Standby/Topping Smart Charger

[lunaras]

I am quite familiar with li-ion safe charging procedures, so I know trickle charging li-ions is quite bad. However, I'd like to get a charger that can keep my batteries well charged when I may not use them for extended periods of time. Can anyone recommend a charger that will charge li-ions up to, say, 4.05V and then when the battery self discharges to 4.00V, it tops it back up to 4.05V? I've heard there are chargers that will do something like this, but I can't seem to find them.

 

[Trevtrain]

Hi lunaras

I don't think I've ever seen a charger that will do this but other more experienced members may be able to recommend a "hobby charger" that might be able to be configured this way.

Cottonpickers chargers over at CPF Marketplace will kick in again once the voltage drops below a certain point I think, but they don't terminate at 4.05V.

Having thrown that out there......

Since Li-Ions have a fairly low self-discharge rate, why would you want to bother trying to keep the cells topped up to 4.05V anyway? The higher the voltage they are stored at the faster they deteriorate and decline in capacity, especially if stored in high summer temperatures. By storing unused cells at a high voltage you will gradually degrade them.
Most sources recommend about a 40% charge in cool ambient temperatures as being optimal for storage.
Have a look at http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

I guess it depends on how soon you think you might need ready access, but I'd be inclined to just charge and store (or discharge to 40% and store) any cells you don't plan on using right away. (ie. Your "extended periods of time".)

When you want to take that camping trip or night hike, just plan a day or two in advance to top them off.

If you are thinking Zombie Apocolypse (which seems to be a popular and frequent discussion point in here :shrug:), hurricane or other emergency scenarios, then you probably should have a light and some primaries stashed in an emergency kit anyway.

 

[lunaras]

The li-ion cells I've been using have sometimes failed completely after 1-6 months of non-use and if I don't use them within around of month of charging them, I usually find them rather drained. This has been true of my first li-ion purchase which consisted of Trustfire and Tenergy cells as well as my current AW IMR cells. I only use protected cells, I don't overdischarge, I've checked the batteries after being charged and they're consistently 4.17-4.20V, and when they're not being used, they're stored in a climate controlled room at around 68-74*F or so.

The reason I'd like the charger is both a matter of convenience and preparedness. This charger is intended for a large, bright 3x18650 light that will mostly be used when camping, but I'd like to keep it mostly charged and available to use if the need arises. Living in Wisconsin, I don't camp in the winter (hell, getting my wife to go in the summer is hard enough), nor do we tend to have power outages during the winter, but it does happen from time to time. So, ideally, I'd like to be able to drop the cells in the charger in October, walk away and not have to worry about them if I don't use the light until May. That way if we do have a power outage, I can use my EDC to get me to my charger, drop them in the monster light, and use that, as it's a much better, brighter light than my EDC or emergency kit lights that I can ceiling bounce and light my entire home.

 

[Knight_Light]

The li-ion cells I've been using have sometimes failed completely after 1-6 months of non-use and if I don't use them within around of month of charging them, I usually find them rather drained. This has been true of my first li-ion purchase which consisted of Trustfire and Tenergy cells as well as my current AW IMR cells. I only use protected cells, I don't overdischarge, I've checked the batteries after being charged and they're consistently 4.17-4.20V, and when they're not being used, they're stored in a climate controlled room at around 68-74*F or so.

The reason I'd like the charger is both a matter of convenience and preparedness. This charger is intended for a large, bright 3x18650 light that will mostly be used when camping, but I'd like to keep it mostly charged and available to use if the need arises. Living in Wisconsin, I don't camp in the winter (hell, getting my wife to go in the summer is hard enough), nor do we tend to have power outages during the winter, but it does happen from time to time. So, ideally, I'd like to be able to drop the cells in the charger in October, walk away and not have to worry about them if I don't use the light until May. That way if we do have a power outage, I can use my EDC to get me to my charger, drop them in the monster light, and use that, as it's a much better, brighter light than my EDC or emergency kit lights that I can ceiling bounce and light my entire home.

In theory you can probably either find such a charger or make such a charger and you would be okay except for the fact that you would shorten the lifespan of the battery (in terms of charge discharge cycles). In reality leaving lithium ions in a charger unattended for months on end is a recipe for disaster. Because if the charger malfunctions you will have a greater disaster then the one you are trying to prepare for. Just my two cents.

