Re: Gauge Number from eBay ---- Wiring question, about 24 volt and "bridges" -- update for today


 

Nice USB charger, worthless ammeter. <sigh> ALL the current flowing in and out of the batteries has to go through the ammeter, or it's shunt, to give any meaningful information. Cal's two 80 lb. thrust motors should draw in the neighborhood of 80 amps at full load. That little ammeter could go up in a puff of smoke if abused with that much current. <g>

A shorter link to the gauge:

https://preview.tinyurl.com/yxhon727

On 8/31/2020 8:18 AM, Jove wrote:
Here is the URL for the gurage, for anyone else looking.
https://www.ebay.com/itm/Dual-USB-Charger-LED-Digital-Display-Voltage-Amp-Meter-Voltmeter-Round-Car-Gauge/363000785546?hash=item5484886a8a:g:ipQAAOSwzEdeSFyE Cal,
to me it looks like it's designed that full amps would run through
that, but it is limited to 10A.
I bet there is a low ohm resistor in there calibrated with a voltage
gauge to display as current.
Not sure what your peak running amps is. You could bypass it with a
switch for sure, then just switch the ammeter in when you want to
check. That would prevent it having to tolerate all the current and
heat.
Heat is a function of amps in a device like this, so it's limit is
going to be heat dissipation and overheating, so if you only
switch it in when needed, it will survive a lot more. Perhaps it
will be willing to read higher amps, but if you put 20 amps through
it I bet it will blow after a few mins. It's all about cooling and
time. If the resistor is inside the plastic enclosure it will not
get much cooling, you could cut the back open if you wanted to cool
it more. even add a heat sink to that resistor.
If you're using up 4 of those full batteries in 8 hrs, that would be
one per 2hrs, ~500Wh/ hr. at 24v. =20 Amps, does that sound right?
--
John <jkohnen@boat-links.com>
I have noticed that people who are late are often so much jollier than the people who have to wait for them. (Edward Verrall Lucas)
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