As usual when it comes to li-ion chargers and other potentially dangerous china made electronics I opened and checked freshly arrived MP1 charger to ensure everything is OK.
Being curios creature I "googled" some IC markings from MP1 PCB and found out that "heart" of this charger is SE9017 chip (http://www.alldatasheet.com/datasheet-pdf/pdf/292099/SEAWARD/SE9017.html) with really nice features.
XTAR was very considerate when designing this charger as they used two of these IC in parallel connection to split power dissipation to two IC, thus making them run cooler while still using simple and cheap PCB.
They made no shortcuts and implemented all recommended features from data sheet.
Interesting part is that with simple resistor change it should be possible to increase charging current. For example by replacing existing 3.47kR resistors (PCB markings R5, R6) with 2kR value resistors charging current should be around 1A. This will for sure make IC -s run hotter so it might be wise to ensure additional cooling by attaching (AA) miniature aluminum heat sinks on them. Obviously charging trough standard 500mA usb port would not ensure sufficient current so AC charger (for example from cell phone) that supports higher current would be needed.
By using other resistor values it should be even possible to set charging current around 1.5A !
I have not yet tried this modification so take everything written here with a grain of salt
If this works MP1 could become cheapest hi-quality high current charger.
Is it just or is there no mention of the minimum charge current in the datasheet. It could be a great option for 10440s if it goes low enough. I don't know of any good options for low current chargers other then building your own.
There is no minimal charging current stated but it can be set to very low value if needed. From example in data sheet with 10kR resistors charging current would be set to 100 mA for each IC resulting in 200 mA to battery.
I finally found some time to make preliminary test. Seems like manufacturer statement for charging current tolerance (+-20%) is quite true and in case of IC's on my MP1 on negative side. Replacing original 3.74k resistors with 1.5k results in charging current of approx. 1A. Actually instead replacing existing resistors there are pads parallel to them (r9 and r10) so it might be easier to simply solder another pair of resistors, for example 2.7k for total value of 1.56k
Little foam pads are used as support for small heat sink that is glued to ic's with artic alumina. Further testing regarding charging current and pattern as well as heat sinking performance will be done ASAP (hopefully this week)
Despite looking good on paper and claiming cc/cv charging pattern measurements show that SE9017 ic doesn't in fact work as advertised. As you can see in chart below, charging current is not constant and drops as voltage rises. Even trough this charger will not be as fast as true cc/cv charger, modifications described in previous post will speed up charging process with minimal effort for modification while still maintaining reliability and security of charger and battery. Heat sinking of IC 's is recommended and even small piece of aluminum should be more than enough. As chip has thermal throttling function things should remain safe even in case of overheating.
Another interesting thing is that green led turned on at 4.13V while still charging at 200mA, however charging did not stop and it continued until charging current dropped to approx. 60 mA when charging was completely terminated.
Seems like SE9017 ic is not the sharpest knife in a drawer of li-ion charging ic's. It gets the work done but leaves bitter taste for not delivering promised features. Despite this it seems to be popular choice for different chargers. For example ML-102 from intl-outdoor uses them too in same double configuration but with higher set charging current (1.6k resistors)
I just checked and markings on ic is 57b6 (???) TP4057 should be 57bM... They do look very similar regarding operation and performance. Anyway ML-102 is best little charger out there...
I don't know what the ideal charge rate is for 10440s is, but Cottonpickers on the CPF Marketplace has a few to choose from: http://www.cpfmarketplace.com/mp/showthread.php?240304-gt-FS-Cottonpickers-Chargers-incl-Worlds-smallest-Li-ion-charger-with-display
I've bought a couple of things from him and had good service each time.
while we're on the subject of MP1 mods and cottonpicker's mods, has anyone hooked up a standalone mini voltmeter display to this MP1 charger like cottonpicker's mods? Picture of this is in my post29 (link) https://budgetlightforum.com/t/-/7566#comment-164078. I just received this voltmeter, and using a different charger, connected in parallel, voltage will always show the charging voltage(4.2v) when charging, so I'll need to add a switch to turn it off when charging.
side question: are the XTAR 18650 2600mAH still Sanyo's ? i plan to order an MP1 and a pair of the $13.50 protected from the group buy (link).
^ Danke Steve for the pics, that was fast! I still haven't ordered the MP1 yet. Just a guess, your jumping voltage is probably from either the USB or your MP1, which would always show the actual input voltage when charging. When I get mine, I'll probably do the same so I can use it as a quick volt checker when not powered.
I was intending to gift 2 flashlights, but one of my cheap 18650 went kaputt, after 2 charges. So to be safe, I'm looking at $20+ for 2 xtar protected batts and the MP1, and hopefully after wiring the volmeter on it, it'll make for a relatively safe and worry-free gift. :)
