Best solar battery charger

Ok, forgive me if there's something relative to this request, but I couldn't find anything recent that would be relevant to my question. I'm looking for a solar battery charger with the following qualifications:

1. Can charge up to 4 batteries at once. (bonus extra, can charge any combination from 1-4 batteries, or in pairs of 2. Either works)
2. Easily portable.
3. Can charge all standard sizes (AAA, AA, C, D, 9v)
4. Gets a good, solid charge of 95% or better when charge is completed. (most solars I've looked at don't do much better than 80% before topping out. T_T)
5. Is able to complete the charge on all 4 batteries within 2 hours or less. 1 hour preferably.
6. Reasonable price. (ie, $60 or less if possible)

So, anyone know of an existing charger that'll do this, or will I have to create a frankenstein build it yourself version?

lordraiden said:

Ok, forgive me if there's something relative to this request, but I couldn't find anything recent that would be relevant to my question. I'm looking for a solar battery charger with the following qualifications:

1. Can charge up to 4 batteries at once. (bonus extra, can charge any combination from 1-4 batteries, or in pairs of 2. Either works)
2. Easily portable.
3. Can charge all standard sizes (AAA, AA, C, D, 9v)
4. Gets a good, solid charge of 95% or better when charge is completed. (most solars I've looked at don't do much better than 80% before topping out. T_T)
5. Is able to complete the charge on all 4 batteries within 2 hours or less. 1 hour preferably.
6. Reasonable price. (ie, $60 or less if possible)

So, anyone know of an existing charger that'll do this, or will I have to create a frankenstein build it yourself version?

Click to expand...

There is no such thing out on the marketplace that I know of. And if you are going to do it yourself you are probably going to have to expand your budget considerably. Just as a starting point you are going to have to charge each AA with a 1A current to be in the ballpark of what you are looking to do.

lordraiden said:

....... So, anyone know of an existing charger that'll do this, or will I have to create a frankenstein build it yourself version?

Click to expand...

Ummm, I don't think you will have any luck finding an off the shelf charger that does all you want. The 1.5v and the lithium ion chargers work differently. So that would entail 2 different charger topologies. Also most chargers want a stable power source such as from a power supply, 12v battery, 5v USB, or 120Vac.

The voltage from solar panels can vary all over the place. And this sort of changes the approach to designing a charger with the ability to pick up and restart when the power is disrupted and then comes back. I personally have been thinking about the do-it-yourself version. I'm seeing more and more requests on CPF for just a solar power source charger. It can be done. It's just that the market for them is not as big.

Some of the criteria that needs to be taken into account is the wide range of input voltage. There needs to be some front end electronics that adjusts the voltage to the value the charging circuits will use. There probably needs to be some built in start and stop thresholds. Then past that you have your regular charging circuits. So it looks like a slightly higher cost than just building a charger that operates off a stable fixed voltage. Thus in this world where everything is made to be as inexpensive as possible, it seems as most manufacturers aren't chasing a market that might be kind of thin.

Well, how about htis hiuintahs. I was working on a solution not long back (never got far with it though due to lack of cash) that involved a very simple approach to solving the solar charging problem you detail. Namely the variability of the input from solar cells. Originally it was meant to solve a problem involving all the energy wasted or lost when solar input was greater than need, storing up the excess energy until a period later on (up to half an hour) when input dropped and more energy was needed to continue the charging than was being supplied. That solution is capacitors. Let me explain.

Over the years I've run into several off the shelf solar powered items (not chargers, just devices) that use a capacitor to help buffer the input from the solar panel to whatever the device is. To make this happen they also employ a small battery as the secondary power buffer. So when it's all done you end up with something like this: Solar Panel -> flow controller w/capacitor -> battery -> device. The batteries that acted as the secondary buffer weren't that big in overall capacity, but they did a bangup job of holding a charge so that the device could continue to work for several minutes without any solar input. They also took the extra power coming in that the capacity couldn't hold during periods when there was even too much power for the capacitor to absorb. However, some designs employed a capacitor alone as the input buffer.

I think solar calculators use the same idea, because if you take and cover up the solar panel they keep working and don't fade away for at least a good minute or so. So if you wanted to create an input buffer like you're talking, you'd probably need to do something like that. Now as for the battery charger itself, I'm not opposed to building my own. I just figured that if there was already a commercial solution, why bother with all the hassle of doing it myself. But as you guys have said, they don't exist, then we need to do one of two things:

A) change the speed at which the batteries charge, or B) go DIY for our solution. TBH I'd *LIKE* a 1-2 hour charge, but if it's not possible without a huge cash outlay, then I'm fine with a greater time frame for charging. I'd prefer faster, as it'd solve a few problems. But I'm flexible. I kinda figured I'd have to back down a little on my criteria, so I listed it a bit high in case I got lucky and did get what I first asked for.

interesting concepts in simplicity. completly reverse everything we think about nickle based charging and instead think of only the chemical reactions that the battery would desire most. Higher current when the most stuff can change state, and lower current when most items in the cell have changed state.
AKA slowing down , as the cell would really desire, instead of alogrythms back from 1960s

The method of charge we are ingrained as being the only possible and "proper" method for charge and termination, is not the only method at all. Single Solar cell items of the usual monocrystaline variety are ~.5v each, toss 3 together and you got 1.5v , gee what else is about 1.5V ??? (ohh hurt my head thinking
What happens when the voltage differential from 2 power sources is higher ? a larger current flow. and what happens when the voltage differential between 2 power sources is lower, a lower current flow.

