New 60Ah gel battery cycling?

[T i m]

Noted, however (and however unscientific) he rates these MK batteries against most of the alternatives.

No, but it proves my point. You can't condemn a charger 'period' if you don't take into account all the variables. The Optimate, as a 'topping off / maintenance device may actually be perfect, partly because of it's fundamentally low (current) output.

Ok. From some of their literature:

"Q: Why am I not getting the run time I expect from my new MK Gel batteries?

A: Our gel batteries are made with thicker plates than other batteries. It is because of these thick plates that we are able to get a longer cycle life from our gel batteries. The downside is that it takes longer for all the material inside these plates to become active. It takes approximately 15-25 cycles to break the battery in."

I have also just spoken to one of their tech guys and he confirmed the 'cycling' requirement. I also confirmed my technique (Draper Intelligent charger overnight followed by a 10A discharge down to

10.5V) as a 'good' way of doing this. [1]

It seems 14.1 or 14.4V ... both ok as long as the final / float is right (and at 13.5V it is).

Understood, and how I used to charge my EV racing batteries. High quality bench PSU set off load to 13.8V (via DMM) and say 4A current limit. It sits at 4A as the voltage picks up then the current drops back to next to nothing (if the battery is good) slowly after that.

Well it is possible to test for something as my Gold IBT capacity tester knows too well. ie, If I put it on this gel battery it tells me it's capacity is 13Ah, similar to the diminutive motorcycle battery standing beside it. Imperial tests have shown it to be at least 30Ah, even at the 3hr rate.

I have used this tester on all sorts of new / old, car / motorcycle / alarm / portable booster / and even Nicad batteries (inc my 3 sizes of

12V Dewalt drill packs) and it has always displayed fairly closely the capacity printed on the tin (maybe +-30% worst cases). This gel battery really seems to be 'different' and in a big way!

Cheers, T i m

[1] I have considered improving this in the following way.

Use a variable (pre-settable) ~5A current load as that would remain constant throughout the test as the voltage drops (so no compensation needed).

Using an alto cut-off / battery protector to ensure I don't over discharge (more chance of being distracted over a longer test period).

Use one of the USB voltage Data-loggers to track the voltage. ;-)

[T i m]

That's pretty well what the tech guy at MK just told me.

Which it what I believe they do. Or do they hold it there and then the current would drop away (absorption stage)?

None of the (my) chargers do that. I have just turned the DMM on after the battery has been at the charged / float stage and it read 13.52V.

Of course.

Understood.

Cheers, T i m

[meow2222]

he does, but he doesnt properly understand how to treat them correctly, or other basics, so his actions factor into the end results.

That suggets you dont understand the issues

A 24v charger, a 6v charger, or a 14.4v charger are all wrong. Yes you can charge your battery on it, but 14.4v will cause gassing, and thats one thing a gel cell has little tolerance of.

too vague to be meaningful. The capacity increase is not a feature solely of thick plate leisure battery construction. This looks like marketing talk.

I dont think it makes good sense to skimp a fiver on the charger and kill the batteries earlier, but its your call.

yup. Or you can do that with much more basic kit. =A320 should be enough, it doesnt take much to convert a 14.4v charger to a 13.8v one.

clearly that doesnt tell it whether a battery is wet or gel.

not relevant

I dont know why you want to muck about with all sorts of trivia but not get the most basic key one right. I've said enough, if you want to ignore the basics of battery health its your battery. Enjoy your outboard.

NT

[Dave Plowman (News)]

We use constant voltage chargers to charge SLA at work - and they charge up overnight just fine.

[Fredxx]

I would imagine different chargers have different characteristics, which suit the size of battery intended to be charged.

One of the problems I feel you have with a multicelled battery is that all cells are slightly unequal. One of the reasons I feel deep discharge must be avoided is that cells can get out of step.

One thought that if charge time isn't important, a float charger would be best to use but would take many hours to get to capacity, but the battery would last the longest.

Any current when the battery is fully charged (over and above the self leakage) will split the water and dry the battery. Not a good idea. To be honest I don't know what the "absorption stage" is? Batteries have a current-voltage characteristic depending on it's state of charge and it's capacity, and to a lesser extent it's age.

[Fredxx]

They probably get to 90% or more and you may not notice the small shortfall. I have seen the characteristics of lead acid batteries of capacity over time whilst charged at 13.8V - but can't recall their details.

[T i m]

Ok, but he's also a heavy user of such batteries in a day to day sense, can you bring any better facts to bear?

Yeah, course. ;-)

Let me try to help you again. A '24V charger' would certainly not be ideal of course but it's quite feasible that one with the right current limit could actually charge and maintain said battery, given time.

Not according to the tech at MK but you know best. Ok, try this, we have brought the battery up to the end of it's bulk charge state and are about to enter the constant voltage / absorbsion stage (where the current will start to taper off over the remaining charge period).

