Using power converter

[jangles]

Is it possible to use a power converter in my truck to charge my 52v battery while running down the highway ? If so how big of a converter would I need to run my 58.8v 3.0 charger ? TIA .

PS: This is my Ebike 52v 6ah mini 30 q from Luna that I am wanting to charge .

 

[flippy]

Just grab a swi power true sine wave inverter from aliexpress. Cheap and you can get them up to 5kW. But in your case a 1000W model is plenty and allows you to run everything you can think of that needs less then 1000W directly from your truck.
Just make sure you get a true sine wave and nothing "hybrid" or "modified".

 

[dogman dan]

Theoretically, a 300 watt inverter would be sufficient. But running such things at near full power continuously gets iffy. I would think though, that a 500w one would be sufficient.

But pulling your chargers current of 250w or so, its not going to happen through the cigarette lighter on the dash. You will have to run some hefty wire directly to the battery. I did something like this on my van, I used a three strand 12 gage extension cord to tap the positive wire on the battery, and run it to the back of the van where I put a second battery. All three wires on the cord carried the positive, making it equal to a big thick wire. The negative is simple, bolted that short thick wire to the seatbelt bolt to ground it all.

Then with that in place, I could run the inverter, my chargers, a tv, etc. While moving I could charge. Stationary I kept the DC coming with the tiny harbor freight generator powering a 12v charger.


Your car is not going to like putting out 1000w for long, that's much more than the car is designed to do continuously. But if your needs are 500w, then a small generator can do that much all day, and while moving, your car can put out 300w no sweat.

 

[flippy]

Your average 120A alternator can deliver 1000W no problem.

I got a 5kW inverter in my transit and a big battery and when i exeed the capacity of the alternator i use the battery of when the engine is off. The alternator catches up once the load is reduced and recharges the battery.

Alternators will suplly their full current all day no problem.

 

[john61ct]

how big of a converter would I need to run my 58.8v 3.0A charger

Well that's well under 200W, just by multiplying.

Usually "converter" to me means DC-DC, just boosting voltage not going from DC to AC back to DC again.

Did you mean that, specifically?

Just out of curiosity, could you link to that charger?

And ideally to the bank being charged, its chemistry and Ah capacity could make a big difference.

 

[john61ct]

Alternators will suplly their full current all day no problem.

That is so laughably false, in many ways.

I have seen many dozens of setups where the stock alt got burnt out when the target deep-cycling bank Ah capacity was increased and/or the chemistry changed.

A whole industry segment of expensive external VRs and DCDC chargers (converters) exist for that very reason.

Many modern vehicles designed to maximize fuel efficiency, and many older ones that react to over-current (over temp actually) by dropping voltage, in effect just can't charge such a bank without a DCDC unit, even if driven 12 hours straight.

In fact only very rare stock alternators can put out their rated current for more than a few minutes at a time.

I guess we live in different worlds.

 

[flippy]

Alternators will suplly their full current all day no problem.

That is so laughably false, in many ways.
I have seen many dozens of setups where the stock alt got burnt out when the target deep-cycling bank Ah capacity was increased and/or the chemistry changed.
A whole industry segment of expensive external VRs and DCDC chargers (converters) exist for that very reason.
Many modern vehicles designed to maximize fuel efficiency, and many older ones that react to over-current (over temp actually) by dropping voltage, in effect just can't charge such a bank without a DCDC unit, even if driven 12 hours straight.
In fact only very rare stock alternators can put out their rated current for more than a few minutes at a time.
I guess we live in different worlds.

i live in a world with european cars where there is plenty of cooling for the alternator and a alternator that burns out due to "overloading" basically does not happen. it does happen that the diode brige burns out on older cars but that is usually because of age and heat cycles, not actual power draw.

dont blame me for shitty american cars. there is a reason they are so cheap compaired to their european counterparts...

FIY: i worked in the millitary on hunderds of cars and trucks and most alternators only ever needed new bearings and sometimes a new bridge, i never seen one that was burned out due to overcurrent. only one had the windings burned out and that was because some dipshit smashed a screwdriver into the windings with a hammer.

tell me the difference between having a generator and a alternator in a car? they both do exactly the same thing (apart from a different voltage) or is somehow a generator-alternator magic?

pro tip: if your alternator craps out then it might be a indication you need a better one.

 

[jangles]

Well thanks , I think . Most of this info is wayyy over my head . I just want to charge my Luna mini 30q while I'm driving down the road .
So I multiply amps x volts to get the wattage needed with a sine wave invertor ? Like this one ?
https://www.harborfreight.com/750-watt-continuous-1500-watt-peak-power-inverter-66817.html

TIA

 

[john61ct]

Yes many well-engineered cars do not allow over-current demands to build up too much heat.

Yes European cars historically have been better engineered than (what used to be) US companies.

Yes military alternators are among the rare exceptional ones that are conservatively rated and robust enough to put out their full rated current continuously.

However none of those facts make this

Alternators will supply their full current all day no problem.

any more true.

Best that can be said, it's a gross over-generalization.

