# Increasing amperage in simple circuit

by Chark711
Tags: amperage, batteries, current, pump, volts
 P: 3 I am currently in an engineering project which is attempting to hook up some solar panels to run an irrigation pump. Right now, the pump that we have is a marine Bilge pump that says that at 12 Volts and 7 Amperes it can pump at around 3.3 Gallons Per Minute. We were provided with a standard zinc-lead car battery that produces 12 Volts. We hooked the pump and battery up, and measured its flow to be around 1.07 GPM, with the battery outputting around 1.84 A and 12.50 VDC. So we know that the pump can take more amperage, but is at its limit in volts. How do we reach this fabled 3.3 GPM? If I = V/R, then we either need less resistance or more voltage, but both seem impossible. Are there other batteries with less internal resistance that are more capable of producing the amperage we need (without such pathetic life-spans that they are useless)? Does anybody know if perhaps marine batteries are more capable at producing amperage than auto ones?
PF Gold
P: 6,353
 Quote by Chark711 I am currently in an engineering project which is attempting to hook up some solar panels to run an irrigation pump. Right now, the pump that we have is a marine Bilge pump that says that at 12 Volts and 7 Amperes it can pump at around 3.3 Gallons Per Minute. We were provided with a standard zinc-lead car battery that produces 12 Volts. We hooked the pump and battery up, and measured its flow to be around 1.07 GPM, with the battery outputting around 1.84 A and 12.50 VDC. So we know that the pump can take more amperage, but is at its limit in volts. How do we reach this fabled 3.3 GPM? If I = V/R, then we either need less resistance or more voltage, but both seem impossible. Are there other batteries with less internal resistance that are more capable of producing the amperage we need (without such pathetic life-spans that they are useless)? Does anybody know if perhaps marine batteries are more capable at producing amperage than auto ones?
You do NOT want more voltage as that will likely burn out the motor. What you need is a 12 source that will provide more amps than your battery is providing.
Thanks
P: 3,757
 Quote by Chark711 I am currently in an engineering project which is attempting to hook up some solar panels to run an irrigation pump. Right now, the pump that we have is a marine Bilge pump that says that at 12 Volts and 7 Amperes it can pump at around 3.3 Gallons Per Minute. We were provided with a standard zinc-lead car battery that produces 12 Volts. We hooked the pump and battery up, and measured its flow to be around 1.07 GPM, with the battery outputting around 1.84 A and 12.50 VDC.
Lead-zinc or lead-acid? Lead-zinc is not suitable for this sort of application; but a properly functioning and fully charged lead-acid car battery will have no trouble at all providing 7 amps (or several hundred amps - whatever power source you end up with, be sure you have a fuse or other overcurrent protection).

 P: 33 Increasing amperage in simple circuit Yeah, agreed, you want more AH in the battery. But, don't just assume you going to reach your stated GPM. Don't we have to calculate the head loss and gains?
P: 1,484
 Quote by Introyble Yeah, agreed, you want more AH in the battery. But, don't just assume you going to reach your stated GPM. Don't we have to calculate the head loss and gains?
That is most likely where his "problem" lies.

He is assuming that the pump will give 3.3 gallons per minute at any head. A bilge pump would be rated for low head, and it is not mentioned at all in the question, ie the head at 3.3 gpm.

I suspect, but only guesing from limited information, he is operating on the lower part of the pump characteristic curve with higher head and lower flow rate, where the power needed would naturally be less than the 12 v and 7 amp.

Other reasons would be that the pump is worn, there is an obstruction at the inlet, or there is not enough positive suction head.
 P: 114 This does not add up. Pump is rated at 7A at 12v to deliver 3.3 gallons per minute. It is at 12v and a bit and is drawing only 1.84A for 1.07 gallons so is clearly lightly loaded and nowhere near capacity. So the reason for the reduced flow is not a blockage or impediment or high working head or current would be higher. Not low volts because we are at rated voltage. So why is the pump so lightly loaded? Is there an air leak into the inlet? Is the impeller loose on the shaft? A poor seal or a misalignment?
Mentor
P: 22,302
 Quote by phinds What you need is a 12 source that will provide more amps than your battery is providing.
No, I agree with 256bits: what I think is the problem here is misleading pump specs. Often, pump vendors will provide the maximum flow of the pump, which occurs if it isn't generating any head (pressure). If you attach piping and pump it uphill, the flow goes down and the energy input with it. There probably isn't anything that can be done here except to get a bigger pump.

Chark, do you have a pump performance curve? How much lift (head) do you have in your system? What is the pressure rating of the pump?
Mentor
P: 22,302
 Quote by pumila This does not add up. Pump is rated at 7A at 12v to deliver 3.3 gallons per minute. It is at 12v and a bit and is drawing only 1.84A for 1.07 gallons so is clearly lightly loaded and nowhere near capacity. So the reason for the reduced flow is not a blockage or impediment or high working head or current would be higher. Not low volts because we are at rated voltage. So why is the pump so lightly loaded? Is there an air leak into the inlet? Is the impeller loose on the shaft? A poor seal or a misalignment?
No. It may be counter-intuitive, but more resistance results in less power draw. The reason comes from the pump law: power draw is a linear function of pressure, but a square function of flow.