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Old 09-18-2021, 09:51 AM   #1
BRB Rig
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Water Pump Capacitor vs Dedicated Line

Has anyone hooked up a capacitor to a 12v Shurflo water pump to alleviate the flickering/dimming trailer lights issue? Would this be a better solution than running a dedicated line to our LiFePO4 battery system? We’ve been told that the reason the lights flicker is because the pump draws from the same line. Any advice appreciated. Moda & Cherry
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Old 09-18-2021, 10:22 AM   #2
quaddriver
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Originally Posted by BRB Rig View Post
Has anyone hooked up a capacitor to a 12v Shurflo water pump to alleviate the flickering/dimming trailer lights issue? Would this be a better solution than running a dedicated line to our LiFePO4 battery system? We’ve been told that the reason the lights flicker is because the pump draws from the same line. Any advice appreciated. Moda & Cherry

if you did wanna do this, it would be to the coach itself..., before the water pump switch. if after the switch, the cap would charge when the pump comes on (and it would be big, say 25v, 4000uF or more) and it would let the motor run a rev or two after the switch cut off, discharging.



So if it was before the switch, it would act like the cap you already have...the battery.


The real problem is the junk lights they use. since all our lights are in the 2700-3500K range, white (unless weirdos use red or purple...), they have a Vf of about 3.2v, therefore in the 12v system, somewhere in the light is a 12v-5v zener or Vr. You could as a test open on up and solder about 47uf 16v cap across the led leads. But this might not work as a lot of the lights I source now are AC and DC and wide voltage hence, dual polarity and sealed from tampering...



If I was making light fixtures, I would use a 78M05 sMD equivalent for a Vr and a .01 ceramic on input and output to decouple spikes, then mebbe just a 10uf 16v cap to smooth serious load drops (like the slide coming in and hitting the stops) but not enough to keep the lights on much after lights out...just a soft fade, but then, my fixtures would cost at least twice as much...
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Old 09-18-2021, 02:47 PM   #3
flybouy
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Originally Posted by BRB Rig View Post
Has anyone hooked up a capacitor to a 12v Shurflo water pump to alleviate the flickering/dimming trailer lights issue? Would this be a better solution than running a dedicated line to our LiFePO4 battery system? We’ve been told that the reason the lights flicker is because the pump draws from the same line. Any advice appreciated. Moda & Cherry
Has it always done this or is this something "new"? If it just started then has anything changed, any wireing or other electrical chamges made? I would start off with checking the amperage draw from the pump. If it's excessive then there's an issue, pump could be failing, a corroded connection could be creating high resistance, etc. Adding a capacitor may just mask a problem that will still go unresolved.

You didn't share your camper model and year so as just a general thought, if the pump was changed at spme point and now draws higher amperage that the wire is not sized appropriately for and is reasonably close to the battery or the power center I would disconnect the positive wire at the pump and feed a relay with it. Then use an appropriatly sized fuse and wire to supply the pump via the relay.
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Old 09-18-2021, 03:15 PM   #4
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Has it always done this or is this something "new"? If it just started then has anything changed, any wireing or other electrical chamges made? I would start off with checking the amperage draw from the pump. If it's excessive then there's an issue, pump could be failing, a corroded connection could be creating high resistance, etc. Adding a capacitor may just mask a problem that will still go unresolved.

