Mixing
Can I replace rechargable batteries with (super)capacitors?
Clash Royale CLAN TAG#URR8PPP
up vote
1
down vote
favorite
I need a very small UPS just to give an embedded device time to shut down when power is lost. There are a variety of solutions that use LiPo batteries to provide extended runtime; they typically take USB input and manage both the charging and failover to battery on power loss.
Can I replace a single-cell LiPo (nominal voltage 3.7v) in a charging circuit with a pair of 2.7v supercapacitors wired in series and have it mostly "just work" assuming that (a) there is already some sort of current limiting in place on the charging circuit and (b) I include a passive balancing circuit between the capacitors?
In this situation, I would be under-charging the capacitors (to 3.7v, vs the combined 5.4v capacity in this example). What impact does that have on their behavior?
batteries ups supercapacitor
edited 1 hour ago
laptop2d
22.2k123175
asked 3 hours ago
larsks
1726
add a comment |Â
up vote
1
down vote
favorite
I need a very small UPS just to give an embedded device time to shut down when power is lost. There are a variety of solutions that use LiPo batteries to provide extended runtime; they typically take USB input and manage both the charging and failover to battery on power loss.
Can I replace a single-cell LiPo (nominal voltage 3.7v) in a charging circuit with a pair of 2.7v supercapacitors wired in series and have it mostly "just work" assuming that (a) there is already some sort of current limiting in place on the charging circuit and (b) I include a passive balancing circuit between the capacitors?
In this situation, I would be under-charging the capacitors (to 3.7v, vs the combined 5.4v capacity in this example). What impact does that have on their behavior?
batteries ups supercapacitor
edited 1 hour ago
laptop2d
22.2k123175
asked 3 hours ago
larsks
1726
A LiPo charger may refuse to charge a "dead" (substantially undervoltage) cell, so you may need to replace the charger with something (resistor?) if there isn't enough leakage to get the voltage to the point where the charger considers injecting current safe.
– Chris Stratton
3 hours ago
Keep in mind that, unlike a battery, the voltage on the capacitor will begin to drop the instant you start discharging it. You will need to see how much headroom you have voltage-wise, and also calculate the amount of energy you will need to see if you have enough capacitance to keep the thing up long enough.
– evildemonic
3 hours ago
When contemplating caps instead of batteries, always compare the energy stored vs. volume & weight, because that's most often the deal killer. A 1-farad, 5V capacitor can store 12.5J at 5V. That's roughly the energy equivalent of a LiPo battery with a capacity of 1mAh. You can't find LiPo cells that small!
– TimWescott
59 mins ago
@TimWescott Note that I am explicitly not trying to achieve the same runtime I would get with LiPo batteries. I'm looking for < 60s of runtime, for which I think the caps should be sufficient.
– larsks
51 mins ago
add a comment |Â
up vote
1
down vote
favorite
up vote
1
down vote
favorite
I need a very small UPS just to give an embedded device time to shut down when power is lost. There are a variety of solutions that use LiPo batteries to provide extended runtime; they typically take USB input and manage both the charging and failover to battery on power loss.
Can I replace a single-cell LiPo (nominal voltage 3.7v) in a charging circuit with a pair of 2.7v supercapacitors wired in series and have it mostly "just work" assuming that (a) there is already some sort of current limiting in place on the charging circuit and (b) I include a passive balancing circuit between the capacitors?
In this situation, I would be under-charging the capacitors (to 3.7v, vs the combined 5.4v capacity in this example). What impact does that have on their behavior?
batteries ups supercapacitor
edited 1 hour ago
laptop2d
22.2k123175
asked 3 hours ago
larsks
1726
I need a very small UPS just to give an embedded device time to shut down when power is lost. There are a variety of solutions that use LiPo batteries to provide extended runtime; they typically take USB input and manage both the charging and failover to battery on power loss.
Can I replace a single-cell LiPo (nominal voltage 3.7v) in a charging circuit with a pair of 2.7v supercapacitors wired in series and have it mostly "just work" assuming that (a) there is already some sort of current limiting in place on the charging circuit and (b) I include a passive balancing circuit between the capacitors?
In this situation, I would be under-charging the capacitors (to 3.7v, vs the combined 5.4v capacity in this example). What impact does that have on their behavior?
batteries ups supercapacitor
batteries ups supercapacitor
edited 1 hour ago
laptop2d
22.2k123175
asked 3 hours ago
larsks
1726
edited 1 hour ago
laptop2d
22.2k123175
asked 3 hours ago
larsks
1726
edited 1 hour ago
laptop2d
22.2k123175
edited 1 hour ago
laptop2d
22.2k123175
edited 1 hour ago
laptop2d
22.2k123175
22.2k123175
asked 3 hours ago
larsks
1726
asked 3 hours ago
larsks
1726
asked 3 hours ago
larsks
1726
1726
A LiPo charger may refuse to charge a "dead" (substantially undervoltage) cell, so you may need to replace the charger with something (resistor?) if there isn't enough leakage to get the voltage to the point where the charger considers injecting current safe.
