[ARC5] 24vdc power

[Charles]

For the small loads mentioned here, that approach is a good one, 
although I have read that battery life may be limited. Unfortunately for 
larger SLA or flooded batteries, and switchers too, the price increases 
more than proportionately ;)

It was actually cheaper for me to buy some of the components for the 
brute force PS than to buy batteries (and switchers).

On 9/4/22 23:06, scottjohnson1 at cox.net wrote:
> I wish I saved my old posts on this subject since it comes up every so
> often!  I find the best way to operate rotating machinery that once operated
> in a mobile environment is to replicate that environment.  SO-
> Get a power supply that can handle the full load current and float an SLA
> battery across it.  Size of the battery and power supply is proportional to
> load, but in your case, a 10-20 A switcher. Set to27.5 V (for normal indoor
> ambient temperature)
> Less for hotter, more for cooler, but in the range of 27-28V.  For your 10A
> load, 12V 7AH SLA batteries would do nicely. (Two in series).  Increase AH
> capacity proportionately for higher current loads.  Amazon and eBay have
> plenty of inexpensive switcher that will work, just don't buy the REALLY
> cheap ones, unless you like the acrid smell of burning components.
>
> -----Original Message-----
> From:arc5-bounces at mailman.qth.net  <arc5-bounces at mailman.qth.net>  On Behalf
> Of Charles via ARC5
> Sent: Sunday, September 4, 2022 10:23 AM
> To:arc5 at mailman.qth.net
> Subject: Re: [ARC5] 24vdc power
>
>> Hey guys,
>> What's everybody using to provide 24vdc for your military radios? Two
> 12vdc supplies in series?  Home brew?  Do they make a 24vdc switching supply
> that will handle 10 amps or so?
>> Thanks for your input,
>>
>> Richard kn7sfz
> Anything with a dynamotor needs about five times the motor nameplate current
> for the starting surge...
>
> I got a 2 KVA three-phase 115V 400 Hz rotary converter at a flea market but
> nothing I had was big enough to start it (rated at 27.5VDC at 115 amps!)
>
> So I bought a 20 VAC, 5 KVA toroid transformer on ebay, a BFBR (big bridge
> rectifier), heat sink, a 220,000 uF cap, meters and shunts, and brewed up a
> 24-28V 120 amp brute force supply with 240 VAC input. THAT starts the
> converter all right. It doesn't even blink at smaller dynamotors :)
>
> -Charles, WB3JOK/0
>
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