Solar generators

Words of wisdom: “These aren't aimed at people that know what they are doing.” – LastTreeStar

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:

• A battery, usually lithium
• USB outlet[s] and 12v outlet[s]
• An inverter
• A solar charge controller

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). These lower-end models tend to have very restricting charging limits not found on DIY systems.

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:

• Has little technical knowledge of electricity and battery chemistries, and no interest in obtaining any
• Is short on time and needs a solution very quickly
• Has plenty of disposable income
• Camps on relatively short outings
• Has small to medium power needs, or does not need long run time.
• Can charge from shore power when away from the camper
• May need to bring their power source well outside of their vehicle for recreational or work reasons

A solar generator may also be useful for people who want to move the battery between different vehicles.

see this article

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.

We are most interested in

• how much capacity the bank has (typically in Watt-hours, Wh)
• charging limits
  • by car adapter (typically ≤120w because of limitations of the ciggy port)
  • by wall adapter (volts and amps, sometimes the stock wall charger makes lower power than is otherwise possible)
  • by solar (Voc and input current, which will dictate which panels and how many are suitable)
• DC output (typically 10A at 12v)
• AC output (given as Watts, the biggest AC loads you can run)

Capacity is most often listed in Wh (watt-hours), which makes comparison quite easy. Some (especially lead cells) retain Ah ratings. For lead batts, 12v x the Ah rating = Wh. Sometimes Ah are expressed as mAh, or 1/000th of an Amp. Which is more impressive, 33Ah or 33,000mAh? They are the same capacity expressed in different ways.

Nefarious marketers sometimes multiply each cell's Ah rating times the number of cells, resulting in a 3x inflation of Ah rating.

Most people know that only about 50% of lead batt capacity should be used in order to ensure a long life. Lithium also has a recommended safety margin, 20%. This means 80% of the rated capacity can be used and still hit the manufacturer's cycle life claims. 400Wh x 0.8 = 320Wh usable.

With 320Wh usable we could run the a theoretical 400w inverter at max load for 48minutes. (320Wh / 400W x 60 minutes)

The cell chemistry is likely 3.6v Li-NMC²⁾ unless LiFePO4 is stated. The chemistry has significant impact on both battery cycle life and solar charging behavior.³⁾

Li-NMC are typically 3.6v cells arranged three in a row (3S) for nominal 10.8v. Actual voltage will vary from 9v-12.6v.⁴⁾ Li-NMC are rated ~500 cycles to 20% state of charge.

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.

If the controller type isn't claimed to be MPPT it is likely PWM.

also see this article on choosing panels for a SG

Many smaller units have quite restrictive solar input limits.

• voltage - 24Voc is a common voltage limit, effectively limiting one to 12v nominal panels. Input voltage limits must not be exceeded. Note: some very large units have high input minimums, like 50v.
• current limit - 3A is a common input current limit on smaller, less-expensive units. 8A is a common limit on larger units.
  • With PWM controllers the max power harvestable will be 3A x [internal battery voltage], which can be as low as 9v. 9v x 3A 27w. PWM input current limits must not be exceeded
  • MPPT controllers with the same limit might run the panels at 18v, the Vmp: 18v x 3A = 54w⁵⁾ MPPT incoming current limits can usually be exceeded; the controller will throttle back incoming current to hold the limit. The allowable amount of overpanel is well-documented with most standalone MPPT controllers but “power stations” are usually black boxes with no published overpanel spec. Proceed at your own peril.

Because the Amp limit is usually the limiting factor for MPPT power production. Selecting a panel with a Voc⁶⁾ closer to the unit's input limit⁷⁾ can make maximal power given the limitations. This is because for a given rated output like 100w a higher Vmp (volts) means a lower Imp (amps).

• 22.5Voc panel - Vmp ~18v.⁸⁾ 18v x 8A limit = 144w.
• 21Voc panel - Vmp ~16.8v. 16.8v x 8A limit = 134w.

Pass-through charging is an important feature, as it allows you to run DC/USB/AC while charging the unit⁹⁾ 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 13.4v¹⁰⁾ 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:

• will you be near shore power for 5 hours to charge from 110vac?
• It takes 13hrs to charge from a running vehicle because alternator voltage output is relatively low.
• Will you have 8hrs of usable solar harvest? Do check the Vmax and Imax specs for the device if you intend to charge with solar; the max input voltage is usually quite low.

Charging these devices from solar panels will probably be slower than you might expect:

• in the absence of an mppt controller¹¹⁾ 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 worse¹²⁾
• 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.
• it is common for smaller units to have low input voltage limits, like 25v or lower. This restricts the panels you can use for charging.
• it is common for smaller units to have low input current limits for DC charging (Wall adapter, car adapter, or panel). This is particularly restrictive on panel input. Consider these examples using a 3A input limit and 100w panel with 18Vmp.
  • 100w panel on MPPT controller - 18v x 3A = 54W¹³⁾
  • 100w panel on PWM controller - With typical 3S Li-Po batteries input would typically be limited to something like 36w (12v x 3A). Less-common internal AGM batteries would make a bit more since voltage is higher, ~39W (13v x 3A).

