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View Full Version : How to Charge Thundersky LIFEPO4 batteries, manually, with a battery supply



NonPolluter
24 September 2010, 0901
Here's how to do it:

1. Go to Jack Rickard's blogs and look up the State of Charge table for Thundersky.
2. Use a multimeter and multiply the number of cells with Rickard's chart.
3. Use a power supply. Set it for 3.8 volts per cell. Multiply by the number of cells.
4. Calculate the amp hours you need. Jack says that the charging efficiency of LIFEPO4 is nearly 100 percent.
5. Use a digital on/off AC shut-off timer, set for the number of Ah you need, in hours.

I've do it, and it works.

Jack says, I think, if you want to get more charges out of the Lithium battery pack, you must stay within the 40 to 90 percent State of Charge.

frodus
24 September 2010, 1233
3.8V a cell will overcharge Headway cells.

Its specific to each and every battery out there. SE cells actually like a little more than 3.8V. Headway shouldn't go over 3.7V.

Just because "jack says" doesn't mean he's right, but so many people seem follow him.


I won't. I believe BMS is importand, especially monitoring.

BaldBruce
24 September 2010, 1237
Jack says, I think, if you want to get more charges out of the Lithium battery pack, you must stay within the 40 to 90 percent State of Charge.

Take what Jack says with some grains of salt. His effort to collect data and share it with others is to be highly praised. His conclusions on that data are where alot of people disagree with him. (And if you can make it all the way through one of his shows without the fast forward button, you are a better man than I!!!!!!)

This last show is a perfect example. He claims that you can re-charge without protecting individual cells and that he has successfully acomplished this. All true statements. However take a look at his video result fom last Friday at the very end where he fesses up to almost burning down his garage because he forgot to unplug his charger circuit when he went out to dinner. Battery pack on test completely disintegrated from overcharging leaving just a slag pile. A BMS with a simple per cell HVC would have easily and inexpensively prevented this near tragedy. So, yes nearly everyone in the Li-ion community agrees you should keep the cells in the middle of their range and never bring them really low or all the way to the very top, the devil is in the details.........

teddillard
24 September 2010, 1243
well I for one think it's time to resurrect this little video from the old site:

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BaldBruce
24 September 2010, 1249
Ted, I even have to fast forward your version.... (shuddering)

ZoomSmith
24 September 2010, 1251
That 3.8 seems awfully high, particularly if you are only shooting for 90%.

When charging, my Headway's (40160S) seem to go up real fast at about 3.45V, so at that point I'm done.
My Battery Monitoring System (me+meter) is not sophisticated, but I'm learning a lot.

Skeezmour
24 September 2010, 1307
Zoom I know I really like those cells you picked up. Post up some performence data (wh/mi @ speed, ect) when you get a chance. your elgixxer sure looks light.

NonPolluter
29 September 2010, 1921
ADDENDUM
Here is the link to Jack's DOD / SOC chart:
http://jackrickard.blogspot.com/2009/12/ok-here-it-is-sag-voltage-more.html#comments


Our experience with 35AH Thundersky LFP batteries on a Native Z6 is different from Jack's. Where Jack has approx. 95% remaining, we would estimate at 30%, for example. Keep in mind that Jack's chart is based on a much larger pack (for a car) than the Z6 scooter's pack.

frodus
30 September 2010, 1417
Same batteries? same Capacity?

teddillard
30 September 2010, 1428
is ampacity a word?

frodus
30 September 2010, 1437
it is, I meant capacity though :)

ampacity is:
http://en.wikipedia.org/wiki/Ampacity

teddillard
30 September 2010, 1542
that's so awesome. it's my new favorite word, since i cant use ****ybollocks.

NonPolluter
09 October 2010, 1353
Here's how to do it:

1. Go to Jack Rickard's blogs and look up the State of Charge table for Thundersky.
.


Jack's Richard SOC (no load) LIFEPO4 chart does not apply to my 35AH 16-cell Thundersky battery pack (non-Yttrium, I think). Jack's battery pack was much bigger, though, but in theory, that should not matter.

What is interesting (in our observation) is that the LIFEPO4 battery acts like a capicitor that loses its charge quickly.

It is a more difficult battery chemistry to charge -- in comparison, the lead-acid method of measuring voltage rise doesn't apply to this battery -- the manufacturer's website states that amperage drop is the correct measurement. Jack Rickard's web blogs also indicate that there is a temperature rise -- this can be used to obtain the SOC, too.

