Reddit mentions of Stinger SPS70 Power Supply/Charger

First of all, going to D.C. will not save any money. There will be loses every time you convert from A.C. to D.C. and every time you go up or down in a D.C. to D.C. conversion.

And the losses can become quite significant.

My goal for D.C. was reliability. I operate my own servers and I am working on a telephone service, therefore having power at all times is very important to me.

Having D.C. for other things is nice, but I wouldn't have installed any of the D.C. power were it not for needing power all of the time for work.

Having said that, it was a simple matter to setup D.C. for the CPAP machines, some of our lighting and I will keep expanding into D.C., putting more and more of our living space on it.

I don't currently have the fridge or anything else on D.C. though I am starting to look into moving that direction.

To use D.C. there are three primary subsystems, the charger, the batteries and the load.

The charger:
I have a Stinger SPS70 charger with a charge control module to keep the batteries going.

http://www.amazon.com/Stinger-SPS70-Power-Supply-Charger/dp/B001TH8O9W

The charge control module monitors the amount of drain on the battery and only provides that much charge to the battery. So as long as power comes to the charger, the battery floats in the circuit.

That means, after the battery is fully charged, if 20A is being drawn from the battery, the charge control module measures it and provides 20A to the battery.

For a short period of time I used a regular battery charger, with a 50A rating. The problem was it always pushed 50A to the battery, regardless of the drain. The excess energy was wasted in heat and the water in the battery would boil out. Not only would I have to refill the battery a lot, but I had to constantly monitor everything to make certain it didn't get too hot. It just got too crazy and even though battery chargers are inexpensive and easy to get, I needed something with more smarts.

I tried a couple of smart battery chargers, but they proved to not be reliable enough to use.

With A.C. available, generally speaking, for every 10A of battery you will want 1A of charger. That will get the batteries charged quickly, within a half of a day, and still let you operate the devices you have attached. Remember, that is a general rule of thumb.

That means with the 70A charger I have I am able to provide enough charge to the three batteries I currently have and simultaneously run the attached devices. When I add the next battery I will still go with my current setup, but I will need another charger before I add any additional batteries after the next one.

When looking for a charger, try to locate something that is reliable and has good efficiency. I am told by the manufacturer the Stinger is about 65% efficient. While price is a consideration, being reliable and efficient is more important.

When I moved from a regular battery charger to the Stinger, I have not had to add water to the batteries since.

The batteries:
Batteries are the key to making this all work. You will want what is called marine or deep discharge batteries and not a regular car battery. I will let you look up to see what the differences between the two are, so no need to go into it here.

You will need to put the batteries somewhere kids can't get to them, but you easily can. You will need to check their water level every month. That means moving each battery so you can get access to the top of the battery for both a visual inspection and to add water. If the batteries are difficult to get to, you won't do the maintenance.

The batteries contain acid. If any acid gets out of the battery, say from overfilling one, then it will spill onto the floor and damage anything it touches.

A battery will die from any of the following; no water, too little voltage, too high of a charging or discharging current, old age.

With the setup I have I have to monitor the voltage. That means when the power goes out I have to watch the voltage until it drops down to about 12V and then shut everything down.

I am typically at home so it is not an issue. If I am not at home, I am very rarely more than an hour away. I have six hours of standby power so if the power goes out I can easily make it home, monitor battery charge and do a shut down as needed.

It is possible to automate the shutdown circuit and I will probably do that next.

Batteries are heavy and large. I have a very sturdy shelf they sit on and have made a dolly that can lift them up a few inches and roll them off the shelf for inspection. I have my batteries so I can shut each one off individually so I don't have to shut the entire system down to do maintenance.

I will eventually have eight batteries. That is a big commitment to time, space and money. So I can't afford to let them go bad.

Each battery is rated at 12V and 200A for a total wattage of 2,400.

The batteries must be stored in a place that kids won't be playing. While batteries are generally safe, it is possible to get hurt. If a person touches any metal between the positive and the negative side of the battery, well that would be bad.

The metal will be melted. If you were to have a ring or a watch that shorted out a battery, the ring would be melted. And so would your finger. And it would be incredibly painful while it happened. If the metal is larger than can be melted, the battery will melt instead. And when a battery gets too hot is can potentially explode.

That means acid and fire in the area it is stored in. And big boom booms.

I have never had a battery fire. I have never shorted out the two poles of a battery. I take a lot of safety precautions when I am in the area of the batteries.

To put it into perspective, I have a 40A circuit from the street, running at 125V for a total of 5,000 watts.

With the three batteries I have 7,200 watts of power and when I have all eight batteries there will be 19,200 watts if power. Definitely something to be respected.

You will need to vent the batteries. When they are being charged, all the time, they produce hydrogen gas. The area they will be stored in will need to be vented to outside so hydrogen doesn't build up.

Finally you will need to keep the batteries at about 65 degrees Fahrneheit. They can be hotter or colder, so if you are comfortable in temperature so will the batteries. If they get cold or hot, their ability to store a charge will decrease.

The load:
I have all of my computers, the KVM, the LCD screens, the gateways, switches and router, all of the fans and lights in the computer area running on battery power.

I had to replace the A.C. power supplies in my servers with D.C. power supplies. For the RAID servers I had to go with 500W rated supplies, but most of the servers operate using 250W supplies.

For other devices I had to use voltage regulators. Battery voltage floats between 11.8V and 14.4V depending on the load and the available charge.

Generally speaking, devices that operate on D.C. have a small fixed voltage they can use. I use the mini-box.com DCDC-USB voltage regulators. They will take a wide input range of voltages and turn it into a fixed output voltage. The nice thing about the DCDC-USB devices is through jumpers I can select an output voltage. If I have a device that uses 9VDC, I can set a jumper for that voltage.

Other thoughts:
There is a wide selection of devices like fans, lights and small appliances, by buying devices that were designed for automotive, marine or camping.

If this seems very complex, get help.

I hope this all helps and best wishes.