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I have a device that uses li-ion battery and the device is also connected to battery directly. For charging I have used TP4056 IC. Flow is like this, V_charge(5v) -> TP4056 -> Battery & load (No load sharing switching while charging). Now this is not recommaneded but I have to go with this for now.

Charging supply will not be there always. Charging current for TP4056 : 500mA; Load current : 200mA(max).

Considering my load current will not go above programmed current of TP4056, if I countinue with this flow will there be any problem over shorter and longer period(1 year or maybe 2) ?

My main doubt is what will heppen if battery is in deep discharge and than I apply charging voltage ? If voltage is below 2.9v, IC will go in trickle charge mode than current supplied to battery will be minimal. In this case my load current is still 200mA (higher than supplied). Will battery ever come out of trickle charge ? Could it damage some other components ?

My issue is shorting of Vin and Vbat pins of ICTP4056 in some devices. I am not sure whether the issue is because of above mentioned problem or not. if anyone knows what could cause this behevior in IC and how can I replicate the problem, please share.

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Yes there will be problems.

If the charger IC has to provide current to battery and load, the charger IC cannot determine when battery current has dropped to low enough level to stop the charging.

Therefore each time you charge the battery, it will be overcharged as it is charged longer than when it is full.

When battery drains below trickle charge level, the trickle charge cannot charge the battery at all if there is a load present.

When battery is drained to the level it is considered empty, if your load keeps draining the battery, then the battery will start degrading or getting damaged when voltage drops below safe level. Therefore there should be a battery protection chip to cut it off if drained too much, but it likely will cut the battery off forever, as the charging IC can't tricle charge the battery.

So don't apply load to battery while it is charging or below safe voltage level.

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  • \$\begingroup\$ Sorry I was away, I will add load switching circuit to address overcharging issue. One thing is still not clear for me , if my cell has BMS attached to it which cutt off battery below certain voltage(2.7 I think) then will battery be in trickle charge mode from there ? and lets say BMS has disconnected the battery then still battery will discharge over long time ( few months) ? \$\endgroup\$
    – dharmikP
    Apr 20 at 15:03

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