Using the SunnyBuddy to charge lead-acid battery

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1

I know that the SunnyBuddy is a charger for LiPo batteries and it’s not intended (nor safe?) to charge other types of batteries with it.

However, I’m living in Europe and the temperature in winter can be as low as -20°C (-4°F) whereas temperature in summer can be as hot as 40°C (104°F) - neither is a temperature where a LiPo is feeling comfortable.

I’m curious if the board can somehow be modified to be able to charge a 6 V or 12 V lead-acid battery or any other battery that can withstand above temperatures. As you may have guessed allready, I’m not an electronics expert.

I’d like to build a weather station like in the tutorial

https://learn.sparkfun.com/tutorials/we … nderground

but either use another type of battery or even take a completely different approch I havent thought of before, as the LiPo probably wouldn’t survive a year.

Thanks for any suggestions!

2

Mr Earl:
I’m curious if the board can somehow be modified to be able to charge a 6 V or 12 V lead-acid battery or any other battery that can withstand above temperatures. As you may have guessed allready, I’m not an electronics expert.

Thanks for any suggestions!

No, charges are designed for a specific battery type. Some chargers can detect what kind of battery is connected, but they are on the expensive side.

If your electronics are going to be in box (which I hope they will be), then you research how to keep the inside temp within the LiPo’s thermal range…

3

It is quite easy to charge lead-acid batteries, and they tolerate abuse much better than most other types. One very simple approach is a constant voltage float charge of 13.8 V (for a “12 V” battery), but see this page for complete information: http://batteryuniversity.com/learn/arti … id_battery

4

Is it possible to combine this idea with the MPPT part of the Sunny buddy?

5

Yes. Many commercial systems already do so. First hit in Google search: http://www.ti.com/lit/an/slva378/slva378.pdf

6

Sorry for being unprecise.

My question was, if it is (easily) possible to use SunnyBuddy as part of the implementation.

As far as I understand, the board has two main functions:

  1. The MPPT part: adjusting the voltage coming from the PV panel to a constant value

  2. Battery charger: respect the battery’s constraints when charging(maximum voltage, float charge,…)

The ideal case: somehow modify the battery charger part in a way so that it is able to charge a 6 or 12 V battery. Is this possible?

If not, is it possible to only get the constant voltage from the MPPT part? I could then hook up a different charger suitable for lead-acid batteries.

Or is all that too difficult/dangerous/… so that i should rather forget the SunnyBuddy and look into making a charger from scratch or buy a readily made one?

7

Your first move would be to consult the data sheet for the chip on the SunnyBuddy board to see what its capabilities are. There, you will discover that lead acid batteries can be charged using the chip.

Then, you would look carefully at the SunnyBuddy schematic diagram and see what components would have to be changed, and decide if it is possible, worthwhile and whether you have the skills to change them appropriately.