USB powered 4xAA (independent) analyzing charger

I'm looking for a 4xAA/AAA analyzing charger that can be powered via USB (5V). Independent channels are a must and the ability to put >500mA per channel into a battery. I also want a LCD that shows mAh, time, etc.

Does anything like this exist? Something like a LaCrosse BC-700/900 or Opus BT-C700 but able to be powered from USB? Or, do I just make my own power cord with a DC/DC converter in the middle to turn 5V USB into 12V DC and use one of the aforementioned chargers through the 12V input?

Stereodude said:

I'm looking for a 4xAA/AAA analyzing charger that can be powered via USB (5V). Independent channels are a must and the ability to put >500mA per channel into a battery. I also want a LCD that shows mAh, time, etc.

Does anything like this exist? Something like a LaCrosse BC-700/900 or Opus BT-C700 but able to be powered from USB? Or, do I just make my own power cord with a DC/DC converter in the middle to turn 5V USB into 12V DC and use one of the aforementioned chargers through the 12V input?

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I'll assume that you don't have 120vac, nor do you want to use 12vdc from say...an SLA/AGM mother battery, or 12vdc solar panel?

The Xtar VC4 is a 4 bay USB multi-chemistry charger that does NiMH, and the popular 3.7v (4.2v) li-ion chemistries at two rates: 1A x 2 and 500mA x 4. It needs a solid 2.1A wall wart adapter, or USB solar panel output to give you that, so hooking the thing up to your computer with 4 cells in it, isn't going to give you 500mA for each, but it does have a voltage meter and tells you how many mAh it pumps into the batteries/cells, upon charging, so you get a little bit of analyzing, although it's not an analyzing charger by any stretch.

I just brought mine over to my GF's place to run with a Xiaomi Mi powerbank, just in case her power goes out during a hurricane. It's a bit slower than advertised, but it is USB and it does both types of chemistries and it'll work with a powerbank, or USB folding solar panels. I brought back my LaCrosse BC-700, FWIW.

Chris

ChrisGarrett said:

I'll assume that you don't have 120vac, nor do you want to use 12vdc from say...an SLA/AGM mother battery, or 12vdc solar panel?

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The idea was to use a 5V solar panel like this to charge a Li-Ion power bank which could then charge AA batteries or other devices that connect to USB to charge.

The Xtar VC4 is a 4 bay USB multi-chemistry charger that does NiMH, and the popular 3.7v (4.2v) li-ion chemistries at two rates: 1A x 2 and 500mA x 4. It needs a solid 2.1A wall wart adapter, or USB solar panel output to give you that, so hooking the thing up to your computer with 4 cells in it, isn't going to give you 500mA for each, but it does have a voltage meter and tells you how many mAh it pumps into the batteries/cells, upon charging, so you get a little bit of analyzing, although it's not an analyzing charger by any stretch.

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Well, I don't really need an analyzing charger per say. I want to see roughly how much energy is going into the batteries. I do like to fully discharge and recharge my Eneloops with the BC-700 though. I'm not sure of the current draw from 12V with 4 batteries charging at 700mA though. If the charger was reasonably efficient it could easily charge 4AA batteries at 700mA with like 6W of power. I guess I will measure the current draw of my BC-700 and see how much current it when charging.

Stereodude said:

The idea was to use a 5V solar panel like this to charge a Li-Ion power bank which could then charge AA batteries or other devices that connect to USB to charge.


Well, I don't really need an analyzing charger per say. I want to see roughly how much energy is going into the batteries. I do like to fully discharge and recharge my Eneloops with the BC-700 though. I'm not sure of the current draw from 12V with 4 batteries charging at 700mA though. If the charger was reasonably efficient it could easily charge 4AA batteries at 700mA with like 6W of power. I guess I will measure the current draw of my BC-700 and see how much current it when charging.

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I've got a 12vdc 60w (2x30w Monos) solar panel system feeding a Morningstar SS-10-L PWM digital controller and a couple of 22Ah/12Ah SLA/AGM mother batteries, so that's the way I roll in that system. My chargers are/were 12vdc, so I'm good there.

Then last year, after the 5v USB folding solar panels started flooding the market, I got a 14w jobbie, some Xtar USB chargers and some inexpensive power banks, to compliment the heavier system and cover some more bases.

