Charger that stops at voltage?

pipes

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I was wondering if there was a charger that you could set the stop voltage, for example if i wanted it to stop my eneloop aa at 1.4 or my 18650 stop at 4v? I have a Nitecore D4 that I have been using for years now and I think I am interested in one of the Xtar, maybe the vc4 plus, dragon vp4 plus, or the ac power one(if there isnt one that has a stop charge functionality) This brings me to a second question, I assume it doesnt matter, but, will the chargers that connect via usb c into a wall plug adapter charge just the same speed as the ac power chargers? I think since you can set the amps, it will be, but I am not sure and figured it would worth the ask. I think it is a neat idea with the usb c to a, you could charge batteries in a vehicle while driving or something.

TLDNR -
1. is there a charger out there, that you can set it to stop charging once a batter in that slot gets to a certain voltage
2. xtar vc4 plus or dragon(or other suggestions, not worried much about cost effective, more focused quality/function)
3. does the usb c input charge at same speed as ac power input

Thank you all for any time and consideration in reading this post!!
 

DIWdiver

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Hi pipes.

1. Some 'hobby' chargers have programmable charge termination voltage. I've seen one that has limited program ranges for various lithium chemistries, but not nickel chemistries. The common iMax B6 (and very likely its many clones) has none. I'd guess very strongly that all the chargers you mentioned and most if not all similar ones do not have programmable charge termination voltages, especially for nickel chemistries.

2. No suggestion.

3. USB C has a theoretical maximum of 100W power capacity. That's more than enough to charge a large handful of Eneloops. But not every host is able to supply all of that, and not every device is able to draw all of that. You need to look at the specs of your specific host and device to determine if you can charge the number of cells you want at the current you want. However, with that said, if you are only looking at charging 4 NiMH cells at 2A or less each, that's only 12.8W. Figuring in charger efficiency, maybe 17W from the USB. Any but the lamest host should be able to do that, and any decent charger should be able to do that. This question would be much more relevant if charging Lithium chemistries, where the charging power can be considerably higher.

TLDNR -
1. Not likely
2. No.
3. Very likely.
 

pipes

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Thank you for the reply! At most there will be 4 3400 18650s in there, usually once a year i top them all off, most of my lights dont actually get used much if im honest, i just like having them lol. I will just probably stick to that xtar dragon, probably overkill, but looks like an amazing charger.
 

DIWdiver

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Yeah, charging those cells at 1C could draw 75W or so from USB. You would have to be more careful to make sure your host and charger were up to it.
 

bridgman

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The Nitecore I2 and I4 (new models where "new" is a few years ago now) let you choose between (IIRC) 3.7, 4.2 and 4.35 for li-ion cells. Don't think you can select voltage for NiMH.

Default is 4.2 so if you are charging LiFePo cells it's really important to remember to change the voltage. If I used a mix of lithium chemistries I would probably try to find a dedicated charger for the LiFePo's (assuming one exists).
 

DIWdiver

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The Dragon VP4 plus manual says the charge voltage is 4.2 +/- 0.5V. That's pretty high for long-term storage. Given your use pattern, your batteries (cells, if I'm being pedantic) would live longer if you turned the lights on for a few minutes (3% or more of expected run time) after topping them up, to get them below 4.1V. Even better would be to use a charger with a lower charge voltage of 4.1V.

Even lower would be better. Optimum storage is at 30-40% charge, aka State Of Charge, aka SOC. Most lithium rechargeable batteries come from the manufacturer at 30-40% SOC. At this point voltage isn't as good an indicator, but you are generally looking at around 3.6-3.7V. Batteries in this state are also less likely to 'vent with flames' (lower SOC is better for this). IIRC, international shipping standards require (at least in some cases) that Lithium rechargeable batteries be shipped at less than 50% SOC (or maybe 40%, I forget). I assume this is to minimize fire risk.

That's why most products with lithium batteries say to charge them before use. Loose cells don't usually come with this notice. I'd guess that's because users of loose cells are expected to know this.
 

pipes

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Yes this is precisely why I want a stop voltage lol!!! I can just start manually taking them off charge at a lower voltage, was just looking for a more automated option.

When you say host, you mean where I am getting the power from right? Even though its usb, I would use a wall adapter on it. I assume i need to get a high quality anker one that will allow the high voltage. I dont know why they would sell high end chargers that connect via usb tho, doesnt seem like the best choice for charging large cells, but i guess they know what they are doing when they engineer this stuff.

I actually made a slight goof in my research. So the XTAR VC4 Plus does have a usb c input however it does come with a wall adapter as well, thats nice to know. The XTAR DRAGON VP4 Plus does run directly with ac power cord.

I also had to google lifepo4, but in doing so, i learned that my nitecore dv has a lifepo4 mode, and it appears if im seeing this correctly, the output is 3.7v. i didnt know what the output voltage meant until your post up there, that means how high it charges. So, putting this together, it sounds like I can put my 18650s on this charger, set it to the lifepo4 setting, and it will stop at 3.7v? I dont think this should harm the battery even tho its not lifepo4 should it?

InputAC 100-240V 50 / 60Hz
0.35A(MAX) 10W
DC 12V 1A

Output4.2V ± 1% / 3.7V ± 1% / 1.48V ± 1%
0.375A*4 / 0.75A*2

Compatible withIMR / Li-ion / LiFePO4:
26650, 22650, 18650, 18490, 18350, 17670,
17500, 16340(RCR123), 14500, 10440
Ni-MH / Ni-Cd:
AA, AAA, AAAA, C
 
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sbj

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With the SKYRC MC3000, the voltages and currents can be adjusted in many areas.
With NiMh, however, only from 1.47 to 1.80V.

With LiIo, the end-of-charge voltage can be set from 4.0 - 4.25V. In addition, there is a storage program that can be set from 3.65 - 4.0V.
The discharge voltage is adjustable from 2.5 - 3.65V.

This means that you can bring a LiIo battery to any desired voltage between 2.5V and 4.25V (or 4.40V LiHv). :)
 

dragosios

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You can try a lab power supply, then you can control both voltage and current. But then comes a greater responsability and knowledge, mistakes can have consequences for cells.
 

DIWdiver

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You can try a lab power supply, then you can control both voltage and current. But then comes a greater responsability and knowledge, mistakes can have consequences for cells.
That's a good idea. Constant voltage, constant current is exactly how LiIon cells are supposed to be charged. Lab supplies (aka bench supplies) can be had pretty cheap these days.
 

dragosios

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That's a good idea. Constant voltage, constant current is exactly how LiIon cells are supposed to be charged. Lab supplies (aka bench supplies) can be had pretty cheap these days.
Cheap ... yes, somehow. I would check ebay for brand-name lab-grade used ones, I had a few of them cheap sometimes.
Otherwise there are newer ones on a PCB who can do a great job for maximum of a few amps at lower voltage, but they usually need an external energy source, e.g. a recicled laptop power supply or similar.
 
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