Expected life of a car battery?

[griston64]

Originally Posted by Laird Scooby

They still won't work with a completely dead battery which is what is being looked for. Good kit other than that.

It worked on the dead battery from my breaker

[griston64]

Blurb form booklet "a special Recond mode for reconditioning deeply discharged batteries".

[Laird Scooby]

Originally Posted by griston64

It worked on the dead battery from my breaker

When you say "dead" Mark, was there any life left in it? As in able to run a small bulb?

[griston64]

As it was dead I didn't bother to check it's level of actual deadness ( I know that not even a word ) This is heading into Parrot sketch territory

[Laird Scooby]

Originally Posted by griston64

As it was dead I didn't bother to check it's level of actual deadness ( I know that not even a word ) This is heading into Parrot sketch territory

From what i understand of Ellies dads problem, the battery he has is totally dead, no life in it at all. Some batteries can be dead but recover enough to give a small output voltage which is enough to trigger the circuitry in the "intelligent chargers" which then do a great job of charging and sometimes reviving the battery.

The "fick" chargers don't differentiate and will provide voltage even on a dead battery (also handy for electrolytic de-rusting as what you create is a form of uncharged battery in the process) which can start the charging process and sometimes swapping to an "intelli-charger" can be advantageous.

As you can see, it wasn't a "Dead Peugeot Sketch" type question, it was in fact a genuine question.

[Forrest]

A 12V car battery is generally regarded as “dead” when its output drops to 10V or lower. I have managed to revive one measuring 2V. It did not have enough output for the charger to recognise that it was connected to a battery but the Ctek has a “supply” mode where it outputs constant 13.6V supply so I ran it in this mode until the battery had enough charge to be recognised and then switched to the “reconditioning” mode which includes an over-charging stage to reduce sulphation.

I think the reconditioning mode is designed to revive a battery that’s got down to about 5 or 6 volts. They also recommend using it proactively occasionally to keep a well-maintained battery in top condition.

[Laney760]

Hi. From what I gather his old battery doesn't hold a charge for long. No idea why he just doesn't recycle it and get rid of it but he is obstinately determined to find out what is wrong with it! He is annoyed that it's sealed and he can't check the cells like he could on his older batteries. He said he wanted a trickle charger so I thought I'd get him one so he could 'tinker'.

On reflection I'm sure the trickle charger will come in handy for him one day!

[Laird Scooby]

Originally Posted by Laney760

Hi. From what I gather his old battery doesn't hold a charge for long. No idea why he just doesn't recycle it and get rid of it but he is obstinately determined to find out what is wrong with it! He is annoyed that it's sealed and he can't check the cells like he could on his older batteries. He said he wanted a trickle charger so I thought I'd get him one so he could 'tinker'.

On reflection I'm sure the trickle charger will come in handy for him one day!

Ah! In that case Ellie, get him one of these, connect it to the battery with the trickle charger and leave it alone for 2 months, switching the charger on and off every 3-4 days - 4 days on, 3 off would be a good way to start.

http://extralifepulse.com/pages/extr...terypulse.html

It sounds very much like the battery has sulphated so that little gizmo should do the trick in conjunction with the trickle charger.

I understand his determination, i very often get like that myself and spend far too long chasing a lost cause to actually get to the bottom of it. That said it sounds like your dads battery may be recoverable so it's worth a try and definitely cheaper than a new battery!

PS they also sell those battery desulphators on ebay but it's cheaper buying direct because of ebay P&P

[mister grimsdale]

Originally Posted by Laird Scooby

You'd need at least a 10W solar panel Lee, just to cover in the winter. That's for the basics - clock, ECUs etc but if you have an alarm, tracker or anything else non-standard you'd need more. In winter you have at best 6 hours of daylight - to get charge you also need sunlight so a 10W is a conservative estimate as well.
It also needs to be angled to face the sun for the best effect which this time of the year means it will be near vertical.

This set me thinking.

Using your figures from upthread for background consumption, 50mA is 600mW, or about 450Wh a month. 50mA would discharge a 70Ah battery to 10.5V in a couple of months, so any solar top-up needs to deliver that sort of output on a timescale of a month or two.

The nominally 4kW array on my roof, which is pretty well optimally aligned, delivers between zero and 5kWh a day at this time of year -- typically about 60kWh a month. All other things being equal, then, a 10W panel should yield about 150Wh a month. That's not enough to keep up, but it might just extend the discharge time long enough to get through the winter. Seems like you'd need at least a 30W panel to keep fully topped up, and more if, as you say, there's other equipment.

No problem in summer, when I'd expect 1.5kWh a month from a 10W panel.

My panels are ten years old, so a modern one might be a bit more efficient, but I was surprised how big the shortfall appears to be. Of course, this is all theoretical. Anyone done the experiment yet?

[Laird Scooby]

Originally Posted by mister grimsdale

This set me thinking.

Using your figures from upthread for background consumption, 50mA is 600mW, or about 450Wh a month. 50mA would discharge a 70Ah battery to 10.5V in a couple of months, so any solar top-up needs to deliver that sort of output on a timescale of a month or two.

The nominally 4kW array on my roof, which is pretty well optimally aligned, delivers between zero and 5kWh a day at this time of year -- typically about 60kWh a month. All other things being equal, then, a 10W panel should yield about 150Wh a month. That's not enough to keep up, but it might just extend the discharge time long enough to get through the winter. Seems like you'd need at least a 30W panel to keep fully topped up, and more if, as you say, there's other equipment.

No problem in summer, when I'd expect 1.5kWh a month from a 10W panel.

My panels are ten years old, so a modern one might be a bit more efficient, but I was surprised how big the shortfall appears to be. Of course, this is all theoretical. Anyone done the experiment yet?

There are easier ways of working it out. This time of year you'd be lucky to see 6 hours of usable daylight (usable in terms of the brightness being enough to get the voltage from the solar/PV cell high enough to charge) so during that time, it outputs 10W to the battery.
Because 6 hours is 1/4 of a day, that means that 10W/hour is spread over 24 hours os is the same as saying 2.5W/hour.

If the current drain is 50mA, the wattage drained from the battery will be nominally 12 x 0.05 = 0.6W = 600mW/hour. However the solar panel (on a good day) is feeding in 2.5W/hour on average - bear in mind the 6 hours usable daylight.

Very simply, that means it's replacing 4 times as much as is being used in "perfect" conditions. Even if you say 3 days out of 4 are no good because of cloud cover etc, on the one day it is good enough it still covers.

No need to get into monthly calculations, just daily and even that can be rationalised into the part of the day that's useful - daylight. As long as what goes into the battery during that period matches or exceeds what is being taken out, it's all good.

It's also no good waiting for a battery voltage to drop to 10.5V as by then, it's considered flat :



The lowest realistic voltage that a battery could be expected to start a car that starts easily would be ~11.8V but even that is optimistic, 11.9 or 12V would be more hopeful. With the normal drains (clock, ECU, alarm etc) this is likely to happen after about 10-14 days, depending how well charged the battery was at switch-off, ambient temperature, overall state of the battery (sulphated badly or not) and several other factors.