Hello /diy/nasours
I wish to create a bunch of ups systems so that networking equipment can continue to work during a power outage.
All UPS' will have 2 lantern batteries in series to make 12 volts, however not all equipment will work on 12v, eg switches running on 5v.
I plan on using 5v buck regulators to regulate down the voltages of the batteries however I am unsure how I will do this with my (well, "modified") design, because right now I am tempted to make them all 12v systems with regulators just chucked on the output.
I may have to include multiple voltage outputs on each ups to power different pieces of hardware (12v access point, and 5v switching hub). May I just use 12v 2a power supplies and down regulate to suit my needs?
P-type mosfet is used as batteries will have an above 12b starting voltage.
OP here
Must remind you that the batteries are disposable and are non rechargeable.
Are they safe for use in this circuit?
>>910873
>>910874
Why would you waste money on throw away batteries? For less than $20, you can buy small, sealed, maintenence free 12v lead acid batteries...for things like UPS' and alarm systems. You top the charge off once a month with a cheap car charger.
Why would you waste energy bucking voltage from 12v down to 5v? Build a dedicated UPS for 5v stuff. Could use 6v battery of same type I mentioned above. Might not even need to buck it down to 5v, but if you had to, your wasting less energy.
>tl;dr...use sealed lead acid batteries you can recharge. Theyre cheap as chips.
>>910886
Cost reduction, the lantern batteries are 3 to 4 quid each.
I can eventually upgrade them to lithium ion cells in the future. A single 18650 cell is the same price as a 6v lantern battery.
>>910886
Actually, I was planning on using lead acid. But I've noted that they are very fussy with being over discharged (so are li-ion) but the protection for pb batteries are quite costly compared to li-ion protection.
I don't need to worry about over discharging disposable batteries.
>>910894
For ease of maintenece, due to car charger, 12v LA is really the way to go, especially when considering Ah ratings.
Assuming they contain F cells:
Standard Duty (Zinc-Carbon): 7 - 7.5 Ah (depending on brand)
Heavy Duty (Zinc-Carbon): 8 - 10 Ah (depending on brand)
Super Heavy Duty (Zinc-Chloride): ~ 11 Ah
Alkaline: 24 - 26 Ah (depending on brand)
Look for 4LR25 (F cell) on the side, not 4LR20 (D cell).
Now, assuming youre talking about old school zinc-carbon, than 12v LA is definitely the way to go for, what, maybe 5 quid more?
The 6v batteries will be wired in series, therefor, Ah rating doesnt double. If youre going for an alkaline 6v, than Ah rating will be more than small 12v la "alarm type" batteries. But I imagine the 6v alkaline are more money too.
Li-Ion would be nice...just be careful. Personally, I would not charge a "pack", but would individually charge each cell. But thats just me being paranoid.
>>910898
crap....sorry for tripcode
>>910898
Right, lead acid is on the table.
Just need reliable chargers with real float charging of lead acid batteries.
Yeah, li-ion will be another thread all together. With balancing and voltage cut offs and what not. Actually might get onto that later on.
So, I've got a good insight about back up power choices.
Just need confirmation that that circuit will work as long as all components have the correct ratings, ie rated for 2 amps @ 12v. Because all ups units will be manufactured the same. But will allow for interchangeable batteries and power supplies.
>>910898
Also cheers for the insight on battery capacity of the different chemistries. Will come in handy.
>>910873
The transistor symbol is wrong. You won't find zener diodes inside MOSFETs.
>>911515
Well, it's a p channel mosfet. That's as much as I've gathered.
I don't know how or why it works. But I think I know it does work. I will make a horrible engineer. Better of going down the electrician path.
I'll get the datasheet for the ones I've ordered.
>>911515
Here we are
http://www.irf.com/product-info/datasheets/data/irf9540.pdf
I only just learned about their existence today. Function like inverted relays.
>>911515
Unfortunately you are wrong.
Some early mosfets did infact have an internal zener diode across the drain and source.
Zener diodes are also a misused tern, as this effect is not relevant for diodes with a forward breakdown voltage of more than ~6.3V as the effect then is due to avalanche, hence the name avalanche diodes.
ALL mosfet have an instinct diode across the drain to source, the body diode, this diode will conduct when the device is reversed biased, but the mosfet will also enter avalanche (conduct current) if the blocking voltage is exceeded.
Today nearly all mosfets is avalanche rated, and can withstand a short event of overvoltage, where it will avalanche. In the good old days mosfets were not a mature technology, and the avalanche voltage were not well defined, therefor some manufactures added an additional avalanche diode or zener diode if you want, across the device.
