Just put a 12v diode so no current will flow in the router at lower voltages. Not sure though if the box supports flow through charging though.
A power bank will work, I keep a 35Ah SLA in a battery box with a dual UBS and lighter plug. I can run my router, 20" flat screen TV, charge a phone, other batteries and use it as a booster for jump starting cars.
It would be a good idea to measure the current draw of the router if you can
, because if its quite low (250ma or thereabouts) I’d say that 2x18650 would be OK. If the router normally draws close to the full 1A the PSU is rated for, 2 of even the best 18650s wouldn’t last very long. Only maybe 3 hours for a 3400mAh bank.
To be safe, a larger bank might not be a bad idea.
I too thought about using a power bank and 18650 batteries to power routers, switch and ip cameras, but I finally bought a UPS coz it was a simpler solution.
Ive been doing this for a long time. My modem, router, and some strip lighting are powered by a 12v SLA batteries of various sizes over the time with a 100watt ebay boost converter powered off a 12v regulated power supply. I used to have just the 12v regulated power supply going to the batteries and the modem, router, lights but i would have problems with the batteries back feeding into the power supply and draining them far too quickly. Incomes the boost converter, its set to 14v to float charge the batteries and then when the power goes out the diodes in the boost converter stop any back feeding. It works very well. doing it with 18650’s would make for a lot of different challenges to overcome
Guess I’m looking for something simpler like a power bank which takes in 18650 cells and hooks out the DC to the router. Any recommended one that does this? Most of the cheap ebay ones do not charge right and may explode.
For that you are going to need some shenanagains i would assume, as you cant really run 18650s as easily as you can SLA’s, you are going to need to have a way to switch from ac to battery backup quickly enough that the router, and modem don’t shut off, and then a way to automatically charge the batteries again when power comes back. I think first you are going to need to do some measurements, stress the router and modem as best you can and measure the amperage they are drawing.
In most cases, fully automatic instantaneous switch over isn’t really necessary. Nothing wrong with manually switching power cables when the power goes out and comes back on, unless you happened to be in the middle of an intense online gaming session. Unless this is being done for the learning exercise, it isn’t worth the hassle and is not likely to save much money. I just recently picked up a couple of UPSs at Sams Club for $10 that is specifically designed for lower current devices like modems and wifi routers.
APC Back-UPS Connect Network Back-Up BGE70
KuoH
there is no way I would trust this for anything important or even remotely valuable without seeing a teardown
Its understandable to seek out that sort of plug and play functionality, but the losses that happen from converting what im assuming is a small 12v battery to 120v ac to back to what is most commonly 12v dc are rather absurd. What I am running now, is essentially a battery powered router being charged faster than it is being drained, its simple as hell, there is no need for input switching, and I move around and charge cycle the batteries enough that they are not wasting away.
I agree, but the OP is seeking a lithium ion powered solution and as we well know they are not very tolerant of the constant charging regime that your SLA battery setup could easily withstand for several years. That’s why I mentioned the manual plug change or the traditional UPS route. True, it’s not nearly as efficient as direct DC, but it is more flexible as it can run other small 120V devices in a pinch. For instance, I have one running a Homelink garage door relay transmitter as my opener has a backup battery, but my car’s Homelink transmitter is an older version not compatible with the opener. This allowed me to get in the house without getting soaking wet during a particularly strong thunderstorm which took power out to the neighborhood.
KuoH
That battery box does not balance charge, I suspect that it will become wildly unbalanced fairly quickly
From the Aliexpress images of what appears to be the same device, the cells are arranged in 2p3s, likely to get that 21V output without using a boost circuit, but only has 2 wires from the board to the battery. For balance charging, there would need to be more wires to connect to each segment of the 2p cells.
KuoH
It’s the one linked in the thread and the Ebay items don’t show the board. Do you have any links with closeups of the board and / or battery connections? Since you have the device, a couple of good pictures showing the connection details could easily clear this up.
KuoH
I’m thinking of loading this thing with 3 ultrafire unprotected batteries. This should be able to power the router at 1A correct? What does the alternation mean?
Hi!
I’m about to build what you want from this power bank:
As I found out, it cannot be charged and used as a power supply at the same time. Applying input power switches out the output power. So I bought a cheap adjustable step-down (buck) regulator from ebay, adjusted to 4.20V, which fits into the leftover room over the PCB. I also fitted an additional 5.5mm DC input jack. Whenever 5V or more are present here, the regulator will charge with around 11W. As it needs around 17mA without input power, I will use an ideal diode from ebay (still in transit) between it and the batteries to prevent them from slowly discharging.
This way, I can recharge at any voltage (5-30V), and have 12V output at the same time.
If you are interested, I can upload images when I’m finished.
Yes Gauss you got that correct. For my plan to work, the box will constantly be on and supply 12V to the device, but instead of discharging the batteries, it will take the current from the additional charge circuit, which gets 12V from a power supply. Only when the power supply is interrupted, it will take the power from the batteries actually.
During normal operation, there will be about 20% power losses from the 90% efficiency of both the charge circuit and the box electronics.
My ideal diode arrived today, and I just finished the box 1h ago. Here are images:
Here is the step down module:
And the ideal diode:
When charging, the step down module heats to about 65°C over ambient, the diode only 10°C. Therefore I added some tape to the last cell. I also soldered some copper to the module to help dissipate heat. Note that I covered the diode with clear shrink tube. Right now it is charging nicely, I will report back if anything worth noting happens.
Wiring: The additional DC jack is connected to the regulator’s input. I unsoldered the regulator’s LED and connected a blue 3mm LED with the very small wires instead which I mounted in a hole at the side near the DC jack as charge indicator. Not all regulators have LEDs. At the output, negative was connected to the batteries’ negative, and the ideal diode. Also positive regulator output was connected to positive input of the ideal diode. Ideal diode positive output was connected to battery positive.
Good question. But I do not think that there will be a sudden increase in voltage. The output current of the regulator I use is limited to around 3A. A 3A charge current will never make the voltage of 6 18650 cells charged in parallel jump that much. When I first used the regulator the cells were at 3.9V, and after connection to 12V the voltage rose to 4.0V, so that’s 0.1V increase, which should not cause much at the 12V output of the box.
But I will drain the cells overnight and check tomorrow.
It looks like the original switching regulator died overnight while charging when the case was closed and it thus got hotter than before…
I thankfully had another regulator with over-temperature and -current protection:
This one does not nearly get as hot as the original one, but also has around 10W maximum power.
Concerning the low-battery behaviour: As indicated in HJKs test of the box, when the batteries run low, the 12V output voltage is” switched off”, but not really, there is always the cell voltage still present at the output port. If the attached device has a quiescent current at 3V, deep-discharged cells might be the result of a really long power outage. The output power does not come on after the batteries are charged. To make things worse, the box only works again when either charge current over the inteded USB input cable is provided for at least a short time, or the internal reset button is presse.
So it’s not really a UPS for a layman once the batteries have run down.
But as my main goal was to be able to charge off multiple voltage sources, I am satisfied with my mod ( if the new regulator lasts, that is).
Edit: The new regulator also became a little too hot for my liking, so I installed yet another one (CC CV step down regulator) with adjustable output current:
This one now works perfectly even for long charge times without overheating.