NASA BM1 Negative cable size

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Scubadoo

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Just fitted last weekend NASA BM1 battery monitor, installed no problems and seems to be working fine. My only question, the black negative cable supplied that connects to the Shunt and the Battery terminal looks a lot thinner than my existing battery negative cables. Should I be concerned and consider installing a larger diameter cable to match my existing negative cables, or what have others done. Mine is a simple set-up 1 x 125amp battery (leisure), the starter battery is not connected to the BM1.
 
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Scubadoo said:
Just fitted last weekend NASA BM1 battery monitor, installed no problems and seems to be working fine. My only question, the black negative cable supplied that connects to the Shunt and the Battery terminal looks a lot thinner than my existing battery negative cables. Should I be concerned and consider installing a larger diameter cable to match my existing negative cables, or what have others done. Mine is a simple set-up 1 x 125amp battery.
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The cable supplied should be heavy enough for the max current rating of the monitor (100amps IIRC for a BM1, 200amps for a BM2) but they are really intended to be used on just the house battery of a two battery set up.
 
VicS said:
The cable supplied should be heavy enough for the max current rating of the monitor (100amps IIRC for a BM1, 200amps for a BM2) but they are really intended to be used on just the house battery of a two battery set up.
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Perhaps I should have said I have 2 x batteries (leisure and starter), only the leisure battery is connected to BM1.
 
Scubadoo said:
Just fitted last weekend NASA BM1 battery monitor, installed no problems and seems to be working fine. My only question, the black negative cable supplied that connects to the Shunt and the Battery terminal looks a lot thinner than my existing battery negative cables. Should I be concerned and consider installing a larger diameter cable to match my existing negative cables, or what have others done. Mine is a simple set-up 1 x 125amp battery (leisure), the starter battery is not connected to the BM1.
Click to expand...

Though the cross section should be large enough for the low current the NASA shunt can cope with, the supplied link is very unworkmanlike in my view, I fitted one recently for a customer and threw it away in disgust and made up a decent one.
 
David2452 said:
Though the cross section should be large enough for the low current the NASA shunt can cope with, the supplied link is very unworkmanlike in my view, I fitted one recently for a customer and threw it away in disgust and made up a decent one.
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So what in your opinion constitutes a decent one ?
I'm installing mine this weekend and had similar concerns as the OP.
Thanks
 
David2452 said:
Though the cross section should be large enough for the low current the NASA shunt can cope with, the supplied link is very unworkmanlike in my view, I fitted one recently for a customer and threw it away in disgust and made up a decent one.
Click to expand...
:encouragement:
 
3 people who seem to know what they are talking about tell us that the provided size is inadequate, but details on what is adequate would be very helpful.
NASA suggest 25mm2..............!!

Any thoughts
 
From the feedback so far and a quick google search, I get the impression that because of the very short length of cable it is adequate for 100amp Shunt, but not easy to install because you have very little cable to play with. So Pladdatoo I think you can work with what comes in the box, but you may find it troublesome locating the Shunt with such a short cable.
 
Pladdatoo said:
So what in your opinion constitutes a decent one ?
Click to expand...

Long enough to site the shunt conveniently and securely, i.e. where you want it instead of within the (very short) restriction of the supplied lead, also though, as I said earlier the cross section will cope with 100a I upped it to a convenient length and to 35mm2 cable in order to securely mount the shunt, this would not have been possible in either case using the supplied lead. I have seen them installed with the shunt hanging loose because of the restriction, frankly it would be better left out of the box then people wouldn't be tempted to do that. These were customer supplied, I would normally use Victron so this problem does not normally arise for me.
 
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"Originally Posted by Cantata
That cable size is fine for the normal loads taken from your leisure battery.
But I too have wondered about that cable, if the circumstances were such that I wanted to start the engine off that battery. Maybe worth a call to NASA and ask them."

You make an interesting point and not something I had considered. I have a link switch to link my starter and leisure battery in the event the starter battery is flat to start the engine. I emailed NASA and here is their response: The cable supplied is rated in excess of 100 Amps load so as long as you do not exceed this it is perfect for intended purpose. It and the shunt will withstand much higher loads for short duration so if engine fires quickly we cannot see it being a problem.
 
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