Worlds Smallest Charger in the World with Built in Voltmeter
This is a combined voltmeter and li-ion charger in one with multple current levels to suit different sized li-ion cells.
Use it to quickly check li-ion battery voltages, and if low just plug it in to a usb socket to charge them -Its neat watching the voltage rise in real time plugged in to my laptop usb socket. The voltage meter will show voltages from 3v to 25v so is perfect to let you know when you've overdischarged a cell.
Note this is for 3.6v / 3.7v rechargable li-ion cells, not 3v rechargeables, primaries or nimh. Never leave cells charging unattended. If you don't know the dangers of li-ions cells and proper management please don't purchase.
The USB Charger is suitable for rechargeable 3.6v /3.7v li-ions that get charged up to 4.2v (The 4.35v CC/CV charger is Only suitable for specific cells of which there are only a couple : eg Samsung ICR18650-30A)
* It will taper the current as full voltage is reached. (so you get to 4v quite quickly, and a slower finish to the charge)
* CC/CV charging algorithm
* Uses a soft start for cells below 2.95v applying 10% current until 2.9v is reached.
See the graphs below for typical charging times, and how the charger typically operates:
What integrated circuit is inside these chargers? If it doesn't have a display it uses a Chinese TP4054. If it has a display I upgrade to the USA LTC4054. The 4.35v specialist charger uses a Microchip MCP73831
What range is the voltmeter good for? Range is between 2.8v & 14.6v
How accurate is the voltmeter? Its rated as accurate to +/-0.005v my tests agreed
What is the current draw of the voltmeter? Its about 10ma
Will my laptop deliver More than 500ma?: Many do, but I can't guarantee yours will. Ask for a 480 model if you are unsure or use a 'walwart' charger capable of the current you need else you risk going outside the spec of the port
Do I need to plug the charger in to see the voltage?: No
What happens if I connect the battery the wrong way around? Its important that you connect the charger the right way (red to positive) otherwise it will damage the charger
What happens if the two leads touch whilst plugged in? I suggest you connect the charger to the battery before plugging in, and unplug before removing the connectors. This then prevents you leaving it plugged in with no battery connected. If you leave the charging magnets connected together without a battery and leave it plugged in it will eventually break the charger. (accidentally letting them touch whilst plugged in doesn't immediately break it, but you should get into a good habit.)
What if I move the switch whilst charging. You can move the switch on the fly and it will move eg from 90ma to 320ma to 620 and back - If you do this on a small cell you risk damaging it by giving it too much current..
Is the cell fully charged when the display shows 4.2v? No, the charging algorithm means you'll see 4.2v or 4.21v on the display for quite some time before the cell is fully charged. See the graphs to see what you should expect to see on the display.
How do I know when its finished charging? There is a small secondary LED at the back that goes out. Of course you can stop the charging early if you wish by unplugging.
Can I use this with your solar panels? You can, but I recommend the 'Basic no display' version see here for reasons:
You use magnets to connect to the battery - Are all batteries magnetic? No, some don't have magnetic ends. Some Redilast will have issues & Yezl 18650. Before you purchase, take a magnet and check your cells have magnetic + and - ends. Most do, but not all -let me know any that don't so I can add to this brand list!
What current setting do I need? The maximum charge rate is around 1C for most cells. So a 350mah 10440 should not be charged faster than 350ma. Many people recommend a lower rate (0.6C) to prolong battery life. This means a 10440 would have an 'ideal' setting of around 210ma.
What leads come with your chargers? The basic chargers without the display come with one set of leads with Magnets soldered to the end. All the chargers with the built in voltmeters also come with Croc Clip leads with small magnets supllied in the jaws.
All the prices below include Paypal fees and international shipping (Not tracked) I will resend any lost items at my discretion. If you need to add a 'note' to your order you will need to manually pay in paypal rather than use these links.
These are amde from aluminium and use a Chinese TP4054 IC which isn't as accurate as the USA version present in the chargers which have a voltmeter.
Add to Cart: 100ma Basic Charger in silver -$17
Add to Cart: 200ma Basic Charger in silver -$17
Add to Cart: 300ma Basic Charger in silver -$17
Add to Cart: 400ma Basic Charger in silver - $17
Add to Cart: 500ma Basic Charger in silver - $17
Add to Cart: 600ma Basic Charger in silver -$17
Add to Cart: 700ma Basic Charger in silver -$17
Add to Cart: 100ma Basic Charger in RED -$19
Add to Cart: 700ma Basic Charger in RED -$19
Add to Cart: 100ma Basic Charger in BLUE - $19
Add to Cart: 700ma Basic Charger in BLUE - $19
Add to Cart: 100ma Basic Charger in BLACK - $19
Add to Cart: 700ma Basic Charger in BLACK - $19
Double Current Chargers
A simple switch toggles between two current settings. Common settings below. These all have USA upgraded ICs and a built in Voltmeter
Add to Cart: Dual 480ma / 700ma Leftie -$39
Add to Cart: Dual 90ma / 200ma Leftie - $39
Triple setting charger
A simple switch toggles between three current settings. Common settings below. These all have USA upgraded ICs and a built in Voltmeter
Add to Cart: Triple Leftie 90ma/320ma/620ma - $44
Add to Cart: Triple Leftie 90ma/320ma/700ma - $44
Quad Setting Charger
A simple switch toggles between four current settings. Common settings below. These all have USA upgraded ICs and a built in Voltmeter
Add to Cart: Quad 90ma/300ma/480ma/700ma - $54
8 Current Settings: 50ma, 100ma, 200ma, 300ma, 400ma, 500ma, 600ma, 780ma
Add to Cart: Octa Black Rightie -$59
$59 High Current Chargers These all require a high current (2 amp) USB socket. Most computers are unable to supply enough current.
Add to Cart: High current 500ma/1200ma Black Rightie - $49
Add to Cart: 500ma/700ma/1200ma Black Rightie- $54
Add to Cart: 500ma/1000ma/1200ma Black Rightie - $54
4.2v / 4.35v Charger
This is a specialist charger - Most 18650s will be damaged with this when used on the 4.35v setting. Only VERY limited number of 18650's are designed to take this 4.35v setting. If you don't know for SURE that your your cell is compatible, please do not purchase. 4.2v setting set to 500ma ; 4.35v setting has max 1000ma (dropping to 500ma at 4.2v)
Add to Cart: Dual 4.2v/4.35v Black Rightie - $49
18650 Cradle This is a cradle for 18650's suitable for all chargers with built in voltmeter. Particularly good with the Octa charger as it ensure you get the polarity correct. Only available when ordered with a charger
Add to Cart: 18650 Cradle - $7
If you want something different to the above, you can Post to the thread, PM me or Email me at This is also my paypal account. Changing any of the current settings is easy and not chargeable. I can also swap Leftie's for Righties etc. If you know what you need and can specify it , I'm fine with you doing that directly in paypal with a paypal note. If something isn't right I can email you.