Li-Ion chargers with voltmeter?

OK, so I was just looking through newer threads, read this one and as result I bought for 4 dollars each one voltmeter and one multimeter from ebay to see how those ultimate budgetgimmicks work. So far this thread cost me 7 bucks, argh!^^

http://www.ebay.com/itm/140734934068?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

http://www.ebay.com/itm/220626725000?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Doesnt the ML-102 even uses exactly same IC as cottonpickers chargers?

ML-102 uses 2x TP4057

Just remember that panel meter needs an input voltage of 4.5-28v, so you won't be able to power it off a single cell (but you can power it off the PSU)

+1, agree 100% Viktor

I saw cottonpickers, thought it was pricy, then looked into making my own and realized the work that goes into those things. I'm still going to try making my own, because I'll learn in the process... but I'll only save a couple bucks at best... and I'll lose hours upon hours of time.

I'll post back here in a few with links to some of the components I sourced for a small USB sized charger, there's a few board options, etc.

Here are some of the components I've sourced for making this little project.

TINY 1a 5v USB charging board. you can adjust the charging current by changing the tiny resister on the -DC input side. I'm honestly not sure my soldering skills are up to the task, but I'm going to try!!! I have a couple on order currently.
http://www.ebay.com/itm/330699360128

SAME board, better pics in the listing, but 2x the $$
http://www.ebay.com/itm/130675830179


Bear in mind those are mini-usb plugs, you'll need to add on another 1$ for a mini to usb A cable like these:
http://www.ebay.com/itm/270822565407
http://www.ebay.com/itm/110653003088


OTHER small charging boards. Some more expensive or less featured, but worth taking a look.

http://www.ebay.com/itm/270958278638 - 5v input, 1a rated, same TP4056 IC, no USB port wired in, no LED wired in. Board is a slightly different size. Twice the $$ ... looks like it would be good for a DIY integration project, not so good for plug-n-play.

http://www.ebay.com/itm/160782678020 - 1.5a rated, 5.8-6v (but recommends 6v), almost the same board design as the one mentioned above, except this time its running TWO TP4056 IC's (still one output) and what looks like dual 1.6k resistors. Item description however is identical to much of the info from the original board, and doesn't seem to apply correctly to the new dual IC 1.5a designed board. going by the resistor tables, 1.6k would = ~750ma on a single IC, so it stands to reason that one each would = ~1.5a .... I don't know, anyone have thoughts on this one? Double the price at $6.... but tempting to get one to play around with. NOTE that it's 5.8v-6v input, so NOT a USB charger without a boost circuit first.
http://www.ebay.com/itm/150795982222 from the same seller provides a much better detailed and clear picture of the board components.

http://www.ebay.com/itm/120898714536 - full size USB plug on it, board size looks to be quite a bit smaller.... but the picture is too small/blurry to see what kind of IC its using or any of its circuit designs... sold in pairs for $12 after shipping, so kind of an expensive experiment :/


REMEMBER, most USB 2.0 plugs are only rated to supply about 500ma. In most cases if you plug a 1A charger into the plug, it will just be fed 500ma, no harm done to anything. occasionally with some of the older USB 2.0 plugs, it would shut off the port if it detected too much current draw - power cycling the computer was sometimes required to reset the port protection switch.... but that's rare these days, I havn't seen that in recent years. USB 3.0 ports are rated for 900ma and many times will provide more than that.


Voltmeter panels: I am waiting on these two to arrive: Downside, it doesn't show below 3.2v, upside is that it will power directly off the battery for portable "checker".

http://www.ebay.com/itm/180861130625

http://www.ebay.com/itm/140741006932

One of these 1-6s lipo meters posted earlier in the thread looks like it would work really well for being powered off the battery directly, and could also be used in a multibay charger mod extravaganza http://www.ebay.com/itm/330702194021

If you want to power the panel off the charger, then this one, also posted earlier in the thread, looks to be good: http://www.ebay.com/itm/140734934068


Ultimate goal of the whole project? Well, this is BLF, and for me, that means anything I build has got to be used by me in the real world. I EDC (and use) lights every day with 10440, 14500, and 17670 batteries. I'd like to build a few units both with and without displays, cover them in shrink tubing, and sprinkle em around my environment (car, office, pack) which could then be used to top up a battery if it was getting used much that day.

Units without a display are very small and could go unnoticed in many places. Units with a display could be very handy for checking the voltage on a battery during the day. Lastly, I've thought about just wiring up a display in some shrink tubing separate from the charger and use that as a portable checker.

