looking to go solar on our new boat dock, not feasible to run AC. I need to power a boat lift motor that is 230v and draws 7.7amps at 60hz single phase. Looking for recommendations on solar panel wattage, battery setup (assuming 24vdc preferred?), inverter, and if any sort of startup capacitor is needed, especially when lifting out of water. Any recommendations?
Solar Powered Boat Lift
- Thread starter pogo2
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one more question to add - also hoping to power some dock lights on same system, i assume this would be an easy add-on, there are enough DC LED lights out there that would work i think.
svetz
Works in theory! Practice? That's something else
Welcome to the Forums!
How long does it need to run for and how many times per day? Thinking a battery for while it runs and solar to charge it through out the day.
If you only use it on Saturday it could be pretty small taking the whole week to recharge. Anyway, post your usage thoughts and hopefully you'll get some ideas. Same thing for the lights... how many watts are they and what sort of usage (if on a motion sensor how many events per night and what duration).
How long does it need to run for and how many times per day? Thinking a battery for while it runs and solar to charge it through out the day.
If you only use it on Saturday it could be pretty small taking the whole week to recharge. Anyway, post your usage thoughts and hopefully you'll get some ideas. Same thing for the lights... how many watts are they and what sort of usage (if on a motion sensor how many events per night and what duration).
thanks for the reply. The lift will runs for ~5-10 minutes at a time, estimated. lifting a boat up and dropping it down. more load lifting than dropping, obviously. Would use the lift 1-2 times a day max, pretty much only on the weekends. The lights would only be switch activated, so no motion sense, and a maybe total up to 30 watts, not looking for a lot of light, just enough to light up the dock and boat at night. I can see them being on for a few hours at a time during the night at most, again, mostly just during the weekend. thanks in advance!
I have a boathouse lift for a 8000-9000 pound boat. Twin 120Vac 3/4 HP motors that would regularly choke out a 2800w propane inverter generator I tried to run it with.
Now I run it on a 25 Ah 48v LiFePO4 battery. I have used a 3kw WZRELB cheap chinese inverter which struggles and a much more robust Sigineer 3kw inverter that can do 9kw surge. The Sigineer has no problems and can do 240Vac.
I use it a couple times each weekend and hook up solar panels to charge it every couple weeks.
Now I run it on a 25 Ah 48v LiFePO4 battery. I have used a 3kw WZRELB cheap chinese inverter which struggles and a much more robust Sigineer 3kw inverter that can do 9kw surge. The Sigineer has no problems and can do 240Vac.
I use it a couple times each weekend and hook up solar panels to charge it every couple weeks.
svetz
Works in theory! Practice? That's something else
A counterweight could negate the weight of the boat, possibly using water as the weight? Let a little water out to drop the boat, pump a little water in to raise the boat?
7.7 amps x 240 (assuming USA) = 1848 watts while running. In-rush current might be as high as 80 amps (e.g., 20,000 watt surge on inverter). Look for the LRA on the motor if you already have it.
Since you need 1848 W for 40 minutes, it's 1848 x 40 min (1 h/ 60 min) =1232 wh/d, 2 days for the weekend, so 2464 Wh.
Battery is 24 volts and needs to supply 2464 Wh / 24V = 102 Ah. Lead Acid use a 50% DoD, so 204 Ah. If LiFePO4, 80%, so 128 Ah.
You need a battery big enough to handle the discharge rate (typically 1C), which is 1848 W/24V = 77 amps @ 24V. The battery is over that, so no worries there.
If lead acid, the peukert effect would for high draw would be substantial, so add 20 to 30% or as indicated by the battery's datasheet.
Assuming an 80% round trip efficiency, the solar panels would need to regenerate 2464 / .8 = 3080 Wh over the course of 5 days = 3080 / 5 = 616 W/d. Assuming an insolation of 4, then 616/ 4 = 154 W array.
The additional solar would be 225 watt hours spread over 5 days or 225 / 5 = 45 Wh, at insolation of 4 that's 12 Watts. 12 + 154 = 166 watt array.
Hope that helps!
Update: Don't trust my math ... already corrected two errors! ?
