Which did you see that supports beyond 4 in series? I would be interested
to check those out.
125*3.65vpc= 456v
I guess you need 125 if your running at nominal voltage (partial state of
charge)
On Thu, Aug 17, 2023, 2:35 PM Mathew Howard <mhoward...@gmail.com> wrote:
> I put four of the sealed 12v lifepo4 batteries in an electric lawn mower
> (it originally had lead acid), and it works well enough, but yeah, a single
> BMS is preferable, and I haven't seen any that say they can do more than 4
> in series anyway.
>
> With lifepo4 you'll need 125 cells to get 400v... I'm not sure where you'd
> find a BMS that will handle that though. I assume there must be something
> out there.
>
> On Thu, Aug 17, 2023 at 4:06 PM TJ Trout <t...@voltbb.com> wrote:
>
>> Many of them have integrated heaters.
>>
>> Sealed lifepo4 batteries should only be used at the nameplate voltage 12v
>> for example, some will support up to four in series for a 48 volt
>> configuration but it's a hack job to do it that way.
>>
>> If you need 400v at 100ah you will need 110 qty of 100ah cells and a
>> compatible BMS.
>>
>> On Thu, Aug 17, 2023, 1:51 PM Chuck McCown via AF <af@af.afmug.com>
>> wrote:
>>
>>> My electric car loses significant range at temps below 35F and as a
>>> double whammy, will not accept a full charge at low temps either.
>>>
>>> Lead acid work at low temps but if they get too far discharged they will
>>> freeze. Gates Cyclons were advertised to be able to be fully charged and
>>> discharged when frozen.
>>>
>>> *From:* Mathew Howard
>>> *Sent:* Thursday, August 17, 2023 2:13 PM
>>> *To:* AnimalFarm Microwave Users Group
>>> *Subject:* Re: [AFMUG] battery nerd question
>>>
>>> Yeah, temperature is the main problem I'm seeing with going to lithiums.
>>> I can throw an SLA battery in an unheated box at our towers and it's going
>>> to work good enough, even in the middle of winter, but the minimum charging
>>> temperature for LFP batteries is 32F, which we're going to be below for a
>>> good part of the year.
>>>
>>> On Thu, Aug 17, 2023 at 3:08 PM Bill Prince <part15...@gmail.com> wrote:
>>>
>>>> Things have evolved. You can get LFP batteries for "almost" the same
>>>> price as lead acid. Sometimes less even. They occupy less than half the
>>>> space as lead acid, and will last at least twice as long. There is the
>>>> issue of temperature sensitivity and they will need help for extremely cold
>>>> environments.
>>>>
>>>>
>>>>
>>>> bp
>>>> <part15sbs{at}gmail{dot}com>
>>>>
>>>> On 8/17/2023 12:36 PM, dmmoff...@gmail.com wrote:
>>>>
>>>> Ooh What lithium batteries are we talking about?
>>>>
>>>> Last time I checked (a number of years ago), it was around 5x the $/Wh
>>>> to buy Lithium.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> *From:* AF mailto:af-boun...@af.afmug.com *On Behalf Of *Mathew Howard
>>>> *Sent:* Thursday, August 17, 2023 10:51 AM
>>>> *To:* AnimalFarm Microwave Users Group mailto:af@af.afmug.com
>>>> *Subject:* Re: [AFMUG] battery nerd question
>>>>
>>>>
>>>>
>>>> Well, right. It doesn't scale well, because battery costs and space
>>>> requirements will quickly become a problem. Batteries don't last forever,
>>>> so you have to factor in replacement costs too, which will be a significant
>>>> ongoing cost for a larger system. I'm pretty sure that lithium batteries
>>>> would be cheaper long term now, since they should have a lot longer life
>>>> span and the initial cost isn't a lot higher, but then heating is required,
>>>> which means you need more power.
