Volts but no amps?

BobnLesley

BobnLesley

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We have a NASA Marine BM-1 Battery Monitor, which I think, or at least hope, has a problem; I've emailed NASA, but now realise that with the time difference, it was about 5:00pm Friday with them by the time I sent it and I'd like to get on with the problem over the weekend, rather than await a response on Monday:

The unit's been on the boat 6 years at least and always seemed to work fine, this morning I look at the display and it tells me there are 0-0.1 amps going into our batteries from the solar panels; the unit's never read the amps in via the alternator (I think that's the norm) but never a problem showing solar-panel input amps. So it's toolboxes and multimeter out and I've checked through the whole solar panel system, I've even fitted a spare charge controller; all seems good, there's definitely volts going into the battery (the Monitor/Multimeter both say 13.3v just now and the Monitor's %-full reading's gone up steadily all morning. When the fridge motor or anything else kicks in, the monitor shows amps discharging, but between times it continues to show 0 - 0.1 amps charging.

Any ideas?
 
BobnLesley said:
We have a NASA Marine BM-1 Battery Monitor, which I think, or at least hope, has a problem; I've emailed NASA, but now realise that with the time difference, it was about 5:00pm Friday with them by the time I sent it and I'd like to get on with the problem over the weekend, rather than await a response on Monday:

The unit's been on the boat 6 years at least and always seemed to work fine, this morning I look at the display and it tells me there are 0-0.1 amps going into our batteries from the solar panels; the unit's never read the amps in via the alternator (I think that's the norm) but never a problem showing solar-panel input amps. So it's toolboxes and multimeter out and I've checked through the whole solar panel system, I've even fitted a spare charge controller; all seems good, there's definitely volts going into the battery (the Monitor/Multimeter both say 13.3v just now and the Monitor's %-full reading's gone up steadily all morning. When the fridge motor or anything else kicks in, the monitor shows amps discharging, but between times it continues to show 0 - 0.1 amps charging.

Any ideas?
Click to expand...

Is the shunt ok? All tight there?
S
 
BobnLesley said:
We have a NASA Marine BM-1 Battery Monitor, which I think, or at least hope, has a problem; I've emailed NASA, but now realise that with the time difference, it was about 5:00pm Friday with them by the time I sent it and I'd like to get on with the problem over the weekend, rather than await a response on Monday:

The unit's been on the boat 6 years at least and always seemed to work fine, this morning I look at the display and it tells me there are 0-0.1 amps going into our batteries from the solar panels; the unit's never read the amps in via the alternator (I think that's the norm) but never a problem showing solar-panel input amps. So it's toolboxes and multimeter out and I've checked through the whole solar panel system, I've even fitted a spare charge controller; all seems good, there's definitely volts going into the battery (the Monitor/Multimeter both say 13.3v just now and the Monitor's %-full reading's gone up steadily all morning. When the fridge motor or anything else kicks in, the monitor shows amps discharging, but between times it continues to show 0 - 0.1 amps charging.

Any ideas?
Click to expand...
Hang on, it doesnt show the alternator amps in? Then you havent got it wired up properly.
One end of the shunt goes to the battery negative and everything goes to the other side!
S
 
At 10Amp setting, multimeter says zero (not even a flutter), I'm not sure if I believe that; how can I be putting volts in but no amps?

All shunt cabling and connections seem good/secure and are not changed from original/pre-problem fitment: Black white & a heavier cable going to a battery negative on one side. Yellow plus a heavier cable to the earth bus-bar on the other side, then a separte red from the monitor's harness to the battery positive.
 
BobnLesley said:
But it does still show amps going out which is what's really confusing me?
Click to expand...

If it's showing amps out when the fridge comes on, but no amps from the solar controller otherwise, i doubt you're getting any output from your solar setup.

You can get volts with no amps, just means no current flowing. Besides, the volts will be battery volts anyway. Disconnect the solar wiring at the batteries and stick the biggest bulb you have on the wires, if it light up bright you have some current, if not.......

Connect the bulb to the controller output, if it lights the fault is in the wire from the controller to the battery. If not, keep checking at every connection until you find where it lights up, hence where the fault is. Bare in mind that when you get to the input side of the controller any anywhere back to the panels you could have more than 12v, so be prepared to lose a bulb, maybe.
 
PaulRainbow said:
If it's showing amps out when the fridge comes on, but no amps from the solar controller otherwise, i doubt you're getting any output from your solar setup.

