[Elecraft] Powering KX3 from Bioenno charger with battery in between

[Julia Tuttle]

Hi Hal,

Thanks for the advice.

I believe the battery has a BMS that will cut off the output if the power
draw is too high -- is that sufficient?

If not, can I trust the fusing on a RIGrunner port, or should I get a
proper inline fuse holder that covers both conductors?

73,

Julie

On Tue, Oct 19, 2021, 18:40 Hal Massey <haljr.massey at gmail.com> wrote:

> Hi,
>
> Your solution should work just fine.
>
> The Bioenno batteries I could look up easily were LiPO technology. I would
> make one suggestion when using a technology like LiPO. Turn off the charger
> every now and then and deplete the battery down to say 25%. You can
> accomplish this with a simple mechanical timer on the AC line (or use
> something more sophisticated). LiPO manufacturers don’t show any data on
> “Float Charging” which is what you propose.
>
> The reason I say this is I cannot find an exact replica of your suggested
> usage model in any of the characterization data on any manufacturer of LiPO
> batteries. Without a reliable source like data from a manufacturer you are
> taking on some of the engineering. At worst I could see your battery life
> being slightly shortened by your approach.
>
> LiPO batteries get intense when shorted out. I would recommend a fuse,
> fusible link, or circuit breaker to keep an accident from turning into a
> thermal event. Accidents do happen with power sources.
>
> The setup you are contemplating depends on integrating the charge demand
> and charge resupply (recharging). So if you add a 100W final, an ATU, or
> something else just be sure to keep that in mind. Every time you go beyond
> a 4A current demand the battery will be supplying the difference until you
> stop making greater than a 4A demand. Then the battery will return to
> recharging. Of course if demand exceeds 4A for too long the voltage will
> sag.
>
>
> While this always sounds pompous when I read it I will supply my
> credentials so you know this is not just a casual social media reply. I
> hold a BSEE from the University of California at Santa Barbara, an MSEE
> from Santa Clara University and practiced design engineering for over 35
> years ending up the Vice President and General Manager (GM) of Hewlett
> Packard’s Business Critical Hardware Group (a $2 Billion US International
> business). Having said all that I am not a battery expert. I looked at your
> problem using engineering first principles. (Can it be done? Can it be done
> safely? What are the consequences of such a topology?)
>
> I once float charged a 12VDC AGM battery from an Astron 50 Amp supply on
> top of California’s Crystal Peak. Crystal Peak is 1 mile south and 1 mile
> east of the famous Loma Prieta. Loma is famous for the big earthquake in
> 1989 during the World Series Baseball Game). This setup worked quite
> successfully for many years. Local hams told me it couldn’t be done and the
> battery wouldn’t last. When power failed at Crystal Peak we remained on the
> air (440.1--- N6ITW Repeater). It was true that the battery would not last
> the full service life in the manual. But most hams cannott keep a repeater
> running for 10 years with the same gear anyway. I suspect your experience
> will be similar. This will not be the perfect charge/recharge profile for a
> LiPO battery but it will be good enough.
>
> Regards
> -Hal Massey (WB6NNR)
>
> > On Oct 19, 2021, at 14:16, Julia Tuttle <julia at juliatuttle.net> wrote:
> >
> > Hi,
> >
> > I've got a Bioenno battery (it's so good!) and the stock 14.64 V
> (no-load,
> > by my cheap meter) 4 A (claimed) charger. I'm currently planning to just
> > leave things plugged in (mains to the charger to the battery to the
> radio),
> > and I want to make sure that's safe (won't start a fire and won't damage
> > the charger, battery, or radio).
> >
> > Here's why I think it is:
> >
> > Will I overload the charger? No, the KX3 draws well under 4 A. If the
> > battery is charging simultaneously, the constant-current circuitry will
> > adjust the voltage down until the two loads together are drawing less
> than
> > 4 A, at the cost of lower charging speed, lower output power, and/or
> higher
> > PA heat dissipation.
> >
> > Will I overcharge the battery? 14.64 V works out to 3.66 V per cell,
> which
> > looks like it's about 93% state of charge, which is fine for the battery
> > long-term.
> >
> > Will I overvolt the radio? No, 14.64 V is under 15 V.
> >
> > Am I missing anything here? Is this a safe way to leave things long-term?
> >
> > Thanks,
> >
> > Julie
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