voltage spike on solar lipo charger
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- bwh13
- Posts: 15
- Joined: Thu May 23, 2013 6:15 pm
voltage spike on solar lipo charger
Hi All,
I'm running a canon sd1000 (camera) off the 'load' side of the v1.0 solar charger. I have a 3.7V 6A lipo battery on the 'battery' side of the charger and a 2W 6V solar panel coming in.
the camera normally takes a 3.7V battery (albeit much much smaller than the 6A i'm using now.)
as i was running the setup today (partly sunny) the camera would occasionally shut down. i'm running a canon hack development kit (chdk) that runs a timelapse script -> anyway, this script writes a log file that (among other things) writes input voltage. the last line in the log before the camera shut down recorded a voltage of 5.8V.
1-could this be right? does the solar lipo charger allow loads to spike like that?
2-is there some regulation on the 'load' side of the charger? or does it allow any voltage to come out?
3-could the battery output a voltage like that?
it is entirely possible that this is an erroneous log entry, but it seems to be recording other values correctly. i'm just covering some of my bases here.
thanks in advance for any insight!
I'm running a canon sd1000 (camera) off the 'load' side of the v1.0 solar charger. I have a 3.7V 6A lipo battery on the 'battery' side of the charger and a 2W 6V solar panel coming in.
the camera normally takes a 3.7V battery (albeit much much smaller than the 6A i'm using now.)
as i was running the setup today (partly sunny) the camera would occasionally shut down. i'm running a canon hack development kit (chdk) that runs a timelapse script -> anyway, this script writes a log file that (among other things) writes input voltage. the last line in the log before the camera shut down recorded a voltage of 5.8V.
1-could this be right? does the solar lipo charger allow loads to spike like that?
2-is there some regulation on the 'load' side of the charger? or does it allow any voltage to come out?
3-could the battery output a voltage like that?
it is entirely possible that this is an erroneous log entry, but it seems to be recording other values correctly. i'm just covering some of my bases here.
thanks in advance for any insight!
- john444
- Posts: 443
- Joined: Sun Mar 04, 2012 2:42 pm
Re: voltage spike on solar lipo charger
Hi Bwh13,
a. The 390 is designed to limit charge voltage to 4.2-V.
b. The 390 couldn't possibly put out that much voltage with a 6-A LiPo connected.
c. The 390 couldn't put out that much voltage with a camera as a load.
d. The 6-V / 2-W (333-mA) panel couldn't put out that much voltage with
either the LiPo or the camera connected.
It seems so improbable, I would spend my time looking at other possibilities.
Good Luck, John
I do not believe that it is possible for the charger to output that much voltage.bwh13 wrote:the last line in the log before the camera shut down recorded a voltage of 5.8V.
1-could this be right? does the solar lipo charger allow loads to spike like that?
a. The 390 is designed to limit charge voltage to 4.2-V.
b. The 390 couldn't possibly put out that much voltage with a 6-A LiPo connected.
c. The 390 couldn't put out that much voltage with a camera as a load.
d. The 6-V / 2-W (333-mA) panel couldn't put out that much voltage with
either the LiPo or the camera connected.
It seems so improbable, I would spend my time looking at other possibilities.
Good Luck, John
- bwh13
- Posts: 15
- Joined: Thu May 23, 2013 6:15 pm
Re: voltage spike on solar lipo charger
Thanks for the thoughts john444.
I'm inclined to believe you, and I set out to find test the hypothesis.
Conditions: full sun on the solar panel. Timelapse script taking pics every 1 minute.
First Test: I ran the solar charger with the panel plugged in. The camera rig shut down after 30 minutes. The log file recorded multiple voltages of 5+ volts before the final entry of 5.8 v
Second Test: same conditions as before (full sun, 1 min. interval) but, I UNPLUGGED the solar panel from the charger. The camera rig ran for 3 hours before I shut it down. The voltages recorded in the log file were all 4.1 volts.
Third Test: same conditions except I ran it with the stock Canon 3.7v battery (not the 6amp lipo.) Solar panel and charger completely out of the equation. The script ran until I shut it down and recorded voltages of 3.6v
So I interpret these findings as: when the solar panel is plugged in under good sun conditions, the battery voltage increases under load.