You can get volts with no amps, just means no current flowing. Besides, the volts will be battery volts anyway. Disconnect the solar wiring at the batteries and stick the biggest bulb you have on the wires, if it light up bright you have some current, if not.......

Connect the bulb to the controller output, if it lights the fault is in the wire from the controller to the battery. If not, keep checking at every connection until you find where it lights up, hence where the fault is. Bare in mind that when you get to the input side of the controller any anywhere back to the panels you could have more than 12v, so be prepared to lose a bulb, maybe.
Click to expand...

But if no current's flowing, why does the battery voltage (as measured by both the monitor and multimeter) increase when the solar array is connected? Similarly, through the course of the day, the battery monitor's %-full column has gone up too.
 
LadyInBed said:
You say you have a multimeter. If it has a 10A facility, how many amps does that say is being delivered?
Click to expand...

Dug out another multimeter:
On the panel side of the charge controller it reads around 8-9 amps, given today's sun/cloud conditions, that's about what I'd expect our panels to deliver and the Battery Monitor to show. On the battery side of the controller it shot up to 18-19 amps (presumably coming from the batteries) in the 1/2 second before I whipped it back off again (with very warm wires)

Full sun just came back out and it read 18-20 amps on the panel side too.
 
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I think these units (I have a Philippi) can become 'confused' try disconnecting both batteries charging them fully using a battery charger and resetting the monitor...there are complicated calculations that 'guess' at voltage. I am 'not sure this will solve the problem good given your description worth a try and certainly will not do any harm.

Still, it baffles me that it doesn't show alternator charging current.
 
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BobnLesley said:
It does show the volt increase from the alternator, the monitor reads 14.2/14.3 with the engine running, what doesn't and has never registered are the 30+ amps that are clearly going in.
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Then it is wired incorrectly as the shunt should be the last connection between the battery bank and everything else that goes in or out. Have you got anything (including the alternator) attached to any negative battery terminal?
 
BobnLesley said:
It does show the volt increase from the alternator, the monitor reads 14.2/14.3 with the engine running, what doesn't and has never registered are the 30+ amps that are clearly going in.
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This will be because it sees the voltage increase at the domestic bank, where it is connected, but does not see the current (amperage) because the engine battery negative is not connected to the shunt.
 
RupertW said:
Then it is wired incorrectly as the shunt should be the last connection between the battery bank and everything else that goes in or out. Have you got anything (including the alternator) attached to any negative battery terminal?
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I'll try re-wiring the whole system from scratch tomorrow - it was probably installed originally by Greek 'professionals' (don't get me started on that issue!), but there's definitely nothing wired from a negative pole; the system's powered by a bank of four Trojan batteries, which give me two 12V feed poles and everything (including the battery monitor's red wire's) goes back to one of those, apart from the alternator connection and fridge supply which connect to the other; the battery monitor definitely sees/reports the fridge's ampage draw.
 
BobnLesley said:
I'll try re-wiring the whole system from scratch tomorrow - it was probably installed originally by Greek 'professionals' (don't get me started on that issue!), but there's definitely nothing wired from a negative pole; the system's powered by a bank of four Trojan batteries, which give me two 12V feed poles and everything (including the battery monitor's red wire's) goes back to one of those, apart from the alternator connection and fridge supply which connect to the other; the battery monitor definitely sees/reports the fridge's ampage draw.
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What are you using for starting the engine ?

Where does the heavy negative cable to the engine connect ?
 
We have a BM1 on our boat , also on our last boat , and if it wired right , and working correctly, then it will show solar panels and alt Amps in and what's going out . Has others have said , check your wiring
 
Actually, alternator output not showing on the battery monitor is a distraction. It has no bearing on the solar output not showing. My alternator output does not show on the battery monitor because i'm monitoring the domestic bank, not interested in the engine battery, apart from keeping an eye on the voltage. My windlass runs from the engine battery and if i connect the engine and windlass negatives that and alternator charging will cause confusion for the battery monitor SOC. I prefer to ignore the engine and windlass and ignore the alternator charging, as i run the engine infrequently and my batteries are mostly charged by solar, with some mains topping up in the Winter, which does go through the battery monitor.

Although there seems to me to be something odd about the system it has presumably been working thus far. But i'd like to hear a bit more about how it's all setup.

What starts the engine ?
How are the different battery banks charged, VSR, diode etc ?
Where is the engine negative connected ?
What isolator switches are being used ?
 
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