 

[HKJ]

if I don't use them within around of month of charging them, I usually find them rather drained.

This is uncommon, usual I do not need to charge LiIon batteries, that have been unused for a year or more.
How warm is it where you store your batteries?

 

[Trevtrain]

I'm sorry to say it, but usually any cell with the word "fire" in the name is suspect from the outset. They may be old cells, laptop pulls, fakes, etc and are usually labelled with capacity claims well above their actual ability. These would be the last flavour of cells I'd be wanting to leave in a charger quite frankly. +1 to Knight_Light's comment.

Tenergy I'm not so sure about but I'm pretty sure HKJ has tested some of these and you could probably find links to the results. Personally, I'd just go with Panasonic or Sanyo based cells from somewhere like Fasttech - very affordable.

Like HKJ, I don't know how your AW cells would be self-discharging; that really doesn't sound right? :confused:

When you say you measure between 4.17V and 4.20V after charging, is this immediately out of the charger? I read that a better way of determining the health of your cells is to measure them at 1 hour and 12 hours after charge. If they have dropped below 4.10V in a day, they are probably due for replacement.

Storage at 72F (25C) is not excessive but some loss of capacity is unavoidable. (Refer to the link in post #2)

Really, I think you might be best to just get two sets of cells and charge them to about 4.00V-4.10V. Top them off for planned trips and be happy that they will have enough charge to get you through any unplanned outages. Set a reminder in your diary to check them every couple of months if you really want.

At the risk of getting of topic, have you considered lights such as the newer 4/8*AA offerings from Nitecore, Fenix or Sunwayman? Whilst maybe not equivalent to the "monster" output from your 3*18650 light, they do have pretty impressive output and will easily light up a room with ceiling bounce. Eneloops are cheap (especially in the USA) and don't suffer much loss in storage. I know you probably weren't thinking of buying a whole new system but I'm just throwing it out there as something to consider for your outage scenario. :whistle:

 

[lunaras]

The safety issue for leaving them in the charger is why I'd prefer to purchase a charger rather than build one. I have the technical skills and theoretical knowledge to build it, but I'm also smart enough to realize that I'm not an expert in this area. Given the potential consequences, this is one time I'd rather leave it to the experts with a QC department.


I charge and store my cells in a corner in my living room. I'd prefer them on a fireproof table/shelf sitting on a concrete floor, but living in an apartment with no garage or basement, I take what I can get and keep them where they are visible in case of a problem. Ambient temps run from about 65-80 throughout the year, but most of the time it's below 70.


Yeah, I agree, the TrustFire and Tenergy cells were from before I knew better and I wouldn't purchase them again in the future. Half those cells died within about 6 months of purchase and after not using them for around 3 months, I couldn't recharge any of them. I suspect they self discharged to the point that the protection circuit wouldn't allow them to be recharged again. The AW cells I have are 2.5-3 years old and I've been quite happy with their performance. I recharge them about every day or two as I'm an e-cig user, so these cells get a heavy workout daily (intermittent 3-4C discharge periods, throughout the day). After 500-750 nearly full charge/discharge cycles, they're probably getting ready to retire (in fact the first to die only did so a couple weeks back), so maybe their inability to hold a charge long-term is just a symptom of their age. I'm planning on ordering protected Panasonic cells for this light.


I'm just getting started with high performance lights, so I'll actually be getting a whole new system, assuming I don't use one of the chargers I currently have. The EDC I ordered I'm building will run on 1*CR123s, 1*14500, or 1/2*AAs. The lights I'm planning on including in the emergency kits I'm building will be taking 1*CR123s, 1*14500, or 1*AAs (or even 1*10440 or 1*AAA with adapters I'm including in the kit in case it's necessary) and I'll have a dozen or two CR123s stashed with them. So, I'm thinking I'm hopefully pretty well covered for actual emergencies without the 3*18650 light. Although it will certainly have it's uses, it will not be used nearly as often as the EDC and I don't want self discharge to kill otherwise perfectly good cells; hence the desire for being able to keep them relatively charged if possible. Hell, if necessary, I'm fine keeping them charged at around 3.0-3.5V to prevents the protection circuit from kicking in if that's my only option.


