Homebrew backup genset

[Weetabix]

I like that the last photo of the series has them powering a TV with it. That IS the most important thing.

[308Mike]

Mike, is there some issue with charging a regular 12v battery bank with home brew generators and then using the battery bank to provide power for the devices in question?

ETA: Eagle beat me to it

Wiz, the issue is not with the motor, it's the quality of the power being put out by the generator or inverter. For people who have large capacity inverters in their RVs, that's the way they're setup (the inverter pulling right from the high-capacity batteries). Check your inverter for the type of sine wave it puts out. USUALLY, the better quality power output is going to be more expensive (sometimes significantly more expensive) than the lower quality modified sine wave.

That's why the Honda gensets rated for computers and sensitive electronics are so easy to identify when comparing price vs wattage output. The 5000 watt gensets are $1400 difference (MSRP) between the two. Personally, I like the EU2000i Companion, 'cause you can daisy-chain them together for more power, it's very quiet, runs a long time (almost 10 hours) on a single gallon of gas, and not overly expensive. As a matter of fact, you could get TWO of those EU2000i Companion gensets and daisy-chain them for approx 4000 watts of power, with about the same cost/price as a single EU3000i Handi model - putting out only 3000 watts (with a pure sine wave).

I have my RV solar panels tied into my coach battery charger, so they can recharge my batteries during the day without my needing to run my noisy 4000 watt generator, or use my RV engine and alternator to charge my coach batteries. Other than my awning, my solar panels are my greatest RV investment. My 1850 watt inverter wasn't very expensive and can handle almost everything we need besides the roof air conditioner and/or residential coffee maker.

For efficiency's sake, make sure you set up your inverter as close as practical to your battery bank because DC electrical power drops off quickly as distance increases from the power source.

[randy]

Mike, is there some issue with charging a regular 12v battery bank with home brew generators and then using the battery bank to provide power for the devices in question?

Wiz, the issue is not with the motor, it's the quality of the power being put out by the generator or inverter....Check your inverter for the type of sine wave it puts out.

To some extent, I think you may be talking past each other somewhat.

Wiz, If you are running something directly from 12V dc, then charging the battery from the generator and then running the devices directly from the battery without the generator running will be fine. *

If you are running AC devices, then yes, Mike is quite correct that the quality of the sine wave from the inverter an be critical.

Part of the reason that as much of my comms gear, lights, etc are set up to be charged from DC, in addition to the losses you incur going through an inverter.

*Depending on the current and size of the battery, the battery bank can act as a filter for poor power characteristics from the generator. I once had a 12v power supply in my ham shack with a nasty 60Hz hum. I hooked it up to a 17Ah gell cell and ran the radio in parallel and the noise went away. Worked that way for years until the battery died and I finally bought a decent power supply.

[The Wizard]

Mike, is there some issue with charging a regular 12v battery bank with home brew generators and then using the battery bank to provide power for the devices in question?

Wiz, the issue is not with the motor, it's the quality of the power being put out by the generator or inverter....Check your inverter for the type of sine wave it puts out.

To some extent, I think you may be talking past each other somewhat.

Wiz, If you are running something directly from 12V dc, then charging the battery from the generator and then running the devices directly from the battery without the generator running will be fine. *

If you are running AC devices, then yes, Mike is quite correct that the quality of the sine wave from the inverter an be critical.

Part of the reason that as much of my comms gear, lights, etc are set up to be charged from DC, in addition to the losses you incur going through an inverter.

*Depending on the current and size of the battery, the battery bank can act as a filter for poor power characteristics from the generator. I once had a 12v power supply in my ham shack with a nasty 60Hz hum. I hooked it up to a 17Ah gell cell and ran the radio in parallel and the noise went away. Worked that way for years until the battery died and I finally bought a decent power supply.

Thanks, that's what I was wondering, if the quality of the electricity being produced from the generator mattered when it was being fed into a 12v battery bank and the battery bank was feeding the electronic devices. I understand that if using an inverter to get 110 AC power then the quality of electricity coming out of said inverter is important. I was thinking in terms of Generator->battery bank-> 12v electronics and generator-> battery bank-> inverter-> 110AC electronics. Was I understanding correctly that one shouldn't run the generator to charge the battery bank while having a 12v load (including inverter and inverter powered devices) attached and/or in use?

[blackeagle603]

*Depending on the current and size of the battery, the battery bank can act as a filter for poor power characteristics from the generator. I once had a 12v power supply in my ham shack with a nasty 60Hz hum. I hooked it up to a 17Ah gell cell and ran the radio in parallel and the noise went away. Worked that way for years until the battery died and I finally bought a decent power supply.

Yup, just a giant capacitor -- though batteries are surprisingly noisy in their own right. Burping, popping, spitting. Played havoc with the dc/dc invertor inputs on a Ku-band mobile sat terminal I spent years supporting. But that was some extreme stuff with crazy levels of isolation required from the TCXO.

[308Mike]

I understand that if using an inverter to get 110 AC power then the quality of electricity coming out of said inverter is important. I was thinking in terms of Generator->battery bank-> 12v electronics and generator-> battery bank-> inverter-> 110AC electronics. Was I understanding correctly that one shouldn't run the generator to charge the battery bank while having a 12v load (including inverter and inverter powered devices) attached and/or in use?

I think you have the right idea, but make sure you also include a voltage regulator in there to ensure your recharging facility can handle any/all the available voltage coming into your setup. It IS possible to not only use the generator to charge the batteries, but (depending on your setup), you can also use you devices WHILE also charging your batteries. THAT'S what the voltage regulator is for. You should be able to split the excess current to charge the batteries AND power your devices - IF you have enough current available to perform BOTH activities at the same time.

