[Battlemesh] Battery recommendations for TP-Link TL-WR703N under solar?

Fri Nov 15 04:38:34 UTC 2013

Hi Ben,

On Fri, Nov 15, 2013 at 2:55 PM, Ben West <ben at gowasabi.net> wrote:

> Hello Battlemesh,
>
> A recent, sadly abortive, funding application had my mesh network partner
> and I scheming interesting things to do with a fully solar-powered mesh of
> WR703Ns.  These lovely little guys have been described as having only 0.5W
> power consumption, i.e. 100mA at 5V.
>
> Is anyone presently using WR703Ns under solar power?  Would you have
> batteries, panels, and charge circuitry you'd like to recommend?
>

We have a student working on solar charge circuitry that could be used with
these, but it won't be ready for months.  I'd recommend instead using the
MR3040 with its small built-in battery, and possibly swapping the battery
out for a larger one.

Also, you might like to take a look at:

http://developer.servalproject.org/dokuwiki/doku.php?id=content:meshextender:power_consumption_table

We have measured the power consumption of WR703Ns and other devices in
various configurations to get an idea of the real-world power consumption
to be expected.  A bit take-home message is that USB storage is a
significant power drain on such low power devices.  Feel free to add in any
extra data you find.

> My own searching yielded these 6V 12Amp-hour AGM batteries:
> http://www.apexbattery.com/powersonic-ps-6100f2-6v-12ah-battery.html
>
> Likewise this handy schematic for an adaptable 5V DC/DC converter:
> http://www.module.ro/5V-dc-dc%20converter.html
>
> A 10W / 12V solar panel like this one could provide ~500mA of current,
> leaving 400mA or so for trickle charging.  Neglecting whatever
> inefficiencies in the charge controller or the 6V > 5V regulation.
>
> http://www.amazon.com/Instapark%C2%AE-Black-High-Efficiency-Mono-Crystalline-Solar/dp/B004FWW1M4/
>

With the WR3040 and internal battery you could use a $20 50Wh USB power
bank with a circuit that switches the MR3040 to run from the solar panel
when it is developing enough power, and switches it to draw on the battery
otherwise. This would let you use mostly off-the-shelf and noxiously cheap
power banks and USB solar charging systems.

> So, it seems such a 12Ah battery could supply a WR703N for days
> continuously.  This would presumably work well for instances where sunlight
> is scant (e.g. windows in urban environments, polar latitudes), but the
> battery is large and heavy, possibly overkill.
>

120Wh 12V 10Ah LiFePO4 can run WR703N + RFD900 radio + USB hub + USB
storage for about 3 days by our experience.  Expect more days without the
RFD900 radio and USB hub.  Trawl through my blog and the wiki to find more
info about the batteries we used, or just poke me.

> Has anyone else tried the TP-Links with different batteries?
>

See above.

Paul.

> --
> Ben West
> http://gowasabi.net
> ben at gowasabi.net
> 314-246-9434
>
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