Topic: Please clarify 9 Volt issue

Since there is voltage (11.5 Volts) being sent to the 9 Volt battery clip is is apparent that a rechargeable cell is required.
Installing an alkaline cell on a recharging circuit dangerous.
IMHO The Chembytes should clarify this issue.
In another thread there is a moderator suggesting to people to install 9 volt batteries into their Chumby. Is this the official stance?

Will a rechargeable cell work? What exactly will it do? will it hold the control panel in memory as well as the time? in case of power loss?

IMHO it is not unreasonable to let the masses know about what that 9 volt clip is for. It is supposed to be an open system. why not tell us?

Maybe Chumby wants to SELL us a special 9 volt battery. The voltage on the clip is the same as that on the charger pads on my lithium 9 volt charger.

I know there are several types of rechargeable 9 volt chemistry's. I know this can make for some confusion and potential danger if the wrong battery is used in the wrong type of charger. What type of charger is built into the Chumby? Is there some type of software access to the battery circuit which will show charging status? Is this meant for a later update?
Anyway guys cut us a little slack. If this is in fact a dangerous issue Chumby users deserve to know. Many are natural experimenters and will find an unused 9V clip too much to resist. somebody sticks the wrong battery on there and the next thing you know their chumby ends up in flames. God forbid somebody's house burns down.
If the clip is not meant to be used maybe The chumby company should cut the clip off in order to prevent just such an accident. Maybe full disclosure would be cool so us end users can act safely while still experimenting in the name of chumby fun.
OK?
Oh and have a happy New Year.
Yaesumofo

Re: Please clarify 9 Volt issue

I have to agree. I received a Chumby for Christmas and promptly put a fresh alkaline 9V battery in it. My Chumby is sitting on my nightstand, plugged in and on while I am now several hundred miles away until tomorrow morning. With all the posts lately I have had a few restless nights wondering if my apartment will be in ashes. I called the office this morning and had them go in and pull the plug. It was an interesting conversation trying to explain why I needed them to do this. I sure hope we get some definative answers soon.

Re: Please clarify 9 Volt issue

I hope I did not cause this.
Somewhere on this site and or in the faq it say NOT to install a 9V cell. I am assuming that Chumby figures we are all good little drones and that we will read and fall inline with all hidden directions.
I am quite sure the offical stance is NOT to insatll a 9 volt battery.
That said this will not prevent people from doing it. if it is dangerous the clip shouldn't be there in the first place. IMHO.
Since it is there it can be reasionably expected that people will install a 9 volt in it's place. Why not tell us that there is charging voltage on the clip and to only use a rechargable battery if you must put a battery in it's place.

I hope I did not cause distreess with my postings. I just happen to beleive that the Chumbyites need to get on board the bus and help us to operate our Chumbys in a safe and correct manner while still having fun and in the spirit of experimentation allowing for those of us who can't resist an empty 9 volt clip.
Yaesumofo

huckfinn wrote:

I have to agree. I received a Chumby for Christmas and promptly put a fresh alkaline 9V battery in it. My Chumby is sitting on my nightstand, plugged in and on while I am now several hundred miles away until tomorrow morning. With all the posts lately I have had a few restless nights wondering if my apartment will be in ashes. I called the office this morning and had them go in and pull the plug. It was an interesting conversation trying to explain why I needed them to do this. I sure hope we get some definative answers soon.

Re: Please clarify 9 Volt issue

I have been running a 9volt in my chumby for a fe weeks now. I have had no problem so far, and I cant remember which thread it was, but I believe bunnie said that the 9volt in the current release chumbys (not the Alpha Prototype) is safe. Don't quote me until I can find the original quote myself.
I dont expect any answers from the folks at chumby for a few days due to the holidays, but I am sure they will give a solid answer soon.

Re: Please clarify 9 Volt issue

Are you running a rechargable cell? I would hope so since there is 11.5 volts present on the clip.
What exactly does it do?
Does it prevent the need for chumby to download the CP? set the time? load the channel?
Have you removed the power with the battery in place and without and compared load times or done any other testing to see what effect the battery has?
Thanks.
Yaesumofo

Ganson wrote:

I have been running a 9volt in my chumby for a fe weeks now. I have had no problem so far, and I cant remember which thread it was, but I believe bunnie said that the 9volt in the current release chumbys (not the Alpha Prototype) is safe. Don't quote me until I can find the original quote myself.
I dont expect any answers from the folks at chumby for a few days due to the holidays, but I am sure they will give a solid answer soon.

Re: Please clarify 9 Volt issue

There is a high-impedance path between the DC input and the battery input. The path consists of the reverse leakage through schottky diodes, less than a microamp. There is also some charge storage on the node as well (about 10 uF).

The reason why you see 11.5V is because reverse leakage through the battery voltage measurement circuitry will slowly charge up the 10uF of capacitance from charge sharing of voltage from the regular DC input line. The amount of reverse leakage and charge sharing is very tiny, but even a tiny current over a long period of time will charge a capacitor and therefore when you put your probes across the node you will see that charge.

