PDA

View Full Version : 14500 Lithium batteries - same size as AA (nearly)



Loopy Byteloose
12-29-2011, 02:34 PM
I went shopping for some generic Lipo batteries for RC electric airplane and discovered the 14500 series that are 3.7V and some are even over 2.4ah capacity. They are 0.5mm longer than regular AA.

I was a bit surprised that I had several options with rather big increases in capacity. I have the 18650s, but mine are 1950ma and now there are 3000ma ones available. And in the 16555, I can get 2700ma.

Since these charge much faster than the NiCd genre, and provide more than triple volt in an AA package - it seems time to permanently set aside Alkaline and NiCd batteries.

erco
12-29-2011, 05:03 PM
Have to round some up, they do sound great!

Hmmm...

Until the wife or kids grab 4 without asking and use them in place of AA batteries.

I love the smell of coffee, Christmas trees, and magic smoke in the morning!

An Ebay search shows many rated at 1200 mA: http://www.ebay.com/sch/i.html?_nkw=14500++battery&_sacat=92074&_sop=15&_odkw=14500+Lithium+battery&_osacat=92074&_trksid=p3286.c0.m270.l1313

sam_sam_sam
12-29-2011, 11:41 PM
[QUOTE=erco;1062200

Hmmm...

Until the wife or kids grab 4 without asking and use them in place of AA batteries and magic smoke ! .....> come out

[/QUOTE]

I caution you to let other in your house hold that these cell are NOT the same battery that they use to

Loopy Byteloose
12-30-2011, 10:36 AM
Well, I returned to the store and bought a pair of 1200ma 3.7V 14500s. Upon taking a close look, they are a bit longer (maybe 1/16th of an inch) than a true AA. But they seem like they will fit nicely in a generic AA battery holder.

It seems with the amount of power available and the higher voltage, these guys will begin to seriously overtake the Alkaline cell market. NickelCadium and such never got a good foot hold because they didn't provide as high a voltage and charge was often less.

At least for hobby stuff, I am ready to go all lithium now. Just think, one battery, no regulator can run a Propeller for roughly 10 hours.

erco
05-30-2012, 10:31 AM
These are getting cheap too. Ten for $13 shipped. Probably not the 1200 mah claimed, but maybe worth a shot. Power your Scribbler or BoeBot with just TWO of these 3.7V babies. Li-Ion charger required.

http://www.ebay.com/itm/10-x-3-7V-1200mah-14500-AA-Li-ion-Lithium-Rechargeable-Battery-/251068691004?pt=US_Rechargeable_Batteries&hash=item3a74dc323c

tonyp12
05-30-2012, 03:05 PM
LIFEPO4 is the future.
http://www.ebay.com/itm/2-Pcs-3-2V-1200mAh-123A-CR123A-16340-LiFePo4-LFP-Rechargeable-battery-Ultracell-/150823210725?pt=US_Rechargeable_Batteries&hash=item231dc38ee5

Rechargeable 2000 times.
Fully charged in 30 minutes,
Can handle very high current peaks.
No heavy-metals.
No explosions

Here is a charging ic: (simple rules to lifepo4 is: never below 2,.2v and never higher than 3.65v)
http://www.mouser.com/ProductDetail/Microchip-Technology/MCP73123-22SI-MF/?qs=E6wAi2XWqcMqq2JIuuGEkYadBjEA7JSociTfMM1zDwg%3d

Duane Degn
05-30-2012, 03:12 PM
Just think, one battery, no regulator can run a Propeller for roughly 10 hours.

A full charged Li-Ion is about 4.2V. Do you use a diode between the battery and the Prop?

BTW, I just purchased a set of 10 from erco' eBay link.

Duane Degn
05-30-2012, 03:22 PM
LIFEPO4 is the future.
http://www.ebay.com/itm/2-Pcs-3-2V-1200mAh-123A-CR123A-16340-LiFePo4-LFP-Rechargeable-battery-Ultracell-/150823210725?pt=US_Rechargeable_Batteries&hash=item231dc38ee5

Rechargeable 2000 times.
Fully charged in 30 minutes,
Can handle very high current peaks.
No heavy-metals.
No explosions

Here is a charging ic: (simple rules to lifepo4 is: never below 2,.2v and never higher than 3.65v)
http://www.mouser.com/ProductDetail/Microchip-Technology/MCP73123-22SI-MF/?qs=E6wAi2XWqcMqq2JIuuGEkYadBjEA7JSociTfMM1zDwg%3d

Tony, These look interesting.

