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Small Cabin Forum / Off-Grid Living / battery charge with trolling motor
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vidaliaman
Member
# Posted: 2 Mar 2021 10:29
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has anyone tried to charge a battery reversing a trolling motor? i'm sure there are some adjustments to be made

dave

ICC
Member
# Posted: 2 Mar 2021 10:55
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Seems to me that "wheel" has already been invented.

Basically, a wind generator is a motor in reverse. Ditto a water generator. Etc.

How are you intending on turning the motor/generator?

vidaliaman
Member
# Posted: 2 Mar 2021 11:41
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i have a culvert emptying out a pond that is fed by a fast moving stream, my thoughts were to hook trolling motor to emptying end of culvert, allow stream to turn blade, use current to charge 2 deep cycle batteries,

gcrank1
Member
# Posted: 2 Mar 2021 11:54 - Edited by: gcrank1
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Ime (from trying to build a small windplant long ago) the small (tiny really) amount of amps generated would be so small as to, at best, only provide a trickle charge which wont actually 'charge' the battery(s) but maybe keep them topped up if already fully charged. Just like a little 10-15w solar panel on a car dash for a car in 'storage' can really only keep up with the self-discharge over time.
If you have enough flow you would be far better to build a hydro out of a 12v car generator or alternator but keep in mind they have to spin fast enough to put out at least 14.5v. You can test spin & measure output on the bench then try to figure out how to drive that fast to make the cut. Also, the more amps generated the more they 'load' the driving force; ie, they get harder to spin the more they generate.

vidaliaman
Member
# Posted: 2 Mar 2021 11:55
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i hooked a drill to the prop shaft and got 4 volts full blast and 2 volts at half speed, what do in need between the motor wires and the 12 volt battery to make sure battery is not over charged? new at off grid battery charging
thanks
dave

gcrank1
Member
# Posted: 2 Mar 2021 12:03
Reply 


The 'generator' has to put out more volts than the batteries to make them take a charge. That is why a car puts out 14-14.5ish volts for a 12v battery.
At 4&2v you might charge a cell phone with a usb port.

ICC
Member
# Posted: 2 Mar 2021 12:03
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Once the system was putting out enough volts to be used for charging, then the same type of charge controller that is used for a wind turbine, along with the dump load would be needed to prevent overcharging. But first you need to see if the moving water can actually spin the motor-generator fast enough to do much of anything.

vidaliaman
Member
# Posted: 2 Mar 2021 12:13
Reply 


great info, so i need to get greater than 12(13 or so) volts from motor to start with, if this is achieved then look for a controller and dump load?

gcrank1
Member
# Posted: 2 Mar 2021 12:40 - Edited by: gcrank1
Reply 


It actually needs to output 14+v, a '12v' battery is a nominal voltage, a typical 12v lead acid battery is fully charged when at 12.8v.
Your 'generator' needs to have overhead above that. A typical auto gen or alt puts out more than that and the regulator (or reg/rectifier for a alt) brings it down to the 14+.

ICC
Member
# Posted: 2 Mar 2021 12:41
Reply 


If we are talking about recharging a 12-volt lead-acid battery then you need to be able to push 14.4 volts or so into the battery to achieve a "normal" charging time. A lower voltage will work, it takes longer. Since this would be running 24/7 you could likely get away with a little less. That is why PV panels sold as "12-volt" panels actually put out about 17 in bright sun. There are losses within the charge controller.

vidaliaman
Member
# Posted: 2 Mar 2021 12:55
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thanks you guys you have answered some very basic question for a beginner

vidaliaman
Member
# Posted: 2 Mar 2021 13:00
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i found a treadmill motor i was able to get to 13v's, i will keep on working on it, thanks again

ICC
Member
# Posted: 2 Mar 2021 13:51
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https://permies.com/f/110/hydro

https://www.youtube.com/watch?v=0ieFZI4-6K8

ICC
Member
# Posted: 2 Mar 2021 13:52 - Edited by: ICC
Reply 


Oops, that ended up a duplicate

Brettny
Member
# Posted: 2 Mar 2021 15:17
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Front load washing machine motors are a good choice for this type of generator. They have alot of coils so dont need to spin fast to make power. Then you put the 3ph AC voltage through a rectifier and a charge controller and your all set.

If your making this powered by water flow out of a culvert you could do something a bit different with the dump load. You could make a diverter so the water dosnt hit the wheel when the battery is full.

FishHog
Member
# Posted: 2 Mar 2021 17:25
Reply 


If I had a flowing stream I'd build a water wheel, always wanted one for some reason.

But you could always just buy one of these
https://www.waterlilyturbine.com/?fbclid=IwAR1wEMmAYhjyvgURJeZ9RLsDwSCaCB5ZiD6snQagLQ 69DPh7O32g0IZXLPA

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