Need Simple 12 vdc voltage regulation

[PowerGuy]

We have two 500 watt tracking arrays running in parallel. The tracking sensors and linear actuators are also in parallel and are powered by an old 12 vdc car battery. The battery is kept charged by an 18 watt flexible solar panel that was supposedly designed to trickle charge a car battery. Unfortunately, the load on the battery is very small and even the 18 watt solar charger ends up overcharging the battery and eventually boiling away the electrolyte. What we need to perfect this system is a Zener diode across the panel output to limit the voltage to the wet cell bulk voltage of about 13.5 or, at most, 14 volts. Left alone, it goes over 16 volts and the electrolyte disappears.

We went on the net for Zener Diodes and found thousands of them, but were not able to find any that seemed to be sized for our needs, of about 13.5v back voltage, and about 25 watts rating (since the Isc of the panel is about 1.0 amp).

Has anyone solved this problem and thus has a source for a Zener of about 25watts or greater that can maintain a healthy car battery? We do not want to use an IC or a complex system, just a simple diode, like the system on the 1960's BSA and Triumph motor cycles!

[cinok]

I do not know nothing about solar but would an older style voltage regulator work for an older car. Many of those were even adjustable to prevent just what you are experincing.

[12vman]

I'd just get one of these..

http://www.harborfreight.com/7-amp-solar-charge-regulator-96728.html

It'll control the charge and avoid over discharging your battery. I use one and it works well. Just gotta mount it in a weatherproof box of some kind.

[tomato204]

Less accurate but if you shade the trickle charger it will have less output. Duct tape?

[PowerGuy]

BWF strikes again! Thanks to all for resposnes. An older car regulator would likely not function very well with the low amperages I have from this so called trickle charging panel. Likewise, I tried biasing the small panel by facing it east instead of south but that did not help either. The actual load represented by these two linear actuators is so low that there is virtually no load on the system.

But the small regulator suggested by 12vman is perfect. I can mount it in the battery box that is at the base of the tracking pedestal.

Thanks for the responses!

PG

[12vman]

PG..
Get one of these so ya don't have to butcher the controller. The wire colors are switched in the plugs but they line up perfectly to the controller. You'll see what I mean.. ;)

http://www.radioshack.com/product/index.jsp?productId=3870003

[PowerGuy]

12vman, I was already planning to do that! But did not know where to get this plug assembly, so thanks. I too try to avoid cutting up the cables of a device like that controller. I also found a local outlet that carries the controller so can save shipping costs. Thanks again!!:)