I am inclined to believe that there is something amiss with the solar charger -> i.e. voltage spikes are making it through to the 'load' side of the solar charger.
I am pretty certain that I wired the capacitor correctly (the only soldering to do.) Maybe it's worth noting that it is the version 1.0 solar charger. I have the newest version of the charger yet to build, but since the components are more or less the same, I'm not sure that this will solve the problem.
Does anyone have any thoughts on what I could test to see that the panel being plugged in really is (or isn't) the culprit in this voltage spike situation? Am I missing something?
Thanks in advance!
I'm inclined to believe you, and I set out to find test the hypothesis.
Conditions: full sun on the solar panel. Timelapse script taking pics every 1 minute.
First Test: I ran the solar charger with the panel plugged in. The camera rig shut down after 30 minutes. The log file recorded multiple voltages of 5+ volts before the final entry of 5.8 v
Second Test: same conditions as before (full sun, 1 min. interval) but, I UNPLUGGED the solar panel from the charger. The camera rig ran for 3 hours before I shut it down. The voltages recorded in the log file were all 4.1 volts.
Third Test: same conditions except I ran it with the stock Canon 3.7v battery (not the 6amp lipo.) Solar panel and charger completely out of the equation. The script ran until I shut it down and recorded voltages of 3.6v
So I interpret these findings as: when the solar panel is plugged in under good sun conditions, the battery voltage increases under load.
I am inclined to believe that there is something amiss with the solar charger -> i.e. voltage spikes are making it through to the 'load' side of the solar charger.
I am pretty certain that I wired the capacitor correctly (the only soldering to do.) Maybe it's worth noting that it is the version 1.0 solar charger. I have the newest version of the charger yet to build, but since the components are more or less the same, I'm not sure that this will solve the problem.
Does anyone have any thoughts on what I could test to see that the panel being plugged in really is (or isn't) the culprit in this voltage spike situation? Am I missing something?
Thanks in advance!
- john444
- Posts: 443
- Joined: Sun Mar 04, 2012 2:42 pm
Re: voltage spike on solar lipo charger
@BHW, something definitely wrong here!
Do you have another meter that you could check things with?
I am afraid that if the 390 is putting 5.8-V into the 6-A LiPo,
the LiPo will be shot. That means the 390 is shot also.
Will the camera record the voltage from the 6-A LiPo w/o the 390?
Maybe post a photo of your wiring / setup.
John
Do you have another meter that you could check things with?
I am afraid that if the 390 is putting 5.8-V into the 6-A LiPo,
the LiPo will be shot. That means the 390 is shot also.
Will the camera record the voltage from the 6-A LiPo w/o the 390?
Maybe post a photo of your wiring / setup.
John
- adafruit_support_mike
- Posts: 68231
- Joined: Thu Feb 11, 2010 2:51 pm
Re: voltage spike on solar lipo charger
Do please post a photo of the charger and how you have things wired.
I agree with John that something is wrong, but don't know what. If you measure 6v across the terminals of a LiPo, you need to be fast because it's probably on fire.
The scenario that makes the most sense is one where the charger bypasses the battery and powers the camera directly. The power would droop when the camera's current consumption is high, but when the camera drops to a low-power state (which is to be expected in a battery powered device) its consumption is low enough that the solar panel can provide that much current at 6v.
I don't know if that's physically possible with the hardware you have though.
I agree with John that something is wrong, but don't know what. If you measure 6v across the terminals of a LiPo, you need to be fast because it's probably on fire.
The scenario that makes the most sense is one where the charger bypasses the battery and powers the camera directly. The power would droop when the camera's current consumption is high, but when the camera drops to a low-power state (which is to be expected in a battery powered device) its consumption is low enough that the solar panel can provide that much current at 6v.
I don't know if that's physically possible with the hardware you have though.
- bwh13
- Posts: 15
- Joined: Thu May 23, 2013 6:15 pm
Re: voltage spike on solar lipo charger
Thanks for the replies john444 and mike -
Here are some pics of my setup. I'm pretty sure that I've wired it correctly, but am more than willing to stand corrected!
Here are some of my most recent observations: I set the rig out the other day under overcast conditions and it ran smoothly, taking pics at 1 minute intervals for about 2.5 hours. The sky cleared and it became sunny and bright and the rig lasted for another ~45 minutes before it shut down. I had also loaded a fresh CHDK firmware and fresh script on the camera's SD card to guard against some settings that I may have inadvertently messed with.
