Spv1050 battery charging issue

[jayasreejayaraj]

    I have made a custom pcb of STEVAL-ISV019V1  circuit. In that ,we need to charge 3.7v lithium ion battery via USB supply and solar panel. When I connect USB supply or panel voltage as input voltage  the complete input voltage is coming in the battery charging point. where as the lithium battery can only  be charged  up to 4.2V.when I measure the open voltage at battery charging point it appears greater than 4.2V.How can we set the charging voltage  and also how can I measure the open voltage at fully charged condition?

[Peter BENSCH]

Welcome @jayasreejayaraj, to the community!

Have you worked through both the data sheet and the AN4394 (both available under Documentation)?
Both deal with EOC and VEOC, respectively, which can be used to adjust the end-of-charge voltage.

Hope that helps?

Regards
/Peter

[jayasreejayaraj]

when we connect battery alone, the LDO1 and LDO2 outputs are not getting. but incase of solar panel and USB power supply  store pin is shorted and the LDO outputs are working .Our device is working on battery supply we use USB only for battery charging. So that we need to get LDO outputs from battery supply. Let me know why it is getting disabled in battery condition.

[Peter BENSCH · Accepted solution]

But that is exactly the point of how the SPV1050 works and what you find in its data sheet. The SPV1050 is originally intended as a pure harvester that processes the energy coming from the input for the battery. Everything else has to be done from the battery rail.

It must be taken into account that LDOs are anything but energy-saving, because they not only have their own current consumption, but also burn up the differential voltage between the battery and the respective output. Since this can drastically shorten battery life, the LDOs are only active when an input voltage (solar, USB) is present.

Regards
/Peter

[jayasreejayaraj]

I have checked the resistor values of EOC and VEOC as mentioned in the datasheet. but still When I connect USB supply or panel voltage as input voltage  the complete input voltage is coming in the battery charging point. where as the lithium battery can only  be charged  up to 4.2V.when I measure the open voltage at battery charging point it appears greater than 4.2V.

[Peter BENSCH]

Please remember that the STEVAL-ISV019V1 works in boost mode and can therefore only be used for lower input voltages than the battery voltage, which is simply due to the way a boost converter works. For larger voltages, such as 5V from a USB port or a solar cell with more than 3.7V, a parasitic pn junction in the SPV1050 becomes active, so that the full voltage also appears at STORE and thus also at BATT. You can see this in the data sheet of the SPV1050, where it can be found under Absolute Maximum Ratings:

• IN_LV (Analog input): VSTORE+0.3V

...where VSTORE is also present at BATT due to the then closed switch.

If you work with input voltages that can be lower and higher than the battery voltage, you have to let the SPV1050 work in buck-boost configuration, which can be done e.g. with the STEVAL-ISV020V1. Don't worry, you don't have to order this kit again: the STEVAL-ISV019V1 can be converted to STEVAL-ISV020V1 by making the changes to pin 19, pin 20 and their connection to CN1 and L1 (refer to their schematics).

Good luck!
/Peter

[jayasreejayaraj]

In buck-boost configuration SPV1050 have only 30mA output current. Is there any other MPPT  IC available which is having large output current and input voltage of 3.4V to 12V?