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Monday, November 1, 2010

Comparison of VRLA vs Lithium Batteries

Dear sir ,
Chanced to browse your website and must say intrigued by the efforts this organisation is making in finding solutions to some of the vexing problems ,
Recently happened to read some of the work done by " Green Mobile Services " a London based organization who in association with "International Funding corporation" has done some good studies , Particularly Uganda in association with MTN, Haiti In association with Digi cell etc In all these cases it appears that reduction of Diesel consumption for powering telecom towers to power te BTS has been attempted
In all these cases the batteries used for back up power has been the VRLA ( valve regulated lead acid Batteries)
VRLA batteries have inherent disadvantages/ limitation
require reconditioning of the battery room thus consuming power for air conditioning provided by the DG set ( batteries do not power theA/c)
requires regular Maintenance adding to the man power requirement
capacity decreases as the room temperature goes up
Foot prints are higher
suffers from sudden death ( a common and inherent problem with lead acid batteries)
Ampere hour efficiency is low and watt hour efficiency is rather lower and so on
In the recent Months these have been astounding developments in regard to the " Lithium " Batteries , more so after the "OBAMA" President of USA advanced Huge grants for the development of batteries for "Electric Vehicle". Safety issues which were once a concern have been dealt with and t o day it is not such a serious issue .
The attachment details the several advantages of Lithium over the conventional VRLA batteries , and would consider it a privilege to receive your views and feedback
Thanking you with best regards
G.Raghavan
Bangalore
Mob 91-0-9980512439




VRLA battery (valve-regulated lead-acid battery) vs Lithium




Sl no
Attributes
VRLA
Lithium
Remarks
1
Electrode Chemistry
Acid
Alkaline

2
Individual cell voltage
2.00
3.7o
Higher cell voltage
3
No of cells required for 48 v system
24 cells
13 cells
Lower no of cells
4
Current cell capacity
Generally 600 ah
Much lower
To be decided/sized
5
Approx Dimensions of cells LxWxHt
300x175x350mm
Tol +/-2mm
Much lower less than 60 % of VRLA
Lower size
6
Approx weight of cell in Kgs
~40 Kgs
Significantly lower say 55%
Less weight better for support structures
7
Approx  foot prints of 48 v system LxWxHt
1300x375x1300
Significantly lower
Saving of space
8
Wt of battery bank
~1050 Kgs
<500 Kgs
Lower weight
9
Float voltage/cell
2.25
4.2v

10
Charging current
~12-15% of rated ah ,72-90Amps
1 C is Fine no harm preferred is 0.3C
Lower charging time
11
Time taken to fully charge
10-12 Hrs
2-3 Hrs only
Saving in time
12
AH efficiency
~90 %
Better than 98%
Saving in power loss , reduction in opex
13
Watt hr efficiency
~70%
>93%
Power saving
14
Operating Temperature
Prefer 22-28deg C
Safe up to 55degC
No A/C required saving in cooling power requirement
15
Maintenance
Required
Not required
Saving in Man hours
16
Individual cell protection
Does not exist
Individually cell protection provided
Safe and reliable
17
Over charge issues
Detrimental
 cut off provided
Safe
18
No of cycles @80%DOD
~1200cycles
>3000 cycles
Longer life
19

No of cycles @50%DOD
~1600
>5000cycles
As above
20
Hydrogen liberation during operation
Yes liberated
None
Safer
21
Sudden deaths
Possible
None
Reliability enhanced
22
Self Discharge
High
Very low
Hardly any longer storage period
23
Sulphation issues
Applicable
 None

24
Capex
Low
Higher
Initially
25
Opex
High
Very low
Savings
26
Cost per cycle
High
 Very low
Lower total cost
27
Operation efficiency of SMPS rectifiers
Low since they operate at lower levels
High since they can operate/charge at higher currents
Savings in Opex estimated at 14 % 
28
Savings On A/c of no Air conditioners
None
Huge
Lower rated power requirements
29
Derating of cell capacity due to orientation
Yes applicable between vertical and horizontal positioning
None

30
Life expectancy
3-4 years Max
10 years minimum
Huge savings

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