power inverter while lipo4 being charged

Thread Starter

shiver22

Joined Feb 1, 2024
5
Hi I have a 48v lipo4 battery with a separate charging input then the wire for output (discharge). I want to connect the battery to the car to charge it when the motor is on and have the battery discharge to an 48v inverter to the controller to power the red motor. I'm guessing this would cause the battery to die quickly or won't work at all. The motor is on all the time to use the fwd for driving so I'm wondering if I should just directly connect a 12v inverter to the controller that will control the motor in the rwd axle? Maybe change it all to find a 24 volt alternator to connect a 24v inverter to 280vac? I heard the higher th volts for the alternator the better for an inverter when running it continuously. It needs a lot of volts and amps to draw from so I'm a little stumped on the best setup to build a rwd electric drive in a car that already is fwd so it would become a hybrid AWD. I want to use as small of a battery I can to save weight and money by using the car engine as a generator for the electric motor while it's driving using the gas and electric. Sorry repeating myself now.
 

KeithWalker

Joined Jul 10, 2017
3,088
That is a lot of jumbled thoughts that you have presented us with. Can you put those thoughts into some kind of order that will explain your problem a little more concisely?
e.g:
What exactly are you planning to do?
What vehicle and hardware are available for this project?
What results are you hoping to achieve?
What, precisely, do you not understand?
 

MisterBill2

Joined Jan 23, 2018
18,388
Indeed I am not able to discern either the requirements or the specific information requested.
I am guessing that the desire is to have one motor driving the front axle and an inverter to power a 48 volt motor someplace else. So a more detailed description of the intended operation is needed before I can even guess at an answer. It also seems that english is not the first language of the TS, so there is probably a translation problem as well.
 

Thread Starter

shiver22

Joined Feb 1, 2024
5
Wow I've spoken English only all my life. The message clearly follows a train of thought. Although my spell check changed rwd motor to red motor that I didn't notice, I don't think it's difficult to to understand. Perhaps I should not have repeated what I was trying to to do; use the engine (ice) to oower
 

Thread Starter

shiver22

Joined Feb 1, 2024
5
Wow I've spoken English only all my life. The message clearly follows a train of thought. Although my spell check changed rwd motor to red motor that I didn't notice, I don't think it's difficult to to understand. Perhaps I should not have repeated what I was trying to to do; use the engine (ice) to drive the front wheels while trying to use the alternator to power the electric motor to power the rear wheels.

I have asked 2 questions; should I use the alternator recharge continuously. The lipo4 battery, while the battery simultaneously powers an inverter. The inverter will convert the power to the voltage that the controller will need to power the motor at the speed that matches the throttle of the car is of the front wheels. I know this can be done with lead acid batteries. Before you say it can't be done, the lipo4 has a recharge and discharge separate wire.

On to other option to remove the battery from the equation bypassing it all together. Just just run the alternator, to the inverter, to the controller, to the motor.

Normally a lead acid battery would be between because when the power is not going to the motor, it would be stored in the battery and stop surges.

In the second scenario, there is nothing from stopping asm surge to hit the inverter from the alternator. It would have no where for the power being generated from the alternator when the engine is running but the electric motor is not moving , therefore not drawing from it.

Are you following me? Will either option work or do I need a different solution?

Maybe I'm too young and you can't understand how younger generations talk because you are too old or are all IQ and have no EQ.

Don't bother answering. Your rude comments is offensive and I will not return to here.

It's true what they say about technical people... The post doesn't let me add to it after 19 minutes. That needs to be changed
 

Alec_t

Joined Sep 17, 2013
14,310
If you get the power to drive the rear wheels from the alternator, then the ICE has to provide that power to the alternator. That will reduce the ICE power available to drive the front wheels. Because of inefficiencies in the electro-mechanical conversions involved, the net result will be wasted energy, not the improvement you seem to be hoping for.
The Law of Conservation of Energy applies here.
 

MisterBill2

Joined Jan 23, 2018
18,388
I did not intend any offense to anybody!! On these forums we do have folks from all over the world and sometimes it is hard to grasp what they mean because of the language difference. And when a string of statements is difficult to understand that is a fair question.
And as for the "red" motor actually being a rwd motor, Now it seems that js Rear Wheel Drive motor, which makes more sense.
There have been several instances where folks simply state wire colors and somehow expect that we should know what that implies. So I took the word "red" at face value.
 

BobTPH

Joined Jun 5, 2013
8,921
You have a basic misconception about batteries. They cannot charge and discharge at the same time. Current can flow in only one direction, either into or out of the battery.

