HOW VOLTAGE DROP AFFECTS BATTERY CHARGERS
ฝัง
- เผยแพร่เมื่อ 17 ธ.ค. 2022
- Undersized wires can cause excess voltage drop which will prevent your battery charger from fully charging your battery bank. This video explains why.
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As the current drops when the battery nears full charge, so the voltage drop will also decrease. Stated at 3:22," the battery will never get fully charged" is then incorrect. To my knowledge (confirmed by measurements on a live system) the battery will get fully charged, but it will just take longer than if heavier cables are used (given that the charger is in constant voltage mode. In constant current mode the cable resistance is no factor providing the charger can ramp up the voltage high enough). Am I missing something?
Oof... although I suppose that's 'technically' true in some scenarios; under-sizing the wire is STILL throttling the charger to how it should actually be working.
When I'm designing a system, I'm always going to avoid something that I have to start with the disclaimer "Well... That will TECHNICALLY work, but...".
This is particularly true if a lead acid is being charged but less so in case of lithium as the battery’s resistance increase as it charges is much less, especially the last 10% of charge.
In all cases voltage drop is proportionate to current, so with all battery types it will fully charge to whatever voltage you set it to. It will be slower, but it will fully charge eventually. The reason to not undersized your wiring isn't because it is inefficient or because it will not fully charge, or not even because it will take longer to charge. It is because it is dangerous and can start fires. The speed your battery is charging at doesn't matter if your van or RV is in fire. A little undersized is fine, it will just take longer. Too much undersized and you get fires. Where is the line? Caveat emporium. If you aren't an electrical engineer, properly size your wiring.
Definitively learned something. Great video.
Glad it was helpful!
Merry Christmas! 🎅
Thank you for sharing your wisdom.
No problem. Happy to help!
Appreciated as always, Thank you.
Hey Dj PsYcOtIc, No problem! Glad it helped! :)
Hi Nate! Really well explained video, as always. One thing i did was to measure the voltage at the house battery as i had quite a long run and i ended up with 14.1 so i went into the settings of the victron dc-dc and upped the voltage so that the house battery received 14.6
Thanks!! Glad you found a fix that worked for you. What prevented you from putting the Orion closer to the house battery?
@@EXPLORISTlife again like you said I have always been told to mount as close to the battery as possible. Same as mppt controllers BUT from what you said I reckon your option would work same if not better than my fix. You have opened up another fix for us people and we all appreciate your efforts. Thank you
Hi Nate! Really well explained video, as always. One thing I'd raise regarding voltage drop while charging LiFePO4 batteries is that it shouldn't matter too much because of the non-linear voltage to state of charge curve of this chemistry. The upper voltage knee of a LiFePO4 battery means that the difference between 1% and 5% voltage drop overall is likely to be pretty negligible in terms of the actual SoC of the battery itself - some will argue that constantly max charging a LiFePO4 will actually reduce the potential service life of the battery. tl;dr is that it won't really matter that much unless you have an "every amp hour counts" scenario. A couple of other examples that would better illustrate the benefits of over-sizing your cables, could be in other low voltage applications where you could have strings of lights that could suffer from excessive wire length, even though their current demand is relatively low, or better still, why it's really important to keep your high current runs between your battery and say, a distributor or Inverter, as short as possible, because the resistivity of the cable at high currents is just wasting energy by heating the wire. And of course, if you've oversized your cables, you're likely to be in a better place if you need to upgrade in the future.
Perhaps, but I'm always going to recommend charging a battery to the voltage that the manufacturer recommends. Where you'll run into issues is if you have a battery monitor in the system: If you set your 'charged voltage' of your shunt to 14.4 and set the charger to 14.6 and excessive voltage drop is only charging at 14.1V; the battery monitor will never re-synchronize at the charged voltage to 100%; which will yield inaccurate battery monitor readings.
@@EXPLORISTlife That's fair - I'd not considered battery monitors. I actually really liked the suggestion you made in the video about the Victron smart battery sense lead for MPPT chargers - that's quite a neat way of getting around resistive losses if you can't easily co-locate the charge controller and the batteries.
