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electrical:inverter [2024/04/05 12:23]
frater_secessus [Sizing your inverter] 		electrical:inverter [2025/01/01 11:24] (current)
frater_secessus [differences from shore power 120vac]
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 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))
  
-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" 
 + 
  
 ===== efficiency ===== ===== 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. 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.
  
-50w * 0.8 efficiency = 60w demanded from the system+50w / 0.8 efficiency = 60w demanded from the system
  
  
 ===== Modified Sine Wave ===== ===== Modified Sine Wave =====
-Originally called "square wave" inverters, MSW inverters are inexpensive and ubiquitous.  If your inverter doesn't say it is MSW or PSW then it is probably MSW.+ 
 +Note:  modified //square// wave is more accurate but relatively uncommon in marketing. 
 + 
 +MSW inverters are inexpensive and ubiquitous.  If your inverter doesn't say it is MSW or PSW then it is probably MSW.
  
 Pro:    Pro:   
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 > One way that I used to check computer/electronic power supplies... take a [[https://amzn.to/2XKSFfp|Kill-a-Watt meter]] and measure the power factor. If it was >0.9, it probably would work fine -- BB((https://forum.solar-electric.com/discussion/comment/191612#Comment_191612))((power factor is the PF button on the kill-a-watt)) > One way that I used to check computer/electronic power supplies... take a [[https://amzn.to/2XKSFfp|Kill-a-Watt meter]] and measure the power factor. If it was >0.9, it probably would work fine -- BB((https://forum.solar-electric.com/discussion/comment/191612#Comment_191612))((power factor is the PF button on the kill-a-watt))
 +
 +Appliances with motors tend to run poorly and hotter than usual. 
  
  
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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).
  
-==== smallest uses ====+==== special case:  tiny loads ==== 
 +[[https://amzn.to/43RbueW|{{ https://m.media-amazon.com/images/I/81-P5bKVCzL._AC_UL320_.jpg?125}}]]
  
-For ~120w loads you can use a small inverter intended for the cigarette lighter port.  They are typically fused at 10A, hence the wattage limit (12v x 10A = 120w).   
  
-If you go this route, consider using [[https://amzn.to/3UgnTWF|a soft wire extension]] so the inverter can rest on a flat surface.  That way it is not hanging out of and stressing the already-delicate ciggy port. +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))   
 + 
 +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.  
 + 
 +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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 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. 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.
  
-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/))+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/)) 
 + 
 +===== cooling ===== 
 + 
 +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.   
 + 
 +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.  
 + 
 + 
 +===== running big loads at lower power ===== 
 + 
 +see [[electrical:triac|this experimental article]]
  
  
 ===== sharing power ===== ===== sharing power =====
  
-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.
  
 ===== differences from shore power 120vac ===== ===== differences from shore power 120vac =====
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 > In fact, the situation with an inverter is very similar to [a] 240 VAC circuit... which has 2 120 VAC lines driven 180 degrees out of phase, i.e., "push-pull."((http://thesurvivalpodcast.com/forum/index.php?topic=63891.msg758502#msg758502)) > In fact, the situation with an inverter is very similar to [a] 240 VAC circuit... which has 2 120 VAC lines driven 180 degrees out of phase, i.e., "push-pull."((http://thesurvivalpodcast.com/forum/index.php?topic=63891.msg758502#msg758502))
 +
 +
 +===== types of setups =====
 +
 +[for simplicity this section assumes 120vac and 12vdc and makes broad generalizations -- secessus]
 +
 +Most **campervans** have a simple setup:
 +
 +  * battery bank -> 12v loads
 +  * battery bank -> inverter -> 120vac outlet[s]
 +  * [other forms of charging/power ignored for the purpose of this section]
 +
 +Vintage **"conversion" vans** might have
 +
 +  * battery bank -> 12v loads
 +  * shore power -> 120vac distribution (120vac loads only run when plugged into shore power)
 + 
 +Since **Class A and Class C RVs** are expected to be on pedestal power at RV parks much of the time and run huge loads like air conditioning, water heaters, and clothes washers they often have robust 120vac setups that can pass through shore power when available and use the inverter when it is not:
 +
 +  * shore power((or [[electrical:generator|generator]])) -> **transfer switch**((automatic or manual)) -> 120vac loads
 +  * battery bank -> inverter -> **transfer switch** -> 120vac loads
 +
 +Very **small RVs** like popups, A-frames, truck campers, etc, with modest loads might have
 +
 +
 +  * shore power -> converter/charger -> battery bank 
 +  * battery bank -> inverter -> 120vac outlets 
 +
 +There are losses inherent in 120vac -> 12vdc -> 120vac but 1) we're on shore power; and 2) the loads concerned are usually quite light.  This setup might also have a dedicated 120vac outlet that only works when shore power is connected. 
 +
 +
 +
 +
  
electrical/inverter.1712334238.txt.gz · Last modified: 2024/04/05 12:23 by frater_secessus

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