Have you every used these batteries and the charger?

What's the battery's max voltage?

How would you suggest powering a Prop from it?

Loopy Byteloose
05-30-2012, 03:53 PM
Inserting a diode or two would not hurt, though I suspect that the Propeller would survive 4.2 volts.

One option is to use a tiny bridge rectifier to have two diode drops and to not have to worry about correct polarity at the battery mains.

The fact that lithium batteries charge so quickly is really quite wonderful. NiCads are slow. Lead Acid is slow.

I see my last post was in December and the truth is I have yet to fully explore these. I was thinking of actually powering an R/C airplane with brushless motor, but I've yet to finish building the plane. All the parts are here, I just have to get to it.

Duane Degn
05-30-2012, 04:05 PM
I was thinking of actually powering an R/C airplane with brushless motor, but I've yet to finish building the plane.

Thanks for the sugguestions about a rectifier.

I think one reason LiPos are so popular with R/C aircraft is they lack the metal can of a Li-Ion so weigh less. I also think AA size might not be the best size for R/C aircraft because of the can of the battery is likely a larger percent of its weight than sub-C cells (I'm thinking of surface area vs volume). These should still have a much better energy density than any of the old NiCd packs.

erco
05-30-2012, 05:10 PM
BTW, I just purchased a set of 10 from erco's eBay link.

Silly Duane. He took the bait AGAIN. :)

GordonMcComb
05-30-2012, 06:08 PM
The LiFePO4's are good (with the right charger) as their nominal voltage is 3.2V, compared to 3.7V of traditional LiPo. So even fully charged they work well with 3.3V systems. The problem is many of the ones you can readily buy have a low capacity -- in the neighborhood of 300 to 400 mA, and are intended for solar applications. Be careful what you're getting, and read labels thoroughly. They are safer than LiPo, can be recharged more times, but they don't have the energy density of traditional LIon cells.

-- Gordon

Tracy Allen
05-30-2012, 07:44 PM
I like dealing with http://www.batteryspace.com/, partly because of the wide selection of cell sizes and packs they have available, and partly because their office is a local will-call here.

There is a lot of information on their site, for example,
LiFePO4 at 120 Wh/kg
LiCoO2 at 200 Wh/kg
Li-poly at 160 Wh/kg
Pb-acid at 35 Wh/kg
NiMH at 80 Wh/kg

Duane Degn
07-04-2012, 08:07 AM
These are getting cheap too. Ten for $13 shipped. Probably not the 1200 mah claimed, but maybe worth a shot. Power your Scribbler or BoeBot with just TWO of these 3.7V babies. Li-Ion charger required.

http://www.ebay.com/itm/10-x-3-7V-1200mah-14500-AA-Li-ion-Lithium-Rechargeable-Battery-/251068691004?pt=US_Rechargeable_Batteries&hash=item3a74dc323c

I received the Li-Ion cells from erco's ebay source a few weeks ago and today I received these below.:

http://forums.parallax.com/attachment.php?attachmentid=93947&d=1341382459

They look like batteries, but they're not.

They have zero volts across their terminals and very low resistance from one terminal to the other. I think they are just empty metal shells.

One of these "cooloop" cells weigh 4.6g. An "eneloop" AA cell weighs 26.0g.

I think these were sent by the same people selling the Li-Ion cells.

It occurred to me, these could be used with the Li-Ion cells to lower the voltage when using a multi-cell battery holder. If one had a three cell battery holder and used one Li-Ion cell and two "cooloop" cells, then the voltage would be pretty close to what one would get from using three NiMH cells.

Did any of you purchase batteries from the ebay item erco's linked to? If so, did you also received these battery holders with fake shunt cells?

Edit: This was not a rip off. The seller went out of their way to make it possible to use the Li-Ion sells in consumer goods. See erco's post #18 for clarification.

erco
07-04-2012, 08:47 AM
Yes. they had previously emailed that they were going to send them to avoid safety issues from too much voltage. I thought that was very responsible for a Chinese seller.