Key takeaway with a large LFP bank is, even if **your** stock setup prevents burning out the alt / diodes,

**how** does your alt respond to over-current demand? If it drops voltage, that may be stopping any effective charging.

For vehicles / boats systems that allow conversion to an external VR, Balmar's MC-614 is a solid choice.

Mark Grasser makes solid products if you're looking to replace the full alt setup.

Some drivetrains can support the very large alts from ex-military and emergency vehicle setups, 3kW up to 15kW if needed, but that latter range will take too many HP away from propulsion in most rigs, so need at least a Field circuit kill switch, "live" de-rating controls are very rare.

Rather than derailing this specific thread further (sorry OP), let's start a new thread to get into the specific details of the issues and how to solve them, if anyone thinks that would be interesting.

 

[john61ct]

So I multiply amps x volts to get the wattage needed with a sine wave invertor ?

Yes, but note that cheap inverters can grossly overestimate their actual output, so build in headroom, in this case I'd say one marketed as 500-1000W unit.

Also, you really should get a **pure** sine-wave unit, even if you don't want to pay for a known-good quality brand of inverter.

FYI, if you were concerned about energy efficiency,

say off grid with solar panels providing the energy rather than "free" energy from an alternator,

I'd investigate a DCDC converter or charger.

Overkill both in cost and complexity,

and yes that side discussion about alternators is also not relevant

in this scenario.

PS link to your charger?

 

[jangles]

So I multiply amps x volts to get the wattage needed with a sine wave invertor ?

Yes, but note that cheap inverters can grossly overestimate their actual output, so build in headroom, in this case I'd say one marketed as 500-1000W unit.

Also, you really should get a **pure** sine-wave unit, even if you don't want to pay for a known-good quality brand of inverter.

FYI, if you were concerned about energy efficiency,

say off grid with solar panels providing the energy rather than "free" energy from an alternator,

I'd investigate a DCDC converter or charger.

Overkill both in cost and complexity,

and yes that side discussion about alternators is also not relevant

in this scenario.

PS link to your charger?

Here is a link . Thank you .
https://www.ebay.com/itm/58-8V-14S-3A-Lithium-Battery-Charger-for-52V-Li-ion-Ebike-XT60-Connector-110v/273499022857?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

 

[flippy]

i volt modded a bunch of those in the past year.
they are not great in the efficiency department as they are made with a large voltage range in mind.

in order not to blow up the input stage you would need a true sinewave. anything less will kill it.


or what you can do is get this:

https://www.ebay.com/itm/DC-DC-10-12-15-20A-150-250-300-400-1200W-Step-up-Step-down-Buck-Boost-Converter/222634543946

put the 1200W version in a case with a fan, set it to 58.8V and 2~3A, put on the proper connector and then you have a 58.8V charger.

 

[john61ct]

But of course it has no stop-charge intelligence.

Does the charger you linked to, OP? (and thanks)

Without that, you'd want to be paying attention to V/A act as regulator yourself.

Probably not ideal if you're the driver. . .

 

[flippy]

But of course it has no stop-charge intelligence.

Please elaborate on this?

I think you have been reading too much marketing wank....

 

[jangles]

But of course it has no stop-charge intelligence.

Does the charger you linked to, OP? (and thanks)

Without that, you'd want to be paying attention to V/A act as regulator yourself.

Probably not ideal if you're the driver. . .

If you mean does it stop charging when the battery is full I dont know . After I read that I went to ebay and opened a return ticket since I can have a Luna smart charger with 80 , 90 and 100 percent for the same money . Seller states he doesnt take returns I'll buy a Luna anyway .

 

[flippy]

so yes, you have been litening to too much marketing wank.

charger is not the right word to be used. the things we use to charge a battery is a constant current / constant voltage source.
the only thing it does is deliver a certain voltage and limits itself to a certain current. nothing more or less.
and its basically the same as inflating a tire with a regulated air hose. you set the air hose to 1 bar then the tire inflates as fast as the hose allows air to pass until the set pressure is reached, at that point nothing happens anymore. its the same with batteries. once the voltage in the battery has reached the voltage set in the charger the whole thing stops naturally. there is no "smart" or " intelligent" wank going on. its just a matter of setting the proper voltage and current.

so, the CC/CV boost converter i linked to will charge ANY battery within its voltage spec, the only thing you have to do is set the proper voltage.

if you want less charge then you set the voltage lower. not that hard of a concept. and that is why paying out the anus for a "smart" charger is just dumb. what do you think a luna is? just a cheap ass chinese aliexpress charger with a pot to set the voltage on the outside instead of the inside and with a 3 dollar aliexpress voltage/current meter hacked into the top plate.

 

[jangles]

Flippy , you're killing me with all this info , I don't understand it . Please stop or tame it down . I'm sure you're a very nice and well meaning person but you're just confusing me . TIA . :thumb:

 

[john61ct]

Most devices sold as chargers do not "just stop" when the battery (if not a 4-wire charger, usually the circuit between battery and charger) reaches the voltage setpoint.

If it does, there is no CV / Absorb stage going on at all, and depending on the charge current C-rate, the bank may be seriously undercharged rather than getting to 100% Full SoC.

