Words of wisdom: “These aren't aimed at people that know what they are doing.” – LastTreeStar
TL;DR - These things are EXTREMELY expensive for the capacity, however they do offer a lot of convenience. For those with plenty of money who value ease and speed over capacity and run-time, an argument can be made for these if your power needs are small-to-medium and you are only taking short trips in your vehicle.
“Solar Generators” (power stations, power packs) are not actually generators. They are basically just a self-contained electrical system in a box, containing:
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 "off_brand".1)
Less expensive “solar generators” may cut corners by using more basic batteries (AGM vs Lithium), cheaper inverters (Modified sine wave instead of pure sine wave), or less efficient solar charge controllers (PWM instead of MPPT).
The overall proposition can be summed up by the title of a Bob Wells video, Should you Buy a Jackery Power Station? Super Easy but Super Expensive.
The terms solar generator and generator alternative are marketing terms with no real meaning: the units do not generate power.
Sometimes the term jump pack is used for portable battery packs in general, but it often means packs intended to jump start a vehicle. Battery pack usually means small, pocketable “bricks” for charging phones and other small devices.
The best use of these “generators” is someone who:
A solar generator may also be useful for people who want to move the battery between different vehicles.
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.2) 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% depth of discharge, giving an actual usable capacity of 16.5Ah. In addition, lead-acid battery 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 peukert effect.
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 a load at the inverter's 300W normal rating for ~36 minutes.3) 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.
LiFePO4 are typically 3.2v cells arranged four in a row (4S) for nominal 12.8v and actually ~12.1v - 14.0v. LiFePO4 are ~2000-3000 cycles to 20% SoC.
SLA (lead) batteries aren't used much anymore, but if present they are nominal 12v and actually ~12.1-14.6v. SLA as found n SGs are capable of ~500 cycles to 50% SoC.
The inverter will usually be pure sine wave, but lower-priced units that do not specify may be modified sine wave. See the linked article for information about MSW and electronics.
Inverters are typically rated on their continuous output but unscrupulous marketers may list the peak load, which is a temporary overload.
Many smaller units have quite restrictive solar input limits.
Pass-through charging is an important feature, as it allows you to run DC/USB/AC while charging the unit8) While passing-through keep an eye on the unit's temperature and discontinue one or the other if it gets too warm.
A unit with pass-through would maximize charging while driving. The SG and attached devices would charge.
12v ciggy port -> SG -> other devices
A unit without pass-through could only charge the SG because the power cannot be “passed through” the SG.
12v ciggy port -> SG
The situation with solar would be even worse, because it might take all day to charge from solar and the SG could not power other devices for that day.
Since many of the devices don't run at 12v-friendly voltages some of the nicer ones have voltage regulation. This means the output would be a steady 12.8v or 13.4v9) no matter the voltage level of the internal battery pack.
Unregulated 3S packs can drop to 9v, causing some devices to misbehave.
Using the Yeti above as our example again, the charging requirements are:
5 hours from a wall outlet with the included AC charger; in 13 hours with the available car charger*; or as fast as 8 hours from Goal Zero’s monocrystalline solar panels*
Things to consider:
Charging these devices from solar panels will probably be slower than you might expect:
Poly panels will typically 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.
Some of the newer Goal Zeros have MPPT chargers built into them, which does increase their usability. To older models, it can sometimes be added.
Goal Zero makes an optional MPPT controller that installs seamlessly into selected models. Will Prowse damns it with faint praise, noting the 22v solar input voltage limit and relatively modest yield improvements:
It does work better than the PWM on the goal zero… it's worth the money but not as good as a DIY system13) (see below)
Although the DIY mppt setup makes somewhat more than the Optimimizer, the sleek install of the GZ Optimizer may result in a better appearance and portability. The GZ display will not show the charge rate from external controllers.
It may be possible to run the output of a standalone MPPT controller into a charging port of the device. Remember to configure the controller to put a max voltage in line with what the AC charging adapter puts out.
See this video by Will Prowse.
It is possible to 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 ~12.3v14). 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.15)
Another approach might be to place a 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.
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.16)
Car charging is typically slow because alternator voltage tends to be fairly low17) and 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.
It's not *efficient* in the normal sense, but if ciggy charging is running <100w it might make sense to charge the device with the AC adapter running on an inverter rather than from the car charging adapter.
12v ciggy port → small inverter → AC adapter → device
If >120w charging is required while mobile, one solution might be to install an isolator as one would when charging an auxilliary battery. The isolator will pass heavier current into the cabin of the vehicle:
As with the ciggy lighter setup above, it's not particularly efficient but while driving the alternator has power to waste.
Some units use AGM batteries. This will greatly reduce cost and provide more normal voltage19) but requires diligent charging or the batteries will fail prematurely. All lead-chemistry batteries need to be fully charged then kept charged as much as possible.
The most common “premium” brands are Jackery and Goal Zero (Yeti). Bluetti is also gaining traction with a loyal following, and there are less-famous brands like Rockpals, ExpertPower, Aimtom, Nexpow, etc.20) They tend to be named after the watt-hours21) of battery capacity22), or sometimes by the inverter output rating.
The manufacturers often sell proprietary panels (Jackery Solar Saga, etc) which are needlessly expensive. Do the homework and find out which normal panels can work with your device;23) most will require an adapter. Will Prowse recommends devices with MPPT controllers.
Notes: inverter ratings below are the continuous rating, not peak/startup rating. Lithium packs are typically duty-cycle rated to 80% of capacity. Inverter runtime estimates are 100% of continuous rating at 80% DoD and 10% inversion losses.24) Inverters described below are pure sine wave (PSW) unless described as electrical:inverter#modified_sine_wave (MSW).
Bluetti provides more information than usual about their specs, outlets, etc. [bravo! – secessus]
Note: check polarity on models with 30A outlet before use; there are reports the outlet may be wired incorrectly.
Some Ecoflow models have an inverter function they call “X-boost” that appears to drop voltage in order to increase current for heavy loads:
The X-Boost mode is not applicable for all electrical devices. Some devices with a rated power of 600W-1200W that have strict voltage requirements are still not compatible. Please conduct a full test to confirm before usage, so it will not to affect your work. It is recommended to use electrical equipment with heating elements and with a rated power between 600-1200W, such as hair dryers, electric kettles, coffee
Note that the loads mentioned in X-Boost docs are resistance loads (heating coils).
People who want portability or an all-in-one solution can build their own solar generator out of a trolling battery box or milk crate.
In this approach the battery, inverter, solar charge controller, and DC power ports are installed in or on the carrier.