# Insufficient force from 6 V 1 A push-pull solenoid powered by a stepped down 9 V battery (relay) — why and what can be done?

I am powering a 6 V 1A push-pull solenoid using a 9 V 1Ah rechargable lithium ion battery (form: 9 V alkaline) using a relay; the 9 V is stepped down to 6 V; controlled by Arduino. It is to be used as a kicker for a robot. The force is weak, perhaps less than the 5N advertised, why? Is it because the current draw is low (i.e. far less than the rated 1A)?

What can be done?

1. Should I use 9 V without stepping down?
2. Use a capacitor to store charge, and then discharge, so the current supply will be ~1A?
3. Can >1A of current be supplied to the solenoid for a short duration?
4. Should I get another solenoid, maybe a 12 V 1A?
5. If I should use a different power supply, what can I get that is small? I have a bunch of 3.7 6.8Ah li-on batteries around.
• What's the current delivery capacity if the battery? How is it being stepped down? – Passerby Mar 20 at 4:14
• Unknown current delivery capacity because it is a chinese made li-on battery. Step down is using a buck converter, this one: amazon.com/4-75-23V-1-17V-DC-DC-Converter-Module/dp/…. The mod can deliver uo to 3A, reckon the batt is the bottle neck? What can be done? – Jorge Mercent Mar 20 at 4:55
• Ah, yes, small weak solenoid usually take less than 1A, while big solenoids might take over 4A. You might like to see the force vs current from these two posts: (1) Rpi.org.forum solnoid (0.8N to 20N) discussions raspberrypi.org/forums/… (2) Searched query: solenoid tlfong01 found 149 matches raspberrypi.org/forums/…. Cheers. – tlfong01 Mar 20 at 6:32
• Typically, you're dealing with a 3.7v cell, stepped up to the 9v output voltage. You're not getting much current out of that. A cheapie I'm looking at has a max output current of under 1 amp, while the solenoid you've shown has a max draw of about 1.6 amps, from a 6v supply. Stepping 3.7v up to 9v in order to step it down to 6v? Hmmmmmmm! – enhzflep Mar 20 at 8:41
• You would do better if you had a single question. Welcome to the site. – Brian Carlton Mar 20 at 18:20

If you mean pick-up power by saying kicker, I faced this problem once. My robot cart couldn't pick up when stoped. I solved the problem by placing a 220uF capacitor parallel to the current control resistor. At start, the capacitor and the resistor both conduct. But at run time only the resistor conducts. I refered to the link showing the kicker. Do you use it for some thing to throw or to get a pick-up? I used the capacitor for the motor.But you can use it for the kicker. Capacitor pases an instant current additionaly.

• thx upali, i am using it for throwing/kicking. I think i have solved the problem. Thx for your help anyways. – Jorge Mercent Mar 24 at 14:30

Solution:

1. 50v, 10000uF capacitor
2. Change 9v to 12v li-on instead & step up (instead of step down) to ~30v
3. Control by Arduino, relay NC port connect capacitor to supply supply, NO port to solenoid, on signal NO closes
4. 6v solenoid will do the job, but will heat up a bit, 12v solenoid will be better.
5. Try 100v capacitor, stepping up to 68v for even more fun, but just be careful, ouchie. Conservely, can use 3 35v 3300uF in series, step up to 18v, modest kick, depends on ball weight.

For reference to those who need it.