Powerbanks and Solar Panels

AmadeusChapter · May 10, 2021

Hello friends,

I want to get a AA/AAA charger that accepts 1.2V Eneloops and also functions as a powerbank. Right now, I'm looking at the XTAR BC4. I also want to get a small solar panel (likely a GoalZero Nomad 5 or 10) to keep the cells topped up when AC power isn't available. The Nomad 5 has an output current (according to GZ) of 830mA, and the Nomad 10 has an output current of 1500mA. The XTAR BC4 has an input current of 2000mA (4 bays of 500mA). You'll forgive such a basic question, but if I attempt to charge four cells in the XTAR BC4, they will charge, right? Just slower than they would off of 2000mA? Thanks!

Lynx_Arc · May 10, 2021

IMO if you are wanting a good power bank skip the eneloop idea and get one that uses lithium ion instead you can often find one for even cheaper than 4 eneloops and it will have more power to it than them.
As for the solar charging bit remember that a charger isn't 100% efficient there will be losses involved. You can figure watts in based upon 5V at current and watts to batteries based upon 1.5vx4 to and I would toss a 20% loss in the mix. I would suggest you not charge the Eneloops at 2A instead opt for about 1A. So 6V*1A is 6 watts that would equate to 5V at 1.2A (also 6 watts) and with 20% loss your 1500ma current may suffice, assuming that you have enough sunlight. It is possible you may have to drop down lower because often there are clouds or you are using it not when the sun is high above etc.
Again you have to remember USB voltage is higher than voltage needed to charge nimh by a factor of more than 3 times.
The biggest problem with solar charging is when the sun is interrupted the charger may turn off and when it comes back on it will be at the default rate and in some cases you may need to unplug the charger and replug it. Some people doing what you are doing use a power bank to charge the eneloops so they will stay on the correct current and complete charging and then us the solar cell to recharge the power bank itself.

AmadeusChapter · May 12, 2021

Excellent advice, thanks!

Hooked on Fenix · May 12, 2021

The Goal Zero panels are set up well for the Guide 10 Plus charger and power bank. Unfortunately, it charges USB at only 500 mAh. Forget eneloops and get yourself an Xtar PB2S Portable Power Bank Charger. Get a couple 5 amp unprotected 21700 cells to run it and you have a 10 amp powerbank that can charge and discharge larger lithium ion cells up to 2 amps. The charger is as cheap as $17. You can get the batteries for about $6 each. The charger will let you charge your 18650 (protected or unprotected) and 21700 cells (unprotected) for your lights.

Dave_H · May 12, 2021

I've used a "12v" solar panel to charge both Li-ion battery packs, and raw 18650 cells.

For the battery pack (up to 6Ah so far) I use a lighter-plug USB charger rated 12v/24v at 1A or 2.1A. I am not sure it is always charging at this rate, especially with lower sunlight, but works OK, if you're not in a hurry. The overall efficiency is not super, but not bad.

For the 18650's I use a 12vdc 2-bay charger. Only caution here is the panel can supply up to 18v or more under light load, so the 12v charger needs to tolerate this; or run it through a solar charge controller which should limit to around 14v.

Dave

AmadeusChapter · May 15, 2021

I guess the natural follow-up question is to ask if the current on the charger impacts the speed at which the cells charge, or if they impact whether or not they charge at all.

ChrisGarrett · May 16, 2021

AmadeusChapter said:
I guess the natural follow-up question is to ask if the current on the charger impacts the speed at which the cells charge, or if they impact whether or not they charge at all.

With small 5v solar panels, you want the highest current output you can afford, whether to power a charger proper, or when charging a power bank.

It's no fun babysitting a panel/mother battery, charger, power bank while in the sun.

In this application, bigger is better/faster.

Chris

Lynx_Arc · May 16, 2021

ChrisGarrett said:
With small 5v solar panels, you want the highest current output you can afford, whether to power a charger proper, or when charging a power bank.

It's no fun babysitting a panel/mother battery, charger, power bank while in the sun.

In this application, bigger is better/faster.

