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Battery Power

Posted by Mark Keitel   10/07/2004 12:00AM

Battery Power

After attending a few Star Parties I realized that having battery power for my equipment was the only way to go. If I was only visually observing this may not matter so much to me, but since I am imaging being self contained at night has gotten to be a big deal. With the influx of people at Star Parties and the number of individuals that now consume power at night has increased to a dramatic proportion. Not only have the number of go to mounts, and people imaging increased, but so has the number of people that bring other items that plug in. Here in Florida there is never a night at a Star Party that one will not hear the loud rumble of a hair blower getting the dew off of their optics. Then the electric blankets on a cold night, or even a plug in electric heater in a pop-up camper. All in all the drain on these sites has become enormous. This past WSP2004, there was never a night that the breakers were not tripping from the amount of electric being used, by the people and their equipment. In comes battery power. It can be on the inexpensive side up to the very expensive side. There are now generators that boast a 59db rating at 7.7 yards. Now that is quiet unless you are wanting to sleep and one is on next to you. Personally I come to a Star Party to be out in nature and be with friends and fresh air, NOT to smell gasoline from a nearby "quiet" generator. But that is another issue all together.

Battery power comes in many forms and shapes. And then you need a charger and then an inverter if you want to convert that power.


BATTERY CARE is your main responsibility with home made electricity. This is the one part of your power system likely to be harmed by neglect or misuse. Lead-acid batteries, the standard in home energy, should not discharge more than 50%. Ideally, they should be recharged to 100% promptly. They can be damaged by undercharging, continued overcharging, or contamination. Do not store batteries without periodic recharging. Continual self discharge when not in use can ruin even a brand new set of batteries.

DEEP CYCLE lead acid batteries have thicker plates and lead-antimony support grids for years of over 50% deep cycle charge and discharge. Golf cart batteries, the "L-16" and the "L-16HC" industrial batteries are the most common. Surplus industrial batteries may be deep cycle lead-antimony, or pure lead, or may be shallow cycle lead calcium construction.

Auto batteries are shallow cycle only. Cat, automobile, and truck batteries are NOT deep cycle and will not last long in home power systems. These have thinner plates and lead-calcium grids designed for less than 20% discharge and immediate recharge. If an industrial lead-calcium battery is well oversized so that normal cycling uses only the top 20% of battery capacity, lead calcium cells can be used.

RV/MARINE This common 12 volt battery is designed about half way between a deep cycle and a shallow cycle, and has medium length of life.

SEALED BATTERIES Gel or AGM (absorbed glass mat) types damage easily from overcharge, and so should be used with a 3 stage charge control. Sealed batteries can be excellent deep cycle alternative energy batteries, cleaner and safer, but only if charging is precisely controlled. Since water cannot be replaced and hydrometer testing is not possible, they are considered special purpose batteries.

NICKEL CADMIUM (ALKALINE) BATTERIES: Unlike lead, deep discharge and failure to recharge do not shorten battery life. However, surplus batteries are often overpriced and defective. Cost is much higher than lead acid. Voltage swings higher when charging and lower when using. Charge efficiency (energy charged in versus energy returned to you) is very low. Disposal and recycling can be difficult and costly. Be cautious of buying used alkaline batteries.


Battery Charging - Remember you must put back the energy you use immediately. If you don't the battery sulfates and that affects performance and longevity. The alternator is a battery charger. It works well if the battery is not deeply discharged. The alternator tends to overcharge batteries that are very low and the overcharge can damage batteries. In fact an engine starting battery on average has only about 10 deep cycles available when recharged by an alternator. Batteries like to be charged in a certain way, especially when they have been deeply discharged. This type of charging is called 3 step regulated charging. Please note that only special SMART CHARGERS using computer technology can perform 3 step charging techniques. You don't find these types of chargers in parts stores and Wal-Marts. The first step is bulk charging where up to 80% of the battery energy capacity is replaced by the charger at the maximum voltage and current amp rating of the charger. When the battery voltage reaches 14.4 volts this begins the absorption charge step. This is where the voltage is held at a constant 14.4 volts and the current (amps) declines until the battery is 98% charged. Next comes the Float Step. This is a regulated voltage of not more than 13.4 volts and usually less than 1 amp of current. This in time will bring the battery to 100% charged or close to it. The float charge will not boil or heat batteries but will maintain the batteries at 100% readiness and prevent cycling during long term inactivity. Some gel cell and AGM batteries may require special settings or chargers.

