Re: [EVDL] Phd in Materials Science on LiFePO4 batteries video WAS: Lithium 60ah 144v
With my order of SE/CALB cells I also received a PDF with a listing of all
the cells in the entire shipment. Looking through that I can see there were
enough cells that could have been grouped within 2 ahs of each other. My
100ah cells came in between 110-114 but could have been selected to be
between 110-111, 111-112, or 112-113 as that's where the majority of cells
were. I can see paying a bit extra to remove the few 114ah outliers which
they could still sell in a small grouped pack. They could even get a higher
price for those by selling them as 105 or 110ah cells. Throwing resistance
into the mix would make things more difficult but I think getting similar
capacity would go a long way to making management much easier.
If they grouped the cells at the factory from the entire production run they
could probably get them even closer.
With my order of SE/CALB cells I also received a PDF with a listing of all
the cells in the entire shipment. Looking through that I can see there were
enough cells that could have been grouped within 2 ahs of each other. My
100ah cells came in between 110-114 but could have been selected to be
between 110-111, 111-112, or 112-113 as that's where the majority of cells
were. I can see paying a bit extra to remove the few 114ah outliers which
they could still sell in a small grouped pack. They could even get a higher
price for those by selling them as 105 or 110ah cells. Throwing resistance
into the mix would make things more difficult but I think getting similar
capacity would go a long way to making management much easier.
If they grouped the cells at the factory from the entire production run they
could probably get them even closer.
EVDL Administrator wrote:
>
> On 14 Dec 2010 at 20:42, AMPhibian wrote:
>
>> I just think we'll get more bang for the buck by pushing for more closely
>> matched cells, even if we have to pay extra, than paying for a monitoring
>> system which doesn't actually fix the problem of mismatched cells.
>
> That was part of Solectria's secret for getting 4-6 years of life out of
> gel
> batteries in the Force. They used batteries with very tight manufacturing
> tolerances, instead of using equalizers or a BMS.
>
> They did fit some cars with a BMS, but I think it was mostly when they
> were
> using Hawkers prior to adopting the East Penn / Sonnenschein gel
> batteries.
>
> But then look at Lee Hart's experience. He got something like 10 years
> out
> of a pack of AGMs with his balancer.
>
> I also think you're going to have trouble finding highly consistent
> lithium
> cells, unless you're willing to play MUCH more - as in several times more
> -
> than the Chinese lithiums go for. But I could be wrong.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
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