Anybody tried these 3800mah AA batteries

ZOR

Senior Member
I have been playing with a couple of Ultrafire red/grey 3800mah 18650 batteries, but don't know if they have internal protection to avoid total discharge. As well as this still a bit hesitant to use much due to many reports of fake, dangerous etc.

I then saw these batteries, and assuming they are AA friendly and safe?

Anybody tried them, will ordinary charger charge them?

http://www.ebay.ca/itm/4-x-3800-mAh-AA-RECHARGEABLE-BATTERIES-MAXELL-UNICELL-NiMH-R6-FREE-WORLDWIDE-/161135403407

EDIT:Maybe fake claims if this heading is true

How to Spot Fake Batteries: The Longest Way Home Travel
www.thelongestwayhome.com/resources/How-to-spot-fake-batteries.html
Just how do you tell the difference between real rechargeable batteries, and a fake ... Most rechargeable AA batteries in Europe and U.S.A. are a maximum of 2700 mAh Meaning their strength. Fakes often make claims to be 3800 or 4000.
So maybe I answered my own question?
 

eggdweather

Senior Member
I have never seen a NiMh that has a capacity over 2800mA, certainly not 3800, so suspect them as you already do. The 18650 batteries are much higher capacity, I have some and they work OK, mine do-not have an internal protection, they are 4000mA and Li-ion. The protection I apply is not to allow the cell voltage to drop down below 3.6volts, which is the 20% charge remaining voltage. The full charge voltage is ~4.2volts.
 

premelec

Senior Member
Last lot of high capacity NiMH batteries I got from Ebay were LOW capacity and leaked! Got my money back and send them to recycler - I'm sticking with known brands... :)
 

ZOR

Senior Member
Thanks all. I think too many Chinese are making fake products, batteries, chargers etc, all carrying a severe risk. I like the two 18650 batteries I boughton Ebay, maybe I was lucky, but I still have doubts as to whether they are really safe. I have asked the supplier three times, do they have protected electronics in them to protect draining below the safety voltage and I get rubbish answers how they are so pleased to do business with me, and don't give bad feedback,
Are there any gauranteed sources in the UK for these batteries.
Egdweather: How do you add your protection in for keeping voltage above 3.6 volts. At the moment I am using the Picaxe to monitor the voltage and was thinking of using a latching relay to cut the power off at a point but never using a latching relay before I don't know what happens when power goes off them ie do they revert position.

EDIT Here's another one
http://www.ebay.co.uk/itm/like/281554093013?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&chn=ps&device=c&rlsatarget=&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108
 

eggdweather

Senior Member
I use mine in my model aircraft Remote controller Tx and use the display to monitor voltage plus it has a voltage monitor and alarm (Taranis), so three in series gives me a huge capacity battery that starts off at 12.6 volts and drops quickly to the nominal 3.7v/cell then stays there until depleted at 3.6volts/cell, then recharge time. Original battery was 800mA-Hr so the li-ion type is x4 to x5 more capacity, and I could get even larger capacity types.
 

Haku

Senior Member
I doubt those AA's are even 2000mAh, if the maker faker has gone as far as fabricating wholly inaccurate specs on the packaging they're hardly going to make sure the cells deliver even half what their lies say.

Go with trusted brands you know or someone you trust reccomends, and nowadays you'd be nuts not to buy the LSD (Low Self Discharge) type that can hold their charge for weeks/months with very little self discharge. My personal favourite AAs are the Uniross Hybrio, I give em a charge and a month later I can put them in a device and they power it like they were charged yesterday.
 

Pongo

Senior Member
Yep, it's a scam. If you google "3800 mah aa" you can find any number of discussions concluding that this capacity in an AA package is pretty much impossible with today's technology. See this discussion for some interesting test results.
 

premelec

Senior Member
Have you seen the youtube stuff about using supercaps starting your car? Any little trickle into these can eventually produce a really large current - however as with all series devices there may be charge balancing requirements... Supercaps still are expensive...
 
