CajunWon
join:2005-12-30
Cary, NC
 ·ViaTalk
1 edit | reply to shortckt
Re: Home UPS powered by car battery: failed
Thanks again, appreciate your time on my little project.
1- The UPS (and the 14ga wires to my battery) should handle 2.5 amps for ~10 minutes without overheating. Both the UPS and wires remained cool to touch (not that that means a whole lot). I was drawing less than 0.7 amps for the laptop as the only connected device. The UPS began the 1 second interval alarm very soon after connecting the laptop. I disconnected the laptop and turned-off the UPS to reset and it would not come back on -even after connecting another charged/newer car starting battery. Perhaps it would have continued powering if I hadn't shut it down?
2 - Although the powerchute software does control the % discharge b4 beginning orderly shutdown, without the software the UPS is supposed to remain on until complete discharge as calculated by its' cpu. I don't think the software allows changing what the cpu thinks is a minimum charge.
3- Wonder if there's a way to hard reset the threshold of how low the battery voltage can be within the APC 350.
I'll install the Powerchute software to see what's available to change monitor.
btw: I did drain the battery significantly after several hours on my 400W car inverter and my cheap volt meter continued to read ~12 volts (could have been 11-14 volts as the scale is hard to read). It took nearly 3 hours to recharge. The inverter & wires remained cool. I would think the APC is of better quality than my Xantrec inverter. |
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drjim
Premium,MVM
join:2000-06-13
Long Beach, CA
clubs:
| Not to be picky about your voltmeter, but if you can't really read the difference between "11-14 Volts", it's time to get a better meter!
I have 4 APC units here, both SmartUPS and BackUPS, and they make a big deal about running the calibration routine every time you change the battery, even if you replace it with an identical one.
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One man's Magic is another man's Engineering. |
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shortckt
Watchen Das Blinken Lights
Premium
join:2000-12-05
Tenant Hell
| reply to CajunWon
said by CajunWon  :1- ...The UPS began the 1 second interval alarm very soon after connecting the laptop... I disconnected the laptop and turned-off the UPS to reset and it would not come back on -even after connecting another charged/newer car starting battery... You tried to restart the UPS with or without AC mains power applied? Some UPS models are designed to allow "cold restart" without AC and others not.
Anyway, I guess we can rule out overheating.
What happens if you just let it run after it begins the "2 minutes remaining" alarm?
2 - Although the powerchute software does control the % discharge b4 beginning orderly shutdown, without the software the UPS is supposed to remain on until complete discharge as calculated by its' cpu. I don't think the software allows changing what the cpu thinks is a minimum charge.
On some models, the remaining battery before the UPS shuts off. This setting is saved in eeprom and UPS obeys it stand-alone, without any outside software control. Useful if UPS is used to power non-computer items.
3- Wonder if there's a way to hard reset the threshold of how low the battery voltage can be within the APC 350.
Don't know for certain, different models have different capabilities, but my guess would be the dead battery threshold is hard coded into the firmware... however there are some trim pots on the logic board.
...I would think the APC is of better quality than my Xantrec inverter.
Sometimes that can be a bad thing. IMO the "smart" devices are sometimes too smart for their own good.
Along those lines, (just thinking out loud here) could the battery control circuit be thrown off by the internal resistance of the battery? Such a large battery must have different electrical characteristics than the original gel cell.
The folks who created APCUPSd have spent considerable time reverse engineering and documenting the APC brand UPS. Per their manual the CS/ES models are treated, for programming purposes, as "smart" devices just like higher end Smart-UPS.
»www.apcupsd.com/
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watchen das blinkenlights |
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CajunWon
join:2005-12-30
Cary, NC
·ViaTalk
| apcupsd software is interesting, but appearantly not applicable to my setup.
Following a little more research, and to aid others considering this DIY approach to extended UPS protection:
The APC350 cannot know the battery reserve capacity unless using the PowerChutePro software for recalibration. That process would require the APC to fully charge a drained battery -not good for the battery and likely not good for the APC charger. Also the Powerchute software, if running, would perform a shutdown within 3-5 minutes -therefore the software cannot be used with an oversized battery.
Since the APC doesn't know the battery capacity it will begin the 1 second sound warning within 3-5 minutes of power outage, but will continue to output proper current until depletion. If turned Off, the APC will not restart without Utility power present (therefore mine didn't actually fail).
The oversized battery must be externally charged every 6 months and recommended to 'shake' the battery every 6 months.
Use this calculator to estimate reserve time on your chosen battery. Simply input the battery amp our rating and your total equipment hourly usage in amps. »www.smartgauge.co.uk/calcs/peukert3.xls
Amps = Watts/Volts
e.g. 15" monitor 40 Watts; basic desktop PC 85Watts
125 total Watts divided by 120 US Utility Volts = 1 amp/hour
I believe I read the APC350 peaks at 2.5amps but will overheat if sustaining that current.
(again, I'm no EE -just regurgitating what little I've read. YMMV) |
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