Standby SLA 6v battery ( & charger)

Hi, I've built this charger (with LM312). I've also got one 6v-7Ah battery. The idea is to use the above as an arduino UPS. I will not use arduino's built in regulator. Instead I'll use a 5V LDO regulator and connect it's output to arduino's vin.

I would like to use an LTC4412 in order to feed from the power supply when power is present or from the battery when it's not. Browsing the application notes of LTC4412 http://cds.linear.com/docs/en/datasheet/4412fb.pdf I think that I need to implement the circuit of Figure 3 @ page 10.

My understanding is that MY "WALL ADAPTER INPUT" should be connected to the unregulated input of LM312 of the charger circuit.

Do I get it right?

As an alternative would it be feasible to just connect the input of the LDO to the battery's pole and not use the LTC4412?

Thanks in advance!

tzanampeths: I will not use arduino's built in regulator. Instead I'll use a 5V LDO regulator and connect it's output to arduino's vin.

Vin is the INPUT of the onboard regulator. The onboard regulator is already a low drop regulator (~1volt).

There are many ways to skin a cat. I would have used a 12volt SLA battery and charger, straight into the DC socket. That would have preserved the USB switching circuitry, that senses >=6.6volt Vin. When run time is important, and/or some high-drain 5volt sensors are used, I would replace the onboard regulator with a Pololu 5volt/500mA micro switchmode supply. Leo..

Sorry about that, I meant 5V pin, not vin.
I think that the built in regulator needs min 7V input. Once I tried a 6V PS and the board did not power up.

Did you put 6volt on the Vin pin, or on the DC socket. The DC socket has a polarity protection diode in series that drops another ~0.7volt. Onboard regulator can vary from board to board. Check the datasheet. Some are very low drop, others are not.

https://www.pololu.com/product/2843 100uA idle, 0.2v dropout, 85-90% efficient. jboyton on this forum has modded an UNO with it. http://forum.arduino.cc/index.php?topic=317000.0 Post#10 Leo..

You’re right. I used the DC socket.
So I’m ok with the existing regulator.

Well if anybody has something to say about LTC4412 "Speak now or forever hold your peace"

:D

tzanampeths: Well if anybody has something to say about LTC4412 "Speak now or forever hold your peace"

:D

Do you need it?

With such a simple charging system (assuming that works), why do you need that changeover switch? Wouldn't it be easier to just connect the charger and load to the battery - then when it's plugged in, the power is supplied almost entirely by the charger, while when it's not, the charger's not charging it, and so the power will coem from battery.

You typically need those sorts of switches when you have batteries that are pickier about how you charge them, like LiPo's - since the charger needs to know the current.

@DrAzzy,

Well I was wondering myself whether I really need it. I don't know what is being used in the vehicles nowadays, but I would guess that older cars just connect load to their batteries.

Thanks for your advice.

PS I try to be very cautious with Batteries & PSs. Really hate smoke & fire...

Oh, Since you mentioned it, do you observe any issues with the charger? Personally I don't have the required knowledge. I can measure voltage or current though.