Instead of charging the lifepo4 batteries directly from the alternator, is it possible to insert a lifepo4 charger in between the alternator and battery.
-----Original Message----- >From: Cor van de Water <[email protected]> >Sent: Feb 14, 2013 11:33 PM >To: Electric Vehicle Discussion List <[email protected]>, Electric Vehicle >Discussion List <[email protected]> >Subject: Re: [EVDL] 12V LiFePO4 batteries > >Since the cells might not be perfectly balanced, >I would expect that when one cell dips to 2V, you can >expect the others still to be around 3V, so I guess that >it would be prudent to disconnect when the voltage dips >to 11V (3x3+2) > >BTW, I did not suggest to float-charge the cells at 3.45V >indefinitely, since no car is running 24/7. >Typically a car is used a short period, sometimes a few hours, >and then shut down, from which moment the battery is slowly >discharged until the car has been started again. > >I believe the highest current in a (ICE) car is starting cold. >That can run close to 1000A peak. Because AFAIK most alternators >are in the 100A region, but it is certainly good to check for >max charging current and adjust for it. >NOTE that the net charging current is the difference between >the alternator's generated current and the consumption of the car. > >Regards, > >Cor van de Water >Chief Scientist >Proxim Wireless Corporation http://www.proxim.com >Email: [email protected] 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: [email protected] on behalf of Jerry Yue >Sent: Fri 2/15/2013 11:56 AM >To: Electric Vehicle Discussion List >Subject: Re: [EVDL] 12V LiFePO4 batteries > >Generally, the low voltage is set as 2.0V/cell or 8.0V/pack for high power >LFP and 2.5V/cell or 10.0V/pack for energy type LFP. Since we're using the >lithium batteries for ourselves, so you can measure the voltages of the >cells periodically. I have only one suggestion that, you'd better measure >the charging current from your alternator and be sure that your lithium >battery is capable for taking that current. Generally, the peak charging >current ranges from 200A-500A. Ideally, choose a LFP battery with 1/3 or >1/4 of the original lead acid battery. Of course, if you like to consume >too much electricity when engine is off, you'd better use bigger LFP >battery. >Jerry >On Fri, Feb 15, 2013 at 2:12 PM, Bruce EVangel Parmenter < >[email protected]> wrote: > >> Thanks Jerry for your response. >> Now, there are Low Voltage Disconnect circuits that I could add that >> would break the circuit at a set voltage. But the disconnect voltage on >> most of them are likely set for use with PbSO4 batteries. >> >> -What voltage would be a good disconnect voltage set point for that 12V >> Li-ion drop in battery? What voltage would prevent draining the Li-ion >> battery too low causing damage? >> >> >> {brucedp.150m.com} >> >> >> - >> On Thu, Feb 14, 2013, at 09:38 PM, Jerry Yue wrote: >> > Sure, it will be ok to use the lithium battery on your car. I used a 12V >> > lithium battery without bms on a SUV in 2008. It lasted half an year >> > before >> > it failed due to two times of over-discharge (I forgot to close >> > headlamps). >> > >> > On Fri, Feb 15, 2013 at 1:32 PM, Bruce EVangel Parmenter < >> > [email protected]> wrote: >> > >> > > Ah Ha! That is what I saw in the back of the J.B. Straubel's Porsche >> > > conversion when I followed him using his pusher trailer to his home >> > > (many years ago). The pack just behind the front seats and had little >> > > light dimly lights between the cells. So, that was the BMS he used in >> > > his EV conversion design ... neat! >> > > >> > > ... >> > > OK, no one has posted about one of my queries as to if the prepackaged >> > > 12V Li-ion battery that would drop as a replacement to my dying 12V >> > > group-24 deep cycle. So, I will assume there is no problem trying one. >> > > >> > > >> > > {brucedp.150m.com} >> - >> >> -- >> http://www.fastmail.fm - Or how I learned to stop worrying and >> love email again >> >> _______________________________________________ >> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub >> http://lists.evdl.org/listinfo.cgi/ev-evdl.org >> For EV drag racing discussion, please use NEDRA ( >> http://groups.yahoo.com/group/NEDRA) >> >> >-------------- next part -------------- >An HTML attachment was scrubbed... >URL: ><http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130215/140fab23/attachment.htm> >_______________________________________________ >UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub >http://lists.evdl.org/listinfo.cgi/ev-evdl.org >For EV drag racing discussion, please use NEDRA >(http://groups.yahoo.com/group/NEDRA) > > >_______________________________________________ >UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub >http://lists.evdl.org/listinfo.cgi/ev-evdl.org >For EV drag racing discussion, please use NEDRA >(http://groups.yahoo.com/group/NEDRA) > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
