I have a Xtar VC4 battery charger that I use almost every day. It charges my 18650, 14500 and rechargeable AA batteries fine.
I recently bought (8) EBL 10000mAh NiMH rechargeable low self-discharge D cells from Amazon.
The VC4 is supposed to charge D cells along with several other sizes.
I put 2 of them in my Xtar VC4 charger in channels 1 and 4, as required. The voltage before charging, from my voltage meter, was 1.26 volts. After charging overnight, the reading on the charger was 1.4 volts and the mAh gauge read 0010, with the last zero flashing. The light on both channels are still red after an overnight charge. My other batteries show a green light when they are done charging.
I would greatly appreciate your advice if the batteries are ok and not defective. I have never bought rechargeable D cells before and never charged them on the Xtar before. Below is the Amazon link.
Might just take longer’n overnight to fully charge ’em.
If 4 digits, getting past 10000mAH (5 digits) might show “tilt” by blinking the last zero. Eg, 11000mAH might read “0011” with the last ‘1’ blinking. Ain’t got a VC4, so am only guessing.
And don’t forget, that mAH when charging is not the cell’s capacity.
If you fill your car’s empty gas-tank and dump several gallons on the ground for whatever reason (leaky hose, sloshing out of the filler-pipe, etc.), you could end up putting “20gal” into a 15gal tank.
From what I’ve read about Ni batteries is that they take a bit more input then they put out. My knowledge disclaimer is that I’ve only used them in Streamlight products with their built in chargers.
I’m curious what current’s charging ’em up. 10000mAH at 500mA would take 20hrs, and that’s assuming 100% efficiency. If that wastes half, then it’d be 40hrs, or just short of 2 days straight.
Brand new, never used cells?
What is the charge rate? What are your charge rate options? NOTE - looked it up, 0.5 and 1A
[From the review - For charging at full current the charger is fairly demanding of the used usb power supply. It is possible to use weaker supplies, but the charging will be slower or sometimes much slower. With the current dial it is easy enough to see when that happens and it is time to get a better usb power supply. ]
FWIW, the EBL’s are only OK. There really are no 10000mA D-cells. It’s an inflated claim, which is common.
NiMh is harder to charge properly than Li-on. Charge ‘em too FAST, and they terminate prematurely or get hot. It’s actually nearly impossible to do this with consumer grade charges for batteries that large. It’s very easy to do with AAA and AA.
Charge ’em too SLOW, and they may never terminate….just charge ’forever’, or until you pull the plug. This is very easy to do with big cells on smaller chargers. They simply were not designed for NiMh capacity that high, no matter what the specs claim.
In either case you will see a very unrealistic capacity; too little, or too much, neither being right.
Since the charging NiMh is always ‘sloppy’ (some overcharge required to do it right), you will always put in more than you took out, if you have the ability to even track it.
If the cells are old, or not been used in a long time the internal resistance may be high. This will further mess up charging termination. I have some REALLY old D-cells that are quite hard to charge properly because of high IR.
Cycling a few times will help, and take forever. I have a charger that will cycle at 2A charge and 1A discharge specifically for big NiMh cells. Even that takes awhile.
I received the new EBL D cells on 7/13/2020 from Amazon. I assume they come charged, but not sure if so and if they are only partially charged.
The specs from Xtar are below:
Specifications:
Input Power: DC 5.0V 2.1A
0.5A CC Current: 500 or 50mA
1.0A CC Current: 1000 or 80mA
Cut-off Voltage: 4.20V
Operation Temperature: 0-40° C
What kind of charger do you have for NiMH cells?
Thanks very much for your detailed, informative reply.
Ted
That should be fine. Are you using a good USB Power Supply?
That could be holding you back.
Set that sucker for 1000mAh charge rate if it will let you.