You'll need the inrush current to get an idea of the startup surge current the inverter must supply. If you can find a DC motor you'd be better off.
7.7 amps x 240 (assuming USA) = 1848 watts while running. In-rush current might be as high as 80 amps (e.g., 20,000 watt surge on inverter). Look for the LRA on the motor if you already have it.
2 times a day, thats 4 events (2 up and 2 down) of 10 minutes or 40 minutes total per day.
Since you need 1848 W for 40 minutes, it's 1848 x 40 min (1 h/ 60 min) =1232 wh/d, 2 days for the weekend, so 2464 Wh.
Battery is 24 volts and needs to supply 2464 Wh / 24V = 102 Ah. Lead Acid use a 50% DoD, so 204 Ah. If LiFePO4, 80%, so 128 Ah.
You need a battery big enough to handle the discharge rate (typically 1C), which is 1848 W/24V = 77 amps @ 24V. The battery is over that, so no worries there.
If lead acid, the peukert effect would for high draw would be substantial, so add 20 to 30% or as indicated by the battery's datasheet.
Assuming an 80% round trip efficiency, the solar panels would need to regenerate 2464 / .8 = 3080 Wh over the course of 5 days = 3080 / 5 = 616 W/d. Assuming an insolation of 4, then 616/ 4 = 154 W array.
30 watts x 3 hours (a few?) = 90 watts hours/day, 180 watt hours/weekend, an additional 7.5 Ah @ 24V (15 Ah if Lead Acid). At 80% Round trip efficiency, 225 watt hours of solar needed to replenish.
The additional solar would be 225 watt hours spread over 5 days or 225 / 5 = 45 Wh, at insolation of 4 that's 12 Watts. 12 + 154 = 166 watt array.
Hope that helps!
Update: Don't trust my math ... already corrected two errors! ?
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I should add that the inverter is turned off whenever the lift is not in use to save battery power.
I have never used a startup capacitor for either inverter.
If I needed lights I might add a small 12v LiFePO4 battery and panel to keep it simple. Amazon has 8Ah LFP for around $30.
I have never used a startup capacitor for either inverter.
If I needed lights I might add a small 12v LiFePO4 battery and panel to keep it simple. Amazon has 8Ah LFP for around $30.
great info - thanks for the recommendations. It looks like I have been looking at a system that might be oversized for this application! Here's what i'm looking at: 4 120W solar panels, 2 200A AGM batteries (are LiFePO4 batteries better for this application? I know they are much more expensive but last ~3-4x longer), a 40amp controller, and a 5000W (10K surge) 12vDC-240VAC inverter.
just updating my findings for posterity... to find my "LRC" (locked rotor current), doing some more research motor faceplate says this is a NEMA type K. Per NEC Table 430.7(B) that means it's KVA/HP = 8-8.9 (i just used 9 for my calculation). It's a 1.5 HP motor at 230v rated for 7.6 amps. From that I calculated LRC using this formula: Amps = kVA per hp 1,000 hp ÷ (V 1.732) - which gives my result of 34 amps. 34 amps at 230v comes out to about 7800 watts of demand at startup, so my 5k/10k 12-240 inverter should do the job. now i need a nap. Anyone smarter than me feel free to check my work.
Hi forum! Coming back to update and pose a few questions.
I think my system is set up to handle all the electrical load... except I now have some uncertainty regarding the lift motor surge amps exceeding the nominal capacity. Let me give an overview of my current setup and calcs. Solar: renogy 400w system with 40A mppt controller. Going to run series parallel (2S2P). I'm in Texas, and the bulk of usage will be in the summer - no concerns about insolation and charging capability of my bank, because of low usage on the motor (.5 to .75hrs use daily). I am feeding that to 2 ampere time 200AH LiFePO4 batteries with 100a BMS (280a max) in parallel to get a total of 400AH with 200Amps current / 560amps max. My inverter is a sigineer 12v 120/240 3000W (9000W surge). I am protecting that with a 250a ANL fuse from battery to inverter. Finally, the motor I am trying to power is a 1.5hp dual voltage 120/240 that runs 1725RPMs at 15.4/7.7amps. Motor has a service factor of 1.15, meaning a top end current of 17.6/8.8. It's a code "E", 60hz.
