Hi there

I'm using a 3.7v LiPo battery to power a variable boost converter outputting 24v. When I connect the battery the voltage on the input and across the battery terminals drops to 1.9. When I switch it off, the voltage goes back up to 4.1v. I'm using a 1100mAh battery, the output side on the boost converter is drawing approx 500mA and is used to saturate a couple of 35v caps to drive a coil.

I suspect a protection circuit on the battery is kicking in if it thinks too much current is being drawn. My question is - is there a simple fix?

Any help or advice is greatly appreciated.

 

You are asking the battery to supply more than 24/3.7 x 500 = 3243 mA

A Lipo battery that is not a high-discharge type can only supply about 1C = 1100mA.

The result is not surprising.

 

If you are just charging capacitors, the add a resistor in series with the converter output to limit its output current to about 150mA.

 

You are asking the battery to supply more than 24/3.7 x 500 = 3243 mA

A Lipo battery that is not a high-discharge type can only supply about 1C = 1100mA.

The result is not surprising.

Thanks for your reply. This is the boost module I'm using: https://www.amazon.co.uk/dp/B091YQRZPL?ref=ppx_yo2ov_dt_b_fed_asin_title

The max current the boost converter can supply on the output side is 2A, however, that's at a much lower voltage. At 24v it's drawing much less so I would have thought the battery could cope. Bigger battery or AAAs I guess.

 

If you are just charging capacitors, the add a resistor in series with the converter output to limit its output current to about 150mA.

Thanks for your reply. I'll give that a try.

 

The max current the boost converter can supply on the output side is 2A

The current rating of a power supply only tells you what it can produce continuously without being damaged. Generally, they can provide higher currents for a short time, but won’t last long if you do that.

 

The current rating of a power supply only tells you what it can produce continuously without being damaged. Generally, they can provide higher currents for a short time, but won’t last long if you do that.

Understood. Thanks

 

If the capacitor charging speed is important, you could use a simple two-transistor constant-current circuit instead of a resistor to limit the charging current, but reduce the charging time by a factor of about 3 to the 90% capacitor voltage value.

 

If the capacitor charging speed is important, you could use a simple two-transistor constant-current circuit instead of a resistor to limit the charging current, but reduce the charging time by a factor of about 3 to the 90% capacitor voltage value.

Thanks for the additional info. Just added a 120-ohm resistor in series to the output. Worked a treat!