Which 12V solar charger solution ?

[fhenryco]

Hello,

I'm currently using the TP4056 linear charger to charge a single cell lithium-ion3.7 V battery from a solar panel as explained here : http://www.instructables.com/id/DIY-SOLAR-LI-ION-LIPO-BATTERY-CHARGER/

However what i need is 12V rather than 3.7V for my project , and i still want the automatic solar panel recharge every day, so:

1. Either may be should i use a 3.7V to 12 V boost up module such as
   http://www.ebay.com/itm/25W-DC-DC-3-3V-3-7V-5V-to-12V-Step-Up-Boost-Module-LED-Moter-Router-Power-Supply-/281237769996
   but i have no idea what extra power consumption such boost up module implies for an output charge working at ~ 300 mA ... (on 12V) ... (i'm not so worried because the output charge (a solenoid valve) will be active only 5' per day)

2. another solution would be to have several 3.7 cells in series to reach beyond 12V and then a step down regulator to get 12V, but several TP4056 can only charge as many 3.7 V in parallell : using the cells in series at the same time ==> shorcuts ! i did not find a low cost module equivalent to TP4056 to charge several such cells while they are working in series ...

so i'm back to 1) unless someone can suggest something else ...

[gohan]

If the solenoid valve only draws 0,3A it should not be a huge problem using the regulator. Keep in mind that there are also latching valves that only draw current to change state.

[fhenryco]

@gohan Sure but those latching valves are probably much more expensive than my 5 euros solenoid valve

[gohan]

I didn't say that it would be cheaper

[Uhrheber]

For the charger:
http://www.ebay.com/itm/MPPT-Solar-Controller-3S-12-6V-Lithium-Battery-Charging-18650-Charger-Module-zhn-/332313023330

For the battery:
http://www.ebay.com/itm/1-3S-11-1V-25A-W-Balance-Li-ion-Lithium-18650-Battery-BMS-PCB-Protection-Board-/272761561101

You need a balancer to charge Li-Ion batteries in series, hence the addon board.
It also protects against overcharging, over-discharging and overcurrent.

You could also buy a battery pack with integrated balancer/protection:
http://www.ebay.com/itm/Portable-DC-12V-20000mAh-Li-ion-Super-Rechargeable-Battery-Pack-US-Plug-Lot-MU-/162662798231