Boat Lift

[Supervstech]

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?

The issue you are having isnt the battery, or the motor... it is the inverter itself.

Motors have a startup draw surge.
Easy starts do reduce it, but nothing is going to eliminate it aside from the motor change.

A 13amp ac motor will pull over 50 amps on startup. An easy start can reduce that down to 26 or so, but no inverter rated close to the final watts of the motor will start it wuickly.

Switching to a pure dc motor could solve it, gates do it all the time on a sla battery.

I would think an ecm motor which is a true balanced 3 phase dc motor should run off the existing inverter... but 13 amps of 120v is 130amps at 12v... probably more like 150amps.
That picture looks like a 1725rpm shaded pole motor...

 

[Supervstech]

No, it appears to be a psc, I didnt see the cap bump at first.

 

[Supervstech]

I would change to a 240v motor, and get a 2500watt 230v cheapo inverter/charger... same watt draw, but a lower amperage. The motor would handle the load easier with less heat.

 

[Supervstech]

A boat lift has to PULL the sticky heavy boat out of the water, then support AND lift the weight, allow drainage etc, and keep lifting...
It is a difficult job.

 

[MisterSandals]

A boat lift has to PULL the sticky heavy boat out of the water, then support AND lift the weight, allow drainage etc, and keep lifting...
It is a difficult job.

Yea, but how big of a boat would someone put in and out of the water, multiple times a day?
OP, any pix of the setup?

And while your 240v motor idea is a potential solution, why not at least try to get a DC motor?
Availability? Cost? Other?

 

[SolarRat]

Is this a 4 pole lift? Doesn't it have two motors? Many of the boat lift motors I have worked on around here can be wired for either 120 or 240. Usually the plate on the side of the motor will say if so. Going to 240 will definitely help but it probably isn't absolutely necessary for such a short duration use.

Sounds like the inverter can't handle the surge. I assume it's a cheap high frequency inverter...a low frequency one would probably be able to kick that motor over, provided your battery is in good shape. A basic 100ah LA battery's cold cranking amps would indicate it has enough juice...I'd think (~500a for a deep cycle, higher for a starting batt). Once the motor is spinning the amp draw drops much lower (these things are geared waaay down).

First, I'd see if you could borrow a good LF inverter from somewhere to test it. 2000w peak should be enough to kick over one motor at a time, but higher is better.

I also wonder if the start capacitor could be changed to something beefier... Either that or the more expensive soft start devices...

 

[SolarRat]

Maybe I missed it but what size battery cables are going from the batt to the inverter? They should be at least 2/0 and as short as possible. Any voltage sag would make that inverter gag. Does the inverter give any error beep or ...?