Loopy Byteloose
07-04-2012, 10:28 AM
Look like batteries, but are empty. Any one want to buy some fake TO-3 power transistors. My local retailer won't accept my return - even the Motorola emblem is a generic M, not the 'bat winged' logo and the lable is 90 degrees from the genuine.

There are some very weird fakes about. Audio electrolytic capacitors that actually have a smaller out of spec capacitor inside the larger's case.

I don't use E-Bay and try to return what I buy over the counter so as to let them know that they are not buying from the right kind of people.

BTW, lithium batteries that have less that the appropriate voltage, do short circuit. Could it be that they just sent you defective batteries?

And, never use a new lithium rechargeable without first charging. If you drive the battery too low, you have destroyed it.

Sure, they may be dummy batteries. But it is still a cheat, isn't it?

Generally, reputable electronic parts retailers use battery sales to bring them repeat customers. Radio Shack has for years. They won't sell bad quality batteries as unhappy customers don't return. It is similar to a camera store selling bad photographic film or a donut shop with lousy coffee.

Duane Degn
07-04-2012, 06:13 PM
Yes. they had previously emailed that they were going to send them to avoid safety issues from too much voltage. I thought that was very responsible for a Chinese seller.

I read one email from the seller cautioning against using the Li-Ion in consumer goods since the voltage would be too high. They also sent a second email which I assumed said the same thing and I didn't read it.

Now I think the second email was to to tell me these battery spacers where on their way.


BTW, lithium batteries that have less that the appropriate voltage, do short circuit. Could it be that they just sent you defective batteries?




These batteries are so light weight, they're obviously hollow inside. I'm sure they're not defective batteries.



Sure, they may be dummy batteries. But it is still a cheat, isn't it?


I don't follow you. I don't think it's a cheat.

I purchased Li-Ion batteries that are AA size. The ebay page made it clear the voltage of these batteries were too high to use with normal electronics equipment.

I plan to use my batteries in custom projects and I have a lot of AA battery holders so it's easier to me to use AA sized Li-Ion cells than the other sizes.

The seller not only went out of their way to remind me of the danger of using these batteries in normal equipment but went the extra mile and shipped these blank cells so we can better match the correct voltage if we choose to use them with consumer equipment.

Each cell has a "Do Not Charge" warning on it. I also think the battery cases are pretty cool.

I don't see this as a cheat at all. I'd go out of my way to buy from this seller again. They seem very conscientious.

erco
07-04-2012, 06:25 PM
Whoa, fellas. For clarity, please allow me to repeat.

There is no problem.

There is no scam.

There is no conspiracy.

No one is selling empty batteries.

This is a particularly great thing from an unusally responsible Ebay seller, freedom345. The seller from whom Duane and I bought ten (10) 14500 batteries shipped them to us in fine style. No problems. Nice batteries delivered in a timely fashion. That could have been the end of it, all parties happy. Then shortly thereafter, the seller sent this email:

Hi.
Dear buyer, thank you for purchasing our products.
I must remind, because it is 3.7V AA Li-ion battery, ordinary electrical using a two 1.2V or 1.5V AA battery. If you use two 3.7V Li-ion battery will damage the electrical, Be sure to look at the voltage of the electrical appliances before use.

Thanks & Best regards

- freedom345

Then a while later, the seller sent this email:

Hi.
Dear friends, thanks for purchase.
In most cases, this battery can only use 1pcs, another battery tube instead, if use 2pcs 3.7V Li-ion battery, may damage the electrical, we will send the same number battery tube to you immediately by free.

Thanks& Best regards

- freedom345

So unsolicited and at his own expense, the seller shipped a package of ten (10) battery tubes (shunts), one for each battery purchased. So you could use one battery and one shunt in place of two AA batteries. Not only that, but they sent them inside some lovely polyethylene battery cases, three cases that hold 4 batteries each. Especially wonderful for storing charged batteries. Mind you, we didn't pay a penny for any of this.

Now how is that a bad thing? I think I'll order another set of ten batteries just to support this fantastic and responsible seller.

