BQ27750EVM-837: integrate into application for monitoring

Anja,

If you want to use the bq27750 to monitor the State of Charge it is required to undergo the chemID selection, Data Memory configuration, and Learning cycle. Are you able to find your battery in the ChemID plug-in through bqStudio?

Your connections sound right. The battery- should be connected to 1N and the battery+ should be at 1P. The bq27750 has built in protection features to protect the IC against things like cell over-voltage, Over Current, and ect... it does this by controlling the FETS connected on the high side trace. The FET byPass jumper (when shorted) allows Pack+ and Bat+ to be directly connected. I would not recommend to have this shorted, but rather configure the data memory to not have the FETs turn off when not desired.

If you are connecting a charge/load to the pack pins and seeing a discharge current it would be safe to assume that you have a load connected and the battery truly is discharging. This EVM does not have an on board charger thus you should only apply a power supply set to the battery max voltage on the charge pins.

Maybe i am not understanding the full question. please elaborate if my information did not assist.

Thanks,
Eric Vos

Hi Eric

What I acutally want to do is the following:
We have a energy harvesting device that delievers not constant but dc current and should charge the battery connected to the energy harvesting board. On the same board we have also a chip which consumes current. What I want to do know is to monitor the charging/ discharging current/voltage as well as the relative state of charge. I hope it is clearer now.

I couldn't find the battery ( and my database should be up to date). The battery is the GMB-300910 from GMBPower. Is there another way to add the chemId?

I couldn't find a manual for the software therefore I don't know what I need to configure in the data memory and I am also not sure if I understand the concept of a learning cycle. It somehow includes discharging until the battery is empty and recharging but I don't see why I need this to be able to monitor the current and the voltage of my battery. for what is it good for and what do I need to configure in the data memory?
Thanks a lot!

Kind regards
Anja

Anja,

Connecting the device to just monitor voltage and current is easy. When you say you want to monitor relative state of charge this is where the learning and configuration is needed. Relative State of charge is a complicated thing. It is very dependent on discharge rate, temperature, age, and more.

If you are wanting something very basic to act as a passed charge accumulator you might want to look into the bq35100 in accumulation mode. What this device will do is while it is active it will adjust a charge counter based on the current it sees. It does not report out state of charge though and you would need to calculate this yourself on your host system. it will report out voltage, current, and temperature as well.

In your application do you expect to see substantial discharges or do you expect the battery to be full most of the time?

Thanks,
Eric Vos

Hi Eric
I see we therefore will have to do an learning cycle as we want to monitor the relative state of charge. Is there a manual for doing the leraning cycle, the memory configuration as well as integrating the battery if it is not in the data base?
In our application we probably will see substantial discharge over a longer time until the battery is almost empty (if the energy harvested power is not enough for the computing power of the chip). Idealy the energy harvested power was enough for the chip and the battery wouldn't discharge.
Thanks a lot!