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Seem to be using more power than I thought


Bewildered

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And therein lies the reason :)

I am wondering why you want to do this other than, "because it's there".

Why not get the BM2 and Smartguage working, see what's going on with your batteries, and don't risk blowing things up?

Yes therein does lie the reason, it is there and it stares me in the face doing nothing.

It is an instrument on the panel directly in front of me while steering the boat, if I can get it working without causing problems I would obviously like to. This is why I asked the question, will it cause problems?

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The resistance of the shunt has to match the ammeter. There is no guarantee that it would. Also if you put another device across the shunt (the ammeter) it might affect the accuracy of the BM2 especially if it is a fairly low resistance device like a mechanical ammeter. But anyway the BM2 gives you amps so why would you need another ammeter?

 

If it uses a shunt it will not be an ammeter in construction although it may be calibrated in amps. It will be a millivolt meter so even if mechanical will have a high resistance. How high compared with a digital instrument I have not idea. However I agree it probably not wise to have the two on the same shunt.

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If it uses a shunt it will not be an ammeter in construction although it may be calibrated in amps. It will be a millivolt meter so even if mechanical will have a high resistance. How high compared with a digital instrument I have not idea. However I agree it probably not wise to have the two on the same shunt.

I could be pedantic and ask what is the difference between an ammeter and a millivoltmeter since they both in fact measure current :lol: but anyway yes I agree that the (mV/am)-meter is likely to have fairly high resistance. However the BM2 will be using electronic sensing with probably much higher resistance

Edited by nicknorman
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The resistance of the ammeter/mVmeter will be many factors higher than that of the shunt and hence is unlikely to make a measurable difference to the BM's reading. However, it's also unlikely to be matched to the BM's shunt value and will be therefore most unlikely to give a meaningful reading itself.

 

If you have found the old shunt then why not use that for the meter? There is no problem with having two shunts as long as the connections are all good.

 

Tony

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Yes therein does lie the reason, it is there and it stares me in the face doing nothing.

It is an instrument on the panel directly in front of me while steering the boat, if I can get it working without causing problems I would obviously like to. This is why I asked the question, will it cause problems?

If it's the fact that you have to look at a meter that's not working, but you don't need another ammeter, change it for a clock - at least it will work and be useful.

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If you must use the old ammeter along with the BM2, then ensure the two shut to are in series, so that the current flowing through both will be the same, and thus they can't affect each other.

 

Well, yes. I didn't mention this because I thought it was obvious, but perhaps not to everyone.

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I think I will give up on the idea for now. I really can't be bothered will fitting another shunt.

 

Found it interesting that the battery strap for the shunt that came with BM2 was only 8" long; this means that they expect you to mount the shunt within 4-5" (allowing for bending the stap etc) of the batteries negative terminal. Ok if your battery is adjacent to a bulk head that you can fix the shunt to and your battery's negative terminal happens to be that side of the battery, pretty useless if not.

Fortunately I had a couple of spare 12" battery straps that I bolted together (heavily taping up the join) until I can get around to buying an appropriate one.

Why do they supply it with such a useless bit of kit in the box? They would be better of not bothering and instead stating on the box "strap not supplied"

Although if I ever do fit the second shunt the stupidly short strap may come in handy

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I think I will give up on the idea for now. I really can't be bothered will fitting another shunt.

 

Found it interesting that the battery strap for the shunt that came with BM2 was only 8" long; this means that they expect you to mount the shunt within 4-5" (allowing for bending the stap etc) of the batteries negative terminal.<snip> Why do they supply it with such a useless bit of kit in the box? They would be better of not bothering and instead stating on the box "strap not supplied"

 

I would imagine that they intend you to remove the lead from Domestic -ve to the bonding stud, connect that lead to the shunt, and connect the new strap to the stud - only a few inches of cable required. If your starter battery -ve currently goes to the domestics, then remove it from there and connect it to the same bonding stud.

 

Tony

Likewise, if your distributed -ve is currently connected to the domestics -ve post, reconnect it to the bonding stud.

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I installed the BM2 earlier this week but I'm a little confused at the battery temperature reading.post-23755-0-13066300-1473273070_thumb.jpeg

95 degrees seems a tad high.

When I fitted the BM2 I also got around to fitting the temperature sensor for the Tracer solar controller that I fitted last week.

post-23755-0-50941000-1473273248_thumb.jpeg

All I did was run the probe to the batteries and wedge it in between two of them and plug the other end into the Tracer unit

So on the one hand we have the BM2 that only takes a guesstimate at the temperature at 95 degrees and then we have the Tracer that has a probe fitted actually measuring it at 28.6

The instructions for the BM2 say how to enter the engineering mode and set the approximate temperature. I just took a look and it is set at the default 20 degrees

Had a good run today and fully charged bank, these readings are taken at least an hour and a half after stopping for the day.

Can anyone shed light on why the BM thinks my batteries are steam powered?

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  • 2 weeks later...

Finally worked out the culprit was the freezer. Bought it new in February direct from Shoreline, it is the small TF35 model.

We noticed that it seemed to run for longer periods than it ought to; as it is located behind the bulkhead from the bed we took to turning it off overnight.

After fitting the BM-2 I spent time working out what draws what, the freezer drew around 3amps continuously. I ended up sitting next to it with a book for a couple of hours and the thermostat never kicked in once. I had pulled the freezer out from the cupboard it was housed in to make sure there was plenty of air circulating around the cooling fins during this test. I noticed on one side a circular patch of condensation about 3 inches in diameter that was freezing cold to touch. Obviously a spot that was not insulated properly during manufacture.

 

I rang Shoreline and explained the problems I was having, they sent out an advance replacement that day. So I can't fault Shorelines customer service.

 

I still think I will be turning the freezer off over night though. It is insulated and as it won't be opened at night will happily stay frozen until I switch it on in the morning during the daily battery re-charge.

 

The back of the frezzer has terminals on it to fit a 12v fan; I assume this will cut in when the compressor is running the idea being to blow cool air over the cooling fins to help dissipate the exchanged heat faster.

What sort of fan would be best for this? Does it actually save power?

If the freezer draws 3amps and a fan adds say another 1/2 an amp, does the freezer actually run for a shorter time that would justify the extra load necessary to run the fan?

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