Naw it cant be THAT simple can it? that when a battery needed the most charge it would get the most current, and when it needed the least charge and charge was completed most it got the least current.
I have applied that method with li-ion charging, plus some fine tuning and a cut-off, could it also work with ni-mh?

If you have 2 buckets of water, one bucket only fills to a specific point then stops, the other bucket is Siphen fed off the other bucket, now the hard part. How high will the second bucket Ever get at any time? Well most brilliant scientist knew the answer to that question back in the pioneer days of yore. its like 2013 and now it takes a computer to fill the bucket, without it nobody know what to do

lordraiden said:

Ok, forgive me if there's something relative to this request, but I couldn't find anything recent that would be relevant to my question. I'm looking for a solar battery charger with the following qualifications:

1. Can charge up to 4 batteries at once. (bonus extra, can charge any combination from 1-4 batteries, or in pairs of 2. Either works)
2. Easily portable.
3. Can charge all standard sizes (AAA, AA, C, D, 9v)
4. Gets a good, solid charge of 95% or better when charge is completed. (most solars I've looked at don't do much better than 80% before topping out. T_T)
5. Is able to complete the charge on all 4 batteries within 2 hours or less. 1 hour preferably.
6. Reasonable price. (ie, $60 or less if possible)

So, anyone know of an existing charger that'll do this, or will I have to create a frankenstein build it yourself version?

Click to expand...

You won't find anything off the shelf that does that (certainly for that cost) for a number of reasons.

1) You mentioned sizes, but not battery type, so I am going to assume NiMh. NiMh requires a steady charge especially around the termination point otherwise you can't reliably determine the end of charge Lithium batteries are actually easier to charge from solar.

2) The mount of power required: ... let's say you had a 4 - 2500mA AA. That would be about 12 watt hours. Let's say 75% battery efficiency, and 75% solar charging efficiency. So I will need about 20 watts of solar panel to charge those 4AA batteries in 1 hour under very bright direct sun (which often one does not have). Let's say I have D batteries with 3x the capacity, now I am into a 60W panel and my budget is gone.

3) Sun is highly variable and hence odds of the solar panel being at peak are low unless you have perfectly sunny days and can point your panel.


Best thing to do is find a charger you really like that has a 12V (nominal) input and uses switch mode conversion inside so that it is efficient. That alone could run you $60 of course, but there are cheaper models. Then get a solar panel, charge controller, and a small 12V lead acid battery. Use that as the power source. You can scale the solar panel depending on your needs/budget.

Glass solar panels are inexpensive. If you want rollably/foldable, be prepared to pay a whole lot more.

Semiman

For me I've gone the route of having an AGM battery as the medium of storage from the solar panel and for now I just use an off the shelf AA or lithium ion charger that runs from 12v.

I only think the route in which you want to go straight from solar panel to charger is for the portable and smaller solar panels where it's not convenient to tote around a system with an AGM battery such as backpacking, etc.

Thus I would think more along the lines of some type of maximum power point type of charging technology such as is used in charging AGM batteries and used to maximize the power that is coming from a smaller solar system since the voltage is high compared to an AA or lithium ion batter. Basically it would charge at a variable rate depending on the output of the solar panel.

So for the constant current charging, I think what you'd end up with is variable constant current........if that makes sense. Some type of big capacitor as you mention might be the secret to indicate when the charge rate can be increased and decreased....ie: the buffer.

Just thinking out loud.

So, now in 2016, do we have a solar charger for OP?

I'd like a compact panel that I can connect to my Xtar VC4.

trojansteel said:

So, now in 2016, do we have a solar charger for OP?

I'd like a compact panel that I can connect to my Xtar VC4.

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Than you'd need a folding USB panel that can put out a proper 2.1A, which is about what the VC4 needs.

I use a folding Sunkingdom 14w panel, or two separate power banks, with my VC4 and other USB chargers.

Chris

ChrisGarrett said:

...I use a folding Sunkingdom 14w panel, or two separate power banks, with my VC4 and other USB chargers...