I did some re-reading of the solar lipo charger tutorial and came across this information that 'admin-support-mike' seemed to touch on in his post: this is taken directly from the "Using the Charger" tutorial page -> http://learn.adafruit.com/usb-dc-and-so ... he-charger
"Load Sharing
The MCP73871 chip in the usb/solar charger has a very nifty feature called 'load sharing.' Say you have an every day lipoly charger and you want to use the battery while its charging. To do this, you might connect the project directly to the battery output. This means, however, that the charger is both charging a battery and driving your project at the same time. The charger is working extra hard and the battery is being charged and discharged constantly.
As an improvement, this design has a pass transistor inside the chip, connected to the output load from the input voltage, so that you dont lose efficiency from charging/discharging the battery. When the USB/Solar charger is powered from a USB port or panel, the load current goes directly from the input voltage to the output. If the current required is higher than what the panel or USB port can provide, the current is supplemented by the lipo battery, up to 1.8A"
The bolded text is my own emphasis added.
If I understand this right, does it mean that instead of the battery powering the camera, that the panel powers the camera directly under certain conditions, i.e. direct sun in this case? It might explain the voltage spikes that only seem to happen when it's sunny.
Thanks in advance for all your help - I really do appreciate your thoughts and comments!
I added 2 pics of my rig as attachments, but placed them inline above.
Here are some pics of my setup. I'm pretty sure that I've wired it correctly, but am more than willing to stand corrected!
Here are some of my most recent observations: I set the rig out the other day under overcast conditions and it ran smoothly, taking pics at 1 minute intervals for about 2.5 hours. The sky cleared and it became sunny and bright and the rig lasted for another ~45 minutes before it shut down. I had also loaded a fresh CHDK firmware and fresh script on the camera's SD card to guard against some settings that I may have inadvertently messed with.
I did some re-reading of the solar lipo charger tutorial and came across this information that 'admin-support-mike' seemed to touch on in his post: this is taken directly from the "Using the Charger" tutorial page -> http://learn.adafruit.com/usb-dc-and-so ... he-charger
"Load Sharing
The MCP73871 chip in the usb/solar charger has a very nifty feature called 'load sharing.' Say you have an every day lipoly charger and you want to use the battery while its charging. To do this, you might connect the project directly to the battery output. This means, however, that the charger is both charging a battery and driving your project at the same time. The charger is working extra hard and the battery is being charged and discharged constantly.
As an improvement, this design has a pass transistor inside the chip, connected to the output load from the input voltage, so that you dont lose efficiency from charging/discharging the battery. When the USB/Solar charger is powered from a USB port or panel, the load current goes directly from the input voltage to the output. If the current required is higher than what the panel or USB port can provide, the current is supplemented by the lipo battery, up to 1.8A"
The bolded text is my own emphasis added.
If I understand this right, does it mean that instead of the battery powering the camera, that the panel powers the camera directly under certain conditions, i.e. direct sun in this case? It might explain the voltage spikes that only seem to happen when it's sunny.
Thanks in advance for all your help - I really do appreciate your thoughts and comments!
I added 2 pics of my rig as attachments, but placed them inline above.
- bwh13
- Posts: 15
- Joined: Thu May 23, 2013 6:15 pm
Re: voltage spike on solar lipo charger
I just wanted to add some replies to 'admin-mike's comments:
I wasn't measuring the 6v spike directly: each time the camera takes a picture, the script that is running the camera logs a handful of values with one of those values being the incoming voltage. I have always assumed this to be the battery voltage, but am now inclined to think it is the situation where the 'load sharing' on the board is porting the incoming solar voltage directly to the camera.
When the camera rig is running solely off the battery through the board (i.e. the solar panel is UNPLUGGED), the voltage never records higher than 4.0v. This seems to lend credence to the idea that the incoming solar (when plugged in and in bright sun) is ported directly to the camera (i.e. the load).
Does this make sense or am I reading into the 'Charging Tutorial' info too much? I've included Figure 4.2 from that tutorial, but I'm afraid I don't read electronic diagrams too well!
Thanks again, one and all!
