What 'flavor' smoke to expect - Solar to lead-acid.

My backup power system was 24V with lead-acid golf cart batteries and PV panels. One sunny day I charged a 12V assembly and didn't stop. At 15V the batteries produced bubbles (gassing) and got noticeably warm. I believe hydrogen is the normal gas produced, tasteless and odorless. Then it might be recaptured by special vent caps on the cells. And/or a bit of airborne sulfurous/sulfuric acid gas can escape from the cells. Whenever I put my face close to look into them, my nose detected a bit of pungency.

Unloaded your panels produce a certain voltage. That drops to battery voltage automatically when hooked up.

After that it becomes a question whether your 500W load leaves sufficient current to charge the battery, and, whether volts remains sufficient to overcome battery voltage in order to charge it.

To answer your initial question about charging the battery indefinitely...
The electrolyte eventually boils away (in one cell or all cells). I don't know to what degree you can restore battery usefulness. I don't know which is better to add: 1) distilled water or 2) battery acid. As I understand it, batteries are shipped dry and charged. When I've bought them at local auto stores they're mostly full and charged.

As current goes through the battery (charging or discharging), the lead plates heat up. If the current gets too high or for too long, the plates may bend. If positive touches negative, and they can't be straightened, you lose a cell's voltage.

If a spark occurs inside the compartment, it risks battery explosion and possible rupture of the enclosure and spraying battery acid everywhere.

Hi,

Externet said:

? Early failure of the battery as there is no voltage regulator/limiting ?
What is missing to make it work as it should ? A 10A charge controller ?

Click to expand...

It makes no nense to connect the panels directly to a battery.
So - like already shown in your ASCII sketch: you need a charge controller.

But if you have a 12V battery ... you need a 400W charge controller ... so it´s not a10 type, but rather a 35A one.

There are all informations available on how to charge batteries ... depending on chemistry.
One good start could be batteryuniversity.com
But battery manufacturers often also provide good informations, like datasheets ...

Mind: the battery voltage is not constant. It varies with: charging state, age, temperature, current, chemistry ....
So for a 12V lead acid battery you may calculate with 11.0V ... 14.4V.

The more energy you pump in (up to 100%), the lower you drain them out, the higher the current .... the lower the life expectancy of the battery.
Also due to memory effect .. batteries may faster wear out when "doing nothing" but keeping thm at a high voltage level.
Don´t ever under-discharge a battery it might result in immedaiate loss of battery health.

And in case you use multiple batteries:
* when you connect them in series: the weakest cell get´s stressed the most, getting even weaker with increased speed. The weakest cell will determine the total lifespan.
--> if the weakest cell is dead ... none of the other cells can be used. The whole system is dead.
* when you connect them in parallel. The weakest battery is stressed the least and you can use the system as long as one battery is still alive. The paralleled batteries provide some redundancy. .. with reduced capacity for sure. But .. the paralleled current will be higher, thus the charger as well as (any) the electronic load may be less effective (higher loss. Over the thumb. Read datasheets).

There are ready to buy solutions.

Klaus