Automatic switching controller - Help

Hi All

I'm wanting to build a complex battery charger.

There will be 5 individual batteries that will have to be charged from one alternator. This need to be done one at a time and they will be isolated. There are reasons for this.

My idea is to have a comparator circuit on each battery (all batteries isolated) confirming the charge state / voltage of each battery, Eg: 13.8 or higher = Fully charged. This can be done with a OPAMP.

It will start charging on "battery 1" and continue until the comparator is activated (13.8V), where it will then start charging "battery 2" and so one.

I was thinking of doing this with a decade counter 4017, getting the output of the 1st comparator to trigger the 4017 and moving it onto the next, But this has several problems:

1 - if it sequances through all the outputs and comes back to "bat 1" where the comparator is still high (battery full), it will never tigger again and cause it to move onto "bat 2"

2 - Even if problem 1 is solved, if all batteries are full, it would just switch through the batteries so quickly it would probably cause a problem or something, I would have to put a minimun charge timer on for each output/battery?

Another problem is the temp of the batteries when charging, I would like to place a LM35 on each battery, if the temp exceeds a threshold (OPAMP again), it must move on to the next battery.

I do under stand this could be done quite easerly with a PIC, however I don't know how to program.

Please help

Don't you have to put a time limit on changing state from one battery to the next as well as (V>13.8 OR Temp>Limit)?

I'm doing something like this with two batteries and a Solar Panel. I put a time limit on how long I leave the panel connected any given battery because if the battery has a shorted cell, the sequencer would never advance to the next battery...

MikeMl said:

Don't you have to put a time limit on changing state from one battery to the next as well as (V>13.8 OR Temp>Limit)?

I'm doing something like this with two batteries and a Solar Panel. I put a time limit on how long I leave the panel connected any given battery because if the battery has a shorted cell, the sequencer would never advance to the next battery...

Click to expand...

That does sound like a good idea, never thought about that!

Say a max time of 2.5 hours?

How are you controlling it Mike?

I used a CMOS oscillator/counter-divider chip for the timing. FET switches to muliplex the panel to the two batteries. A shunt regulator to limit the battery voltage during charge.

You could use a 555 clock and a 4017 as the multiplexor. Make the RC network in the 555 so that the max time it spends in any given state is preset, and that time is shortened if the given battery is too hot, or if its terminal voltage is already in the gassing range.

Hi Mike

Do you perhaps have a circuit diagram of the circuit you have used? I'm a bit confused on the timing and automatic changing.