I wasn't measuring the 6v spike directly: each time the camera takes a picture, the script that is running the camera logs a handful of values with one of those values being the incoming voltage. I have always assumed this to be the battery voltage, but am now inclined to think it is the situation where the 'load sharing' on the board is porting the incoming solar voltage directly to the camera.
When the camera rig is running solely off the battery through the board (i.e. the solar panel is UNPLUGGED), the voltage never records higher than 4.0v. This seems to lend credence to the idea that the incoming solar (when plugged in and in bright sun) is ported directly to the camera (i.e. the load).
Does this make sense or am I reading into the 'Charging Tutorial' info too much? I've included Figure 4.2 from that tutorial, but I'm afraid I don't read electronic diagrams too well!
Thanks again, one and all!
- adafruit_support_mike
- Posts: 68231
- Joined: Thu Feb 11, 2010 2:51 pm
Re: voltage spike on solar lipo charger
I think the scenario laid out above is correct.
I read through the MCP73871 datasheet a couple of times and couldn't find anything about output voltage regulation. There's a lot about voltage regulation for the battery charging circuit, and current limiting to the load, but nothing about load voltage regulation. In fact, the datasheet makes some effort to point out the low voltage drop between the external power supply and the load.
That makes sense, really.. voltage regulation has a price tag. You lose a couple of volts through a linear regulator, and even low-dropout regulators need a couple tenths of a volt to work properly. The chip is designed around the assumption that you can run the load directly from either power source (the external supply or the battery), and that its job is to be as non-intrusive as it can.
In your case, you probably want to build a low-dropout regulator into your battery-replacement circuit/adapter.
I read through the MCP73871 datasheet a couple of times and couldn't find anything about output voltage regulation. There's a lot about voltage regulation for the battery charging circuit, and current limiting to the load, but nothing about load voltage regulation. In fact, the datasheet makes some effort to point out the low voltage drop between the external power supply and the load.
That makes sense, really.. voltage regulation has a price tag. You lose a couple of volts through a linear regulator, and even low-dropout regulators need a couple tenths of a volt to work properly. The chip is designed around the assumption that you can run the load directly from either power source (the external supply or the battery), and that its job is to be as non-intrusive as it can.
In your case, you probably want to build a low-dropout regulator into your battery-replacement circuit/adapter.
- bwh13
- Posts: 15
- Joined: Thu May 23, 2013 6:15 pm
Re: voltage spike on solar lipo charger
-mike-
thanks for that. a way forward!
couple of questions:
1) would something like the "Adjustable breadboard power supply kit - v1.0" http://www.adafruit.com/products/184 be a workable solution? I've read through the tutorial and it seems like the 'adjustable' nature of the board is what I'm looking for.
2) in your last line, the part about the 'battery-replacement circuit/adaptor.' Do you mean something to the effect that I would want to install this low-drop regulator on the 'load' side of the lipo charger? That seems to make the most sense in my mind, but will defer to you on this.
thanks again for the great response. the support is keeping me psyched!
thanks for that. a way forward!
couple of questions:
1) would something like the "Adjustable breadboard power supply kit - v1.0" http://www.adafruit.com/products/184 be a workable solution? I've read through the tutorial and it seems like the 'adjustable' nature of the board is what I'm looking for.
2) in your last line, the part about the 'battery-replacement circuit/adaptor.' Do you mean something to the effect that I would want to install this low-drop regulator on the 'load' side of the lipo charger? That seems to make the most sense in my mind, but will defer to you on this.
thanks again for the great response. the support is keeping me psyched!
- adafruit_support_bill
- Posts: 89476
- Joined: Sat Feb 07, 2009 10:11 am
Re: voltage spike on solar lipo charger
Not sure where the adjustable supply would fit in. I'm a bit late to the discussion, but from what I have read you just need to regulate the final output to the camera. A simple low-dropout regulator on the load-side of the charger should do it.
- bwh13
- Posts: 15
- Joined: Thu May 23, 2013 6:15 pm
Re: voltage spike on solar lipo charger
Thanks bill-
I mentioned the Adjustable Powersupply for a couple reasons:
- I need 3.7v to run the camera (adjustable)
- input voltages could run from 3 to 6 volts
- the kit looks doable for my level of skill and understanding (I had to look up what an LDO was)
- the kit was in-stock and in my price range
- the kit looks small enough to fit in my enclosure
I'm pretty much a noob when it come to electronics, so if anyone wants to mention or present me a stand-alone or simpler LDO setup, I'd love to entertain it.