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manuka

Senior Member
Near bullet proof but powerful 3.2V LiFePO4 rechargeables may be your friends - the new breed of "pocketable" automotive jump starters feature them, as do the likes of the esteemed BYD battery buses .

I personally now avoid using NiMH/NiCd at the "AA" (& "AAA") level as LiFePO4 ("LFP") equivs. have been so satisfactory. Although most 14500 AA LFP types are only 700mAh,they've a steady 3.2V until almost total discharge, so are almost the same energy as 3 x 1.2V NiMH. A single LFP will power most of today's circuitry, without the devil of suspect cells,wonky multi-cell contacts or larger battery enclosures.
 

ZOR

Senior Member
Thanks everyone, there's a lot here to read.

Jim: Thanks Jim, I would use an SLA battery but too big physically and I want the battery internally fitted. Only sbace for 4 AA's or two 18650's.

Egdweather:I am still looking for battery cutoff circuitry, latching relay won't help?

Stevesmythe:I saw another seller on Ebay yesterday, I sent him a message saying he was selling fake product. He replied asking for more info so I copied him a paragraph I'd found, he must of panicked because he said he was giving me credit/Paypal and I had never purchased from him? Interesting will wait to see what comes through.

Pongo: Thanks for link, interesting read

Premelec: Thanks, interesting.

Manuka: It's a shame batteries don't do what labels say. One of my projects is a PIR box. Maybe I should consider putting in a wheel generator inside with a mouse. The mouse will start running round the wheel when it see's someone, double PIR?
 

premelec

Senior Member
Stan... I've been using single Li cells with cheap regulated up-converter - about 80% efficient - not great for idle drain but great for on/off use...
 

srnet

Senior Member
The protections circuits in Lithium cell are there to prevent (or at least reduce the risk of) explosion and fire; they are most definelty NOT intended to act as a low voltage switch off for the device they are powering.

Your mobile phone battery will have a protection circuit inside, but your phone will switch itself off long before the battery protection circuit is activated, in order to prevent damage to the battery.
 

srnet

Senior Member
Thanks srnet, I thought the circuit boards inside some 18650 batteries prevented discharge below a certain voltage, so that's put me right, thanks.

EDIT: What does this do, thought these were in some batteries
https://www.fasttech.com/product/1451307-charge-discharge-protective-circuit-board-for
They do, but the cut off voltage, 2.4v, is way to low to prevent damage to the cell, to quote an appropriate page from WikiPedia;

However, particularly in the case of lithium ion batteries which are used in the vast majority of portable electronics today, a voltage cut-off below 3.2V can lead to chemical instability in the cell. The result being a reduced battery lifetime. For this reason, electronics manufacturers tend to use higher cut-off voltages, removing the need for consumers to buy battery replacements before other failure mechanisms in a device take effect.
 

manuka

Senior Member
ZDR: Mouse? What kind of talk is this in a solar age! I installed ~7 solar charged PIR yard lights in several properties ~2012-13, with all powered by a single AA sized 14500 LiFePO4. They're bright, but none of them were costly (I recall ~US$20 each), & charging to those in shaded areas was easily handled by extending the supply wires from their small PV. Not one installation has missed a beat in 2-3 years.

Although NZ has sunny winters, with snow almost unknown, it can get wet & windy at times. I'm only a stones throw from the sea as well, with salt spray an issue after storms. I'd not trust Li-Ion for such applications, & past installations using multiple NiCd/NiMH became a dead loss after only 1-2 years.

srnet: Although heavy duty solar slanted this LFP thread may be of interest? Stan.
 

ZOR

Senior Member
Thanks srnet, I was going to buy those items but will now go back to finding how I can cut the battery off at 3.7 volts. I am okay monitoring, but as I only have one power source if I use a relay to cut input volts the relay will drop out with no power there and keep cycling on/off.
 
