Lipo Battery Packs in Parallel Noob Question...

bakaneko

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#11
this charger i bought is a POS... It saids DC output of 44V 1.8A but when I stick a multimeter in there it reads between 40.4 - 42.6V. I've been trying to get the batteries to full charge 42V but been falling short at like 40.7-40.8V. I mean if the peak voltage on the charger is ~42.6V; can it even get the battery to 42V...

I'll try leaving the charger in for a few more hours. :mad:
 


bakaneko

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#12
Put a watt meter on the bike and my multimeter must be faulty or I didn't get good enough a contact with the probes but the watt meter reads close to 42V now and I am still trickle charging it to completely full so all the cells balance. So everything is good in the world :D
 

Frankenstein

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#14
I'd get a 52v charger, that will charge a 41v battery to 41v, or in your case 44v I guess.
Now that sounds like a bad idea, up next: how to charge your 18v nicad tool batteries with a state of the art 20v li-ion charger. Voltage and amperage work the same way, you can supply more than you need and never have any problems (except for minor burns and battery explosions.)
 
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#15
I'd get a 52v charger, that will charge a 41v battery to 41v, or in your case 44v I guess.
Absolutely don't do that! For a 10S pack, use a 42v charger for lithium batteries, they are cheap enough. You CANNOT EVER over charge lithium batteries, not even a little bit for a little while, you can blow them up easily that way. And by "blow up", I mean literally, as in big ball of fire that burns your house down. If you are on a 36v system, then you want a 10S pack, and that means 10 cells in series, that will have a 42v peak charge, and be discharged at about 30v. Don't over discharge them, either.
Pick one:
https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=42v+lithium+charger&_sacat=0

The way a lithium battery charger works, is it charges at it's maximum capacity until the voltage reaches 4.2v per cell. Then, it gradually reduces the charge in order to keep the voltage from ever going over 4.2v per cell, until the output reaches zero, meaning the batteries are fully charged, and hold 4.2v per cell without any charge being applied. You can't EVER go over 4.2 volts per cell, or BOOM. Therefore, charging that last little bit takes the most time.
 
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bakaneko

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#16
Yes, I think he means for his 48V system he will get a 52V charger and for my 36V system he will get a 44V charger. This is what I think he means. I never charge my bike even close to 4.2V.
 
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#17
If it were me, I think I'd hook the battery packs up to three 12 volt lights in series and put an ammeter in series with that also. Then I'd stick a video camera in front of it and walk away. Sometime after the light went out I'd check the video to see when the light went out. That would tell me I could draw X amps for T amount of time. In other words, it'd measure the actual aH at that particular current draw.

For even more info, I'd put a voltmeter in parallel with the load and make sure the camera could see it. Then by reviewing the video I could plot the voltage drop over time.
If you did that to lithium batteries, they would never recharge again, and would probably explode if you tried. That's IF you could get a lithium charger that would actually try it. Mine wouldn't. You can't discharge those below 2.8 to 3.0 volts per cell (depending on the type), or they don't come back.

I wish you guys would relate your packs in terms of cells in series. A "48v" pack should be 12S (12 in series, the other part is "P", for parallel, so if you had 6 cells with 2 in series, and two each, sxs, it would be 3S2P), which, @ 4.2v per cells comes to only 50.4V, I think 52v is too much. Most of the cheap chargers are dumb, and only have a peak voltage limit. It would be fine if you have some kind of protection circuit, which you should, but I don't. I have a 10S2P pack on a 36v system, and my cheapo charger just stops at 42v. It blinks on and off for a while near the end, but that's it. 50v would be fine for a 12S pack. Particularly if you are using cylindrical cells. My smart charger has a setting for those that only charge them to 4.1v per cell, although all the other chargers will make them 4.2. My smart charger also has a discharge function that will discharge them to the safe limit, and measures the actual aH, like you wanted to do the hard way.
BTW, that's a $25 r/c charger called a B6, which is a great machine, but it only charges up to 6S, which is why I have a dumb charger for my bike. The B6 will recondition nickel packs, too. It requires a substantial d/c power supply between 11 and 18v, it's meant to be connected to your car battery, at the r/c field. If you get into lithium batteries, a good smart charger is a wise investment. I made a report on lithium battery types I posted on another forum, but I'll copy it here, just FYI
 
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#18
Regular Lithium Ion: Remember, these have the highest storage capacity, but they are DANGEROUS, and should only
be used with a protection circuit board, and should never be charged at more than 1C. These
also have the lowest discharge capacity, and will explode if charged or discharged too fast (1C)!

