I'm taking a shot that there must be something out there to accomplish my mission.

It's December and my bike is put away until I start commuting to work again in the Spring. I have two powerful CygoLites and a Bem speaker that are packed away, as well. I know these things need to maintain some level of charge over the winter, and I know I have too many things going on to remember to put them on a charger every few weeks or months. So...

I am looking for some type of device to which I can attach these three pieces of gear and leave them plugged in until I am ready to use them again. Some sort of very slow trickle charge device that will automatically shut off when the batteries are charged and turn on again when they reach a certain low level.

PLEASE do not bombard me with questions or comments about why I don't ride through the winter or why I can't just remember to charge the batteries manually a few times over the next few months. I might have to kill you if you do.

Thank you.

they have them for cars... trickle chargers..

What kind of batteries? NiCd, NiMH, Li? Removable (AA, AAA), or wired into the devices?

That would be for starting batteries with lead acid chemistry, which are sensitive to deep discharge (i.e. more than 50%).

The discharge rate of NiCad is 10%/month, Lithium is half that. Unless storage extends for more than a year or so, there should be little or no need to charge the batteries.

I store my NiMH and Li Ion batteries in the fridge when not in use. They discharge much slower that way. I have had Li Ion computer batteries that were still almost fully charged a year after I took them out of the fridge.

If you do that, put them in plastic bag so they do not get any condensation when you take them out later. Let them warm up before doing anything with them. Also Li Ion batteries are not supposed to be charged when cold, but I do not know how cold, if you are curious you could do a google search.

If you can put a voltage meter on the battery, you could check them every month or two to see if they need to be topped up. But if they are internal to your device, then maybe you would just need to top them up on occasion.

solar chargers are pretty useless on tours because you are moving. maybe left in a winter southern window they would work .

Chances are, these devices use LiIon batteries. The thing you want is not necessary. Firstly, these batteries are fantastic at holding charges over long periods. I misplaced a battery for 18 months and just found it. It was 73% full, and I might not have charged it before losing it. Secondly, it's fairly harmless to leave it connected to its regular charger. This is because LiIon chargers are smarter than previous ones. They cut off voltage when the battery is charged.

I've read that it's better not to leave it 100% charged before disuse, but I don't know how true this is.

Yes, the Cygolite Metro 850 and the Cygolite Hotshot Micro 150 use Li-ion batteries. In the past, people have warned me about maintaining a certain amount of charge when not in use. Based on what I'm reading here, I think I will save my money. Thank you!

PS: My speaker is a BEM EXO200. I can't find info about the battery type. Would NiCad store the same way, for the same length of time?

Pick up a trickle charger at you local hardware, Harbor Freight.

It seems like all the trickle chargers out there are for automobiles and motorcycles and require hard-wiring. I thought there might be a common gadget that techies are using these days to keep batteries on USB-charged electronics sufficiently charged to withstand a break in the action. It seems I don't have to worry about that, though, according to many of the comments here.

Best way to store Li-Ion: Charge them to 50% and check them in 6 months. Leaving them fully charged will work but degrades life a little faster. Heat and higher voltage will degrade the batteries faster.

I see the speaker charges via USB, so I'll bet it's LiIon. These batteries have tons of advantages over the old types, and one of them is that you should use them in a way that's convenient for you without consideration for what's "good" for them. And no, NiCad don't store the same, but it doesn't matter.

I do not think anyone is using Ni Cads anymore. NiMH has pretty much replaced the Ni Cads, they have similar voltage range. As I noted above, I store my NiMH batteries (and Li Ion) in the fridge.

If it is NiMH, most of those discharge pretty quick - tens of percent of charge loss each month. But there are low discharge NiMH batteries (AA and AAA Eneloop is the most common one) that hold a charge for a long time. Ikea sells some low discharge AA and AAA NiMH batteries at a great price.

I have NiMH batteries that are over a decade old that I am still using, but some lower quality ones can be shot in less than a couple years. My old ones are not the low discharge ones, I am pretty close to taking them all to the recycle center and just using the low discharge Ikeas and Eneloops in the future.

Lithium batteries keep their voltage over many months, the discharge is very slow. So set it to a good partially discharged amount, and put it away. Keep it cool if possible.

This page, How to Prolong Lithium batteries,
says:Also, their chart shows that partial discharges are much better than full discharges -- there's way more charge cycles at partial discharges.

The link includes lots of charts of discharge amounts, temperature effects, and storage.

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I contacted Dinotte about battery storage for their lights.
From their Battery Care page:I didn't want to do this timing, so I emailed about optimal voltages.
A full charge is about 8.4 volts on this battery. (4.2v per cell)

They replied:I'm not sure what that second paragraph refers to...


So I stored the battery at 7.8v for maybe 6 months, and the final voltage only dropped slightly more.



~~~
I'm doing the same thing with my camera battery. I don't use the spare battery very often, so I keep it at an equivalent partial voltage, just charging it up if I expect to use both batteries in one day.

Same with cordless drill lithium batteries. Stored at partial charge.

This...
Lenovo follows this guideline by offering an option to charge Li-Ion batteries in their laptops to around 50% and maintain the charge there while plugged in. I've used that setting for five years with my low end Lenovo and the original battery is still good. The only drawback is I have to manually choose this setting again anytime I unplug or reboot the laptop, otherwise it defaults to Windows settings and fully charges the battery before switching to trickle charge.

Generally I try to keep my old Nikon dSLR EN-EL4 Li-Ion batteries partially charged in storage, although approaching 12-15 years old they're pretty much at the end of service life even when not used heavily anymore. The more recent Nikon and off-brand Li-Ion batteries seem to last much longer.

NiMH batteries don't seem to be picky about charging. The manufacturing quality matters more than anything else. I've had some NiMH AA batteries that lasted for years and others that failed within a year, even when used, charged and stored similarly. I'm not sure brand name is a good indicator of quality either. Some of my longest running AA NiMH batteries were sold under their manufacturer names, recognizable only within the industry, while those relabeled as Duracell, Ray-O-Vac, etc., didn't last long.

My light use is the opposite of yours; I use my MTB lights in winter and store them all summer. My battery packs are larger than the CygoLites but the technology/chemistry should be similar or identical.

I agree with the advice others have offered......my practice has been to charge the batteries to around 50% (as best as I can estimate) and put them in an airtight ziplock bag in the refrigerator. Doing this has kept my batteries somewhat diminished from new but still quite usable, for 8 years. That said, I don't venture out without a Fenix backup light in my pocket should things go wrong while I'm out in the dark woods.

BTW, welcome back.