Re: Building a Raspberry Pi DMR HotSpot

Jerome Kutche

Mark thanks for the detailed info.. I will look at these and try one.. Nice… 73 jerry


PS the fact they do use superior Batteries is impressive..



From: <> On Behalf Of Mark J Culross
Sent: Tuesday, July 10, 2018 9:58 PM
Subject: Fw: [RaspberryPi-4-HamRadio] Building a Raspberry Pi DMR HotSpot


Jerome (& anyone else that may be interested):



Yes, some of the more recent battery packs are specifically designed to allow charging the pack & maintaining the USB outputs simultaneously (unfortunately, that particular feature didn't exist when I bought my 4-year-old Anker 20000mAH pack).  Packs with this feature are ideal for powering devices like the RPi.

I don't know which particular battery pack product you have, but they may be designed to allow being charged at the same time that they are providing output power.  The ones that are specifically designed with this feature are commonly referred to as having "pass-thru" or "pass thru" or "pass through" charging capability.

These packs with pass-thru charging can certainly be used as a 5VDC UPS (I believe it was Steve asking this question earlier).  RAVpower also offers this capability combined with solar charging, which might also be useful, depending upon the particular application.

Here's just one example of the products available from RAVpower (the specification doesn't specifically list it, but you can reference the FAQ to confirm that it supports pass through charging on all of its output ports):

From: Jerome Kutche <n9lya@...>
Sent: Tuesday, July 10, 2018 5:38 PM
Subject: Re: [RaspberryPi-4-HamRadio] Building a Raspberry Pi DMR HotSpot


Jim, Got curious, to make sure I was not making an assumption or had a bad
memory on a test from earlier,  and Just looked the first 4 I bought way
back late last year do charge while powering a device the ones I got in the
last few months.. Do not .. Wonder what changed or if it's a fluke that they
do, or a fluke that they do not.. I will do some side by side testing on the
one from last year and the one more recent. and see what parts may be
different. Or defective?
With two cell phones here.. and two battery packs.. I have them both hooked
to wall chargers and the pack connected to the phone.. I even switched
phones.. and one will charge will powering one will not..

It's possible it's a safety feature they added after the fact. But being
from China I kind of doubt it.

I am keeping the 4 that do.. and have labeled them such.. Huh... What is
If I charge with a 5V 1 Amp Charger none of them charge while powering a
device.. Hum..
I am suspecting a change in design.. Maybe in fact a safety feature..

73 jerry n9lya

-----Original Message-----
From: <> On
Behalf Of Jim Higgins
Sent: Tuesday, July 10, 2018 4:53 PM
Subject: Re: [RaspberryPi-4-HamRadio] Building a Raspberry Pi DMR HotSpot

Received from Steve McGrane at 7/10/2018 04:04 PM UTC:

>Awesome, thanks.
>Can you leave it plugged in all the time in that pseudo UPS config I
>was thinking about?

I'd be VERY surprised if you could.

Typical charge controllers for LiIon batteries don't provide a safe charge
if there's a load on the battery while it's being charged. This means that
using this thing to run your RPi while it's charging probably isn't possible
because devices like this are designed to stop delivering current when being
charged. LiIon cells catch fire and even explode if charged incorrectly, and
they can't charge correctly by the typical charge controller while
delivering current. So this cutoff-while-charging behavior is a safety issue
that a device manufacturer would be foolish to ignore... which is why I said
I'd be VERY surprised if you could use it as a UPS as you outlined.

On the VERY UNLIKELY chance that this device doesn't contain the typical
charge controller and instead contains a charge controller designed to
charge CONSTANT VOLTAGE to a certain safe voltage (~4.1 volts) and no
higher, and then hold that voltage; i.e., float, then you could probably use
it as a UPS... again PROVIDED the charger is able to deliver all the current
necessary to BOTH operate the RPi AND recharge the battery following an
outage. And in an environment with frequent outages you'd want this
additional current to be sufficient to recharge the battery before the next

Going back to the advertised unit... if it could be adjusted to deliver
5.2 or 5.3 volts out while still providing all the current needed to power
your RPi, you could put a germanium diode (voltage drop 0.2 volts) between
the device and the RPi so the RPi sees ~ 5.0 to 5.1 volts from the device.
Then you could use a power supply with a slightly higher voltage than the
device is trying to deliver to the RPi - let's say 5.2 volts - connected to
the RPi terminals to power the RPi. The diode would prevent this higher
voltage from flowing into the UPS and because the RPi supply is higher
voltage than the UPS, no current would flow from the UPS as long as the RPi
is powered from its own supply. But when the AC supply dies, current from
the UPS would flow immediately from the battery, providing uninterruptable
power to the RPi. Voltage adjustment would be critical. During recharge, the
recharge power supply would be different than the one powering the RPi, so
it wouldn't matter whether the device could deliver current while
recharging. I can only guess whether the UPS could turn on fast enough if
power failed again during a recharge.

