# How to efficient use Solar Panel to charge a 12V battery 10Ah?

I have tested my solar panel and i have these values :

Conneteced in series produces : Around 136V and 16mA(closed circuit)

Connected in parallel produces : Arround 15V and 450mA(closed circuit)

I want from this panel to be able to charge a 12V battery of 10Ah but also many other energy storage devices such as SuperCapacitors in the near future etc. etc. So my goal here is to be able to at least give at the charger controller from the panel around 13V-15V and 1Amp or at least the closest to 1Amp.

What could be my best bet to do so : Step down the series connection from 136V to 15V and raise the mAmps to where i need or use the parallel connection and give that straight to the battery charger and let the charger do the volts and amps regulations accordinng to battery/supercaps needs ?

I am on my first step of having the solar panel and try to find with these values my best way to charge 12V batteries and or SuperCaps (making portable for these 2 options)

Any suggestion or new way of doing it will be fine also and much appreciated.

Let's summarize. You have a panel that puts out 450 mA at 15 V. You want 15 V at 1 A.

This is clearly not going to happen. (15 V)(450 mA) = 6.8 W, which is the power your panel can put out. However, you want (15 V)(1 A) = 15 W. You can't create power from thin air. Physics can be inconvenient like that.

As a sanity check, let's look at the power from the series combination. (136 V)(16 mA) = 2.2 W. That means there is something wrong the series hookup, or maybe all cells weren't as fully illuminated as when you did the parallel test.

In either case, the best numbers we have still say that the panel puts out less than half the power you want. Get a bigger panel or lower your power requirements. No amount of conversion or parallel/series re-arrangement can fix this.

Switching power supplies can change the volts times amps tradeoff over a wide range with reasonable efficiency, but they can't make more power out than in. In fact, the power out will always be at least a little less than the power in due to some inevitable inefficiency.

• thanks for the reply, as it seems from the calculations yes i need to upgrade the panel with more cells but if i can`t do that, would a small inverter do any good before the charger for making the output reach the desired one ? – Vas Feb 27 '18 at 12:50
• @Vas: I might have a spare converter like that up at my unicorn ranch. Otherwise, go find someone with a pointy hat and a wand. – Olin Lathrop Feb 27 '18 at 12:54
• I understand. So the only way is either to low my systems needs at storage level or upgrade the solar cells to produce more power. – Vas Feb 27 '18 at 12:56

Total power not withstanding, if there is a risk of shading of part of the panel the series connection will be inefficient.

Depending on converter efficiency, you might benefit from combining multiple switching converters to a single load.

• thanks for the option, i might have some tests on it regarding shading and not shading cells.I am looking for converters for this way ? – Vas Feb 27 '18 at 13:03
• The maximum each cell produces non shade is 15V and 120mA as tested. But since my solar panel is not flat i have some shades cells so i think i will use only the part of the non shaded for charging reasons and the shaded ones for other smaller needs.If i use the non shaded cells only and connect them i have around 15V 400mA parallel and in series around 80V 40mA, it is kind of not so stable – Vas Feb 27 '18 at 13:09