@Chris Bassett gosh I wish I understood what was being said. no need to reply I was just making a comment. I've had so much going into my brain over the past month or 2 with solar n everything else I'm kind of overwhelmed. I do know more than when I started though that's for sure. but it sure gets confusing. And then I I try to find either the comment or the spot in the video n the spot so difficult to find🙂.. I don't know how people did it back in the day. Days we have great people like Nate to help us navigate through all the trials and errors
jesus christ this guy elettrotecnics
Again, well done explaining 2 viewers; it is educational n Ur video is *qualify as instructional video like Ur other video that draws picture to make connection, or related or associated with similarities is good way 2 understand n remember, fireman truck hose to burning house comparing an below battery to bulb or load device, which used up voltage and between culprit is resistance or ohms, which we must use-Or-2-replace-2-thicker-gauge-wire-guage-to-reduce-resistance-or-ohms, and clean N brush up corroded device connection like battery cable to battery post and we also forgot to remove battery that have been inserted 2 battery chamber where many cases we left them for quite some times and result is corroded battery and device would not turn on OR will not work, also causing significant reduction in voltage drop in a case like battery terminal or NOT battery cable NOT fully connected 2-battery-terminal, still LOOSELY connected so lose lots of voltage drop! Of course, anywhere circuit open area, wire, etc. meaning NO voltage! Other cases is wires got *TWISTED cause big voltage drop or result in **shorted-*2-*power-meaning wires got ended up connected to other wires, NOW wires got connected to more than one intended wire, and often happens case where wires got exposed due to hot exhaust pipe heat and wire coating has been melted and as result connected 2-other wires that was not meant! like near exhaust pipe, and of course **shorted-*2-**ground-meaning FUSE(s) is or are blown!
Hey RubiconKLBRUTO Rowman, No problem! Glad it helped! :)
Hi Nate. Thanks a lot for your videos! Also a complete electrics beginner. I have a renogy 40a dc to dc charger. I believe this gives out a surge current of 60a or sth like that. My one-way run length is 4.5m, so 9m in total. I was planning to use 4awg wire between my starter battery and dc to dc charger for a voltage drop of roughly 3%. However I am now reconsidering to use a 6awg wire which will be cheaper and less bulky when installing based on your guidance around only needing to meet the required input voltage of the dc to dc charger which in my case is 8-16v which should be fine. I will also place dc to dc charger right beside the house battery. Am I on the right track?
Nate, is the use of a Victron Smart Shunt and Smart Networking equivalent to a remote batter sense? Provided of course the shunt is located very close to the negative terminal of the battery bank. This is what I’ve been using to charge my battery bank and independent voltage measurements confirm it works. If so you might want to inform people about that. It’s also an additional reason to purchase a Smart Shunt over a ‘regular’ shunt. I use the Smart Shunt and Smart networking to tell all of my chargers (MultiPlus, DC-DC, Smart Solar) what the battery bank voltage is. I hope this is a smart thing to do.
These are great videos! I wish you'd had them before I built my system. lol
🤷🤣😂
Hi Nate, extreme beginner here trying to really get a handle on this before I get rocking on my power system install. As always, I VERY much appreciate your approachable electronics explanations!
So my take-away here (please correct me if I'm wrong) is that in this scenario, it's best to have the DC DC Charger closer to the battery bank than the starter battery. Given the inbound side of the charger can handle more of a drop, would we make sure the charger is as close as possible to the house battery to eliminate as much drop as possible, so we're as close as we can be to that 14.6V required charging?
Exactly!
I know you guys work mainly on vans. In the future would you consider talking about fitting a average trailer conversion. Not the monster motor homes and fifth wheels, something like a couple or small family would use. Say 17 to 25 feet.
I know this is primarily about voltage drop but why haven't you discussed the smart sense before? Maybe I missed it but it's relatively inexpensive and looks like an easy addition for a victron system. I assume you just add it to the victron network and it controls the mppt, of which I have 2, so it would adjust both of them appropriately. I'm still weary of the DC to DC charger as it gets very hot and I'm running out of room but I assume it would control everything in the network.
Hi, I bought a 24/12 30amp orion dc to dc charger but I have a 12v system. It said it works for both systems. I'm worried that if it drops below 14v it will shut off and not turn on until it reaches 15v. So is there a possibility that it will switch off and not come back on since 12v won't reach 15v input ? 🤔
Hi Nate, I used you renogy wiring diagram for my build. I have 600 watts of solar and 400AH of lithium battery. I’ve set all my appliances to lithium and recently has my whole electric setup shutoff at 50% battery. I have a renogy smart shunt. Is there something I need to program so it doesn’t shut off at half battery life?
