any battery experts

[Macski]

Battery new Feb last year, left on a car for four months it is not surprisingly flat. Recharged it for 24 hours but it still empty. Jump started it but after running a few minutes it stalled, jump started ot again it stalled again.

Charged it again but it won't work, When I first connect the charger it showed a charge of 3 amp charge but falls to 1amp.

the shop said it needs a charge boosathamp, my charger does 10 of at least 6, my charger does 9. I also put it on a 1.5 intelligent charger but no luck

anyone with advice please

[tapkaJohnD]

A lead-acid battery that is allowed to go flat and stay that way for any time, is a dead battery. The lead plates inside cannot reconstitute themselves after so long.

See the Battery University webpages, eg: https://batteryuniversity.com/learn/article/lead_b...

JOhn

[Macski]

Thanks, I will read the link later.

The car has been off the road 4 months, the battery was not left flat, the alarm started bleeping and I charged the battery

[GreenV8S]

Macski said:

the battery was not left flat, the alarm started bleeping and I charged the battery

What was the battery voltage before you charged it? Four months is enough to flatten the battery on many cars.

[Macski]

GreenV8S said:

What was the battery voltage before you charged it? Four months is enough to flatten the battery on many cars.

battery was flat, not sure what the voltage was, but simply letting a battery go flat
should not kill it should it? My MR2 stood for six months while flat the battery was still good.

Getting a trickle charger for future use.

[227bhp]

Welcome to real life where batteries go flat when you leave them connected to cars with alarms and they get so flat they don't amazingly rejuvenate.
It's tough out there so be careful, but we'll help you through.

[GreenV8S]

Macski said:

simply letting a battery go flat should not kill it should it?

It is likely to kill it completely, or substantially reduce the capacity. Automotive batteries aren't design for deep discharging.

[Penelope Stopit]

Guess it's a mystery that many dead flat lead acid batteries have been emptied, filled with fresh sulphuric acid and water mixed to a specific gravity of 1.250, placed on charge and later lived to fight another day

Perhaps it's a touch of luck that the majority of them lived on

[elanfan]

Presumably it’s still under guarantee?

Shop should replace it, you’ve taken more than reasonable action to recharge it!

[Dogwatch]

Macski said:

Getting a trickle charger for future use.

Get a battery conditioner such as a Ctek rather than a boggo trickle charger which may keep shoving charge into the battery when it is fully charged. I bought a Ctek accessory which allows the conditioner to be hard wired to the battery via a quick release plug in the charger lead, very useful.

[Macski]

The car has been off the road for 3 months not four.

I know keeping a battery flat over long periods is not good for it, but I thought allowing the battery to go empty is good for the battery.

Although when I bought a gel battery it came with a little sticker with a warning not to allow it to go flat.

Edited by Macski on Sunday 20th October 05:05

[Twig62]

I know keeping a battery flat over long periods is not good for it, but I thought allowing the battery to go empty is good for the batt

Edited by Macski on Sunday 20th October 05:05

[/quote]

No it is not.

[Macski]

Twig62 said:

I know keeping a battery flat over long periods is not good for it, but I thought allowing the battery to go empty is good for the batt

Edited by Macski on Sunday 20th October 05:05

No it is not.

Now I know!

[GreenV8S]

Macski said:

I thought allowing the battery to go empty is good for the battery.

Being deep discharged is very bad for the type of lead-acid batteries used in cars. It can easily kill them, and if they survive they are likely to have significantly reduced capacity. It's possible to get storage batteries which tolerate deep discharge, but they are not commonly used on cars.

[Macski]

So what is deep discharged?

The battery is relatively new and although yes I left it for three months how much can the car drain the battery?

[GreenV8S]

Macski said:

So what is deep discharged?

The normal guideline is to keep it above about 20% of its nominal capacity to avoid damage. That means keeping the resting voltage over about 12.2V. When the resting voltage comes down to 12.0V the battery is completely discharged.

[227bhp]

Cars drain batteries if you leave them long enough.
Think about it, when you turn the key it's remembered all the engine ECU codes, what radio station you were tuned into and kept it secure via the alarm with a little red flashing light. All this takes power.
It's done quite well at that, some flatten their batteries in 3 weeks if left.

[Macski]

227bhp said:

Cars drain batteries if you leave them long enough.
Think about it, when you turn the key it's remembered all the engine ECU codes, what radio station you were tuned into and kept it secure via the alarm with a little red flashing light. All this takes power.
It's done quite well at that, some flatten their batteries in 3 weeks if left.

I get it but it is a big battery to power things that use little energy and it was summer, believe batteries last longer in the summer. The battery on my MR2 lasted 6 months and it is older and that was through winter, although it was flat it still managed some power to turn over the engine a little.

Out iof interest why do cars need power to remember codes? If my mobile goes dead, or my camera it will remember its settings.

What happens with the ECU codes now the car has not had power for two or more weeks?

Related question, learnt today a Ford Focus battery for a 1.6 diesel costs £150 and goes up to £230, why are they so expensive?

[GreenV8S]

Macski said:

Out iof interest why do cars need power to remember codes?

It's security measure.

[Penelope Stopit]

GreenV8S said:

Macski said:

Out iof interest why do cars need power to remember codes?

It's security measure.

If the heart is switched off the brain stops functioning