Controlling a charger transformer

Thread Starter

frankr2994

Joined Apr 30, 2020
36
Ok so my BS stupid battery charger stuff continues. This time it's basically spend little to no money because we may not keep the forklift. Struggling to go over uneven ground if you bring it to a stop. Anyways given that I might just sell the machine I'm attempting to see if I can make the 36v single phase charger that we bought work better. To my understanding of the absorption stage of charging the 36v battery it needs approximately 44.1v. this little charger kicks off at 42.6v which when charging even a fairly depleted battery the charger is only on for about 4 hours....I spliced in a variable resistor today to what I'm calling a voltage sense for the controller. I had to keep adjusting it as the day went on to keep the charger on and voltage in spec. I'd like to either find a way to control that sense line or another way all together to control the transformer. Screenshot_20211110-185123.png

So the red wire off the controller going to the dc+ line is what I spliced the resistor into. Started out around 250 ohms to get the voltage close to 44v and finished at about 80 ohms to make the charger shut off at 44.3v I was able to get about an 8 hour charge on it today after the charger "said" it was charged yesterday. The other feature that I would love it to have is float. Float voltage should be under 42v. I don't have a way for the charger to stay on at that low of a voltage when the battery is charged.
Again any input is appreciated
 

Thread Starter

frankr2994

Joined Apr 30, 2020
36
So I've found out something. The charger can only put out just over 44v. Logic in the controller shuts it off when current is down to 6amps. So setting my resistor to max which is around 600ohms the charger throws everything it has until the current tapers down and then still kicks off automatically. This does work. I've been reading on this circuit and am curious to see if it can be improved. From what I've gathered if I could make it a full wave rectified circuit I should be able to get more voltage out of it. Does this also mean I should be able to draw more current? When I'm above say 42v in the charger it can only output 14 amps. Below that voltage I can hit the rated 21 amps.
 

LowQCab

Joined Nov 6, 2012
1,929
The question is ..........
How much Money is your time worth,
and how much does a new proper Charger cost ?

I can show You how to modify what You already have into a very high performance Battery-Charger,
but it ain't cheap, and may take you a Month or 2 to complete.

Maybe all You really need is an add-on Float-Charger,
that would be considerably cheaper to build.
.
.
.
 

Thread Starter

frankr2994

Joined Apr 30, 2020
36
Regardless of time, difficulty and money I'll always accept knowledge. So on that I'd love an explanation on how to convert that charger into something better. A real single phase charger for this machine is about 1,700 dollars.
 

LowQCab

Joined Nov 6, 2012
1,929
OK,
Well if you're really dedicated, and want to spend about ~$500.oo in parts,
here's how I would do it ............
Some of the values and parts will need to be adjusted for the higher Voltage You need.
.
.
.
High Current Battery Charger FLAT .png
 

Thread Starter

frankr2994

Joined Apr 30, 2020
36
I'll definitely study that tonight. I was a general contractor for years and have wired complete houses and have since then been employed as a race car mechanic doing custom work every day. Not afraid of a challenge and very good at grasping things I haven't previously delt with. Originally though I was curious in making an improvement to what I currently have. Could I get more volts/amps out of my current transformer. For 50 amps I have looked into the possibility of using server power supplies wired in series connected to a charge controller. Never got any input from anyone on here for that. However I believe I could get 36v 60amps for under 300 going that route. I would assume your schematic is more efficient as each of those supplies are rated at or above 80 percent efficiency then feeding a charge controller that knocks it back some more.
 

Thread Starter

frankr2994

Joined Apr 30, 2020
36
For instance. What I've been reading on is this. separate-each-rectifier-diode-out.jpg

I didn't draw that and I'm curious if I can apply this to mine and how much benefit I can see from it.
 

LowQCab

Joined Nov 6, 2012
1,929
Large Heat-Sinks required for the Bridge-Rectifiers.
No means shown for Voltage-Regulation and Current-Limiting.

