MPPT w/ No Battery

[olsenn]

I have a 70W folding solar charger which has an unregulated DC output. I would like to be able to connect this to a device which will force the output voltage to be a constant value (such as 12V) and whatever current that yeilds the maximum power-point of the solar panel.

A MPPT charge controller is similar to what I am looking for. However, all the charge controllers I know of require a battery be connected for it to work. It shuts off when the battery voltage is high enough to be considered fully charged and won't output power at all unless it reads a certain minimum voltage across the battery terminals. I want to bypass this limitation.

Does anyone know of any device I can use towards this end?

[PNPmacnab]

That basically is a linear current booster often used for remote pumping without a battery. A common buck converter will work if the panel is not heavily loaded. Too much load and panel voltage and power goes into a death spiral. I'm using a couple right now that are modified. When panel drops below a fixed voltage it fakes the converter into thinking the output voltage is too high. Lower voltage can work for a load like a fan. What is your load? Don't know of any commercial ones that you don't pay thru the nose for as it tends to be a specialty item.

[LETitROLL]

That basically is a linear current booster often used for remote pumping without a battery. A common buck converter will work if the panel is not heavily loaded. Too much load and panel voltage and power goes into a death spiral. I'm using a couple right now that are modified. When panel drops below a fixed voltage it fakes the converter into thinking the output voltage is too high. Lower voltage can work for a load like a fan. What is your load? Don't know of any commercial ones that you don't pay thru the nose for as it tends to be a specialty item.

Good info PNP, I am about to receive (and test) my first Buck converter, I mostly understand them well. My question is, at the end of day for instance (sun going down), seems to me there would be a point in every system where the threshold to run the load is barely available and the converter would "switch off" the load, then panel voltage could come up just a bit (no load) and converter would see enough to switch load back on?, I have always been curious if getting into a 5 or 10 minute zone as the sun goes down, where they toggle on and off many times is possible, common, or they require enough "headroom" from the input side that that is not usually a problem?
thanks
I am going to be running a 5w security camera, and 5w hotspot , at a remote location, with a good size panel.

[PNPmacnab]

True, a lot of electronics will almost shut down when the low drop out voltage is reached reducing the current which is drawn. While not "working", they will still draw some power. With many motors they just go slower. I have a hot water diverter that can send as little as 1/10A to the heating element. As the sun starts setting the electronics still works when the 520W array can only produce 5ma. A very small Li battery can stabilize the output if an electronic disconnect is added.