BMS design for boats

[Goboatingnow]

View attachment 114943
Hope this block diagram is visible note it’s not electrically perfect

This bms is based on a battery by battery basis in this case each battery is 4 series cells resulting in a nominal 12v 100Ah battery

The bms has a high side mosfet disconnect and uses an ATTINY connected to a dedicated analog front end. ( there are several haven’t finalised one yet. ) these chips handle the large common mode voltage of the series series

Some things are omitted. The current is sensed using the Vds drop across the mosfets ( bidirectional mosfet switch. ) however I could equally use a simply sense shunt as some front ends have a shunt reading ability.

The mosfets are high side so the system ground remains intact so comms can continue even post mosfet disconnect

A haltek switched capacitor active balancer is present running under the ATTINY control. This prevents balancing until the upper knee voltage is approaching.

Each cell has voltage sensing to 1mV accuracy and temperature measurement per cell.

A wired OR fault and alarm lines run between each BMS per battery. Alarm is a pre warning of impending disconnect and fault Indicates disconnect.

As can be seen each battery unit is connected to a ESP32-C3 ( RISC V) based communications monitoring unit. This communicate to the bms modules via LIN bus which is a simple serial system. The esp polls each bms and equally monitors the fault and Alarm lines.

The comms module has CAN WIFI and Bluetooth supporting potential connections to Victron VE.CAN or Bluetooth setup apps. It’s intended that charge and load commands would be issued over CAN. But equally dedicated IO lines could be provided if needs be to allow selective load disconnect strategies or charge start stop.

I’m working on this project post Christmas as I’m currently designing a new alternator controller

 

[Goboatingnow]

I’m aiming at packaging it in something like this per battery.

 

[56knoise]

Very cool. I had no idea that the attiny could do hardware i2c using its USI bus.
So the idea is each BMS is connected to the same LIN bus and a single ESP32 serves as the master for however many batteries/BMS's are in your battery bank?

 

[Goboatingnow]

Very cool. I had no idea that the attiny could do hardware i2c using its USI bus.
So the idea is each BMS is connected to the same LIN bus and a single ESP32 serves as the master for however many batteries/BMS's are in your battery bank?

3 -4 parallel batteries in the bank 12v at approx 350-400Ah total

 

[Goboatingnow]

Very cool. I had no idea that the attiny could do hardware i2c using its USI bus.
So the idea is each BMS is connected to the same LIN bus and a single ESP32 serves as the master for however many batteries/BMS's are in your battery bank?

Yes that’s it. Each battery can act in dependantly but the whole system also works together

 

[rgleason]

Very Nice. Wish I understood it all.
I was going to send you a new TI Lin based Alternator Regulator microchip link, but I deleted it and can't find it in the recycle bin.

Maybe this was it, but I thought it was TI.

The LIN serial interface is used by the engine control unit (ECU) to transmit charging voltage set point from 10.7 V to 16 V, load response control ramp and cut-off speed and the field excitation limit. The voltage set-point command can also disable the field driver for a momentary no-output condition.

Signals transmitted to the ECU from the regulator include field excitation duty cycle, current or temperature (customer-defined) and the fault status. Transmitted fault codes provide unique indication for mechanical, electrical, temperature, communication and timeout errors. In addition, the LIN-controlled alternator-regulator includes short-circuit protection, EMI and ESD suppression and consumes less than 200 µA standby current.

 

[Goboatingnow]

I reviewed all the current crop of alternator regulator ICs , Infineon , IR , NXP and ST micro. Wasn’t aware of a TI one.

I have good contacts with engineering support in STmicro so went with them. They only release full data sheets on this device after signing an NDA!!

I disregarded non LIN units as they are not easily controlled by a micro controller.

This is not first alternator controller. I started by building the open source precursor to the wakespeed 500 http://arduinoalternatorregulator.blogspot.com/?m=0 ( use a PC not a mobile browser)

In fact if you want you understand how the wakespeed developed follow this as the WS5000 grew out of this project.

I built this but I wasn’t happy with the huge software dependency.

The advantage of using say the ST L9918 is the chip will function independently of the micro. But the micro can change the on going set points retrieve monitoring data etc.

But now as I said my focus is changing to wifi connectivity. How that fits into my system architecture remains to be determined.

 

[rgleason]

I reviewed all the current crop of alternator regulator ICs , Infineon , IR , NXP and ST micro. Wasn’t aware of a TI one.

I have good contacts with engineering support in STmicro so went with them. They only release full data sheets on this device after signing an NDA!!

I disregarded non LIN units as they are not easily controlled by a micro controller.

This is not first alternator controller. I started by building the open source precursor to the wakespeed 500 http://arduinoalternatorregulator.blogspot.com/?m=0 ( use a PC not a mobile browser)

In fact if you want you understand how the wakespeed developed follow this as the WS5000 grew out of this project.

I built this but I wasn’t happy with the huge software dependency.

The advantage of using say the ST L9918 is the chip will function independently of the micro. But the micro can change the on going set points retrieve monitoring data etc.

But now as I said my focus is changing to wifi connectivity. How that fits into my system architecture remains to be determined.

No kidding! I was following the development too and thought Al should also make a BMS at the time. Then I saw one of the Gen3 for sale and actually purchased it for very little. ..Still using a Balmar ARS-5 though.

Very interesting about the regulator work.

 

[Padzb]

Each cell has voltage sensing to 1mV accuracy and temperature measurement per cell.

What are you using to measure cell voltage please?

 

[Goboatingnow]

What are you using to measure cell voltage please?

Imstrumrbtion amp and 14 bit adc

 

[Padzb]

Imstrumrbtion amp and 14 bit adc

Ta, was actually interested which ADC. ads1115 have been great onboard so far for other stuff, just interested what others use

 

[Goboatingnow]

Ta, was actually interested which ADC. ads1115 have been great onboard so far for other stuff, just interested what others use

Latest design is ATmega406 based

 

[Padzb]

Latest design is ATmega406 based

so your using the interal atmega ADC?

 

[Goboatingnow]

so your using the interal atmega ADC?

Yes in this version

 

[Goboatingnow]

Circuits soon hopefully within two weeks.

 

[firebat45]

Circuits soon hopefully within two weeks.

Any updates on this? I am extremely interested.

 

[Ohms_Cousin]

update ?

 

[Ampster]

update ?

I would guess it died as a concept. 90% of what a BMS does is unrelated to whether the cells are on a boat, vehicle or land. I never saw a need for a BMS specifically designed for a boat.

 

[Skypower]

I would guess it died as a concept. 90% of what a BMS does is unrelated to whether the cells are on a boat, vehicle or land. I never saw a need for a BMS specifically designed for a boat.

I’m in the camp of less is more. More battery integration, the more things to go wrong. I’m a strong believer in a BMS having a strong active balancer, 2amp minimum for 280/305 class cells. Having that, I don’t believe that there’s much need for communication between batteries and system. I do however believe in a good dedicated alternator that communicates with inverter/charge control like Victron and a Arco/Zeus integration.

ARCO Zeus High Energy Bluetooth Alternator Regulator

High-energy External Bluetooth Alternator Regulator ARCO’s Zeus is the only high-energy external Bluetooth alternator regulator to feature Bluetooth (no additional equipment required) and a native app (on IOS and Android) allowing for easy installation and configuration. With its intuitive...

arcomarine.com

 

[Ohms_Cousin]

I would guess it died as a concept. 90% of what a BMS does is unrelated to whether the cells are on a boat, vehicle or land. I never saw a need for a BMS specifically designed for a boat.

Maybe he fell overboard and drowned? He was in Greece, so maybe a bit too much Ouzo ?