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 system¹⁴⁾ (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 ~12.3v¹⁵⁾. 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.¹⁶⁾

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.¹⁷⁾

Car charging is typically slow because alternator voltage tends to be fairly low¹⁸⁾ 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

Example: the Bluetti AC50S charges about 2x as fast from the inverter than from the car adapter, due to the AC adapter's higher 27.5v output.¹⁹⁾

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:

alternator --> isolator –> inverter –> SG's high power wall adapter

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 voltage²⁰⁾ 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.

[note: see this reddit post comparing larger units by Wh/$, etc. ]

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.²¹⁾ They tend to be named after the watt-hours²²⁾ of battery capacity²³⁾, 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;²⁴⁾ 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.²⁵⁾ Inverters described below are pure sine wave (PSW) unless described as electrical:inverter#modified_sine_wave (MSW).

• Explorer 160 - 167Wh. 100w MSW inverter (~72 minutes practical runtime²⁶⁾ at full inverter load). 1x AC outlet. 2x USB. 1x USB-C outlet.²⁷⁾ 6mm DC output jack.²⁸⁾. PWM controller. 14.4v internal.
• Explorer 240 - 240Wh. 200w inverter (~52 minutes). 1x AC outlet. 2x USB. Ciggy port. Some specs mention MPPT controller.²⁹⁾
• Explorer 300 - 293Wh. 300w inverter (~42 minutes). 2x AC outlet. 2x USB. 1x USB-C³⁰⁾. Covered ciggy port. Used by caratank³¹⁾.
• Explorer 440 - cannot use Solar Saga panels
• Explorer 500 - 518Wh. 500w inverter (~45 minutes). 3x USB. 2x DC. ciggy port. Original version has a PWM controller; version 2 has MPPT.³²⁾
• Explorer 1000 - 1002Wh @ 21.6v(regulated). 1000w inverter (~43 minutes). 3x AC outlet. 2x USB. 1x USB-C³³⁾. Covered ciggy port. DC jack and Anderson³⁴⁾ inputs. MPPT controller. 1000 charge cycles to 80% DoD.

• Yeti 200x - 187Wh @ 14.4v (regulated). 120w inverter (~67 minutes). 1x AC outlet. Ciggy outlet. DC jack outlet. 2x USB. 2x USB-C. MPPT controller. 500 cycles.
• Yeti 400 - 428Wh @ 10.8v (regulated to 12v). 300w inverter (~62 minutes). 2x AC outlets. Ciggy outlet. 1x DC outlet port. 3x USB.
• Yeti 500x - 505Wh @ 10.8v (regulated). 2x AC outlets. Ciggy outlet. 1x DC jack outlet. 2x USB. 2x USB-C³⁵⁾. 500 cycles.
• Yeti 1500x - 1516Wh @ 10.8v (regulated). 2000w inverter (~33 minutes). 2x AC outlets. Ciggy outlet. 2x DC jack outlets. 1x DC Anderson outlet. 2x USB. 2x USB-C. 500 cycles. DC input jack and DC input Anderson jack.
• Yeti 3000x - 2982Wh @ 10.8v (regulated). 2000w inverter (~64 minutes). 2x AC outlets. Ciggy outlet. 2x DC jack outlets. 1x DC Anderson outlet. 2x USB. 2x USB-C. DC input jack and DC input Anderson jack. 500 cycles.

Bluetti provides more information than usual about their specs, outlets, etc. [bravo! – secessus]

• Maxoak AC20 - 200Wh. 120w inverter (~72 minutes). 1x AC outlet. 1x DC jack outlet. 2x USB. 1000 cycles. MPPT controller.³⁶⁾
• Maxoak AC100 - 1000Wh @ 14.8v (regulated to 13.4v). 600w inverter (~72 minutes). 2x AC outlets. Ciggy outlet.³⁷⁾ 4x usb. 1x USB-C. “Up to” 2500 cycles. MPPT controller.³⁸⁾
• AC200P - 2000Wh LiFePO4 @14.8v. 2000w inverter (~43 minutes). 6x AC outlets. Ciggy outlet. 3x DC jack outlets. 2x USB. 1x USB-C. MPPT controller.³⁹⁾
• AC200 Max.

Note: check polarity on models with 30A outlet before use; there are reports the outlet may be wired incorrectly.

Note: check

• Ecoflow River Pro - 720Wh. 600w inverter (~52 minutes). 3x AC outlets. Ciggy outlet. 2x DC jack outlets. 3x USB. 1x USB-C. Specs do not list MPPT, but website does.⁴⁰⁾

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).

Heads up: there are at least two issues that may affect the Delta Pro: "explosive" failure and reverse polarity.

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.

• Will Prowse "milk crate" how-tos (YT)

The Jackery Explorer 1000 flashlight appears to activate one of the USB ports even when the USB panel is switched off.

The Jackery Explorer 500 solar charge controller is PWM⁴¹⁾ while the 500 version 2 appears to be MPPT and capable of handling up to 30v.⁴²⁾

Some units are tightly focused on inverter (AC) output, and don't have big DC outlets. The Bluetti EB150, for example, maxes out at 9A DC and that is through the ciggy outlet.