Controller voltage question
Have been have problems for a while with getting the full voltage to show up on my DrainBrain.
For the last month have been using a C'lyte 36-72v 40a controller with 100v(88.8v nominal) worth of batteries.Has been a pain to get the full voltage to show up all the time.
I will turn the main power(key) switch on and sometimes 29v/39v/40v will show up instead of a 100v.
Repeat on/off of the main power switch will eventually get it working.
It does the same when using 88v(77v nominal)
This controller only had a red button ON/OFF switch
I have checked voltage coming out of the connection going to the controller from the batteries and it is the proper voltage -the problem i think is the inrush of power to the controller trips something out.
In frustration i switched back to my 36-72v 20a dual controller which has a power key switch on it as well.
If i leave the controller switch powered ON when turning main power on -it will do the same -29v/39v/40v thing.
If i use 88v(77v nominal) -it will read that OK with this controller anytime.
If i turn the controller power switch to OFF -and then apply main power -i will get my proper 100v.
My question is- Is there an easy fix for this -maybe something that will leak the power in more slowly?
I'm not sure if true, but I heard that is normal. Have you simply left it on for a few minutes to see if it comes up to the proper voltage rating?
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Yes, it sounds like the meter is tripping out. This sometimes happens if the power is cycled rapidly like if the switch contacts are bouncing or the inrush current is creating voltage spikes.
Does your system have a relay between the batteries and the meter?
Possibly a big capacitor across the power input to the meter would prevent rapid voltage changes.
Either way, if there is a main disconnect, it might be a good idea to figure out a pre-charging circuit. A precharging circuit is usually just a resistor that gets switched across the contacts to allow the main capacitors in the controller to charge up prior to closing the contacts. This prevents the huge current spike you would otherwise get when you connect a discharged cap to the batteries.
On my Vego, I have two power switches. The first one is the key switch, which puts a 1K 5w resistor across the relay contacts and enables the second switch. The second switch (on the handlebars) activates the relay and powers up the controller. I always turn on the key first, then use the handlebar switch to turn the scooter on and off.
Without precharging, I used to weld the relay contacts closed once in a while. This can ruin your day, not to mention it's rough on the relay contacts.
The slow voltage drop when you turn it off is the discharge of the main caps. My Vego didn't have a problem, but I just wanted to keep it that way. The main relay I'm using would take a beating without the precharge. Your main switch is apparently beefy enough to handle the current inrush. I used a 1K 5watt resistor. There's only a brief time when there's current in it, so it doesn't get hot. If I mess up and try to power the motor through the precharge resistor without the relay on, then it gets hot, but not destructively hot.
Just as a test, you could possibly rig up a 120v incandescent light bulb as a resistor.
If the controller has a logic power switch, turn it off first. Put the light bulb resistor across the terminals of the key switch and see if the meter will come up normally. Once the voltage comes up, then turn on the key switch.
Note for 72V users. On backlit DrainBrains shipped before Oct 26th 2006, it is possible for the backlighting LED to get damaged from an inrush current when it is plugged into a source above 80 Volts. Since fully charged 72V batteries are up to 85Volts, this can cause a failure. The fix is quite an easy one, simply replace the 120 ohm resistor R7 on the LCD circuitboard with one that is between 300 to 400 ohms.
This change is not necessary for 36 and 48V systems. If you have one of these units and plan to run with a 72V pack, please make sure sure to implement this change before plugging it in. I will mail the appropriate resistors to anyone who is comfortable doing the modification themselves, or I can do it at this end if you ship the meter back here.
Go here for more info:
I dont really see this being the fix. If the resistor is on the lcd board it shouldnt have anything do with the a/d in the microcontroller. This could be a fix for a blowing led but i dont understand how it would fix a false reading.
Im going to take a wild guess that the capacitors in your controller charging could be causing an inductive spike that the power supply in the drainbrain cant deal with. Could cause the microcontroller to latch up. I dont think its the current exactly thats doing it, i could be wrong. Does the drain brain update normally, as in when you move does it show amps and watts as it should or is it frozen like a sick pc running windows. In any case fechter(as usual) is right on in that you need a precharging circuit to get rid of the turn on spike.
Do the resistor fix also, just for the sake of the led in the backlight.