Example: I am able to not only run my RV generator to power my AC devices, but can also charge my batteries at the same time. My genset runs 110 VAC and charges not only my AC devices, but also charges my coach batteries (12 VDC) - AT THE SAME TIME. When I added solar panels, they were tied in (along with a voltage/AMP regulator) to be able to not only add to my system, but it too could also charge my batteries (even if they were in use - and if my current draw was less than needed to charge the batteries, my monitor would show a slight positive current display for charging, if the batteries were REALLY depleted, it would be a negative display on my digital panel).

It all depends on how you set it up. Other than my solar panels, the other most expensive hardware part of my solar setup was the regulator. My regulator capacity tops out at 20 AMPs, and with my 5 solar panels on my RV, the most I've ever seen is a little more than 10+ AMPs - coming from my solar panels.

It sounds to me like you're missing the power regulator to tie it all together to give you the flexibility you want/need to do what my RV has installed (although I didn't install it nor set it up - I relied upon a local experienced solar installer for guidance who'd been dealing with RVs for YEARS).

For emergency situations, I can't see how your setup would differ too much from my RV. From what I recall (and I had this explained and installed over a decade ago) = ALL power feeds into the regulator, which handles the charging of the batteries (as needed) and distributing power to the site (depending on draw), which is either 12VDC (one circuit) or 110VAC (with can also feed the battery charger if a DC charger isn't part of the loop, but more than likely they use a 110 VAC commercial charger to drop down to 12VDC to charge the batteries) - yet still have the capacity to run your other items from your captive (meaning not tied into the regular electrical grid) system - as long as you don't exceed the capacity of your system's rating (which also performs the job of power distribution), THEN into either the devices (if running 110 VAC), or into the battery charger, which handles charging the battery bank and should be able to do so if the batteries are in use, or simply being used to charge the batteries, which feed into the inverter, then out to your devices.

When running my RV's 4KW generator, I can not only run my 110VAC devices, but can also charge my coach batteries. And I suspect everything is running on 110VAC when the generator is running. When the generator is off, the solar panels charge the batteries, and EVERYTHING running off the inverter is pulling off those same coach batteries. EVERYTHING generating power helps charge the coach batteries, then when I need to run something AC and don't want to run the noisy generator, it pulls off the charged coach batteries for power. With my solar panels, I have yet to drain my batteries while not being hooked up to "shore" power (regular 110/120VAC power at hook-up sites or running the generator and/or using my engine alternator to power the batter recharging - which really hurts my MPG).

If you have the proper setup, you CAN not only run your generator and use your devices, but if you have enough current, you can also CHARGE your batteries at the same time (as I can when using my RV).

You need to also look into a power distribution regulator to add into to your system to give you MUCH more flexibility than your original design.

[The Wizard]

Would the (internal/external) voltage regulator that comes with the car alternator not be sufficient to do what you are talking about so as to show a need to have a second voltage regulator? After all we were talking about a home brew generator using a lawn mower engine and car alternator.

And also if a power distribution regulator were installed would it allow the flexibility to add something like solar PV panels at a later date and if PV panels were installed would that require the aforementioned second voltage regulator in addition to the solar charge controller or would the solar charge controller be enough?

[308Mike]

Wiz, I'm sorry, but this is getting beyond my knowledge to be able to effectively guide you in this regard.

I have NO DOUBT there are others with FAR more knowledge either on this site or other who may be able to further educate you regarding what you're trying to do (without purchasing additional equipment).

I wish you the best in your further endeavors and hope everything works out for what you're trying to do with minimal additional expense. If you can get it all to work out, and it works well, perhaps you can come back later and educate us regarding the issues you ran into and what you did to overcome them. I'd be very interested to know what happens/happened and how your project turns out!!

After all, I'm sure I'm not the ONLY one who would love to see how your project turns out and what you needed to do to make it all work seamlessly.

[The Wizard]

Well this started out as Eagles thread, I just thread jacked it because it is relevant to my interests too. Not being a mechanical or electrical engineer when I get around to building one I'll enlist the help of a couple people I know and WESCOG something together.

[Termite]

Guys, "apples and oranges" are getting mixed up here. I'm ditto-ing what Chris said, with few twists.

There are AC generators, which is the vast majority of generators, and there are DC generators, which are much less common.
If you are building a "homebrew" battery booster using a car alternator, that's a DC generator. The alternator on automobiles has a DC output, but it usually is not particuliarly "clean" DC. The car's battery "smooths" this DC signal out somewhat. So car alternators run by a Briggs & Stratton will work OK to charge batteries, but DO NOT try to run DC equipment directly from it, without having a battery as a signal pulsation dampener.
Additionally, charge rate also affects battery life. To keep from killling your batteries prematurely, do not have a charge rate greater than C/4. That is, your battery amp hour rating should be at least 4 times the charger's max amp output. IOW, a 200 amp hr battery should never be charged at greater than 50 amps for any significant length of time. The solar panel/offgrid folks consider C/10 to be about the best compromise between charge time vs battery life.

If you are going to run your house while also charging batteries, you will be using an AC generator and a battery charger, or invertor/charger.

For home generators, generally the cheaper the price, the "dirtier" the AC power output. This is difficult to explain to non-electrical folks, without being able to show it on an oscilloscope.
So if you are going to purchase a home generator, spend the money to buy a better quality one. Hondas are good, so are Yamahas. Generacs are OK, depending on which model.
MultiQuip is another good generator; they cater to the contracter crowd, and are pricey. I have one.

What you DO NOT want to buy is one of the 5000-5500 watt generators, for $599-$699.

I hope that helps explain things.