Battery Charging

[JATO_RaT]

Any folks know what the best way to recharge a 12 volt battery used to open and close a gate. By best I mean for battery longevity or useful life. I have 120v at the gate but currently use solar cells. I'm just not sure that I'm getting the kind of life out of the battery that I should. The battery is a deep charging type, 12 volt, the size of a typical car battery. Thanks in advance, Rat...

 

[Gary_in_Indiana]

There are two things here. First, you should be using a deep cycle STARTING type battery. Other deep cycle batteries don't work nearly so well in your application. I learned this the hard way with an electric hydraulic tilt bed trailer.

The typical deep cycle is good for long draws at low amps. I had one of those and it was terrible. I then went to the starting type and it's been great. Like mine, your use is short burst, high amp draw so a starting type is what you need.

As to charging it, I use a standard battery charger on mine and it works fine. I hope this helps. /w3tcompact/icons/smile.gif

 

[JATO_RaT]

Thanks Gary, I do have a starting/deep cycle according to the battery label. What exactly that means I'm not sure. I was thinking about charging it with a permanently attached type charger, you know these fairly small ones that keep a battery maintained. While at a NAPA getting my battery, I noticed many different chargers. Some about the size of laptop computer transformer. The prices went all over the place. There were floating charge models and models that simply said 2 amp charge. I guess the real question is, is there a preferable type of charger and are there ones that can stay connected permanently? My two battery chargers will easily charge the battery but are too big to fit in the enclosure and also don't recommend staying tied to the battery over 24 hours. Rat...

 

[TWINKLE_TOES]

Rat,

The following is what you might get if you asked the battery manufacture this question (C is the battery capacity in Amp Hours):

Start by charging at a constant current rate of C/10, continue until the battery voltage rises to the transistion voltage (13.87 Volts for flooded Lead Acid with a temperature coefficient of ~ 4mV/deg.). At this point switch to a constant voltage mode at a higher voltage (Manufactuers vary here 14.8 to 16.5). Maintain this voltage until the current drops to C/40 ~ c/50. Drop the constant voltage to a "float voltage" (13.6 volts). This is occasionaly followed by a cell by cell equalization.

Chargers that do this are called smart, dual state or three sate chargers and cost an arm and a leg.

In your application, if everything is working properly you should never see a deep discharge of the battery (unless you live in Alaska or Seattle where the sun may not shine for several months).

Most trickle chargers are guaranteed to boil away the electrolyte if left on continiously. Harbor Frieght sells a trickle charger that is a regulated constant voltage type current limited to ~600mAmp. This is suitable for batteries of greater than 6 Amp Hours and up. The voltage is set at 13.6 volts which is below the transistion voltage of 13.87 Volts and will never charge the battery to 100% but will also not boil away the battery, except under hot conditions. The Item # is 37137 and costs about $15. Sealed Lead Acid are quite similar, differing slightly in transistion and float voltage recommendations.

You should not have any problem connecting this charger to your solar system The regulator will only source current and not sink any from the existing charger. Your existing system may provide a load for the trickle charger but this can be resolved with a series diode in the present charge line.

 

[JATO_RaT]

Al, it took me awhile to understand what in the world you were talking about. Not that your comment was hard to understand but rather my lack of knowledge about it, in fact, I'm really rather naive about the whole thing. I have gone to several websites like Schumacher and Battery Tender to get more education. Its pretty amazing how difficult it is to actually do this charging thing 100% correct. There are quite a few variables as you eluded to in your comment. Thanks for the information, it has made me all the wiser. I thought a simple little transformer/charger would be completely fine, however, its what the charger does and reacts to the changing conditions the battery goes through as it becomes charged. Thus, as you mention, a smart charger is needed. Even our little cordless tool batteries have been changing the way we charge them. Makita for example not only detects the battery temperature prior to charging but with an internal smart chip in the battery itself can tell the charger about its charging history and how it might charge it in its current state. Thanks again as you are a wealth of information on this board, Rat...

 

[JohnMiller3]

<font color=blue>...I have 120v at the gate but currently use solar cells...</font color=blue>

Why not use the 120 vac with a AC/DC converter (to operate your 12v equip.) and do away with the 12vdc battery & solar cell source entirely...? Seems somewhat redundant...

Normally, you'd have the 12v battery source at a remote location because 120 vac is not avail.

Just a thought... /w3tcompact/icons/eyes.gif /w3tcompact/icons/smile.gif

 

[JATO_RaT]

True John, I think the converter would have to be pretty clean since the contols are electronic. I never priced a converter but just figured a 25 to 30 amp converter would be a couple hundred dollars. Of course, thats only about 3 batteries or about 10 to 12 years of use. If the power goes down, your also stuck with a closed gate. Rat...