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electrical:inverter [2021/08/20 20:15]
frater_secessus [MSW and electronics] |
electrical:inverter [2024/04/18 00:01] (current)
frater_secessus [Inverters] |
| It is **more efficient to use DC power directly** whenever possible. In particular it is more efficient than running a laptop of phone charger off an inverter.((http://www.cheaprvliving.com/forums/Thread-Here-s-one-for-you-inverter-lovers)) | It is **more efficient to use DC power directly** whenever possible. In particular it is more efficient than running a laptop of phone charger off an inverter.((http://www.cheaprvliving.com/forums/Thread-Here-s-one-for-you-inverter-lovers)) |
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| AC-only items will require an inverter. [[electrical:12v:wallwart|Devices that run off a "wall wart" adapter]] almost never require an inverter. | Note: **only AC loads will require an inverter**. [[electrical:12v:wallwart|Devices that run off a "wall wart" adapter]] that output DC almost never require an inverter. Things that charge off USB (phones, fans, tablets, etc) can use a [[https://amzn.to/3JmopvO|12v-to-USB port]]. Laptops often have car chargers that run off 12v ([[https://amzn.to/3Wax1Nw|example]]). Search for "[specific make/model] car charger" |
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| | ===== efficiency ===== |
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| | Inverting from DC to your local shore power spec will necessarily incur losses. These might be 10-30%, depending on the inverter, the inverter's efficiency spec, etc. In the absence of hard information you might use 20% losses as a rule of thumb. This means it will require 20% more power to run your load than the rating spec. |
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| | 50w * 0.8 efficiency = 60w demanded from the system |
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| * widely available | * widely available |
| * works for many/most AC items | * works for many/most AC items |
| * generally more efficient under no load (?) | |
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| Con: | Con: |
| > In the end, probably 80% of the stuff you plug in will work fine [on MSW], 10% will fail pretty quickly, and the other 10% it will be difficult to tell. -- BB((https://forum.solar-electric.com/discussion/comment/191612#Comment_191612)) | > In the end, probably 80% of the stuff you plug in will work fine [on MSW], 10% will fail pretty quickly, and the other 10% it will be difficult to tell. -- BB((https://forum.solar-electric.com/discussion/comment/191612#Comment_191612)) |
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| there is anecdotal evidence that MSW can damage some electronics. The most commonly repeated stories are Dewalt cordless tool battery chargers and laptop chargers. | While MSW powers resistive loads like crockpots and coil heaters perfectly, there is anecdotal evidence that MSW can damage some electronics. The most commonly repeated stories are Dewalt cordless tool battery chargers and [[electrical:12v:laptop|laptop chargers]]. Milwaukee battery chargers may also require PSW.((https://www.electriciantalk.com/threads/cordless-chargers-and-inverters.40405/post-754431)) |
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| Laptop chargers that work on MSW will usually run somewhat warmer and may buzz. Laptop chargers that will not work on MSW tend to get hot, not power on at all (no light), or cycle on/off. Laptop chargers and other power supplies might be tested thusly: | Laptop chargers that work on MSW will usually run somewhat warmer and may buzz. Laptop chargers that will not work on MSW tend to get hot, not power on at all (no light), or cycle on/off. Laptop chargers and other power supplies might be tested thusly: |
| * 433MHz remote radio controlled plugs((https://diysolarforum.com/threads/what-really-requires-a-pure-sine-inverter.22574/post-266515)) | * 433MHz remote radio controlled plugs((https://diysolarforum.com/threads/what-really-requires-a-pure-sine-inverter.22574/post-266515)) |
| * asynchronous motors with a capacitor to build up the 90° phase do not run well on MSW((https://diysolarforum.com/threads/what-really-requires-a-pure-sine-inverter.22574/post-266767)) | * asynchronous motors with a capacitor to build up the 90° phase do not run well on MSW((https://diysolarforum.com/threads/what-really-requires-a-pure-sine-inverter.22574/post-266767)) |
| | * hair clippers |
| | * In [[https://www.youtube.com/watch?v=wimTJw_Gpgk|an apples-to-apples comparison]] knurlgnar24 found a microwave to run 10% less efficiently and at 20% less power on MSW. |
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| | Also see [[https://www.reddit.com/r/diySolar/comments/yyd20a/pure_sine_wave_inverters_what_is_real_and_what_is/ix136m7/|this technical post]] on the topic by therealtimewarren. |
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| ===== Pure Sine Wave ===== | ===== Pure Sine Wave ===== |
| * Not as widely available as MSW; you may not find them at truck stops, big box stores, etc. | * Not as widely available as MSW; you may not find them at truck stops, big box stores, etc. |
