[AuRavelling79]

I use a car battery (with a second charged and ready) to run my two reels which have separate flojet pumps. The batteries are charged overnight, not on the van.

When the battery is getting low on charge, one pump always seems to run slower than the other - it makes no difference if the pumps are drawing power together or each one on it's own.

When I swap to the second battery the power resumes to being the same flow for each pump.

Any idea why one pump "dies" before the other?

[Simon@ Clearview contractors]

Could be something to do with how many amps they draw and what a dying battery can supply...

[SunShineCleaning]

You obviously say unkind words to the weaker pump and it affects it's  performance.

"Apples of gold..." and all that.

[andyM]

You obviously say unkind words to the weaker pump and it affects it's  performance.

"Apples of gold..." and all that.

I find in most cases talking dirty to faulty equipment usually works.
If it doesn't take any notice I then give it a thump or kick.
When it still decides not to work I sling it in the bin. 

[Spruce]

Interesting question.

We had the same thing happen to us with 2 identical Shurflo pumps when the last leisure battery died. Both of these pumps draw the identical amps under load when working on the glass.

It can't be anything to do with wiring as both pumps are positioned together and both are supplied with the same length of wiring to the controllers and back. Both controllers are also the same.

We also noticed that after we switched off 1 pump when it was going very slowly, it failed to start again. You do know from experience that a pump draws more current to get it started that when it is running, so this could explain the failure to restart.

I don't know the answer. Could it be something to do with resistance in the circuits which in our case would include motor components, flow controllers, wiring and joins with strip connectors?

[Smudger]

We get the same with the pure freedom system pump 1 always flashes batt before pump 2 and the flow dies first

Other than fully charged or using the pumps with the van running when both read 14.1 pump 1 always reads 0.2 lower in amps than the other



Darran  

[Ian Sheppard]

Spruce I think is pretty much on the money.

While copper is a good conductor of electrical current is does also have some resistance as well. This is know as volt drop.
Eg you start of with one volt as the current passes along the cable it is not 100% efficient so by the time you reach the other end your one volt will be reduced how much is lost will vary as the quality of the cable and the connectors will also have an effect. Also long runs of cable will lose more voltage than short.

Electrical current will always follow the path of least resistance so if cable to one pump is longer than another the pump with the longer cable will lose power 1st.

As Spruce points out at start up a pump will draw higher current than when it is running. So Smudger your 0.2 is due to volt drop and in honesty there will always be some difference between the battery and pump. The majority of the time it is not significant enough to cause a problem. It will be more pronounced however if a battery is not holding a charge properly and as the battery becomes exhausted.

The pump tries to pull the same current however the battery is less able to carry the current as the volts diminish.

[AuRavelling79]

Thanks chaps - now I know!

[David Salkeld]

Spruce I think is pretty much on the money.

While copper is a good conductor of electrical current is does also have some resistance as well. This is know as volt drop.
Eg you start of with one volt as the current passes along the cable it is not 100% efficient so by the time you reach the other end your one volt will be reduced how much is lost will vary as the quality of the cable and the connectors will also have an effect. Also long runs of cable will lose more voltage than short.

Electrical current will always follow the path of least resistance so if cable to one pump is longer than another the pump with the longer cable will lose power 1st.

As Spruce points out at start up a pump will draw higher current than when it is running. So Smudger your 0.2 is due to volt drop and in honesty there will always be some difference between the battery and pump. The majority of the time it is not significant enough to cause a problem. It will be more pronounced however if a battery is not holding a charge properly and as the battery becomes exhausted.

The pump tries to pull the same current however the battery is less able to carry the current as the volts diminish.

Yeah, it's to do with resistance it the circuit. 
I take it you have two separate power wires to each pump circuit?
Also use thick grade wire - 30amp - less resistance.

David