10 Battery Do's

Think Safety First.

Do read entire tutorial

Do regular inspection and maintenance especially in hot weather.

Do recharge batteries immediately after discharge.

Do buy the highest RC reserve capacity or AH amp hour battery that will fit your configuration.

11 Battery Don'ts

Don't forget safety first.

Don't add new electrolyte (acid).

Don't use unregulated high output battery chargers to charge batteries.

Don't place your equipment and toys into storage without some type of device to keep the battery charged.

Don't disconnect battery cables while the engine is running (your battery acts as a filter).

Don't put off recharging batteries.

Don't add tap water as it may contain minerals that will contaminate the electrolyte.

Don't discharge a battery any deeper than you possibly have to.

Don't let a battery get hot to the touch and boil violently when charging.

Don't mix size and types of batteries

Now there are units that come self contained battery / charger/ inverter all together in one nice package. I have used two such self contained units before.

1) Century Portable Electric Power model BPIP-99
This unit has a charger, inverter, (2) 17 amp batteries inside. A 300 watt inverter with two grounded plugs onboard. also one cigarette lighter adaptors. Very
nice unit and was great when I was not imaging. Worked all night long with my mount. As my power requirements increased this battery was no longer
enough. This battery is rated for 300 watts (2.3 amps) 12volt output 20amps

2) xPower 600 Indoor / Outdoor Generator made by Xantrex
This unit called a generator though it has NO engine. 40 amp-hr AGM sealed Non-Spillable, Lead Acid battery. 600 watt inverter 115vac 60Hz continuous
power. It has two grounded plugs on the inverter. Has one cigarette lighter adaptors. Also has a power switch for the A/C outlets and battery status light
bar. Nice thing about this is it is on wheels. I still have two of these little gems. Xantrex no longer makes these from what I can figure out. They make a larger version now a xPower 1500.

Now all this is great and wonderful. What about the equipment that is sensitive to energy spikes that an normal inverter can not control? The Xantrex does a very good job at this, though it is on the lines of what is called a modified Sine Wave Inverter. What is really needed is called a Sine Wave Inverter. These now tend to get expensive, though there are going to save the equipment that you spent thousands of dollars on. There are different manufactures of Sine Wave Inverters however I decided to get one made by Xantrex. I had such a great experience with their xPower 600 that I decided to also go with their Sine Wave Inverter. Another thing to consider on Inverters, that is if you are putting together your own system. Do you want to go with 12 or 24 volts. 24 volts will give you a longer run time, and you will need to have more batteries. I chose the 24volt system since this was also going to be used in my home since living in the Hurricane capital of the World this unit will be used. In fact as soon as I finished putting this together and I built the cart for it. Two days later we were hit with Hurricane Jeanne. Being without power for 105 hours this system got a nice work-out. I did not use the Sine Wave Inverter on my Refrigerator, instead I used a generator that was being used for other things too. Due to the use of "Dirty Power" the Refrigerator was a casualty of this storm.

With the below set-up once can run a 6amp draw for 43 hours or 5 nights at 8 hours per night. And still have some left over to view a movie on your laptop. This is without recharging. The following calculations were done by someone allot smarter than I on this

The specs on a group 31 battery. It is called a 225 amp
battery but it really delivers 130 amp/hours for 20 hours. That is a big difference.
130 x 20 = 2600 then you multiply that by 24 volts and you get 62400 watts. you take 50% of that an your get 31200. divide that by 120 volts and I get 260 amp hours.
You could run you 120 volt, 6 amp telescope for 43 hours.

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