When you have a load with about 10mOhms and wires of maybe double that resistance... yes, obviously. We are talking about fractions of an Ohm, fractions of a volt and losses always add up quickly. :))

@GloweIndustries

Жыл бұрын

Hey now, I’m offended! 😅 All our cells are sub-m ohm. We literally don’t sell any cells over 1m ohm. And that’s when a 2 m ohm chunk of wire can quadruple the load’s resistance.

See if you can find a charger with sense input. The sense leads connect via separate cables directly to the battery terminals and compensate for loss on the charging cables.

@GloweIndustries

Жыл бұрын

A lot of the battery testers I use have 4 wire input. That’s not going to beat the resistance on the charging lines though when a static voltage limit has been placed.

You might also want to pull the case off and have a look at the internal wires, mainly the two going from the board to the back side of the Pos and Neg banana terminals. I can't remember what mine were for sure but I think they were 14awg internally. So I just soldered a run of 10awg for Pos and Neg on the inside of the case. After I got it out back together I made a couple 10awg leads, the difference is huge!

@GloweIndustries

Жыл бұрын

Good idea, but I primarily use a much larger charger. This was more or less for demo purposes.

All of my charging sources used for semi-permanent charging have 10 gauge wire. It's good for 30 amps (40 amps for 90C THHN) for long runs and easily 20-25% more for the very short runs associated with most battery charging - that's also why they make IR thermometers ;-) Even some of the physically small lithium-based packs have serious current potential. A Fuji 12 volt 9AH battery pack has a 4s3p configuration of Murata LiFePO4 26650 cells that can deliver 25 amps per cell. If you plan to use the pack's full capabilities, you'll need a big BMS and some serious wiring. I'm more likely to use a pack of its physical size as a replacement for an AGM UPS battery so a 30 or 40 amp BMS is fine and we're back to 10 gauge wire. Nice to have a UPS where the UPS' low voltage shutdown is higher than the LiFePO4 pack's low voltage cutoff. The UPS can never damage the battery by excessive discharge - that plus the usual overly agressive charging UPS units do (to get the battery back to full capacity as fast as possible) contribute greatly to the short life the AGM batteries in UPS units experience.

@GloweIndustries

Жыл бұрын

Notyoung, the batteries that we (Glowe Voltage) sell are designed to sustain over 400 amps. They're abused in car audio situations every day, for sure.

I wonder if the resistance would be less if the ring lugs were the correct diameter of the posts on that charger? I noticed they looked larger than the post size, be interesting to see any difference? Thanks for sharing as il be charging up my new bank soon 🇦🇺🤙

@GloweIndustries

Жыл бұрын

I imagine it would help at least a small amount, sure. Fractions of a miliohm add up fairly quickly when the batteries you’re charging are only fractions of a miliohm for sure. Real easy to double the resistance to the load.

You have to be extremely careful using bench power supplies to charge batteries. I have that particular Hanmatek and, like most bench supplies, you absolutely cannot put reverse voltage on its output leads. This includes turning the supply off (like you just did) or unplugging its AC cord while it is still connected to the battery. Now, when connected to battery cells at such low voltages, 3.65V, it might be able to handle it, but as a rule, you are playing with fire. A dedicated battery charger is almost a requirement. That said, I use my bench supplies to charge batteries too, but I run the output through a bunch of Schottky diodes in parallel (each one can handle 4A in free air) to protect the supply. Which works great for battery packs, I might add. But doesn't work well if you are trying to charge individual cells such as in your video. It is difficult to get the correct output voltage since the diodes have around a 0.34V drop under load, but that decays to no drop as the current goes down. I typically use 20SQ060 Schottky diodes for that purpose (which can withstand 60V of reverse voltage). So for charging individual cells at 3.65V (or individual cells in parallel at 3.65V), there is really no good solution that is safe other than using a battery charger capable of outputting 3.65V. -- 8 gauge can carry 40A, that's really overkill I think. 10 AWG or 12 AWG is fine for this purpose. Sure, there is a voltage drop, and when your output is set for individual cells I totally agree it does make a difference. But the drop isn't that great as long as the wires are short. More importantly, DONT USE BANANA PLUGS! That's the key. Banana plugs are horrible for carrying real current. In fact, they are an arcing and fire hazard at high currents. Instead, crimp ring terminals on your wires and use that to get a solid connection to the power supply. I think using ring terminals are more important the low AWG in this case. Ring terminals on 10 AWG or 12 AWG should be fine at 15A. Also, the lower the amperage, the lower the voltage drop. So once the current drops off it basically doesn't matter what gauge the wire is. Wire losses are a function of the square of the current so losses at 4A are only 8% what the losses at 14A would be.

