Initial battery charge for ThunderSky cells

Is an initial charge in parallel necessary?
Or will, a initial charge with a BMS attached also properly balance the cells?

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Always equalize the pack before you install. This ensures that the batteries are all at the same voltage before you install. If you install and then let the balancers work, it'l take quite a few charges to get all of the batteries completely balanced. Yes it'l work, but it'l take a long time to become balanced. If you start balanced, the BMS won't have to work as hard, if at all, to keep the batteries in balance.

If I have to do an initial charge, can I use the PFC30, or will I need another charger? If I need another charger, any recommendations? What wiring to people use for this initial charge? (i.e.: 10 or 12 gauge common automotive wire?)

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no you cannot use the manzanita charger. If you parallel all batteries, the voltage will go between 3 and 4V or so. The PFC 30 goes 12 to 450VDC output. You will need a single cell charger. This can be a very low current charger. Batteryspace.com has several:
http://www.batteryspace.com/smartchargerforlifepo4batterypacks.aspx

This one is on sale for $20:
http://www.batteryspace.com/Smart-C...1-Cell-LiFePO4-Rechargeable-Battery-Pack.aspx

Just parallel all batteries together (or in groups) and plug this in to charge. Might want to let them sit. Then after the charger is done, let the batteries sit for a night or two to let the charges equalize.

Any pointers to external documentation or websites are greatly appreciated. Thanks!

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www.manzanitamicro.com
www.elithion.com

Those chargers are 3.2v chargers with 3.0v nominal; if I understand right, that isn't correct for Thundersky batteries, which are 3.2v nominal, and 3.8max (recommended). They also have a range up to 163ah; I have the 200ah cells. Will that be a problem?

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read the description of the charger:

Cut-Off voltage = 3.65 +/- 0.05V

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Nominal doesn't really matter, its the charge current and the cutoff voltage. The cutoff voltage can be lower than the max voltage of the TS cell, as long as its above the nominal voltage of the cell (in this case, TS is 3.2Cut-Off voltage = 3.65 +/- 0.05V), it will charge. The charger tries to PULL the voltage up to 3.65V, but no more.

You just want every one of the cells to be at the same exact voltage. Leave a parallel bank on the group until its charged, take it off, put another group on and charge them. Before you install, make sure all of the groups are at the same voltage. Then take out of parallel and install in your desired pack configuration.

The charger will be fine for equalizing cells, but I wouldn't try to use one of these to charge a cell from completely dead to a full charge. A single cell charger, IMHO, is required for lithium builds. It should be in every toolbox. If the BMS fails, or one becomes too out of balance for some reason, you'll need this to help bring it back up.


[/quote]
Thanks -- I obviously have seen those sites; I'm curious about some specific pages or documentation that recommends where and how to do an initial charge.

corbin[/quote]

Although it has been discussed on a few other threads, you can just use this thread. I'll help you figure out what you need to know, just ask. If I don't know it, I'll know where to find the information. I work as a consultant for both ManzanitaMicro and Elithion and previously with EVComponents.

corbin said:

Thanks -- I obviously have seen those sites; I'm curious about some specific pages or documentation that recommends where and how to do an initial charge.

corbin

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The implication in the above quote is that you would like some evidence to any assertions made herein. A reasonable, and prudent, demand when dealing with internet advice. This 75 minute long video will tell you all you need to know about the care and feeding of LFP packs for EVs and if you truly value your expensive investment then you will watch every minute of it and take good notes along the way:

http://www.ri.cmu.edu/video_view.html?video_id=60&menu_id=387

Connecting all of your cells in parallel first then charging to a specific voltage somewhere along the knee of the upper end of the charge curve is top balancing. That's fine as long as you understand that it shifts discrepancies in cell capacity to the end of the charge curve. Conversely, discharging all of those cells to a voltage somewhere along the knee of the lower end of the charge curve results in bottom balancing the pack, and you will then need to use a BMS with a cell-level high voltage cutoff to terminate charging as soon as the first cell just enters the upper knee of the charge curve (say, 3.50-3.55V). Even better would be to terminate charging when a specific number of Ah have been returned to the pack (ie - the charger has a Coloumb counter).

I'm in the same boat as Corbin. In fact we have virtualy exactly the same hardware. I have a PFC 30/ elithion / sky energy 180 ahr. EVcomponents speacial (when they were actualy delivering).

After watching the video above I think have decided to parallel my batteries first and charge to ~ 3.5V / cell then series them and let the manzanita/elithion top off the cells to 3.8V (closely monitored) I want to do this to test the HVC of the system. 3.5V should get me high enough on the knee of the curve so all the batteries are at roughly the same SOC so when the manzanita starts to top it off balancing with the Elithion with be faster/easier. The elithion only has a shunting capasity of 200mA if I remember right, which just isn't enough for an initial balancing if the batteries are far out of balance.

