Estimating Battery Power Used

Tubamanandy

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Feb 12, 2014
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Is there any approximate way of working out what percentage or how much battery power has been used from the recharge time ?

eg. My 36V 10.4Ah Li-on battery took 4 hours to re-charge after my run to work and back today from full
 

JohnCade

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May 16, 2014
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You need to know the amps of the charger, then multiply that figure by the time taken to charge. That will give the Ah used. Multiply that by the battery voltage, say 36 typically and that's the whs used. You can then divide that by the miles ridden to find the wh/per mile figure if you want.
 
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Emo Rider

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Jan 10, 2014
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I have seen a few threads similar to this one. It leaves me wondering why there is a need to know how to calculate this type of info. It seems to me that once you have ridden your bike over a consitant distance, on the same route and with the same rider input you soon get a very good idea of what your machine is capable of. After over a year of commuting, I can tell you within a couple of hundred yards when my gauge will drop. I travel 30 miles in two days and on the charger it goes. Still I respect the OP's question and would ask why you would want to know this?
 

Tubamanandy

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Feb 12, 2014
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I thought the general understanding was you should charge the battery after each cycle (I do it after I'm back from work each day after a 14 mile round trip)
 

Emo Rider

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I thought the general understanding was you should charge the battery after each cycle (I do it after I'm back from work each day after a 14 mile round trip)
The life of a lithium battery is based on charge cycles, typically 700 to 1,000 or there abouts depending on the type. It is my understanding that everytime you chage you are using up one of these cycles. So to maximize the life of your battery, you should let it go down as much as you can. A 10ah battery should give you 30 to 35 miles of range before need to charge. Charging a 10ah battery every 14 miles would technically half your battery life in terms of years of usefulness. You should be able to comfortably get two trips to and from work on a charge.
 

JohnCade

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The life of a lithium battery is based on charge cycles, typically 700 to 1,000 or there abouts depending on the type. It is my understanding that everytime you chage you are using up one of these cycles. So to maximize the life of your battery, you should let it go down as much as you can. A 10ah battery should give you 30 to 35 miles of range before need to charge. Charging a 10ah battery every 14 miles would technically half your battery life in terms of years of usefulness. You should be able to comfortably get two trips to and from work on a charge.
The best way to make it last is to charge it every trip and not allow it to discharge too low too often. My understanding is that two charges from half charged to full is also a cycle.
 

danielrlee

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The life of a lithium battery is based on charge cycles, typically 700 to 1,000 or there abouts depending on the type. It is my understanding that everytime you chage you are using up one of these cycles. So to maximize the life of your battery, you should let it go down as much as you can. A 10ah battery should give you 30 to 35 miles of range before need to charge. Charging a 10ah battery every 14 miles would technically half your battery life in terms of years of usefulness. You should be able to comfortably get two trips to and from work on a charge.
This is just plain wrong. Lithium batteries of any chemistry will last longer the less they are taken to their voltage extremes (high/low voltage). This is why some individuals (myself included) do not charge to 100% and also ensure a rigorous low voltage cutoff during discharge. Actual voltages vary from chemistry to chemistry.

In layman's terms, the less deeply a lithium pack is discharged, the longer life it will see.
 

Tubamanandy

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Feb 12, 2014
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This is my understanding too - where is Dave when you need him ? The danger of not having him around means stuff like this goes unchallenged.
 

Emo Rider

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Jan 10, 2014
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This is my understanding too - where is Dave when you need him ? The danger of not having him around means stuff like this goes unchallenged.
Two members have different views on charging cycles but I am not saying they are wrong. I work selling a number of different brands and this is the training I have recieved. I have never had a battery manufacturer tell me what is the correct proceedure for maximizing battery life however.
 

mfj197

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Jul 18, 2014
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danielrlee is quite correct. The less stress on the battery (in terms of deep discharge) the better. Emo Rider is probably taking his understanding from Bosch batteries, where charge cycles are recorded by the battery for warranty reasons (although according to Martin at e-bikeshop part charge cycles are counted as part cycles, so you don't need to fully discharge even then). But yes, for the batteries themselves the less stress the better.

Michael