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stevesmythe

Senior Member
ZOR I don't remember if you said what Picaxe you are using but you could maybe consider using calibadc10 to monitor the supply voltage. With a 28X1 or 40X1 Picaxe you could then hibernate the processor to prevent further battery discharge and damage.
 

ZOR

Senior Member
Thanks, I am using an 08M2, and using calibadc10, however have other bits taking power. Maybe I need a second battery with a relay when energised disconnects the primary battery, but then what happens with battery 2 going dead. Like a chicken and egg

How does an iphone shut off when battery low?
 
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ZOR

Senior Member
Spent all day trawling for circuits to disconnect my load on an 18650 battery when it's output falls to 3 volts.

Is this circuit I found too basic?
I was thinking of using the Picaxe to trigger this circuit using calibadv10 but does this circuit me finding a 3 volt zener?

ASKFORUM.jpg
 

premelec

Senior Member
@ZOR I have made cutoff circuits using TLV431 or TL431, depending on how low you want cutoff, - PMOS transistor in series with V+ 431 - resistor between Gate and Source - resistive divider from drain [output V+] to V- and divider center goes to 431 control pin to set hold voltage, 431 + pin goes to Gate to turn on the PMOS when adjustment voltgae high enough. - basically 3 resistors and PMOS transistor [though I use a pot for the divider's 2 resistors to make voltage setting easy]. PMOS should be logic level. Initial turn on can be made by small capacitor or swtich across the PMOS [Source to Drain].
 

ZOR

Senior Member
Thanks premelec. I have not used these semiconductors before, but came across someone using the TLV431. when you say the TL and TLV offer two types of cutoff, I am looking for a quick total switch off to the load. I will have done all the homework prior to this event using calibadc10.

Is this pasted circuit what you were suggesting?
TL431CIRCUIT.jpg

As I have not used PMOS transistors before, is the one on the vircuit okay or can suggest another. Thanks again
 

premelec

Senior Member
@ZOR - similar except I use NO op amp - just use a resistor from PMOS Source to Gate and Gate to TL431 + . The caveats are that the 431 has a small current draw before it switches on so the R to the PMOS gate must not develop voltage on the PMOS Gate enough to turn it on and the voltage divider to 431 draws a bit of current. The circuit you show has the 431 connected as a simple zener rather than _adjustable_ zener [that's by connecting the adj terminal to the top - rather than putting the adj terminal from an output voltage divider]. Look at the TL431 [or TLV431 which has lowever voltage ref and lower current capability etc] datasheet.
 

ZOR

Senior Member
Thanks premelec, I will read through what you say and get a diagram together and play with it. I have ordered the TLV431 and will look for a suitable PMOS device. I don't know how much current the circuit will continue to draw when the load is cutoff but will know more when bits put together. Thanks again.
 

premelec

Senior Member
@ZOR if you look at the internals of TLV431 on datasheet you'll see it has inside an OpAmp and reference - If I remember correctly the TL431 not only has higher current capability but also operating voltage - limited to 6v on TLV model. I need to draw up a schematic and make a picture of it - The TLV has about .05ma [50ua] before break point and TL about .5ma [500ua] before break point so this current times the gate resistor should be about 1/2 gate threshold voltage or lower resistance.
 

premelec

Senior Member
Attached circuit

Note PMOS must be bridged to turn on [a capacitor can work for initial turn on] and that it's Vgs ON must be lower than dropout voltage you want... Sorry diagram not clearer... about 2K usually ok for Rgate.
 

Attachments

ZOR

Senior Member
Many thanks both, great help. Can I ask premelec, what is the value of potentiometer on the output. Thankyou both for the help.
 

techElder

Well-known member
Stuart, I read something in your code at your post linked above in #30. Could you comment on it there? Thanks.
 

premelec

Senior Member
@ZOR the pot value is not critical - just to divide the output voltage to the TL431 internal ref to turn it on - 1.2 or 2.5 volts depending on which 431 you have - current into ref adj is probably a few microamperes [look at data sheet...] - so 10K to 100K could work fine.. depends on your power budget 1M might work... Note that a PNP bipolar transistor can work in this circuit also though the VceSat could be higher than the PMOS on drop.
 

