That makes sense, I was losing one at just under 22v, but with voltage drop from the cable, it probably would've been 20v at the radio.
I think that's the ideal way to do it, I agree - I want keep running as long as possible, I just don't want to keep draining them once everything is dead, and like Ken said, they drop off pretty fast when they get to that point. If we're talking about something like a solar site where the batteries are being cycled constantly, it would be different, but considering most of these batteries (in our case, anyway) will only ever be cycled 5-10 times over their lifespan, discharging them that low probably isn't going to hurt them that much. On Wed, Dec 2, 2015 at 3:00 PM, Josh Luthman <[email protected]> wrote: > The ePMP sync APs die right at 20 volts FYI. > > In my case I use the regulator as a LVD - it will continue doing 24v until > something like 19 or 20v from the batteries. I'd rather lose some > batteries than have the site go down. > > > Josh Luthman > Office: 937-552-2340 > Direct: 937-552-2343 > 1100 Wayne St > Suite 1337 > Troy, OH 45373 > > On Wed, Dec 2, 2015 at 3:53 PM, Mathew Howard <[email protected]> > wrote: > >> I don't see that there's really a lot of value in running batteries below >> 10.5 volts or so, at that point the voltage is going to be low enough that >> a lot of radios aren't going to run anyway (for example, ePMPs will die >> just a little under 22v), which means your going to just be wearing out the >> batteries for nothing. >> >> One time I had a Mikrotik router lock up after a power outage - >> apparently, when the voltage dropped to low (and all the radios had long >> since died), the Mikrotik locked up, but it never actually got low enough >> for it to completely shut down, so when the power came back on, it stayed >> in it's locked up state until I went out there and unplugged it. it >> would've saved me a trip out there if there had been an LVD on the >> batteries. >> >> On Wed, Dec 2, 2015 at 2:12 PM, Ken Hohhof <[email protected]> wrote: >> >>> I have anywhere from 2 to 8 x 100Ah AGM batteries at a bunch of sites. >>> That’s a lot of money. They are not throwaways. It does help somewhat >>> that more expensive batteries tend to survive more discharge cycles. >>> >>> But it seems to me from graphs that once you get down to 11 volts, it >>> declines pretty rapidly from there. I could be wrong, but I don’t think >>> you’re getting that much extra runtime continuing to drain the batteries >>> below let’s say 10.5 volts. >>> >>> I try to have at least 8 hours of runtime, some sites that are hard to >>> get to in winter more like 2-4 days of runtime. The idea is to bring out a >>> portable generator before the batteries are dead. If you have mountaintop >>> sites, maybe that’s different. >>> >>> Smaller sites we often see zero customers registered while running on >>> batteries because none of them have power or generators. It might make >>> sense to have remote per-radio power control, to shut off the APs but keep >>> the backhauls running for downstream towers. But if they are licensed >>> backhauls, they may consume most of the power anyway. >>> >>> >>> *From:* That One Guy /sarcasm <[email protected]> >>> *Sent:* Wednesday, December 02, 2015 1:56 PM >>> *To:* [email protected] >>> *Subject:* Re: [AFMUG] Calculating battery bank size >>> >>> so how dead does it make the battery for fully discharge, the rhetoric, >>> is run em down, throw them away, is there a rule of thumb for damage? >>> >>> On Wed, Dec 2, 2015 at 12:49 PM, Bill Prince <[email protected]> >>> wrote: >>> >>>> He didn't indicate how the 400 ah were configured. Is it one 12V 400 ah >>>> battery, or one 24v 400 ah battery, etc. But as you noted, once you convert >>>> the battery voltage and amp-hours to watts, it eliminates any confusion. >>>> >>>> If I had 4800 watt-hours of battery (assuming 12V X 4 at 100 >>>> amp-hours), I would estimate 9 hours of run time until the batteries are >>>> dead as a doornail. If you want to use them again (and most people do), >>>> then cut that time in half. >>>> >>>> On the other hand, if you have a 48 volt battery with a 400 amp-hour >>>> rating, then you actually have 19,200 watt-hours of capacity, and you could >>>> multiply the above by 4. >>>> >>>> If you configure the four 12V/100 ah batteries in series, then you >>>> don't have 400 ah, you have 48V/100 ah. The watt-hours are the same. >>>> >>>> bp >>>> <part15sbs{at}gmail{dot}com> >>>> >>>> >>>> On 12/2/2015 10:23 AM, Mathew Howard wrote: >>>> >>>> watt-hours stay the same - 200x24 and 100x48 both equal 4800 watt >>>> hours. In other words, unless you have some horribly inefficient voltage >>>> converters in the mix, it makes little difference. >>>> >>>> On Wed, Dec 2, 2015 at 12:05 PM, Bill Prince <[email protected]> >>>> wrote: >>>> >>>>> wrong. >>>>> >>>>> bp >>>>> <part15sbs{at}gmail{dot}com> >>>>> >>>>> >>>>> On 12/2/2015 10:04 AM, Josh Luthman wrote: >>>>> >>>>> If you do 4x 12v 100ah batteries and do 24v it's twice the time as 48v >>>>> >>>>> Josh Luthman >>>>> Office: 937-552-2340 >>>>> Direct: 937-552-2343 >>>>> 1100 Wayne St >>>>> Suite 1337 >>>>> Troy, OH 45373 >>>>> On Dec 2, 2015 1:01 PM, "Bill Prince" <[email protected]> wrote: >>>>> >>>>>> What voltage? >>>>>> >>>>>> bp >>>>>> <part15sbs{at}gmail{dot}com> >>>>>> >>>>>> On 12/2/2015 10:00 AM, TJ Trout wrote: >>>>>> >>>>>>> >>>>>>> How long will 500w load last on 400ah? >>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>>> >>>> >>> >>> >>> -- >>> If you only see yourself as part of the team but you don't see your team >>> as part of yourself you have already failed as part of the team. >>> >> >> >