The Anker Power Port 21w folder will be the next one I buy, unless something better comes out. Like 18650 cells, the manufacturers fudge the numbers a bit and if you get half the claimed output, you're lucky. So that 21w might actually be 10w-12w, which isn't a lot when charging up 4xAAs.

This being said, 12vdc rollable/foldable panels are substantially more money, although they might be the way to go for quicker charging.

There are always inefficiencies and people thinking that they're going to charge up 4 Eneloop batteries that are at 20% SOC, in a couple/few solar hours using some 10w solar jobbie are probably smoking some good stuff.

With solar, much like with fish tanks, buy the biggest panel that you can afford.

Using a 12vdc solar panel(s,) a digital controller (20w plus,) a mother battery and 12 volts can work fine, if not a bit on the bulkier/heavier side than a USB system.

Add to all of this, the fact that the BC-700 type chargers tend to trip their temperature safeties and I wouldn't rely on the BC-700 charger to charge up quickly in a SHTF event.

The VC4, your Anker PP 21w and some power banks that you can self replace the cells in and you're set for most small scale scenarios, IMO.

Chris

ChrisGarrett said:

I've got a 12vdc 60w (2x30w Monos) solar panel system feeding a Morningstar SS-10-L PWM digital controller and a couple of 22Ah/12Ah SLA/AGM mother batteries, so that's the way I roll in that system. My chargers are/were 12vdc, so I'm good there.

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I have something more like that in mind for home, but with higher wattage panels. Trying to see about a MPPT instead of a PWM controller, but I don't think the low cost ones actually are true MPPTs. However, here I want something I can stuff in a backpack and leave with if needed.

The Anker Power Port 21w folder will be the next one I buy, unless something better comes out. Like 18650 cells, the manufacturers fudge the numbers a bit and if you get half the claimed output, you're lucky. So that 21w might actually be 10w-12w, which isn't a lot when charging up 4xAAs.

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It uses Sunpower solar cells, so it should be legit, but who knows.

Add to all of this, the fact that the BC-700 type chargers tend to trip their temperature safeties and I wouldn't rely on the BC-700 charger to charge up quickly in a SHTF event.

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I have several BC700's I've never seen any of them misbehave. They charge up my Eneloops in just over 3 hours every time.

FWIW, I have the older 14W version of Anker's panel, and it's pretty decent. I haven't done any exhaustive testing, but in full sunlight it does appear to be good for close to 8-9W or so. Call it in the region of 60% of the advertised capacity, which appears to be the norm. As always, YMMV; we're not exactly short of insolation here most days.

We bought it for the occasional camping trip, and as a means of charging batteries and having light at night if the power goes out. Actually, that's more like when - there have been two instances in the last 10 years where the power went out island-wide, and those were triggered by comparatively minor events; one was caused by a 6.7 earthquake under the Big Island, and the other a lightning strike that caused the entire "grid" (not that the electrical system here deserves such a name) to cascade on itself, effectively failing because it was failing. Every summer we stare down a bunch of hurricanes as they come in from the east, and one of these days one will finally hit (I wasn't around for Iniki, but my wife was, and we actually had one pass far closer than that to the north a couple of weeks ago).

The plan would be similar to yours; if we run out of primaries, we charge a power bank as best as we can during the day, then charge AA's from that as needed. We have some Portapow (IIRC) USB charger that can do 4 AA/AAA's at a time, and while it's not exactly lightning fast, it gets there in the end. Charging from a power bank is probably a better idea than trying to run a charger directly from the panel, as the varying output of a panel might upset the controller in some chargers.

So it turns out the BC-700 takes 3V on the input, not 12V. Further, the wall wart the comes with it is only rated for 2.8A. I'm going to test and see how much current the BC-700 actually draws while charging 4 AA Eneloop batteries, but a decent buck converter should be able to make 3V @ 2.8A from 5V/2A.

Edit: Measured it at 2.8A. The charger is very sensitive to input voltage. If you drop below 3.0V the current going to the battery drops. If you go above 3.0V the current from the power supply goes up rather quickly.