– Chris Stratton
3 hours ago
Keep in mind that, unlike a battery, the voltage on the capacitor will begin to drop the instant you start discharging it. You will need to see how much headroom you have voltage-wise, and also calculate the amount of energy you will need to see if you have enough capacitance to keep the thing up long enough.
– evildemonic
3 hours ago
When contemplating caps instead of batteries, always compare the energy stored vs. volume & weight, because that's most often the deal killer. A 1-farad, 5V capacitor can store 12.5J at 5V. That's roughly the energy equivalent of a LiPo battery with a capacity of 1mAh. You can't find LiPo cells that small!
– TimWescott
59 mins ago
@TimWescott Note that I am explicitly not trying to achieve the same runtime I would get with LiPo batteries. I'm looking for < 60s of runtime, for which I think the caps should be sufficient.
– larsks
51 mins ago
add a comment |Â
A LiPo charger may refuse to charge a "dead" (substantially undervoltage) cell, so you may need to replace the charger with something (resistor?) if there isn't enough leakage to get the voltage to the point where the charger considers injecting current safe.
– Chris Stratton
3 hours ago
Keep in mind that, unlike a battery, the voltage on the capacitor will begin to drop the instant you start discharging it. You will need to see how much headroom you have voltage-wise, and also calculate the amount of energy you will need to see if you have enough capacitance to keep the thing up long enough.
– evildemonic
3 hours ago
When contemplating caps instead of batteries, always compare the energy stored vs. volume & weight, because that's most often the deal killer. A 1-farad, 5V capacitor can store 12.5J at 5V. That's roughly the energy equivalent of a LiPo battery with a capacity of 1mAh. You can't find LiPo cells that small!
– TimWescott
59 mins ago
@TimWescott Note that I am explicitly not trying to achieve the same runtime I would get with LiPo batteries. I'm looking for < 60s of runtime, for which I think the caps should be sufficient.
– larsks
51 mins ago
A LiPo charger may refuse to charge a "dead" (substantially undervoltage) cell, so you may need to replace the charger with something (resistor?) if there isn't enough leakage to get the voltage to the point where the charger considers injecting current safe.
– Chris Stratton
3 hours ago
A LiPo charger may refuse to charge a "dead" (substantially undervoltage) cell, so you may need to replace the charger with something (resistor?) if there isn't enough leakage to get the voltage to the point where the charger considers injecting current safe.
– Chris Stratton
3 hours ago
Keep in mind that, unlike a battery, the voltage on the capacitor will begin to drop the instant you start discharging it. You will need to see how much headroom you have voltage-wise, and also calculate the amount of energy you will need to see if you have enough capacitance to keep the thing up long enough.
– evildemonic
3 hours ago
Keep in mind that, unlike a battery, the voltage on the capacitor will begin to drop the instant you start discharging it. You will need to see how much headroom you have voltage-wise, and also calculate the amount of energy you will need to see if you have enough capacitance to keep the thing up long enough.
– evildemonic
3 hours ago
When contemplating caps instead of batteries, always compare the energy stored vs. volume & weight, because that's most often the deal killer. A 1-farad, 5V capacitor can store 12.5J at 5V. That's roughly the energy equivalent of a LiPo battery with a capacity of 1mAh. You can't find LiPo cells that small!
– TimWescott
59 mins ago
When contemplating caps instead of batteries, always compare the energy stored vs. volume & weight, because that's most often the deal killer. A 1-farad, 5V capacitor can store 12.5J at 5V. That's roughly the energy equivalent of a LiPo battery with a capacity of 1mAh. You can't find LiPo cells that small!
– TimWescott
59 mins ago
@TimWescott Note that I am explicitly not trying to achieve the same runtime I would get with LiPo batteries. I'm looking for < 60s of runtime, for which I think the caps should be sufficient.
– larsks
51 mins ago
@TimWescott Note that I am explicitly not trying to achieve the same runtime I would get with LiPo batteries. I'm looking for < 60s of runtime, for which I think the caps should be sufficient.
– larsks
51 mins ago
add a comment |Â
1 Answer
1
active
oldest
votes
up vote
4
down vote
You could do this, but will it work? The charging circuit will be confused as it is built to charge/discharge at certain voltages. Because lithium ion batteries are considered dead below a certain threshold (like 3.0V) the UPS charging circuit may not switch on at all because a supercapacitor will have no voltage initially.
As far as the capacitor goes, it doesn't matter if it is charged below a threshold, the main thing to worry about is the breakdown voltage (max voltage) and that you don't exceed that rating. It can hold any value between the max voltage and zero.
