Current draw for running a petrol fuelled car

That might well be the case for many who don't know any better. However the difference between running a generator and intermittently recharging a battery say in a narrow boat and the same in conjunction with a solar panel can be twice the battery life.

Ignorance is often bliss.

I was thinking of the real world rather than an ignorant one.

I understand. The battery will still be taking a charging current at the stabilised voltage and take quite a time for it to drop down to a few amps if the charging voltage is just 13.8V

For narrowboats, before solar cells became the norm, it was often said with limited time charging, you would only recharge up to 75-80% capacity. That also meant cells became sulphated more quickly than if the battery was maintained in truly fully charged condition.

Aww bless.

WTF are you trying to change the goalposts to now, talking about DoD / lifespan?

The chances are I have had a PEV longer that you (30+ years)?

How many LA powered EV's have you designed, built and raced?

How many LA batteries are you currently using / maintaining, OOI?

How far can your C5 go on one charge with the std spec battery?

How long does your electric outboard run on full throttle?

And changing the subject, disingenuous.

It appears you weren't, eh.

Now, try again with some real facts and without trying to squirm out of it.

Cheers, T i m

Not sure about that ...

Or, the battery has already been fully charged (to a higher voltage) and is now sitting at a balanced voltage.

Not 'experienced' then?

No, really? Fancy that?

Again, no s*1t Sherlock.

And what of the plate erosion when keeping the battery sitting at a higher charge state? What full-charge SG would you recommend on a long life LA battery? What minimum DoD would be required to prevent irreversible sulphation buildup and how might you reverse it?

(That should give you a bit of reading to do). ;-)

Cheers, T i m

It goes bang just the same. ;-)

I'm not convinced charging a lead acid to a genuine 100% is actually good for its life.

Whilst you may be right, that could well depend on a whole load of other things ... like ...

If you need to have a battery on standby for emergency use (UPS say) then you (typically) need the most power available (from a given capacity solution) and the batteries themselves are often seen as consumables.

Not a dissimilar situation with LA powered vehicles, where range / runtime may already marginal (I don't know of many instances where people have too much battery power and fit a smaller one). ;-)

Where you are having to run a 'smaller than optimum' capacity battery because of space or weight (like a small motorcycle / scooter). The battery in my Yamaha YP250 is the exact same size as in my APC 600VA UPS's for example.

So UPS's and many motorcycles often keep their batteries at around

100% charge ('battery tender' on a bike) because even if they lose a bit of power they might not manage what is expected of them (powering your server for long enough or starting your bike). It's also difficult to accurately determine anything other than 'not fully charged' and 'fully charged', without continuous power monitoring etc.

Of the many LA (typically) traction batteries I have here, I give most a topup charge every few months, typically by leaving them on an Optimate Smart charger overnight.

I might also give them all a reasonable discharge (never more than

50%) and immediate recharge once every so often, especially if they haven't been used for real for a while.

I have an adjustable load auto-disconnect jig for doing that and often log the discharge process via a power meter and the USB Voltage logger so I can keep a check on the capacity.

'You can manage what you can measure.' ;-)

Cheers, T i m

Then that is even more pertinent. LA batteries lose their capacity with time. Keeping a standby one topped up to maximum may well mean its capacity when needed is well below that when new.

Yup.

But that's the 'nature of the beast'. ;-(

When I buy and / or 'activate' a LA (particularly) battery I know the clock is ticking. That clock can be slowed to some degree by how you keep the battery (temperature, vibration, charge state, DoD etc) but you can't stop that clock. ;-(

The good thing is that LA batteries are getting a reasonable amount as scrap and lead is one of the most efficiently recycled metals (or materials for that matter) ...

Cheers, T i m

Longest live LA I've ever had was on my last BMW. Did 11 years. Worked just fine then failed suddenly. That was longer than the Yuasa standby SLA in my alarm managed. Which was at domestic temperatures and on a constant float charge. Rather more ideal conditions than in a car. ;-)

Last car one I scrapped got just over a fiver. New cost over 100.

