DC - DC Battery Charging Using a Charge Controller

I've found DC-DC battery chargers to be quite expensive (>$500 for a 24V-12V 5A charger) but I need one for an off-grid solar application. I had an idea to use a small 12 V solar charge controller (because they are cheap and readily available) between the 24 V source (in this case a 24 V battery bank) and a 12 V lead acid battery. Would that work? Or would its just burn out the charge controller?
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Brock and firerescue712, I'll definitely give it a try then.
Johann, that is the configuration I currently use, but I'm trying to find a way to stick to purely DC to minimize losses.
I am available for custom hardware/firmware development
If you try this with a PWM controller, the internal fuse or FET switch will blow nearly instantly, as the 24V 200aH battery tries to dump it's power into the 12V battery, when the PWM circuit turns on. Not at all efficient. If it survived, it would only be about 50% efficient, PWM relies on a solar panel acting as a current source, not a voltage source. The further the voltage of the PV is from the battery voltage, the more loss.
The MPPT controller will be about 95% efficient, as they nearly always (for a quality engineered one). Not all MPPT controllers are rated for Battery - battery charging like this, but Morningstar is capable.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
I am available for custom hardware/firmware development
This application is alot diiferent than hooking solar panels to the mppt. An mppt internal failure could start a fire.
http://members.sti.net/offgridsolar/
E-mail [email protected]
MRBF terminal fuse by blue sea (MRBF - Marine Rated Battery Fuse)
http://bluesea.com/productline/overview/378
Get the fuse & holder.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
-Bill