Aseras said:
my charger is a bit flay too, sometime i have to fiddle with it to get it to start a charge cycle.
I'm also uneasy that the batteries and probably the lithium charger are unprotected. 18650 batteries run about $10-12. a good charger ( not a voltage charger, a true lithium safe charger ) will run about $40.
it's a good investment and might save you from a lot of pain later on if the charger blows a lithium. Loose unprotected cells like that are what that laptop recall were about. they can and will explode and burn, producing their own oxygen to sustain them should they be overcharged. overcharging is hard on new batteries, but old batteries can easily be overcharged to the point of spectacular failure.
Hi Aseras,
The 18650 cells that come with the RPL (not sure of the cells you have, since you got yours 2nd hand.) are NOT protected cells. The battery charger is protected, so there is not a problem with leaving them on the charger. When the cell is charged, the led turns green and all charging stops (no trickle charging). Before you can recharge them, they need to be discharged somewhat. This is because the charger will sense they are still near a full charge and above the recharge threshold voltage. To avoid any flakiness, plug the charger into the wall and wait a couple of seconds before installing any batteries for charging.
The charging cycle of a lithium-ion cell depends on two things.
1. The capacity in mAhrs of the cell (larger capacity means more time needed to fill it up).
2. The current output of the charger. The more current it can drive, the more expensive it will be.
The charger that comes with the RPL is rated at 350mA.
It will run on 110 / 220 and 50/60Hz, I'm not sure how the frequency or input affects the output current or if it even does.
I don't know a whole lot about battery charging efficiency, but lets say that every mA (350) goes right to the battery and gets stored at 100% efficiency, then the amount of time to charge a 2400mAhr cell would be 2400/350=6.85 hours.
If two cells are put into the charger at the same time, then each cell would only be getting 175mA each, so it would take twice as long or 13.7 hours.
Knowing how much these types of things are spec'd, 350mA may be a "best case".
That said, when we came out with RPL (1st laser to use an 18650 cell), this was the only charger I could find period. Since then, I have seen more powerful ones, but they are pretty expensive and bulky. It's a much better deal to just have 2 or 3 extra cells so you always have one ready to go.
The RPL itself has built in lithium battery protection, so it's safe to use unprotected cells in it.
In fact I may have mentioned this in my post about duty cycle. What I found was that there is no problem with the RPL diode overheating, even with 100% use, what I found was that the circuit to protect the lithium battery is what caused some lasers to "shut down" after many minutes of use. What happens is these battery protection ICs will sense current draw, and battery output voltage. If the current or voltage sense gets tripped, the laser is powered down.
This is a good safety feature if implemented the right way, but these sense levels were set for the kind of cells we had 4-5 years ago that were rated a 1400mAhr or less and limited to a couple of amps of current. The LG 2400mAhr cell can output like 4 amps continuously until it reaches a low voltage limit that is lower than those of cells used in the past.
I'm still working on this project in my spare time. It's easy (electronically) to bypass this circuit altogether, I've done that. What is hard is doing the mechanical part of this and get it back together. As long as you have an ESD protected workbench, microscope or good eyes (under 30 years of age I would say...hehehe, a nice professional grade solder station (MetCal or equivalent) with a sharp pointed tip and a steady hand with patients, you can do it too.
I'm going to photograph each step on the next one I'm getting ready to experiment on, so I can document this process.
Jack