Devices like your phone, which operate while charging, are drawing all the power from the charger, not the battery when plugged in.
 

nsaspook

Joined Aug 27, 2009
13,231
Kids today, Moses (the master builder engineer) said long ago. Youth is sometimes wasted on the young.

The charge/discharge wires are BMS connection points. Having two wires to electronics doesn't change basic electrochemistry.
 
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MisterBill2

Joined Jan 23, 2018
18,388
OK, I see now rather clearly that the TS wants to add electric drive to the rear wheels of a front wheel drive gas engine car. A very interesting concept indeed, but certainly not a simple task. A very first question will be just how much power is desired to be added to the rear wheels? Certainly this could produce the ultimate "Sleeper" vehicle and win lots of money street racing. Just imagine what an extra 200 or 300 HP could do for an economy car!! AND it would be great for merging onto some expressways.
But probably not using a 48 volt battery pack. That could be handy in city traffic grid jam-ups with all start and stop driving and never over 15MPH. But we are given no clue as to the intention.
There is a fair understanding of the relation to battery capacity relative to available battery power distance, so some insight is possible.
One more detail is that adding an electric rear wheel drive to an existing front drive car will be a serious undertaking. With a whole lot of effort needed for all those many very critical details.
 

Thread Starter

shiver22

Joined Feb 1, 2024
5
I am East Indian that was born in Canada and I have had been the victim of racist comments all my life. Even from other Indians that don't like the fact I don't speak the languages.

I apologize for getting upset.

I am going to install a very small yet powerful engine that was going to be front mid engine to rear wheels however it occurred to me that installing an engine that will be fwd would be easier in some ways because alot of these are producing 300hp in very small 1.2-1.6 displacement.

I thought I can get a motor and build a direct drive axle for the rear so a high torque electric motor would drive the rear. Engines sacrifice torque to raise the horsepower so a small engine would lack the get up and go in a race.

Most motors use very high voltage at low amps instead of older ones that use low volts and much higher amps. In order to make an alternator work to power a rear motor, it would need to be converted to much higher volts that it produces now in a car. 12v to 240-380 volts would be required to power a motor that would be capable of being used in a car to get it up to a proper speed.

I thought instead of using a hybrid setup of lots of expensive heavy batteries that will only power the rear until it runs out of power then need to be shut off to charge, could it be continuously charged like lead acid can? Now I know that's possible. Thank you.

So now in order to power the rear motor it seems the only option would be to run the motor off the alternator of the car. The only way to do this that I know if is to connect the alternator to an inverter that will convert it to either 240v or 380v which would be determined by what kind of motor will be best for this setup and uses a range of volts that falls within the amount that an inverter can convert continuously. There are inverters with the speed controller built into it but they cost alot of money. Using an inverter that will power a controller that will power the motor is what I think will be more cost effective.

I did not consider that an alternator would cause more strain on the engine then it already does however I am assuming that the previous comments are saying I will need to use a much bigger alternator then the stock one in order to produce the correct amount of power required for an inverter to convert to the correct volts.

I am assuming that a higher voltage alternator, let's say 24v or if there is a 48v would be easier and more efficient then a 12v to convert. Is this true? Also would an inverter that has an input of 48v be much more expensive then a 12 or 24 volt alternator? I am even wondering if an inverter can convert enough voltage with enough amps to run the speed controller that will run the motor?

Having a high torque electric motor that could push the car is more effective at lower speeds when the gas engine is going to struggle because of the low torque. As it gets to higher speeds the electric motor will not be able to get up to higher speeds without gears. The gas engine will be able to take over for the electric motor using the higher horsepower to continue to accelerate to very fast speeds.

The main goal is to have an partnership between the engine and motor moving all 4 wheels together to give the car more traction and the partnership between one being a better fit for torque at low speeds and horsepower at high speeds should make for a very fast race car.

Having no batteries needed to drive the electric motor will save alot of weight if this can be achieved by having the alternator power converted to drive the electric motor.

If you have forgotten the questions I have asked throughout the message, can the alternator provide an inverter with enough power? Can the inverter convert the input power to enough continuous volts and amps to power the speed controller that will power the motor? What voltages can alternators provide? Will it be more efficient for a higher voltage alternator to power an inverter to convert a higher voltage like 48v instead of 12v to 240 or 380 volts? I guess I should also ask what's a good voltage and amp be for a motor for what I want to do?
 

BobTPH

Joined Jun 5, 2013
8,921
Do some calculations. At 48V, you will require 15A for each horsepower, if the motor is 100% efficient. So count in 20A for each HP.

If you want to get 50HP to the rear, you are talking about 1000A.

If I remember correctly, the Prius I used to own used 900V for the electric motor. Yes, it has a 900 inverter.
 

nsaspook

Joined Aug 27, 2009
13,231
I am East Indian that was born in Canada and I have had been the victim of racist comments all my life. Even from other Indians that don't like the fact I don't speak the languages.