Know what you're doing or don't try any of this because 20000 or 30000 mAH
of LiIon cells could easily burn your house down or kill you if they
exploded in your face.

FRAUD ALERT- I suggest everyone click on that last link below to the
batteries and tell Amazon this seller is COMMITTING FRAUD by advertising
cells with 9800 mAH capacity when cells of that size can't deliver more than
about 3400 mAH max. Clicking " Report incorrect product information" in the
lower right of the main portion of the listing pops up a little form that
you can complete in 30 seconds or less. Please help to drive these crooks
off of Amazon.

73 de Jim, KB3PU

>On Tue, Jul 10, 2018 at 10:50 AM, Jerome Kutche <n9lya@...> wrote:
> > Sure here they are.. Look like they are $5.99 for the cases. + 2.33
> > for
> shipping. Been a while since I ordered any.
> >
> >
> 6RKVR/ref=sr_1_2?ie=UTF8&qid=1531237557&sr=8-2&keywords=18650+battery+
> 30000mah+case
> >
> > Links to batteries several examples.
> >
> ries/dp/B015COL0ZM/ref=sr_1_5?ie=UTF8&qid=1531237658&sr=8-5&keywords=1
> 8650+battery
> >
> >
> ht/dp/B071XC7XH9/ref=sr_1_11?ie=UTF8&qid=1531237685&sr=8-11&keywords=1
> 8650+battery
> >
> > These have proven to be good as well.
> >
> /B00IOCCDBK/ref=sr_1_12_a_it?ie=UTF8&qid=1531237685&sr=8-12&keywords=1
> 8650%2Bbattery&th=1
> >
> > Batteries to NEVER BUY they are rated at 9800 maH tests have shown
> > actual
> rating is around 1000maH or even less.
> >
> l/dp/B074HB7W2F/ref=sr_1_25_a_it?ie=UTF8&qid=1531237685&sr=8-25&keywor
> ds=18650+battery
> > Best to stay away from any Yellow Batteries..
> >
> > 73 Jerry
> >
> >
> >
> > -----Original Message-----
> > From: On Behalf Of Steve McGrane
> > Sent: Tuesday, July 10, 2018 11:43 AM
> > To:
> > Subject: Re: [RaspberryPi-4-HamRadio] Building a Raspberry Pi DMR
> > HotSpot
> >
> > Links would be great!
> >
> > I was just thinking about making a "UPS" for my RPi from these guys.
> > Can I leave these plugged in, then have the Pi plugged into the
> > battery
> and have them float?
> >
> > I have a Pi that runs out of power and I can't tell what's causing it.
> > Would be great to have a "surge" reserve for when this happens.
> >
> > Thanks,
> > - Steve
> >
> >
> >
> >On Tue, Jul 10, 2018 at 10:38 AM, Jerome Kutche <n9lya@...>
> >> I make these all day from Parts off AMAZON.. They hold 8 18650 3V
> Batteries. You must watch what kind of batteries you get some are
> rated for like 9800ma each and that is a lie.  Get quality batteries
> best are Panasonic  NCR18650B rated around 3400 maH I also like the
> Samsung Green ones They are like $14 for 2. The LG INR18650 HG2 are good
> >> I have used some good batteries for a lot less you get 10 for about
> >> $15
> they  are BLUE sure fire and are rated at 3000maH so 8 x 3kmaH is
> 40000maH capacity.. I just like the Panasonic Batteries best and they
> are a bit more pricy.. I do use them in my High Current Draw
> projects.. sometimes..  Where $$$ is no issue.
> >>
> >> They do good the cases are like $4 each.
> >>
> >> So I can make each pack for about $19 after I make 4 I have 8
> >> batteries
> left so the 5th pack costs me $4 to make.
> >>
> >> I just make them for family.. But all you have to do is buy parts
> >> off
> amazon and make your own.. If you need links to these let me know... 
> A lot cheaper they buying an assembled pack from anyone.. I also put
> small amounts of DeOxit on the battery terminals and the terminals in
> the pack before locking it together.
> >>
> >> If the pic does not show up I will add it to the groups files... 73
> >> Jerry N9LYA
> >>
> >> PS what ever you get do not get the ones with a built in current
> >> limiter
> on the bottom of them. Sometimes hard to tell.
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: On Behalf Of WA7SKG via
> >> Groups.Io
> >> Sent: Tuesday, July 10, 2018 10:46 AM
> >> To:
> >> Subject: Re: [RaspberryPi-4-HamRadio] Building a Raspberry Pi DMR
> >> HotSpot
> >>
> >> Mark J Culross wrote on 07/09/2018 08:11 PM:
> >>
> >>> Anker makes some very nice, high capacity (20000maH & higher),
> >>> 5VDC booster batteries that work very well for portable operations
> >>> of USB-powered devices like the RPi.
> >>>
> >>> Mark J Culross
> >>> KD5RXT
> >>>



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