Battery dead, relay at fault?

[citronut]

years ago the battery on an old BX i used to have would be fine then one day id go to statr the car and nout, not even a glimmer on the dash,
top electralight (battery fluid ) up charge battery and away it would go for another 6ish months or so, till the fluid evaporat's to low then the same thing again,

the thing with modern chargers ( at least domestic ones at least ) is they have protection circuitry, which if trying to charge a completely flat battery the charger will switch on off on off on off on off on off constantly, till it gets a little charge into the battery before it will charge continuously,

i had one like this ( digital type ) once and it seemed like it had done absolutely nout over night,

get an old fashioned charger they just charge

regards malcolm

[Gibbo2286]

We're talking about lead acid batteries here, all that deep discharge stuff doesn't apply, that's for modern lithium and alkaline batteries.

I think the first thing the op needs to do is try a known good battery, my guess would be that he has a shorted cell in the one he's trying to charge so it's dead and going to stay dead.

[mat_fenwick]

I'm afraid I disagree there - lead acid batteries in cars are not designed for deep discharge. You can buy deep cycle lead acid batteries used in forklifts and off grid systems, but these are much more expensive.

Some interesting info here.

Alkaline batteries (and non rechargeable lithium cells) by their nature are deep discharged at the end of their life, but it doesn't matter as that's when you bin them! Lithium ion batteries can be permanently damaged (short circuited in which case attempted charging can be spectacular!) by deep discharge, but most cells/batteries have a protection circuit which shuts off when a safe discharge level is reached.

Agreed that battery looks to be the likely suspect here though.

[Dollywobbler]

I've just had a battery die very suddenly. As in I moved the car on the drive, turned it off for a few minutes, went to start it again and it was utterly dead. That turned out to be a lack of electrolyte (older style battery where you can check) which was probably caused by overcharging.

[Wooscary]

Thanks for thoughts everyone.

Jumping produced no results, and thinking more about it, the battery is at least 3 years old, but almost certainly
a fair bit older, so a good innings probably.

Friend with car acquired, new battery obtained, car started.

Cheers.

[Defender110]

I'm afraid I disagree there - lead acid batteries in cars are not designed for deep discharge.

Correct that's why they have 'Leisure Batteries' that are lead acid batteries designed for deep discharge - recharge cycles.

[mat_fenwick]

Arguably, most leisure batteries aren't true deep cycle batteries, but certainly better at coping with it than normal starter batteries. The one I linked to can do 3200 cycles to 50% capacity (but at a cost!), whereas a starter battery could maybe do 100-150 cycles. A leisure battery would be somewhere in the middle.

Anyway, back OT - any developments on the flasher unit?

[Birotor]

By applying the same system of management to standard off the shelf car batteries as I used on my multi million GBP submarine batteries I cannot remember when I last got less than 7 years out of a car battery....

[Vanny]

If you have a dehumidifier the water collected by that can be used

bloody hell, your brave, the amount of crap that ends up all the dehumidifiers i've ever seen i'd want to strain it before putting it down the drain! Try checking the pH too, i bet its acidic!

[Dollywobbler]

Stuff out of my dehumidifier was very clean (mind you, it doesn't get serious use). Is acidic a problem? Not like battery acid is alkaline is it?

[Birotor]

If you are have to regularly top up a lead acid battery on an alternator fitted car your voltage regulation is up the spout! Gassing should be negligible.

[Geoffrey Gould]

Hi we used to use Exide batteries when they were available and they were good for 8 years, when 'sealed for life' batteries came out then we found that they suffered sudden death, usually just outside of guarantee, turn off and then go to start, after a while, and completely dead hardly enough to light the ignition light. This was on a range of vehicles and wondering why I cut the top off of one and it was almost dry, just a little electrolyte in the bottom of the cells.Cutting the rest of the dead ones open then they were the same.
If it had been one vehicle then a possible charging fault would have been possible but this was on anything from small vans to transit sized stuff. Built in failure??
G.

[mat_fenwick]

Doing a bit more reading (as I find this kind of thing interesting) I found out that maintenance free lead acid batteries don't actually capture any lost electrolyte, but contain extra to allow for that which is lost during normal use (which is a much smaller amount than in the past, due to modern construction methods. The extra amount supplied when the battery was new effectively limits the life, as once that's gone that's it. So if you can remove the caps on a 'maintenance free' battery, topping up when required could extend the life.

bloody hell, your brave, the amount of crap that ends up all the dehumidifiers i've ever seen i'd want to strain it before putting it down the drain! Try checking the pH too, i bet its acidic!

I'd certainly get rid of any floaters, but ours is run for a couple of days whenever we do a clothes wash and it's raining (that would be every week then) and is clean. It's amazing the amount of dust collected by the filter though!

[Birotor]

For the record submarine batteries were made by Exide in the Manchester factory but were labelled Tudor. The loss of electrolyte by gassing is likely to be caused by gassing during charging and s/ms used to do Quarterly Discharges followed by Charging and Gassing for several hours - very unpopular with the smokers as there was a lot of hydrogen generated by 4 x112 bloody great cells - (at full power we had 880 volts across the main motors in parallel). Gassing should not occur with alternators but is difficult to avoid in conventional off car charging which I never do. The gassing voltage changes as a battery ages and you could see it start down the filler holes in the old type batteries. All my batteries are on low rate float when the car is in the garage (I can reach the lead while still in the car - its a long curly cord lead from the cig lighter skt) and three monthly I leave the charger off overnight with the side lights on and then reconnect. I first had this set up in 1974 when I had a GSA. In the days of dynamos Top up WAS necessary and I always used demineralised (deionised) water which was shared with my wife's steam iron. Back in 1956 at the RN Engineering College at Keyham we used to un-sweat the battery tops (held in with bitumen in those days and clean out the sludge and repaste the plates. Grinding away trying to start cars with crap ill maintained ignition distorts the plates and can cause internal shorting as the paste falls out into the bottom of the cell and shorts the cell out.
None of which explains why all my batteries last SEVEN years.. I must be getting something right.

[Way2go]

Generally, if the battery is in good condition, it should not be necessary to use a charger if the car is driven a reasonable distance each week and not subject to numerous short shopping runs.

In actual fact, regular use of a charger can damage the battery, shortening it's life, not just for the gassing mentioned but because domestic chargers are rather crude devices in terms of their smoothing. This can shake the plates with 50Hz ripple on the DC which ultimately leads to shorted cells. The on-car alternator operates at higher frequencies thus reducing the adverse effects of any such shake if ripple is encountered, its effects also reduced by the other imposed loads in the car operating mode.