My Vantage Vue ISS suffered the inevitable fate of supercap failure and I got around repeatedly replacing the backup battery by exteriorising and modularising the entire contraption with a separate solar panel that charged a 12V battery which I then dropped to 3.3V and fed into the backup battery terminals (see previous posts). Worked well for 4 years now...until the ISS built-in solar panel failed a month ago.
So the system relied on the little solar panel to power the ISS during daylight, and the external battery to power it at night (no supercap power is available). Daylight also charged this external battery.
Problem: the external battery cannot be charging and discharging concurrently (it cannot feed the ISS while it is charging itself).
I had to find a replacement for the ISS solar panel power to allow the external battery to charge during the day and power the ISS at night.
Solution: 5V lithium power bank charged by a low voltage solar panel!
So I threw out the old solar panel (17V open circuit voltage to charge the 12V lead acid battery through a solar regulator) and installed a similar sized 6.2 V solar panel...perfect for charging a 5V lithium -ion power bank.
Since the new solar panel has so much more capacity than is needed to charge the li-ion power bank, I split the solar output to feed the ISS as well. I simply unscrewed the terminals off the ISS little solar panels and diverted the leads to receive solar power.
Well those are the basic principles of its operation; it needs a few details filled in.
1. The solar panel output varies, and goes up to about 6.8V in bright sunlight. I used a 3.3V voltage regulator to give the ISS a voltage it can safely work with.
2. I attached a 1000uF capacitor across the voltage regulator output to smooth the fluctuations in solar supply.
3. The power bank receives the solar panel power directly for charging. It has protective circuitry that allows it to accept a good range of input voltages.
4. The output from the power bank is 5V. Once again, I dropped this down to 3.3V with a voltage regulator and fed it into the CR123 battery terminals. A new CR123 battery coincidentally happens to be 3.3V
5. The ISS is designed to only use the backup battery when there is no solar power so the li-ion battery only kicks in at sunset.
6. I found that the best powerbank is the one that has no button to manually turn on; it needs to kick in automatically when the solar panel isn't feeding the ISS. Most power banks are designed to turn off when there is minimal draw from them and the ISS uses precious little power which is not enough to keep the USB output active. This is a problem esp around dawn and dusk when there is a "handover" of sorts from one source to the next; it is not a binary state of either this or that source of power so both need to be available for the ISS to choose from.
7. The system works well in the "bench test" phase of my experimentation. I'm mulling over whether I should install a supercap across the solar panel outputs to smooth AND supply the Li-ion battery as well as the ISS. Not necessary right now because it works well without this modification.
8. The voltage regulators I used are LM3940IT-3.3 in a TO220 package. These things are not very energy efficient, but since the draw through them is so low, and the voltage drop is so minimal (5V to 3,3V for one and 6.8V to 3.3V for the other) they don't dissipate any heat whatsoever.
Hope it helps!
So the system relied on the little solar panel to power the ISS during daylight, and the external battery to power it at night (no supercap power is available). Daylight also charged this external battery.
Problem: the external battery cannot be charging and discharging concurrently (it cannot feed the ISS while it is charging itself).
I had to find a replacement for the ISS solar panel power to allow the external battery to charge during the day and power the ISS at night.
Solution: 5V lithium power bank charged by a low voltage solar panel!
So I threw out the old solar panel (17V open circuit voltage to charge the 12V lead acid battery through a solar regulator) and installed a similar sized 6.2 V solar panel...perfect for charging a 5V lithium -ion power bank.
Since the new solar panel has so much more capacity than is needed to charge the li-ion power bank, I split the solar output to feed the ISS as well. I simply unscrewed the terminals off the ISS little solar panels and diverted the leads to receive solar power.
Well those are the basic principles of its operation; it needs a few details filled in.
1. The solar panel output varies, and goes up to about 6.8V in bright sunlight. I used a 3.3V voltage regulator to give the ISS a voltage it can safely work with.
2. I attached a 1000uF capacitor across the voltage regulator output to smooth the fluctuations in solar supply.
3. The power bank receives the solar panel power directly for charging. It has protective circuitry that allows it to accept a good range of input voltages.
4. The output from the power bank is 5V. Once again, I dropped this down to 3.3V with a voltage regulator and fed it into the CR123 battery terminals. A new CR123 battery coincidentally happens to be 3.3V
5. The ISS is designed to only use the backup battery when there is no solar power so the li-ion battery only kicks in at sunset.
6. I found that the best powerbank is the one that has no button to manually turn on; it needs to kick in automatically when the solar panel isn't feeding the ISS. Most power banks are designed to turn off when there is minimal draw from them and the ISS uses precious little power which is not enough to keep the USB output active. This is a problem esp around dawn and dusk when there is a "handover" of sorts from one source to the next; it is not a binary state of either this or that source of power so both need to be available for the ISS to choose from.
7. The system works well in the "bench test" phase of my experimentation. I'm mulling over whether I should install a supercap across the solar panel outputs to smooth AND supply the Li-ion battery as well as the ISS. Not necessary right now because it works well without this modification.
8. The voltage regulators I used are LM3940IT-3.3 in a TO220 package. These things are not very energy efficient, but since the draw through them is so low, and the voltage drop is so minimal (5V to 3,3V for one and 6.8V to 3.3V for the other) they don't dissipate any heat whatsoever.
Hope it helps!