>>>>
>>>>
>>>>
>>>> On Wed, Aug 16, 2023 at 7:02 PM <dmmoff...@gmail.com> wrote:
>>>>
>>>> That’s building strictly for a 20W load though. Building for a tiny
>>>> load does make the costs easier. But if you wanted a second AP, bigger
>>>> backhaul, or anything else you can’t do it without growing the whole power
>>>> system proportionally.
>>>>
>>>>
>>>>
>>>> Steve was talking a 50W load today. The real high end hardware now is
>>>> using a lot of signal processing either to reassemble useful data out of
>>>> garbage or for beam steering, or both. So you end up needing 100-150W for
>>>> an AP. You’d be hard pressed to find a licensed backhaul under 35W, and
>>>> most of them are 50W+. We could say we won’t deploy that equipment….but
>>>> building for a 20W load takes the choice away.
>>>>
>>>>
>>>>
>>>> A 20A 240v circuit is 4800W. Or a 20A 120V circuit is 2400W. Even
>>>> 2400W would power almost any WISP deployment. Building solar to handle any
>>>> load you might have is expensive, and building for only low power handcuffs
>>>> you.
>>>>
>>>> You do your thing your way, no judgement. If it’s working for you then
>>>> it’s good, but I can’t see myself going that direction.
>>>>
>>>>
>>>>
>>>> -Adam
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> *From:* AF <af-boun...@af.afmug.com> *On Behalf Of *Mathew Howard
>>>> *Sent:* Wednesday, August 16, 2023 5:01 PM
>>>> *To:* AnimalFarm Microwave Users Group <af@af.afmug.com>
>>>> *Subject:* Re: [AFMUG] battery nerd question
>>>>
>>>>
>>>>
>>>> I'm at about the same latitude as you. My experience is that having
>>>> extra battery capacity is more helpful than oversizing the solar panels, so
>>>> I'd probably go with Chuck's numbers for batteries if I was putting
>>>> something together now, and solar panels are cheap now anyway, so figure
>>>> 400 watts (if mounting space allows for it, which could be an issue if
>>>> we're trying to fit it on a pole).
>>>>
>>>>
>>>>
>>>> A quick check on Amazon shows 100ah SLA batteries for $160, so 6 of
>>>> those would give me 7200 watt hours, for just under $1k. At $1500 (which is
>>>> mostly just adjusting battery and panel sizes from where I started at $1k),
>>>> I'm right in line with Chuck's estimate, aside from the battery costs.
>>>>
>>>>
>>>>
>>>> On Wed, Aug 16, 2023 at 3:33 PM <dmmoff...@gmail.com> wrote:
>>>>
>>>> I end up closer to Chuck’s estimate. In Southern or Central NY State
>>>> I’m 2 degrees north of Salt Lake City. 42N
>>>>
>>>> What’s your latitude?
>>>>
>>>>
>>>>
>>>> *From:* AF <af-boun...@af.afmug.com> *On Behalf Of *Mathew Howard
>>>> *Sent:* Wednesday, August 16, 2023 4:11 PM
>>>> *To:* AnimalFarm Microwave Users Group <af@af.afmug.com>
>>>> *Subject:* Re: [AFMUG] battery nerd question
>>>>
>>>>
>>>>
>>>> Yeah, that's what I'd do in a difficult to access location. I did a
>>>> site like that here (Wisconsin) with 200 watts of panel (I think the actual
>>>> load is around 15 watts, so a bit more than 10x), and ~4kwh of battery. It
>>>> had some issues in January a couple years, but I attributed that more to
>>>> using cheap flooded deep cycles, rather than not enough capacity. With
>>>> AGMs, it's gotten through the last couple of winters without issues. 4kwh
>>>> of AGMs can be had for around $800, last I checked. Probably looking at
>>>> closer to $1500 when you add in enclosures and mounts, but some of that is
>>>> replacing parts that are needed with AC power anyway (smaller enclosure,
>>>> backup batteries, power supply), so that offsets it a bit.
