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Posted 16 June 2014 - 11:56 PM
Posted 17 June 2014 - 03:31 AM
I wouldn't try this if I were you, unless you have the money to buy another MB for your PC. And using a car battery will probably provide you with a dramatic, and unwanted, result.
The above scenario will probably cause a disaster that will cost you money... money better spent on a beefier UPS.
Posted 17 June 2014 - 05:06 AM
Posted 17 June 2014 - 06:43 PM
Watts = Amps x Volts, and Amps = Volts / Resistance
So, if the volts are the same and the resistance hasn't changed, then the watts ( = power drawn ) won't change. So, having got Ohm's Law out of the way, let's look at the real life possibilities.
Increasing the battery capacity attached to your system will enable your UPS to supply the rated current for longer, but will take more power out of the unit to recharge the batteries after use and this may exceed the charging unit's rating leading to its failure. Should this charging unit fail with a short circuit, then increasing the battery capacity merely increases the amount of energy that will get dissipated through the short circuit.
Car type lead-acid batteries can provide very, very high currents, more than capable of starting a fire or literally melting your equipment !
It's your equipment, it's your decision. But I would look very carefully at the rating of the charging circuit before I went adding extra batteries to it.
Posted 17 June 2014 - 06:46 PM
This is a a fire hazard. The wattage required to charge those depleted batteries will exceed the current handling of the small unit you have.
Posted 17 June 2014 - 08:24 PM
Posted 19 June 2014 - 04:49 PM
If you look at your inverter you should find a plate on it giving the input voltage and current and the output voltage and current. From your post #6, you will find, I think, that the input voltage is 12V. This is a nominal value, it means that you can use any nominally 12V battery to power it. A standard 6 cell lead-acid car battery has a nominal value of 12V, but the actual voltage can vary from about 13.5V fully charged to about 10V virtually flat. Other battery technologies have similar but slightly different values.
Most inverters I have come across strictly limit their output power to the specified amount, which again you should find on the same plate. Let's say for example it has a maximum output power of 5A at 24V, equal to 120W. Whether you use one outlet or all six, that's it. The millisecond you try to draw more than the total 120W, it will cut out and you will need to reduce the load on it and re-set it. Designing load limiting like this is extremely easy, I was doing it with transistorised equipment 30 years ago !
Adding extra batteries will not increase your output capacity, it will only allow you to draw the power for longer before the batteries go flat. And the points that mjd420nova and I made above about the limitations of your battery charging circuitry and the fire risk are both valid.
Like mjd, I wouldn't do it - if you need more power, get a higher capacity inverter.
Posted 19 June 2014 - 08:44 PM
I think a little more thought is required, my reasoning is I ran a Yaesu FT7 off car batteries for several years. I used a cheap off the shelf 10 AMP charger, it ran through a battery tender. Only issue was battery life due to light up/down charge, gave me about 12-14 months. I did a fair amount of electronic installations on various sized boats, whether the batteries were group 27's or 8D's they all run the same basic stuff and do fine
Honesty & Integrity Above All!
Posted 24 October 2015 - 07:25 AM
I have seen this done before on a couple of occasions, if I remember rightly the issue was not the power but the type, car batteries are made for starting so the plates are thinner and almost porous making them very poor at deep cycling which a UPS needs to do, leisure batteries are about half way between, not designed for starting or deep cycles but they do a reasonable job of both.
What you should be really using is deep cycled sealed lead acid batteries as this is what the UPS is designed for a number of reasons, they charge at a slightly different voltage to car batteries, are capable a very deep cycles and will be safer, \I would think they would last considerably longer that the car batteries, no doubt they maybe slightly more expensive than the car ones but in the long run because they will not need changing as much the cost must surly be cheaper.
You can always daisy them to what ever you need, these are the ones I mean http://www.batterytrader.com/ups-battery-c-302.html
Posted 24 October 2015 - 12:12 PM
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