Lead acid battery: maximum charge and discharge power?

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Lead acid battery: maximum charge and discharge power?




by Christophe » 06/04/09, 13:46

Topic dedicated to the dimensioning of buffer or lead storage batteries. The question is simple: in order to optimize their lifetime, how many amperes can be drawn on lead acid batteries (12V) according to their capacity in Ah? Same question in charging current: what is the optimal charging current (min? Max?)?

My question is not "innocent" since it concerns this paddle wheel project.

“It is said” that the load should generally be in A of 1/10 of the capacity in Ah.

Thus a battery of 100 Ah should be charged under a maximum current of 10 A in 10h. So questions:

a) Is this still true with "modern" maintenance free batteries (has technology really changed?)?

b) What about reloading under the bonnet (do all the alternators make more than 50 A and no car battery has 500 Ah)?

c) And for the discharge? How many seconds can you draw how many amperes compared to the capacity of the battery?

d) Many fast chargers exist on the market: are they flinging the batteries?

In short, full of useful information to properly size a buffer battery or renewable energy storage. Thank you for the details.
Last edited by Christophe the 06 / 04 / 09, 15: 31, 2 edited once.
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Alain G
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by Alain G » 06/04/09, 14:02

Christophe

It is easy to judge the battery discharge, any good inverter or battery discharge protection and it will stop itself when the batteries are too low so no need for regulator or other battery monitoring systems.

For the regulation of overload you buy a good charger of 20 amps and you recover the regulator, if all the protection of the batteries that you need will be there.
:D
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by elephant » 06/04/09, 15:00

Generally, lead-acid batteries have a number of indicated values, including the maximum (peak) discharge intensity accepted (usually acceptable for starting the vehicle).

For charging, a generally accepted value for a maintenance-free battery is that it is fully charged in 24 or 48 hours. (for a battery that has delivered its rated capacity)
The tenth of the capacity seems to me already very strong steady regime: at this pace there, it heats!
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by Christophe » 06/04/09, 15:22

Alain G wrote:It is easy to judge the battery discharge, any good inverter or battery discharge protection and it will stop itself when the batteries are too low so no need for regulator or other battery monitoring systems.


Yes, the one I have has "low battery voltage" protection, but that doesn't really answer the question I'm rephrasing: how much amps to draw to save battery wear? In other words: how much to use a battery to optimize its life?

Alain G wrote:For the regulation of overload you buy a good charger of 20 amps and you recover the regulator, if all the protection of the batteries that you need will be there.
:D


Well logically it will be self-regulated, right? Let me explain: the generator that I am going to use (from a wind turbine) already has a regulator (Three-phase -> 12 V DC) so if the battery is "full", the current demand and therefore the load on the generator will be weaker ...

elephant wrote:Generally, lead-acid batteries have a number of indicated values, including the maximum (peak) discharge intensity accepted (usually acceptable for starting the vehicle).


It's just but not systematic and is this value worth for how many seconds?

I found 2 values ​​for 2 180Ah batteries: 1000 and 1200A. So we can say that in A roughly speaking 5 * the capacity in Ah?

On smaller batteries it is closer to 8 *.

Problem: what does "start" mean? 3s? 5s? 10s? :)

Battery 12 V / 180 Ah
Dimension 513 x 223 x 223 mm
Starting intensity (EN) A 1000 (GUARANTEE HIGH POWER TO START)


12V Battery 180Ah
Intensity at startup: A 1200
Dimensions L x W x H in mm: 513 x 223 x 223


If not, is the 24 to 48 hour "rule" really still relevant? Because on a car this is never the case (and it never has been)!
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by dirk pitt » 06/04/09, 15:53

First, there are several technologies of lead batteries (since you talk about lead because otherwise there is also nickel, lithium, etc.)

the batteries of cars also called starter batteries are different in their constitution of so-called traction or servitude batteries (for vehicles or for photovoltaic buffer)

the starter batteries have thin plates favoring high intensities over short times but they do not withstand discharges of more than 20%
in fact they are always recharged by the alternator.
Moreover, the power of the alternator does not go entirely into the charge of the battery but is a function of the power of the consumer elements, the battery being a buffer.

the traction type batteries can be discharged from 80%, with high intensity but not as much as starting. on the other hand, these intensities may extend over the entire discharge.
count a continuous discharge of 1C maxi (100A for an 100Ah)

finally the capacitance indicated on the batteries is often for a value of C / 20 ie by unloading it with only 5A for a battery 100Ah
the Peukert effect causes the capacity to drop as the discharge intensity increases.
so our 100Ah C20 battery will actually have 100Ah only under 5A during 20h
but unloaded under 20A it will surely have only 60 or 70 Ah of capacity.

PS: the intensities of which you speak (* 5) are the short-circuit intensities maintained only 10s
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by Christophe » 06/04/09, 17:19

Ah thank you for the figures dirk in my case a starter battery would be perfect because the wheel would charge the battery permanently and as I do not intend to connect large power above it should go. I will make sure not to exceed 20% discharge in the dimensioning so!

When you talk about traction batteries, I think it's the same "inside" technology as cyclic batteries (solar)

They are more expensive to stored than storage batteries.
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by dirk pitt » 06/04/09, 17:59

Christophe wrote:When you talk about traction batteries, I think it's the same "inside" technology as cyclic (solar) batteries of this type:.


Yes, the same, although traction batteries accept currents a little stronger than servitude batteries.
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by Christophe » 06/04/09, 21:33

Ok and so you talk about thin plates for starter batteries: what changes in traction batteries?

I found this picture: http://www.yuasa.fr/batterie_np_spec.htm

It indicates the maximum current on 1 mn (A) and on 1 sec (A). It's a coef. from 1 to 3 between 2 approximately (except for large batteries)

We also have an indication on the life span in .pdf, for example: http://www.yuasa.fr/pdf/NPL100-12.pdf
Lifetime (at 20 ° C)

Floating application (= buffer): 10 years / years

Cyclic application:

100% discharge depth: 100 cycles
50% discharge depth: 400 cycles
30% discharge depth: 700 cycles


Yuasa seem to have really good batteries ... to see their price, given the performance, I think they will be salty ... very ...
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by elephant » 06/04/09, 22:20

But, indeed, they are very very good (a quarter of a century in the alarm: a real misery, they are replaced much less than the others: they are replaced after 6 or 7 years - use buffer - by acquit of conscience). How do you want to make a living? They are twice as expensive as Chinese batteries that last 2 years, so it's all good, you do not earn your life in emergency travel!

There is even better: Sonnenschein!
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