So, if you are buying a battery charger for LIFEPO4, buyer beware -- I don't know of any battery charger that uses "amperage drop" as the cut-off signal --- do you?

Using a temperature sensor -- question -- how do you attach a metal (shaft with a point) temperature probe to a Thundersy cell?

BaldBruce
09 October 2010, 1801
1) Stop your fixation on Jack. You are getting horribly confused.
2) Charging Li based batteries is very easy. CC/CV. Keep the constant current below the manufacturer's maximum. Keep the output voltage below the manufacturer's maximum.
3) The trick is to monitor each cell individually so that none of them exceed the maximum allowable voltage. (A BMS is ESSENTIAL for this job or charge them individually. Do not swallow hook, line and sinker the nonsense that Jack spews.)
4) If you insist on not using a BMS, then shoose a maximum charge voltage for your pack that does not come close to charging any individual cell over 100%.

By the way, do you often speak in the third person, represent a group of people or is english a second language? Just curious. (Batteries and capacitors do have some things in common, but their voltage curves sure are not one of them.)

NonPolluter
13 October 2010, 1136
1) (A BMS is ESSENTIAL for this job or charge them individually. Do not swallow hook, line and sinker the nonsense that Jack spews.)
)

Thanks for the info.

Not all BMS's are alike. And even if they have high-voltage cutoff and cell voltage balancing-shunting, based on experiences with lead acid battery balancers, the BMS is usually inadequate, or fail miserably with higher loads, or (partially) fail in less than six months (as in our case with the Modalis BMS on a Native Z6. The Modalis doesn't do the battery charger shutoff any more -- the Modalis BMS still balances the cells perfectly.)

I've also been part of a group that build a high-voltage equalizer for lead acid. Even with the top brains in electronics and EV's, we discovered that our custom BMS had a current draw while on standby that would eventually drain the battery flat in an unexpectedly short time.

There is also a lot of misinformation about BMS's -- at least in the lead acid electric vehicles. Our conclusions were that the BMS were unnecessary with lead acid EV's IF you configured the battery pack in particular ways, that unfortunately, I can't share in this forum.

BTW, I've already stated that our realworld experience with 40AH LIFEPO4 batteries differs greatly from the SOC curve that Jack Rickard blogged about.

frodus
13 October 2010, 1321
I don't know of any battery charger that uses "amperage drop" as the cut-off signal --- do you?

Quite a few do. First they do Constant Current. They charge the battery at constant current until they reach a previously assigned voltage level. Then it keeps that voltage constant until the current drops and they shut themselves off. They’re called smart chargers. Yes they do charge to a voltage, but then they KEEP that voltage until the current drops towards zero. They don’t detect voltage as the end of the charge cycle, they detect voltage in order to switch to constant voltage mode.

This is, in my opinion, the only way you should be charging your batteries, with a CC/CV charger.

BaldBruce
14 October 2010, 1848
I've also been part of a group that build a high-voltage equalizer for lead acid. Even with the top brains in electronics and EV's, we discovered that our custom BMS had a current draw while on standby that would eventually drain the battery flat in an unexpectedly short time.

"Top brains in electronics" and you didn't bother designing for low standby drain???????



There is also a lot of misinformation about BMS's -- at least in the lead acid electric vehicles. Our conclusions were that the BMS were unnecessary with lead acid EV's IF you configured the battery pack in particular ways, that unfortunately, I can't share in this forum.

Absolutely true that their is a lot of misinformation about BMS. Starting with the assumption that lead acid and Li based chemistries can be treated the same!

Skeezmour
14 October 2010, 1912
Our 8 cell BMS at manzanita micro has a standby current draw of 0.003 amps. or about 1AH in 2 weeks..
Gene
Manzanita Micro

Only2Jakes
14 October 2010, 1923
You don't even really need a BMS in lead acid battery packs. The difference doesn't make much difference at all and they are cheap to replace anyways.

BaldBruce
14 October 2010, 1933
You don't even really need a BMS in lead acid battery packs. The difference doesn't make much difference at all and they are cheap to replace anyways.

Right. GM agreed with you. I have 26 lead acid batteries in series with no balancing other than the float charging. Works fine. There is a BMS on each cell, but the only function it performs is monitoring for a severe under voltage situation. (1997 S-10 OEM EV that cuts the power available back if any cell drops under 10.5V)