Chris

Amen to this. Being shackled for a day to get your batteries recharged for the night basically would not be a good thing as often when you need solar power you can't stick around the same place for days on end you often have a few hours then you need to move. If I were into solar charging I would want a panel that could easily supply a days worth of power in about 4 hours or less of peak sun output. this would have you charging things rather quickly perhaps every hour you could complete charging something or 2 hours several items and could move on and setup elsewhere again to charge more. A higher output panel could allow for mobile charging perhaps as I've heard of people mounting panels on backpacks while moving and although sometimes the charge rate is less if you can travel for 5-6 hours and get 1-2 hours worth of charging done while doing so then you may be able to complete your charging in the few hours left in the day either early in the morning or later in the late afternoon.
I wonder if two panels would be better than 1 panel for charging as you could have 2 setups for different needs, one to charge large batteries slowly the other to charge smaller batteries quickly. You could set them up in different spots one closer to a work area that needs more attending than the other panel which could be left charging for a few hours or so.

ChrisGarrett · May 17, 2021

Lynx_Arc said:
Amen to this. Being shackled for a day to get your batteries recharged for the night basically would not be a good thing as often when you need solar power you can't stick around the same place for days on end you often have a few hours then you need to move. If I were into solar charging I would want a panel that could easily supply a days worth of power in about 4 hours or less of peak sun output. this would have you charging things rather quickly perhaps every hour you could complete charging something or 2 hours several items and could move on and setup elsewhere again to charge more. A higher output panel could allow for mobile charging perhaps as I've heard of people mounting panels on backpacks while moving and although sometimes the charge rate is less if you can travel for 5-6 hours and get 1-2 hours worth of charging done while doing so then you may be able to complete your charging in the few hours left in the day either early in the morning or later in the late afternoon.
I wonder if two panels would be better than 1 panel for charging as you could have 2 setups for different needs, one to charge large batteries slowly the other to charge smaller batteries quickly. You could set them up in different spots one closer to a work area that needs more attending than the other panel which could be left charging for a few hours or so.

I'm in a condo on the third of three floors and while I have an elevator, I rarely use it.

For hurricane season, I have two 30w 12vdc mono panels hinged together, a Morningstar SS-10-L PWM controller, a 4 pistol case with cables, adapters and a 12Ah SLA/AGM mother battery. Additionally, I have two Chrome 22Ah mother batteries that I charge up when power is out.

I can then run my chargers and 12vdc fans off of those and have my power banks for the phone.

Panels are about 11# together and the Chromes are another 11# each.

I can manage them easily enough going up/down the stairs.

Chris

Lynx_Arc · May 17, 2021

ChrisGarrett said:
I'm in a condo on the third of three floors and while I have an elevator, I rarely use it.

For hurricane season, I have two 30w 12vdc mono panels hinged together, a Morningstar SS-10-L PWM controller, a 4 pistol case with cables, adapters and a 12Ah SLA/AGM mother battery. Additionally, I have two Chrome 22Ah mother batteries that I charge up when power is out.

I can then run my chargers and 12vdc fans off of those and have my power banks for the phone.

Panels are about 11# together and the Chromes are another 11# each.

I can manage them easily enough going up/down the stairs.

Chris

Sounds good. The only solar panel I've used it a broken one on a helmet mom bought me for a present long ago. The panel needs to be replaced the fan has a 2AA cell power or solar cell. I've used it to play golf once in the summer and it has sit there because I was broke and couldn't afford $8 for a solar cell for it long ago. I bet solar cells are a lot better now and maybe I could redo the cap to use an 18650 instead of 2AAs that would allow longer runtime with less fading in speed. I think I have headroom for a linear regulator from 4v to about 2.8v I figure.

Powerbanks and Solar Panels

AmadeusChapter

Newly Enlightened

Lynx_Arc

Flashaholic

AmadeusChapter

Newly Enlightened

Hooked on Fenix

Flashlight Enthusiast

Dave_H

Flashlight Enthusiast

AmadeusChapter

Newly Enlightened

ChrisGarrett

Flashlight Enthusiast

Lynx_Arc

Flashaholic

ChrisGarrett

Flashlight Enthusiast

Lynx_Arc

Flashaholic

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