@GloweIndustries

Жыл бұрын

Good input!

@jasonbroom7147

Жыл бұрын

That was my immediate take-away as well...just switching from banana plugs to ring terminals was probably 90% of the net gain.

I have some copper pipe.. think they will work fine as my new charging "cable" :) thanks for the tip!

@GloweIndustries

Жыл бұрын

Haha, let us know how that goes! Bare minimum sounds like the start of a really good bus bar.

I like when people know why- and not just - THIS is how it's done, - no idea of Why it's done that way -lithium -all types, use a CV maximum because of the separator that is used - between the anode and cathoid, it has the same -structure in Lithium-ion, and Lifep04, ... above 4.2 (critical 4.9) it will start to short out, it's enough voltage to overcome its resistance .. it's just as sensitive as a capacitor (like supper capacitors) to over-voltage, it's not the current charging it is why 4.2v - it's for safety, and a mean point for best Cycle-life and capacity .. - Lifepo4 can also charge at 4.2v, but it's not going to get its 20k cycle life... but can safely charge at that voltage - now it's a different chemistry - the advantages do not outway the cost, - the voltage will still drop down to 3.35-ish at rest, and still have its FLAT discharge curve - battery types that fast charges like NIHM/cd or Flooded acid.. can keep raising the voltage to maintain current .. this is called VV/CC (variable voltage constant current ) there able to do this because they burn off excess charge as a heat ... - a nihm, it has a resting voltage of 1.4v, nom of 1.2v - a Vary flat discharge curve ... you can go up to 5v-cell during charging, this will not damage it at all ..., there are multiple ways of knowing when it hits FULL-charge, the easiest way - it heats up and gets hot to the touch.. .. (or a charge will look for the voltage of the cell, it drops slightly at FULLy charged ) flooded acid can do this vary similarly, above 2.45v it's going to start off-gassing , you must replace the electro-water ) - attempting this even 1 time on Lithium will destroy its live-span and can be very dangous if you do not know that already

@GloweIndustries

9 ай бұрын

I like LifePo4 if for nothing else than how safe they are. I've been completely unable to ever make one catch fire or do anything worse than vent.

Ha....the first thing I thought when you said you were changing wires, was that the resistance would be lower. Didn't know how much it would effect though.👍

@GloweIndustries

Жыл бұрын

A lot!!

Understanding what the voltage drop means and I mean 'really' means is important if you are going to be working with high amp circuits. Another test you might want to start doing to have some fun and learn a bit. When you are doing these charges... take a multimeter and measure the voltage between the PSU output + post and the cell + post. (Wha?) Yep. The multimeter will read the voltage drop. Makes sense right? Now do the same for the - post and - cell terminal. You will find the same voltage drop. Put the meter down. Have a cup of coffee or a beer and ponder what that means. Usually we would consider "GND" or - or NEG as being the same for all items in the circuit. It's very important in many cases that they are the same. However the experiment above just showed that they are not at all equal or the same in a high amp circuit.

@GloweIndustries

Жыл бұрын

Paul, our 48 amp hour battery is capable of sustaining over 12 volts with a 420 amp load. Voltage drop is literally the primary issue we work to combat with what we use lithium for. We are powering car audio systems running at 60,000+ watts daily. Is that high current enough for you, or are you just here to attempt to be condescending while making yourself look foolish?

@GloweIndustries

Жыл бұрын

Also - please see my other video about voltage drop between a psu and the cells and ways to drastically improve charging speeds. We’ve covered this.

