diy solar

diy solar

Boat Lift

SurfaceScratcher

New Member
Joined
Dec 9, 2019
Messages
7
Hello and thanks for the help. I have a boat slip that is the sole source of an electric bill. Now you probably don’t want to hear me complain that electric company goes up every month even though most months I use no electricity at all… so I won’t. (Oooops).

So, I want raise the boat up and down a few times a day, on a busy day. Most days it wont be used at all. The lifting unit is very typical and is powered by a 120 volt, 13 amp motor.

I've purchased an inexpensive 2500/5000 peak wattage pure sine inverter, thinking that the 1660 watts I’ll be asking of it would be covered.

I’ve also purchased a Renogy 50 watt starter kit. What I have not bought yet is a battery, although I have a newer marine battery that I've been experimenting (playing) with around the house.

The solar panel and controller, although entry level, do a very good job charging the batteries. The marine battery with the inverter can run the washing machine, my table saw and just about anything else around the house but when I take it to the boat lift, it will lower the boat but it doesn't have the grunt to get the motor started going up.

My inverter’s power comes on slowly, over a period of 2 or 3 seconds. I need all 13 amps at once. Did I buy the wrong inverter? Can someone recommend one that will rise to this task? Would some sort of capacitor addition fox my problem? Would better batteries guarantee a solution?

Finally, what would be a good battery for this system, remembering that I need approx 13 amps of power but only for a short period of time?
 
Somebody smarter will chime in, but I believe that you need a "hard start capacitor". It stores energy to help with starting motors/compressors that needs a lot of surge power. @Ped posed one earlier that might do the job for you. Having trouble finding it right now.

Please define "short period of time". Is it always the same boat with the same amount of weight in it?
 
Here is what @Ped posted earlier. Would this work for your application?

 
Of course it cant, thats over 1/c youre asking from a lead acid battery. Theyre only good for c/6. In plain speak youre asking 130A from a single 100Ah battery. Which is good for about 100/6 = 16.7A

You need a bunch more battery.

Or get AGM which can handle 2/c. You can get 3 100Ah or 2 6v 225AH.

Then theres lifepo4 which can handle .5/c or 200A from a 100ah battery.
 
This would be a good use case for a LTO battery for 400 bucks you can get 40Ah with a 400 amp discharge rate possible. If your lift took 5 minutes you would use 1/4 capacity per lift though. Although I suspect you are using it for even less time.
 
Thank
Of course it cant, thats over 1/c youre asking from a lead acid battery. Theyre only good for c/6. In plain speak youre asking 130A from a single 100Ah battery. Which is good for about 100/6 = 16.7A

You need a bunch more battery.

Or get AGM which can handle 2/c. You can get 3 100Ah or 2 6v 225AH.

Then theres lifepo4 which can handle .5/c or 200A from a 100ah battery.
Of course it cant, thats over 1/c youre asking from a lead acid battery. Theyre only good for c/6. In plain speak youre asking 130A from a single 100Ah battery. Which is good for about 100/6 = 16.7A

You need a bunch more battery.

Or get AGM which can handle 2/c. You can get 3 100Ah or 2 6v 225AH.

Then theres lifepo4 which can handle .5/c or 200A from a 100ah battery.
Thank you, I knew I was underpowered. Do all inverters spool up slowly like this one or will the proper ah batt fix that characteristic?
 
This one's identical to mine
That looks like it would be pretty easy to swap out if you could find a similar DC motor.

Belt reduction looks to be about 20:1 and the worm drive based on quick tooth count around 100:1. I would suspect your main/large gear turns about 10 RPM.

Your (pictured) motor is probably more than you really need with that gearing, but you should have a feel for how hard its working.

Ideally you would want a motor that accepts that pulley and fairly close on RPM.

Depends on whether you want to remove AC from your boat lift enough to take this on. You might get lucky and find a bolt on replacement.

Something like these two from a quick search.


 
Last edited:
My first suggestion should have been to contact your boat lift maker to see if they have a DC replacement motor. That motor looks pretty standard - search online for a bolt on DC replacement.

A quick google search with "DC powered boat lifts" has a lot of results.
 
This would be a good use case for a LTO battery for 400 bucks you can get 40Ah with a 400 amp discharge rate possible. If your lift took 5 minutes you would use 1/4 capacity per lift though. Although I suspect you are using it for even less time.
Where are you located @SurfaceScratcher
I'm in Brownwood TX, right in the center. Thanks for your concise recommendations. The lift takes approx 5 min. up and down, and I think I would be more comfortable with about twice that battery capacity. Can you recommend any particular battery?
 
That looks like it would be pretty easy to swap out if you could find a similar DC motor.

Belt reduction looks to be about 20:1 and the worm drive based on quick tooth count around 100:1. I would suspect your main/large gear turns about 10 RPM.

Your (pictured) motor is probably more than you really need with that gearing, but you should have a feel for how hard its working.

Ideally you would want a motor that accepts that pulley and fairly close on RPM.

Depends on whether you want to remove AC from your boat lift enough to take this on. You might get lucky and find a bolt on replacement.

Something like these two from a quick search.


Well, as the resident uber nubie, I never considered going DC. That makes sense. I'm working backwards from the lift, loosing power through the inverter....but, I suspect I'll continue down this road a little further. ;) Thanks for the insight.
 
If you do not need the AC power a dc motor would definitely be the way to go. I see some motors posted here and they draw far less watts than the original AC motor so Im curious as to weather or not they will have enough power.

Is there a formula as to how much energy it takes to lift X pounds Y feet in the air?

Not saying the motors listed wont work Im just wondering aloud as to how you are going to get 350 Watts to do the work of 1560 watts
 
Not saying the motors listed wont work Im just wondering aloud as to how you are going to get 350 Watts to do the work of 1560 watts
Where did you get 1560 watts? From the AC motor startup requirements?

The existing motor specs should provide the needed details to find a suitable DC replacement.
 
Last edited:
He says its a 120 Volt 13 amp motor. 120 * 13 = 1560
And not just once but 3 times! Sorry.

That does not look like a 2HP motor. With 2000:1 gear ratio in just that piece, that would lift a LOT with ease.

Hopefully OP can find a bolt on replacement DC motor.
 
Back
Top