That does indeed sound like a settings issue. I'd triple check your user manuals to learn more and reach out to Renogy tech support for more help if needed there.
Nicely explained. Why run from the starter battery compared to from the alternator? And does that B2B charger know not to run the starter battery flat? Regards
It's usually much easier to attach wires to the starter battery than the alternator and the wires going from the alternator to the starter battery are always rated to carry the full load of the alternator, so voltage drop is rarely an issue there.
First time I’ve seen voltage drop from a DC to DC charger to Li battery be discussed and it totally makes sense. But what is solution in 2001 dodge class B van when house batteries are not in a tight, non-weather proof enclosure that would not accommodate a DC to DC charger install? I was assuming I’d mount in under hood next to van battery, but now I’m questioning that plan.
Yeah, it needs to be closer to the batteries. Usually it's easy enough to locate the charger inside the camper 5ft or less from the batteries, which will be plenty close enough.
Hi Nate, Ive been following your series for my project. I'm trying to add a way to charge my system using ev charge stations. Do you have any content that demonstrates that?
I do not. Charging your house battery bank from a public EV charging station is a good way to get vans and campers banned from even more parking lots than they already are. Charge from solar, alternator or onboard generator. If you need to plug in, go to a campground.
@@EXPLORISTlife good point. Makes sense why this isn't a bigger thing
Very useful as ever! I was wondering if you ship overseas (Victron and wiring)? Thanks.
Yep! Sure do.
I was just dealing with this problem in my scamp, wiring is all too small to be able to send the full 30amps to my lithium battery. Time to put in some 4awg left over from my car audio days lol. 😀
I do have a question on ground wire. can you take the positive from starting battery to dc to dc charger then take the ground input to dc to dc charger from frame or closer ground source or does ground need to come from starting battery as well. asking since starting battery is already grounded to frame. thanks
I recommend running the negative all the way back to the starter battery for more a reliable connection as shown in all of our diagrams at www.explorist.life/solarwiringdiagrams
@@EXPLORISTlife got it, thanks
I cannot find wire sizing calculator you are using, can U post link Nate? Ths.
explorist.life/wire-sizing-calculator/
Nate: Does your online calculator take into account the drop for the entire circuit, or just one direction? The voltage that matters is between the positive and negative terminals of the battery. If the positive and negative wires (paths) are the same length, and you have a 2% drop on the positive wire/path, you will also have a 2% drop on the negative wire/path, and the battery will actually see a voltage that is 4% less than the charger is putting out.
Total wire length. 10ft negative +10ft pos = 20ft wire.
@@EXPLORISTlife Thanks for clarifying that.
VERY GOOD, yes very good information. Hehehe I have to do some rewiring.
Thanks! 🙂🙌
How does using chassis ground affect the voltage drop calculation? My 20a renogy dcdc charger has input neg connected via 18" 10awg to lynx power in grounding terminal, which is connected via 18" 2/0 to chassis (drivers seat bolt). I haven't measured the voltages, but I will ... later.
Good question! With wire, we have specific resistance measurements for different sizes of wire that gives us the voltage drop results. With a chassis ground, we don't have resistance coefficients, so we can't calculate that. Plus... every chassis is different depending on how the body/frame/etc is connected. This is one of the biggest reasons I never recommend using the chassis as a 'current carrying conductor' like with a non-isolated charger.
Can you run a 2awg 95% of the length and step it down to 6awg the remaining 5% to fit the charger?
Thank you for sharing this information Nate, it has helped us alot!
Out of all of the systems I've seen and helped with, I've never seen a scenario where that is necessary.
If somebody finds themselves installing a DC DC charger in the back of a 100ft long rv and 6awg doesn't cut it, use bigger wire and a pin terminal instead of downsizing the wire, or just fill the 100ft long rv up with solar panels and forget the dcdc charging.
@@EXPLORISTlife
Thank you, I was not aware pin terminals existed , I have seen millions of videos of electrical work done and never came across this type of terminal.
