charging 2 independent batteries - solar

[morphingstar]

Up to recently I had 2 solar panels float-charging 2 independent batteries - until the panels got stolen. The charge capacity was not good enough, so I want to find a better solution. Searching for panels that would deliver 250 - 500ma (2 - 3 times more than float charge) I found spec's / price relations that make me think of using one panel at 500, feeding both batteries.

Presumptions:
12 vdc 600 amp 40ah batteries are unequally charged.
Feed lines must be isolated using one diode per battery, consuming 0.5 - 1 vdc
Loadfree panel vdc might be about 20+.
Loaded voltage might be 14-15 vdc, excluding the isolating diode voltage.
Lowest battery voltage without voltage drop in wires might be12.
In this circuit the lower charged battery might get more current than the other, = good.
I do not intend to add a control device for cost reasons.
The negative pole of the batteries are connected together.

The "float charge" situation happens only when the sun rays are perpendicular to the fixed panel, a few hours per cloudless day. This is why 2 -3 times more current is required.

Do you see any "pot holes" on the way of creating this system? I can not yet, I have never done this particular "one panel / 2 batteries" circuitry.

Thanks for checking.

 

[(*steve*)]

The main issue is that the battery with the lowest voltage will hog all the current.

This will be an issue if one battery loses a cell, it will allow the other battery to go flat.

 

[morphingstar]

1 solar charging 2batteries

The main issue is that the battery with the lowest voltage will hog all the current. This will be an issue if one battery loses a cell, it will allow the other battery to go flat.

Correct, you got a point, thanks. If a battery loses a cell, its voltage will drop by that cell under load conditions, or the cell prevents current to flow. Most likely the bad battery will be detected by the owner / user, whether in good time I can not predict.

I presume this problem has been solved somewhere with some circuitry. Where could I find it?

Diagram attached.

 

[(*steve*)]

The normal solution is to use a proper charger and (most importantly) to keep your batteries in good condition.

If these are flooded cells, then they will tolerate overcharge much better than gel cells.