Discharging batteries

[jambouk]

Assume I have two identical brand new 12v batteries, each with 200 amp hour capacity.

One drives a 12v motor which pulls 60 amps and the motor is run for 5 minutes.

The other battery is connected to a smaller motor which pulls just 5 amps but is run for 60 minutes.

I'm assuming both batteries have discharged 5 amp-hours worth of their capacity (2.5%). 

Have both batteries really taken the same "hammering"? 

Thanks for any replies.

James

 

[Carbon Brush]

Not at all.

You are presumably talking about lead acid batteries.

The amp hour (Ah) rating is specified at a given discharge current, and temperature.

Often a 20 hour rate is specified. So your hypothetical 200Ah battery will run 10 amps for 20 hours to an agreed discharge level.
However, if you run at a higher current, there is less Ah available.
The actual loss of capacity varies with battery type. But think in term of 50% of 'on the tin capacity' if you discharge in 2 hours.

Put the battery in a cold place, and it doesn't do so well.

HTH, David.

[Seelive]

52 minutes ago, jambouk said:

... Have both batteries really taken the same "hammering"? 

 

If you believe my Ladybird book on batteries, definitely not - the higher discharge rate will likely hit the battery harder.

[Jonk]

Store in the cold, use in the warm for performance (but the warmer they are, the quicker they degrade).

The ideal working temperature for lead acid blocks is 20-25 Deg C. Cooler than this, they won't perform as well, warmer than this they will but degrade quicker.

A typical lead acid block will degrade by up to 20% over 10 years, when used correctly within design parameters.

12V x 60A? That's a 720 watt motor.

But no, to answer the question they will not perform like that.

[jambouk]

Thanks all.

So is there a way to estimate the percentage dischrage of both batteries in this scenario?

James

 

[Seelive]

1 hour ago, jambouk said:

Thanks all.

So is there a way to estimate the percentage dischrage of both batteries in this scenario?

James

 

That's when the data sheet for the battery is invaluable (which should be available for any branded battery).

[Jonk]

James, have a look at the battery university website -> https://batteryuniversity.com/

I find the information very good and quite often use it.

[Zermelo]

14 hours ago, Jonk said:

James, have a look at the battery university website -> https://batteryuniversity.com/

I find the information very good and quite often use it.

That's a great resource.

[kbrown]

It's also not a good idea to constantly let lead acid batteries to completely discharge as sulfation will happen and degrade the battery faster.

[jambouk]

Just found this plot which seems logical though no idea f it’s validity / authenticity:

https://electronics.stackexchange.com/questions/125220/lead-acid-max-discharge-rate