@@EXPLORISTlife I am thinking of this very setup (above) for my 5th wheel trailer, with alternator charging. As I see it I am going to have about a 25 ft (50 ft)run thru the truck to an Anderson connector near the hitch. From there the wire will run up the hitch, thru the front bay and into the pass thru compartment where the batteries will be mounted. I am thinking this will take about another 25 ft (50 ft) of wire. In the pass thru compartment it will be feeding 2 30amp DC to DC chargers and maybe a 3rd, new alternator.
I am thinking 2 GA wire from the truck thru the Anderson connector to fused buss bars close to the chargers. From the buss bars to the chargers it is going to be 6 GA, a couple of feet. I have 600 AHr of batteries that I am going to be working and may expand to 800 or 1000. I will be adding solar to help offset battery usage. You never know when the sun may shine and when not and for how long. I am looking cut voltage drop to a minimum.
Bob
As the voltage drops from the starting battery to the charge controller, the controller draws more amps to compensate for the voltage loss so that the house battery is charged at 14.6 volts, correct?
Basically, yes.
A "tactical" solution is to run your 2 or 0 gauge wire from the battery up to a buss nest to the charger. Then from the buss to the charger you run a very short 6g jumper. Yes not ideal but in some situations it solves the voltage drop issue when you do have to traverse a long distance.
A 'pin terminal' is another solution if wire larger than the terminal is absolutely necessary, but I pretty much never run into a scenario where a wire oversized to that degree is necessary.
Not seeing link to calculator, thanks
Ditto!
Why would you use an isolated Victron instead of non-isolated, in a van build or trailer.
I always use isolated because they work in 100% of use cases, no questions asked.
DIY CAMPER, try to make a Smart Battery Sense video lesson and also how to compute/calculate the voltage drop % percentage with the Wire Gauge using the manual way if you didn't have that wire size calculation program how would you do it the old fashion way?
I've got a video a while back that teaches you how to size the wire from the hand-written calculation. You can use the same formula to determine voltage drop. I will not be making a video on that, though, as nobody really wants to do that calculate voltage drop by hand without a calculator.
@@EXPLORISTlife I mean using a calculator using formulas to compute the wire size and voltage drop percentage, instead of using that app software program. I know to use ohms law to compute voltage drop but I don't know how to compute the voltage drop percentage and wire size
I see. Yeah, you'll probably just have to look that one up on your own. I don't suspect enough people would watch that video to make it worth one of my weekly uploads. Otherwise, you may just have to suffer through with the app I made for you that does all the work automatically. 🤣😂
@@EXPLORISTlife i mean you can throw it into a new video if the lesson had to compute the voltage drop percentage and wire size because most other subject lessons will have to compute the voltage drop percentage and wire size it will come up again in future videos
The video I made a few years ago talking about how to size wires shows the formula, if I remember correctly.
The difference in SOC between 14.6V and 14.2V is nothing. Maybe a single AH. MAYBE 2ah.
And highly unlikely you're going to be pushing 30A by the time you are above 14V. You are past the knee and voltages inside the cells are rising very rapidly.
I think your white boarding would be better to do at what you expect a during bulk charging - 13.3 - 13.7V.
Oof... although I suppose that's 'technically' true in some scenarios; under-sizing the wire is STILL throttling the charger to how it should actually be working.
When I'm designing a system, I'm always going to avoid something that I have to start with the disclaimer "Well... That will TECHNICALLY work, but...".
I'm always going to recommend charging a battery to the voltage that the manufacturer recommends instead of purposefully a few amp hours lower when the problem could be solved by using properly sized wire. Where you'll run into issues with not charging to full voltage is if you have a battery monitor in the system: If you set your 'charged voltage' of your shunt to 14.4 and set the charger to 14.6 and excessive voltage drop is only charging at 14.1V; the battery monitor will never re-synchronize at the charged voltage to 100%; which will yield inaccurate battery monitor readings.
So are you saying that if you mount the charger in the back with that batteries it will charge the battery to 14.6? I got lost! Sorry.
Mounting the charger near the batteries that are receiving the charge will be best, yes.
@@EXPLORISTlife This is incredibly timely and helpful. I'm basing my electrical overhaul off of a mix of a couple of Explorist wiring diagrams and had planned to keep my Orion further from my batteries but will tweak it to be more like the diagram now. This answers the biggest remaining question I had for the whole build.