I think you need 2 2 channel USB chargers as I don't think these chargers can take advantage of more than about 2.1A input which is needed to charge 4AA @ 1A off a USB input. One that comes to mind with drawbacks is the XTAR VC2 Plus. The drawback is one reviewer on Amazon noted using a solar cell when it couldn't sustain a 1A charging level it dropped to 0.5A and then wouldn't resume 1A when more solar power returned. This wouldn't be a big problem using a power bank though.

Stereodude said:

So it turns out the BC-700 takes 3V on the input, not 12V. Further, the wall wart the comes with it is only rated for 2.8A. I'm going to test and see how much current the BC-700 actually draws while charging 4 AA Eneloop batteries, but a decent buck converter should be able to make 3V @ 2.8A from 5V/2A.

Edit: Measured it at 2.8A. The charger is very sensitive to input voltage. If you drop below 3.0V the current going to the battery drops. If you go above 3.0V the current from the power supply goes up rather quickly.

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I built that in 2012 and there are 12v>3v cigarette car adapters that you can buy and I did, so I can run the BC-700 in the car, or with my 12v AGM/SLA mother batteries.

Robert Dana is my charger dude on Ebay:

http://www.ebay.com/itm/Car-Adapter...hash=item35bb9aab22:m:mn24CU0lw-KU_C1nSlqTlRQ

Here's my thread on building my 12vdc system and there are some great ideas shared in the various posts, so check them out.

I miss Norm:

http://www.candlepowerforums.com/vb/showthread.php?342073-Portable-solar-charging-setup-I-just-built

Chris

Smegheaaad said:

We bought it for the occasional camping trip, and as a means of charging batteries and having light at night if the power goes out. ...

The plan would be similar to yours; if we run out of primaries, we charge a power bank as best as we can during the day, then charge AA's from that as needed. We have some Portapow (IIRC) USB charger that can do 4 AA/AAA's at a time, and while it's not exactly lightning fast, it gets there in the end. Charging from a power bank is probably a better idea than trying to run a charger directly from the panel, as the varying output of a panel might upset the controller in some chargers.

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So the more I look into this the worse and worse it looks. The Li-Ion power banks are only 80% efficient when charging, they're only about 80% efficient when outputting their power to USB. NiMH chargers are less than 50% efficient. My BC-700 looks to be about 40% efficient at transferring power into AA cells. If we assume 90% converting 5V to to 3V it looks like this.

So 80% * 80% * 90% * 40% = 23% :sigh:

I'd be way better off with a powerbank charger like the Tomo v8, or just a USB powered 18650 charger and giving up on NiMH AAs. There's only one 80% hit vs. 23%.

Stereodude said:

So the more I look into this the worse and worse it looks. The Li-Ion power banks are only 80% efficient when charging, they're only about 80% efficient when outputting their power to USB. NiMH chargers are less than 50% efficient. My BC-700 looks to be about 40% efficient at transferring power into AA cells. If we assume 90% converting 5V to to 3V it looks like this.

So 80% * 80% * 90% * 40% = 23% :sigh:

I'd be way better off with a powerbank charger like the Tomo v8, or just a USB powered 18650 charger and giving up on NiMH AAs. There's only one 80% hit vs. 23%.

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I've got a Tomo V8-4 PB and a genuine Xiaomi Mi 10,000mAh 3x18650 bank, that states 6250mAh tested output, so roughly 62% usable power out of the three quality cells. Charging something else like my LG Revere flip phone, will yield less output capacity, but some power banks, like my Ruinovo 4x18650 have tested charging efficiencies of 90+%, so your 80% numbers above, aren't necessarily as bleak as you might think, but there are no free lunches.

It's all 'robbing Peter, to pay Paul,' so pick your poison.

The 18650 form factor is very energy dense and one moderately sized (3000-3500mAh) 18650 holds about as much energy as 4 quality NiMH AAs, so there's your answer.

Chris

ChrisGarrett said:

I've got a Tomo V8-4 PB and a genuine Xiaomi Mi 10,000mAh 3x18650 bank, that states 6250mAh tested output, so roughly 62% usable power out of the three quality cells.

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I think your math is off. That's 10Ah at ~3.7V, so 37Wh. 6.25Ah at 5V = 31.25Wh. Basically 84.5% efficient to the USB output.