Really, for backup use, Li-Ion would likely make economic sense, now the prices have come down. Since they tend to have state of the art chargers too.

That's going some.

I think the one in the kitcar must be a similar age and has actually had a pretty hard (abused) life.

The battery in the alarm had failed (unbeknown to me) and was constantly taking charge and flattening the main battery. I would go to it and it would be F L A T, not even an ignition light.

So I treated it to a dose of a chelating agent (EDTA powder), charged it for a few days on the Optimate and it's been fine for years. ;-)

Probably a link between the cells had been eroded over the years?

I think it can be swings and roundabouts. An SLI battery at least generally get's some regular level of discharge / charge, albeit as you say, whilst going though a range of temperatures, loads and loads of bumps and vibration.

Your std alarm / UPS battery is not doing anything for most of it's life and so forgets to be a battery. ;-)

They were down to about 50p.

I've seen folk (on Youtube) using supercapacitors instead of SLI batteries in their car and it appears they work pretty well?

Cheers, T i m

Acceptance at last.

Lead acid? Really? So old hat.

Then you will understand that fully charged will mean different things to different people. If not, if you were asked the above questions your would reply 'no' or 'none' to all.

Furthermore, you should answer how many chargers have you designed and built for various systems, from alarms to UPSs.

No change.

I guess you may well be right, what most consider real world is often out of ignorance. Fully charged to you may not be the same for someone who wants to maintain a battery with maximum capacity.

No squirming, just because you think a charge level of 90% for a battery makes it fully charged doesn't make it so for those less ignorant. Real world or otherwise.

There is a general consensus that any lead sulphate on a plate in a discharged condition will change to a crystal form of sulphate which can't undergo reversal under charging.

As others have said corrosion is also an issue so a maintenance voltage of 12.6V is ideal to keep a 'fully charged' battery in top condition with minimum corrosion. Most chargers don't bother and simply keep at 13.7V.

Another issue with stationary wet LA batteries, not used in traction for instance, is stratification where the acid concentration varies in each cell. Equalisation charging is used for a short while on a periodic basis to cause bubbling to mix the acid.

Given the fully charged voltage of a lead acid is 2.2v a cell, making a

12v one 13.2, I'm not sure how 12.6v is going to keep it fully charged?

You are one strange bunny. ;-(

What, 30+ years ago?

Will I? I can agree that different levels of charge will be achieved under different circumstances but that's not the same thing as you are desperately trying to suggest.

What are you going on about now!

Many. Now, your EV history ...?

Even more disingenuous.

Oh how they twist and turn.

If you are saying that the ignorant (of battery storage technology) might not know when a battery is fully charged then you are right. Just like they might not know much about most things, but that wasn't what you were saying.

And now we are moving the goalposts as well. What someone may *set* the maximum charge to isn't the same as what *is* actually a fully charged battery.

Where have I said that!

Ironically, you have just suggested that so you are contradicting yourself!

May I suggest you give up before you dig the hole even deeper. ;-(

Cheers, T i m

Why the differentiation? Please don't say that the movement in the traction battery always 'cures' stratification.

That's not the issue with stratification. It's typically an issue with

*every* cell (in a wet cell battery).

No, it's used on every charge as part of the final balancing stage (in an ideal world).

If you are going to Google this sort of thing, try to actually understand what and why before quoting it. ;-(

Cheers, T i m

And finally,

No moving goalposts, this whole threadlet was because you couldn't accept this small but subtle point.

It goes a very long way to help. You're bing either disingenious or ignorant to imply otherwise:

But more prevalent in an application where battery movement doesn't aid mixing.

In an ideal world, yes. But we are talking about real world here.

One could say the same for someone who says, "Please don't say that the movement in the traction battery always 'cures' stratification" without providing detail. In most real world case, 'always' is rarely true, in general there will be exceptions.

Why on earth would I 'accept' your warped view on things?

Typical left brainer attitude.

Cheers, T i m