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yathis

Charging Lithium Ion Batteries

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Posted · Original PosterOP

When bulk charging LiFePO4 without a BMS, does it matter which way the battery leads (pos, neg) are connected to the psu?

 

I have 3 Mean Well psu's rated for 15A and 24V, the voltage is adjustable, I can connect them in series to get a total of 90V 15A.

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Don't be this guy.


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Posted · Original PosterOP

LOL that is funny

 

I remember reading somewhere that rechargable/secondary batteries need to be force fed current in reverse for charging.

 

I have a rc charger, but it does 3A and takes hours to recharge. I did a quick bulk charge today on my Mean Well psu's and it seemed to go well. Only thing is I set the psu to the correct Vmax for the pack = 3.6V/cell, it charged to the full amount, confirmed with dmm reading, but when I took psu off batteries, the Vtotal was about a volt lower. I finished the last 1V with the rc charger and it took 10 or so minutes. The MW's were working hard, and were warm getting hot to the touch, upgraded wire guage to help it out.

 

My batteries are bagged to shit, I think the IR is very high or I have put the pack together wrong somehow. I got a few tricks up my sleave, planning on soldering up an extra Series string, should help out with the voltage drop on load. This is an expensive lesson - DO NOT BUY USED BATTERIES - LOL that is 2 stupid mistakes.

 

1st - Buying LiPo from Hobby King - Those need to be baby sat hardcore.

2nd - Buying used A123 M1A's - Safer then LiPo, HUGE discharge amperes, 2ish Ah capacity

 

 

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11 hours ago, yathis said:

I remember reading somewhere that rechargable/secondary batteries need to be force fed current in reverse for charging.

Thats how fires are made. To charege a battery you need push the power back in(think of it that way) so the plus of the psu pluggs into the plus of the battery.

 

11 hours ago, yathis said:

have 3 Mean Well psu's rated for 15A and 24V, the voltage is adjustable, I can connect them in series to get a total of 90V 15A.

You better know exactly what your doing if you want want a fire. That litte computer chip in those chargers are doing a lot.

 

 

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Posted · Original PosterOP
On 4/20/2017 at 10:42 AM, Electronics Wizardy said:

Thats how fires are made. To charege a battery you need push the power back in(think of it that way) so the plus of the psu pluggs into the plus of the battery.

 

You better know exactly what your doing if you want want a fire. That litte computer chip in those chargers are doing a lot.

 

 

Well yeah, the MW's were getting hot and the fans were blowing. My tiny guage wires (~18awg+)were hot as well, thats when I got bigger wires (~12awg-) but it was pumping in 15A on my dmm. These MW's are ground isolated, the dell psu's.... I have one that is gnd isolated and thats all you need, its gotta be the first one in the series string. Oh and I kept a keen eye on the total voltage, but the MW's rocked steady, better then some cheap china crap. My imax from Hobbyking is off a bit.

 

Im trying to figure out exactly what to do with bulk charging because as I said, I set the mw's to the Vmax and keep a keen eye on it, I have a temp laser gun I use for the batteries themselves. The mw's are cc/cv, so I think its cc on low battery, so pumping in 15A in total to the entire pack 7S5P. Then it goes to cv because I notice the voltage slowly climbing.

 

In CC its pumping in 15A to the 7S5P (and the voltage slowly increase over time to the packs Vmax which is what I set the mw's to) then is it 15A/7S=2.14A then divide that by 5P = ~0.43A per can

 

So its pumping in 0.43A into each can, and each can is 3.3V(nom), 3.6V(max) and 2.3Ah(new) but I think my used ones are like 1.9Ah with a high IR. I dont deplete cells below 2V which is recommended, but my pack is ending much higher due to LVC of the controller. Roughly 2.75-3.2V per can.

 

I wish I could lower the current on the Meanwells.

 

++++++++++++++++++++++++++

 

Stole some juice frrom 7-eleven store, Good little setup, misplaced a bullet connector and got some Kentucky Fried Fingers, 50V and 300A isnt cool, not at all. Lets just say the copper bullet melted. So I just soldered up some 6mm bullets with the 4mm bullets so I dont do it again.

 

Good news tho, figured something out, gunna do it tonight.

 

 

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Posted · Original PosterOP

I can attest to LiFePO4 being fucking safe

pop, pop, crackle pop, pop, and some bubbling

snipped all the serial connectors, then ripped off the parallel strips

There has got to be 2 more pops in there.

 

Lemme say this, MUCH MUCh MUch Much much better then LiPo.........much

 

Lemme just say its resting in the cool night air in some bear proof can in a neighborhood park, will dump it off at the firehall tomorrow.

 

 

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