doubt regarding  BQ24650EVM-639

VSYS is the output (system voltage).

VOUT is the battery connection.

It might have been better if they'd called VOUT 'VBAT'.

As  rsc says, VSYS is the diode-OR of the panel and the battery and is supplied by whichever has the higher voltage.

In case you're tempted to try running a load directly from the battery (both supplied by the charger), I think you'll find you get to a stage where you can then overcharge the battery (as the current won't decline in the way the charger expects, the charger will keep going even though the battery has reached 100% capacity and is starting to work its way into the buffer region, and then you get to the point where the buffering runs out and you're just wrecking the chemistry and degrading the battery). You might get away with a light load that comes in a fair way below the end-point charge current, though.

VSYS is the output (system voltage).

VOUT is the battery connection.

It might have been better if they'd called VOUT 'VBAT'.

As  rsc says, VSYS is the diode-OR of the panel and the battery and is supplied by whichever has the higher voltage.

In case you're tempted to try running a load directly from the battery (both supplied by the charger), I think you'll find you get to a stage where you can then overcharge the battery (as the current won't decline in the way the charger expects, the charger will keep going even though the battery has reached 100% capacity and is starting to work its way into the buffer region, and then you get to the point where the buffering runs out and you're just wrecking the chemistry and degrading the battery). You might get away with a light load that comes in a fair way below the end-point charge current, though.

So if I understood you guys correctly the purpose of VOUT is specifically to charge the battery and VSYS for the load the latter being powered by the battery OR the panel So  BQ24650EVM-639BQ24650EVM-639 will be doing the switching between using panel or battery to supply power for the load(I guess using the panel as long as there's enough light to avoid using energy stored on the battery By the way thanks a lot for your quick response Both were great answers

The switchover occurs naturally, it doesn't need the charger chip to actively switch anything.

When the panel is above the battery voltage it supplies the load and charges the battery. When the panel gets down to just above the battery voltage the charger shuts down and then the handover is done passively by the diodes. (The charger is a buck converter and only operates when the panel voltage is above the battery.)

When you're designing your system, you'll need to look carefully at the panel characteristics and make sure it can support the load and the charging (or the battery may never charge or take an excessive time to do so). You'll also lose the adaption that the charger does to try and operate the panel at peak efficiency.

You've got the test setup, so you can look at those things and satisfy yourself that it does what you want it to do.

great!! Once again,  thanks a lot  Jon!

Hi

what is the maximum current the load can draw from the EVM board. I am using a 3s LiPo battery and my Load current varies between 1A to 40A.

Can this board support 40A?

It's all in the data sheet:

Symbol Description Min Typ Max Unit Notes

Supply voltage, VIN Input voltage 5 20 28 V

Battery voltage, VOUT Voltage applied at VOUT terminal 2.1 12.6 26 V

of J2

Supply current Maximum input current 0 8 A

Charge current, Ichrg Battery charge current 0 2 8 A For charge current above 2 A, replace R6

and L1 with high-current rating

components

Operating junction temperature range, TJ 0 125 °C

So max current as standard 2A, with some parts changes, 8A

MK

Hi, thanks!

I meant the load that is connected to Vsys, not the battery charge current. How much current can the board provide to Vsys ?

Is it possible if Vsys can draw current directly from battery in this case?

Study the schematic, it tells you the max current for Vsys.

Vsys is not regulated, it will be battery voltage or more.

MK

Ok.

My load requires 40A, so should I then connect it directly to my battery like in the image below?