How to protect batteries and what would like to see in new EVO

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How to protect batteries and what would like to see in new EVO

Message par Swissete le Sam 9 Avr - 6:48

The main concern we may all have is the degradation of the batteries and how to prolong their life and after some investigation it looks like the normal number of cycles for Li-ion batts goes up to 300-500 (full discharge cycles) for its expected lifespan.

How to increase that lifespan?? (please chip in to correct me... not an expert!)
1) Not discharging batteries too deeply. Found this interesting as discharging only to 50% before recharging again just triples the life of the battery.
2) Not charging them to the maximum. Max voltage for the li-ion cell is 4.2v. If instead of charging to 4.2v we reach only 4.2v we will double again the lifespan of the battery while loosing only a 10% of capacity/range.
3) Discharging in full. Leaving a battery too low for long period of time and adding a bit of self-discharge may end up going below the 3.0v mark per cell hence destroying the battery
3) Not storing for long the battery fully charged. This is problematic as it looks to develop electrolyte oxidation that reduces its capacity on the long run.
4) Making the battery work at high temperature or even storing at high temperature. It gets degraded. Funny enough that 30ºC is treated already as high temp.
5) Charging the battery when it is too hot. We should never do this but there's no temp sensor for the batt... so impossible to have it checked.
6) Charging at high "C". It is better for the battery to charge at 10A than 16A, it will increase less its temp.

Cutting the long story short the main idea is trying to charge more frequently and avoid high temps... don't charge at direct sun during summer if possible. As well if possible when charging at home after using the scooter wait for an hour to let the battery cool down.

What BMW did well:
After doing some math what I have seen is that BMW already did it well... they don't let us charge to 4.2v??

At full charge the bike reaches 148v...
- 148v total voltage / 3 modules is: 49,3v per module.
- 49,3v per module / 12 cells throws: 4,11v per cell .....  they don't let the batterys reach the 4.2v at full charge hence almost dubling/trippling the life of our batteries Very Happy (at the cost of up to 10% in range)

A full discharge to 0% battery leaves us with 120v
- 120v total voltage / 3 modules is: 40v per module
- 40v per module / 12 cells throws: 3,33v per cell.... That's well above the minimum nominal voltage permitted of 3.2v and far from the low end of 3.0v when the battery may get destroyed if lowering even further.

On top of that there are many types of Li-Ion chemistry and the one BMW chose is on the best ones  (NMC (Lithium Nickel Manganese Cobalt Oxide2)) that tolerates hich abuse and has not much drop per high temps. If they would just put a temp sensor on the battery for us to know when and when not to charge... it would please some control freaks like me Suspect

Swissete

Messages : 6
Date d'inscription : 05/04/2016

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Re: How to protect batteries and what would like to see in new EVO

Message par pberinger le Sam 9 Avr - 7:20

Thank you for those figures always wanted to check all what you have mentioned.

pberinger

Messages : 240
Date d'inscription : 12/03/2015

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Re: How to protect batteries and what would like to see in new EVO

Message par rico69 le Lun 27 Juin - 17:32

Very interesting and comforting, thank you Swissete!
Science is on our side Cool
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rico69

Messages : 255
Date d'inscription : 18/07/2015
Localisation : C evolution 2014

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Re: How to protect batteries and what would like to see in new EVO

Message par suerte_loca le Lun 27 Juin - 18:48

It means that the actual kwh stored in the c's battery (8kwh) is not the actual "nameplate" capacity of the cells, but for better durability. Sweet.

suerte_loca

Messages : 87
Date d'inscription : 08/04/2016

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Re: How to protect batteries and what would like to see in new EVO

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