[EVDL List]

On Tue Jun 26 13:13:04 PDT 2012 marke.xxx@xxx.xxx said:
>That's what I have in my hand a A123 12V7 implying that it's 7.2ah like the lead battery that it replaces but it's actually 4.6ah. Both of mine arrived DOA 0V so I'll get a replacement. I bought them in a Phoenix Contact metal enclosure for a UPS I'm working on for work (from Mouser). They said I'd void the 1 year warranty (claim 15 year in ad) if I pry it apart to check out the balancing curcuitry but I'm curious. Nice package though but $790 for 2 in the enclosure (24V supply) #2320351 vs $220 for the lead version pair #2320319. I still don't understand why the LiFePO4 is only 4.6ah compared to the 7.2ah for lead, not sure what the advantage is except weight, certainly not price.

Advantage is total cost over expected life. (and having the UPS actually be able to work when it's needed.)


--

Bobcats and Cougars, oh my! http://john.casadelgato.com/Pets
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[EVDL List]

The reason for the lower Ah spec of the Li-Ion battery
is because it can *deliver* at least as many Ah as the
Lead-acid that is only delivering the 7+Ah when discharged
in 10 to 20 hours, while a UPS will discharge that battery
under half an hour, so you are lucky if it manages to suck
4Ah out at that rate.
See the bottom of the following page for an example of the
available power and Ah at different discharge rates:
http://www.csb-battery.com/english/01_product/02_detail.php?fid=5&pid=11

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: xxx@xxx.xxx Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203

-----Original Message-----
From: xxx@xxx.xxx.edu [mailto:xxx@xxx.xxx.edu] On
Behalf Of xxx@xxx.xxx
Sent: Tuesday, June 26, 2012 1:25 PM
To: Electric Vehicle Discussion List
Subject: [EVDL] A123 ALM 12V7 drop in LiFePO4 battery

On Tue Jun 26 13:13:04 PDT 2012 marke.xxx@xxx.xxx said:
>That's what I have in my hand a A123 12V7 implying that it's 7.2ah like
the lead battery that it replaces but it's actually 4.6ah. Both of mine
arrived DOA 0V so I'll get a replacement. I bought them in a Phoenix
Contact metal enclosure for a UPS I'm working on for work (from Mouser).
They said I'd void the 1 year warranty (claim 15 year in ad) if I pry it
apart to check out the balancing curcuitry but I'm curious. Nice
package though but $790 for 2 in the enclosure (24V supply) #2320351 vs
$220 for the lead version pair #2320319. I still don't understand why
the LiFePO4 is only 4.6ah compared to the 7.2ah for lead, not sure what
the advantage is except weight, certainly not price.

Advantage is total cost over expected life. (and having the UPS
actually be able to work when it's needed.)


--

Bobcats and Cougars, oh my! http://john.casadelgato.com/Pets
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[EVDL List]

Put the zero volt battery on charge. It will very likely be just fine.

The BMS disconnects the output when the cells drop below a some
selected voltage. Thus, seemingly zero volts output. Also, the cells
themselves are completely unharmed by running them to zero volts.
Thus, put the battery on charge and it will likely be just fine.

Here is what I wrote about these batteries just a few weeks ago on this list:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>

There are a few important advantages of LiFePO4 over lead-acid:

1) The A123 12V7 will pretty much last forever in your UPS or
emergency light or alarm system. (20 years at least.) The lead-acid
will need to be replaced every 3-4 years, give or take.
2) You get 13 volts during the entire discharge, even at full load.
3) Under a 30 amp load, the A123 12V7 will deliver the entire 4.6
A-hrs holding 13 volts. The lead-acid will deliver, at most, 2.4
A-hrs at _half_ that load, and will sag down below 11 volts doing so.

Here are the discharge curves for the typical 7.2 A-hr lead-acid "brick":
http://www.gsbattery.com/ind-products/pe12v72/pe12v72.html

If you have a typical UPS on your computer, it has one of
these 7.2 a-hr lead-acid bricks in it. Your PC and monitor likely
draws 150 watts. About 1.3 amps @ 115VAC. To provide the required
150 watts, the 13 volt A123 12V7 will need to supply 11.5 amps and
will do so for 24 minutes. The 12 volt lead-acid will need to supply
12.5 amps and will run for maybe 12 minutes, about half as long as
the A123 12V7.

The UPS will run twice as long, weigh half as much, and I
doubt you will ever have to replace the battery.

There is a lot of air inside the case of the 12V7 because
they wanted a direct drop-in for the 7.2 a-hr brick. Not _quite_
enough room, however, for another row of 26650's to give 6.9 A-hrs.

Bill D.


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