Big wiring kit purchase incoming! Thanks for all you do.
Can you take actual measurements for what you are showing? I suspect that once the charge controller hits 14.6 then the current will begin to drop and you will not see 30amps at that voltage but instead current will drop significantly causing much less voltage drop.
Yeah, maybe, but why not just size wires appropriately for the full load the whole time instead of toeing the line of cutting corners for the sake of saving a couple bucks in wire?
@@EXPLORISTlife Wasn't suggesting to use smaller gauge wire. I was suggesting that the voltage drop is not a concern since the current will begin to drop and there for you will get fully charged batteries regardless
Won't the lack of full charge due to excessive voltage drop during the bulk phase of the charging cycle be made up by a slghtly extended absorption phase?
You mentioned the mid input voltage on the dc:dc converter being 8V. If you have a min battery voltage of 12V, that is a max allowable voltage drop of 30%. Yikes!
But when you're talking about a 'slightly extended absorption phase', if we are talking about a DC DC Charger, wouldn't it make more sense to just size our wires appropriately so that it's a non-issue?
For the 8V minimum on the Orion, although that's technically the minimum... it'd take something like 200+ ft of wire to get that kind of voltage drop with 6ga wire and 30a, so unless you were driving a truck pulling a camper that was pulling a camper that was pulling a camper where the house batteries were charged from the alternator... this is a non-issue. I've never seen this kind of voltage drop presented in a real life scenario.
It’s all about wire size and length when it comes to battery charging, regardless of chemistry. You want the largest gauge of wire possible so that the high current is distributed over a wider surface area, equating to less heat (safety issue) and you want the shortest length as the ‘further’ the electrons have to travel, the more ‘tired’ they are when they get there = voltage drop
@@EXPLORISTlife what I was getting at is that it is very arbitrary. The example you gave was a ~10% voltage drop not allowing the batteries to fully charge. I am saying they will fully charge during the absorption phase, and it will be a negligible difference in time. This of course is if you have the voltage drop on the dc:dc output wiring. On the input side it is even less important. Voltage drop of 5%, 10%, or even 20% is easily overcome in the dc:dc. There is the case of using voltage to detect ignition on that will demand low voltage drop.
I guess what you are saying is that 6ga wire is overkill for most 30A circuits.
@@marvs4321 heat from 30A? Your house uses 10 ga for 30A and it runs in a wood framed house. Probably not recommending 10ga for long runs of 30A in a 12V system.
@Doug G Perhaps, and maybe, but that's a bit of a hack that comes with a lot of gotchas and other cinsiderations. Another spot youll run into issues with purposefully undersized wires like you are suggesting is if you have a battery monitor in the system: If you set your 'charged voltage' of your shunt to 14.4 and set the charger to 14.6 and excessive voltage drop is only charging at 14.1V; the battery monitor will never re-synchronize at the charged voltage to 100%; which will yield inaccurate battery monitor readings.
If 12ga is rated for 20 amps, how could 10ga be rated for 50-60 amps..???
The higher the temperature rating of the insulation on the wire, the higher the amperage rating for the wire will be. Compare the max amperage for wire with 70 degree insulation vs 105.
Yeah but you to need to mention not to use such a skinny wire to squeeze in to just over the 8 volts as the wire resistance will make the wire very warm at full load.
There are always fun hypotheticals, sure... but to get that scenario you're talking about would be a circuit length of longer than 120ft (10% is as high as my calculator goes and 6ga at 30a and 120ft is 10%); so yes... If you are driving a truck pulling a camper that is pulling ANOTHER camper trying to charge the furthest back camper from the trucks alternator... you may have to do something different. 😂🤣 Out of the 1,000's of systems I've helped with...I've never run into that scenario.
I consider any wire, lug, screw or stud temperature that is warm to the touch as inefficient and a bad design. Especially in 12v systems. And this can easily be achieved by increasing wire gauge 2 sizes over 20 odd feet in a van. As people have a tendency to cheap out on wire and peripherals once they have spent a fortune on the main components
6awg wire carrying 30 amps over 20ft like what we have in our Orion wiring kits at shop.explorist.life will not get hot and is only 4.5% voltage drop, which is well within proper design parameters.