24v battery bank charger q's

[birdhouse]

hello-
i've got a 24v battery bank as part of my renewable energy set-up at my ranch.  the bank is about 450Ah @ 24v.  there are times in the winter when the solar and wind just don't keep up with the use. 

i also use a honda eu-1000 to power up a 32' airstream trailer.  that will slowly be put on the RE system, as bulbs get changed out ect. 

so i was looking on ebay at 24v chargers, and anything ove 3-4 amps starts getting really expensive.  so, then i found these chargers designed for Mac laptops.  at $9.65 for 2.6 amps, they're the cheapest "dollar per amp".   idea being, buy maybe 6 of these chargers and wire them up all in parallel.  so 6 would give a 15+ amp charger that could be plugged into the eu-1000. 

would this work?  any ideas?

is it easy to make a "dumb" 24v charger?  i've got a ts-60 in dump mode, so it could be the "smarts" for the dumb charger. 

thanks!
adam

specs for laptop charger:
Features:
1.Input: 100--240V, 50-60Hz
2.Output: 24V 2.65A
3.Power: 65 Watt
4.Smart device surge protection for over voltage, temperature and short-circuit protection
5.7.5*2.5mm

Specifications
Package include:1*APPLE G4 PowerBook 15" 17"  AC adapter

Compatible with
G3/G4 all Snow/White Apple iBook 500 mhz+ Apple iBook 12-inch Dual USB
Apple iBook Late 2001 Model
Apple iBook G4 14.1-inch M9165B/A
Apple iBook G4 14.1-inch M9165CH/A
Apple iBook G4 14.1-inch M9165J/A 

[97fishmt]

Hey birdhouse,

It's time to build a lawnmower generator out of your Fanuc motor.

You can use the C-60 for regulation but you still have to keep an eye
on it.

You'll be happier with a better motor for the turbine when you find
it anyway. 

Or find a 24 volt alternator,  I use a 48 volt  G.E. out of a dozer, got
it for $50. 

The servo's for 24 volt charging are getting harder to get a deal on
or I'd make a trip down to see ya. 

Mike

[birdhouse]

mike-
yea, that'll be a long term solution.  i "think" i've got a free 3.5hp briggs to play with.  i think semi alternators are all 24v...

at this point though, a possible $60 for a 15 amp charger sounds like the go for me!


adam

[oztules]

The cheapest most useful devices I have found for the money are these things.

http://www.ebay.com.au/itm/New-24V-15A-360W-Switch-Power-200-240V-Supply-Driver-LED-Strip-light-Display-/120799021110?pt=AU_B_I_Electrical_Test_Equipment&hash=item1c202ec836

http://www.ebay.com.au/itm/350W-24V-14-6A-Regulated-Switching-Power-Supply-/170607332827?pt=LH_DefaultDomain_0&hash=item27b8fd4ddb

They are nominally 24v with adjustable voltage control on the output.... if you change the series resistor going to the trimmer pot, you can push it up a few more volts without danger. These ones go up to 26.4 or thereabouts, it's no problem extending this a bit.

There are 27volt versions, but more rare/dearer. (26-31v)

They are switch mode power supplies. You can dial up your voltage... but most importantly, for battery charging you will have terrible power factor... and these things have internal power factor correction, and so leave your alternator with much better control (less current in the windings for the same actual power output)

or

Grab an old microwave oven transformer, haul out the secondary, pull out the shunts (metal plates between the primary and the secondary) and rewind the secondary with heavy wire.
 I did one a long time ago here:




good for about 20A or more@42v.. or 40A@22v

This transformer is wound for saturation, so best run with a decent AC capacitor in series to stop it from heating up, and keep the low batt voltage surge to reasonable levels..



..............oztules

[birdhouse]

thanks oz!

i saw those LED power units while hunting.  i was concerned on weather they'd go higher than 24-25 volts, but sounds like they're a go, especially if you mod them. 

i hope you don't mind if i PM ya once i get it, cause i'm really kinda lost on replacing a resistor with a different value.  i mean, i understand what your saying but would have no idea what value to use, or where to find this particular resistor within the unit. 

adam

[oztules]

No problems with the PM.

If you look at the pictures in the first link, you will see the trim pot on the left hand side where the V adjust is labled.

It is a simple task... see which way the pot turns for max voltage. If it pulls the rail to ground for higher voltage, then the pot shorts for max voltage... but it will be in series with another resistor to stop you driving it really to ground, and pushing the V out through the roof .

So we find that series resistor, and change it by 10% lower..... then when we use the trim pot, it will end up 10% closer to ground when fully turned up.

If you think about it, as you  pull the voltage sense closer to ground, it will have to have a higher output voltage in order to develop the same control voltage the PWM chip is looking for... so it increases the pulse width until it gets what it wants.

I have the smaller 24v meanwell unit, and use it for a variable voltage / current controlled source... so I can control the current from 0-15A, and the voltage from 18 to 48v.... they suffer a fair amount of thuggery and still survive. (I don't get 15A at 48v though with this setup... too many watts ). (uses a tl494 in this model)

They also have a 27v unit that will require no messing about with, but will be dearer as they are usually not competitive in stock units.



.........oztules

[birdhouse]

thanks again oz!

ended up getting a 15A 24v unit.  $34 to my door. 

i'll let you know when i get it!

adam

[Volvo farmer]

You mind giving a link or something? I also have an old Honda EX1000 (pre-inverter model) and was recently looking for a cheap 24V charger to help with bulk.

[birdhouse]

VF-
http://www.ebay.com/itm/24V-15A-360W-Switch-Power-Supply-Driver-LED-Strip-light-Display-200V-240V-/390347714048?pt=LH_DefaultDomain_0&hash=item5

adam

edit:  it says 200  240v, but if you read in the listing, there's a manual switch on the side of the case to have it run at 110  120v. 

[ChrisOlson]

Why wouldn't an inverter charger work?  Just hook the gen output up to the inverter's AC input.
--
Chris

[Volvo farmer]

Because when an inverter charger is charging batteries, the only power coming into the house straight out of the same generator that I'm trying to charge batteries with. So if I'm putting 500 watts into batteries with a 1000 watt generator, and the refrigerator comes on, things are going to get ugly.

Also, most of the decent inverter/chargers for 24V are running in excess of $1000. This thing is $34 

[ChrisOlson]

Because when an inverter charger is charging batteries, the only power coming into the house straight out of the same generator that I'm trying to charge batteries with. So if I'm putting 500 watts into batteries with a 1000 watt generator, and the refrigerator comes on, things are going to get ugly.

Oh, OK.  That must be different than mine then.  Mine "blends" power and uses the gen to run loads and charge the batteries, and if the load exceeds the gen output the inverter quits charging and uses battery power to help the gen until the load goes away, then it goes back to charging.

Carry on   
--
Chris

[rossw]

Oh, OK.  That must be different than mine then.  Mine "blends" power and uses the gen to run loads and charge the batteries, and if the load exceeds the gen output the inverter quits charging and uses battery power to help the gen until the load goes away, then it goes back to charging.

+1

[halfcrazy]

Yeah it is a shame the SW was one of the only inverters with "Gen Support" this feature allows the inverters to add to the generator. It truly is a shame this never got put into the other brands.

[rossw]

Yeah it is a shame the SW was one of the only inverters with "Gen Support" this feature allows the inverters to add to the generator. It truly is a shame this never got put into the other brands.

Mine isn't a SW, but it has it.