Plugging away, here he is: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=251100046291

Edit: Duane beat me to it. DEGN! (Newman!)

Loopy Byteloose
07-04-2012, 06:37 PM
I understand now -- they were selling regular Lithium and providing for safety in situations that you might try to replace the Alkaline AA cells, you need 'dummy batteries' and that was what you wanted.

r/c airplane users used to buy 'dummy AA batteries' so that they could use regular AA alkaline batteries instead of NiCad AA batteries in the transmitter. HAM radios have done similar things.

One point that is important.

If you build something that demands quite a bit of discharge, you need to shut down the battery before it gets too low. If you have a separate charger, that may be an issue. I have some 4-wire 3.3volt low-dropout regulators and the 4th wire shuts down the regulator. It can be wired to create a shut off threshold.

Not exactly sure what to do if no regulator is used.

Duane Degn
07-04-2012, 06:38 PM
I think the miss-understanding arose by my calling them "fake" cells.

I completely agree with erco (on this topic), this seller went out of his way and at his own expense to send these shunt cells so those who purchased the Li-Ion batteries could use them with normal devices.

I apologize if I made it appear I was being ripped off.

Duane Degn
07-04-2012, 06:55 PM
If you build something that demands quite a bit of discharge, you need to shut down the battery before it gets too low.

I accidentally left my RC transmitter on over night not long ago. The transmitter was being power by a 3-cell LiPo. When I noticed what I had done the next day, it was too late. One of the LiPo cells is now dead and wont take a charge.

I now use one of these (http://www.hobbyking.com/hobbyking/store/__18987__On_Board_Lipoly_Low_Voltage_Alarm_2s_4s_. html)on any LiPo pack I have plugged into anything.

93955

These are very loud so I'll should hear it from anywhere in the house. I think it's loud enough to wake me up.

They only cost $1.92. Hopefully, they'll keep me from ruining any more LiPo cells.

I also like to use the battery monitor erco had sent me.

93956

Since receiving erco's gift, I've purchased several more.

The picture is of the HobbyKing version (http://www.hobbyking.com/hobbyking/store/__6589__Battery_Monitor_2_6S.html). They're not as cool as the red PCB version erco sent me, but they work fine and are cheap ($1.96) (I think they're even less expensive from ebay).

erco
07-04-2012, 06:55 PM
I just sent a nice "thank you" email to the seller. :)

Loopy Byteloose
07-04-2012, 06:57 PM
The term 'fake' did not make it clear, but no harm done. I jumped to a conclusion and apologize if I offended anyone, including the vendor.

These are NOT exactly the same length as AA cells and may not fit in the battery holder if you are attempting to just replace conventional AA cells with half as many Lithium. I have had to work hard to squeeze then in a normal AA holder and I have yet to see a special holder just for them.

Duane Degn
07-04-2012, 07:27 PM
The term 'fake' did not make it clear, but no harm done. I jumped to a conclusion and apologize if I offended anyone, including the vendor.

These are NOT exactly the same length as AA cells and may not fit in the battery holder if you are attempting to just replace conventional AA cells with half as many Lithium. I have had to work hard to squeeze then in a normal AA holder and I have yet to see a special holder just for them.

No offence here.

I hadn't noticed the extra length on these cells. You're right they are longer than other AA cells.

I grabbed a few cells I had near by and measured them.

Here are the results:


Brand & Chemistry Diameter Length
___________________________________
UltraFire Li-Ion 14.1mm 50.7mm
Kirkland Alkaline 14.1mm 50.3mm
Energizer Alkaline 14.1mm 50.1mm
Energizer NiMH 14.2mm 50.2mm
Duracell NiMH 14.2mm 50.2mm
eneloop NiMH 14.2mm 50.2mm
cooloop shunt 14.0mm 49.9mm

These Li-Ion cells are about half a millimeter longer than most of the other AA cells I measured.

I've previously noticed how many rechargable batteries are a little wider than alkaline cells. I have an 8-cell holder that fits inside my RC transmitter when the holder is full of alkaline cells but it doesn't fit when I use recharable cells.

I hope the extra length of these Li-Ion cells doesn't cause too much trouble for those of us using them with normal AA holders.

