Power has been cutting out for a few seconds when going up hill

[Bachgen_o_Gymru]

Hi.
I have a converted bike with a 48v 500w BPM motor, a 20a sine-wave controller with a kt-lcd3, and a 48v 20ah battery. I only converted the bike a month ago and all the parts are hardly used so far. During the last week that I've been riding, the bike has cut out power for a few seconds when going up hill. It has only happened three times so far, on separate occasions. The LCD stays on and doesn't show any error message, but the power just cuts out and then goes back on five seconds later. It has happened when going up hill under load with the wattage at or near its maximum, which is over 900w.
Does anyone know what the cause of this could be? I suspect maybe it is the battery. Perhaps a loose connection? Or could it be the controller cutting power momentarily due to the current being too high?
Any help would be much appreciated.
Thanks.

 

[anotherkiwi]

Touch the controller. You will understand why it is cutting out Don't grab it, you will have a controller tattoo on the palm of your hand...

 

[Benjahmin]

I agree. It's happened to me a couple of times, in hot weather on particularly steep hills.
Can you mount the controller where it will get more airflow? Is there a way to fit a heatsink?
Other than that try to keep your speed uphill to a minimum of around 8mph(not always possible, I know). Be prepared to put in more effort yourself on the hills, in the knowledgr that you get a rest at the top. Counterintuitivly, use a lower setting on the steepest hills
Last time it happened to me, I'd just had lunch and the route I took out of Newcastle Emlyn gave me about a three mile climb. Mostly moderate with some steep bits. The after lunch lethergy was upon me and , consequently, I was letting the bike do more than normal. It was a hot day, fortunately it cut out under some trees, so I just stopped, had a drink and waited until the controller wasn't burn ya fingers hot.

 

[Bachgen_o_Gymru]

Thanks for your replies .

Yeah I figured it was probably that the controller is getting too hot with the high wattage when going uphill. The controller is attached to the bike out in the open rather than being in a box, so it gets good air flow. Attaching a heatsink sounds like a good idea but I don't know how I would do it. Do you know if there's anywhere online where there might be some instructions?

For the first three weeks of using the bike, I had the C5 setting in the LCD set at level 9 out of 10, but during the last week I've had it set at level 10, which is the highest setting for the permitted maximum current. The bike has only done this cutting out since I increased the permitted maximum current to level 10.
I think I should change the C5 setting back to level 9 or even 8 and see if the bike stops doing this cutting out on hills. With the C5 setting at 9, the controller will be 18.2a rather than 20a, which will be fine for my usage.

 

[anotherkiwi]

In my case up upped the voltage to 44.4v from 36v and was seeing about 680 W instead of the usual 540 peak so it really doesn't take much to get it too hot. I am going to try a heat sink and if that doesn't work I'll do the same as you have done and trim the Amps back to 12.5 A, I need the extra rpm more than I need extra power.

 

[Bachgen_o_Gymru]

In my case up upped the voltage to 44.4v from 36v and was seeing about 680 W instead of the usual 540 peak so it really doesn't take much to get it too hot. I am going to try a heat sink and if that doesn't work I'll do the same as you have done and trim the Amps back to 12.5 A, I need the extra rpm more than I need extra power.

I'd like to add a heatsink to my controller too I think. I don't know much about heatsinks though. Would you or someone else on here be able to provide a link to one I could get on Ebay or elsewhere? Thanks.

 

[Fat Rat]

Just put heat sink in eBay
You can get loads of different types and sizes

 

[Nealh]

Surprised error 6 didn't show on the screen which is controller short, China speak for very hot fets causing thermal cut out.
100 x 60mm x 18mm heat sink on ebay or other various sizes depends on you actual controller size and how much extra depth of HS you want to add. If need be put one on each side.

https://www.ebay.co.uk/itm/100x60x10mm-Heatsink-Aluminum-Heat-Sink-Heat-Sink-for-LED-Power-Transistor/142646690392?hash=item213667c258:g:8V8AAOSwogpaT96v
​

Too attach heat sink buy/use silicone thermal heat paste 31g on ebay £1.65, tube is enough to fix two HS's on. It cures by heat so need temporaray to use elastic band until it gets warm again to cure.
https://www.ebay.co.uk/itm/31G-Thermal-Grease-Paste-Compound-Tube-for-CPU-PC-VGA-Processor-Heatsink-Cooling/332408820652?_trkparms=aid=555017&algo=PL.CASSINI&ao=1&asc=20170912102017&meid=74bae3db52ef46e596d0ad5555bd6271&pid=100706&rk=1&rkt=1&&itm=332408820652&_trksid=p2045573.c100706.m4781


I use 100 x 60 with 2x 5v mini fans affixed & paralleled and run off a pair of 18650 cells in 2p 1s.
My controller is in a triangle bag.

 

[Bachgen_o_Gymru]

Thanks guys.

Where on the controller should the heatsink be attached? Should it be the side where the mosfets are?

 

[anotherkiwi]

There are fins there si it has to be stick underneath the logic board side. I thought about screwing the mosfet side to the heat sink and 3D printing a housing to replace the aluminium one but Nealh's silicon paste will be my solution.