@1over137

Жыл бұрын

@@GloweIndustries I was trying to be helpful. I'm not sure if you delibrately leave out or seem confused by the details and measurements you are seeing or not. 60kW I'm going to assume you mean peak power. You should never be bringing that power requirement anywhere near the batteries. Usually the peak power rating on an amplifier is limited by the main bulk caps and how much they can safety dump and sink as instantaneous current. It's also a very reactive load, speakers push back. Ideally the amplifier itself should produce a constant impedance on it's power input, such that it's current stays "flat" and doesn't jump around but follows a smooth RMS average. If you are seeing current spikes into the amps (you'll need a scope) I would suggest a super capacitor bank directly on top of the amp, let it take the current spikes and use your lithium cells with a current limiter to charge them. The super caps can provide massive current and if they are wired onto the amplifier bus bar power input, it can provide it without (too much) voltage drop. You work with audio, so you understand the impact of the ground moving by even 0.1V. Luckily you also have a massive big heavy block of metal to use as a ground bus bar! The chassis and engine block. It will take a LOT of current to drop 0.1V across that!

@1over137

Жыл бұрын

The reason I'm following along is that I am making a lithium iron audio battery, just with a different purpose that yours. I do not need high current. I need high voltage, positive and negative rails and I need silence. Going with 6S LFP 14Ah Varicore cells. To get 21V and +10.5V and -10.5V tapping the centre of the pack. It will power anything connected to my audio gear that can't be optical. DSP, DAC, ADC, headphone amp, desktop speakers etc. When it's in use it will galvancially separate itself from the world. When it goes to standby it will connect itself to a DC power supply and charge. So as long as I let it sleep and charge, it should be ready to run for quite a few hours without any noise induced from the busy computer and electronics lab power rails. Testing out the JK-BMS's this week. Also got a active cap balancer to play with, but I expect it uses more than it saves and should only be trigger when necessary.

The first mention of Ohms law was incorrect. The current flow into the battery is not determined by ohm law, maybe a tiny bit, but the current "sink" nature of the battery is just that, a current sink/source. They are actually pretty complex to model in electronic primitives. A capacitor with a series resistor and inductor with a self disharge resistor across it is barely adequate. The wires IS ohms law. The voltage drop in the cables is by definition determined by current and the resistance. Chose cheap ass chinese test leads are well known for being high resistance. It was these that opened my eyes to the problem as well. However, a tip. In future, you don't need to go to the lengths of making new heavy gauge wire for everything. Instead you should be basing your charging, not on what the power supply says, but what the battery says. Put a voltmeter on the cell(s) themselves. You will find that while the PSU is saying 3.65V 5A the battery is maybe saying 3.45V and you are losing 200mV in the cables. This is how every BMS ever made (worth buying) works. It's also how any of the proper battery testers work. 4 wire connections always. Similarly, if you invest in a resistance meter it uses 4 needle sharp gold plated probes. 4 needles such that while one pair pulses the current the other pair can measure the voltage. So. Use your older smaller cables, but if you want to hurry up the charging, set the charge voltage based on the cell end of the wires. So if the battery is 200mV lower, turn the PSU up 200mV. Just be careful as when the current starts to fall that voltage drop will reduce as well.

@GloweIndustries

Жыл бұрын

Also, I absolutely use a four point YR1035+ to test small amounts of resistance. This video illustrates more how much of an impact adding like 10 miliohms of resistance in wire has when the receiving load has sub-miliohm resistance to begin with. More or less it’ll stay in CC mode a lot longer (as long as ohms law lets it based on the max output voltage of the charger and the resistance of the load including wiring.)

@junkerzn7312

Жыл бұрын

@@GloweIndustries You don't need to use a 4-point, though I have to admit it is cool to measure small resistances like that (I have an 8845A myself for that and similar purposes). Just measure the voltage drop under load with a normal multi-meter. Keyword being, under load. They have plenty of precision for that purpose. To be frank, any voltage drop under load that is below 0.02V or so just won't matter in this case. For LiFePO4 cells, 3.65V can be your voltage target for top balancing as long as you don't hold it there too long (a few hours at the most IMHO)... you don't want to over-volt the cells after all, so that will give you the most current for the longest period of time. That said, the voltage curve as you charge LiFePO4 cells goes exponential once they charge past around 3.50V, and the current will rapidly drop-off. So a few tens of millivolts of voltage drop under load is not going to make much of difference in terms of charging or top-balancing the cells. Remember that the power lost to dissipation in the wire is a function of the SQUARE of the current. It matters for large currents but the voltage drop will disappear as the current goes down near the end of the charging cycle.