The original design is the minimum parts-count possible,
but has some possibly serious quirks caused by "Phase-Angle" SCR-Regulation,
( virtually the same principle as used in a cheap wall-mounted Light-Dimmer ),
which produces brutal amounts of dirty Electrical-Noise / Hash
which can be deadly, or disruptive, to any sensitive Electronics-Circuitry nearby.
This may, or may not be, an issue for you depending upon your environment.

Unfortunately, "High-Current-Filtering" gets expensive real fast.

An "Inductor-Input" filtering scheme will increase the overall efficiency substantially
and extract the maximum amount of power possible out of the Transformer
and reduce, or eliminate, any Electrical-Noise,
and reduce waste-heat-dissipation requirements.
.
.
.
 

Thread Starter

frankr2994

Joined Apr 30, 2020
36
As far as dirty noise is concerned the battery has to be disconnected from the machine to charge. I know the majority or chargers produce a very dirty signal which is why we don't use them while doing any programming to vehicles. And a heatsink for the diodes is not a problem. Rear or that charger right now is one big plate of aluminum for an overkill heatsink for the 2 scr's. And yes I know that diagram doesn't show voltage or current controll. I would need help on adding that on. I've read that scr's really do their function well with AC not so much DC. So I'd have to come up with something different. So I'm sorta looking for the middle road answer. Your schematic is still very valuable to me. As far as programming and flashing cars I would love to have a super stable/clean power source. I may start getting items together just for that.
 

LowQCab

Joined Nov 6, 2012
1,929
Fork-Lift .........
With the Batteries disconnected,
the Deep-Cycle-Batteries that are used can take a tremendous amount of Charging abuse,
so the "Phase-Angle" regulation scheme, with no Filtering, is definitely a much cheaper route to take.
But unfortunately, I personally have never bothered to learn how to drive SCRs,
so I can't help You there,
and all You really need is a re-designed Driver-Board to make the SCRs do what You want.
But, there are several other regular-contributors here who can help You with that, if they are so inclined.

"" As far as programming and flashing cars, I would love to have a super stable/clean power source. ""

The Schematic I provided is ideal for Automotive applications,
in fact, You really don't need any where near the ~50-Amp capacity,
half that capacity would suffice for ~99% of your needs, and be MUCH cheaper to build.
For a ~25-Amp Charger / Supply, I would probably do almost everything differently,
and it would be a much simpler arrangement.
.
.
.
 

Thread Starter

frankr2994

Joined Apr 30, 2020
36
Actually for what I would "want" for a programming charger would be 40 amps min. I like to keep the voltage stable and sometimes fans and fuel pumps are running. This would be on standalone ecus also wouldn't be the first time I was flashing a Porsche and the engine fan came on to pull engine heat. Saves time if I don't have to disable things in between writes. But ya if anyone would like to chime in on either controlling the scr's I have or a different current voltage control after doing a full wave rectification on that transformer I'd appreciate it. Last question I have is what is a common software you guys use to draw all these schematics up with? Preferably something that let me do a simulation. I tried a few that were just awful for me to use which is why I don't post anything really that I drew.
 

LowQCab

Joined Nov 6, 2012
1,929
"" I like to keep the voltage stable and sometimes fans and fuel pumps are running. ""
Are You running the Computer without a Battery in the Car ????
If so, that's a very dangerous thing to do.
Or am I
misinterpreting your statement ?

The Battery needs to be there to stabilize everything, at all times.

It should make zero difference to anything in the Car for the Voltage to temporarily drop down to ~10-Volts,
and then, (if the Engine is not running),
the Charger can replace any lost Battery-Charge that the Alternator may have not handled adequately.

If a ~30-Amp-Fan inadvertently kicks-in,
with the Engine not running,
and you have a ~25-Amp-capable Charger hooked-up,
the drain on the Battery would be around ~5-Amps,
which the Battery should be able to handle for at least ~4-hours,
and I'm sure the Fan wouldn't continue to run for more than a few minutes,
after which,
the Charger would quickly have the Battery recharged in
just a few more minutes after that unexpected incident.
.
.
.
 
