Essentially what you're describing is a double conversion UPS, the most expensive and quality UPS available.?? You don't even need to use a battery cycle system, just use a charger that can keep up with demand of charge but won't overcharge the battery (DC-DC charger on one side with diodes on the other), the system will keep itself topped off until an outage then it will start discharging.?? For triggering it's normally a 120v to 3.3v relay powered by wall voltage that can trip pins on a pi which will then start either beeping during transmissions or doing voice announcements at interval.?? The ideal charging system would be single charger so there's no need to attempt to load balance the chargers when it gets to float voltage.

I can definitely rebuild this to do so but we would have to be sure that we have overtemp sensing on the batteries (I've seen some over 145*F) and that the city is OK with that kind of battery in the facility.?? As it's not likely to off-gas or burn it should be fine but if we wanted to use LiPo or LiFePo4 then there's a risk of that even if it's very small on the LiFePo4 batteries. ? I essentially have this exact same system with LiFePo4 batteries in my car so that when the car is shutoff it has 200AH of? reserve which is charged as soon as the car is plugged in or started and becomes feed through in that condition.

Miranda

On 3/5/2025 1:01 PM, Anthony KB3DVS wrote:

A suggestion I had made a bit ago was to use a lead acid or AGM battery in between the AC supply and the radios.

I worked with a ham in Alaska, who manages several repeaters and remote tower sites and this is how he does it, for simplicity and reliability.

The AC is on a timer, to be able to charge the battery within a few hours.

All the radio and compute runs off fused DC taps, (and voltage converters) so that if AC dies, the DC is still there and he's got 100+ AH batteries to carry it for days. He's got a bit of compute to make an announcement / send a message if AC is lost. There's diodes on the leads to the batteries to prevent any backflow form the battery to the AC power supply.

The DC can directly power multiple radios / compute at the same time as opposed to needing multiple AC adapters.

It's also cheaper than a similarly sized UPS solution that converts the DC battery back to AC that is then converted back to DC for the radios and compute.

Just an idea to consider if we're re-jiggering the power solution for a rack of radios and compute.

Anthony Burokas
General Class Ham (KB3DVS)
VP: Plano Amateur Radio Klub –
25-year video producer — IEBA.com

On 3/5/25 11:40 AM, Miranda Schwarck KE5YZP via groups.io wrote:

Tim,?

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If we have someone willing to donate parts then I'll take that over a paid replacement.? ?With both transmitters enabled transmitting the time we were at 30 amps, if all radios were transmitting we might get to 45 amps since APRS doesn't transmit, or not often anyway.? ?This means we should be able to take those two supplies plus the one still there and move the site back to permanent hardware changing up the power distribution just a bit.?

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We also should determine if the D-Star rack would benefit better from those supplies than the FM rack due to form factor or loading issues, as I didn't have a key I was unable to do any diagnostics on it.?

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Miranda