DC Switch looks Great!

[sirhc]

SO I went a read the long boring spec sheet on my OPTIMA Blue Top battery.

It is an AGM battery so it is hard to freeze these batteries even if DEAD DEAD.

They consider them 100% Discharged at 10.5V for their rating but can be discharged to and recovered from a lower voltage without damage or shortening the life cycles however you need an intelligent multistage charger to recover from a very low level.

Also found several 6V Batteries designed for solar sites that look interesting such as this one http://www.wholesalesolar.com/products. ... river.html

[sirhc]

So I hate when I am not sure about something so I have been reading and reading and reading tonight on battery terminology and practices.

I was wrong in a previous statement of voltages in relation to discharge state.

However draining some batteries below 10.5V "may" damage them but many manufactures claim that a standard 80% DOD is expected as a normal cycle especially for AGM and GEL.

In fact a lot of manufacturers of AGM and GEL claim no damage will occur to their batteries that are completely drained by accident a few times in a normal expected life span such as being used in an RV and the light is left on resulting in a complete discharge of the battery.

In fact if a complete discharge "occasionally" either by accident or intentionally resulted in the guaranteed destruction of a battery then every time a kid leaves the light or radio on in their parents car COMPLETELY discharging/draining the car battery (which is not a DEEP CYCLE AGM or GEL) the only option would be to replace the battery. Where as I agree repeated intentional discharging like this will damage the battery I do not believe that the once in a blue moon 100% "discharging" of a WET, AGM, or GEL cell will always result in the destruction of a battery. Yes I understand it "can", and if I play golf in a lightening storm I "could" get killed but this action where as is foolish and an unnecessary risk the odds are I will complete my 18 holes and live to tell about it.

Many times as a teenager I left my parents car radio on totally draining the battery to not even the dome light would come on and a simple jump of the car then idling for an hour or two in the drive way revived the battery to a state that allowed the car to be shut off and be able to start again. I realize that the battery was not fully charged and more then likely this process of charging took several days of normal car operations to accomplish a 100% charge but the battery was not destroyed nor was the life span noticeably diminished and I did not get grounded because they never knew it even occurred and my father was very mechanically inclined as we grew up in WV.

So will an occasional DEEP discharging or even the FULL discharging of a WET/GEL/AGM battery decrease it's life span? Yes it "can" and probably does to a measurable degree but if it only happened once or twice such as an emergency you probably would not notice the difference in the expected life span.

Can it destroy a battery the first time it happens? Yes it "can" but it is not very likely, especially with a good quality DEEP CYCLE AGM/GEL battery.

Once again we are not saying you should discharge your battery bank below the recommend voltage (DOD) as a normal procedure but if you NEED to you can if you chose to.

And yes as a WISP there are many situations where I would DEFINITELY rather replace $1,000 of batteries if it meant I stayed up at a critical remote location, maybe this site feeds a small remote town and they rely of the internet for medical and other emergency services.

But I do not "THINK" that discharging my battery bank in an emergency will always or even likely result in permanent damage to the battery. Is it possible,YES it is "possible".

Also keep in mind that if you have a 2 battery bank (24V) and you allowed the switch to take it to 9V IN AN EMERGENCY before it shuts off this would be less damage to the batteries than if you left the radio or dome light on in your car all night and FULLY drained the battery which we all know we have done this before and simply jumped the car and all was good.

Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it will last about 5 times as long as one cycled to 50%. Obviously, there are some practical limitations on this - you don't usually want to have a 5 ton pile of batteries sitting there just to reduce the DOD. The most practical number to use is 50% DOD on a regular basis. This does NOT mean you cannot go to 80% or even more once in a while. It's just that when designing a system when you have some idea of the loads, you should figure on an average DOD of around 50% for the best storage vs cost factor. Also, there is an upper limit - a battery that is continually cycled 5% or less will usually not last as long as one cycled down 10%.

So in closing, where as I agree it is not good practice to drain a battery below 80% DOD it does not guarantee that it will destroy a battery if done in an emergency.

The sky truly is not falling.

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[WisTech]

I've got pics on my desktop at the office! =) Had to run so couldn't post them. Have the switch powering a 5X, an AC-Lite and a PBE-M5 right now in the office.

[WisTech]

Pics added!

[WisTech]

Just got the switch deployed this AM, and upgraded the backhaul to a 5X, and tossed an NSM5 up as a narrow sector for a handful of clients out just a few miles. Works like a dang champ, even on a 12VDC bank, sitting at 88% efficiency with 30W load.

[mhoppes]

In a pinch can I use some 9 volt batteries I purchased at the Dollar store on my way up the mountain?

8-D