Hey folks,
I’ve got a few 3.7v Li-Ion batteries. One is 6600mAh, another is 2500mAh. I also have a Spark Battery Shield and an Adafruit charger.
These large batteries take sooooo long to charge. Anything I can do to speed up my charging cycles?
Thanks!
You would need to use a charger capable of providing more current to the battery, while being extra super careful not to provide TOO MUCH current to the battery in question.
Since a charger cannot know the capacity of a battery it is charging, it is often the choice of the charger designer to assume a low capacity battery, which limits the amount of current it will provide.
The Adafruit charger will probably have a way to adjust the charging current. you’ll have to look at the product page for the charger you have to get instructions on how to do that.
Hello wells,
Quick note to remind you that handling LiPos is something that you should be very careful with.
As far as my understanding goes, you can charge a LiPo safely at 1C, this means that for the 6600mAh you could charge it at 6.6A and for the 2500mAh at 2.5A. However, it’s better not to assume and follow each battery specifications, If you send me the link to your products I can confirm this. From adafruit I could not find any 6600 nor 2500 Lipo, only Li-ons which have a different charging rate, in the case of Adafruit’s ones they are about 0.5C so you can charge them at 3A and 1A but you do need to find a charger that is able to provide those Amps, Adafruit’s charger can provide up to 1A.
There are special batteries that have a higher charging C rate which allow you to charge them faster. This requires bigger chargers and a proper power source that can provide the current in order to charge them.
lv4n, you’re absolutely right. They’re Li-ions, not LiPo. Sorry, still learning terminology 
6600: https://www.adafruit.com/products/353
2500: https://www.adafruit.com/products/328
I replaced the surface-mount 2k resistor with a 1k (as specified on the back of the charging board) to increase it to 1A. I think it took about 10 hours to charge the 6600mAh though – am I incorrect in thinking that it’s really slow?
Thanks for your help!
No worries wells, it’s actually a little bit difficult in the beginning. I fly quadcopters so I use them quite a lot. I would be lying if I tell that I didn’t have to read a lot to feel comfortable with the subject, I’m sure there’s still things that I don’t know 
By the way, one of them is actually a LiPo (2500, note “Polymer” in the name) and another is a Li-ion (6600).
A rough calculation throws that
6600 should take around 8 hours at 1A
2500 should take about 3 hours at 1A
It’s long, but it is like that. If you get a charger that can do 3A, it will take about 3 hours to charger the 6600, don’t use this one with the 2500 as it is rated to be charged at 1.2A only, so the current charger is good enough.
If it’s taking you 10 hours for the 2500 make sure that your power source can provide a good 1A of current, better if you have it hooked to a 1.5-2A power source.
ahhh!
Ok. Well I think the Li-Poly one is the one I’m going to end up using for this project anyways. I tried searching for a 3A charger, but all I’ve seen on Google are car battery chargers etc. I don’t think I want to use one of those. 
It is possible to recharge li-ions at greater than this 1C rate, but you then have to be very careful not to have the temperature rise too much or too fast. At a minimum this requires using thermistors and circuitry to track the temperature, which is why most of the single-cell lithium chargers don’t bother.
This is good advice and I wanted to point out that the Adafruit charger has a 10k resistor on the board that is designed to be replaced by a 10k thermistor specifically for this purpose, if you need make the charge rate temperature dependent.
Posting what I couldn’t post because of the read-only time:
If you are going to using the LiPoly, there are lots of source where you can get them, google the following:
This is the one I use http://www.hobbyking.com/hobbyking/store/__14633__HobbyKing_8482_E4_Balance_Charger.html, simple and straight but you should make sure find a proper power supply. There are way more options than just this one.
A few tips:
If you follow this it will have a longer life span and help preventing accidental fire. If your battery ever gets puffy (kind of filled with air, it’s time to stop using it). Don’t leave LiPoly charging unattended, charge them in a place that your house wouldn’t burn down in case it sets on fire.
Got it. Is anything available for Li-Ion batteries? Or is that charger cross-comparable?
I found this listing on ebay which I have never tested before but it says it charges li-ion and lipos:
http://stores.ebay.com/A-OK-battery/1S-4-2V-/_i.html?_fsub=3192806010&_sid=911311590&_trksid=p4634.c0.m322
and this from hobbyking: