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--- lifestyle:faq_solar_generator [2020/05/20 11:20]
frater_secessus [solar charging]
+++ lifestyle:faq_solar_generator [2020/05/20 11:39]
frater_secessus [Charging from solar panels]
@@ Line 52: / Line 52: @@
   * 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.
-==== technical discussion ====
+====Charging from solar panels====
-**Charging from wall socket** 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 these devices from solar panels will probably be [[electrical:solar:output|slower than you might expect]].
-**Charging from car outlet** 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.
-**Charging from solar panels** is can be problematic because daylight is limited, and because most devices effectively run the straight to the internal battery through the input jack.  This runs the panel way off its rated power point and **greatly reduces the amount of power harvested by the panel**.   You may see a device listing 60w max input but specifying a 100w panel for use with it, and now you know why.  [[electrical:solar:pwm_tweaking|A similar thing happens with PWM controllers]] only it's probably going to be even worse with low- and medium-range devices that have lithium batteries in them.((3S Li voltage can be as low as 9v, and maxxes around 12.5v.))  Devices that claim to have internal solar controllers (probably mppt) will cost more but will make much better use of panels for charging.((4S or greater Li configurations will also charge better from solar due to higher voltage))  Be //certain// not to exceed the maximum input charging voltage.((typically 20-25v for built-in controllers.  Standalone controllers typically can handle much higher input voltages -- check the specs.))
-, resulting in power harvesting
+  * 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 is 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 ====

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