You didn't share your camper model and year so as just a general thought, if the pump was changed at spme point and now draws higher amperage that the wire is not sized appropriately for and is reasonably close to the battery or the power center I would disconnect the positive wire at the pump and feed a relay with it. Then use an appropriatly sized fuse and wire to supply the pump via the relay.
Yes. The two pumps we’ve owned have always triggered lights dimming and flickering since we got the toy hauler in 2018. The amperage draw is the same for both. We’ve been in friends’ rigs and noticed the same issue. Like QD stated, the lighting quality isn’t great. We’ve read a lot of the same online. We’ve got a 2015 Fuzion toy hauler powered by a ton of lithium. We use a second Shurflo pump for filling our freshwater tank from our 30 gallon remote tank. You could be right about the capacitor masking something else. Thanks QD for mentioning where to install the capacitor (before not after the switch). I think what we’re going to do is run a designated line from our busbar. We do the same for the second pump, no dimming or flickering there. I just don’t know if the power for the primary pump runs parallel with the lights or separate to the breaker. Also, is the power connect for the pump at or near the console switch? I didn’t see it at the pump. Would a 10 or 15 amp fuse work for power to the pump? Or do we need to mount a circuit breaker near the busbar power source? Moda & Cherry
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Old 09-18-2021, 03:17 PM   #5
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Just saw the part about using a relay. However, how could we still use the console switch to turn the pump on and off?
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Old 09-18-2021, 03:21 PM   #6
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Originally Posted by quaddriver View Post
If I was making light fixtures, I would use a 78M05 sMD equivalent for a Vr and a .01 ceramic on input and output to decouple spikes, then mebbe just a 10uf 16v cap to smooth serious load drops (like the slide coming in and hitting the stops) but not enough to keep the lights on much after lights out...just a soft fade, but then, my fixtures would cost at least twice as much...
We would imagine you’d sell a lot of those lighting units!
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Old 09-18-2021, 03:39 PM   #7
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Just saw the part about using a relay. However, how could we still use the console switch to turn the pump on and off?
If the console switch powers the pump now then disconnect that wire at the pump. Use that wire to energize the coil on the relay. The other terminal of the relay coil is grounded. The contacts of the coil (normally open) get connected one to the pump positive side and the other to a fused 12 vdc source.
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Old 09-18-2021, 09:46 PM   #8
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If the console switch powers the pump now then disconnect that wire at the pump. Use that wire to energize the coil on the relay. The other terminal of the relay coil is grounded. The contacts of the coil (normally open) get connected one to the pump positive side and the other to a fused 12 vdc source.
Thank you! We think we got it now. When the console control switch for the pump is on, it now energizes the wire that runs from the switch to the pump which turns the pump on. When we add a relay, the same wire would run into the positive side of the coil and a ground would connect to the negative side of the coil. When energized, the current from the switch would connect the circuit, allowing electricity to flow from the positive battery wire (hooked up to the relay common terminal) and the positive pump wire (hooked up to the relay's connect terminal). When the switch is off, the relay would be open, cutting the electrical connection between the com and the connect terminal. Do we have this correct? Also, can you recommend a relay that would work for us?
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Old 09-19-2021, 06:38 AM   #9
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Thank you! We think we got it now. When the console control switch for the pump is on, it now energizes the wire that runs from the switch to the pump which turns the pump on. When we add a relay, the same wire would run into the positive side of the coil and a ground would connect to the negative side of the coil. When energized, the current from the switch would connect the circuit, allowing electricity to flow from the positive battery wire (hooked up to the relay common terminal) and the positive pump wire (hooked up to the relay's connect terminal). When the switch is off, the relay would be open, cutting the electrical connection between the com and the connect terminal. Do we have this correct? Also, can you recommend a relay that would work for us?
That's correct. Any NO relay (I'd use a 30 amp one to be safe), from an out parts store or on-line like this https://www.amazon.com/Bosch-0332019...2062054&sr=8-3
Make sure you use an in-line fuse at the power source (i.e. at the battery or power center) that's matched for the max amperage draw of the pump.
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Old 09-19-2021, 08:36 AM   #10
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That's correct. Any NO relay (I'd use a 30 amp one to be safe), from an out parts store or on-line like this https://www.amazon.com/Bosch-0332019...2062054&sr=8-3
Make sure you use an in-line fuse at the power source (i.e. at the battery or power center) that's matched for the max amperage draw of the pump.
Thanks again! We ended up ordering overkill! An 80amp relay that we can screw down wires. Since the pump has a max 8 amp draw, we also ordered a 10 amp in-line fuse to connect between the battery positive busbar and wire to the relay. We really appreciate your help! https://www.amazon.com/dp/B010L02RUO/ Moda & Cherry
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Old 09-19-2021, 08:45 AM   #11
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Thanks again! We ended up ordering overkill! An 80amp relay that we can screw down wires. Since the pump has a max 8 amp draw, we also ordered a 10 amp in-line fuse to connect between the battery positive busbar and wire to the relay. We really appreciate your help! https://www.amazon.com/dp/B010L02RUO/ Moda & Cherry
Over capacity is not an issue. Just be sure to connect to the NO (normally open) connections.
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Old 09-24-2021, 05:38 PM   #12
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Over capacity is not an issue. Just be sure to connect to the NO (normally open) connections.
Just an update. We’re getting ready to hook up the relay. We recorded a short video of what we believe is the correct method for hooking it up. If anyone can watch our video and confirm if we’re correct, we’d appreciate it. Moda & Cherry

The video is at https://bit.ly/3EIK4uy
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Old 09-24-2021, 05:52 PM   #13
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One thing I’d say about these mods…I’d write down locations,wiring diagrams,reasons for installing mods and model numbers or the label off the relay and stick it all in your Owners manual folder .
In case you ever sell the rv the next owner will have an idea of what is going on and why you installed it and where it’s located.
People come on the forum all the time with weird electrical issues and wonder if it was an owner or factory installed fuse, wire etc
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Old 09-24-2021, 08:42 PM   #14
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One thing I’d say about these mods…I’d write down locations,wiring diagrams,reasons for installing mods and model numbers or the label off the relay and stick it all in your Owners manual folder .
In case you ever sell the rv the next owner will have an idea of what is going on and why you installed it and where it’s located.
People come on the forum all the time with weird electrical issues and wonder if it was an owner or factory installed fuse, wire etc
Great advice. In our case, we’ve documented everything we’ve done in detailed videos. What did you think of the video? Our new relay came with zero instructions and we’re seeking advice. Did we make any mistakes? Any help appreciated. Moda & Cherry
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Old 09-26-2021, 12:06 PM   #15
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Thanks for all the advice! We successfully hooked up the relay. It's SO GOOD to run water without flickering lights. For anyone interested in performing this mod, I created a diagram of the steps we took. We installed the relay near the pump. While the relay comes with a plastic cover, we sheltered it from potential water as best we could. We paid $17 for the relay. It's overkill at 80a, but works great. https://www.amazon.com/gp/product/B010L02RUO/

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Old 09-30-2021, 07:57 AM   #16
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Could you draw it out using an auto store 40 A relay?

I’m weak on relay and electrical hookups.

I too have the led light flicker when pump runs.
Thanks
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Old 09-30-2021, 08:32 AM   #17
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Could you draw it out using an auto store 40 A relay?

I’m weak on relay and electrical hookups.

I too have the led light flicker when pump runs.
Thanks
Yes. Just like flybuoy wrote. Just make sure you identify the coil, common, and NO (normally open) contacts on the relay so that you know which wires go where. You can use the diagram we created as an example of how it all works. We went for the larger relay because of the screw terminals and the fact that we could see everything work. It’s only been a week, but it’s been solid for us so far. 😀 Moda & Cherry
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