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lifestyle:faq_solar_generator [2019/11/16 09:16]
frater_secessus wisdom
lifestyle:faq_solar_generator [2020/05/20 08:40] (current)
frater_secessus [Charging from solar panels]
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 Words of wisdom: ​ "These aren't aimed at people that know what they are doing."​ -- [[https://​www.reddit.com/​r/​vandwellers/​comments/​dr387z/​500w_aimtom_rockpals_500_solar_generator_review/​f6jc7lz/​|LastTreeStar]] Words of wisdom: ​ "These aren't aimed at people that know what they are doing."​ -- [[https://​www.reddit.com/​r/​vandwellers/​comments/​dr387z/​500w_aimtom_rockpals_500_solar_generator_review/​f6jc7lz/​|LastTreeStar]]
 +
 +
 +> The self contained units are overpriced, underperforming "power for dummies"​. ​ -- Somebodyelse((https://​www.promasterforum.com/​threads/​run-engine-idle-to-charge-house-batteries.90688/​post-706125))
  
 ====== solar generators ====== ====== solar generators ======
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   * a pure sine wave [[electrical:​inverter|inverter]]   * a pure sine wave [[electrical:​inverter|inverter]]
    
-These devices are packaged for convenience and are usually much more expensive than the components bought separately.+These devices are packaged for convenience and are usually much more expensive than the components bought separately. ​ ​Sometimes manufacturers use non-standard panel connectors to keep customers in an expensive "​walled garden",​ referring to normal, non-proprietary panels as [[https://​inergytek.com/​pages/​support|"​off_brand"​]].((COUGH [[https://​amzn.to/​2SpgjbR|inergy]] COUGH)) ​
  
 The terms //solar generator// and //generator alternative//​ are marketing terms with no real meaning: ​ the units do not //​generate//​ power. The terms //solar generator// and //generator alternative//​ are marketing terms with no real meaning: ​ the units do not //​generate//​ power.
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 Specs for these devices are often given in nonstandard or even misleading ways.  The following discussion will use the Yeti shown above, although their product description is better than most.  Specs for these devices are often given in nonstandard or even misleading ways.  The following discussion will use the Yeti shown above, although their product description is better than most. 
 +
 +Ah are often expressed as mAh.  Which is more impressive, 33Ah or 33,​000mAh? ​ They are the same capacity expressed in different ways. 
 +
  
 The 33Ah **capacity** lead-acid battery in the example above is stated as 400Wh. ​ This is technically correct but mixes units in a way that consumers may not understand. ​ Consumers may also not realize that lead-acid chemistries are usually only drawn down to 50% [[electrical:​depth_of_discharge|depth of discharge]],​ giving an actual usable capacity of 16.5Ah. ​ In addition, lead-acid battery [[electrical:​12v:​battery_capacity|capacities]] are measured over 20hrs. ​ With our example this means a **10w** continuous DC load in this case, or 9w from the built-in inverter. ​ Loads greater than those will decrease usable capacity due to the [[https://​www.google.com/​url?​sa=t&​rct=j&​q=&​esrc=s&​source=web&​cd=1&​cad=rja&​uact=8&​ved=2ahUKEwjNo6ayjbXgAhXJwVQKHZ7xAmAQFjAAegQIChAB&​url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FPeukert%2527s_law&​usg=AOvVaw0guPoMgsy0smO6ISiV1t32|peukert effect]]. The 33Ah **capacity** lead-acid battery in the example above is stated as 400Wh. ​ This is technically correct but mixes units in a way that consumers may not understand. ​ Consumers may also not realize that lead-acid chemistries are usually only drawn down to 50% [[electrical:​depth_of_discharge|depth of discharge]],​ giving an actual usable capacity of 16.5Ah. ​ In addition, lead-acid battery [[electrical:​12v:​battery_capacity|capacities]] are measured over 20hrs. ​ With our example this means a **10w** continuous DC load in this case, or 9w from the built-in inverter. ​ Loads greater than those will decrease usable capacity due to the [[https://​www.google.com/​url?​sa=t&​rct=j&​q=&​esrc=s&​source=web&​cd=1&​cad=rja&​uact=8&​ved=2ahUKEwjNo6ayjbXgAhXJwVQKHZ7xAmAQFjAAegQIChAB&​url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FPeukert%2527s_law&​usg=AOvVaw0guPoMgsy0smO6ISiV1t32|peukert effect]].
  
-In units with lithium batteries, the DC output of the device will be somewhere between 9v-12.6v due to the [[electrical:​12v:​deep_cycle_battery#​non-lifepo4_lithium-ion|voltage of li-ion chemistries]].((if LiFePO4 is eventually used in the devices then the voltage will be quite close to lead acid's voltage)) ​ On the upside, they have almost no peukert effect and therefore can support heavier loads (at the expense of running time).+In typical ​units with lithium batteries, the DC output of the device will be somewhere between 9v-12.6v due to the [[electrical:​12v:​deep_cycle_battery#​non-lifepo4_lithium-ion|voltage of li-ion chemistries]] ​and their [[electrical:​12v:​parallel_serial|3S]] internal arrangement.((if LiFePO4 is eventually used in the devices then the voltage will be quite close to lead acid's voltage))  ​Nefarious marketers sometimes multiply each cell's Ah rating times the number of cells, resulting in a 3x inflation of Ah rating. ​ \\ 
 +On the upside, they have almost no peukert effect and therefore can support heavier loads (at the expense of running time).  Also, higher end units run 4S or higher voltages then downconvert them for a ~13v output much closer to what nominal 12v devices expect.
  
