Battery charging

After much seeking, there is no cheap battery charger that can take a lithium polymer cell with a connector and recharge it. The only stuff available is oriented towards RC hobbyists and is really overkill and costs a lot. Even if there was something like that on the market in China we can't sell it without paying several grands for testing it in the lab.

Therefore we can't order an off the shelf part. Also, li-poly cells can't be shipped in their charged state. So it seems we have to bite the bullet and do what we were trying to avoid, which is upgrade our remote to be able to recharge its own battery...

This is a lot of work and a lot more components. We're laying out the boards now hoping to get the RF issue and the charging straightened out in 1 trial and not waste any more time. We will also try to coerce the testing lab into including all this new circuitry in their original estimate.

Li-poly cells are hard to charge. There's a preconditioning phase, a fast charge phase, a constant voltage phase, and the battery absorption must be measured along with its temperature. There's an IC that does all this but it needs to be programmed carefully and it requires many external components.



Our current design is quite complex to get this to work. We had to figure out the C rating of the battery, the capacity, the charging time, which temperature window to enable charging for, and a lot more, took almost 2 days but now we have a connection diagram that we're turning into a PCB design. In the process, we've also found a reliable battery guy who answered our inquiries diligently and in good English from his honeymoon location.

Presently we're running into trouble with insufficient space to place all these components. We have more capacitors, resistors, LEDs, a thermistor, a regulator, and a USB mini B connector to draw power from the USB port (no data connection, only used for charging). The board will have to be optimized to death just like the receiver...

The bad side is that this may take another 1-2 days. Then we need to get some more PCBs and test so perhaps it's a 7-10 day delay. The good side is that we won't need to worry about these batteries anymore! You won't even need to open the remote control, just plug it into your PC's USB port for an hour and you'll have a brand new battery. you can even use the remote while it's plugged in.

When the voltage drops the LEDs will fade and eventually no longer light up but the remote will still work quite normally; that's how you know it's time to charge.

In case you're wondering -

1. yes, we promised no more improvements or design changes or features, but unfortunately there's no charger! And we can't even sell you more batteries because they won't be charged to more than 50% when they're shipped. So it seems this time we don't have an option...

2. The receiver's battery is ultra high pulse drain and ultra high capacity so it cannot also be rechargeable. We will have to make these available, fortunately though, these are already charged when they ship (as they aren't rechargeable) so ... this is a good combination! Remember we're working with many constraints: miniaturization, battery life, and a lot more. This is the very best compromise for this particular product and its intended usage.

--

Electronics is hard... as we're putting together the components we find the USB mini connector is still huge compared to the board, we'll need to change the plastic enclosure, luckily the plastic mold has not been created yet. The positioning is HARD because if it's too close to the antenna the RF range will suffer. As usual we're trying to keep everything as small as possible, don't want to add any thickness or length to the remote... The hole we need to make in the enclosure interferes with the snap fit mechanism which is OK since you won't need to open this so the remote can be closed in many ways now, doesn't need to be user friendly to open it.

Again, sorry to throw everything out incoherently but things are just hectic. We need to fix the motors, fix the range, fix charging.

In the interim we've fixed the other problem, which is that because the assembly house took too much time, all vendors ran out of 3 needed parts... but we've found stock and replacements so now that's ok...

Too many things to report everything. We're in a tsunami of to-dos and working 7 days a week. We'll bring you this product, and it will be good and beautiful... :)

Comments

By Lance_Lake at 2010-05-17 14:07:57 Reply

I know you aren't putting new things in (except the charger), but software wise, you should have the option on the website to set it "Auto recharge". Basically, when a certain time hits (settable by the website), it sends out a low shock. 5 min. later, a medium shock. 5 min. later and every min. after, a high shock.



This stops when the recharger is plugged into the USB to recharge.



Also, you get a low shock to signal when it's full and safe to remove. Remove it before and get the high shocks until it's plugged back in.



Perhaps if you can, incorporate it directly into the unit itself so that the website isn't required?

By dyonisos at 2010-05-17 16:57:42 Reply

I'm wondering about the life time of receiver batery since you add the micro motor. If the receiver is going out of power, what could we do ? Buy new batteries from you ? Is it possible to change it user friendly inside the module ?

By dreamloverlabs at 2010-05-18 01:52:27 Reply

Shocking the wearer when the remote runs out of batteries is not in the plan, the remote isn't to be managed by the wearer anyway.



The battery in the receiver is non rechargeable. The receiver is waterproof so it can't have a connector sticking out. Besides connectors are huge compared to the circuitry.



So you will have to buy a new battery when it runs out. With no motor it should last 3 months. Using the motor can deplete it very fast - it's intended for occasional use anyway.

By fgordon at 2010-05-18 02:35:57 Reply

What type of battery does the receiver use?

By dreamloverlabs at 2010-05-18 02:46:34 Reply

A spiral type high pulse drain 14250 with 700-800mAh capacity, 300mA pulse drain, and a specific wire length, mounted at a specific point on the battery so that the extra thickness is in the right spot where the enclosure will tolerate it, and a specific connector.

By Henry at 2010-05-18 05:19:19 Reply

Could I make a suggestion:



- Make the unit without motor for version 1.

- Add the motor and rechargeable battery for version 2.



Using the motor means much shorter battery life, so it needs to be rechargeable. It's not good to keep opening a waterproof seal and it's not good to keep buying batteries and throwing them away.



The advantages:

- gets the product shipping sooner and brings money in

- avoids many technical problems: battery life, rubber motor covering

- makes the device cheaper



The disadvantages:

- no "good boy" feature

- disappointment about postponing the surprise feature



If you're in doubt have quick survey to see for how many people this feature is deal-breaker.

By dreamloverlabs at 2010-05-18 08:31:09 Reply

The motor is not holding up launch. Many things still need to be done including incorporation, a test assembly run, the new remote with charger, etc.



If we get to the point where the motor's the only thing that's waiting we may very well release without it but it's likely we'll have this figured out soon since we now have metal pieces to attach to the motors and Jason's promise that we can go to another rubber guy if the present one keeps giving problems.

By Henry at 2010-05-18 09:40:18 Reply

How often do you think the waterproof receiver will have to be opened to replace the battery? Once a month? Once a week?



I understand the motor is coming along quite well, but as soon as the motor is used the battery life is going to be shorter and the waterproof unit has to be opened more often.



Tough decisions!



I suppose ideally the receiver wouldn't be opened at all. And having a recharge connector on the receiver runs into waterproofing issues. I don't know how practical wireless recharging is, but perhaps something to explore for future versions.

http://en.wikipedia.org/wiki/Wireless_recharging

By dreamloverlabs at 2010-05-18 09:59:48 Reply

Don't even dare guess how much the testing lab will charge to be able to sell something with inductive charging :)



See the latest post about battery life, it's not that bad really.

By dreamloverlabs at 2010-05-18 09:24:13 Reply

1.



Not only is it not good to keep opening a waterproof enclosure, but also there is a max number of times you can rescrew it closed before the plastic gets messed up and it no longer closes right. This is about 10 to 15 times. If each battery lasts 3 months that should be more than enough, and we'll also offer a new plastic top for separate purchase should you need a new one (the top is the part that gets damaged a bit every time you close it). We may even give out 2 top parts in each unit just to be on the safe side.



In order to overcome this we'd have to use brass inserts but again miniaturization is what we're optimizing for - trying to keep everything as small as possible.



2.



Recharging the receiver's battery is out of the question for the near future due to PCB space, physical space in the enclosure, the need to have a connector which would greatly increase waterproofing complexity, and more.



3.



Current: see upcoming post.