Thanks for the heads up about it.

erco
07-04-2012, 07:36 PM
Duane: Didja get some mad July 4 sparkz when you put your metal calipers across the batteries? :)

Duane Degn
07-04-2012, 08:15 PM
Duane: Didja get some mad July 4 sparkz when you put your metal calipers across the batteries? :)

I'm insulted, you think I'd be so dumb.

I only used metal calipers on the first battery. After that,

I used a set of plastic calipers to measure the batteries.

And yes, I did get some pretty good sparks.:tongue:

Loopy Byteloose
07-04-2012, 09:48 PM
So the shunts are true AA, I had suspected that as they have been around for ages.

I have been looking into shut off circuitry for a low voltage and apparently a MOSfet can be controlled by a good reference voltage and a voltage divider circuit to do the job. But it also seems many of the battery vendors have boards that do the same thing rather cheaply.

See RSJC in the thread linked to below for what I suspect is a best circuit.
http://www.eevblog.com/forum/projects-designs-and-technical-stuff/li-ion-battery-low-voltage-cut-off-circuit-needed-for-project/

Publison
07-04-2012, 10:06 PM
What are you guys using for chargers?

erco
07-05-2012, 03:07 AM
I have two like this for individual charging. A pain to R&R cells, but cheap and in charges all sizes. http://www.ebay.com/itm/New-RCR123A-Lithium-Li-ion-NI-MH-AA-AAA-18650-14500-Intelligent-Battery-Charger-/251097680215?pt=Battery_Chargers&hash=item3a76968957

Duane Degn
07-05-2012, 04:30 AM
What are you guys using for chargers?

After reading this artcle (http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries), I've decided it should be safe to use my LiPo charger to charge Li-Ion cells. I think these Li-Ion cells should probably be charged at a lower current than the usual 1C. The article says they should be charged at 0.8C or less.

I'll probably use .6C for these batteries. 0.6 * 1200mA = 720mA. So I'll set my charger to 720mA charge current.

Loopy Byteloose
07-05-2012, 11:02 AM
I use a charger for both 14500s and 18650s that is sold in Taiwan. It takes two cells at a time.

In theory a LiFEPO4 charget should work with the LiMnO2 chemistry of what you term "Lithium Ion" charger, but you would definitively get less of a charge. Peak charge will be to something like 3.9V rather than 4.2V. The rate of charge may be slower as well.

Parallax's 18650 is a charger and battery holder system. That simplifies battery management as I still haven't build anything to shut down a low battery. I would hate to waste good new Lithium batteries by an over-discharge on the first round of use.

In some cases, the microcontroller can monitor and shut down the battery, but not always.

Duane Degn
07-05-2012, 05:27 PM
I would hate to waste good new Lithium batteries by an over-discharge on the first round of use.

In some cases, the microcontroller can monitor and shut down the battery, but not always.

Make sure and check out the battery minder I mentioned in post #21. It makes a very loud sound if one of the cells drops below a set voltage. I doubt it would work well with LiFePO4 cells or other cells that are not in the correct voltage range.

For something that costs less than $2, it could save a person a lot of money from ruined batteries.

Loopy Byteloose
07-05-2012, 07:12 PM
I have been digging. I finally located my 14500 cells that I purchased near the start of the thread. They happen to be 1200ma at 3.7V and after all this time are still over 4.0 volts. I have wanted to use these with my SXchips as they will tolerate variable voltage as long as I don't clock to fast and have the brownout shut down set low or off.

Also, I have been digging and digging for low voltage cutout circuits, but mostly were ones for 12 volt gel cels and such. They often suggested a comparitor or an op amp. That is way too complex.

But I finally found a set up that is a couple of transistors and one Mosfet on an r/c airplane site. That looks exactly like what I want. I will have to build a proto-type and test its shutdown, but the main thing is it is all easy to get components and with a 2N7000 it would only be for about 200ma of power. But with bigger MOSfets, one can use it for nearly any size Lithium battery pack.

Now I am trying to figure out if there is a low power MOSfet out there that is similar to the 2n7000, but with substantially less Rds than 1 ohm at 4.5V. By inserting it, I am wasting about 3-4ma.

