Need some guidance on run times

Timothybil

Flashlight Enthusiast
Joined
Nov 9, 2007
Messages
3,662
Location
The great state of Misery (Missouri)
I live in an area where power outages, while not common, occur frequently enough that I need to have alternatives available. I have my light an heat situation under control, but am still working on my computer & communications.
I have a nice APC UPS that works just fine to protect my desktop system, my DSL modem and my Wi-Fi router. If power goes out I can shut down my desktop and survive with my Android table without too many problems. The only drawback is that even when I shut down my desktop PC, the UPS will only run the modem and router for a couple of hours. Together the need 2A@12v.
I was looking at some battery packs today on line, and came up with some questions. As an example, one I was looking at seemed ideal. Capacity was 11000mAh@12v, which should be ideal. By my calculations that should provide me with about five hours of usage - 11Ah ÷ 2A = 5.5hr, right? To be conservative, maybe figure 4 hours useful life. The question is, is that 11Ah the usable capacity of the pack, or the total capacity, with some unknown portion not accessible, like the fact that one shouldn't drain a lead acid battery below 50%.

Anybody out there have any guidance to give, maybe some personal experience?
 

AVService

Flashlight Enthusiast
Joined
Dec 30, 2011
Messages
2,163
I live in an area where power outages, while not common, occur frequently enough that I need to have alternatives available. I have my light an heat situation under control, but am still working on my computer & communications.
I have a nice APC UPS that works just fine to protect my desktop system, my DSL modem and my Wi-Fi router. If power goes out I can shut down my desktop and survive with my Android table without too many problems. The only drawback is that even when I shut down my desktop PC, the UPS will only run the modem and router for a couple of hours. Together the need 2A@12v.
I was looking at some battery packs today on line, and came up with some questions. As an example, one I was looking at seemed ideal. Capacity was 11000mAh@12v, which should be ideal. By my calculations that should provide me with about five hours of usage - 11Ah ÷ 2A = 5.5hr, right? To be conservative, maybe figure 4 hours useful life. The question is, is that 11Ah the usable capacity of the pack, or the total capacity, with some unknown portion not accessible, like the fact that one shouldn't drain a lead acid battery below 50%.

Anybody out there have any guidance to give, maybe some personal experience?

I am going to leave the math out of my answer as in my experience it is not really all that relevant or realistic anyway,you just need as much capacity as you find practical from a standpoint of cost and size so that you can feel comfortable implementing it in your situation.

First of all many UPS units will allow for huge external batteries too even if not documented adequately too. SO as long as the system can charge the battery and many can as it just needs to trickle charge usually you can use car sized deep cycle batteries if you want to,and I want to for sure!

Secondly of you implement a simple charging system with a huge battery then the battery can effectively filter the power from even a crude power supply to turn nto a useful UPS for you that you have created.This way there is no real limit to the battery & Runtime again depending on your practical limits.

I use products from the Radio industry used to provide backup 12vdc power which is what you have already said os your requirement anyway for the network stuff. I find that wit a 75ah AGM or SLA battery on my network stuff that I can run my Cable modem and WiFi for a few days easily especially if I do not leave it powered up when not in use.

Look at the West Mountain PwrGate as an example of what I am talking about.

http://www.westmountainradio.com/product_info.php?products_id=pg40s&navcode=/UPSPGATE

You will need a 12vdc Power Supply,a PwrGate and the huge Battery of your liking.

I have 3 different systems like this set up around my house and here in TornadoVille have used them all too often too!

Those car jump start boxes as an example use a 9ah or 18ah battery usually and I have also used those a lot as they are handy and I can easily configure something on the fly if I need to but to get any meaningfully useful run times I need a lot of battery.
When you consider that typical UPS systems are really meant to only provide enough time for a safe clean shutdown it starts to make sense that those might not be practical to maintain your systems during even short outages.

So the method that I use is designed to make sure that I can communicate for a while during an outage and I can easily supplement charging with portable Solar panels when needed too.
 

Timothybil

Flashlight Enthusiast
Joined
Nov 9, 2007
Messages
3,662
Location
The great state of Misery (Missouri)
I have come to agree with you. The small UPS sets I was looking at claimed 250 watts output, but when I looked further, that was for something like five minutes, leading to a really low watt-hour figure.

I have configured a setup with a 40w Sunpower solar panel with 18v output, a reasonably priced PWM charge controller, and a 35Ah SLA deep cycle battery. I plan on buying as I get funds saved up. At my expected load of 25 watts, the 40 watt panel should be able to keep ahead on a good day. If I need more I can always add another panel and parallel into the charge controller.

What would be a good brand for a battery?
 

AVService

Flashlight Enthusiast
Joined
Dec 30, 2011
Messages
2,163
I have come to agree with you. The small UPS sets I was looking at claimed 250 watts output, but when I looked further, that was for something like five minutes, leading to a really low watt-hour figure.

I have configured a setup with a 40w Sunpower solar panel with 18v output, a reasonably priced PWM charge controller, and a 35Ah SLA deep cycle battery. I plan on buying as I get funds saved up. At my expected load of 25 watts, the 40 watt panel should be able to keep ahead on a good day. If I need more I can always add another panel and parallel into the charge controller.

What would be a good brand for a battery?
I am partial to Yuasa or Powersonic as these 2 have been the premier battery in the Alarm industry since I have been around it which is almost 40 years.

There might be no real difference at all though in the end these days too?

Don't know where you are exactly but if there is a Alarm Distributor anywhere near you these batteries will be a lot less pricey too.

I have a friend who is in Iowa a lot if I can help you get hold of a battery let me know via P.M. but I will bet they are around you too.
 

Timothybil

Flashlight Enthusiast
Joined
Nov 9, 2007
Messages
3,662
Location
The great state of Misery (Missouri)
I have configured a setup with a 40w Sunpower solar panel with 18v output, a reasonably priced PWM charge controller, and a 35Ah SLA deep cycle battery. I plan on buying as I get funds saved up. At my expected load of 25 watts, the 40 watt panel should be able to keep ahead on a good day. If I need more I can always add another panel and parallel into the charge controller.
Well, I went ahead and did it. Amazon had 100w Renogy monocrystalline panels for $100 USD on one of their one day sales. Couldn't turn down that much increase in input for about the same cost as the 40w portable panel I was planning to use. So I ordered one, the controller, a supposedly good 35Ah SLA (UB12350 12V 35 AH) deep cycle battery from Chrome Battery, and associated cables, fuses, etc. Should start showing up next week, so will if I ordered everything I need.
 
Top