Battery discharge question

Georgio

Georgio

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Ok, so I have standard wet lead/acid "leisure" type batteries and have no intention of going to AGM or Gel batteries.

What level of discharge would it be acceptable to go to without significantly damaging them before recharging. I immagine that it's around 60% (as in 40% of capacity used) but would be interested to hear your thoughts.

I now have a battery monitor fitted and want to put the info to some use.
 
Using 30% or 40% of their capacity before recharging shouldn't shorten their life significantly. However, remember that it's not that easy to recharge to 100%, so you need to know what your starting point is. Also, unless your batteries are brand new, their capacity is likely to be less than specified.
 
[ QUOTE ]
A 12v battery should not be discharged below 10.5 volts.

Look HERE for all your answers.

[/ QUOTE ]Discharging to 10.5v will kill a battery fairly quickly! The link you posted quotes a typical voltage of around 12.2v for a 50% discharged battery.
 
I think this whole question is a variable. Yes major discharge probably shortens a batterie's life. Especially if it happens often.
i reckon just try to keep batteries form major discharge but don't get to concerned if you inadvertently do discharge occasionally.
After all the battery will die of old age eventually anyway with a life shortened or lengthened a little by careful capacity management.

Not disagreeing with conventional wisdom just putting a different emphasis on the subject. olewill
 
A good summary from William H and some sound words from the other contributors. I have not yet had the time to read the link from Piers but there certainly appears to a lot of good stuff there. Note taken to read it though.

I don't think anyone will give a hard and fast rule about how much you can safely discharge a battery (other than a deep discharge one) As little as possible and as infrequently as possible I think is the best policy. Your figure of 40% would be a good one to work to I think. It would be interesting to compare your battery monitor with a rested voltage reading

On point I'll make, although it may be covered in Piers' link, is that if you you use a voltage reading as an indicator of state of charge it must be a reading taken after a period of rest, ie no load or discharge. I try to allow 12 hours and the figures I use as a guideline are 12.7v fully charged and 11.7v discharged with a linear relationship between those two and the state of charge in between . That gives the 12.2v as quoted by pvb as the 50% mark. ( A new battery still in tip top order will get a bit higher than 12.7 when fully charged)
 
Also one of the important factors that will determine the overall life of a lead acid battery is the length of time the battery is left discharged or even partially discharged.

Never leave a lead acid battery even partially discharged for any period of time.

I have some batteries over 10 years old on my classic cars which are constantly kept on an automatic charger maintaining full charge between usage of the cars
 
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