Making a wind turbine, how to stop it overcharging battery?

[beany_bot]

Hi, I plan to make a simple 12v-battery trickle charger wind turbine that I will put on the roof of my garage and connect to my jetski to keep it topped off during winter when my solar panel is performing poorly.

I have a 24v Motor I will use and will use a bicylce wheel for the "blades". I was wondering, on the off chance that my battery gets to 100% capacity. How do I stop the charging?
I thought about putting a Zener Diode in the circuit so that it would sent the voltage back to the motor but this raised two questions.

The fan may be making anywhere up to 20v I estimate (depending on wind) but very low amps. Not a problem for the battery but this would surely trip the Zener diode by itself? OR will the zener only detect/trip with voltage coming back the otherway? i.e. voltage from the battery.

Also what will happen if the voltage is sent back to the motor? Will it just try and turn it in the opposite direction? effectively "braking" the motor? Will that energy just be lost as heat?

Sorry for the perhaps silly questions but I have very little knowledge about these things. Just thinking on the fly here.

P.S. I do use the JetSki in winter.

 

[anorlunda]

A charge current of 2 amps or less is considered a trickle charge. You can leave it on forever without overcharging your lead acid battery. It is lead acid, Correct?

 

[beany_bot]

Yes, lead acid. I would be surprised if the setup would make more than 2 amps. Its quite a small battery though. 18Ah

 

[anorlunda]

If you want total safety, buy a cheap charge controller. Here is MPPT controller for $2.32 plus shipping. Real cheap https://www.amazon.com/dp/B01CX6WVFU/?tag=pfamazon01-20