On 2022-04-28, Bret Cahill <bretcahill@aol.com> wrote:
> Guessing that there was no clever end run around the 30v maximum I tried a DC to DC converter set to 15v then measured the voltage between the +38v and the +15v.
>
> Instead of 23 v it jumped around all over the place then settled on 3.x v.
>
> A cap between the terminals might not work either and may due to the fluctuating current short out the converter.

buy a better $3 voltmeter:

  https://www.aliexpress.com/item/4001035064897.html?spm=a2g0o.productlist.0.0.3ec85061Xtfaf4&algo_pvid=8b55bb0e-88bc-4587-b3e9-abf2fa2c8d6a&algo_exp_id=8b55bb0e-88bc-4587-b3e9-abf2fa2c8d6a-33&pdp_ext_f=%7B%22sku_id%22%3A%2210000013672700960%22%7D&pdp_npi=1%40dis%7CNZD%7C%7C1.84%7C%7C%7C%7C%7C%402101d4a716511737026983704e56e4%7C10000013672700960%7Csea

One of those wires powers the display and wants no more than 30V
the other one measures voltages upto 100V

it may be possible to convert the one you already have to 3 wire operation.

-- 
  Jasen.

> Guessing that there was no clever end run around the 30v maximum I tried a DC to DC converter set to 15v then measured the voltage between the +38v and the +15v. 
> 
> Instead of 23 v it jumped around all over the place then settled on 3.x v. 
> 
> A cap between the terminals might not work either and may due to the fluctuating current short out the converter.

Whoops! It works, at least for an 8 amp converter with a .270 amp load.

The $3 volt meter reads a volt high, but once corrected the voltages add up only losing half a volt somewhere.

Just add 14.3v to get the voltage and remaining range of the ebike.

I will now try a 2 amp converter.

Guessing that there was no clever end run around the 30v maximum I tried a DC to DC converter set to 15v then measured the voltage between the +38v and the +15v.

Instead of 23 v it jumped around all over the place then settled on 3.x v.

A cap between the terminals might not work either and may due to the fluctuating current short out the converter.