 You could run run [[electrical:​12v:​loads|a load]] at the **inverter'​s 300W normal rating** for ~36 minutes.((including 10% efficiency loss on inversion, but not including peukert effect)) ​ Some manufacturers will list the inverter'​s peak output (600w in this case) in the title as if it were the amount of power the unit could deliver over time.  New folk sometimes read this as "I can run 600w of appliances off the unit forever!",​ forgetting this is a //peak// load and that the unit has a finite capacity. You could run run [[electrical:​12v:​loads|a load]] at the **inverter'​s 300W normal rating** for ~36 minutes.((including 10% efficiency loss on inversion, but not including peukert effect)) ​ Some manufacturers will list the inverter'​s peak output (600w in this case) in the title as if it were the amount of power the unit could deliver over time.  New folk sometimes read this as "I can run 600w of appliances off the unit forever!",​ forgetting this is a //peak// load and that the unit has a finite capacity.
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   * Will you have 8hrs of usable solar harvest? ​ Do check the [[electrical:​12v:​electrical_notation|Vmax and Imax specs]] for the device if you intend to charge with solar; ​ the max input voltage is usually quite low.  ​   * Will you have 8hrs of usable solar harvest? ​ Do check the [[electrical:​12v:​electrical_notation|Vmax and Imax specs]] for the device if you intend to charge with solar; ​ the max input voltage is usually quite low.  ​
  
- +====Charging from solar panels==== 
 + 
 +Charging these devices from solar panels will probably be [[electrical:​solar:​output|slower than you might expect]]: 
 + 
 +  * in the absence of an [[electrical:​solar:​charge_controller#​mppt|mppt controller]]((sometimes present on higher-end devices)) [[electrical:​solar:​output#​charge_controller_type|panel output will be hamstrung by battery voltage]]. ​ You may see a device listing 60w max input but specifying a 100w panel for use with it, and now you know why.  
 +  * devices with 3S lithium cells will hamstring the panels even worse((3S Li voltage can be as low as 9v, and maxxes around 12.5v.)) 
 +  * long wire runs (as seen with portable panels set outside) result in voltage drops 
 +  * sunlight is limited to a certain number of hours. ​ Some units require more hours of charging than there are hours of sunlight in a day.  
 + 
 +Poly panels will typically [[http://​bdp.mousetrap.net/​index.php/​2019/​11/​13/​pwm-loves-poly/​|make slightly more power]] on normal (non-MPPT) devices due to poly's lower voltage / higher current. ​ Devices with internal MPPT controllers will use both panels equally well because they decouple battery and panel voltages.  
 + 
 +Note:  it is possible to [[https://​www.youtube.com/​watch?​v=yXNW-4fNZVk|place a small DC-DC converter between the panel and input port]] to get the panel up near max power. ​ Doing so will make it even more important to manually disconnect the panel when charging is complete. 
 + 
 +Units that do not mention solar charging in their specs can likely still take solar charging through the DC charging port.  Since there may be no controller, **manually disconnect the panel when battery voltage creeps up too high**. ​ For lead this would be ~15v, and for lithium ~12.3v((assuming 3S)).  Another rule of thumb is that the cutoff voltage should be no higher than the voltage on the stock DC charger -- read its label. ​  
 +Be //certain// not to exceed the maximum input charging voltage.((typically 20-25v for built-in MPPT controllers. ​ Standalone controllers typically can handle much higher input voltages -- check the specs.)) 
 + 
 +Another approach might be to place a [[electrical:​solar:​shunt_tweaking|shunt charge controller]] between the panel and DC input and limit the voltage automatically that way. This will not work if the DC port does not "​show"​ the controller the battery voltage. 
 + 
 + 
 +====Charging from wall socket==== 
 +Wall charging is typically fastest because the manufacturer gets total control over the adapter'​s voltage and current output. ​ Note that they might not include a fast charger to reduce cost or heat stress on the battery.((particularly for Li)) 
 + 
 +====Charging from car outlet====  
 +Car charging is typically slow because [[electrical:​12v:​alternator|alternator]] voltage tends to be fairly low((particularly for charging lead)) and [[electrical:​12v:​ports#​the_cigarette_outlet|ciggy outlet]] current limited to 10A.  Unless one is on a road trip there is probably not enough time spent driving the vehicle to charge the device fully.  
 + 
 + 
 +==== internal AGM batteries ==== 
 + 
 +Some units use AGM batteries. ​ This will greatly reduce cost and provide more normal voltage((compared to 3[[electrical:​12v:​parallel_serial| ]] lithium)) ​ but requires ​ [[electrical:​12v:​charging|diligent charging]] or the batteries will [[electrical:​batterycide|fail prematurely]]. ​ All lead-chemistry batteries need to be **fully charged** then **kept charged** as much as possible. 
 + 
 + 
  
  
lifestyle/faq_solar_generator.1573924610.txt.gz · Last modified: 2019/11/16 09:16 by frater_secessus