ICR LiCoO2 (Lithium Cobalt Oxide)

High Discharge Capacity: Better chemistry means these don't really need a protection circuit.

IFR LiFePo4 (Lithium Iron Phosphate) Have the lowest voltage per cell, and far from the highest capacity, but they have the longest life of any battery.
IMR LiMn2O4 (Lithium Manganese Oxide)
INR LiNiMnCoO2 (Lithium Iron Phosphate With Nickel/Manganese Oxide)

Primary cells (non-rechargeable)

ER Li-SOCl2 (Lithium Thionyl Chloride)
LS Li-SOCl2 (Lithium Thionyl Chloride)
CR Li-MnO2 (Lithium-Manganese Dioxide)
BR Li-(CF)x (Lithium-Carbon Monofluoride)
FR Li-FeS2 (Lithium-Iron Disulfide) - 1.5 to 1.8V "Energizer Ultimate"

The numbering usually refers to the size of the battery, a 14500 refers to "AA" size of 14mm x 45mm, a 18650 is 18mm x 65mm, and so on. At least with ICR, IMR, INR, and IFR types. So, "AA" size 3.7V primary cells are ER14500 or LS14500.

I'm going to add a breakdown on C rating.
There are a couple of factors to consider when trying to quantify capacity and discharge capacity. The "C" number is the minimum time the battery can be safely discharged completely in, quantified in fractions of one hour. So when they give you the capacity in mAh, they are telling you the 1C for the battery. So a 5Ah battery can be discharged completely if discharged @ 5A for one hour. This way you can multiply the mAh capacity by the C number to calculate the maximum sustainable discharge rate, in amps, with the time you can do it in given.
Let's say we have 2 identical looking packs, same size and weight, same capacity, 5Ah, but we'll make the first one a 20C and the other a 30C. The 20C battery can be discharged in (60/20=3) 3 minutes @ (20x5=100) 100A. The 30C battery can be discharged in (60/30=2) 2 minutes @ (30x5=150) 150A.
 
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#19
Samsung ICR18650-22p cells, commonly the type in these hoverboard packs, are effectively empty at a static 3.40V.
Static voltage is resting - no throttle, release throttle for several seconds for good reading.
Typical 36V controller has a LVC (Low Voltage Cutoff) of 30-31V.

You will notice speed loss and a severe voltage sag as cells reach 3.40V 34V pack voltage.
Recommend the use of an LCD voltage meter as fuel gauge.

If you want better control-monitor I suggest a Voltage Amp Watt Ah meter - about $11
More - Volt Amp Watt Ah meter - blue are LCD black are lighted LCD
Can also monitor Ah used or charged!

Note: I've run these packs at 2p (8.8Ah) for quick trips and 4p (17.6Ah) for pleasure cruising.
Also, I run as 3p (13.2Ah) on my Snow Beast (only short trips in cold and snow). These cells-packs show excellent voltage sag resistance in cold enviornment.
 
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bakaneko

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#20
Samsung ICR18650-22p cells, commonly the type in these hoverboard packs, are effectively empty at a static 3.40V.
Static voltage is resting - no throttle, release throttle for several seconds for good reading.
Typical 36V controller has a LVC (Low Voltage Cutoff) of 30-31V.
Thanks, I was always wondering what the actual brand name of cells. Sometimes, you just cant trust the eBay sellers specs. I have a watt meter to check the voltage and amp-hours used. I think the lowest I got it was like 35.95V resting after a 80 mile ride. The cost to power ratio of the powerboard battery packs is impressive. Not the best cells but definitely not the worse or worse than SLA. =)
 
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