Sabvoton 72150 help

Hi. I have recently finished my build. Specs are QS 205 50h 5T, sabvoton 72150 and 72v 40ah battery with Samsung 35E cells, 3500s. I only have the Bluetooth app set up and the bike runs ok though top speed is just under 40mph and torque won't lift the front unless I help it. I am wondering what amps my battery should produce, on the shunt LCD its peak 118amps tho I am told controller and hub can Handle far more. Can anyone suggest settings for this combo, including how i set up programming from laptop? Thanks in advance. D.

What's the max continuous current limit on the battery's BMS? That is your limiting factor for running the bike.

You can set a peak current as high as the peak battery limit, but you don't want to use that for more than a few seconds at a time.

The BMS is 50amp and I disconnected the discharge as it was cutting out battery at 72v and wouldn't come back on until I charged it. Now it has a little more torque and no issues but BMS is still connected for charging. The battery is 20s/12p and from what I can see the Samsung 35E cells are 5 amp continuous 8amp max discharge. Cheers.

You need a usb cable to program from your laptop.
Which display are you using?
Do you have a multi power switch? (3 speed)
You should easily be able to run 100a + with your setup.
Post some screen shots of your app settings .
Where are you located?

Jonno

amberwolf said:

What's the max continuous current limit on the battery's BMS? That is your limiting factor for running the bike.

You can set a peak current as high as the peak battery limit, but you don't want to use that for more than a few seconds at a time.

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Seems like the cells are the limiting factor. When drawing 118A from cells that have a 96A max, and removing the BMS from the equation, one should concurrently be researching what pack to get to replace it with.

Darnc73 said:

The BMS is 50amp and I disconnected the discharge as it was cutting out battery at 72v and wouldn't come back on until I charged it. Now it has a little more torque and no issues but BMS is still connected for charging. The battery is 20s/12p and from what I can see the Samsung 35E cells are 5 amp continuous 8amp max discharge. Cheers.

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What does "disconnected the discharge" mean?

If you mean that you bypassed the BMS's ability to shut off the output to protect the pack when there are problems, by connecting directly to the cells, then that's a bad idea when it's cutting out like that. (If you want the BMS's protection against overdischarge and unbalanced cells, it's also a bad idea because it can't protect them if it's discharge port is bypassed).

If it was shutting off at 72v, it means it was likely detecting a problem with a cell or cell group, usually one that has a bad cell or cells, or an interconnect issue that's decreased that group's capacity and capability, so it's likely overstressing that group (or groups), and making the root problem worse, just masking it.

It could just be that below 72v the cells and/or the BMS can't handle the current you were drawing, in which case you need either a better BMS (but not one that exceeds the cells' capabilities), or better cells.


If you mean something else, be very specific and we can help you find the problem and fix it.


Either way, if the BMS is 50 amp, then that's the limit your controller can pull from the pack, regardless of what the cells can do.

The cells aren't made to handle what you want out of it either, so at this point you should probably either replace the pack entirely, or buy a second one to keep in parallel with it while riding, so you don't overload the pack and damage it (which has the potential to cause a fire, as unlikely as that is it's still possible, especially if you bypass the BMS's protection).

Darnc73 said:

The BMS is 50amp and I disconnected the discharge as it was cutting out battery at 72v and wouldn't come back on until I charged it. Now it has a little more torque and no issues but BMS is still connected for charging. The battery is 20s/12p and from what I can see the Samsung 35E cells are 5 amp continuous 8amp max discharge. Cheers.

Click to expand...

Your battery cells are not strong enough.
Also you mentioned 40 mph with the 72 V battery? Should be getting more top speed than that. My QS205 is a 6T and I get a little over 40 mph without flux weakening. Around 50 mph with flux. So what winding do you have for your QS205?

