. It didn't cost much (compared to the batteries). You require a signal (equivalent to ignition switch on vehicle) so board knows to expect LVC or HVC. I used voltage relay for this, you could also use this relay to enable either your charging or discharging solenoid so LVC cuts out discharge and HVC cuts out charging solenoid.


Doug

[sparrowhawk1]

Originally Posted by s/v Thea

Sparrowhawk1,

I use the mini BMS, the one built for EV vehicle conversion. It didn't cost much (compared to the batteries). You require a signal (equivalent to ignition switch on vehicle) so board knows to expect LVC or HVC. I used voltage relay for this, you could also use this relay to enable either your charging or discharging solenoid so LVC cuts out discharge and HVC cuts out charging solenoid.

Doug

Exact models, prices, where you purchased and how exactly its wired up would be greatly appreciated

[SnowT]

I think I saw that someone wrote that they can afford the batteries, but can't afford the systems to run the batteries properly..

- I don't think they have had a look at the long term benefits of good overall system..
Price wise the end reward is a system that will out live any LA system by 2-3 times the LiFePO4's.

the cost of a monitoring system is not that expensive.. when you compare it to life span of the batteries..

Juergen

No I will not tell how I'm doing my batteries..

[sparrowhawk1]

Originally Posted by SnowT

I think I saw that someone wrote that they can afford the batteries, but can't afford the systems to run the batteries properly..

- I don't think they have had a look at the long term benefits of good overall system..
Price wise the end reward is a system that will out live any LA system by 2-3 times the LiFePO4's.

the cost of a monitoring system is not that expensive.. when you compare it to life span of the batteries..

Juergen

No I will not tell how I'm doing my batteries..

That was really helpful