Ginormous battery rack [RE-wrenches]

[Ezra Auerbach, DragonSun Consulting]

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Hi all,

Sorry for any confusion I may have caused. I do mean apply the  
Capacity divided by five (C/5) charge rate. Which  in these batteries  
(2KS33PS) equals 445 amps. The term "capacity" may cause confusion in  
this dicsussion. Here's why: we normally talk about battery capacity  
at the 72 hour rate (2225 amp hours for this model). This is  
appropriate for the usual rate of residential discharge and we are  
usually looking at storage capacity. However when looking at  
recharging the same battery the appropriate rate to refer to is the  
20 hour rate. This is because the batteries will be charging faster  
than they were discharged hence more heat will be generated which in  
this case will actually hasten the charging process. The good news,  
is that the 20 hour rating for these batteries is 1766 amp hours  
hence we "only" need an initial charge rate of 353 amps.

That's the problem with ginormous batteries, it takes a lot of  
current to properly recharge them. Most battery manufacturers who  
I've spoken to would like to see the C/5 rate and are thankful if the  
C/10 is a reality. Again for these batteries even the C/10 rate would  
be a charging system capable of 176 amps at 48 Vdc. Not an un- 
achievable charging system with an 8.5 kW array or a couple of large  
wind gennies, a few inverter/chargers or a combination of all. Much  
less than this much charging "umph" will eventually result in  
shortened battery life.

Hope this clarifies.

Ezra


On 2-Oct-06, at 8:19 AM, Allan Sindelar wrote:

>
> Ezra,
> Minor correction here with large consequences to the question at  
> hand...a
> C/5 rate is "capacity at a five-hour rate", or 20% of the battery's  
> amp-hour
> rating, rather than 5%.
> Allan at Pos Energy
>
> ----- Original Message -----
> From: "Ezra Auerbach, DragonSun Consulting" <ezra at lasqueti.net>
>>
>> I totally agree with Drake, your next challenge will be charging
>> those batteries. You need an on-site ability to apply C5 (5% of the
>> battery banks amp hour rating at the 20 hour rate).
>
>
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