I have a project that will use multiple LiPoly batteries. I would like to charge the the batteries during the day with solar for my circuit to use them every night. My idea is instead of buying 3 Sunny Buddy chargers with 3 solar panels, I would like to get one solar panel and one sunny buddy then switch the output as each battery charged.
The original idea was to use the Arduino to check the output voltage of each battery. When battery 1 gets low, the Arduino would turn on a transistor that would add the battery 1 to the output of the sunny buddy. Only one battery would be charged at a time. When battery 1 was considered charged, the Arduino would “turn off” battery 1 transistor and check battery 2. If battery 2 is low, it would “turn on” battery 2 transistor connecting it to the output of the sunny buddy. The batteries are only going to be used at night to push LEDs so there will be no load on the batteries during the day.
Does anyone see any issues with this type of set-up? I didn’t see a charged indicator pin on the sunny buddy, so I will use the Arduino as well to see when the battery is charged.
Unless you are fairly skilled at electronic design, anything you put between the battery and the Sunny Buddy is likely to interfere with battery voltage measurements, and proper Sunny Buddy functioning.
Even if it is put behind the battery on the negative lead? Also, it would be a transistor, which I don’t believe transistors have much of a voltage drop? I have attached a diagram of basically what I am thinking about doing. This would just be replicated in parallel.
LiPo cells are easily destroyed by improper charging or discharging, and the control depends CRITICALLY on the voltage (to one tenth of a volt).
If you have to ask whether it makes a difference putting a device in the negative battery lead, you clearly do not know enough electronics to do this properly. Just use a single battery of sufficient capacity.
A safe way to switch the batteries would be to use electromechanical relays, but they waste so much power that there is no point in using them in a small scale solar installation.
First I appreciate the pointers but instead of just saying I am not knowledgable, maybe telling me why it will not work would be more beneficial? I can’t learn by you just saying “you don’t know enough.” If that is the case, why even do any of this in the first place?
What I’m saying is that your particular idea will not work unless it is designed by an expert and even then it would be failure prone. However, with some study you could certainly become that expert.
I’m not interested in designing the proposed circuit for you, or explaining how to go about the process, because there are much better solutions, such as using a LiPo battery of larger capacity.
Ok, fair enough. Where could I pick up a large LiPo, between 4,000 and 5,000 mAh? I was going to use 2 x 2000mAh batteries plus a 500mAh battery to power the Arduino.