[RE-wrenches] Lithium Ion Phosphate for grid back up

[John DeBoever]

Darryl,

Lead acid battery typically recommended bulk charge is 10-15% of C20 for the flooded lead acid and 20 -25% of C20 for the sealed valve regulated lead acid.  Depending the application and the environment, these rates could be optimized, on a case by case basis. As the battery voltage raise to the absorption voltage (regulation voltage), the current automatically tappers due to the PWM or MPPT regulation.
Off-grid standalone PV systems optimum designs feature 5-days autonomy at 80% DOD at the worst month-average low temperature. Off-grid PV-genset hybrids optimum designs typically feature 2 to 3 days autonomy at 80% DOD same conditions.  The purpose of the large battery bank is to take the best advantage of the solar energy when it is available to store Ah in the battery for a desired power supply system power availability level. So the maximum current available from the PV array, after powering the load, is not wasted and sent into the battery during bulk charge and then tapered in as the voltage raise.

Lithium-ion batteries charge mode have certain benefits in some well-defined applications requiring fast charge with the requirement of a BMS.

John

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Darryl Thayer
Sent: Wednesday, August 24, 2011 10:44 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Lithium Ion Phosphate for grid back up

One of the advantages of LiFeP is the fast rechange rate.  I have found that fast recharge is very hard on LA batteries, if they are recharged faster they fail sooner.  Perhaps Jamie or others could answer is there something that can be recharged fast?  Capasitors are almost impossible to work with.  Lead carbon? Ni Magnisum Cobalt?
From: Jeff Oldham <starpower4u at juno.com>
To: re-wrenches at lists.re-wrenches.org
Sent: Tuesday, August 23, 2011 5:31 PM
Subject: Re: [RE-wrenches] Lithium Ion Phosphate for grid back up
I 2nd what Ray Waters is saying. Much too soon, BMS will be an insane challenge, we rarely care about weight and footprint like the EV's do. Returning defective cells to China IF they accept responsibility for the failure - I don't think so!! Sex appeal is overwhelming good judgement, one of the curses of our industry.


>From the Solar, Wind and Hydro powered office of Jeff Oldham/Regenerative SOLutions


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