Solar LED Spot Light with Extended Capacity and Dual Input

[icecube57]

I have an 3 spot light led light kit. Actually two of them. It has 3 lights and one solar charging base battery holder. This is supposed to last 6 hours on a charge. It has a 900mah 14500 Lifepo4 battery. Ive done a small mod to increase the light duration. When I first got the lights they were able to do 12hour charge. Im pretty sure the Led drive has an automatic brightness mode that drops the current as the battery discharges. Ive wired in an additional 14500 battery. I got a radio shack battery C battery holder and wrapped the cell in ductape until it match the sice of a C battery. Weve had several overcast days that drastically reduced the light duration to 3-4 hours. This prompted me to upgrade the batteries and double the capacity for overcast days where it didnt recieve a full charge. Well we have has several days of over cast and Im back in the same boat of it not getting a full charge. Since these are LED and the consumption isnt that high i decided to use a small AC to DC aka cell phone charger. I paralleled the first cell phone charger. It gave out 5.21 unloaded. When parallel with the solar panel to the input of the LED driver the charger became unstable as if the load was too big and it was cycling every few seconds. Ok on to the next charger. This charger has a 5.25v unloaded. Under load of the LED Driver/Solar battery charger the voltage dropped to 4.25-4.3. It functions normally the output voltage of the Driver/charger is 5.25 unloaded but 3.5 loaded. So it makes me wonder are both of the power supplies meaning the cell phone charger and driver/charger stable to a fixed voltage when loaded or will they float up to the unloaded voltage. I plan to put the cell phone charger on a timer/ and or photo light cell to come on in the morning run for a designated period of time and shut off based on the current output of the cell phone charger and total or partial capacity of all the batteries in the light system and consumption during the night. Its roughly 4 batteries with a total of around 4AH. the current I measured while charging was about 3-400ma. I do expect the solar to chip in at the end of the dc to dc bulk charge so when the sun is in the back of the house the AC to DC is working. The sun comes to the front of the house around 12-1 and sets fully around 530pm.

Anybody have any thoughts.

 

[icecube57]

From the looks of it the voltage is still climbing on the batteries. Im at 3.62v right now which is near full charge for Lifepo4. It makes me wonder is there a HVC on the driver/charger. I kinda doubt it. One thing i also noticed is it either has a good voltage regulator or some buck boost technology. The input voltage is lower than the output. Also since the input floats at 5.25 The max ive seen the solar panel out put is aroun d 3.6. I could use two diodes to drop the voltage around 3.8v Maybe this will change the output.

 

[amberwolf]

Just to be sure, are you hooking up the AC/DC PSU in parallel with the solar panel, or with the output of the panel's converter?

AFAIK for the former you'd need to have a diode in series with the panel to parallel it to another voltage source, or else the other voltage source will feed current back into the panel.

If the latter, then the converter will take care of that problem.


Regarding HVC, I'm wondering if they designed it expecting it to discharge fully each night, and calculated charging current so that even on the longest most optimistically sunny day it would never overcharge the battery? Then they would only need to have an LVC.


I don't know if it'd make any difference to lower the input voltage, but I expect it would only lower the charging current to the battery.

 

[icecube57]

The voltage with the cell phone charger charging the batteries was causing the batteries to float up to open circuit voltage. I stopped the charge at a safe voltage. Im going to have to get a volt phreaks charger or similar that limits to 3.7 to make this work successfully. Also Amberwolf I think the circuit was designed never to get a fully charge cause the panel doesnt put out enough voltage even fully exposed to light to fully charge the batts. But I still think there is some buck boosting but the thing is its not limited or capped at a fixed voltage but i think it does have a linear boost. More voltage in more voltage out. But this doesnt matter cause my approach now isnt to go to the driver/charger input but to parallel with the battery charging output directly. It does have an lvc of around 2.8 I assume because thats what both sets were at before I put them on the charger. Today I basically used the cell phone chargers to give both regular internal battery and extended battery a full charge and sat them outside to float charge on the built in solar panel. The sun starts hitting one panel aroun 10 and the next one shortly later. So now they both have a full charge and they have been in the sun all day so it theoretically should have a two night run capacity with its full charge now'

Eventually im going to solder some small wires to the internal battery contact points and have an external anderson plug and when i purchase and recieve my charger I will extend the leads to both light and do periodic charges to maintain them. I may permenantly wire them. I havent decided but it defeats the purpose of having solar lighting so.

How else do i get around the lack of a full charge during the day. Besides what im doing now

 

[amberwolf]

I can't think of a better way to do it than you are already doing, other than adding more panel surface area to make up for the loss of sun, and more battery to store what comes in when it is sunnier.