I know that the 'Adjustable' is a breadboard setup, but it looks hackable enough for my purposes.
Thanks for any input!
I mentioned the Adjustable Powersupply for a couple reasons:
- I need 3.7v to run the camera (adjustable)
- input voltages could run from 3 to 6 volts
- the kit looks doable for my level of skill and understanding (I had to look up what an LDO was)
- the kit was in-stock and in my price range
- the kit looks small enough to fit in my enclosure
I'm pretty much a noob when it come to electronics, so if anyone wants to mention or present me a stand-alone or simpler LDO setup, I'd love to entertain it.
I know that the 'Adjustable' is a breadboard setup, but it looks hackable enough for my purposes.
Thanks for any input!
- adafruit_support_mike
- Posts: 68231
- Joined: Thu Feb 11, 2010 2:51 pm
Re: voltage spike on solar lipo charger
Thank you.. you've made us aware of a non-obvious issue WRT the charger. Through sheer good luck, you were powering a device smart enough to shut down when given too much voltage, but the same setup could possibly damage more fragile 3.3v (or 5v) devices.bwh13 wrote:thanks for that. a way forward!
It would work, and it's a nice piece of gear, but it's overkill for this specific situation.bwh13 wrote:1) would something like the "Adjustable breadboard power supply kit - v1.0" http://www.adafruit.com/products/184 be a workable solution?
Regulating voltage is such a common job that there are thousands of chips to do the job for you. It's also so common that circuit designers don't want to futz around with compicated subcircuits, they just want to plug in a single low-cost part and get on with their day.
For a LiPo-driven circuit, the input you really want is 3.3v, and you don't want to waste a lot of power getting that. This chip from ST Microelecronics: http://www.mouser.com/ProductDetail/STM ... eP2qVDA%3d gives you 3.3v at up to 1.3A, and can provide full power from a 4.4v input supply. It has three pins: input voltage, output voltage, and GND. You do need a couple of capacitors to go with it, but the total parts cost would be about a dollar (The LD1117V33 costs 55c if you buy a single one).
Yep. Connect the solar charger to the 'input voltage' and 'GND' pins, and the camera to the 'output voltage' and 'GND' pins. It's really that simple.bwh13 wrote:2) in your last line, the part about the 'battery-replacement circuit/adaptor.' Do you mean something to the effect that I would want to install this low-drop regulator on the 'load' side of the lipo charger?
If you want the breadboard regulator, go for it.. like i said, it's a nice piece of equipment, and you'll get good use from it for years. If you want to go with something dedicated, we'll help you get that working too (even if we don't sell the parts).
- bwh13
- Posts: 15
- Joined: Thu May 23, 2013 6:15 pm
Re: voltage spike on solar lipo charger
-mike-
thanks for the discussion - I got a lot out of it. you folks do a great service by encouraging us.
Adjustable Power Supply Overkill: I did some homework over the weekend and you are completely right. It also turns out that I ordered a breadboard and supplies from you folks, because I decided that I had to build the circuit myself. I'm pretty psyched to do it, actually. That adjustable supply will come in handy!
3.3v: The LDO you posted had a dropout of 1v. So that means I would have to supply 4.3 to get that. That won't be a problem when the sun is shining and the panel is putting out 5+ volts, but when it switches to battery supply (i.e. cloudy day, night time) the battery voltage will probably work it's way down to 3.7 (it's nominal rating.) So with my novice's understanding, I wouldn't necessarily be able to push 3.3v out to my device (the camera.) Is that correct?
I'm guessing that there are LDOs with smaller dropouts...I haven't done all my homework yet. I could also get the 'adjustable' LDO and use a trim pot. to get a voltage a bit higher than the 3.3v (to make the camera happy -> more homework to do there.)
Thanks again for all the encouragement!
thanks for the discussion - I got a lot out of it. you folks do a great service by encouraging us.
Adjustable Power Supply Overkill: I did some homework over the weekend and you are completely right. It also turns out that I ordered a breadboard and supplies from you folks, because I decided that I had to build the circuit myself. I'm pretty psyched to do it, actually. That adjustable supply will come in handy!
