Charging Tesla Battery from 24v alternator

[Wonky]

Do you think I can use a sterling charger [ https://sterling-power.com/collecti...battery-chargers-up-to-400a?variant=878104907 ] to charge my Tesla Model S battery module, 24V, 250Ah,5.2kWh from an 24v alternator ? (The alternator is really a bank of 4 alternators that are load sharing and have a total output of up to 560 Amps.)

the sterling charger has a setting for LiFePO4, is that close enough?

Any other DC to DC chargers that will do the job?

Thanks

 

[Geriakt]

No. Charging for Lifepo at 24 volts us based on a 8s battery at a max of 28.8 volts way too high for Tesla. The Tesla is 6s and your max charge is 25.2 volts.

The Victron 24 to 24 Orion TR smart charge or the Victron Buck Boost dc to dc charger would be a better choice as they are both programmable. What are you using for a BMS on your Tesla?

 

[Wonky]

No. Charging for Lifepo at 24 volts us based on a 8s battery at a max of 28.8 volts way too high for Tesla. The Tesla is 6s and your max charge is 25.2 volts.

The Victron 24 to 24 Orion TR smart charge or the Victron Buck Boost dc to dc charger would be a better choice as they are both programmable. What are you using for a BMS on your Tesla?

OK, thanks for the input, I just learned what an S number is thanks to you. So these tesla batteries have 6 cells in series and thats why the lower voltage/charge profile. Good to know.

The Victron Buck Boost seems so expensive ( $1100 / 50A ) where the Sterling was more like $900 / 200A.

The Orion TR looks like $263 / 17A that's over $3000 to get back to 200A capacity, if they can be paralleled.

Let's say I have two of these tesla battery's, how many amps do I need to charge them in say 8 hours?

I was hoping to just tie an 2000w inverter to the tesla battery and leave them hard wired to each other all the time. (with protection of course) This would mean when I start the alternators, the load of the inverter ( 1200w max so maybe 45amps at 28v ) plus the charging current for the tesla battery would have to go through the dc-dc unit. Thoughts? Would I be better off to use contactors and just move the inverter from the battery to the alternator when the engine starts?

About the BMS, I have no experiance or idea yet, this is an adventure in engineering for me. I have a background in EE and have come a long way, but all things lithium are new to me. I also have more time than money and an awesome workshop, so diy fabrication is better than spending big money for my projects.

 

[Geriakt]

My system is 2 tesla 5.3kwatt hour modules in parallel. I use a Victron Multiplus 24/3000 and i charge at 60 amps to both modules or about 1400 watts through the Multiplus. I have 1100 watts of solar. I have my RV house Tesla system isolated from my sprinter cab. I may get a Victron 12 to 24 Orion TR Smart that can charge at 15 amps or about 380 watts, but i am not sure i need it as i have a generator as a back up to charge. I have a 220 amp alternator but MB limits the Alternator to 40 amps charging only. Yes you can install 2 Orions to charge at 30 amps nearing the limit of the alternator.
I am using 2 Electrodacus SBMS0 for my BMS system. They are fully programmable and works with the Victron equipment.

 

[Geriakt]

My thoughts on the Serling is i dont think it has the option for custom profile programming to match the teslas chemistry.

 

[Wonky]

My system is 2 tesla 5.3kwatt hour modules in parallel. I use a Victron Multiplus 24/3000 and i charge at 60 amps to both modules or about 1400 watts through the Multiplus.

How long does it take to charge the two modules for example from 20% up to 80% at that rate?

 

[Wonky]

** I think I found a dc dc charger **

I am looking at the Conext MPPT 60 150Solar Charge Controller. It is marketed for PV to battery charging, but in the manual under features it says it "will also work with other DC sources." It can be paralleled for more current.

The menus allow for the following settings:

MPPT disable (then you tell it what voltage to expect from the source, in my case 28v )
Equalization disable
Bulk voltage
Absorption voltage
Float voltage ( also float disable )
Charge current limit

and much, much more.

And at $550 / 60A, it seems like a fair deal especially given that it is the only unit I've found that fills the bill.

I am still not clear on how many amps I should set the charge limit at for these tesla batteries. Any one have any data on this?

 

[Geriakt]

** I think I found a dc dc charger **

I am looking at the Conext MPPT 60 150Solar Charge Controller. It is marketed for PV to battery charging, but in the manual under features it says it "will also work with other DC sources." It can be paralleled for more current.

The menus allow for the following settings:

MPPT disable (then you tell it what voltage to expect from the source, in my case 28v )
Equalization disable
Bulk voltage
Absorption voltage
Float voltage ( also float disable )
Charge current limit

and much, much more.

And at $550 / 60A, it seems like a fair deal especially given that it is the only unit I've found that fills the bill.

I am still not clear on how many amps I should set the charge limit at for these tesla batteries. Any one have any data on this?

teslas can take a lot of amps. Like i said mine are charging at bulk at 60 amps. They can take everything your alternator can provide. Now what your alternator can provide without catching on fire is another story. Charging the tesla at anything greater than 25.2 volts will result in disaster for you and your vehicle. Dont buy on the lowest bidder, purchase on what fits the bill.

 

[Geriakt]

How long does it take to charge the two modules for example from 20% up to 80% at that rate?

Lets do the math. 5,300 watt hours each. 2x 10.6KWhours /1400 watts = 7.6 hours. I am only using about 8KW hours so it would take 5.7 hours to charge at 1400 watts (about 60 amps)

 

[SteveCA]

When looking at DC to DC chargers, be sure to check the output amperage. I just learned that some units list the amps but it means maximum amps on either the input or output.

 

[freds]

I have been testing out my Tesla setup that includes Victron solar charge controllers and wanted to test it without solar panels. I had a bunch of cheap 24V power supplies laying around which I could turn up to 27.5 volts.

The solar charge controller would overload them right away. The solution was to bring up the app and turn down the charge rate for the controller.

My current thinking is that since my bus has 350 amp alternator; that I would have a raspberry pi monitor the system and if I am in motion, switch the charge controller input from the solar panels to the vehicles 24 volt (actually 27-28 when the alternator is online) system; if it can get more power that way.

That way I simply reuse the solar charge controller that is already there and you avoid all the complications of not having a normal vehicle battery in the circuit for the alternator. Just need a relay to do the switching....

 

[borednerds]

** I think I found a dc dc charger **

I am looking at the Conext MPPT 60 150Solar Charge Controller. It is marketed for PV to battery charging, but in the manual under features it says it "will also work with other DC sources." It can be paralleled for more current.

The menus allow for the following settings:

MPPT disable (then you tell it what voltage to expect from the source, in my case 28v )
Equalization disable
Bulk voltage
Absorption voltage
Float voltage ( also float disable )
Charge current limit

and much, much more.

And at $550 / 60A, it seems like a fair deal especially given that it is the only unit I've found that fills the bill.

I am still not clear on how many amps I should set the charge limit at for these tesla batteries. Any one have any data on this?

@Wonky did you ever try this? How did it go?