Stereodude said:

I think your math is off. That's 10Ah at ~3.7V, so 37Wh. 6.25Ah at 5V = 31.25Wh. Basically 84.5% efficient to the USB output.

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It's not my math, it's Xiaomi's. That's what they've printed on the rear panel.

Maybe 'efficiency' isn't the proper word in a technical sense, to describe 'useable capacity.'

6250mAh is what you can hope to get out of the unit, so that's 62.50% of stated/claimed total capacity, assuming the three 18650s have 10Ah of true capacity to begin with. Remember, these power banks don't discharge down to 2.5v/2.75v, so if they get down to the nominal 3.6v/3.7v, that is about 40% of capacity left, as a rough guestimate.

Now, I will say that I was able to get more than 6250mAh out of my fully charged Mi when I was charging up my GF's iPad 2, but I really wasn't paying close attention to it during the charging process and my KCX-017 volt/current meter adds some clicks to the counter over time.

Anyhow, get what makes you happy. When the power goes out and we're in the dark, most of us aren't going to be worried about whether Unit X is 62.5% efficient, or 81% efficient, right?

Chris

ChrisGarrett said:

It's not my math, it's Xiaomi's. That's what they've printed on the rear panel.

Maybe 'efficiency' isn't the proper word in a technical sense, to describe 'useable capacity.'

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How it their math? Xiaomi says it has 10Ah capacity. It likely does at the voltage of the internal batteries. It could have 10Ah of NiMH batteries in parallel at 1.2V or 10Ah of SLA at 12V. You're measuring the mAh of a 5V output. The output voltage is different from the internal battery pack voltage. mAh from the batteries and the output are not comparable. Even if the unit was 100% efficient you couldn't get 10000mAh with your meter due to the voltage difference between USB and that of the batteries in the powerbank. Do you think 10Ah of 1.2V NiMH batteries and 10Ah of 12V SLA are equivalent and that a powerbank of both should give you 10000mAh with your USB meter?

6250mAh is what you can hope to get out of the unit, so that's 62.50% of stated/claimed total capacity, assuming the three 18650s have 10Ah of true capacity to begin with. Remember, these power banks don't discharge down to 2.5v/2.75v, so if they get down to the nominal 3.6v/3.7v, that is about 40% of capacity left, as a rough guestimate.

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No it's not. mAh is not a measure of power or energy. You can't ignore the voltage. Xiaomi didn't claim it has 10Ah of 5V output.

When the power goes out and we're in the dark, most of us aren't going to be worried about whether Unit X is 62.5% efficient, or 81% efficient, right?

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I would have worried about that before the power goes out. If you get 5 good hours of sun on your solar panel do you want to waste 75% of the energy the panel collected in conversion losses? Would you rather have enough power to run 1 flashlight for 4 hours, or would you rather have a vastly more efficient solution that lets you collect enough power to run 3 equivalent flashlights for 4 hours each?

Stereodude said:

...I'd be way better off with a powerbank charger like the Tomo v8, or just a USB powered 18650 charger and giving up on NiMH AAs. There's only one 80% hit vs. 23%.

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I've almost come to that conclusion myself however, I'm testing a "hybrid" option for my small solar panel AA charging solution of using a USB powerbank with a USB AA battery charger (XTAR VC2 Plus) plugged into it. The powerbank though must have pass-through charging functionality which lets it act as a UPS for the battery charger. If the sun gets hidden by a cloud enough to shut down power production from the small solar panel, the powerbank kicks in and continues the charging of the AA batteries. If the shade goes away, the pass-through kicks back in and AA battery charger doesn't know the difference. The powerbank from my testing can actually in take more power from the solar panel than the AA charger needs so the powerbank can recharge itself if needed at the same time the AA batteries are being charged.

As mentioned in a prior post the XTAR VC2+/VC4 will not ramp their charging power back up once it is brought down due to lowered power input which can happen often when connected to a small solar panel. A power cycle (which can happen often too with a solar panel) will reset the charger but the VC2/VC4 charger have a 10 minute pre-charge period at the beginning of every cycle. The pass-through on the powerbank fixes this issue but I'm going to try the LiitoKala Lii - 202 charge to see if it will do better and without the powerbank in between.

Will the Toma V8 powerbank do pass-through charging? It would be a nice option to be able to charge 18650's at the same time the AA's are charging.