3.3v: The LDO you posted had a dropout of 1v. So that means I would have to supply 4.3 to get that. That won't be a problem when the sun is shining and the panel is putting out 5+ volts, but when it switches to battery supply (i.e. cloudy day, night time) the battery voltage will probably work it's way down to 3.7 (it's nominal rating.) So with my novice's understanding, I wouldn't necessarily be able to push 3.3v out to my device (the camera.) Is that correct?
I'm guessing that there are LDOs with smaller dropouts...I haven't done all my homework yet. I could also get the 'adjustable' LDO and use a trim pot. to get a voltage a bit higher than the 3.3v (to make the camera happy -> more homework to do there.)
Thanks again for all the encouragement!
- bwh13
- Posts: 15
- Joined: Thu May 23, 2013 6:15 pm
Re: voltage spike on solar lipo charger
Hi All,
I just measured the outgoing voltage on the solar lipo charger (i.e. the 'Load' side) and under full-sun conditions (and pointed at the sun like a tracker) and I was getting about 6.8 volts with a voltmeter. It's the 'medium' 6V 2W panel from the store. My camera was logging ~~5.8v, so it looks like there might be some circuitry that uses some of that and drops it down before the voltage is even logged.
With regards to a LDO and what voltage to set it at: I've read and been told that most 3.7v batteries will start at ~~4.1v and transition down to the rated range. The cameras I'm running operate in the 4.1 - 3.7 volt range, and I need to regulate ~~6.8 incoming volts down to this range, so my question is: when the incoming 'Load' voltage transitions from feeding directly from the solar panel (6.8 v) to coming from the LiPo battery (3.7v +) is the LDO still going to skim some voltage off the top (i.e. equal the dropout voltage?)
Said another way, does incoming voltage at or beneath the regulated level still get taxed by the dropout voltage?
Thanks!
I just measured the outgoing voltage on the solar lipo charger (i.e. the 'Load' side) and under full-sun conditions (and pointed at the sun like a tracker) and I was getting about 6.8 volts with a voltmeter. It's the 'medium' 6V 2W panel from the store. My camera was logging ~~5.8v, so it looks like there might be some circuitry that uses some of that and drops it down before the voltage is even logged.
With regards to a LDO and what voltage to set it at: I've read and been told that most 3.7v batteries will start at ~~4.1v and transition down to the rated range. The cameras I'm running operate in the 4.1 - 3.7 volt range, and I need to regulate ~~6.8 incoming volts down to this range, so my question is: when the incoming 'Load' voltage transitions from feeding directly from the solar panel (6.8 v) to coming from the LiPo battery (3.7v +) is the LDO still going to skim some voltage off the top (i.e. equal the dropout voltage?)
Said another way, does incoming voltage at or beneath the regulated level still get taxed by the dropout voltage?
Thanks!
- bwh13
- Posts: 15
- Joined: Thu May 23, 2013 6:15 pm
Re: voltage spike on solar lipo charger
So I've been working out this LDO: it is a Texas Instruments LP3964. So far, it has a really low dropout voltage (24mV @ 80mA).
I've wired up the circuit here (according to specs on the datasheet) and removed the jumper wires for clarity. It's a really simple circuit (I pretty much just learned how to read circuit diagrams since my last post.) I've been using the adjustable power supply to simulate the higher voltages that I was getting with the solar lipo board, and it's working really well.
The regulator had staggered and bent leads that (looked really cool, but) were not breadboard friendly. They can be reshaped, but if you reshape them too much, they break. Good thing I had the foresight to buy 2. I'm going to solder it all together on a perma-proto board next and hook the panel and the camera up for some field tests. I'll update then.
I've wired up the circuit here (according to specs on the datasheet) and removed the jumper wires for clarity. It's a really simple circuit (I pretty much just learned how to read circuit diagrams since my last post.) I've been using the adjustable power supply to simulate the higher voltages that I was getting with the solar lipo board, and it's working really well.
The regulator had staggered and bent leads that (looked really cool, but) were not breadboard friendly. They can be reshaped, but if you reshape them too much, they break. Good thing I had the foresight to buy 2. I'm going to solder it all together on a perma-proto board next and hook the panel and the camera up for some field tests. I'll update then.
Please be positive and constructive with your questions and comments.