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This is a configuration I've been testing lately too and it works well unless the panel is shaded too much and power drops.
However, Chris, mentioned the use of power banks and this is what I've used too to account for any long term cloud cover that might interfere with the VC4's NiMH charge cycle.
I use a Goal Zero Venture 30 powerbank which has a form of USB pass-through ability which basically lets the Venture 30 act as a uninterruptable power supply. My USB solar panel is plugged into the Venture 30 and I plug the VC4 into it as well. The Venture is good at maximizing it's own charging from the solar panel and also at giving the VC4 as much power as it needs to charge at it's max. I watched the Venture complete the charge of it's own battery and continue to pass through the current to continue to charge the cells in the VC4. The Venture 30 was always able to pull more power from the various USB panels I tried than was needed by the VC4 to charger. If I covered the panel from the sun the VC4 continued to charge without a hitch.

The maximum amount of power I've measured the VC4 needing to charge all 4 cells at once was just under 7 watts so it doesn't use as much power as 12v NiMH battery chargers I had tried before. Outside of being a little bulky it appears to be a great solar charging option for NiMH AA/AAA/C/D cells as well as lithium cells.

On a side note, the XTAR VC2 Plus has USB pass-through ability on the port it has built into it. I'm thinking it might work the same as the Venture 30 did but let me charge or use an 18650 cell as the UPS.

I think you guys have it right - VC4 and ~14W (or better) folding USB panel. This comes about as close as you can get to what the OP wants. But it certainly won't fully charge four batteries as quickly as the OP wants - ESPECIALLY if we are talking C and D cells (which can't even charge that quickly from a standard 120VAC charger due to charge rate limits on the batteries themselves). It also won't charge 9V batteries. And it's not one nice, neat unit. But it would certainly get the job done, ESPECIALLY in sunny places (ie California, Nevada, Arizona, Colorado, etc). And it's not too expensive or overly heavy.

I keep a 22Ah Chrome SLA/AGm and a 12Ah PowerSonic handy for mother batteries and trickle charge them up with a Battery Tender Jr. every couple of months, so they're ready to go for hurricane season.


In a power outage, I'll charge them up with my 2x30w 12v rigid mono panels and Morningstar SS10-L controller that's posted in the 'solar charging kit' thread I did.

Add to that, my 14w USB panel and two (4x18650 Ruinovo & 3x18650 Xiaomi Mi) power banks and I'm not going to be hurting even in cloudy weather, at least not for a while.

Honestly, for my condo living, I have a lot of portable power. Keeping the neighbors away is going to be the hard part. 432 units watching the lights blaze away and listening to the music blaring will be a handful. Forget the water filters I have for the lake/canal we live on.

I'm not going to be able to hide from anybody, so OpSec will be practically nil.

Chris

filibuster said:

...On a side note, the XTAR VC2 Plus has USB pass-through ability on the port it has built into it. I'm thinking it might work the same as the Venture 30 did but let me charge or use an 18650 cell as the UPS.

Click to expand...

Just tested the VC2 Plus connected directly to a solar panel with the VC4 plugged into the VC2+'s USB port. I had a singled 18650 cell in the VC2's left bay to act as a power source in case the solar panel dropped power production.

The results weren't good. The VC2 would power the VC4 but it was not very dynamic in it's ability to charge and pass-through the USB power as needed when connected to a solar panel. If the solar panel's power went away the VC2 would shutdown and not automatically start outputting power via the 18650 cell to it's USB port. It would often reset the USB out connection too such as when the cell in the VC2's bay reached full charge and so the VC4 would power cycle often during it's charging process which is what I was trying to avoid.

I tried the Venture 30 again in the same configuration and it worked great as "UPS". It would charge and pass-through power when the solar panel was in the sun and keep the power flowing when the solar power went away.

filibuster said:

Just tested the VC2 Plus connected directly to a solar panel with the VC4 plugged into the VC2+'s USB port ... The results weren't good...

Click to expand...

Most of the pseudo-"UPS" functionality in powerbanks is very poorly implemented - often appearing to be an afterthought (or even an accident). Unfortunately this functionality is rarely tested by reviewers, so the only way to know if it will work in any application is to do your own test. I encourage reviewers to test this, since the info would prove helpful to many readers.

A good implementation includes power path control, with independent power paths for the load and batteries, and intelligent load sharing. This enables much more precise control, e.g. one can slow down charging when the load rises, or when one is close to reaching limits on input power (e.g. USB limits). For example, TI calls this PPM/DPPM = [Dynamic] Power Path Management and has various charger chips that include such (as do other vendors).

Many of the naive designs in cheap powerbanks simply use the CC/CV charger to power both the load and charge the batteries, with no further control or intelligence. This poses many problems, e.g. it imposes load limits based on the battery charging current, it poses problems with proper CC/CV algorithm execution, because the charger doesn't know how much current is going to the cells (some is stolen by the load). For example, the termination current may never be reached since the load may always be higher, precharge may timeout since the cells never reach 3.0V since the low precharge current was mostly stolen by the load (this is partly why cell phones don't allow you to use them when they are precharging after the battery has completely drained).

Some of these chips with power-path management are probably cheap enough nowadays that they might percolate down into powerbanks. But I am not aware of any.