If you install a regular 9V battery, this tiny leakage current will not charge the battery. Therefore, any standard 9V non-rechargeable battery would be fine to put inside the chumby device. You do not need a special rechargeable battery for safety.

As alluded to before, there is a pair of diodes that help the power management for the chumby. The diodes sit between the power supply, the battery, and the power input to the core board in "Y" topology. Therefore, if the power is lost, the battery will take over as the voltage supply. Primarily, the battery is there to keep the cryptoprocessor/alarm power manager IC alive in the case of a power outage, so that the chumby will wake you up if the power goes out. A more detailed discussion of this functionality is happening in the "Hardware" section, although most of the power management features being discussed are due out in a firmware update soon.

Re: Please clarify 9 Volt issue

Thank you Bunnie.

Re: Please clarify 9 Volt issue

This is both good and bad news.
I am very happy to be wrong about this from a safety point of view.
Unfortunately no matter what battery is in use it will drain rather quickly and not be able to rebound when power is applied.
since the chumby is NOT charging the battery.
If a power outage is longer than 1/2 hour or so the battery will be drained.

Can the system be set up so that if power is lost and a switch to backup 9V happens that the chumby drops into a power saving mode?
That would be a sort of consolation since the battery is not being charged.
Using a rechargeable cell would certainly be a greener thing to do.

Yaesumofo

Bunnie wrote:

There is a high-impedance path between the DC input and the battery input. The path consists of the reverse leakage through schottky diodes, less than a microamp. There is also some charge storage on the node as well (about 10uF).

The reason why you see 11.5V is because reverse leakage through the battery voltage measurement circuitry will slowly charge up the 10uF of capacitance from charge sharing of voltage from the regular DC input line. The amount of reverse leakage and charge sharing is very tiny, but even a tiny current over a long period of time will charge a capacitor and therefore when you put your probes across the node you will see that charge.

If you install a regular 9V battery, this tiny leakage current will not charge the battery. Therefore, any standard 9V non-rechargeable battery would be fine to put inside the chumby device. You do not need a special rechargeable battery for safety.

As alluded to before, there is a pair of diodes that help the power management for the chumby. The diodes sit between the power supply, the battery, and the power input to the core board in "Y" topology. Therefore, if the power is lost, the battery will take over as the voltage supply. Primarily, the battery is there to keep the cryptoprocessor/alarm power manager IC alive in the case of a power outage, so that the chumby will wake you up if the power goes out. A more detailed discussion of this functionality is happening in the "Hardware" section, although most of the power management features being discussed are due out in a firmware update soon.

Re: Please clarify 9 Volt issue

That is correct, the battery will be discharged within half an hour of power loss if the device is full on. What's supposed to happen is the firmware detects the loss of power and requests the system to be shut down, in which case the main CPU will be turned off and only the real time clock/alarm circuit would stay alive, and the chumby could run for a couple of days in that state. This new functionality will be released in a firmware update.

There have been many requests for a rechargeable battery--please look around the forum for the basic reasons for why they are not included. Short answer is cost (long term and short term costs) and safety.

Re: Please clarify 9 Volt issue

Bunnie, thank you for your response. So with the current firmware the Chumby should stay on if power is removed but a fresh 9V battery is installed? I plan on getting one of those rechargeable photo frame batteries as mentioned in another post to keep my Chumby alive for an extended time during a power outage.

Re: Please clarify 9 Volt issue

Yeah, I freaked out when I read that there is voltage on the plug after having an alkaline 9V in there for weeks. Last night, I got out the meter and checked it out. The voltage dropping almost immediately after putting the probes on it told me that there wasn't enough current there to worry about a battery in there.

Re: Please clarify 9 Volt issue

For now, the chumby will stay powered on with the 9V battery installed but don't count on that behavior, it will change soon.

However, the rechargeable photo frame battery plugs into the DC input, so it looks exactly like the wall adapter to the chumby--so your idea will still work, and work even better, because if you accidentally knock the DC input connector out (it happens) the chumby will still stay on thanks to the 9V and gives you a moment to plug the external pack back in.

Re: Please clarify 9 Volt issue

Well in one of your other posts you mention removing the beads to fit the 9V. I was able to fit it in just fine with the beads, but now that I removed the beads I am wondering if that rechargeable photo frame battery would fit inside the chumby. There seems to be plenty of room with the beads removed. If so I would not even use the 9V and since the rechargeable is inside, pulling the plug "should" be less likely to happen. In another of your posts you mention that you have used several of these rechargeable photo frame batteries, have you tried fitting it inside the chumby? If so any concerns on the heat buildup inside? I would not want to cause any thermal issue with either the Chumby or the battery.

Sorry to derail this topic slightly off of the 9V battery.

Re: Please clarify 9 Volt issue

I don't think you'd have a thermal issue with putting those batteries inside the chumby if the batteries are operating normally and not damaged in any way.

Rechargeable Li-Ions, as you may know, do have a propensity to overheat though, especially as they age. I've had several Dell laptop battery packs almost go into thermal runaway on me in the past. If that happens, of course putting the batteries in an insulating bag like the chumby would simply aggravate the problem.