I apologize for getting upset.

...
Good deal...
First, stop pulling the race card (save it for when you actually have a winning hand) when people are analyzing your self-admitted misinformed ideas about what you think is possible.
 
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MisterBill2

Joined Jan 23, 2018
18,388
OK, this is an interesting concept and would be an interesting project.
But, as has been stated already, the numbers will tell the true story. For starters, the engine power used to drive the alternator will not be available to drive the wheels. So for a quick startup, there will need to be battery power available. So there would need to be some significant battery storage. Next consider that a good motor may be 90% efficient, and a good alternator could be 90% efficient. So running the electric drive along with the gas engine is less efficient than the engine drive alone. So the added electric drive will need to be able to deliver the extra power from the batteries. So the TS needs to decide how much extra drive power is desired, and then how much electric motor power is desired, and then calculate how much battery power that will take, and for how long that power will be needed. Then calculate the cost, size, and weight of that battery pack. Those numbers will allow the TS to make a well informed choice as to how much added power will be added.
 

Ya’akov

Joined Jan 27, 2019
9,098
Hi

[1] I have a 48v lipo4 battery with a separate charging input then the wire for output (discharge).

[2] I want to connect the battery to the car to charge it when the [engine] is on and have the battery discharge to an 48v inverter … to power [an electric] R[W]D motor. I'm guessing this would cause the battery to die quickly or won't work at all.

[3] The [engine] is on all the time to use the FWD for driving so I'm wondering if I should just directly connect a 12v inverter to the controller that will control the motor for … the RWD?

[4] Maybe change it all to find a 24 volt alternator to connect a 24v inverter to 280vac? I heard the higher th volts for the alternator the better for an inverter when running it continuously. It needs a lot of volts and amps to draw from so I'm a little stumped on the best setup to [add electric] RWD in a FWD car so it would become a hybrid AWD.

[5] I want to use … [the] small[est] battery I can to save weight and money, using the car engine as a generator for the electric motor while it's driving using ICE and electric [hybrid drive].

Sorry repeating myself now.
Welcome to AAC.

I’ve edited your original post as lightly as possible first by adding paragraphs, and also by removing confusing, redundant content (indicated by …) and adding or changing things when needed for clarity (indicated by enclosure in [ ]).

Note the effect of the paragraphs which, on their own, went a very long way to making your post decodable.

Some (or possibly all) of what I will say in answer has been mentioned by others in the thread, I apologize for the any repetition this is my first chance to answer. Take or leave my contribution as suits you best.

[1] First, it’s a LiFePO₄, or LiFePO4, or LFP battery—not LiPo4. This isn’t such a big deal but you should get it right.​
As has been mentioned, batteries simply can’t charge and discharge at the same time. The charge if the conditions permit and discharge when circumstances create current flow into the battery.​
This doesn’t mean you can’t use a battery as a sort of accumulator that charges when sufficient current is present and discharges into the load when it isn’t, but the question is—why would you want to do it? What benefit do you perceive to this arrangement? What problem is it solving?​
[2] Why? Why do you want an electric motor on the rear wheels? Is it simply that you want an F/RWD vehicle and this seems to you the best way to get it? Even in the case, what is the advantage you expect from the new arrangement?​
[3] As has been mentioned, you need to do some basic, “smell test” calculations to decide it your idea—even if it does have some attractive aspects—is even practical. You have to determine how much power you will need at the rear wheels to make it useful. You have to determine if you can hope to provide that amount of power using the scheme you propose.​
Power is a product of voltage and current, and it measured in Watts. Watts are freely convertible to Horsepower. So, if you can make a reasonable estimate concerning how many HP are needed at the rear wheels you can convert that to W(atts), and then find the combination of voltage—in V(olts)—and current in A(mps) you might use to achieve that.​
You also need to work out at least a guess at the efficiency of the conversion of ICE power to electric power, and of electric power to mechanical power at the wheels. There will be loss, and you can‘t reasonably expect more than 80% efficiency (that is 20% loss) and practically it will be worse.​
[4] The calculations above will answer these sorts of questions. Always start with a test against the laws of thermodynamics, they are very hard limits. Also, always be sure you have a good reason to do something by clearly defining the problem to which the thing you hope to do is a solution.​
[5] Here you show that your requirements are a jumble of a priori guesswork and ex post facto rationalization. A clear problem definition can discipline this and give you direction when engineering a solution. Without this definition you can‘t really know if you’ve succeeded since you don’t have any particular reason for anything you are doing—save the feeling you are solving something.
So, what is the problem you are trying to solve? And no, you haven’t already described it. What you have described is a free floating “solution“ that has now become the problem—but it isn’t the problem, or at least shouldn’t be.​
Good luck with your project.​
 

