Upgraded to 48v lithium; confused about blue wire, black/white wire for accessories

[enfantterrible]

Thank you. Makes sense.

[enfantterrible]

I have now set this all up, and it's working nicely. I bought the two items that PingEye3 recommended. Thank you for the help with that.

I do have one outstanding issue, though: The 48v reducer is draining my batteries when the cart is off. I have configured the reducer to depend upon the key switch—but, having run some tests, that only seems to apply to the output of the reducer. In other words: When I turn off the key switch, all the accessories that are connected to the fuse box that is after the reducer in the chain do, indeed, switch off; but the reducer itself does not. Not only can I see that the reducer is drawing power by using my meters (and from the digital readout attached to my Lithium batteries), but it is constantly warm to the touch (and, when I physically unhook it, it's not).

I assume that if I want to alter this, my best move is to put a switch between the batteries and the reducer? Something like this, that can handle 48v: https://www.amazon.com/gp/product/B0...SYWK2555&psc=1

Thank you.

[Pat911]

Are you able to measure the input current draw of the reducer when the switch is off? It may be quite negligible, I know mine is as I leave it on continuously to keep the radio memory.

Cheers
Pat.

[enfantterrible]

Originally Posted by Pat911

Are you able to measure the input current draw of the reducer when the switch is off? It may be quite negligible, I know mine is as I leave it on continuously to keep the radio memory.

Cheers
Pat.

I'll try to do this. If it is negligible, though, then I guess I have a different problem, because there's no way that a pair of brand new Lithium batteries should be losing 8 percent of their SOC overnight, right? The LED SOC meter uses 1 percent per day at most, and I can't imagine that the controller on the cart would be that thirsty absent a problem (although I may be wrong about that, of course).

[Pat911]

I haven’t charged my cart in over 2 months as it is winter here at the moment. I have the cart in tow mode to reduce current draw but the reducer is permanently connected. I’ve lost less than 1 volt in all this time. My power consumption in about 20mW. At that rate my 120Ah battery will last over 8 months.

8% capacity loss overnight is extremely high. Assuming you have 2 of the 30Ah Relion batteries, 8% (4.8Ah) loss over 12 hours (overnight) equates to a 400mA draw. That is VERY high standby current.

[enfantterrible]

Originally Posted by Pat911

I haven’t charged my cart in over 2 months as it is winter here at the moment. I have the cart in tow mode to reduce current draw but the reducer is permanently connected. I’ve lost less than 1 volt in all this time. My power consumption in about 20mW. At that rate my 120Ah battery will last over 8 months.

8% capacity loss overnight is extremely high. Assuming you have 2 of the 30Ah Relion batteries, 8% (4.8Ah) loss over 12 hours (overnight) equates to a 400mA draw. That is VERY high standby current.

Yes, it's bizarre. It's actually worse than 8 percent over 12 hours. I've been keeping detailed notes, and here's what I found thus far (to confirm: these are two 30Ah Relion batteries, as you guessed):

1. With everything plugged into the batteries (controller, charging cables, cables to 48v reducer) and the cart unplugged from the charger, it's essentially losing a percentage point every hour.
2. With the 48v reducer and the fusebox completely removed from the system, and the cart unplugged from the charger, it's losing a percentage point about every three hours.
3. If I leave the charger on overnight, the batteries hit 100%, but then by morning they're around 92%, even though the cart is plugged in.

I'm going to run some tests more methodically, including seeing what happens to the batteries if nothing except the meter is plugged into them, but I'm a little at a loss as to where I should start troubleshooting this. I suppose it's possible that the meter is inaccurate, but, in my experience in other technical areas, that's rarely the case.

