Goboatingnow
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Maybe but people making videos also need to understand the fundamentals of dc design rather the camera angles and saying misleading things that’s gets reported on discussion forums.
Avoiding sulfation and loss of capacity: How frequently must I charge to 100%?
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MurphyGuy
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Yeah, its made for the high voltage battery systems. I pointed it out to show the beginning of a pattern, not to counter your statement.
With more and more battery backup systems coming on-line, it is only a matter of time before solutions start to catch up with the market.
I'll bet you Honda is the first to come out with a small 2000w 48 volt generator.
Goboatingnow
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Vigilant24
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I was pretty sure he'd have problems with that. These air cooled engines shed more heat/power to the air than they provide in electricity. So, if our generator is burning enough fuel to make 1000W, it's shedding more (maybe much more) than 1000W of heat to the air (like a small electric room heater). We can imagine how hot an insulated 6 cu ft box would get if we ran a 1000W room heater inside, even with some vent holes.
In a later video, it looks like he installed a big ventilation fan in (in a big open hole):
Anyway, a box is a good idea, but it needs to cool reasonably if the engine is to live a long life. Also, there's a vented tank of gasoline in there, and that's worth thinking about.
This guy did a pretty downtown job of making a hush box.
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Vigilant24
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Getting back to avoiding sulfation: This might be the >cheapest< way to make sure we can get a 12V battery pack back up to a high state of charge if solar power is unavailable: A simple industrial ("lawnmower") engine driving an automotive alternator. Yes, it requires some DIY McGuiver-ing, it's not very light, portable, or sexy.
This guy explains it well in a video:
"6HP" (ha!) engine running at an efficient power setting (about 2500 RPM, running steady), driving an automotive alternator to make 80 amps at about 14.5 V. That'll recharge a 400AH 12V battery pack at 0.2C, and take it from 50% to 90% SOC in about 2 hours.
It's not especially quiet (he's built a good muffler/exhaust hose, we could also address noise through the induction system and add a hush box). It requires a manual throttle adjustment once when started, and we'd need to turn it off. The voltage regulator on the alternator will provide good feed for the bulk charging of our batteries, but we'd need to do something else for the high-voltage, low amp saturation top-off charge. Even a cloudy day could probably provide that using solar. These engines are widely available everywhere, and the alternators are in every car part store. If you had to buy everything new (no curb-side rusted out lawnmower with a good engine), a Harbor Freight 212cc engine would cost $160 and the alternator is about $70. My suggestion would be to find a good new or used approx 200CC Honda or B&S engine. Everything is available locally, and the parts can be serviced (or easily swapped out) without drama. All of these engines are the same architecture (air-cooled pushrod overhead valves, with carburetors) and I don't think the sophisticated throttling of a modern inverter generator will offer substantial advantages in this case compared to an engine operating at steady RPM and manifold pressure right in the sweet spot of its BSFC curve.
Solar power is variable. Bigger and bigger battery banks to cover essential loads during infrequent lulls in solar availability becomes cost prohibitive, and leaving lead acid batteries at low SOC for days isn't good, either. So, a generator of some kind will make sense for many use cases if grid power isn't available.
This guy explains it well in a video:
"6HP" (ha!) engine running at an efficient power setting (about 2500 RPM, running steady), driving an automotive alternator to make 80 amps at about 14.5 V. That'll recharge a 400AH 12V battery pack at 0.2C, and take it from 50% to 90% SOC in about 2 hours.
It's not especially quiet (he's built a good muffler/exhaust hose, we could also address noise through the induction system and add a hush box). It requires a manual throttle adjustment once when started, and we'd need to turn it off. The voltage regulator on the alternator will provide good feed for the bulk charging of our batteries, but we'd need to do something else for the high-voltage, low amp saturation top-off charge. Even a cloudy day could probably provide that using solar. These engines are widely available everywhere, and the alternators are in every car part store. If you had to buy everything new (no curb-side rusted out lawnmower with a good engine), a Harbor Freight 212cc engine would cost $160 and the alternator is about $70. My suggestion would be to find a good new or used approx 200CC Honda or B&S engine. Everything is available locally, and the parts can be serviced (or easily swapped out) without drama. All of these engines are the same architecture (air-cooled pushrod overhead valves, with carburetors) and I don't think the sophisticated throttling of a modern inverter generator will offer substantial advantages in this case compared to an engine operating at steady RPM and manifold pressure right in the sweet spot of its BSFC curve.
