Looking for turn-key BMS system

I have a list of future projects which includes a battery monitor. I figure it might have a wire per cell (+1 at the end of the string) and snoop voltage, ripple, and estimate cell impedance, something like that. Measuring string current would help.

John

Measuring the core battery temperature is a good idea. Measuring surface temperature of the battery is useful additional information.

Battery output voltage depends on temperature and the state of charge (not to mention the current flowing through the internal resistance).

It you have enough current flowing through the battery to create thermal gradients, life can get complicated and you'd need to do a bit of thermal modelling on the fly.

I got asked that question at a job interview - I didn't get the job. Maybe the interviewer thought that I was over-complicating the task.

Looks good, they have a lithium battery with internal BMS at resonable price.

No State of Charge (SoC) though for the battery. Is it possible to get rough SoC from a lithium battery by voltage sensing only?

A number of hits online says that SoC is difficult to determine for a Lithium battery purely from the voltage.

But for the cell I am using, the datasheet seems to disagree (if compensated for temperature)

Victron has been suggested, who are a good start for turnkey options.

In the DIY home storage and EV (electric bike, car) community there are a bunch of 'smart' Chinese BMSes in use: (in roughly descending order of usefulness)

JK BMS (Jikong) JBD BMS (Jiabaida) Daly BMS

which operate via Bluetooth, having their own phone apps but also a protocol via RS485. They come in versions from about 20A to 300A (although I wouldn't run one near its maximum rating).

Then there are vendors who make rack-mount LiFePO4 batteries with BMSes designed to talk to solar inverters:

Pylontech Seplos

Usually those rack batteries are in 2+kWh configurations so perhaps less useful to you, but maybe the BMSes are.

Probably not the kind of supplier or level of integration you want to deal with, but it's useful to be aware of the communities using them. More info on various forums, eg:

Slightly more integrated-ly, there are LiFePO4 'leisure' batteries that have the BMS included. Some of those offer a display or bluetooth app that might give you enough information.

Theo