How low to run non-leisure battery?

[CaptainBob]

Until my existing "low maintenance" engine starter type batteries are kaput, I'll be using them to run my laptop (as I am right now). As they're not designed to deep cycle too often - how low can I run them so as to get a reasonable lifespan out of them?

At present I'm showing 12.15V under load and 12.58V when not under load, so I'm assuming I'm OK for the moment?

TY!

 

[Billjratt]

Evidently it will sustain damage if you let it go below 10.5v. It will not neccessarily be obvious at the time, but the first chemical steps on the road to ruin will have been taken.

 

[VicS]

I don't think there is a hard and fast figure. From the Squadron Batteries website:

Each battery has a certain life expectancy based on a number
of cycles (or number of times used). Many factors affect
the cycle life (battery technology & construction, charging
method and ambient temperature) but it is the depth of
discharge a battery experiences that is of key importance.
In short, the deeper the discharge, the shorter the life
span of the battery.
Thin plated batteries which suffer 100% discharge will last
only a small number of cycles. A more technically advanced
AGM or Gel battery however offers more cycles and can
last up to five times longer than a conventional battery.

I would avoid exceeding 50% discharge (that's about 12.2 volts no load) but if you can keep it smaller than that you will get more life from them.

It is also important to recharge as soon as possible as leaving a battery in a discharged or partially discharged state will also shorten its life expectancy.

 

[CaptainBob]

That's good then. I'm finding I can get approx 7 hours on the laptop before it's below 12.5 no load at the moment.

Cheers chaps : )