Nasa Battery Monitor

[Sniper]

I have today installed one of these and although it appears to be functioning I am a bit confused by it. It registers charging voltage and amps without any problems and will also give me values for charging times to reach peak battery capacity. However, I can see no values for useage (?current draw) when I switch a range of items on (radio, depth sounder, GPS, log, nav lights) and no estimate for percentage of battery charge remaining. The amps being drawn remains at 0.1 and the percentage meter remains at 0.

The instructions told me to wait 'a few minutes' to allow the meter to 'learn' the battery, which I did. How many is 'a few' and is this likely to be the root of the problem I am experiencing? The other thing that confuses me is that even with the engine off it displays the legend 'charge' when I would expect 'discharge'. I should say that this is on a brand new 85ah battery which I had on a trickle charger for 24 hours beforehand.

Any views appreciated.

 

[CPD]

If you see charge when you would expect to see discharge then it vccould be you have the wires that measure voltage drop over the shunt wired the wrong way round.

 

[VicS]

Are you sure the negative connection for all the items you mention comes from the correct side of the shunt. Only the black and white wires from the monitor must go to the battery side of it. All charging and load must be connected to the opposite side together with the yellow wire.

you say its showing charging current Ok so there must be some reason why the load current is not passing through the shunt.

 

[ga1135]

Have you "Tell" the unit that you have a 85AH bank?

 

[Sniper]

I'll double check my wiring. It has my tiny brain a little exercised since I have the classic 'two batteries and a three way battery switch' set-up, so it is possible that the shunt is the wrong side of the load. I did set it up to measure a 85ah battery.

Thanks all.

 

[VicS]

[ QUOTE ]
since I have the classic 'two batteries and a three way battery switch' set-up

[/ QUOTE ] potential for a few pitfalls there. How have you wired the BM1 up to it.
Just got the shunt in the negative to one battery? If so is the load on the other.
Got the shunt in the common negative? Thats no good is it?

 

[Eccles]

The BM1 will only monitor 1 battery - typically the service battery.
the shunt must be between the common -ve and the -ve of the service battery.
The +ve of the BM1 must be on the +ve of the service battery.

If you switch things on with the changeover switch on Engine battery the BM1 will not register this load!

I hope this helps.

 

[MacMan]

[ QUOTE ]
The BM1 will only monitor 1 battery - typically the service battery.
the shunt must be between the common -ve and the -ve of the service battery.
The +ve of the BM1 must be on the +ve of the service battery.

If you switch things on with the changeover switch on Engine battery the BM1 will not register this load!

I hope this helps.

[/ QUOTE ]

I am not being pedantic for the sake of it - but just in cases it confuses anyone else. The BM1 will happily moniter one *bank* of batteries containing many batteries. It's been monitoring 2 * 110AH in my domestic bank for the last year quite happily. What is does not do is measure multiple banks. In my set up I have a starter battery which is left completely un monitored.

If you want to measure two *banks* you either need 2 BM1's or more sensibly a more expensive monitor which copes with two banks at the same time.

Also in an attempt to be helpful I have an old 1-2-3-Off switch and it cope with this perfectly if you follow the wiring diagram in the instructions.

Also the "minutes" is to calibrate the time to charge/discharge estimates - the Volts and Amps in/out should be nearly instant. If wire correctly.

 

[Phoenix of Hamble]

Second Macman... thats exactly how we've implemented it too, and it works very well.

 

[Eccles]

I was trying to keep it simple.
Up until last month ours was set up with 1 engine and 1 service battery.

I have just added a second service battery to create a bank.
both scenarios work fine as long as you keep clear in your wiring where the BM1 sits in the curcuit be it single battery of a bank.

 

[ga1135]

FYI, I use the M1 to monitor my 3 batteries for few years and it works well.

Set up as below :
* 1-2-Off main switch with +ve switching
* 2 x 85 Ah service batteries connect to switch 1
* 1 x 75 Ah separe battery (not starter, just idle as sapare) connect to switch 2
* Connect all batteries -ve to a singlw cable -> shunt -> service panel
* Tell M-1 that I have 170 Ah bank.

It measure switch 1 group well. I seldom use switch 2, I only check volt & level for it occasionlly. If I need to use it for long, I will tell M-1 of the changes in total Ah valve.

 

[[10753]]

I've just bought one of these - yet to install - glad everyone likes them !

 

[James_Hortop]

Be careful using with a 1, 2, both and off switch or with systems with an emergency battery parallel feature. The shunt is rated at 100A only - be careful not to overload it (thats a 1.2Kw starter motor max). Be careful of other high load devices (inverters, windlasses etc) as they will have the same affect).

 

[VicS]

[ QUOTE ]
The shunt is rated at 100A only

[/ QUOTE ] I think we have been over this one before. IIRC someone contacted Nasa and was told that the 100amps could be exceeded.
Perhaps it was for short periods for a starter motor and
perhaps the 100amp limit is the max current that the instrument will display but it will record the load correctly and the shunt will withstand a higher current than 100A. Dont remember what though

Perhaps someone else can remember.

perhaps I'm wrong again.

 

[Phoenix of Hamble]

it was 300A long enough to start an engine....

 

[VicS]

But you do have to bear in mind that starter motors are rated by their mechanical output. The electrical consumption will be greater.

For example you'd assume that a 1.1hp (800watt) motor would draw 67 amps but in reality it will draw 30 - 50 amps at a terminal volts of 11.5 when not loaded. 185 - 220 amps at a terminal volts of 9 volts when cranking and as much as 400 - 480 amps at a terminal volts of 7 when stalled.

(Data for a Bosch motor on Volvo Engine)

 

[Sniper]

Just an update for anyone interested; I swapped the neagtive leads around a bit and the monitor seems to work fine now. It is quite illuminating just how little draw there is from having the radio, depth sounder and log on - less than 1 amp.

As a final query, when I turn the batteries off the monitor records a charge of 0.1 amp at 13.5 volts. I assume the service and starting batteries are somehow equalising themselves across the negative terminals?

 

[Phoenix of Hamble]

you can tune this out.... can't remember which key strokes are required... but if you have everything switched off it needs setting to zero (or you have something still consuming current somewhere!).... the manual explains how

 

[Chris_Robb]

I contacted NASA and they were quite happy with the shunt passing the load of the starter for occaisional starting. They did say that if you were churning the engine, for a long time, it was not a good idea.

I do start it (VP2003T) on House batteries when I forget - which is quite often!

 

[southace]

nasa

One thing I hate is the led lighting goes out on a timer its a real pain in the lard!