Generator and variable input set output

Thread Starter

SwollenUvula

Joined Jul 3, 2020
6
Okay, so I am doing a stupid project. Lets say I have a small motor that I am going to be using as a generator. It can output up to 350w at 24vdc. I need something that can take ANY INPUT voltage dc and output it to 14.2v dc to charge a lead acid battery. I bought 2 boost converters off of ebay, but it's output is dependent on the input. (i.e. I applied 12.3v and it output 16.3 and i adjusted it down to 14.2v. I then applied 20v and it putput 20v??) Can someone PLEASE help me find something that can handle up to 24vdc 350w, input but output a constant non-input dependent voltage?
 

Papabravo

Joined Feb 24, 2006
18,422
What makes you think the output of a boost converter will be constant for any input? That is not how boost converters work. It sounds like what you want is a buck converter that will take 24VDC input and put 14.2 volts out. You may be able to move the input up or down a bit and still get 14.2 volts out, but it will NOT give 14.2 Volts out for any input voltage. That is not how buck converters work either.
 

Thread Starter

SwollenUvula

Joined Jul 3, 2020
6
What makes you think the output of a boost converter will be constant for any input? That is not how boost converters work. It sounds like what you want is a buck converter that will take 24VDC input and put 14.2 volts out. You may be able to move the input up or down a bit and still get 14.2 volts out, but it will NOT give 14.2 Volts out for any input voltage. That is not how buck converters work either.
Is there anything that can take any input voltage up to 24vdc and at least make it constant?
 

Reloadron

Joined Jan 15, 2015
6,585
You have a 24 VDC generator developing 350 watts and you want to charge lead acid battery at 14.2 VDC. That would be a 24 VDC 14.6 amp generator. If you expect to charge your battery at full generator current you will need a system capable of regulating your voltage down and also be able to deliver a higher current. You will want a DC to DC converter something like this. Google DC to DC converter and keep in mind how much current you want or need. Higher currents don't come cheap. You would likely do better with an automotive 12 V alternator than your 24 volt generator.

Ron
 

Papabravo

Joined Feb 24, 2006
18,422
Is there anything that can take any input voltage up to 24vdc and at least make it constant?
No. It is the any input voltage that is the problem. The immutable rule of DC-DC conversion schemes is that power out will always be less than power in. In some cases, the power out will be much less than the power in. I really hate to keep repeating myself, but you need to consider practical matters if you want any chance of finding a realizable implementation of your fever dreams.

If you follow the link in post #4, you will see that it specifies an input of 24 VDC nominal. without additional information, I would interpret that as perhaps, 24V ± 5%. The 14 V output then requires an approximate duty cycle of 14/24 = 58%. This is fairly typical of buck converters. You can't get close to either 0% or 100% duty cycle, but somewhere in the middle is just right. It is the same for most DC-DC converters that they tend not to work too well at the extremes of duty cycle.
 
Last edited:
Top