Hey Guys,


I'm on a journey to build a "dirt cheap EV" to prove to people that 1) you don't need to spend gazillions to own an EV commuter and 2) any dum dum, namingly me can build one.

so Ive acquired 48 (VRLA, 12v, 33ampere) batteries from the scrap metal yard and I need to find a way to charge 40 of them as a 48v pack, Ive created 4 series strings of 10 and made the whole pack parallel with soft copper pipe hammered flat bus bars. (I have a 48v AC 3-Phase induction motor and 48v 500a controller from a forklift)


Ive also acquired 4 x DPS1200FB A Power supplies: input 200v-240v ~/7.8A, output 1200 MAX, +12V / 100A MAX. I've successfully modified one of them to output 13.5v. the float range for the cells are 2.23-2.27 (13.36-13.62) so its good enough for a float voltage but I really need a boost charge as well, not sure what a boost charge would be but I'm guessing 15v

So I need a charger that can ideally adjust voltage from 48-60v and the Current as well, I'm guessing 1-?10? Amps or however many Amps required to charge 1320Amperes of battery pack, not that they will have 1320amperes as I retrieved them from the scrap yard.

and to conclude I'm a total electronic muggle... I need to find a cheap solution but I don't mind paying a few dollars for a pre configured circuit board/ components, just not $2000 dollars NZD!. I had a look on ti.com at DC/DC step-down regulators/buck controllers but the battery management components either weren't in the right voltage range or the current was too low..

48v chargers are rare and super expensive here in New Zealand same goes for technical support..

hope you can help

thanks in advance

Stephen

 

Welcome to AAC. I hope that you get some helpful advice here. Of course some will be cynical but you learn to take the bad along with good.

Did it occur to you why the batteries were in the scrap yard?

If you want to learn about how to charge lead acid batteries, this is the place to go:

http://www.batteryuniversity.com/learn/article/charging_the_lead_acid_battery

 

Hi, thanks so much, that was a good recap also learnt new things. the batteries might be knackered but I swapped all the old batteries I had and paid a little extra in cash, even if they only get me up and down the road it'll be a good learning curve and I can return them and get half my cash back, it would've only cost $200.

so, i really want to get these batteries charging, are there any off the shelf semiconductors and schematics, i dont necessarily need to build something up, even if i pay a little extra for an all in one voltage regulator current regulator that I can connect to my Power supplies in series 48-60v. although ideally i would like an automated system. just seems the prices of 48v battery chargers are exorbitant...

cheers

 

Hi,

would something like this do the trick?

https://www.aliexpress.com/item/120...upply-Module-8-60V-to-12-83V/32458534088.html

I might be able to grab 5 x 460w 12v power supplies from work and wire them in series for a 60v PS

is this the right forum to ask these questions or should I try somewhere like rcgroups.com?

Cheers

Stephen

 

Have you checked the junk yard for old man/aerial lifts? The battery operated models usually use 8x6v batteries and would have all the components necessary to build the charger you need. It would likely be a trickle charger (most seem to be rated for less than 5A.

 

thanks Mate, good idea but I think the chances would be pretty low of finding an aerial lift in the junk yard here in NZ unfortunately. most scrap metal yards don't even allow someone off the street access.

 

Look into solar charge controllers.

You just have to feed them DC, not necessarily from a solar panel either. Nudge nudge, wink wink.

One that will take up to 150 to 200 VDC as input would be perfect, but the affordable ones seem to be limited to about 70 volts input max.

Solar companies should be able to price you out a unit that would accept the input levels you need and would come ready to charge the batteries without internal modification.

 

that's a great idea, would kill 2 birds with one stone but I heard that solar charge controllers don't like a DC source other than from PV's? or is that sales talk? I don't know why, don't understand. would hate to destroy it, but if there's no issue with feeding a power supply DC source into a solar charger then I'm keen!

 

Cheapese manufacturers probably make units that won't operate well with a little hum in the input, but any major manufacturer will have designed a circuit with plenty of tolerance for such a minor annoyance.
If you have a steady source of DC above 60 volts and with more wattage available than your charger can deliver then the presence of a little AC hum will make little difference.
Be sure the power supply has a large overhead of available power.
Rectified AC supplies have horrible output waveforms when pushed to the rated limit of power output.
Don't use a 1000 W dc supply to power a 900 W battery charger that needs clean DC voltage.
Use a 1500 to 2000W supply instead. The DC will have much less AC noise this way. This will prevent any problems if you go with a solar charge controller. Remember they deal with voltage that changes, just much more slowly than 60Hz, so they can operate with changing voltage levels, but best to keep it small changes. Not approaching the upper power limit of your supply will prevent large AC variations from appearing in the output.

 

Thanks for the lead Kermit! using a solar charge module what I originally wanted to do, its multipurpose and future proofed (to a degree) one day I can buy some PV's and power the house

 

that's a great idea, would kill 2 birds with one stone but I heard that solar charge controllers don't like a DC source other than from PV's? or is that sales talk? I don't know why, don't understand. would hate to destroy it, but if there's no issue with feeding a power supply DC source into a solar charger then I'm keen!

Something you might find cheap is a golf cart charger. It might be a little slow (15 amps I think) but you might get one cheap.

 

great ideas, thanks guys I don't know any sparkys, any advice here would cost $$$$ so this forums great.

Cheers

 

Ive also acquired 4 x DPS1200FB A Power supplies: input 200v-240v ~/7.8A, output 1200 MAX, +12V / 100A MAX. I've successfully modified one of them to output 13.5v.

If you modified them to get 13.5 volts just take them the extra ~1 volt more to get into the proper ~14.5 volt range you need and skip the extra work and cost of adding more power supplies.

 

that would be the ideal solution but...

"Once the pot is replaced, you can turn up the volts to 13.5v. Going higher than 13.5v will invoke a crow-bar overvoltage protection circuit which will turn off the output."
http://tarpn.net/t/builder/builders_power_supplies.html

maybe I can series 5 together at 60v that way I wouldn't have to modify the potentiometers.

 

Is it technically possible to connect 6 12v PSU's in series and then use a Current and voltage regulator? My VRLA batteries need 14.4v for a bulk charge.

Modifying PSU's seems to be the absolute cheapest way to charge batteries? If it was possible.. theres a few good instructsbles for turning PSU into lab supplies and even connecting in series but I can't find much on charging a 48v pack.

No luck with second hand or cheap golf cart chargers or Solar Charge Controllers as yet..

Thanks for your patience..

 

Whoops I mean 5 PSU's...