drew_greenday

Senior Member
VIP Member
T6 Guru
I'm thinking of getting a battery monitor for my van. It would be good to see what sort of load i'm using when out and about, will also give an indication of how long left. Was specifically looking at the Nasa Marine BM-1 Clipper Battery Monitor. The only thing thats putting me off is the price tag.

Does anyone have a battery monitor, i've seen some Chinese ones on the bay that look ok. Do I get one if these or just a standard voltage output?

Thanks

Andy
 

xpfloyd

Senior Member
VIP Member
T6 Guru
Personally I wouldn't bother. I just installed a LED voltmeter wired to a switch. I can just flick it on to check the current voltage of the second battery. When camping I just check that every so often
 

andys

Senior Member
VIP Member
T6 Legend
I had a Nasa BM-1 in my last van. Was much more accurate than the cheap LED ones I'd tried and I generally found it useful. The shunt that goes across the battery terminals was quite bulky so make sure you have the room if the battery is squeezed under a seat. Don't have one now cos those functions are built in to the Westfalia control computer
 

travelvolts

Auto Electrician
Trade Member
T6 Legend
You won't get an accurate battery monitor for less than £100. If you just want one to give you an idea of state of charge then you would be better off with a graduated scale type meter rather than a volt meter. Unless you know the accuracy of a volt meter and understand what the displayed voltage means then they are next to useless.
 

t0mb0

Senior Member
VIP Member
T6 Guru
Do those Votronic units (and the Nasa BM1) estimate battery capacity solely by integrating up current flow over time? Do you need to input the Ah capacity of your battery to start with and/or do some kind of periodic calibration? Or do they have some internal model of voltage response that allows them to automatically calibrate themselves?
 

drew_greenday

Senior Member
VIP Member
T6 Guru
Do those Votronic units (and the Nasa BM1) estimate battery capacity solely by integrating up current flow over time? Do you need to input the Ah capacity of your battery to start with and/or do some kind of periodic calibration? Or do they have some internal model of voltage response that allows them to automatically calibrate themselves?


When you set up the battery monitor I think you input the ah of the battery, then I imagine the current draw would be divided by the total capacity of the battery and displayed in a time. Someone on here with one might correct me though.
 

t0mb0

Senior Member
VIP Member
T6 Guru
When you set up the battery monitor I think you input the ah of the battery, then I imagine the current draw would be divided by the total capacity of the battery and displayed in a time. Someone on here with one might correct me though.

Yeah, I just had a peek at the instructions online. It does need calibrating whenever it's first (re)connected by fully charging the battery so it must work solely by accumulating current. I assume a slow error will accumulate over long periods of time but I guess you could always reconnect and recalibrate it once in a while if it became suspect.
 

Andy Cody

Member
Yeah, that's right. I've taken mine down as far as the components in the van (fridge, heater etc) will allow and then taken it back up to 100% and it seems to be accurate. Like you said, I'm not sure how much error to expect over time but it's no problem to unplug it when I'm giving the battery a cycle with the home charger every now and then.
 

drew_greenday

Senior Member
VIP Member
T6 Guru
Think I will get a Votronic one as thy look a lot smarter than the NASA BM-1 units. RoadPro haven't got back to me so might ring them tomorrow and see.
 

travelvolts

Auto Electrician
Trade Member
T6 Legend
All the shunt based monitors will have an error over time. The only monitor that gets more accurate as time goes on instead of less accurate is the Merlin SmartGauge.
 

Ads_Essex

Local lowlife
Moderator
VIP Member
T6 Legend
Has anyone got any experience of either the
Simarine monitor
FACBF5B4-FD9E-45AB-A972-0CC0CB7EBFB9.png

or the
BMPro monitor
F9D6D855-9086-4936-B027-CCFCEABD57D8.png

Both look very smart. And pricy.
Quite VW like, I guess then.
 

Ads_Essex

Local lowlife
Moderator
VIP Member
T6 Legend
Cheers, Martyn. I did have a look at the Merlin stuff before posting.
I suppose I should have started a new thread on ‘one size fits all’ monitors which incorporate power and water.
 
Top