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A&A Engineering Charger + KBT2

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Brian - N5BCN

A&A Engineering Charger + KBT2

Hi all,

A&A Engineering's "QRP Smart Charger" has the option to be built using two of four charging rates: 0.250 A, 0.500 A, 0.750 A, and 1.00 A. I plan to run my K2 using a KBT2 + Charger combo.

Which two charging rates would best suit this setup? My K2 has a number of options and draws about 380 mA right now on receive, considerably more when the remoted KPA100 goes into high power mode (remoted KPA100 obviously runs on a different power source).

I've read W3FPR's Smart Charger Mod and he's using 250 mA, so I'm leaning towards the 250 mA/500 mA combo, however, I don't think his mod is used in conjunction with a remoted KPA100.

73

N5BCN - Brian

Don Wilhelm-4

Re: A&A Engineering Charger + KBT2

Brian,

The consideration over the bulk charge rate is still valid - if the
charger goes into bulk charge state the voltage is higher - AND, if the
receive current is much lower than the bulk charge current, the battery
can be over-charged. To prevent that condition, the bulk charge rate
should be lower than the receive current (it does not have to be matched
to the receive current - just lower).

What will happen is that part of the receive current will come from the
charger and some from the battery - all is well as long as your
operating times are only for a few hours, the battery will provide
plenty of "juice". The switchable Smartcharger is a real help here, but
I would suggest using 1 amp for the higher current rate - provided you
resolve to leave it at the low current rate until your operating session
exceeds 2 or 3 hours, and at that time, switch the charger to the 1 amp
rate. If you cannot make that resolution, then I would suggest your
proposed 250/500 ma combination would be better.

73,
Don W3FPR

On 5/8/2011 8:02 PM, Brian - N5BCN wrote:

> Hi all,
>
> A&A Engineering's "QRP Smart Charger" has the option to be built using two
> of the four charging rates: 0.250 A, 0.500 A, 0.750 A, and 1.00 A. I plan
> to run my K2 using a KBT2 + Charger combo.
>
> Which two charging rates would be suit this setup? My K2 has a number of
> options and draws about 380 mA right now on receive, considerably more when
> the remoted KPA100 goes into high power mode (remoted KPA100 obviously runs
> on a different power source).
>
> I've read W3FPR's Smart Charger Mod and he's using 250 mA, so I'm leaning
> towards the 250 mA/500 mA combo, however, I don't think his mod is used in
> conjunction with a remoted KPA100.
>
> 73
>
> N5BCN - Brian
>
> -----
> K2 #6800 KPA100/KAT100-2, KSB2, KAT2, KIO2, K160RX, KNB2, KAF2, LP-PAN/K2 w/ Pre-amp, SignaLink USB
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/A-A-Engineering-Charger-KBT2-tp6342835p6342835.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
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n7ws

Re: A&A Engineering Charger + KBT2

Don,

I'm sorry but I fail to understand why you think that the bulk charge mode will overcharge the battery.

Properly configured, the "smart charger" won't even completely charge the battery in the bulk mode, it takes a shift to the higher voltage absorption (overcharge) mode to completely "top off" the battery, after which the charger should reduce its output to the float voltage.

The whole idea behind the smart charger is the automation of the charge cycle without intervention.

The bulk mode current should be set by design to some fraction of the capacity (AH rating) of the battery and left alone.

I have a homebrew charger keeping a 95AH Deka AGM battery charged and have operated my K3/100 on it 100% of the time for over two years. I built it using an A&A board in a modified Astron 35A power supply.

http://k6mhe.com/n7ws/Astron_A_A.jpg

Wes

--- On Mon, 5/9/11, Don Wilhelm <[hidden email]> wrote:

> From: Don Wilhelm <[hidden email]>
> Subject: Re: [Elecraft] A&A Engineering Charger + KBT2
> To: "Brian - N5BCN" <[hidden email]>
> Cc: [hidden email]
> Date: Monday, May 9, 2011, 12:16 PM
> Brian,
>
> The consideration over the bulk charge rate is still valid
> - if the
> charger goes into bulk charge state the voltage is higher -
> AND, if the
> receive current is much lower than the bulk charge current,
> the battery
> can be over-charged. To prevent that condition, the
> bulk charge rate
> should be lower than the receive current (it does not have
> to be matched
> to the receive current - just lower).
>
> What will happen is that part of the receive current will
> come from the
> charger and some from the battery - all is well as long as
> your
> operating times are only for a few hours, the battery will
> provide
> plenty of "juice". The switchable Smartcharger is a
> real help here, but
> I would suggest using 1 amp for the higher current rate -
> provided you
> resolve to leave it at the low current rate until your
> operating session
> exceeds 2 or 3 hours, and at that time, switch the charger
> to the 1 amp
> rate. If you cannot make that resolution, then I
> would suggest your
> proposed 250/500 ma combination would be better.
>
> 73,
> Don W3FPR
>
> On 5/8/2011 8:02 PM, Brian - N5BCN wrote:
> > Hi all,
> >
> > A&A Engineering's "QRP Smart Charger" has the
> option to be built using two
> > of the four charging rates: 0.250 A, 0.500 A, 0.750 A,
> and 1.00 A. I plan
> > to run my K2 using a KBT2 + Charger combo.
> >
> > Which two charging rates would be suit this
> setup? My K2 has a number of
> > options and draws about 380 mA right now on receive,
> considerably more when
> > the remoted KPA100 goes into high power mode (remoted
> KPA100 obviously runs
> > on a different power source).
> >
> > I've read W3FPR's Smart Charger Mod and he's using 250
> mA, so I'm leaning
> > towards the 250 mA/500 mA combo, however, I don't
> think his mod is used in
> > conjunction with a remoted KPA100.
> >
> > 73
> >
> > N5BCN - Brian
> >
> > -----
> > K2 #6800 KPA100/KAT100-2, KSB2, KAT2, KIO2, K160RX,
> KNB2, KAF2, LP-PAN/K2 w/ Pre-amp, SignaLink USB
> > --
> > View this message in context: http://elecraft.365791.n2.nabble.com/A-A-Engineering-Charger-KBT2-tp6342835p6342835.html
> > Sent from the Elecraft mailing list archive at
> Nabble.com.
> >
> ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Brian - N5BCN

Re: A&A Engineering Charger + KBT2

Hi Wes,

I could be wrong on this, but I think what you say is correct if considering charging the battery alone, but is thrown off when you consider powering the K2 with the batt via the smart charger.

For example, my K2 receive current is about 400 mA with a bunch of options. Let's assume that my KBT2 battery is fully charged. Let's further assume I built my charger to use a 500 mA bulk charge.

When I turn on my K2, the charger thinks the battery needs to be charged, and therefore offers up its 500 mA bulk charge. 400 mA goes to the K2, the excessive 100 mA goes to the battery that is already fully charged, thus the possible overcharge situation (again, correct me if I'm wrong on this).

What Don is suggesting is to build the charger with a bulk charge BELOW what the K2's receive current is. In this case, a bulk charge of 250 mA. Therefore, when I turn on the K2, the charger offers up 250 Ma, the battery offers the difference, 150 mA.

If it's run this way for hours and hours, eventually the battery will be drawn down, in which case the A&A Engineering Charger has the option of switching to a higher bulk charge (1 amp for example), which can power the K2 AND charge the battery.

If I could somehow mod the smart charger to provide EXACTLY the same draw current as the K2, then I think you are right, the chance of overcharging the battery is nil.

73 N5BCN - Brian