One more tip. When you are pushing high current into one of your parallel packs. Do remember to check for voltage drop across the bus bars. You'd like to hope, with using proper copper bars the resistance will be measured in 10th or 100th of miloohms, but that can still result in a small voltage drop between cells in parallel. Usually more a concern on the discharge side when the current is 100-200A. To push 100A through 1 Ohm you need 100V. Pushing 100A through 1mOhm drops 0.1V. 10mOhm its a volt. Volts * Amps = Power. 100A * 0.1V = 10 watts of heat probably fine. 100A * 1V = 100Watts. Now it starts to depend on where that 100W is being concentrated as to whether it's going to start a fire or not.

@GloweIndustries

Жыл бұрын

… when top balancing in parallel? I’m a firm believer you should let the cells rest with no external charge until all of the cells match. Very much for the specific reason that one cell will normally be 3.65 with another at 3.58 etc due to the resistance from the point of charge. I agree with you here and have observed this first hand. It is especially prominent when doing like 16 cells in parallel to top balance for sure.

@GloweIndustries

Жыл бұрын

Also, CC/CV charging is good for this because the higher voltage cells once they reach the max voltage will begin trickling juice to the other cells while the charging gets drastically slower due to the voltage between power supply and the cell it’s connected to being close in voltage.

Are you really charging 4 cells in parallel to 3.65V and negligible current? That’s way overcharged compared to the manufacturer’s stated charge termination point of 3.65V max at 0.05C. If those were 280Ah cells and you have 4 in parallel, you should be stopping once the CV phase current drops below 56A. Any lower than that and you’re overcharging with detriment to the cell longevity.

@GloweIndustries

Жыл бұрын

Hmmm. My manufacturer states to use CC/CV charging to 3.65v.

@PVflying

Жыл бұрын

@@GloweIndustries I bet they also state that whatever cycle life they’re forecasting is based on terminating that charge at 0.05C, ie not tapering to zero as you seem to be trying to do. That little detail gets overlooked by everyone, even the resellers don’t understand the significance. We all know the voltage rises in proportion to the current you’re pushing when charging, just as it drops when drawing current to a load. That effect becomes exaggerated in the top knee, so when you charge to 3.65V tapering down to zero, you’re at a higher state of charge than if you stopped charging when current tapered down to 0.05C level. Proper termination at that point would likely see the terminal voltage drop straight to 3.37V per cell and yet you’re fully charged. Pushing more in can be done, but you bet it’s having some effect on cell longevity. It’s a subtle detail easily overlooked, but if you care about your cells lasting their full lifespan it’s worth paying attention to.

@GloweIndustries

Жыл бұрын

@@PVflying .05c would be 1.6 amps on this 4P bank of 8ah cells.

@PVflying

Жыл бұрын

@@GloweIndustries I didn’t realise you were using 8Ah cells. They looked bigger

@GloweIndustries

Жыл бұрын

@@PVflying they actually might have been larger cells. 🤔 genuinely don’t remember, filmed this kind of in a hurry. That said: 3.8v is the limit on most of these cells, with 3.7v being the “operational limit” which we don’t charge them to.. If charging should be stopped at cv mode at .05c, it would be impossible to use a 10a lifepo4 charger to charge a 280a bank, yeah? Lifepo4 chargers generally charge up to to where cv is switched on, and maintain that charge until they drop to 10% of the chargers max output. This means that charging up a 300a bank to 14.6v with a 10a charger it does not stop until it reaches 1 amp of current.. so using anything under a 140a lifepo4 charger is detrimental (since it’d cut off at 14a) on a 280a 4S bank?

yep nope...

@GloweIndustries

Жыл бұрын

nope yep...