 

[Bachgen_o_Gymru]

That's good to know. Thanks anotherkiwi.

My bike did the same cutting out for 5 seconds again today going up a hill. I was only in level 9 and not level 10 of the C5 setting, and the controller felt slightly warm but not hot.

Are you guys sure the cutting out issue is due to the controller receiving too much current? Could it be an issue with the battery instead? Maybe a loose connection somewhere? Presumably, if the issue was with the battery, it would cause the LCD to shut off rather than stay on when the power is being cut? I'm guessing that since the LCD stays on, it means it probably is the controller.

Maybe I should get a controller that can handle more current. I'm thinking maybe the 35a torque simulation square wave controller from PSWPower. I'm currently using their 20a sine wave controller

 

[anotherkiwi]

What is the voltage reading on the LCD when you climb hills? Does it sag over 2v? Where did the battery come from? What cells are in it? What configuration 7P or 8P x 13S?

 

[Bachgen_o_Gymru]

What is the voltage reading on the LCD when you climb hills? Does it sag over 2v? Where did the battery come from? What cells are in it? What configuration 7P or 8P x 13S?

The LCD doesn't show the voltage but it does show the wattage, which is over 900w on steep hills when C5=10, and over 800w when C5=9. The power meter on the LCD sometimes drops a bar on hills and then goes back up a bar when I'm back on the flat. I got the battery from DHGate in China. This is the exact battery I bought: https://www.dhgate.com/product/ebike-lithium-battery-48v-20ah-lithium-ion/384948639.html
The battery is 3.7V, 13S. It doesn't say what the specific cells are in it. The battery has good reviews from other buyers.

 

[anotherkiwi]

"1. Cells - A grade cells to make sure batteries in high and full capacity"

I would say your cells (Chinese A grade) are not up to delivering 20 Amps continuous for a longish period of time. The battery is sagging and slowly coming back up to charge.

The other "buyers" live in flatter lands or... the French one is a bit iffy already.

 

[Nealh]

KT LCD3 shows accurate real time voltage inc voltage sag and voltage recovering.
You can get an idea if it might be severe battery sag by keeping the voltage display on the screen.
The bottom pane displays mileage, odo & voltage you can choose which one you want in view by simply short pressing the on/off button each time.

 

[Bachgen_o_Gymru]

Thanks for your replies guys.

So it looks like it could be either the battery or the controller that's causing the issue.

I might upgrade my controller to one that can handle more current, and see if that fixes this issue. I'm thinking maybe the 35a square wave one from PSWPower (which I would run at a lower current than 35a). Its wiring is the same as my current controller also from PSWPower (except that it is sensorless), so I wouldn't need to adjust or replace anything else on the bike.

If that doesn't fix the issue then I guess it is probably the battery that is causing it.

Next time I go for a ride I'll keep an eye on the voltage on the LCD to see if there's severe battery sag when going up the hills. What would be the voltage reading on the LCD display that indicates voltage sag?

 

[Nealh]

Thanks for your replies guys.

So it looks like it could be either the battery or the controller that's causing the issue.

I might upgrade my controller to one that can handle more current, and see if that fixes this issue. I'm thinking maybe the 35a square wave one from PSWPower (which I would run at a lower current than 35a). Its wiring is the same as my current controller also from PSWPower (except that it is sensorless), so I wouldn't need to adjust or replace anything else on the bike.

If that doesn't fix the issue then I guess it is probably the battery that is causing it.

Next time I go for a ride I'll keep an eye on the voltage on the LCD to see if there's severe battery sag when going up the hills. What would be the voltage reading on the LCD display that indicates voltage sag?

You will see a resting voltage, 49v as an example when you hit an incline and ask for power in a higher pas level take note of the voltage reading, if it collapse /sags heavily say 3 - 4v then the cells used within will be rubbish ones. Once you are riding on level ground or down hill the voltage will settle down again when it has recovered.

Adding a 35a controller will only make you situation worse (if that is at all possible). If the battery isn't able to cope with a 20a load it is no use asking it to deliver more load.

Edited as forgot op was using 48v & not 36v.

 

[Bachgen_o_Gymru]

You will see a resting voltage, 39.5v as an example when you hit an incline and ask for power in a higher pas level take note of the voltage reading, if it collapse /sags heavily say 3 - 4v then the cells used within will be rubbish ones. Once you are riding on level ground or down hill the voltage will settle down again when it has recovered.

Adding a 35a controller will only make you situation worse (if that is at all possible). If the battery isn't able to cope with a 20a load it is no use asking it to deliver more load.

Okay thanks for that information.
If I get a 35a controller, I would run it at 20a or thereabouts. My reasoning behind this is that if the issue I have experienced is due to my controller not being able to handle the high current, the more powerful controller when run at 20a will be able to handle the current, and will not cause the issue I have experienced.
I am aware that if the issue that I have is being caused by the battery rather than the controller, then changing the controller will not help.
I guess I'm just trying to solve the issue by trial and error.

 

[Nealh]

How do you intend on running a 35a controller output to only draw 20a ?

 

[wheeliepete]

The battery supplies the current the controller demands, not the other way round.