Battery Charging Question

[WhyZed]

I have found a pretty big (8"x8"x8") 1500VA transformer that should give me ~ 65VAC off the secondary windings with a 220VAC primary. After I rectify this, I think I'd be looking at ~90VDC and how many amps ~25??? Charger controller 140vdc & 3600wats max. This should be a bit low but descent load on a 10kw genset?
Put this input into the charge controller and on a 24V string, the controller should give out the 60amp max of the XW-MPPT60-150.
If the battery string is charged at 48V, would I get about 60amps still???

The battery manufacture recommends the 415AH batteries should be charged @
75amps for 250 minutes/4hrs
25amps for 940 minutes/15.5hrs.

Would this transformer and rectifier setup have the power to fully charge these batteries?
Would this transformer and rectifier setup have the power to equalize?

I was hoping to be able to charge these up as quick as possible and not have to run a generator for 16hrs/charge (if math is correct).

It's been so long since I've worked in ohms law and I'd truly appreciate some help before I take this project on.. Am I even heading in the right direction?

What do you guys use to charge up your big strings?

Thanks,
Zed

[Mike90250]

It's a maybe. Just because your transformer is labeled 1500VA, does not mean you can get the voltages you are talking about. There is a spec plate on it, or in the paper work, that says what the voltage and load capabilities are. You can't guess or wish it to be anything else. If you overload it, you smoke it.
Generally, any center tap full wave bridge rectifier will loose a bit of voltage, as you load it heavier. Your power factor will likely not be good, maybe .7

What will regulate the charge to the battery? A switch and voltmeter ? you really need a way to accomplish 3 stage charging.

The XW-MPPT60-150 can handle 60A @ 24v or 48V. At 48V, the 60A will be 2x the power of 24V, so that's a better deal.

[WhyZed]

Thanks for the reply Mike,

Yes agreed, the XW-MPPT60-150 can handle 60A max and 140vdc max, whether @ 24v or 48V out. So 48v would be best indeed BUT, I'm finding more load options (motors/pumps/lighting etc) that run on 12 & 24VDC than 48vdc (including inverters). I guess there might be some constant fiddling to charge at 48 and run 24V things...

With a togel switch between the genset DC charger/solar panels, and the XW-MPPT60-150, the DC input source could be switched manually and the XW-MPPT60-150 used to control the battery charging (charge controller). The user manual for the XW-MPPT60-150 indicates that the equalize charge state can be manually initiated through programming and possibly (must reread) programmable to do so automatically, so I've got that going for me (quote caddy shack).

The transformer's label reads; 1500va
480v primary 120 secondary (diagram - only 4 terminals).
So if I apply 240v primary I should get ~60vrms secondary.

60vac divided by .707 for peak to peak DC = 85vdc - 1.4v (loss for 2 diodes, positive side of bridge rectifier) to give me ~ 83.6VDC.

So how many amps can a 1500va transformer produce at 60vac given the load about to be introduced? How many watts can this 1500va transformer produce total?
I did a quick google search and that question raised more questions than it answered for me..

[Sunking]

The transformer's label reads; 1500va
480v primary 120 secondary (diagram - only 4 terminals).
So if I apply 240v primary I should get ~60vrms secondary.

60vac divided by .707 for peak to peak DC = 85vdc - 1.4v (loss for 2 diodes, positive side of bridge rectifier) to give me ~ 83.6VDC.

So how many amps can a 1500va transformer produce at 60vac given the load about to be introduced? How many watts can this 1500va transformer produce total?
I did a quick google search and that question raised more questions than it answered for me..

It does not work that way. 85 VDC would be peak. The actual Average DC Voltage is going to depend on what type of rectifier you use. So with 60 VAC RMS the DC output will be between 27 volts and 54 volts. Here is a good reference document that should help. However that is the output of the rectifier and does not account for voltage and current regulator voltage losses.

Second problem is your transformer is rated 1500 VA at specified input voltage. The limiting factor is the input winding wire size. So at 480 volts and 1500 VA the maximum input current is 1500 VA / 480 V = 3.125 amps. So the max input current is 3.25 amps. You are correct if you input 240 volts on the primary, the output voltage will be 60 VAC RMS, but by doing so you just cut the VA down to 240 VAC x 3.125 amps = 750 VA. Gotcha! That means 60 volts at 12.5 amps max output.

[WhyZed]

Thanks Sunking, I'll read up on the link and thanks so much for the info on the transformer. I used to have a couple massive hi current transformers kicking around that I could have played with here, & I know they would have worked get but out they went when wifey needed more room for shoes.

Still need DC hi current source, looking, looking, any recommendations?

[Sunking]

Still need DC hi current source, looking, looking, any recommendations?

Yeah look around on the web for a used or salvage Telephone Batery Plant rectifier. That is what i use on my golf cart. Look for names like Lorain Reltek, Marconi, Peco, Lucent, Delta.There are a lot of manufactures out there and a lot of old transformer-SCR rectifiers out there since most Telco's use Switch Mode rectifiers now days. Especially the wireless carriers will dump them from time-to-time.

YOu should be able to find a battery plant rectifier for cheap like $20 to $50 up to 100 amps. Just besure it is not a 480 volt model which should not be a problem with a 100 amp or less rectifier. If you can find one they last forever as they are heavy duty industrial grade designed to run at 110% current rating 100% duty cycle. Not to mention dead accurate control circuits.