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TheLounge is fantastic. I've got it on a pi in the basement on a battery, and I just VPN into home from anywhere. Been running 3-ish years I think. It works su

TheLounge is fantastic. I've got it on a pi in the basement on a battery, and I just VPN into home from anywhere. Been running 3-ish years I think. It works surprisingly well from mobile browsers, too.

HumblyTossed 2y ago
> I've got it on a pi in the basement on a battery, and I just VPN into home from anywhere. Been running 3-ish years I think. That's a _really_ good battery!
- universa1 2y ago
  or maybe he just put it on top of the battery? ;-)
- myself248 2y ago
  Yeah, that's an oversimplification. It's a rack with a bunch of ports to plug in whatever 12-volt batteries aren't currently in use elsewhere. So when I retire one from the car, or a solar experiment, or replace a whole pile of 'em from a UPS and most are kaput but a few are still viable, they all end up on that rack, in parallel. (With fuses and stuff, of course. And I precharge each battery so it closely matches the float voltage before plugging it in.) Presently I think there's like 30-40 amp-hours worth of lead and lithium sitting there, all charged by a little Meanwell RS-25-12 or something. I don't exactly remember, but the photo looks familiar. (25 watts at 12 volts tweaked up to 13.85 volts, so, roughly 2 amps.) That powers the cable modem, wifi router, service pi, and a RIPE ATLAS probe. The first two eat 12-ish volts and have SMPS input stages so they're not picky about the -ish, so they just run directly from the battery rail. The latter two have DC-DC converters feeding them (the venerable MC34063 or something similar). Combined, their draw is just shy of an amp at 12 volts, so the rack with its current fleet of batteries can run several days with no AC input. Realistically if power fails, I usually start the generator after just a few hours, so the batteries never actually drain much. If I can find a good place to mount a solar panel that doesn't annoy the landlord, I might be able to unplug the Mean Well and run it independently indefinitely.
  - progval 2y ago
    Don't you also need some sort of battery controller to stop charging batteries once they are full?
    - myself248 2y ago
      Nah, that's what "float" status is all about. There's a voltage where it's safe to let the battery sit indefinitely. Float is less than full-charge peak stress blow-things-up-if-you-stay-here voltage, but IMHO that's to be avoided anyway. So I set the power supply for float, not peak. Furthermore, all the lithiums have a built-in BMS that'll dehance the charge-path FETs if a single cell goes over its cutoff voltage. So even if my power supply were to lose its regulation and attempt to overcharge them, they'd just disconnect themselves. The lead-acids in such an overcharge state would simply convert more of their electrolyte to hydrogen gas and eventually deplete the liquid, but because the power supply is so weak in the first place, it couldn't force that to happen at a problematic rate. The regular drafts and air changes through the house would keep the hydrogen below its LEL unconditionally.
  - tinix 2y ago
    i'd love to hear more about this setup! what kind of rack lets you just jack in 12v batteries with no concern about charge/discharge? what's the spread of their capacities? do you group similar capacity batteries together? somehow and charge/discharge them together? won't nearby large capacity batteries spread/smear their voltage with other batteries on the rail? the smallest batteries will just get obliterated, and the large ones will do the heavy lifting, right? do you have something that disconnects batteries when their voltage drops too low? and does it charge them too? if you put every battery on its own charger, and then use a high/low voltage disconnect, maybe this works, to connect random batteries together on a shared rail... am i overcomplicating this? or is your setup dangerous? are you assuming everything has the same float voltage, and you never need to actually discharge, and then you never charge either? as soon as you go off mains/float voltage, and actually use this battery system, some batteries will deplete faster than others since they have less capacity. are you using it for purely backup purposes only, and not recharging?

HumblyTossed 2y ago

> I've got it on a pi in the basement on a battery, and I just VPN into home from anywhere. Been running 3-ish years I think. That's a _really_ good battery!

universa1 2y ago
or maybe he just put it on top of the battery? ;-)
myself248 2y ago
Yeah, that's an oversimplification. It's a rack with a bunch of ports to plug in whatever 12-volt batteries aren't currently in use elsewhere. So when I retire one from the car, or a solar experiment, or replace a whole pile of 'em from a UPS and most are kaput but a few are still viable, they all end up on that rack, in parallel. (With fuses and stuff, of course. And I precharge each battery so it closely matches the float voltage before plugging it in.) Presently I think there's like 30-40 amp-hours worth of lead and lithium sitting there, all charged by a little Meanwell RS-25-12 or something. I don't exactly remember, but the photo looks familiar. (25 watts at 12 volts tweaked up to 13.85 volts, so, roughly 2 amps.) That powers the cable modem, wifi router, service pi, and a RIPE ATLAS probe. The first two eat 12-ish volts and have SMPS input stages so they're not picky about the -ish, so they just run directly from the battery rail. The latter two have DC-DC converters feeding them (the venerable MC34063 or something similar). Combined, their draw is just shy of an amp at 12 volts, so the rack with its current fleet of batteries can run several days with no AC input. Realistically if power fails, I usually start the generator after just a few hours, so the batteries never actually drain much. If I can find a good place to mount a solar panel that doesn't annoy the landlord, I might be able to unplug the Mean Well and run it independently indefinitely.
- progval 2y ago
  Don't you also need some sort of battery controller to stop charging batteries once they are full?
  - myself248 2y ago
    Nah, that's what "float" status is all about. There's a voltage where it's safe to let the battery sit indefinitely. Float is less than full-charge peak stress blow-things-up-if-you-stay-here voltage, but IMHO that's to be avoided anyway. So I set the power supply for float, not peak. Furthermore, all the lithiums have a built-in BMS that'll dehance the charge-path FETs if a single cell goes over its cutoff voltage. So even if my power supply were to lose its regulation and attempt to overcharge them, they'd just disconnect themselves. The lead-acids in such an overcharge state would simply convert more of their electrolyte to hydrogen gas and eventually deplete the liquid, but because the power supply is so weak in the first place, it couldn't force that to happen at a problematic rate. The regular drafts and air changes through the house would keep the hydrogen below its LEL unconditionally.
- tinix 2y ago
  i'd love to hear more about this setup! what kind of rack lets you just jack in 12v batteries with no concern about charge/discharge? what's the spread of their capacities? do you group similar capacity batteries together? somehow and charge/discharge them together? won't nearby large capacity batteries spread/smear their voltage with other batteries on the rail? the smallest batteries will just get obliterated, and the large ones will do the heavy lifting, right? do you have something that disconnects batteries when their voltage drops too low? and does it charge them too? if you put every battery on its own charger, and then use a high/low voltage disconnect, maybe this works, to connect random batteries together on a shared rail... am i overcomplicating this? or is your setup dangerous? are you assuming everything has the same float voltage, and you never need to actually discharge, and then you never charge either? as soon as you go off mains/float voltage, and actually use this battery system, some batteries will deplete faster than others since they have less capacity. are you using it for purely backup purposes only, and not recharging?