I think if we started over fresh with our lead acid battery system
designs, we would find we should have the same Battery management system
requirements that you have mentioned. Those are all problems that
plague lead acid as well.
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 9/15/2014 8:08 PM, jarmo.venalai...@schneider-electric.com wrote:
Hi:
We've done some testing and operation of Lion battery banks in the 10
kWh range with our inverter chargers and so far the most important
findings are:
1. The battery pack must have its own battery management system to:
a. regulate the individual cell voltages during charge and discharge
b. balance the cell voltages during charge and discharge
c. adjust cell charging voltages due to temperature variations
d. not provide a continuous float voltage to the battery bank
d. provide a built in safety cutoff disconnect, which turns off the
current if for any reason either the charge or discharge current is
too high.
A series string of Lion cells, without the battery management system
functions above is very likely to result in damaged cells or worse.
The most likely mechanism which ultimately causes damage is
individual cell temperature or cell to cell voltage imbalance.
2. The inverter system must be designed so that the inverter never
draws so much current that the current limit circuit in the battery
bank is triggered.
3. It may be necessary to adjust the current limit circuit as they
typically respond within milli-seconds and may be triggered on simple
power up as the inverter cap bank charges up.
4. When working with Lion, the inverter/charger should be configured
so that it is a simple current limited voltage source when in charge
mode. The built in battery management system should take care of the
required charge cycle operation.
5. Whether the pack is LiFePO4, Lion polymer or other does not appear
to be as important as a having a reputable brand and more importantly
a well designed built in battery management system.
The short version is that lead acid cells are amazingly forgiving with
regards charging and discharging voltages, currents and temperatures.
Lion cells on the other hand are amazingly sensitive and going out of
bounds on any of these can and will cause irreparable damage.
Given the sensitivity, it doesn't make sense to take on responsibility
for Lion battery management.
Management of that sensitivity and responsibility is best left to the
battery bank manufacturer.
JARMO
_____________________________________________________________________________________
*
Jarmo Venalainen* | *Schneider Electric **| Solar Business* |
*CANADA* | *Training & Development Specialist - Senior* *
Phone:* +604-422-2528 | *Fax:* +604-420-1591 | *Mobile:* +604-505-0291 *
Email:* _jarmo.venalainen@schneider-electric.com_
<mailto:jarmo.venalai...@schneider-electric.com> |
*Site:*_www.SEsolar.com_ <http://www.sesolar.com/> | *Address:* 3700
Gilmore Way, Burnaby, BC V5G4M1
_
_<http://%20www.sesolar.com/>
*** Please consider the environment before printing this e-mail
From: "William Miller" <will...@millersolar.com>
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org>,
Date: 09/15/2014 04:27 PM
Subject: [RE-wrenches] LiFePo4
Sent by: "RE-wrenches" <re-wrenches-boun...@lists.re-wrenches.org>
------------------------------------------------------------------------
Wrenches:
Does anyone have any experience with Lithium Ferrous Phosphate cells?
What are your experiences? I am looking at an installation tomorrow
and would like some input.
Thanks in advance.
William Miller
Gradient Cap_mini
Lic 773985_
__millersolar.com_ <http://www.millersolar.com/>
805-438-5600
______________________________________________________________________
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