Source: https://learn.adafruit.com/li-ion-and-lipoly-batteries/voltages
Source: https://www.tecategroup.com/ultracapacitors-supercapacitors/ultracapacitor-FAQ.php
answered 2 hours ago
laptop2d
22.2k123175
add a comment |Â
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
4
down vote
You could do this, but will it work? The charging circuit will be confused as it is built to charge/discharge at certain voltages. Because lithium ion batteries are considered dead below a certain threshold (like 3.0V) the UPS charging circuit may not switch on at all because a supercapacitor will have no voltage initially.
As far as the capacitor goes, it doesn't matter if it is charged below a threshold, the main thing to worry about is the breakdown voltage (max voltage) and that you don't exceed that rating. It can hold any value between the max voltage and zero.
Source: https://learn.adafruit.com/li-ion-and-lipoly-batteries/voltages
Source: https://www.tecategroup.com/ultracapacitors-supercapacitors/ultracapacitor-FAQ.php
answered 2 hours ago
laptop2d
22.2k123175
add a comment |Â
up vote
4
down vote
You could do this, but will it work? The charging circuit will be confused as it is built to charge/discharge at certain voltages. Because lithium ion batteries are considered dead below a certain threshold (like 3.0V) the UPS charging circuit may not switch on at all because a supercapacitor will have no voltage initially.
As far as the capacitor goes, it doesn't matter if it is charged below a threshold, the main thing to worry about is the breakdown voltage (max voltage) and that you don't exceed that rating. It can hold any value between the max voltage and zero.
Source: https://learn.adafruit.com/li-ion-and-lipoly-batteries/voltages
Source: https://www.tecategroup.com/ultracapacitors-supercapacitors/ultracapacitor-FAQ.php
answered 2 hours ago
laptop2d
22.2k123175
add a comment |Â
up vote
4
down vote
up vote
4
down vote
You could do this, but will it work? The charging circuit will be confused as it is built to charge/discharge at certain voltages. Because lithium ion batteries are considered dead below a certain threshold (like 3.0V) the UPS charging circuit may not switch on at all because a supercapacitor will have no voltage initially.
As far as the capacitor goes, it doesn't matter if it is charged below a threshold, the main thing to worry about is the breakdown voltage (max voltage) and that you don't exceed that rating. It can hold any value between the max voltage and zero.
Source: https://learn.adafruit.com/li-ion-and-lipoly-batteries/voltages
Source: https://www.tecategroup.com/ultracapacitors-supercapacitors/ultracapacitor-FAQ.php
answered 2 hours ago
laptop2d
22.2k123175
You could do this, but will it work? The charging circuit will be confused as it is built to charge/discharge at certain voltages. Because lithium ion batteries are considered dead below a certain threshold (like 3.0V) the UPS charging circuit may not switch on at all because a supercapacitor will have no voltage initially.
As far as the capacitor goes, it doesn't matter if it is charged below a threshold, the main thing to worry about is the breakdown voltage (max voltage) and that you don't exceed that rating. It can hold any value between the max voltage and zero.
Source: https://learn.adafruit.com/li-ion-and-lipoly-batteries/voltages
Source: https://www.tecategroup.com/ultracapacitors-supercapacitors/ultracapacitor-FAQ.php
answered 2 hours ago
laptop2d
22.2k123175
edited 2 hours ago
answered 2 hours ago
laptop2d
22.2k123175
answered 2 hours ago
laptop2d
22.2k123175
answered 2 hours ago
laptop2d
22.2k123175
22.2k123175
add a comment |Â
add a comment |Â
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2felectronics.stackexchange.com%2fquestions%2f402800%2fcan-i-replace-rechargable-batteries-with-supercapacitors%23new-answer', 'question_page');
);
Post as a guest
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
A LiPo charger may refuse to charge a "dead" (substantially undervoltage) cell, so you may need to replace the charger with something (resistor?) if there isn't enough leakage to get the voltage to the point where the charger considers injecting current safe.
– Chris Stratton
3 hours ago
Keep in mind that, unlike a battery, the voltage on the capacitor will begin to drop the instant you start discharging it. You will need to see how much headroom you have voltage-wise, and also calculate the amount of energy you will need to see if you have enough capacitance to keep the thing up long enough.
– evildemonic
3 hours ago
When contemplating caps instead of batteries, always compare the energy stored vs. volume & weight, because that's most often the deal killer. A 1-farad, 5V capacitor can store 12.5J at 5V. That's roughly the energy equivalent of a LiPo battery with a capacity of 1mAh. You can't find LiPo cells that small!
– TimWescott
59 mins ago
@TimWescott Note that I am explicitly not trying to achieve the same runtime I would get with LiPo batteries. I'm looking for < 60s of runtime, for which I think the caps should be sufficient.
– larsks
51 mins ago