My wife and I used to dive almost weekly with lights requiring 4xD-cells. I needed to charge a lot of large cells routinely. I got this: MAHA MH-C808M AA - AAA - C - D Battery Charger
Excellent charger if all you want to do is large cells. It can be throttled down to 1A but even that’s a bit hot for AA. It is expensive, but it did heavy work for years and is still going, though seldom used now that I’ve moved on from D-cells.
I have used other chargers for D-cells, but they just don’t have the juice. Large D like you have are just fine with 2A. Depending on the termination algorithm they may not do well at 1A, and have a much higher chance of missing termination at 0.5A.
@ 1.26v the charge state is OK. With NiMh you don’t know if that is 1/8, 1/4, 1/2, or 3/4 full. Voltage is a poor indicator of capacity for NiMh.
[People used to know and understand NiMh. Now they seem to know Li-on and don’t understand NiMh. They are entirely different chemistries with very different characteristics, especially when it comes to charging.]
First, I’d try what @jeff51 suggested. Make sure your power output allows a reliable 1A charge rate. If it’s not up to that level the probability of missing termination goes up.
(Note - You CAN charge them at 1/10C > in your case use 0.5A, and leave them in there for a long time. This would be turning your Xtar into a ‘dumb’ charger, which was common 15 years ago. I still have several)
Since they came out at 1.4v that’s a pretty good indication they are full. A freshly charged NiMh will be just over 1.4v and lose that probably within 24 hours of resting down to 1.3x volt. That’s just how they work.
If you still have some to charge I’d do it during the day when you can check it occasionally. The weird reading may be the capacity ‘odometer’ turning over since it’s not designed for that much capacity. Hard to tell without watching it.
Then drain them in whatever you are going to use them in, and do it again.
My Xtar VC4 battery charger comes with a Samsung Travel Adapter that is rated as follows:
input: 100-240V 50-60Hz 0.15A
output 5.0V 0.7A
It has a USB cable as well.
I just checked my overnight charge of 2 of the EBL’s. One of them says full with 1.4 volts reading 3334 mAh. The other one is still reaching full charge status.
Thanks very much for your informative reply. I will charge them for a longer period. One of them that I charged overnight finally reached full charge. I’m hoping the other 7 do as well.
One of the 2 EBL’s I charged overnight finally reached a full charge on the VC4. I’m hoping a longer charging time will fully charge the other 7 as well.
0.7A is limiting the output. I have found that a LOT of USB cables, especially those that come with cheap Chinese products have a high resistance, plus the longer the wire, the higher the resistance.
Combine a low output, and a poor cable and you may end up messing up the termination on batteries that large. It might work just fine with AA as you will tend to charge at 0.5A.
You will get better performance if you get a charger with an output of at LEAST 1.0A, and I suggest 1.5A or higher for better overhead. Easy to get 2.0A+ power supplies.
Best cables I’ve found…period….are Monoprice Select Series (or Premium) USB-A to Micro B Cable, 2.4A, 22/30AWG. I use the 0.5 foot and 3 foot almost exclusively. Low resistance, plugs hold up. always just seem to work.
I’ve checked a LOT of cables, and thrown away a mess of the worst ones. A special USB Tester with resistance function is needed to check them with high accuracy.
In the manual it says you need a wall adapter that can do 5v 2.3 amps out. Anything lower than that will slow charging time.
The most the charger can do is 1 amp each per 2 bays. So 10 hours or more with a drained 10,000mah battery is the very best you can do with the VC4.
The other posters are correct.
Your supply is way too wimpy.
See if you can find something in the 2.5 amp or more range.
A little extra won’t hurt and should be enough to make sure your charger is getting plenty of current.
Another problem might be your charging cable. Crappy ones won’t pass enough current.
But get a better power supply first. That’s your main problem.
All the Best,
Jeff
Thanks again very much. The EBL’s are charging to full capacity now, but as you indicate, are taking a long time to fully charge. Most are charging in 2 overnight charges.
Best wishes,
Ted