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| | Not all PSW are prohibitively expensive. Bestek makes [[https://amzn.to/3N4YE3S|a 300w PSW for about $50]]. See [[https://www.amazon.com/gp/customer-reviews/R3UKQ7A0GQ196N/ref=cm_cr_dp_d_rvw_ttl?ie=UTF8&ASIN=B07KQ4Q2L5|the top-rated review]] for oscilloscope testing and limitations. |
| ===== inverter chargers ===== | ===== inverter chargers ===== |
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| {{ https://m.media-amazon.com/images/I/61wb7PGYPNL._AC_UL320_.jpg?150}} \\ | {{ https://m.media-amazon.com/images/I/61wb7PGYPNL._AC_UL320_.jpg?150}} \\ |
| An //inverter charger// performs several functions: | |
| | //Inverter/chargers// are most often found on rigs that are on shore power much of the time and run heavy AC loads |
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| | It provides several functions: |
| - invert 12v battery power to 120vac | - invert 12v battery power to 120vac |
| - pass-through shore power when available | - pass-through shore power when available, with auto-switching |
| - some can bond shore and battery power to support heavy 120vac loads | - some can bond shore and battery power to support heavy 120vac loads |
| - charge battery banks like a [[electrical:converter|converter]] | - charge battery banks like a [[electrical:converter|converter]] |
| | - some also handle solar charging |
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| They tend to be [[https://amzn.to/2KMcImw|expensive]], some over $1000. | They tend to be [[https://amzn.to/2KMcImw|expensive]], some over $1000. |
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| | Note: the Victron Multiplus line has outputs for maintaining the starter battery: |
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| | >> The main DC terminal can supply the full output current. The second output, intended for charging starter battery, is limited to 4A and has a slightly lower output voltage.((https://www.victronenergy.com/upload/documents/Manual-MultiPlus-3k-120V-(firmware-xxxx4xx)-EN.pdf)) |
| ===== Sizing your inverter ===== | ===== Sizing your inverter ===== |
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| Once you have made your MSW vs. PSW decision the next step is **sizing the inverter** (picking the right capacity). | Once you have made your MSW vs. PSW decision the next step is **sizing the inverter** (picking the right capacity). |
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| Note that to **actually power the inverter** you will need something like a 1:1 ratio of panel:inverter on flooded lead and 1:2 on AGM or lithium.((https://www.solarpaneltalk.com/forum/off-grid-solar/solar-living/15554-how-to-increase-solar-panel-output-amps?p=181738#post181738)) This would mean 400w of solar to run a 400w inverter (dipping into the battery as needed) or 400w of solar for 800w of inverter on AGM/Lithium, which have greater throughput. | ==== special case: tiny loads ==== |
| | [[https://amzn.to/43RbueW|{{ https://m.media-amazon.com/images/I/81-P5bKVCzL._AC_UL320_.jpg?125}}]] |
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| | For ~120w loads you can use [[https://amzn.to/4cMWwdW|a small inverter]] intended to be powered by the [[electrical:12v:ports#the_cigarette_outlet|cigarette lighter port]]. The ports are typically fused at 10A, hence the ~120w wattage limit (12v x 10A = 120w).((technically you could use any size inverter as long as you remembered not to draw >10A)) |
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| | Note: Ciggy ports are already prone to failure and poor connections. An inverter that hangs out of the socket will make matters worse. To avoid stressing the socket you can use an inverter with a built in power cord (as pictured above). If you already own [[https://amzn.to/4aLoUuT|one designed to live in the socket]]((don't buy this!)) consider using [[https://amzn.to/3UgnTWF|a soft wire extension]] that will allow you to relocate the inverter. |
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| | In any case, find out what kind of fuse your ciggy port uses and have some on hand. Mistakes are easy to make and easy to fix (if you have the spare fuse waiting). |
| ==== estimating your needs ==== | ==== estimating your needs ==== |
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| You will need to know the largest draws you will need to meet **at the same time**. If your TV is 40w, and your your laptop is 100w you would need (40w + 100w) * 1.10((inverter losses)), or an inverter that can power at least **154w**. | You will need to know the largest draws you will need to meet **at the same time**. If your TV is 40w, and your your laptop is 100w you would need (40w + 100w) * 1.10((inverter losses)), or an inverter that can power at least **154w**. |