>>>>
>>>>
>>>>
>>>> On Wed, Aug 16, 2023 at 2:50 PM Chuck McCown via AF <af@af.afmug.com>
>>>> wrote:
>>>>
>>>> Using my historical rules of thumb for off grid, snowed in mountain top
>>>> location for a 20 watt load I would do the following that has never failed
>>>> me:
>>>>
>>>>
>>>>
>>>> Load X 20 so 400 watts of panel. So less than $200 these days.
>>>>
>>>> 2 weeks of battery autonomy.
>>>>
>>>> 20 x 24 x 14= 6720 watt hours. $2K of batts
>>>>
>>>> Plus enclosures, mounts, charge controllers.
>>>>
>>>>
>>>>
>>>> $2500 and it will never go down in the winter. At my Utah latitude on
>>>> top of Utah mountains.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> *From:* Mathew Howard
>>>>
>>>> *Sent:* Wednesday, August 16, 2023 1:07 PM
>>>>
>>>> *To:* AnimalFarm Microwave Users Group
>>>>
>>>> *Subject:* Re: [AFMUG] battery nerd question
>>>>
>>>>
>>>>
>>>> It depends on how much stuff you're trying to run. A minimal micropop
>>>> can be done with less than 20 watts of load (single AP and backhaul). I can
>>>> put together a solar setup for around $1000 that will power that.
>>>>
>>>>
>>>>
>>>> On Tue, Aug 15, 2023 at 12:50 PM <dmmoff...@gmail.com> wrote:
>>>>
>>>> I can save you the suspense. If you have access to electric that’ll be
>>>> cheaper than solar. The problem is the need to run 24/7. You have to
>>>> design around the December-January months. I’m in NY State, and at our
>>>> latitude we only get a few hours of average production per day during those
>>>> months. And obviously if it’s snowing for a week you need to be able to
>>>> ride through that on mostly battery power. Even with a modest load it
>>>> takes a silly amount of panels and batteries to stay up 24/7 in the
>>>> winter. More than you’d ever be allowed to put on a utility pole.
>>>>
>>>>
>>>>
>>>> Talk to your electric co about the smallest service you can get.
>>>> Explain what you’re trying to do and that your max load is very low.
>>>>
>>>> NYSEG normally doesn’t do less than 100A, but they made an exception
>>>> and let us do 60A. You need a meter can, a service rated panel, a conduit
>>>> up the pole and a weatherhead. Then you either have an outdoor outlet, or
>>>> have an outlet inside your enclosure. You’ll want the smallest service
>>>> they’ll let you do because of the wire size on the service cable. A 20A
>>>> (if they’d allow it) would only need a 12/3 with ground, and that’s up to
>>>> 4800 Watts (240x20) so it’s still more than you’d ever need. A 12/3 is
>>>> way cheaper than a 100A service entrance cable.
>>>>
>>>>
>>>>
>>>> My figure is 8 years old, and obviously there’s been inflation since
>>>> then, but I went to the same contractor who does electric installs for the
>>>> cable company and they quoted me about $1000. Even if it’s 3x that for you
>>>> today you’d still never beat that with a solar installation even if they’d
>>>> let you do it. And I’m not some knee-jerk anti-solar lunatic, I’m just
>>>> saying I’ve run the numbers and it doesn’t add up. People do it when
>>>> they’re off grid, or when the electric service is unreliable in the area,
>>>> or sometimes just for the PR/marketing power of being “solar powered”.
>>>> Those are all fine reasons, but doing it for cost savings isn’t going to
>>>> work out.
>>>>
>>>>
>>>>
>>>> -Adam
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> *From:* AF <af-boun...@af.afmug.com> *On Behalf Of *Steve Jones
>>>> *Sent:* Tuesday, August 15, 2023 10:27 AM
>>>> *To:* AnimalFarm Microwave Users Group <af@af.afmug.com>
>>>> *Subject:* Re: [AFMUG] battery nerd question
>>>>
>>>>
>>>>
>>>> we have a dozen or so, but are looking at pole mount micropops (our own
>>>> poles). We are losing a grain elevator site because they decommissioned the
>>>> elevator and theres no real options for the customers in some of the areas.
