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Open Roads Forum  >  Tech Issues

 > Quantifying the Peukert effect: extra camping days?

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MEXICOWANDERER

las peƱas, michoacan, mexico

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Posted: 04/14/12 04:22pm Link  |  Print  |  Notify Moderator

Another extrapolation is to imagine a battery somewhere near the 3/4 charged mark. It may accept 15 amps. A pair would accept 30 amps. I have to try and keep this simple. Imagine 10 batteries each accepting 15 amps; Get the idea?

bka0721

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Posted: 04/14/12 08:18pm Link  |  Print  |  Notify Moderator

You will also have an impact if the batteries have different age and number of cycles. That is why you would be better off buying both batteries at the same time.

If things are working for you now, don't worry about swapping out the batteries until these expire. With the way you are using them, that will be sooner than later. When you get the new batteries, pay more attention to their SOC and % Discharge, or if you don't worry about money and don't mind replacing the batteries more freqently, keep doing what you are doing. With charging and discharging more batteries, you won't have to take your battery % down as far and your charge time will be shorter too.

b


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Posted: 04/14/12 10:16pm Link  |  Print  |  Notify Moderator

From Smartgauge

115AH batteries.
Peukert = 1.3.
Use from full to 50%.

One battery:
1A, 97.2 HRS
5.75A, 10 HRS
10A, 4.9 HRS
100A, .25 HRS

One battery then switch to the other battery:
1A, 194.4 HRS
5.75A, 20 HRS
10A, 9.8 HRS
100A, .5 HRS

2 batteries parallel:
1A, 239.3 HRS
5.75A, 24.6 HRS
10A, 12 HRS
100A, .6 HRS


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pianotuna

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Posted: 04/14/12 11:04pm Link  |  Print  |  Notify Moderator

Hi,

It is always better to use two batteries in parallel than to use each individually. The longer time between cycles means greater over all life span. That's more dollars to use for camping.

As others have pointed out, charging via a generator will also be faster with two batteries in parallel.

Or, you could--go solar!


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Posted: 04/15/12 09:38am Link  |  Print  |  Notify Moderator

pianotuna wrote:

Hi,

It is always better to use two batteries in parallel than to use each individually. The longer time between cycles means greater over all life span. That's more dollars to use for camping.

As others have pointed out, charging via a generator will also be faster with two batteries in parallel.

Or, you could--go solar!


Please give an example of how charging time is less when doing both together than by doing one and then the other, specifying SOCs at start and at the end of the recharge and the charging rates involved.

Obviously if you have two chargers you can do them separately at the same time given enough gen watts to run both chargers, but that is not the question.


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pianotuna

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Posted: 04/15/12 09:51am Link  |  Print  |  Notify Moderator

Hi BFL13,

Your own research into charging amps. Acceptance rates after 85% state of charge would be twice as great with batteries in parallel being charged at the same time. And at 50% the parallel batteries will take as many amps as the charger can push without overloading the generator. If there are only two batteries and the converter is large enough charging times might well be nearly the same. That, of course, is IMPORTANT if one is paying to run a generator. If there is adequate solar, it doesn't matter from a cost point of view.

BFL13

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Posted: 04/15/12 10:21am Link  |  Print  |  Notify Moderator

The acceptance rate would double but so would the required AH to restore. Where is the time saving coming from?

Time x to do a 50-90 on a 110 at 20amps twice = 2x
Time y to do a 50-90 on a 220 at 40amps once = y

How is y less than 2x?

MrWizard

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Posted: 04/15/12 10:31am Link  |  Print  |  Notify Moderator

its time Not volume
one battery for 2 hrs then a second battery for 2 hours is TWO separate charge cycles totaling 4 hrs
however charging 2 batteries at the same time using twice the charge acceptance rate means One charge cycle of two hrs

yes the generator has to produce more power and the charger/converter has to produce the charge, but the physical run time of the generator is reduced

its the reason we all want the biggest baddest smartest charger we can afford

* This post was edited 04/15/12 10:38am by MrWizard *


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BFL13

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Posted: 04/15/12 10:44am Link  |  Print  |  Notify Moderator

In my example of doing one twice at 20 amps or doing both at 40 amps, the charging rate is the same.

If you double the charging rate to 80 amps and do both with that instead of 40 amps you don't halve the time.

A 50-90 takes 180 min on 220 with a 35 amp Vector and it takes 130 min with two 35s doing 70. It is not linear as we know.

The 50 min (edited from 40) saved by doubling the amps is 50/180 =28% time saved not 50%.

I still am having trouble seeing where you can shorten the time without seeing the whole scenario. Maybe I need more coffee.

* This post was edited 04/15/12 10:58am by BFL13 *

Salvo

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Posted: 04/15/12 10:55am Link  |  Print  |  Notify Moderator

Pumping 40A into one battery will knock it out of bulk at perhaps 70 to 75% SOC. Two batteries will remain in bulk perhaps to 80 to 85% SOC. Absorption charging (tapered current) is slower than bulk charging (constant current).

BFL13 wrote:


How is y less than 2x?


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