For reference, my system is setup like this:

1. The two batteries are connected together in parallel with busbars that run, respectively, from positive to positive and negative to negative.
2. The OBC is bypassed: The purple, red, black, and yellow wires are capped off; the white and blue wires are spliced together.
3. The main positive wire to the controller is connected to the positive terminal on battery 1. The main negative wire to the controller is connected to the negative terminal on battery 2.
4. The positive charging cable from the charging port is connected to the positive terminal on battery 1. The negative charging cable that once ran into the OBC now runs directly to the negative terminal on battery 2.
5. The positive IN cable on the reducer is connected to the positive terminal on battery 1. The negative IN cable on the reducer is connected to the negative terminal on battery 2. The green control cable on the reducer is connected to the key switch. The positive OUT cable on the reducer is connected to the positive port on a fusebox. The blue low-voltage OUT cable on the reducer (for accessories with memory) is capped.
6. The main positive terminal on the fusebox is connected to the positive OUT cable on the reducer. The main negative terminal on the fusebox is connected to a ground wire that runs out of the OBC and has a bullet connector on the end (this used to connect directly to the negative input on the light harness).
7. The positive wire running to the light harness is connected to one of the positive bays on the fusebox. The negative wire running to the light harness is connected to one of the negative screws on the fusebox.
8. The positive wire running to the USB charger is connected to another of the positive bays on the fusebox. The negative wire running to the USB charger is connected to another of the negative screws on the fusebox.

As I say, I'm a little stumped. My plan now is to charge the batteries to 100%, disconnect the charger, disconnect all cables except the meter, and see if/how much they run down. Then I'll re-add things one by one, and re-run the tests.

[Pat911]

Do that test and report back. Some of those meters can have a significant draw, especially the LED ones. The LCD ones draw less.

Also, connect the negative fuse box directly to the reducer, not the OBC. Don’t know if that’s your problem but it may help.

[enfantterrible]

Originally Posted by Pat911

Do that test and report back. Some of those meters can have a significant draw, especially the LED ones. The LCD ones draw less.

Also, connect the negative fuse box directly to the reducer, not the OBC. Don’t know if that’s your problem but it may help.

Thanks. I've started the tests, and will share my results.

On your second point, quick question: The reducer I have doesn't have a negative out, it just has a negative in. (It has (1) positive in, (2) key-switch on/off, (3) negative in, (4) switched positive out, (5) constant low-voltage out.) I understand that the negative in wire in effect does both, but is there any particular way you would wire this?

[Pat911]

Connect the fuse box negative to the negative battery post.

[enfantterrible]

Alright. I tested three configurations, each from a starting point of 65% SOC. For all three configurations, I recorded (a) the SOC according to the meter, and (b) the voltage reading across the two batteries. I did this every hour.

Before I started, I altered my wiring per Pat911's suggestion, so that the negative wire from the fusebox runs to the negative post on battery 2.

Here's what I found:

1. Without anything except the LED meter plugged into them, the batteries dropped 0.1 volts over eight hours. During that period, the LED meter suggested that the battery's SOC had diminished by 2%.
2. With the cart in Drive mode, and the 48v to 12v reducer disconnected, the batteries dropped 0.1 volts over eight hours. During that period, the LED meter suggested that the battery's SOC had diminished by 2%.
3. With the cart in Drive mode, and the 48v to 12v reducer connected, the batteries dropped 0.1 volts over eight hours. During that period, though, the LED meter suggested that the battery's SOC had diminished by 9%.

This is out of my area of expertise, but assuming that I'm not making any major mistakes, I might conclude the following:

1. That the batteries are not self-discharging at any meaningful rate (good news).
2. That the 48v to 12v reducer (which is warm when connected) is pulling from the battery when not in use, albeit not at a particularly alarming rate.
3. That the LED meter (or whatever is informing its output—perhaps the BMS?) is not especially accurate.

These conclusions presuppose that testing the voltage of the batteries a good way of tracking their SOC, and that testing that voltage to a single decimal point (which is all my meter can do) is informative. If that is correct, it is reasonable to conclude that if

(a) for all three tests the reduction in voltage was just 0.1v, but
(b) in only one of those tests (the third) the LED meter dropped dramatically, then
(c) the LED meter must be wrong/confused by the slow draw of the 48v to 12v reducer

If these conclusions are correct, it would definitely be worth it to me to put a switch between the batteries and the 48v to 12v converter simply to stop the LED meter from giving me an erroneous readout. But, obviously, I am keen not to assume that I have a fundamentally aesthetic error if, in fact, I have something more serious. Thank you once again for your help!