I considered the Caveman for my wife, who wants a standard alkaline flashlight so she doesn't have to mess with recharging anything, so I have at least a passing familiarity with them. I'm hoping to be able to convince her on using Eneloop AA rechargeables since they're less fiddly and safer than li-ions. But so far, no luck. She likes the 2C Mag she used to have and wants a direct replacement. I've at least convinced her to get the LED model, but that's it.


As far as I know, maybe this whole thing is a moot point since it sounds like using the higher quality Panasonic cells, may reduce the self discharge to the point where they'll be, say, 75% full after 6 months. I'd be fine with that as it'd be usable on short notice and as you said if I am planing on using it, I can always top them off before doing so. The unplanned usage is the only part that concerns me in the least.

I guess if it comes down to it, I can rig up some electronics to control a relay that turns on power to a charger once every month or so or something like that.


As an aside, does anyone make 3.0V or preferably 3.7V primaries in a 18650 form factor? That'd completely eliminate any need for any sort of standby charging on my li-ions.

Sorry for the wall of text. :)

 

[HKJ]

I did just checked a couple of 2½ year old batteries, that has not been used or charged since (From my 2011 battery test), most of them where around 4 volt.

 

[Knight_Light]

I did just checked a couple of 2½ year old batteries, that has not been used or charged since (From my 2011 battery test), most of them where around 4 volt.

Shame on you for not storing your batteries at 40% SOC. ;)

 

[lunaras]

HKJ, are you aware if any particular brands seem to hold their charge better than others, or do all high quality cells seem to fare well?

 

[HKJ]

Shame on you for not storing your batteries at 40% SOC. ;)

That means they have suffered a larger permanent capacity loss, than they would have if stored properly. I am also storing them at 25 degrees Celsius, that does also increase the ageing rate.

I did at one time store my batteries in a drawer in the fridge, but I stopped that after a problem with the fridge, where the drawers got flooded. :(

 

[HKJ]

HKJ, are you aware if any particular brands seem to hold their charge better than others, or do all high quality cells seem to fare well?

No, even some of the cheaper brands did keep their charge.

 

[lunaras]

I guess my TrustFires and Tenergys were rather sub-par then. Not surprising I guess, but it's good to know that I really don't need to worry too much about not charging decent batteries for a while.

Thanks for the info!

 

[Knight_Light]

That means they have suffered a larger permanent capacity loss, than they would have if stored properly. I am also storing them at 25 degrees Celsius, that does also increase the ageing rate.

I did at one time store my batteries in a drawer in the fridge, but I stopped that after a problem with the fridge, where the drawers got flooded. :(

I was just teasing you. :) It is a PITA to actually maintain batteries under proper circumstances. Plus from reading all of your reviews you probably have enough batteries to last a lifetime. :)

 

[HKJ]

I was just teasing you. :)

I know.

It is a PITA to actually maintain batteries under proper circumstances.

I do not really worry about lifetime on the batteries, I want most of my batteries ready to use.

Plus from reading all of your reviews you probably have enough batteries to last a lifetime. :)

I do not use many of the review batteries, mostly I buy Panasonic 3100 and 3400 for use.
And I do hope to last longer than the batteries (Remember the limited lifespan of LiIon) :).

 

[Knight_Light]

The safety issue for leaving them in the charger is why I'd prefer to purchase a charger rather than build one. I have the technical skills and theoretical knowledge to build it, but I'm also smart enough to realize that I'm not an expert in this area. Given the potential consequences, this is one time I'd rather leave it to the experts with a QC department.


I charge and store my cells in a corner in my living room. I'd prefer them on a fireproof table/shelf sitting on a concrete floor, but living in an apartment with no garage or basement, I take what I can get and keep them where they are visible in case of a problem. Ambient temps run from about 65-80 throughout the year, but most of the time it's below 70.

The point I was making is that it’s just a bad idea to leave lithium batteries unattended while charging let alone for months on end. So unless you’re going to sit there for three months straight watching these batteries charge it’s not a good idea. I understand your point of checking up on them periodically and in theory you would be fine. But like all electronics there is always a possibility of something failing. And if you’re charger responsible for this process goes and you are unaware of it you can have some serious consequences.

 

[Knight_Light]

I do not really worry about lifetime on the batteries, I want most of my batteries ready to use.

I am totally with you on this one. Especially since you can get good quality Panasonic’s for about eight bucks apiece.