Is the battery fully charged at this point? Answer, 'No.

So, it continues to charge at the ever reducing current towards the final charge point where it's cuts off and goes into maintain / monitor mode. Just before that point the battery will be sitting at (say) 14.4 volts and the current will be next to nothing. How much surplus energy will the battery have to dissipate at this point (the point that would normally cause gassing)? Answer, next to none.

*Just* like the example I sited earlier that you so quickly dismissed with my 1000V x 1mA charger.

Or could possibly be facts? The fact that you can't prove or disprove anything doesn't change things.

Oh, you have found me the correct charger, great! Link please?

Why would I want to do that?

No? Well in a blind test of all (probably 20) batteries I have here I could tell you which one was the Gel battery using that tool and the 'expected' capacity.

To you maybe. To me it's proven to be a versatile piece of test equipment, the only thing it doesn't work on is this one battery.

I'm not sure you know what that is though do you?

1) I'm (according to the manufacturer) charging the battery in accordance with their recommendations. 2) I'm cycling the battery in accordance with their recommendations. 3) I'll be using the battery within their recommendations (if not 'idea' but acceptable under the circumstances. 4) I'll be storing it to their recommendations.

What did I miss?

That's the last thing I want to do and why I will take the manufacturers information as the last word ... unless you want to replace the battery should it go wrong though (say) being undercharged?

Thanks, I hope to. ;-)

T i m

[T i m]

Indeed. The guy at MK confirmed the charger I currently have is ideal for the job, initially charging between 4 and 6A and floating at around 13.5. I am charging it again now and will monitor the charge voltage this time.

Incidentally it says on the Draper instructions that the BCI charger draws 110W and that's exactly what the power meter socket said it was drawing. ;-)

Understood and I did confirm the maximum discharge voltage (minimum voltage) with MK to be 10.5V (on load).

Yes, and why I was happy my charger was at the low end of the permitted charging scale. I think there are realistic minimums for intelligent (they would be maximums for float chargers of course) chargers though. Having enough charge 'lift' to be able to measure the battery's reaction to them accurately etc.

Indeed not, however, at least with non sealed batteries you can top them up. I remember my electric car (with 8 x 200Ah 6V mono blocks) needing regular checks and the occasional drop of distilled water.

As I understand it these batteries / chargers have 3 key stages, bulk, charge and float.

The fist stage is where the bulk of the charge is applied, often current limited by the abilities of or settings on the charger. It doesn't matter what the terminal voltage would be for most of this because it's in a current limiting state anyway.

However, once the battery has reached it's terminal voltage (dependant on several criteria like age, temperature, charge current etc)it requires the 'absorbsion' phase where the voltage stays the same and the current then drops back to it's minimum (that again dependant on certain criteria).

From then on the charger would drop back to a float or maintenance phase where it will maintain a lower voltage (as you have also said) offsetting any self discharge etc.

The fancier chargers can prepend the bulk phase with a de-sulphation stage and others can apply tests and timers along the way to ensure the battery isn't faulty and or if it is to reduce the charge rate or repeat the entire cycle etc.

That's my best understanding of it anyway. ;-)

Cheers, T i m

[Dave Plowman (News)]

Quite possible they're not at 100% - but we carry enough for the requirement anyway. 10% wouldn't make a difference to that number.

[T i m]

Of course, when you are using batteries in a non traction role, or even when that role isn't too demanding (like the electric hire boats or forklifts that get charged weekly) then, and assuming the battery isn't being damaged by undercharging then it doesn't matter.

But in my role where I will probably require every ounce of energy out of it each trip it all counts. ;-)

Similar with my electric car. It typically had about 20 mile range. Typically it was used for 2-5 mile trips so only *needed* charging every fourth trip or so. However I took the opportunity to charge it after about 5 miles as you never knew what you needed tomorrow. ;-)

One such lunchtime return trip was calculated at about 20 miles but what I hadn't factored in was the hill in the middle. I might have remembered it had I ever had to walk or cycle up it but it was just a touch extra on the throttle in the car or on the motorbikes.

My prayers for a clean run weren't answered either, following a bus on the way up and similar on the way down (and no regen braking).

I backed off wherever I could to eek out the last few watts And must have been way below 5.25V / 6V battery). ;-(

Thank goodness I had access to a charging point at work ... it was all charged up ready for the journey home. ;-)

"I love the smell of hydrogen in the evening"

T i m

[T i m]

Not a reply to you in particular Dave (other than it mentions std 'lead' V gel batteries) but I've just been sent some data from the charge controller from someone's Camper van.

Tension : > De charge : (It's in French).

14.2Vdc Pb : 13,7V, Gel : 14,2, +/- 1%

I'm not quite sure how that breaks down but it looks like 'Gel -

14.2V' ?

is also interesting (well to me anyway) is that all the controllers covering 20 to 200Ah all use the same voltage characteristics (as they should).

Cheers, T i m