MisterBill2

Joined Jan 23, 2018
18,388
I think that the TS described the anticipated problem in post #11 " so a small engine would lack the get up and go in a race. " As I see it the problem would be inadequate accelleration. Certainly the performance of an electric motor drive CAN BE impressive. BUT after watching "funny cars" and "Top Fuel" cars it becomes clear that normal driving is quite a compromise. Late in 1967 some of us went thru the math to see what could be done with an electric dragster that picked up power from heavy copper strips alongside the track, instead of on board batteries. That would allow a high power diesel generator set not carried on the car to supply huge amounts of power. And the sparking pickup brushes would be quite a show for nigh-time races. It became clear that the cost was many orders of magnitude beyond financial capabilities of the group. But it was an interesting exercise. Today it could be done much more effectively, but still very costly.
Clearly the TS was not considering a 4 second car, but certainly better performance than a low powered 18HP city car.
 

Thread Starter

shiver22

Joined Feb 1, 2024
5
Thank you for explaining this to me. I am not an engineer nor a mechanic. From what I am understanding a small engine in front wheel drive configuration will not be able to send enough power through an alternator to the motor to drive the r ar wheels while simultaneously the front engine driving the front wheels. It doesn't make sense to install huge batteries to power the rear motor then need to charge them after it is dead.

What I understood with hybrid cars the motor charged the nickel metal batteries which is why they are so small. There are new trucks that are using generators that will charge the batteries so there is no need to stop to charge them. I don't understand why they can continuously do it if you say it's not possible? The new cars are using lithium batteries not the old nickle ones. There are motorcycle cars that use 2 motors. One for front and one for back to achieve very fast times. I am not looking to beat anyone racing. I just want a fast car that is AWD and thought combining new tech with old ways I could do something different.

Thank you for setting me straight.
 

nsaspook

Joined Aug 27, 2009
13,231
There are new trucks that are using generators that will charge the batteries so there is no need to stop to charge them. I don't understand why they can continuously do it if you say it's not possible?
It's pretty simple. The ICE generator/alternator provides battery charging energy AND wheel traction energy at the same time in those types of trucks. They can walk and chew gum at the same time.
1707168944909.png
https://afdc.energy.gov/vehicles/electric_basics_phev.html
 

MisterBill2

Joined Jan 23, 2018
18,388
Understand that those batteries are not being charged at the same rate they discharge driving the car. There is a big difference there. Also, the car is normally driven by the engine, not the electric motor.
 

Ya’akov

Joined Jan 27, 2019
9,098
Thank you for explaining this to me. I am not an engineer nor a mechanic. From what I am understanding a small engine in front wheel drive configuration will not be able to send enough power through an alternator to the motor to drive the r ar wheels while simultaneously the front engine driving the front wheels. It doesn't make sense to install huge batteries to power the rear motor then need to charge them after it is dead.

What I understood with hybrid cars the motor charged the nickel metal batteries which is why they are so small. There are new trucks that are using generators that will charge the batteries so there is no need to stop to charge them. I don't understand why they can continuously do it if you say it's not possible? The new cars are using lithium batteries not the old nickle ones. There are motorcycle cars that use 2 motors. One for front and one for back to achieve very fast times. I am not looking to beat anyone racing. I just want a fast car that is AWD and thought combining new tech with old ways I could do something different.

Thank you for setting me straight.
The NiMH cells used in the classic hybrid car batteries aren’t small size for technical reasons—it‘s because the patent on larger sized prismatic cells was licensed exclusively by the USABC (US Auto Battery Consortium) which included Ford, GM, and Chrysler among others.

They claimed the NiMH battery was not ready for use in cars, but at the same time they threatened legal action against the inventor if he attempted to help any other car company use NiMH cells—even just in research. The goal, it seems, was to suppress electric cars since the only viable battery chemistry at the time was NiMH.

Toyota eventually chose to use a huge number of cylindrical cells in their batteries so they could bypass the patent on the prismatic ones.

As far as charging goes, the simplified version is that charge will flow from high potential to low potential. Ohm’s law describex the effect of resistance on current in a circuit. The motor, to be powered, must be lower resistance than the battery if they are both always in parallel with the charger.

So, the battery will be discharging into the motor unless the charger produces enough current to run the motor alone (it won’t, but) if it did, the current would flow to both in proportion to their resistances.

Since the load of the motor is going to be able to sink more current than the charger and provide, as long as the motor is running, both the charger and battery will be trying to power it.

So, the battery in this case will never charge as long as the motor is running.
 
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