Last edited:

Thread Starter

frankr2994

Joined Apr 30, 2020
36
Really just me being paranoid. I have yet to brick an ecu. There is always a battery in the car but if I had a preference I wouldn't like to see a voltage drop when accessories turned on. I know on some of the later cars modules can be turned off when a discharge is detected. Gets really screwy and the car doesn't always let us know it's going on. Stuff just quits working. Voltage is almost always still above 12v when this happens. Haven't had to flash one of those yet and not sure if it would matter if some of those ecus shut down during a flash but it's just one of those better safe than sorry situations.
 

LowQCab

Joined Nov 6, 2012
1,929
It's almost impossible to "Brick" an ECU made in the last ~10-years,
but who knows,
certain non-essential things could be shut down under certain circumstances,
but I would estimate that it wouldn't be a shut-down of any Computers, or Network-Connections,
they just don't draw enough Current to make any difference,
and,
during a software up-grade, comms with other Computers in the Car is generally not possible,
unless they have things set up for Software-Up-Dates over the Internal-Network, ( usually CAN ),
in which case,
it's guaranteed that no Computers would be shut down during an Up-Date-Procedure.

Check the appropriate Manual for the exact procedure,
if there might be an issue during an Up-Date, it will be spelled out in no uncertain terms,
and they would certainly have an exact protocol for insuring that nothing bad happens.

When a request is made to the Computer for a Software-Up-Date,
all other normal functions should immediately stop,
( including activating Cooling-Fans / Fuel-Pumps, etc. ).

All of the Computers in the Car are purposefully designed to
operate properly down to around ~7 or ~8-Volts.

The Car needs a Health-Battery,
the Voltage shouldn't drop below ~11-Volts when cranking.
If it's lower than ~10,
Charge the Battery, then re-test,
if it's still low,
correct the problem before proceeding with any Software-Up-Dates.

Unless You know for a fact that your Battery-Charger has a well Regulated, and well Filtered Output,
it SHOULD NOT be connected to the Car during a Software-Up-Date.
.
.
.
 

Thread Starter

frankr2994

Joined Apr 30, 2020
36
All good points. End of the day I've gotten screwed on too many things over the years that are somehow a fault of my own that no one could explain to me how it would have happened in that chain of events. Right now when I do writes and I'm talking about firmware level and software I make sure the car battery is charged and I just hook a charge jump back up as well. Reason I was asking about the charger was I don't own one that I would chance being connected while doing anything. 25 amps more than likely is enough but I can also tell you from experience on completely custom stand alone cars thats given me trouble on tuning that I've had to stop for the day and charge the car battery and my jump pack so I can continue tomorrow. Regardless this isn't my problem at hand just a bonus on my end that you provided something I believe could be of use to me. You bring up many valid points on why 25 amps would be enough. I'd you would like to share how to build a very clean 25 amps source I'd appreciate it. Typical chargers meant for flashing are 400 dollars and up.

Still if anyone has ideas on controlling scr's or another method of voltage/current controll on my current 36v charger I'd like to hear it.
 

LowQCab

Joined Nov 6, 2012
1,929
I'll work on a simplified, ~30-Amp version when I get some spare time,
it might be a couple of days.

While I'm at it, what is the Circuit-Breaker Amp-Rating on your big charger ?
What is the Full-Scale, maximum Current on your Ammeter ?
What is the "Out-of-Circuit" Resistance measurement of your Current-Shunt-Resistor ?
( It may be printed on the Shunt,
it will be an extremely low value, and sometimes difficult to measure without a high-quality Meter )
Measure the "No-Load" AC-Voltage at either one of the Secondary-Windings, ( they will both be identical ).
If You have any Charging recommendations from the manufacturer, please provide them.
.
.
.
 
Last edited:

Thread Starter

frankr2994

Joined Apr 30, 2020
36
Your help is appreciated. You won't get any lip from me on how long it takes for you to provide said help. Thanks for all your input
 

Thread Starter

frankr2994

Joined Apr 30, 2020
36
I'll be back at the shop tomorrow and I'll get those questions answered. I have a fairly expensive fluke meter. Definitely not the most expensive thing out there but better than most.
 
Top