Not sure about winding. Motor is 50H V3 that's all I know. Can you recommend a cell and where I can get these cheap in Scotland or UK? The battery was ordered from China and at the time I knew noting about cells/amps etc. Like I do now So battery upgrade is what I need. I don't want to overload the battery cells or damage them so what settings would be recommended for my controller? I will post some pics. Also Flux Weakening seems to make no difference.

You don´t need a cable for the computer.
Bluetooth is enough.
Your Sabvoton is set to max current 150A
Either your battery does not give more current or your motor does not want more current, or your cables between battery and controller are limiting the current.

How much is the voltage sag while full throtle?

Don't know about voltage sag, the shunt has a small LCD I will use my GoPro to record that when I get home. Think maybe my battery is the issue. Highest I've seen it discharge at was 118amps. The battery had 12awg to controller which I changed to 10awg, is this ok?

Amberwolf.
I disconnected the BMS, or bypassed it. The bike I built not knowing anything about these bikes so please excuse my ignorance with regards to battery amps,volts, controller amps etc. The reason I disconnected it as like I said, at 72v it was shutting off, brand new battery, and I was left to push the frocker 4 miles the last time it happened. From what I can gather my controller can draw 150amp max or continuous, but battery can't deliver it. I think the solution for now is limit controller amps to max battery discharge until I can get a more suitable battery. Or maybe build one. The BMS still works when charging and I keep an eye on voltage usage through the mqcon app so I'm not bothered there. I should have researched better what battery I needed for the set up.

The SVMC gives 150A until it either shuts off with an over current error, or it shuts off when it reaches his max temperature, in the first situations you can only drive on if you have the posibility to switch the power to the controller off, as the app has no reset switch for errors, or I didn't find it.
I had to reset mine to factory settings and set everything again in the app.
I have never reached over temp, so I don't know if this is self resetting.

Awg10 is too small for drawing 150A for long times.
I think you should stay under 100A with the controller until you have better bms, battery, and bigger wiring.

Darnc73 said:

I disconnected the BMS, or bypassed it. The bike I built not knowing anything about these bikes so please excuse my ignorance with regards to battery amps,volts, controller amps etc. The reason I disconnected it as like I said, at 72v it was shutting off, brand new battery, and I was left to push the frocker 4 miles the last time it happened.

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YEah, that usually sucks. I have a very heavy cargo trike I couldn't push or ride very far without power, especially if it was loaded (though to be fair, I couldn't do much with a plain bicycle these days either ).

From what I can gather my controller can draw 150amp max or continuous, but battery can't deliver it. I think the solution for now is limit controller amps to max battery discharge until I can get a more suitable battery. Or maybe build one. T

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Yeah, I'd just reduce the controller max amps to whatever the battery was made for. Won't be as fun a ride, but it'll be safer for the battery till you can add to or replace it.

he BMS still works when charging and I keep an eye on voltage usage through the mqcon app so I'm not bothered there. I should have researched better what battery I needed for the set up

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.

Ok. I just don't want to see anyone that doesn't know about the potential problems to end up with any dramatic types of failure modes because those really suck. :/

Regarding monitoring while riding, the problem isn't voltage for the pack overall, the problem is voltage on any cell groups that don't perform as well as the others, which you can't see from the controller (only from the BMS--if you have an app to see that, then that can work alright as manual control). If a cell group has a big enough problem, it may look pretty normal for overall pack voltage on a 20s pack, maybe a little excessive voltage sag, but the group itself could be dipping down way below safe levels especially as you're closer to empty than full for the whole pack. Sometimes that makes cumulative damage to the group that over time can lead to a fire (rare, but it happens--usually the cells just get trashed).

As long as all the groups are equal, it's not that big a deal--but problematic groups are usually a lot higher resistance, so they heat up a lot more than others under excessive loads, and in your situation that's more likely to happen.

Amberwolf.
I've set the controller to 100amps, not as quick, but top speed is roughly the same. Tbh it's not used much right now as it's freezing here in Scotland. I think the next move is to build my own pack with a Bluetooth BMS.