Lawson
07-05-2012, 10:56 PM
For a low voltage cut out, I'd use a MN1381 (http://www.digikey.com/product-detail/en/MN13812SGU/MN13812SGUCT-ND/1465105) ( or here (http://www.solarbotics.com/product/1381/) ) driving a N-channel Fet in the ground connection to the load. Other power supervisor chips should work as well. Through-hole I'd suggest a IRLD014PBF-ND (http://www.digikey.com/product-detail/en/IRLD014PBF/IRLD014PBF-ND/812481) FET. If you're willing to use surface mount parts, 568-6540-1-ND (http://www.digikey.com/product-detail/en/PMV56XN,215/568-6540-1-ND/2531827?cur=USD) works well for a "slow" switching application like this.

Lawson

Loopy Byteloose
07-06-2012, 10:08 AM
Thanks, that first chip looks fine at 35 cents each, but I'd have to buy a reel of 3000. So, it I need just one, it is $1000USD; if I need 3000, they are 35cents each.

The second one is 92 cents in single quantity, plus shipping. But they seem to want to sell 2500 or more. And so it goes.....

Since I suspect that part availability is going to cloud the issue, I am trying to DIY a differential amplifier that can be built with easy to get components. But I will add these items to my shopping list for when I visit a local parts house. They are quite used to telling me "Don't have it. Never heard of it."

I used to spend a lot of time locating the best part, and then finding out I couldn't get it in single quantities. My projects tend to be single production items.

Christoph_H
07-06-2012, 01:46 PM
Thanks, that first chip looks fine at 35 cents each, but I'd have to buy a reel of 3000. So, it I need just one, it is $1000USD
I'm pretty sure Digikey will sell you the MN13812SGUCT-ND in single piece quantities. At least that's what the price table says. So if you need one you'll pay 94c (plus shipping).

If shipping cost is a problem RS Components (http://taiwan01.rs-online.com) could be an option. It looks like they offer free shipping in Taiwan.
Search for "Voltage Supervisory" on their site - minimum quantities per part are usually 5 or 10.
.

Tracy Allen
07-06-2012, 05:25 PM
I'd posted a circuit (http://emesystems.com/BS2power.htm#oscillator) using the MN13812 as a battery cutoff for the Basic Stamp. I bring that up to follow up on Lawson's comments, because it took me three extra resistors to set the threshold and hysteresis, and a capacitor for stability.
93993

The LP701 in the circuit is a lateral p-channel fet. There are more up-to-date parts that would be better in the same circuit--The MN13xxx series is listed as obsolete. My favorite mosfet for low power shutoff (up to a couple hundred mA) is the FDN304, with 70mΩ at 2.5V Vgs. Look up "trenchFET" or "powerTrench" for logic level mosfets in a large range of ratings & packages from Fairchild, Siliconix, Vishay and others.

For small lithium-poly cells (<1Ah) in my micropower data loggers, I'm using the LTC4071 as a combined charger and battery cutoff protection switch. It's an unusual parallel charger circuit meant primarily for energy harvesting or backup applications.

Loopy Byteloose
07-06-2012, 06:08 PM
@Tracy Allen
Thank you, a schematic makes it all the more useful for everyone. I think there is another device, a TL431 - Programmable Shunt Regulator, that will do the job.

I'll have to do some local shopping as it just isn't worthwhile to pay shipping to Taiwan for anything these days unless it is a big order. And tonight, I will tuck into bed with a bit of review of BJT differential amplifiers in the context of a Low Voltage Cutoff. The part count for that is not much more than for your schematic. I am wondering if I can get a LP0701P or FDN304 Mosfet as well.

And @ Lawson, thank you as well.

I still need to adapt this to a single 3.7V LiFePO4 cell, or two at 7.4V with precise cutoff voltage. My 14500 is 3.7V and rated at 1.2AH, but I have seen some with odd fittings welded to the ends that go as high as 2.4AH. Maybe Tracy would find these useful.

There is lots more to come in Lithium rechargable batteries now that we have several generic sizes and shapes. It is tempting to throw out all my NiCads and NiMh as it take two or three to provide similar capacity, AND they are more temperamental in some ways.

