Food Truck 24v System Design

[Wonky]

Hello All,

I am building my dream: an mobile espresso hot chocolate shop. I have the bus with new engine and transmission. I have the italian espresso machines and american chocolate melters. Now I need a robust power system to run the food equipment. That Is what this conversation is about. 24V food truck Power System

A quick rundown of the power system components already chosen:

APU SECTION: 9kW NOMINAL
4 x 140amp 24volt Alternators ( prestolite BLP 3312 MultiPower--all 4 alternator are common regulated load sharing with the prestolite Multipower system)
1 x Kubota D722 three cylinder diesel engine (14kW peak output power, hoping to run around 2000rpm to yeild up to 9kW output)
This will yield up to 400Amp 28V continuous power! that is 11,200 watts. I will call this 9kW nominal APU

24V RAIL / CIRCUIT BREAKER PANEL SECTION
1 x Alpha Technologies 020-671-20 Rear Access Bullet Breaker Panel 23" 600 A
N x various Airpax Sensata CMLHP dc rated circuit breakers
N x 4/0 and 2/0 copper cables ( spare no expense on cables! )



INVERTER SECTION
1 x Samlex S-2024A ( 24vdc in 120vac out 2000W pure sine inverter/charger) --powers 120vac loads
1 x Aims Power PE300024230S ( 24vdc in 230vac out 3000W pure sine inverter ) --powers sensitive 230vac loads
1 x Aims Power PUK500024230W ( 24vdc in 230vac out 5000W modified sine inverter ) --powers resistive heating element 230vac loads
The samlex is already onboard and working fine, so no reason to get rid of it. The Aims units are chosen for the cheap price. With the price of the Aims inverters, I can afford to keep spare inverters on hand, which is very desirable.

======================================================================

now for the fun part: choosing the batterys and DC to DC battery charger for the lithium batteries

BATTERY SECTION
starting battery
2 x Motorcraft BH31XT (wired in series to provide 24v starting and a "cushion" for the alternators and inverters to ride on. )

deep cycle battery
2 x Tesla Model S battery module, 24V, 250Ah,5.2kWh (to provide deep cycle service for the truck when parked)

DC TO DC BATTERY CHARGER SECTION

????????????

I don't have a clue! Charging the lithium battery seems like a big chore! HELP ME ON THIS ISSUE??? please?

This system has the following two states:

APU engine running:
400A 24vdc ( 9600W ) continuous power source
up to 5000W continuous inverter loads ( up to 6000W peak inverter loads )
up to ????? W load to charge Lithium batteries. --can somebody help me with the maths here?

APU engine off:
lead acid battery disconnected, (reserved for starting) (yes this is about 10 or 20 times overkill for a baby diesel engine--it is sized to cushion the alternators )
lithium Battery supplying power
up to 1200W 120vac inverter loads (power to refrigeration and chocolate melters)
all 230vac inverters shut down.
up to 200W lighting loads

future upgrades:

shore power charger input
solar array capable of running refrigeration and holding batteries charge.

 

[John Frum]

Have you considered getting a 230VAC@50hz diesel generator?
They run at 1500 rpm.
charge the bank with ac to dc chargers

 

[John Frum]

Also why not 48 volts?
Does the transmission have a PTO provision?

 

[Wonky]

Have you considered getting a 230VAC@50hz diesel generator?
They run at 1500 rpm.
charge the bank with ac to dc chargers

smoothJoey, decisions were made, a major factor was the air conditioner/ hvac system, which uses belt drive compressors off the APU. I already have the prestolite units.

Why not 48V? the aircon, bus chassis, motive power starter (cummins) and samlex inverter were already onboard at 24v, and the prestolite alteranators were sourced used at a real bargain. So that's where we are at--24V

PTO of allison transmisson is not desirable because I want to shut down the noisy cummins and run the smaller, quieter kubota for 8 to 12 hours a day.

 

[John Frum]

smoothJoey, decisions were made<snip>

Cool bus btw.
I would buy an espresso from you.