Solar power is variable. Bigger and bigger battery banks to cover essential loads during infrequent lulls in solar availability becomes cost prohibitive, and leaving lead acid batteries at low SOC for days isn't good, either. So, a generator of some kind will make sense for many use cases if grid power isn't available.
Vigilant24
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That would be nice. It would cost less to produce than their 120VAC inverter unit. Ideally, put both options on the same product.
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Solar Wizard
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I ask again what's the point when you can just hook a battery charger up to a normal inverter generator? Who are they going to sell it to that only wants 12V charging but without the ability to power 120V stuff?
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MurphyGuy
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It's all about automation, and there's an energy conversion efficiency aspect as well. While your solution is totally functional, it's nice to have it automated.
For example, when our home goes off-grid, I turn on a couple of Sunny Islands in AC coupling mode. When a string of crappy solar days happens, I have to run the generator to get the batteries charged up. I could disconnect the battery and run straight off the generator, but that is a huge amount of wasted energy. So instead of just running off the generator, we continue on the battery and send the gen power into the Sunny Islands, which then use the juice to charge the battery bank.
As for 12 volt charging, I would agree its not a marketable item, but for us folks with large 48 volt whole-house off grid systems, it would probably be quite popular.
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Solar Wizard
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What would be the benefit of letting the sunny islands do the 48 to 120/240 conversion while charging? Is that not introducing the same inefficiency you claimed to be preventing by running a straight dc generator?
With a 120/240 volt gen, I can load the generator more and get better efficiency by running the house loads at the same time while letting the inverter/chargers do the work of charging the the now unloaded batteries.
Your method used a 48v gen that applies 48vdc to the batteries which is then applying power to the inverters to make your household voltage and charging your batteries in parralell.
Where is there any savings or benefit here? You're also stuck with no 120/240 if your inverters fail.
Vigilant24
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The Honda inverter generators already have approx 180VDC-220VDC available inside anytime they are running. If they modified their existing products (or added a new item number, or sold an aftermarket kit, etc) users could have the (present) clean 120VAC available AND have access to that high-voltage DC for easy and efficient step-down to any DC voltage required to charge their batteries (or, to add to their available battery DC current to power big loads through their existing inverter).
It's about flexibility, efficiency, and redundancy. More efficient battery charging from the generator (no loss to convert to AC and then immediately re-convert to DC through the a battery charger), more flexible powering of AC loads (from the receptacles on the genset directly, or choose to use another inverter, but with other DC augmented by DC from the generator). Redundancy: If the Honda inverter fails, the Honda DC power is still usable through another inverter.
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Solar Wizard
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It's not efficient to step down 200 volts dc to 12 volts dc.
Even that little gen would then have 200 amps available at what? Jumper cable clamps at the end of 0000 cables hooked to what kind of connectors on the generator? And all to do what?? Save maybe 3% in fuel and have to have your gen right next to your batteries.
Makes zero sense, at least to me.
MurphyGuy
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The Sunny Islands are providing power to the house. During the day, there is no 48 to 120/240 conversion due to the fact that they are AC Coupled. Basically, the grid tied solar inverters are powering the house in off-grid mode.
With Sunny Islands in Gen Charge mode, they can load the generator down to its maximum efficiency of around 80% capacity. The generator runs at a constant load and doesn't surge or choke. When I tell my Sunny Islands to draw 15 amps from my generator, that's exactly what they draw, 15 amps constantly regardless of the load in the house. This is the most efficient way to run a generator and produces the least amount of wear and tear on it.
It also allows me to charge the batteries up really quickly so the generator only has to run for 3 or 4 hours and I'm good for the next 24 hours.
Failures can always happen with anything from the inverters to the generator. That's why we keep backups and multiple ways of generating power.
A DC generator isn't the answer to all off grid systems, but when it comes to larger systems, it would simplify things quite a bit.
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Solar Wizard
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Oh. Was thinking off grid.
MurphyGuy
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You are thinking correctly, I was discussing off grid application. Our (normally) grid tied solar system can go into total off-grid mode using the battery storage system.
Vigo
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Lol. Sorta sounds like they just put a full bridge rectifier and a capacitor on the generator's 240vac output and.. charged more money im guessing? I didn't check the link, but im assuming they charged more money.
