Calculate Gel Battery Life

[darwenn]

Hello, I think to get a GEL 12V 95A / h battery see two maybe

Currently I have 330w 12v in solar panels coupled to 3 diesel car batteries, it works but after 2 years of car batteries, they let me go (it's scrap for scrap so it doesn't help)

I would like to know the formula to calculate the autonomy of a 95 Ah 12v battery if I pulled for example 100w continuously at night (therefore excluding panel load)

A GEL battery having a better efficiency than the 30% of a car battery, I would like to know.

Thank you and all my best wishes for 2013

[dirk pitt]

if your battery is 100% charged it potentially contains 95 * 12 = 1140Wh (and not W / h by the way)
if you consume 100W, you could in theory do it for 1140/100 = 11.4h but then the battery would be at 0% charge which is not good for its lifespan.
you must avoid going below 20% DOD on a deep discharge lead (if it is one)
100W in 12V draw about 8A which is <C / 10. it is therefore correct. if the current drawn is greater than C / 10, the battery capacity decreases (Peuker effect)

[darwenn]

Thank you, unlike lead type car a gel battery can be fully discharged, but anyway my inverter has a safety, it cuts if the voltage drops below 11 volts, so normally there is no risk for the battery.

[dirk pitt]

yes, certainly it can be fully discharged but not too often, as I said, otherwise the life will suffer.

[Forhorse]

+1
And if you wait until the battery is at 11V to cut, your battery will die quickly (it won't last longer than your recuperated batteries)
To size a battery, we generally take 20% depth of discharge (or 80% remaining), which means that we have to take 5 times what we need. Exceptionally we can go down to 50%
Any deeper discharge seriously damages the health of the batteries (see the curves given by the manufacturers)

[darwenn]

On the other hand, the seller of the supposed gel batteries that I found on the net offers me this model:
http://www.batteries-service.fr/pour-vo ... undra.html

Model: Tundra L5 E595 95Ah 900A Car Battery

I would like your opinion, because they are obviously car batteries, and not GEL batteries for solar.

Can you confirm what these batteries are really worth?

and what does "Ca / Ca metal" technology mean?

[elephant]

There are 2 battery races:

buffer batteries (such as cars and alarm systems)

traction batteries (like those of clarks)

These are more designed to work in charge / discharge cycle

The residual voltage of a battery is measured in (de) charge, because when empty it means nothing, the discharge should not exceed 1 / 10th of the capacity. (to be clear, if your battery has X Wh of capacity, it should not be allowed to flow more than X / 10 Wh in continuous mode. transient peaks of a few minutes are acceptable)

In alarm, we are used to consider that if a battery is discharged up to 10.5 V, it has a good chance of surviving. the 11 V of your inverter is therefore very good.
If it has dropped below 8,5 V, it will no longer live very long.

Ah yes: the batteries are cozy: 15 to 25 ° C is good. Do not charge them in a poorly ventilated room (otherwise boom!)

[darwenn]

Thank you Elephant, but what about the batteries offered to me above? is it better to invest in a real 100 Ah GEL battery rather than in two of these batteries that are offered to me?

[elephant]

These batteries are not made for that. However, they tolerate the huge current demand from starters, but that is not what you are looking for.

Put more money in traction batteries, Yuasa, Sonnenschein, Fulmen, etc., made for the charge-discharge alternation.