Who sells heavy duty shunts?

[fridayman]

I am looking for a 300A 100mV shunt with an insulated base?

 

[Crispin]

I found lots on flesbay, cpc and rs.

Sent from TapaTalk

 

[Chris]

And what exactly does that do?

I might want one too. Well I might! In fact I might order 2. So there.

No really, huh?

Enlighten please.

Chris


Ahh, just read your other post. Decided now that I don't think that I really want a shunt. They're not for me. Not unless they come on cammo.

 

[fridayman]

There are few places that do shunts like cpc, rs, etc but not the size that I am looking for. Found a place in the US, but they have a minimum order limit of $75 +shipping.

 

[Crispin]

I found some 400A 75mv shunts. Ok if you always using high current but I only wanted that high to handle the starter. Rethinking to bypass starter and only measure everything else.

Chris, a shunt is a resistor with a very small value, it allows you to measure very high current by measuring the voltage drop across it. The one fridayman is looking for would give you 100mv @400A.

You connect it between source and load and measure the voltage across it. You'll need more than two. One for each wheel

 

[fridayman]

I need it for a Reya battery monitor that only cam e with one shunt,and I need two. The one it came with is a 100mV, so I assume that for the monitor to work I will need another one that is the same. If I am wrong please let me.

 

[fridayman]

Actually, thinking about it... what is the maximum current that I am likely to draw from a starter battery for starting? And if I linked it for winching? Maybe I don't need a 300A shunt..?

 

[Crispin]

I asked it on another thread somewhere. My starter (120) is apparently a 2.7KW jobbie. Assuming that is electrical power and not Rob's suggestion of mechanical, then 2700/12 = 225A. That is turning at full load. The initial current, as it overcomes the inertia in the engine, would be much higher. For winching, I think it would be a bad idea. When you stall a winch, it would basically be a short across the battery.

I would expect most shunts would be able to take a surge current but can't offhand see on CPC what they would be rated at. I would guess a few multiples.

 

[Rob]

Assuming that is electrical power and not Rob's suggestion of mechanical, then 2700/12 = 225A.

At work I deal with electric motors on a daily basis, which includes dyno testing and analysing dyno curves. Although I have not been there long I have never come across a motor rated at electrical power and all the catalogues I have looked at are in mechanical power.

A peak efficiency of 60% is common in a LVDC (low voltage DC) motor. However what we don't know is how much mechanical power is needed to turn the engine over and so it is difficult to tell how much current is drawn.