 

[FilterGuy]

APU engine off:
lead acid battery disconnected, (reserved for starting) (yes this is about 10 or 20 times overkill for a baby diesel engine--it is sized to cushion the alternators )
lithium Battery supplying power
up to 1200W 120vac inverter loads (power to refrigeration and chocolate melters)
all 230vac inverters shut down.
up to 200W lighting loads

How long do you need to operate on batteries? Assuming you can get everything out of the tesla modules, you will get about 3.5 Hours if you are running 1400 watts continuous. However, I assume the refrigeration, and chocolate melters are intermittent loads. You may want to do some measurements on the equipment so you will know if the design meets your needs.

Also, the Tesla modules tend to have a lower voltage range than a lot of inverter equipment is designed for. You may find your samlex sounds an alarm and then shuts down before you have fully discharged the Tesla Modules.

 

[Wonky]

How long do you need to operate on batteries? Assuming you can get everything out of the tesla modules, you will get about 3.5 Hours if you are running 1400 watts continuous. However, I assume the refrigeration, and chocolate melters are intermittent loads. You may want to do some measurements on the equipment so you will know if the design meets your needs.

Also, the Tesla modules tend to have a lower voltage range than a lot of inverter equipment is designed for. You may find your samlex sounds an alarm and then shuts down before you have fully discharged the Tesla Modules.

Right now, I have one beverage air undercounter fridge ( ucr34 ) at about 500W and one melter at 500W, but both have a duty cycle below 50%. I want to have a provision to automatically start the APU and charge the battery when the inverter cuts out from low voltage. I assume deep discarge is bad for the tesla battery, so I don't mind not using the bottom 30%--is that correct?

 

[FilterGuy]

Right now, I have one beverage air undercounter fridge ( ucr34 ) at about 500W and one melter at 500W, but both have a duty cycle below 50%.

Is 500W a measured value or is it off the name-plates? (Name-plate is always higher than actual)
Lets say it averages 500W continuous. Assuming you leave 30% in the battery
.7 * 5.2KWh / .5Kw = 7.3 hrs from a full charge,

I assume deep discharge is bad for the Tesla battery, so I don't mind not using the bottom 30%--is that correct?

Like any battery, if you don't take it all of the way down it will last longer. However the Tesla Li-ion cell can handle full discharge reasonably well.

 

[Wonky]

Is 500W a measured value or is it off the name-plates? (Name-plate is always higher than actual)
Lets say it averages 500W continuous. Assuming you leave 30% in the battery
.7 * 5.2KWh / .5Kw = 7.3 hrs from a full charge,


Like any battery, if you don't take it all of the way down it will last longer. However the Tesla Li-ion cell can handle full discharge reasonably well.

500 watts is from the spec sheet which says 4 amps 115v full load amps. So yeah, probably more like 2.5 or 3 running amps.

Also, I have room for 2 tesla batteries, that makes 10.4 kWh. I'm not worried about how long it lasts on batteries, just that I can shut down all the engines and not have any milk or food spoil. If the rig burns a gallon or two of diesel a day to keep the fridges cold, thats ok. Also, shore power with transfer switches will keep everything fresh at many parking spots.

What I am really needing help with is the dc-dc charging, that is current limiting to keep the low resistance of the lithium from eating all the alternator amps etc.

 

[FilterGuy]

Take a look at this:
https://redarcelectronics.com/products/24v-20a-in-vehicle-dc-battery-charger

It says it will handle AGM so it *might* work for your tesla modules.... be sure to check.

At 20 Amp it will take quite a while (>20Hr) to charge two tesla modules form empty to full.... I don't know if you can parallel a couple of them to get better amperage.

Take a look at these as well.... but look close at the output voltages.
https://www.powerstream.com/dc-input-charger-24-24v.htm

 

[kernel]

Renogy has a 60a 12-48v dc to dc charger that will charge lithium. Rover 60.

Not sure if they make a larger one, you are pretty much a 100A and up kinda situation.... power hungy at least.

You could possibly parallel battery to battery chargers, but it could get wonky.

Shouldnt be a problem to get what you are after. The dc to dc charger is a nice trick, but you may need something in a size im sure is made, but ive never seen.

Justin may have. Big boats. Military surplus units have to be available.

Kinda fun.

 

[John Frum]

@Wonky How are things progressing?