Those chargers that **do** hold Absorb voltage for a time (AHT) must have some mechanism to determine **how long** they will do so, IOW when they stop charging, drop to Float V, whatever. There are many different algorithms in use, and usually they determine a lot of how "smart" a charger with "stages" is judged to be.

Anyway, my point is, a plain raw PSU does none of this. It just puts out voltage forever until you turn it off. With a battery at low SoC, there will be a CC (Bulk) stage while the PSU "strives" to reach the (Absorb) setpoint.

What the % SoC is when that CC-CV transition takes place, and how long it takes is determined by batt chemistry, CAR and C-rate of the charge current, it is not determined by any regulator intelligence.

Maybe that last was what floopy meant to say with that marketing comment.

There are disagreements about how many lifetime cycles are lost by continuing to try to push current into a bank once it's reached 100% SoC, or even to the point that resistance is so high that trailing amps have dropped to zero.

Probably does not make much practical difference for batteries already being used for propulsion at high C-rates.

But I for those striving for maximum longevity, I would most would want to terminate charging before current drops to say .01C.

 

[flippy]

how does a standard lipo cell gets overcharged if the charger is set to 4.2V? once the cell is at 4.2V and saturated the current is zero.
that stiuation is not controlled by the charger but because the cell wont absorb any more unless you increase the voltage at wich point you start killing the cells.

so there is no "stopping", that only happens with SLA batteries that have a difference between charge and float voltages. we are talking about lipo that does not have a difference between charge and float voltages, they are one and the same.

the "red/green" led on a charger does not measure capacity or some dumb thing, it only measures the current and if the current is below the treshold the light goes from red to green. almost no lipo charger actually deliberatly cuts off the actual power flow and allows the battery to continue to charge until the cells are balanced (if you have a bms balancing the cells) or until the cells are fully satuarated, but that can take many hours.
gnerally i recommend not doing this but stop at 4.1V instead of 4.2V just to increase the lifespan of the cells, that way you can keep it on the charger without it killing the cells because you keep them at 100% soc all the time.

for the record: bulk chargers dont "strive" for anything, they just deliver as much amps as is set until the voltage is reached and then naturally the current starts tapering off. that is not something the charger activly does, it just happens because the voltage that is set has been reached. just at that point the charge rate lowers because the amps are going down.

this is why you dont need a expensive ass charger, just a simple converter that does CC/CV is enough like the one i linked above. the rest of any "features" is just dressing designed to take your money.

 

[jangles]

Jeezuz kryst , will you two get off my thread . My question still hasn't been answered and with you guys arguing back and forth it never will be .

 

[john61ct]

Sorry I thought you had all the information you needed. The further nitpick discussions are not so relevant to your use case.

Yes you can use a DC-DC boost converter.

Yes you can use a properly sized **PSW** inverter + whatever AC-DC charger or PSU you'd use at home.

If you need further clarification, please ask specific questions.

 

[jangles]

Okay , which of the inverters in the link will allow me to hook to the 12 volt battery's in my 5th wheel and run my 58.8v 3.0 charger to charge my 52v 30amp 6ahr battery ? I don't need one to do anything else . TIA .
https://www.harborfreight.com/catalogsearch/result/index/?dir=asc&order=EAScore%2Cf%2CEAFeatured+Weight%2Cf%2CSale+Rank%2Cf&q=inverter

 

[flippy]

Okay , which of the inverters in the link will allow me to hook to the 12 volt battery's in my 5th wheel and run my 58.8v 3.0 charger to charge my 52v 30amp 6ahr battery ? I don't need one to do anything else . TIA .
https://www.harborfreight.com/catalogsearch/result/index/?dir=asc&order=EAScore%2Cf%2CEAFeatured+Weight%2Cf%2CSale+Rank%2Cf&q=inverter

None of them. They are all crap hybrid modified sinewave. as i mentioned before those cannot be used. If you took the time to read the posts where this is mentioned you would catch that.

https://www.aliexpress.com/item/power-inverter-1000W-pure-sine-wave-inverter/32689206395.html

They also sell a version with a charger built in so it can charge your car battery when you feed it ac.

 

[dogman dan]

Well, I was thinking only about If your car alternator did not like the extra pull for hours and hours, And, you really pulled 1000w, and how hard it might be to pull that alternator.

You wont pull 1000w, with a typical charger. 5 amps ones only put out 250w. Yours will put out only 150w.


But now that I see its for your RV,, I would say get a good quality sine wave inverter, perhaps 2000w. Then you could briefly use the microwave without running a generator. And solar on the roof to keep that house battery full while moving. 100w panel at least.

 

[john61ct]

Mass market big box is not IMO where to buy a decent inverter, you'll just get cheap Chinese crap.

From a known good respected quality brand a 300-400W will not be too expensive.

Xantrex is good but terrible CS attitude. Magnum is the best, Vanner, Victron, MasterVolt, Sterling, Outback, ProMariner but pricey. Samlex and Tripplite solid middle ground. I've heard Morningstar is good.

But if you do go cheaper, then should size for a higher rating.