Roger Bly

A solo over-nighter at the Santiago shelter. Refreshing cold, light snow, ice and those wonderful treacherous roads.

Trip Priorities: 

1. Re-establish internet connectivity to the repeater controller.
2. Replace the Dell computer server.
3. Change 440 input frequency back to 437.450 PL 103.5.
4. Tune 440 band-pass cavity.
5. Battery backup installation.

Trip report:

• (Done) Dell server replacement racked and tested.
• (Done) RLC controller connected to Dell server (talking to server).
• (Fail) Ability to send commands to RLC controller. Have RLC prompt – no privileged Auth. Plan: Ordered another RLC for testing on bench and future backup.
• (Done) changed 440 CDM freq back to 437.450 per decision by team to avoid interference.
• (Done) 440 bandpass cavity tune +6dB RX with change from 431.450 noise floor and cavity tuning.
• (Done) Battery backup re-install and 1kW inverter testing.
• (a little bit Done) General rack management.
• (Done) Shelter maintenance — Sealed open shelter cable ports left open by others with fire resistant foam, cleaned shelter floor.
• (No time) in-shelter webcam replace (Low priority)

Fresh new batteries in 24v configuration with 2x 12v battery tenders.
Long report on backup power calculations below. We do have propane generation for a week or so, but it has transfer switch delay and hasn’t been reliable. Need enough battery hours to alert the shelter crew to send a propane truck for refill; usually takes 1-2 days.

Nominal state — On power grid, Inverter is available, but bypassed because grid power is available.

Battery Backup Project — For loss of grid power and propane generator we have:  24 volts from batteries to inverter, producing 1kW+ @ 60 Hz AC pure wave.  But, a bit overloaded at 119 VAC (Vo) @ 8.7 Amps (Io) = 1,053 Watts AC to rack.

I know, blah, blah, blah… what’s the fucking runtime on battery power???
About 3 hrs now, plan to go to 15 hrs battery.
We also have 1+ week of propane backup, but there have been reliability issues.

( optional reading below )

Notice how the inverter instantly pulled the battery voltage down from 26.5V to 24.1V when commercial power was lost.

The Inverter will alarm at 19~23V, shut-down at 18~22V, restart at 23~27V.

So, here’s my math:
Measured the full rack with amplifier on during transmit as:
* ~800W @120VAC.
* 2x 12VDC @ 66Ah batteries in series = 24VDC @ 66Ah = 1584 Wh
* About 80% usable power before recharge of AGM batteries:
* 1584 Wh × 0.8 = 1267 Wh usable energy
* The spec on the COTEK inverter is 90% efficiency, we’re down to calculation of
800W ÷ 0.90 ≈ 889W. The inverter reports 1,053 watts usage
(+164 watts off, probably due to the incorrect efficiency estimations.)

Runtime (hours) = Usable Energy ÷ Power Draw
100% duty cycle ≈ 1267 Wh ÷ 889W ≈ 1.42 hours
50% duty cycle ≈ 1267 Wh ÷ 445W ≈ 2.85 hours
On, but not transmitting ≈ 1267 Wh ÷ 250W ≈ 5 hours
50% duty cycle — Amplifier Bypass, ≈ 1,267 Wh ÷ 250W ≈ 5 hours

We don’t like that! … so the plan is to:
1. Add 4 more batteries.
2. Re-apply our coax relay amplifier bypass circuit to drop to exciter power (see circuit below.

That will provide:
50% duty cycle and Amplifier Bypass ≈ 3,800 Wh ÷ 250W ≈ 15 hours
Realistically, I think we could reach 24 hours with a typical use profile. Need more.

Categories: Uncategorized

Tags: 147.435, 435, hilltop, repeater