ZOR

Senior Member
Thanks again, that should get me going in the right direction. Have a good weekend, regards
 

ZOR

Senior Member
My TLV431 devices arrived today so I thought I would see what they did. Am I wrong, as because of their circuit symbol, I took them as being a variable zener. However I tried all sorts of values in a resistor potential divider into the reference pin but I could not get it to lose output when the supply voltage dropped to 3.7 volts, which I thought should happen to drive the mosfet? I put anode to ground, the cathode to 1k resistor to supply input, and split divide resistors between +v and 0v to feed the reference pin.
 

premelec

Senior Member
TLV operation

@ZOR - I don't think you have a correct view of the 431 - see attached from the data sheet - in effect there is a bipolar transistor which shunts current from cathode to anode when Vref is higher than the internal reference. Note that the external reference input can come from either the cathode terminal OR an external divider... It's a bit tricky as the unit must have at least the internal Vref on the input terminal to work.

Note also that for the circuit to work in cutting off low voltage the Vgate on of the PMOS + Vref of the 431 must be less than the voltage you are trying to cutoff at - hence need for low Vgth...
 

Attachments

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ZOR

Senior Member
Thanks for the information. I tried various values of a potential divider to drive the external reference, and my values I was playing with were either higher or lower than the internal ref voltage. I was trying to make things happen on the range from 4.2 volts down to 3.5 volts where I was wanting it to change being my lowest voltage allowed for my battery to go to. I tried potentiometers as well as fixed resistors. I presumed something must happen at my lowest permissable voltage to affect the gate of the mosfet. Both these devices are new to me and with my lack of knowledge fun to understand.
I am using the Picaxe to monitor the battery and could make a port go high at some point to do something, but it's like sawing off a tree branch while your on it The unit it will come back on when it loses it's power if I use a relay and would be using power for nothing,otherwise lost on alternatives, can't seem to think outside of the box.
 
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premelec

Senior Member
@ZOR - it is certainly possible to have a PICAXE turn itself off and this has had some discussion on this forum - a simple way is to put a PMOS transistor in series with V+ [Source to V+ Drain to PICAXE +] with a resistor from the gate to a pin on the PICAXE which will turn on and _stay on_ while the program is running - there is a delay while the PICAXE starts and sets the gate connected pin LOW. When this pin goes high it will turn off. Same with a relay - PICAXE only on while the relay is actuated and only is it actuated via a PICAXE pin. Give it some more thought and try a relay circuit alone that will latch on through an actuated contact only [when it drops out it won't reset]; these methods all require some extra circuit to _start_ them holding. Note that you can calibrate a relay circuit so it de-actuates below a certain voltage and then won't reset until bridged again to start the latching action. Relay need more power than MOSFETs and have inductive kicks and such that should be accounted for [parallel diode]. P.S. there is NO box :)
 

erco

Senior Member
Small latching relays are perfect for allowing low-power devices to turn themselves on & off. Zero power is consumed in on or off states, just a brief blip to energize a coil to change states as necessary. That's how battery-powered residential thermostats run for a year on 2 AA batteries. For instance: http://www.ebay.com/itm/NEC-Miniature-Single-Coil-Latching-DPDT-Relay-5V-1A-SMD-SMT-EB2-5SNW-L-/110995424098 is a one-coil type. Reversing polarity on the coil sets & resets the latching contacts. Some other types have 2 coils, one sets, one resets.
 

ZOR

Senior Member
Thanks again premelec. I want to totally disconnect the battery from the Picaxe driven unit. I considered using a relay held in by itself but dropped the idea on added consumption. I was also worried in some conditions things would reset on powering off. I did look at a latching relay but could not find for sure if that would not reset. Erco, thanks for telling me there were two coil types, so if I have a large electrolytic on my +v rail I could disconnect, and on power on have a reset button. Will play with that as well as more with premelecs idea. Regards
 
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