Hi folks,

I've bought a spare charger (Sans SSLC084V42) for my 36v ebike that I'd like to tweak down to 80% charge of the battery's capacity (ie 39.6v) to extend the life of the battery.

The original trimpot (3362 P102 T020) in the charger only adjusts down to 41.0v. To test it's range, I tweaked up to 50v before stopping and bringing it back to 42v, I didn't go any further for fear or damage. From what I've read I would need to replace with a 5k trimpot.

My question is around the maximum voltage rating of trimpots and how that might interract with the charger. In Australia we run 230v, the final output would as mentioned 39.6v. Bourne 3362 trimpots are rated at 300v, but Piher horizontal trimpots are rated to 100v.

I'm assuming the charger would drop voltage down substantially before passing through the trimpot, but that's a guess?
Which value does the trimpot maximum voltage rating need to accommodate?
Can I safely use either?
Bourne are out of stock until next year (and I don't want to pay $24 shipping for a $2 part), and piher are available at the local electronics store (Jaycar). I am skeptical of buying this component off ebay or aliexpress as should anything go wrong, a replacement battery is not cheap!

I can upload photos of the charger if it would be of any help.

Thanks in advance!

 

The trim pot will not be on the 230V side so it will be ok.
You could change the series resistor instead of the trim pot, but a look at the circuit is needed to work that out.

 

Thanks dendad. Photos attached. I'm always open to easier options. While I can't foresee the need, it'd be nice to be able to tweak it back up if the need ever arose.

 

Make sure the power is off for a bit to discharge everything first.
With the trim pot turned to MAX volts, and you please measure the resistance across the "R46-1" pads?
Then, repeat for MIN volts.

 

Max 15.9

Min 16.4

Edit: typo on min value

 

Do you mean 15.9K and 14.6K?
If so, solder a 220K resistor across the R46-1 pads.
It should now read 14.8K to 13.7K if I have it worked out ok.

Now, measure the output volts range to see if it goes down more.

Just as a safety measure, I usually apply a couple of layers of wide tape over the mains end of the power supply.

 

I measured it again this morning and it comes up as 16.54k at min voltage, 16.10k at max voltage.

R46 is terminal 2 on the trimpot and R46-1 is a terminal on what I think it's an optocoupler/optoisolater (IC2 on top)

You're saying to solder another resistor on the underside of the board bridging these two?

 

It is a bit hard to see the circuit bit I think R46-1 is an adjustment.
But,going by the typo, the values were the other way around.
Adding a resistor would raise the voltage, not lower it, if my idea is correct.

You're saying to solder another resistor on the underside of the board bridging these two?

Yes, that was the idea. It may still be worth a try and measure the voltage range, just to see if it does alter as I expect.
Can you have a go at tracing the circuit out?