Lawson
07-06-2012, 06:56 PM
If you're planning on experimenting with differential configuration circuits, I'd skip strait to an op amp or comparator with a <1uA idle current. For instance the MCP6141 (http://www.digikey.com/product-detail/en/MCP6141T-E%2FOT/MCP6141T-E%2FOTCT-ND/1963698) also available in a DIP package (http://www.digikey.com/product-detail/en/MCP6141-I%2FP/MCP6141-I%2FP-ND/509483) if you can find them. (MCP6541 for the comparator version) Ti, Linear, etc. have similar parts if you local distributor doesn't stock Microchip parts. The biggest bit I haven't found is an inexpensive voltage reference with a similar ~1uA idle current under all circumstances. A 1.2v MCP1700 regulator gets close, but my testing of higher output voltage parts indicates it'll draw >10uA if the supply voltage drops below 1.2v. (not a big deal with battery power, but a pain running from super-caps and solar)

I agree that the MN1381 isn't particularly accurate. It's also reaching end of life. I suggested it because it still has one of the lowest idle currents I can find, and is a good place to start looking for newer chips.

Lawson

erco
07-06-2012, 07:08 PM
Is there ANYTHING that Tracy Allen doesn't know about? :)

A big shoutout to one of the most knowledgable and helpful forumistas ever. I met him briefly at Expo in April and he's not only smart, but a very personable and likeable fellow as well. I hope our paths cross again soon.

Loopy Byteloose
07-06-2012, 07:08 PM
I found the 1381 chip and Maxims 8212 at Solarbotics in single quantities. And most embarrassingly, the reason I looked there was because it occurred to me that I have one or two 1381s on hand for a BEAM project that never got done.

@ Lawson

My impression was that having a power supply that was dropping down to as low as 2.5VDC might play havoc with all but very special op amps. So I became interested in the discrete component differential amp solution. That MCP6141 looks perfect as I only need a comparitor and it will power at 1.4volts.

And now, having read an introduction that claims you are nobody in electronics if you don't comprehend differential amplifier design, I am wanting to dig into this for knowledge's sake.

Even if I build the differential amp version, it is going to consume much more power than either of these chips. So it is just an academic exercise and learning experience.

@Tracy.

There are some 'half-sized' 3V Lithium batteries, the 16555s which will fit two in one 18500 battery holder. These total 6V, not 7.2V at nominal operation. They might be more useful to you than the 14500s, which I hope to one day use to power a Propeller.

erco
07-07-2012, 10:04 PM
A closer look at the shunt batteries and the keen-o storage boxes sent for free by the seller.

Now who wouldn't like to have those? :)

Duane Degn
07-07-2012, 11:06 PM
Now who wouldn't like to have those?

Amen, Brother.

I thought maybe the original description on ebay said the batteries included battery holders and the battery holders were just sent late. After checking the original listing I don't see any mention of battery holders so these (and the shunts) where just gifts (and nice ones too). Kind of an amazing seller to go this far out of his way.

Choirboy Duane

erco
07-07-2012, 11:11 PM
All I can figure is that some nogginhead used 'em like 1.5V AAs and complained when some magic smoke got released and the seller did a proactive, preemptive mailing to avoid more complaints from other Americans with room temperature IQs. :)

Loopy Byteloose
07-08-2012, 09:26 AM
Room temperature IQs? Would that be Fahrenheit or Centigrade? Or does it matter to you?

It is NOT easy to use these like AA cells as they are .5mm longer. I had to force two of them into an AA battery holder. I am happy that I can though as it seems that no one is making something else for them.

Two of these in series are great for the BS2 as you have a voltage regulator to adjust the use. And Pololu sells tiny voltage switching regulators if the linear are too wasteful for you.

I have made a bit of progress with my low voltage cut off. I am abandoning the discrete transistor differential amplifier approach and looking at a LOW Voltage comparator chip - the LMV331 for use with ONE cell (not the LM331 which requires 5 volts power and is a voltage to freq pulse chip). This chip drains less power than anything I could build myself.

One can use the TL331 (single package) or 1/4th of the LM339 (quad package) if you are using two batteries in series as it would cut out before ever reaching 5volts. I still have to bench test something before posting. I've been hung up with another project using SLEEP in the SX28 chips and the Watchdog Timer. So please be patient.