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| Note that motorized equipment like drills likely have **greater current requirements for startup and for running**. Be sure to meausure both startup and running (see below). There are tricks you can use to minimize the start load, like starting a sewing machine at a low-load position((http://www.cheaprvliving.com/forums/Thread-Is-it-possible-to-Boondock-with-an-electric-sewing-machine?pid=165956#pid165956)), or //easing// into the trigger of a variable-speed power tool. | Motorized equipment like drills likely have **greater current requirements for startup and for running**. Be sure to measure both startup and running (see below). There are tricks you can use to minimize the start load, like starting a sewing machine at a low-load position((http://www.cheaprvliving.com/forums/Thread-Is-it-possible-to-Boondock-with-an-electric-sewing-machine?pid=165956#pid165956)), or //easing// into the trigger of a variable-speed power tool. |
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| | Note that to **actually power the inverter** without voltage sag or dipping so much into battery capacity you may want need something like a 1:1 ratio of panel:inverter on flooded lead and 1:2 on AGM or lithium.((https://www.solarpaneltalk.com/forum/off-grid-solar/solar-living/15554-how-to-increase-solar-panel-output-amps?p=181738#post181738)) This would mean 400w of solar to run a 400w inverter (dipping into the battery as needed) or 400w of solar for 800w of inverter on AGM/Lithium, which have greater throughput. |
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| [[https://amzn.to/3ptHIbX|{{ https://m.media-amazon.com/images/I/61FOAk4UA5L._AC_UL320_.jpg?75}}]] | [[https://amzn.to/3ptHIbX|{{ https://m.media-amazon.com/images/I/61FOAk4UA5L._AC_UL320_.jpg?75}}]] |
| The best way to understand how much your 110v equipment needs during startup/running is to use a **power monitor** like the [[https://amzn.to/3ptHIbX|Kill A Watt]]. You may be pleased to find that some appliances run at much lower power than their labeling would suggest.((the label likely has to list the highest-possible wattage draw under any conditions)) It is rare to find a device that pulls more than the label states. | The best way to understand how much your 120vac equipment needs during startup/running is to use a **power monitor** like the [[https://amzn.to/3ptHIbX|Kill A Watt]]. You may be pleased to find that some appliances run at much lower power than their labeling would suggest.((the label likely has to list the highest-possible wattage draw under any conditions)) It is rare to find a device that pulls more than the label states. |
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| Kill A Watts may be available for loan from your public library.((http://www.cheaprvliving.com/forums/showthread.php?tid=26835&pid=337451#pid337451)) | Kill A Watts may be available for loan from your public library((http://www.cheaprvliving.com/forums/showthread.php?tid=26835&pid=337451#pid337451)), and sometimes used at thrift stores. |
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| The buttons on the traditional Kill-a-Watt have two functions each. You press the button repeatedly to see the information: | The buttons on the traditional Kill-a-Watt have two functions each. You press the button repeatedly to see the information: |
| * **Watt / VA** | * **Watt / VA** |
| * **Watt** - this reading is the most important thing for load assessment. Add 10%-20%((depending on your inverter's efficiency)) to tell how much power the appliance will actually consume. | * **Watt** - this reading is the most important thing for load assessment. Add 10%-20%((depending on your inverter's efficiency)) to tell how much power the appliance will actually consume. |
| * Volt-Amperes is //apparent power//, not directly useful. | * Volt-Amperes is //apparent power//, normally not directly useful. If you have a device that is unexpectedly tripping an inverter (200w load tripping 300w inverter when powering on) you might watch VA to see if apparent power is >300w; this can happen with some loads. For this reason some inverters are rated in VA rather than W. See Power Factor below. |
| * **Hz / PF** | * **Hz / PF** |
| * Hertz - as with Volts, you can check your inverters AC frequency with this. In the US it is 60Hz. | * Hertz - as with Volts, you can check your inverters AC frequency with this. In the US it is 60Hz. |
| * **Power Factor** - this reading can be indirectly useful. One rule of thumb is that [[https://forum.solar-electric.com/discussion/comment/191612#Comment_191612|devices with a PF of >=.90 are good candidates for MSW inverters]]. A resistance heater may have a perfect 1.0 power factor and works great on MSW. A laptop charger or other wall wart might have a PF of .040 - .60, which suggests it might overheat on MSW. | * **Power Factor** - this reading can be indirectly useful. It is a relationship between Watts and VA (see above). One rule of thumb is that [[https://forum.solar-electric.com/discussion/comment/191612#Comment_191612|devices with a PF of >=.90 are good candidates for MSW inverters]]. A resistance heater may have a perfect 1.0 power factor and works great on MSW. A laptop charger or other wall wart might have a PF of .040 - .60, which suggests it might overheat on MSW. Also see [[https://www.youtube.com/watch?v=Tv_7XWf96gg|this video]] about power factor. |