So this is where things get tricky. The motor's "Locked Rotor Amps" based on it being code E is 62.4a at 120vAC, which translates to a spike of 7488 Watts. Inverter can handle, no problems there. My concern and question comes with the DC amps. If my calculations are correct, the specs above will induce a 689amp DC current for that instant of startup, which exceeds max rating of my battery bank BMS (560amps max) as well as my ANL fuse. I guess my question is: can the system setup I have handle this for the few hundredths of a second that is needed to overcome the inrush surge? Or do i need to size up my batteries to 24V, which would reduce current needed by half? In that scenario, I'd obviously also need to get a different inverter to do 24V.
So... what do we think? Are my DC volts too low to handle the inrush current, even at 1/120 second demand?
I think my system is set up to handle all the electrical load... except I now have some uncertainty regarding the lift motor surge amps exceeding the nominal capacity. Let me give an overview of my current setup and calcs. Solar: renogy 400w system with 40A mppt controller. Going to run series parallel (2S2P). I'm in Texas, and the bulk of usage will be in the summer - no concerns about insolation and charging capability of my bank, because of low usage on the motor (.5 to .75hrs use daily). I am feeding that to 2 ampere time 200AH LiFePO4 batteries with 100a BMS (280a max) in parallel to get a total of 400AH with 200Amps current / 560amps max. My inverter is a sigineer 12v 120/240 3000W (9000W surge). I am protecting that with a 250a ANL fuse from battery to inverter. Finally, the motor I am trying to power is a 1.5hp dual voltage 120/240 that runs 1725RPMs at 15.4/7.7amps. Motor has a service factor of 1.15, meaning a top end current of 17.6/8.8. It's a code "E", 60hz.
So this is where things get tricky. The motor's "Locked Rotor Amps" based on it being code E is 62.4a at 120vAC, which translates to a spike of 7488 Watts. Inverter can handle, no problems there. My concern and question comes with the DC amps. If my calculations are correct, the specs above will induce a 689amp DC current for that instant of startup, which exceeds max rating of my battery bank BMS (560amps max) as well as my ANL fuse. I guess my question is: can the system setup I have handle this for the few hundredths of a second that is needed to overcome the inrush surge? Or do i need to size up my batteries to 24V, which would reduce current needed by half? In that scenario, I'd obviously also need to get a different inverter to do 24V.
So... what do we think? Are my DC volts too low to handle the inrush current, even at 1/120 second demand?
Me? I would just give it a go. Be sure to have a spare fuse handy ?.
I choked out my 2.8 kw generator and 3kw 48v WZRELB inverter on my 12,000 pound boat lift more than a few times.
After I began staggering the starts of my lift motors (one each side) the WZRELB would run it most times. The generator never could.
I eventually switched to a Sigineer Low Freq inverter which can start both motors at the same time.
Edit: I see I have repeated some info I posted above about 6 months ago. I thought this topic seemed familiar ?
I choked out my 2.8 kw generator and 3kw 48v WZRELB inverter on my 12,000 pound boat lift more than a few times.
After I began staggering the starts of my lift motors (one each side) the WZRELB would run it most times. The generator never could.
I eventually switched to a Sigineer Low Freq inverter which can start both motors at the same time.
Edit: I see I have repeated some info I posted above about 6 months ago. I thought this topic seemed familiar ?
Hedges
I See Electromagnetic Fields!
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- Mar 28, 2020
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Shoulda used AGM, not that newfangled LiFePO4 that needs a BMS that can't handle the current. 
689amp DC current is less than CCA for a decent car battery.
A good fuse can handle a surge. How about bypassing BMS and wiring inverter direct to battery. Have BMS relay activate a relay compatible with control circuit/switch of lift?
"even at 1/120 second demand?"
My measurement of a window AC unit was about 1/6 second, 5x nameplate rating.
689amp DC current is less than CCA for a decent car battery.
A good fuse can handle a surge. How about bypassing BMS and wiring inverter direct to battery. Have BMS relay activate a relay compatible with control circuit/switch of lift?
"even at 1/120 second demand?"
My measurement of a window AC unit was about 1/6 second, 5x nameplate rating.
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