I just bought an old surplus HP DC power supply that I plan on using for this (HP 6286A)
0-10V @ 10 amps has both CC and CV modes which is nice.

I don’t know if I would recommend the charger Frodus recommended (though it will certainly do the job) simply because the out amperage is really low.

If you do a little math. Time to charge the battery (in hours) will be given by the (Estimated SOC* Ahr rating)/amperage of the charger.

So for your case if you assume a 50% SOC, using the charger recommended 0.5(200 ahr)/.7a = 143 hours for one battery. If you have all 48 of your batteries in parallel it will take you 143 hrs (48) = 6864 hrs to charge your pack, which is like 9 ½ months sooo….. that’s a long time.

There is a 6 A charger on the site I would recommend getting that one if you are going to get any of them. You can buy 3 of those for what I paid for my power supply after you figure in the cost of S and H plus they have automatic cut off which is nice and they are a plug in and go which is also nice.

I chose my HP because I have been wanting a low voltage adjustable power supply that was capable of highish amps for a while for other projects that I tinker with from time to time so this was a good excuse to buy one.

If you find your batteries are really low you can always charge them at high current with your Manzanita then top them off with the single cell charger, that will significantly reduce the balancing time, but you run the risk of overcharging a cell or cells if you neglect the process.

I hope this helps

frodus said:

really?

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frodus said:

Last time I checked, 12Gauge can carry 25A. 18 can do over 10A, and 24 can do 2-3A.

http://en.wikipedia.org/wiki/American_wire_gauge
http://wiki.xtronics.com/index.php/Wire-Gauge_Ampacity

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this is the website I refered to http://www.powerstream.com/Wire_Size.htm
I quoted the power transmission limits as they are the most conservative. Since this will be a continious load for a long period of time so I felt those numbers were the most appropriate to use. I maybe wrong as I am frequently.

The fact of the matter is that the current will be so low even with a 6A charger virtually anything he has laying around will work, even cat 5 cable (24ish guage).

frodus said:

I didn't recommend the 0.7A, I said get the 6A charger.

repeat

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frodus said:

I'd say get a small (0.7A) charger, but you never know when you can use the higher amperage one. It'l equalize quicker for ya.

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I’m sorry I must have misunderstood the later comment as recommending the 0.7A charger

frodus said:

And you need to realize, this is an equalization charge, not a charge from EMPTY to FULL. It won't take but a night to equalize.

repeat

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this is not the behavior that is reported by dtbaker in this thread.

http://www.diyelectriccar.com/forums/showthread.php/normal-initial-charge-li-52341.html

I don’t know what SOC the batteries ship out with nor do I know how long the batteries were sitting since they were charged last. My batteries have been sitting for nearly a year an and half at this point so I anticipate significant balancing time.

even if the batteries are at 90% SOC the time to charge one cell with the 6A charger is (1-0.9)(200 ahr)/6A = 3 1/3 hrs , for all 48 in parallel it is 3 1/3 * 48 = 160 or so hours.... I'm thinking it will likely take at least a couple of days. But you are the consultant and I'm sure you have done this before so I would probably tust you more then me.

The fact of the matter is that the current will be so low even with a 6A charger virtually anything he has laying around will work, even cat 5 cable (24ish guage).

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Agreed.... although 6A is a little much for 24gauge , but anything larger than that will work great.

this is not the behavior that is reported by dtbaker in this thread.

http://www.diyelectriccar.com/forums/showthread.php/normal-initial-charge-li-52341.html

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just read that. That is a little surprising that they are shipped not fully charged. Sorry I assumed.

I don’t know what SOC the batteries ship out with nor do I know how long the batteries were sitting since they were charged last. My batteries have been sitting for nearly a year an and half at this point so I anticipate significant balancing time.

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Yeah, if they've been sitting, they probably self discharged a little bit. It'l take a while to equalize.

even if the batteries are at 90% SOC the time to charge one cell with the 6A charger is (1-0.9)(200 ahr)/6A = 3 1/3 hrs , for all 48 in parallel it is 3 1/3 * 48 = 160 or so hours.... I'm thinking it will likely take at least a couple of days. But you are the consultant and I'm sure you have done this before so I would probably tust you more then me.

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Yeah, it'l take a little while, but if he wants it to equalize quickly, it'l cost a bit. Large single cell chargers are not easy to find nor are they cheap. You could use a large power supply, but for $20, a 6A doesn't sound that bad. Thats what, a week? Maybe get two or three and do multiple banks.

The long and the short of it is that you want to get your batteries to the same resting voltage.