I've also thought about mounting one in a junk single bay adjustable charger I've got and incorporating a slider switch to select the resister & charging current from 90ma to 1a. Again assuming I can solder that small :)

Some little magnet leads are also a must have, but easy to produce.

VERY good job researching, spectrrr!

/me *tips hat*

Now, THAT is what this forum is all about.

Viktor

Here is a more budget version, with voltage range better suited for our application:

Battery Voltage Indicator Checker Tester 2.8V -25.2V

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330702194021

Viktor

This thread seems to mirror one on the other forum, more good info here

Same version voltmeter as spectrrr's, but $1.50:

http://www.ebay.com/itm/261009249991

Edit:

Scratch that, it's an auction.

question:

If I get this 1s-6s voltmeter display, can it be wired in parallel with the charger? or does the charging circuit have to be disconnected/switched-off to use this display?

example: incorporating OP's idea, can this 1s-6s voltmeter (link $2.88) be soldered/connected permanently to this microUSB charger (link $3.40) or something like this Universal Charger (link $2) while charging?

I suppose if it is soldered-on, it will always show ~4.2V during charging, and actual battery voltage only when you disconnect the power? this way, one could avoid adding a 3-position on/off swich (link $1) to the voltmeter display. Similar to the setup of Ledoman (link), except his setup is only a display, not a charger. Cottonpicker on CPF's ForSale item has a switch, though I don't know if it is to toggle between Voltmeter Display VS Charging.

related ebay pictures:

I hae the same ? as AAx3. I ordered a 1s-6s & 2s-6s. I would like to use it with my UF WF-139.

I don't have any experience with using those - hopefully someone else more knowledgeable will chime in.

woohoo, got one of the charging boards and one voltmeter in the mail today.

http://www.ebay.com/itm/330699360128

http://www.ebay.com/itm/140741006932

voltmeter looks good. only single digit precision however. So 4.09v on the multimeter reads 4.0v on the voltmeter. Not a huge deal, but if your charger only sends it to 4.19v for example, you'll have a tough time seeing when it kicks over to CV charging. Still, it will make a great compact battery tester or it will integrate nicely with the USB charger. Size wise they are both very similar. One is 3mm fatter, the other is 1mm longer. Almost the same.

that resister is freaking TINY on the USB board... this is going to seriously challenge my soldering skills :)

More voltmeter's on the way, we'll see how they behave....

I'll be pretty busy this month... not sure when I'll have time to really dig into this....

You can use one 1S voltmeter per charging bay, in parallel with the charger contacts.

It will not display constant 4.2V, but rather the actual (at-the-moment) cell voltage, while charging.

2S or more voltmeters are useless for monitoring separate bay charging progress, but are good for monitoring cells connected in series and balanced charging setups.

Viktor

UPDATE:

I'm beginning to not like this voltmeter... http://www.ebay.com/itm/140741006932

Earlier I measured the voltage - The battery was at 4.05v, the voltmeter said 4.0v ... ok, no problem.

Now I put the battery on the charger and charged it for a couple hours to 4.17v (that's full for this cheapo battery). Checked it with the voltmeter - STILL reading 4.0v - NOT COOL!!!

UPDATE #2

I fixed the off-kilter readings on the voltmeter (I think). There's a small calibration screw on the back. plug in a known voltage and adjust it till it reads right.

This one has two decimal precision, and I think it's more accurate than my cheap multimeter:

http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=330702194021#ht_4380wt_1041

It's also cheaper, does not require separate power supply, but can measure from 2.8V upward, powered from the cell itself.

Viktor

I've got one of those coming, hopefully arriving in a week or two :)

I already got one, and it looks to be quite good.

I've had it connected while charging a keygos 26650 on the charger that came with ma M10, and it terminated spot on at 4.20V. My cheap DMM did state that's 4.23V, so I'm starting to trust the charger and this small voltmeter over my DMM.

Viktor

Just got this one in the mail today: http://www.ebay.com/itm/180861130625

I really like it... display the decimals out to two spots, showing my battery at 4.11v, spot on agreement with both my DMMs. Only downside is that it's not adjustable, there's no way to tune the reading... but in this case it doesn't matter, it's spot on. Def my favorite so far.

A note on voltage readings - my cheap DMM has two settings. a normal DC V setting, and a DC V 1.5v Battery setting. A lion battery of mine reads 4.11v on all three meters... BUT the 1.5v battery setting reads it at 4.14v... My expensive meter agrees with the 4.11v reading... might want to check your meter Viktor and see if you've got a low volt battery setting like that... would explain why it was reading 4.23v.

One charger ends at 4,09V, other at 4,13V. Bad...