Batteries: Knowledge is power that lasts!

[Dan Jacobs]

I saw another post where someone was asking a question about batteries, and I thought about a presentation I had seen about emergency power for amatuer radio operators. There was just too much good info not to share it. Names have been removed to protect the inncoent . I have tried to expand on the info in the past, but the presentation was pretty good as is, so I left it alone. If you ignore the parts that will only be specific to radio, you will come out the other side more knowledgeable about batteries, their proper use and feeding, and how they can help you while camping or in an emergency. I have highlighted in yellow the most important points. If you read nothing else, make sure to read the highlighted info, there isn't much that I highlighted.

There are some slightly technical parts, and I will do everything I can to answer the questions that anyone might have. Post them up! You might find a way to do some of the things you haven't thought you could and take your machine with you!

Less than 300kb .pdf file:
https://dl.dropbox.com/u/1347382/Emerge ... 0Power.pdf

[HoseCrusher]

Great article.

[Dan Jacobs]

Glad to share it. Here is some more info from another topic thread:

I am not sure about power consumption without the humidifier. My manual only says 5 amps DC. I suspect that has to be with humidifier. Guess 4 nights 8 hours a night. Can I recharge a deep cell off my car battery?

OK, lets look at the details.

Amp-hour means a constant load of "X" amps over an hour. 5 amps over an hour equals 5 amp-hours (Ah)

8 hours of 5 amp use equals 40Ah. Most batteries are rated at "X"Ah use over 20 hours. You need a 40 Ah minimum battery to use the machine at 5 amps for one night. You can either double the Ah rating of the battery for two nights, or use more than one battery for each extra night, etc.

Lets say you want to buy an Interstate Battery. Looking at their web site, http://www.interstatebatteries.com/cs_e ... rine_f.asptheir SC34M has an Ah rating of 50, so that leaves a little extra cushion in reserve in case you sleep in a little. 50 Ah means that if you use something that draws 50 amps, the battery will run it for approximately 1 hour, and will have a voltage of about 10.5 volts at that time.If you have no means of recharging this battery, you will need 4 of them for 4 nights at 8 hours of a 5 amp draw.

If you want to keep the battery(ies) extra happy, you will try to prevent the voltage from going below a 50% state of charge, which can be found with the help of this graph: http://www.scubaengineer.com/documents/ ... graphs.pdf. Your battery(ies) will last much longer if you can prevent them from going under 50% SoC, but deep cycle batteries will do much better at lower than 50% SoC than other types of lead acid batteries upon recharging.

Yes, you absolutely can recharge a deep cycle battery of of your car, but not your car battery exclusively. Start the car, let it run for a minute or so, have the deep cycle battery close and on a surface where it will not fall (the ground is a good place), hook up jumper cables properly to the deep cycle battery, hook them up properly to the car, and let it charge while the car runs. When it reaches about 12.5-12.7 volts (best checked 20 minutes or so after you remove the cables to allow the "surface charge" effect to diminish), and Bob's your uncle. It's inefficient to use such a large engine just for this purpose, but if there is no other source of power to charge the battery, it will work fine. RV's do this very thing to recharge their deep cycle batteries as they go down the road, or with a generator set.

When you get home, put the battery(ies) on an automatic charger that has a "float" charge, and keep them charged and ready for next time.

Another alternative is laid out here, which isn't a bad idea, and the battery can be disconnected from the UPS for charging from your car, then easily reconnected:
viewtopic/t73063/UPSZILLA--UPSUninterru ... upply.html The added benefit is that the UPS will charge the battery as it sits at home, and you can have auto-magic power back up for your machine at home in case of a power outage and protection against power surges. Changing 12VDC power to 120VAC isn't as efficient as running a 12VDC capable machine straight off the battery, but it is a good option if you need it.

I hope that has been helpful in your decision making. Please let me know if I can help you any further.

[JohnBFisher]

Good information. Of course, for those of you interested in using a dep cycle battery as a backup battery can use the following Battery Backup Design to create your own battery backup system:

viewtopic.php?p=449334

The advantage of this over most UPS type designs is its ability to last even with humidification. In our area when we loose power we tend to loose it for a couple days at a time.