Transformer sizing

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guytrinidad

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N. California
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Electrical Contractor
Good day
I'm installing a load center for
40 - 20 amp 120v breakers. Each breaker powers a charging wall for Makita battery chargers that are pulling 16 amps continuous on each breaker until the batteries are charged, then the controller draw drops as batteries are charged. So I figured a 800 amp load center, or 2 400 amp load centers, so I'm trying to size the transformer.
The primary voltage is 480/277 1200 amp switchgear, the load center needs to be a 120/208 3/phase.
I appreciate any suggestions.
Thank you.
 
Welcome to the forum.

First, round up to a quantity divisible by three, so say 42.

120v at 16a is 1.92Kva; 42 x 1.92 = 80.64Kva

Look for a delta primary/wye secondary unit.

Let us know if you have any questions about proper bonding and electrodes.
 
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In the lovely state of California, new requirements for landscape maintenance will be battery operated tools only. Makita has come up with an array of battery powered lawn maintenance tools that run off 40 W batteries. So according to my landscape contractor I'm building this for a normal crew could have. 20 batteries to get them through the day. So the charging wall will consist of an array of battery chargers that are plugged into a towa system that regulates each charger, so you can stack these towa systems Up to 32 single receptacles on a 20amp circuit and the system manages the battery packs as are charging. But it is constantly running up to 16 amps continuously until batteries are charged. And then of course, the amperage drops as the changing packs turn off..
I'd post a photo if I could figure out how to.
 
guytrinidad said:
In the lovely state of California, new requirements for landscape maintenance will be battery operated tools only.
Click to expand...
I assume you mean electric only, right? If you want to pull an extension cord around instead of using batteries, I assume you can do that.
 
guytrinidad said:
Makita has come up with an array of battery powered lawn maintenance tools that run off 40 W batteries.
Click to expand...
I assume you meant 40V…

Make sure you are not reading the OUTPUT amps of those chargers and conflating it with the INPUT amps. 16A on the 40VDC side will only be 5.4A (+ some minor losses) on the 120VAC input side…

Conversely for the 120V side of the charger to be pulling 16A, the output of the charger would have to be almost 50A! That would be a lot of heat in those batteries.

PS:
A little sleuthing and I found (not easily mind you) that the input on their DC40RA “40V Max XGT Rapid Optimum Charger” is actually 310W, so around 2.5A…
 
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A bit of specifics might be nice....
The OP does say a "charging wall" with a 16 amp load but not not say how many chargers are on a "wall".
Likewise he mentions "32 single receptacles on a 20 amp circuit" and "40 20 amp circuits"
The devil is definitely in the details.
 
guytrinidad said:
Good day
I'm installing a load center for
40 - 20 amp 120v breakers. Each breaker powers a charging wall for Makita battery chargers that are pulling 16 amps continuous on each breaker until the batteries are charged, then the controller draw drops as batteries are charged. So I figured a 800 amp load center, or 2 400 amp load centers, so I'm trying to size the transformer.
The primary voltage is 480/277 1200 amp switchgear, the load center needs to be a 120/208 3/phase.
I appreciate any suggestions.
Thank you.
Click to expand...
40 * 16 = 640 Amps = about 77 kva

Scattered across three phases 77 kva is about 215 amps so a single 400 A panel would suffice if you can find a 400 Amp panel with at least 40 spaces these days.

112.5 kva would be the standard size xfmr that would be able to supply this much current.
 
this charging wall can charge 20 small batteries and 4 large batteries as shown, you can have all chargers full with 2 batteries each and the entire wall will charge batteries in random order, dropping off chargers as the batteries are full. each Towa can take 4 chargers plugged into it and each Towa can stack with other Towas , each plugged into each Towa other up to 6 Towa units. then they all plug into a single 20 amp receptacle on a ded 20 amp circuit. so all together they will only draw up to 15.6 amps, and I did put my Fluke on it and checked the amp draw, it peaked at 15.6 amps. these walls are fora commercial landscape maintenance company, they are building 40 of these walls that will stand up vertically, so thats what I am gearing up to supply power to.
 

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I just read the posting picture guidelines, I apologize if I posted the pics incorrectly, and I have no problem if they are removed.
 
ggunn said:
I assume you mean electric only, right? If you want to pull an extension cord around instead of using batteries, I assume you can do that.
Click to expand...
these charging walls are for battery operated tools for commercial landscape maintenance company's, not for residential home use, thanks.
 
Just to verify, have you done a amp draw measurement while the charger is charging? Just to make sure it draws around 16A.

The posted spec sheet is very hard to read.
 
Ponchik said:
Just to verify, have you done a amp draw measurement while the charger is charging? Just to make sure it draws around 16A.

The posted spec sheet is very hard to read.
Click to expand...
yes, I had the 4 giant batteries on and 6 small batteries on and it was maxing out at 15.6 amps, the specs say even if all 32 batteries are in the chargers it will still stop at 16 amps, the walls they are building will have the ability to charge 20 small and 4 large batteries, thats what they need for one of their maintenance crews, they want to have 40 charge walls hooked up. yes they are a very large landscape maintenance company.
 
guytrinidad said:
yes, I had the 4 giant batteries on and 6 small batteries on and it was maxing out at 15.6 amps, the specs say even if all 32 batteries are in the chargers it will still stop at 16 amps, the walls they are building will have the ability to charge 20 small and 4 large batteries, thats what they need for one of their maintenance crews, they want to have 40 charge walls hooked up. yes they are a very large landscape maintenance company.
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So, they are just replacing one fossil fuel burning item to another one...the power plant. Makes sense to me. :(
 
Knightryder12 said:
So, they are just replacing one fossil fuel burning item to another one...the power plant. Makes sense to me. :(
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Yes, two fuel use upsides: (a) not all grid energy comes from fossil fuels and probably (b) small engine efficiency is much less than large fixed generator efficiency. So even with the electricity transmission losses and battery round trip losses, if the power plant is burning fossil fuels, likely less fuel will be required. [My comment (b) is based on EVs; I'm assuming the situation with small engines is comparable.]

Cheers, Wayne
 
guytrinidad said:
these charging walls are for battery operated tools for commercial landscape maintenance company's, not for residential home use, thanks.
Click to expand...
Right, but doesn't the ban on gas powered leaf blowers also apply to residential users?
 
I’m a little confused about this.

You’re building 40 walls, each capable of charging 32 batteries?

So this landscape company is going to have 1,280 batteries charging at once?

I don’t think all the landscape companies up here combined would use that many batteries.
 
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