I put a push mower engine on a riding mower (and put a small crane on it too) and i was able to find a random V belt pulley from my box of random pulleys (car guy thing, long story) and i found a pulley with a pressed in bearing that i was able to press out, and the ID of that pulley was close enough that i was able to just press that pulley onto the top side of the push mower's 'blade hub'.
But even more interesting.. I found that the indexing 'nubs' and 9/16" central centering 'hub' actually correlate perfectly to the water pump snout and pulleys of many, many old RWD american vehicles. Which means, you can pick a desired pulley diameter water pump pulley from some old tank in a junkyard, have it center perfectly on your push mower blade hub, drill and tap the middle of the indexing 'nubs' for some hold-down bolts, and have a large enough pulley to get full rpm on the alternator without having to overspin the push mower engine.
These and other tips brought to you by 'a mad tinkerer who has done a lot of goofy shit'. ?
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Solar Wizard
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Lol. Sorta sounds like they just put a full bridge rectifier and a capacitor on the generator's 240vac output and.. charged more money im guessing? I didn't check the link, but im assuming they charged more money.
I put a push mower engine on a riding mower (and put a small crane on it too) and i was able to find a random V belt pulley from my box of random pulleys (car guy thing, long story) and i found a pulley with a pressed in bearing that i was able to press out, and the ID of that pulley was close enough that i was able to just press that pulley onto the top side of the push mower's 'blade hub'.
But even more interesting.. I found that the indexing 'nubs' and 9/16" central centering 'hub' actually correlate perfectly to the water pump snout and pulleys of many, many old RWD american vehicles. Which means, you can pick a desired pulley diameter water pump pulley from some old tank in a junkyard, have it center perfectly on your push mower blade hub, drill and tap the middle of the indexing 'nubs' for some hold-down bolts, and have a large enough pulley to get full rpm on the alternator without having to overspin the push mower engine.
These and other tips brought to you by 'a mad tinkerer who has done a lot of goofy shit'. ?
Yes you can throttle down but what most people don't think of and what the guy on Youtube found out is that cannot lower air cooled engine rpm or alternator RPM beyond what the cooling fan of either can provide for the load.
You can produce 100 amps at 3000 alternator RPM or 100 AMPS at 6000 alternator RPM.
At 3000 RPM the alternator's cooling fan is only providing half the air flow as it would at 6000 RPM. In regards to air-cooled engines with governors, same thing.
Vigo
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Absolutely! But it is important to get a large enough pulley on the engine side of things because you cannot speed up the gas engine all that much beyond its stock governed rpm without potentially putting your health and safety at risk. I think most people who are 'new' to the idea of making their own engine-driven alternator would overlook the pulley ratio that exists on most engine-driven alternators. For example, most cars have something like a 6" diameter crank pulley, and a 2-3" diameter alternator pulley. So to hit 3000 rpm on the alternator only requires ~1500 from the engine (which is why almost all alternator output tests say something about revving the engine to 1500-1800rpm, etc). You could easily have 'enough' engine power but put yourself in a situation where it was impossible to make it work well, with the wrong pulley ratio.
Riding mower engines are one thing because they typically have two pulleys available from the 'donor vehicle', the trans drive pulley and cutting deck drive pulley, and they are usually sized very differently and give you flexibility without having to fab on your own pulley. But on push mower engines, the only stock pulleys I have seen are for the self-propelled ones and that pulley is a TINY diameter that would not give you full power from the alternator because you probably can't spin the engine fast enough or get a small enough pulley for the alt, to get full power at a 'comfortable' engine rpm that's not making you wonder about connecting rod durability, or flywheel balance/harmonics etc.
So in my mind it's better to start with a larger pulley on the engine side, and shrink it or grow the alternator pulley as needed, vs having a small pulley on the engine side and trying to fix the alt speed with engine rpm. But still have to stay in a range that both can cool themselves, as you said.
If you run a 'regular' side-shaft 'universal small engine' you can just buy whatever pulley you want for it. Being able to scrounge pulleys only matters when you're 'repurposing' an engine with an odd shaft size or key arrangement because it's cheaper than buying a brand new side shaft from Harbor Freight etc. The more i talk the more i realize it's kind of a big subject and this thread isn't even about this so.. stopping there.
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Solar Wizard
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Agreed. Alternator spin fast good while Engine only spin kinda fast also good.
teal95
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I'm pretty sure it's 4x, not 2x. Most fans and aero drag are difference ^2.
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Solar Wizard
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I think you're thinking power to drive the fan, not the amount of air it moves.
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