>>>> Im just trying to get to something we can get solar power with enough
>>>> battery to last through overcast. So Im calculating per battery runtimes,
>>>> then will look at number of batteries we would need to survive vs paying
>>>> for a ROW meter vs losing the customers. Just have to get to the cost per
>>>> customer to retain them and the benefit gained per pole
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Tue, Aug 15, 2023 at 8:53 AM Brian Webster <i...@wirelessmapping.com>
>>>> wrote:
>>>>
>>>> How many of the batteries do you have? Do you need any voltages other
>>>> than the 48 volts? If you have 4 batteries and only need 48 volts then wire
>>>> them in series and not have to deal with the converter.
>>>>
>>>>
>>>>
>>>> Thank you,
>>>>
>>>> Brian Webster
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> *From:* AF [mailto:af-boun...@af.afmug.com] *On Behalf Of *
>>>> dmmoff...@gmail.com
>>>> *Sent:* Tuesday, August 15, 2023 6:59 AM
>>>> *To:* 'AnimalFarm Microwave Users Group'
>>>> *Subject:* Re: [AFMUG] battery nerd question
>>>>
>>>>
>>>>
>>>> *You’re around C/30 which should be on the high end *of capacity*.
>>>>
>>>> Lower load usually means a little extra capacity out of the battery. I
>>>> realized that sentence might have been ambiguous.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> *From:* dmmoff...@gmail.com <dmmoff...@gmail.com>
>>>> *Sent:* Tuesday, August 15, 2023 6:56 AM
>>>> *To:* 'AnimalFarm Microwave Users Group' <af@af.afmug.com>
>>>> *Subject:* RE: [AFMUG] battery nerd question
>>>>
>>>>
>>>>
>>>> You can do the whole thing in Watts.
>>>>
>>>>
>>>>
>>>> 12V * 150ah = 1800 Watt-hours
>>>>
>>>> 1800Wh / 50W = 36 hours
>>>>
>>>>
>>>>
>>>> If they’re telling me 95% efficiency, I’d assume 50W out needs 53W in
>>>> (50 / 0.95).
>>>>
>>>> There’s usually an efficiency curve for the device based on load and
>>>> temperature so it wouldn’t be 95% in all circumstances. Your system should
>>>> be drawing less than 5A off the battery, and if your multimeter has a 10A
>>>> fuse like most do, then you could put the meter in line and actually
>>>> measure the amperage before and after the converter. Then you’d know for
>>>> sure.
>>>>
>>>>
>>>>
>>>> And the battery’s total capacity will have a curve based on C-rate so
>>>> there’s some variability there too. Usually it lasts longer when you’re
>>>> drawing lower amperage. You’re around C/30 which should be on the high
>>>> end.
>>>>
>>>>
>>>>
>>>> Age and maintenance of the battery affect runtime as well. If I want 6
>>>> hours of runtime then I plan Ah for 12 hours runtime. When my batteries are
>>>> halfway toasted I’m still getting useful life out of them.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> *From:* AF <af-boun...@af.afmug.com> *On Behalf Of *Steve Jones
>>>> *Sent:* Monday, August 14, 2023 9:57 PM
>>>> *To:* AnimalFarm Microwave Users Group <af@af.afmug.com>
>>>> *Subject:* [AFMUG] battery nerd question
>>>>
>>>>
>>>>
>>>> Just trying to cipher runtimes
>>>>
>>>> I have on hand 150ah 12 volt batteries, so thats what id be looking to
>>>> use.
>>>>
>>>> Excluding the conversion loss of a 12v to 48v step up converter is the
>>>> math correct here?
>>>>
>>>> 12v 150ah=1800 watt hours
>>>> 1800 watt hours at 48v = 37.5ah
>>>> 50 watts of radio running 48v = 1.04 amps
>>>> 37.5ah @ 1.04 amps = 32.77 hours runtime
>>>>
>>>>
>>>>
>>>> does a step up that claims 95% efficiency mean 95% of the watt hours?
>>>>
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