DC motor as generator

Question

Hello everyone,
This question might have been asked somewhere else but I was not able to fand any other posts regarding my question, if there are please link them and i will delete this post, so I don't waste anybody's time.

I was recently looking into making a generator. I found some glow engines that don't cost alot (I am on a budget) like this one from ali express (I can also buy from other websites, this one just showed up first): https://www.aliexpress.com/item/GO-Engine-18th-methanol-engine-3-0CC-Without-Glow-Plug-for-1-10-on-road-Buggy/32804111807.html?spm=2114.search0204.3.287.c3ltkE&ws_ab_test=searchweb0_0,searchweb201602_5_10152_10065_10151_10068_5430020_5410020_10304_10307_10137_10060_10302_10155_10154_5370011_10056_10055_10054_10059_100031_10099_5400020_10103_10102_10052_10053_10142_10107_10050_10051_5380020_5390020_10084_10083_10080_10082_10081_10177_10110_10111_5420020_10112_10113_10114_10312_10313_10314_10315_10078_10079_10073,searchweb201603_16,ppcSwitch_5_ppcChannel&btsid=982ac520-824a-4967-816b-8c0d979ee8e4&algo_expid=9ff6c1ab-f534-4c27-94b5-31bdddab7c71-39&algo_pvid=9ff6c1ab-f534-4c27-94b5-31bdddab7c71

And I was looking around for a dc motor But I don't know which one to pick. Should i be brushed or brushless? What rpm? what voltage? what amp rating? I heard some motors generate AC and others dc?

I am looking to power something like a buck boost converter to charge 5v things (like phones or camping lights... etc).
Will it provide enough power for these appliances?

Thanks in advance.

Vince

jw0752 · Answer

Hi Vince,

If you are doing this project for the fun of building a motorized generator then you should proceed but from your question and description it sounds like you may have a difficult path. A motor will generate electricity if it is turned by a source of power such as a gasoline engine if it is of the proper design. Permanent magnet motors would probably be the best choice as you would not have to energize a field coil on the motor. If your goal is to have an independent source of electricity then I would look for a small or used generator and by pass all the hassle trying to integrate engines and motors to do things they are not really designed to do. For example you will need some way to regulate the voltage output of the motor (turned generator) and you will need some way to regulate the RPM of the engine. If you can find a small commercial electric generator then the pieces will all be designed and fitted to do the job of generating electricity and you will have the proper voltage to attach your electronic devices and loads without the need of more converters.

John

jw0752 · Answer

Hi Vince, Here is an example of what I am talking about: https://www.amazon.com/PowerPro-56101-Starting-Portable-Generator/dp/B00J261PGQ/ref=sr_1_5?ie=UTF8&qid=1502551377&sr=8-5&keywords=Generator You can probably find used ones like this for not much more that the cost of the engine you were looking at. John

dougw · Answer

That is a beast of a motor. It can produce over 1300 Watts which is 91 amps at 14.7 Volts - more than enough to charge anything, including car batteries. It could easily run an alternator from a car or motorcycle, but would need to be geared down to 2000 rpm. Gearing and pulleys will likely be your biggest challenge. You probably want a car battery or a LiFePO4 battery to tame the output, followed by a DC-DC converter for your 5 volt requirements. This way you wouldn't need to run the motor very often to charge up the big battery.

balearicdynamics · Answer

In past I had one to power the lights when doing out door photo sessions with models. These cheap versions are very bad controlling the fuel engine RPM and consequently the output power is so unstable to broke any kind of device as far as I saw. There are well working ones instead like the CAT devices that costs about 10 times By the contrary of what you can imagine, these cheap generators are instead perfect to power battery laptop just because the power does not reach directly the device. If you try to attach a sync flash for photography or a light spot it is a mess. Enrico

jw0752 · Answer

Hi Enrico, You make a very good point and it also highlights the likely outcome of building ones own engine motor combo to make a generator. If the inexpensive commercial ones are poorly regulated it is even more likely that a home made combo of hobby engine and motor will be very difficult to regulate and control. John

vinceverc · Answer

Thank you for the quick answer, this project is mainly for fun. Because I am interested in electricity and engines. I was just wondering would a step up/ step down voltage regulator do the trick for having a stable voltage?
PS: Like I said it is just for fun, but I might use it once or twice if something evere were to happen with the electricity in our street ( for example if there is a local power outtage to charge a phone (directly of the 5 volt regulator I suppose).

DC motor as generator

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