| * **kWh / Hours** | * **kWh / Hours** |
| * **kWh** are 1,000w-hours. This is the actual amount of power used over time | * **kWh** are 1,000w-hours. This is the actual amount of power used over time |
| ==== understanding the specs ==== | ==== understanding the specs ==== |
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| Inverters are generally **rated in watts**. | Inverters are generally **rated in watts** in terms of continuous resistive loads (heatihg elements, etc). Inductive loads (things with motors, some electric blankets, etc) can draw more than their rated wattage and overpower the inverter. Plan accordingly. |
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| While there are both **peak** and **continuous duty** ratings it is common for marketers to advertize only the peak rating.((http://www.cheaprvliving.com/forums/Thread-PROBLEM-Dorm-fridge-won-t-run-on-1000-watt-inverter?pid=86851#pid86851)) The peak rating is only for short bursts of heavy draw. | While there are both **peak** and **continuous duty** ratings it is common for marketers to advertize only the peak rating.((http://www.cheaprvliving.com/forums/Thread-PROBLEM-Dorm-fridge-won-t-run-on-1000-watt-inverter?pid=86851#pid86851)) The peak rating is only for short bursts of heavy draw. |
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| | Stand-by power ((parasitic draw when no loads are present)) may be a factor when an inverter is run for many hours. The inverter drops to a power-saving mode then checks regularly to see if any load has been added. |
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| | * [[https://diysolarforum.com/threads/victron-power-save-modes-a-short-explanation.33621/|an explanation]] of Victron inverter power save modes |
| | * Renogy inverters >700w appear to have a power saving mode |
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| Most inverters will shut off if they get too hot, or if the input voltage is beyond certain points. | Most inverters will shut off if they get too hot, or if the input voltage is beyond certain points. |
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| The low voltage cutoff is to protect your batteries from [[electrical:depth of discharge|over-discharge]]. The high voltage cutoff is to protect the inverter itself. | The low voltage cutoff is to protect your batteries from [[electrical:depth of discharge|over-discharge]]. The high voltage cutoff is to protect the inverter itself. In addition, [[https://forum.solar-electric.com/discussion/comment/419096#Comment_419096|the current consumed by the inverter may increase]] as bank voltage drops. |
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| | HandyBob((https://handybobsolar.wordpress.com/)) reminds us that //"Properly adjusted solar systems with temperature compensation [for lead batts] will regularly exceed the 15 volts many inverters use as a high voltage shut down."//((https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/)) |
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| | ===== cooling ===== |
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| | Most inverters have fans to pull cooler air through them. Some do this only when they are too warm, or at a given power output regardless of temp, and some run 100% of the time. |
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| | If your fan runs only when hot, do not turn off the inverter until the fan has cooled the insides and stopped running. With continuous running fans put your hand on the inverter after the load is stopped to feel when it is safe to power off the inverter. |
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| | ===== running big loads at lower power ===== |
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| HandyBob((https://handybobsolar.wordpress.com/)) reminds us that //"Properly adjusted solar systems with temperature compensation will regularly exceed the 15 volts many inverters use as a high voltage shut down."//((https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/)) | see [[electrical:triac|this experimental article]] |
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| ===== sharing power ===== | ===== sharing power ===== |
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| Because higher voltage power has less losses over long wires, it may be most efficient to share power between RVs as 120v. The donor vehicle would invert to 120v, plug in an extension cord to their inverter and run it to the recipient. The recipient could plug it cord into their [[electrical:shore_power|shore power]] inlet or use it as 120v. | Because higher voltage power has less losses over long wires, it may be most efficient to share power between RVs as 120v. The donor vehicle would invert to 120v, plug in an extension cord((outdoor rated and approprate gauge)) to their inverter and run it to the recipient. The recipient could plug it cord into their [[electrical:shore_power|shore power]] inlet or use the end of the extension cord directly. |
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| ===== differences from shore power 120vac ===== | ===== differences from shore power 120vac ===== |
