Charging cycles question

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undead
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Charging cycles question

Question for those of you out there who know a lot more about batteries than I do (which makes it pretty much everyone here ;) )

So the Vectrix manual says 1,700 charge cycles alledgedly before it starts to have problems or lose power or whatever.

Now lets say that for a week it only runs down to just under halfway before I charge it - does that count for 3 and a half charges, or does it not count for less or more if the battery is only half charged from full?

chas_stevenson
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Re: Charging cycles question

First of all, you should never leave Lead Acid batteries in a discharged so you should charge after every use. Each charge is considered 1 charge cycle.

Second, you can't think of this as you would a gas tank which can be half full. Batteries are either charged or in a discharged state. The amount of discharge makes a difference as well.

Third, amount of discharge. I would recommend never using Lead Acid batteries past 60% of their amp hour rating. So if I have a 100 AH battery I should only expect to have 60 AH of usable charge. A 20 AH battery would yield a 12 AH usable charge. Discharging the batteries lower will greatly reduce the number of charge cycles they can endure.

1700 charges???? I wish I could get half that from a set of batteries on an EV. Because an EV uses the batteries much harder than the standard discharge test they don't last as long as they do on a test bench.

I am sure there are other opinions here and I hope they also post. The more information you get the better you will understand.

Grandpa Chas S.

undead
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Re: Charging cycles question

Would it make a difference being that they are NiMH and not lead acid?

chas_stevenson
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Re: Charging cycles question

Yes it make a difference. With NiMH you will get a lot closer to the rated value of the pack, about 85%. These batteries also don't get very upset when left with a partial charge.

Each charge still counts as a cycle.

NiMH may get 1700 cycles if you do not over charge or over discharge them.

As far as I know their worst enemy is heat. They can get very hot during charge or discharge so it is best o keep them as cool as possible. A really good NiMH charger will have a temperature sensor to monitor the heat during charge and compensate.

Hope this helps,
Grandpa Chas S.

Mik
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Re: Charging cycles question

It is really a question to ask Vectrix dealers. But you might not get a reliable and useful answer.

I am not sure if they changed their advertising hype, but they used to claim 80000km and 1700 cycles and 110km range....

80000/1700=47km per cycle.

That is about the real world full range and half of the claimed range.

Therefore each of the cycles claimed should be between a full and a 50% discharge.

But that is all theoretical nonsense!

You will most likely get more kilometers out of a NiMH pack if you recharge frequently. Plug it in whenever you can and unplug when charging has finished.

Avoiding recharging to keep the cycle count lower will have a deleterious effect on the battery pack.

This information may be used entirely at your own risk.

There is always a way if there is no other way!

undead
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Re: Charging cycles question

Cheers

I have asked Vectrix the question today as well, waiting for a reply.

Sandy
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Re: Charging cycles question

Hi Folks,
First things first. Ni-MH cells are a totally different animal compared to Lead Acid cells.
Whilst you should never leave Lead Acid batteries/cells in a discharged condition for more than a matter of hours, Ni-MH cells can be left in a state of discharge for long periods weeks even, without damage/deterioration.
The real question is how do we obtain maximum life from the Ni-MH batteries as are fitted to the Vectrix? An excellent source of technical information can be obtained from Duracell. I can't just now locate the website but I do have a copy of the Pdf file.
What I have quickly learned is that there are various factors that will limit or reduce the cycle life of Ni-MH batteries.

On Discharge (in use on the Vectrix)
a/ The regular (normal) discharge current should not be greater than the Ampere Hour Capacity. i.e. 30 Amperes. This gives a useful power output of Five H.P.
b/ Higher currents than in a/ above may be used intermittently but should be balanced by periods of lower power use, the result should be that the battery should be discharged over a one hour period of use. Faster Discharge causes heating and a lower total out of electrical energy.

On Charging, there are a number of things to consider
a/ The battery temperature should be between 10Degrees C and 30degrees C (50 to 86 degrees F).
b/ The Maximum rate of charge should not exceed the Ampere hour capacity of the battery.
c/ The Charge in ampere hours should not be more than 110% of the discharge in ampere hours.

Overcharging the battery will shorten its cycle (service) life.

General Points.
Discarging the individual cells to less than 1.0 Volts per cell will shorten the battery life.
Ideally the battery should not be discharged to less than 10% of it's total capacity.
Ideally the battery should not be charged rapidly to more than 90% of it's maximum charge capacity. A slow /Low rate 'top-up' charge of 1/30th to 1/20th of Capacity (i.e. 1.0 to 1.5 amps) can be used for a couple of hours to bring the capacity to near 'full'.
At no time should the battery temperature be allowed to exceed 86 degrees F when being charged.

All of this does rather leave one with many questions. Not least of all being, Is there a current limit on the charge provided by regenerative braking when the battery is 'hot' i.e. nearor at 86degrees F? Is the charging system similarly controlled?

By all accounts the so called 'memory effect' (the correct name is Voltage depression) is minimal (Duracel say that it will not exceed 5% of the battery capacity). This would seem to render the 'necessity' for ocassional 'deep discharges'suggested by Vectrix as being unnecessary. Indeed, they may well reduce the cycle life of the battery.

I hope that some of the above information will help the readers understanding of the workings of the Ni-MH battery as fitted to the Vectrix.

I shall try to deal with any questions which arise from this article. Please remember that I an offering information which I believe to be accurate and informative. I am not telling you how to do anything.

Sandy

Mik
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Re: Charging cycles question

Hi Folks,
First things first. ........

That is a good summary! Thanks!

This page has been added to the Vectrix Collaborative Handbook, please stay on topic!

This information may be used entirely at your own risk.

There is always a way if there is no other way!

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