Battery monitors

[sabconsulting]

I'm looking to replace my cheap Chinese volt / ammeter with a proper battery monitor that can integrate charge / dishcharge current in order to estimate Ah used / available.

Current thinking is Victron BMV-700 (about £130) - manual looks comprehensive, very sophisticated bit of kit
Or NASA-Marine BM-1 Compact (about £100) - British built, but looks less sophisticated, plus comes with lower amperage shunt. But would be easier for me to install.

Anyone got any thoughts / recommendations?

Cheers,

Steve.

[Gary W]

I'm looking to replace my cheap Chinese volt / ammeter with a proper battery monitor that can integrate charge / dishcharge current in order to estimate Ah used / available.

Current thinking is Victron BMV-700 (about £130) - manual looks comprehensive, very sophisticated bit of kit
Or NASA-Marine BM-1 Compact (about £100) - British built, but looks less sophisticated, plus comes with lower amperage shunt. But would be easier for me to install.

Anyone got any thoughts / recommendations?

Cheers,

Steve.

Victron, Sterling and NASA all fine Steve, but what about something really special? Take a look at the Merlin 'Smart Gauge'.

It must use magic or something because somehow, without a shunt and with just 3 simple connections, it's test results consistently show it to be one of the most accurate monitors around. You don't hear much about Merlin, they're mostly military and emergency services suppliers, but being just up the road from us we discovered them almost by accident and they do a lot of stuff that works well with adventure campers too. I don't know if they will supply the consumer directly but if you have any trouble just let me know and you can do it though us.

Best wishes

Gary

[saDgit]

Hi Steve,
I fitted a Victron BMV-600 (I presume that's the series before the 700?) into our Great West Van at the same time as I installed a couple of 125ah batteries and an 80-watt solar panel dedicated to running the compressor fridge (Waeco CR110). Installation of the Victron was fairly straightforward and it's certainly a VERY sophisticated bit of kit, much more sophisticated than I need if I'm honest, but it does seem to be reliable and I believe it's accurate as long it's occasionally synchronised. It's also a very neat and unobtrusive gauge.

I have it set up so that, at the press of a button, the gauge will cycle through voltage, amps in or out, amp/hours used, % state of charge, and (probably least accurate but most useful in some ways) the number of hours the system could sustain at the current level of demand and input. At some point I shall need to fit something similar into my demountable and I'd certainly be happy to go with Victron again.

[sabconsulting]

Interesting tip about the SmartGauge Gary.

I too struggle to see how that works having half the information available to it that the other monitors have.

http://www.smartgauge.co.uk/index.html

I do have a concern that using mathematical models and measuring only voltage and time might work well on simple installs, but I'm not sure how well it would cope with my power usage. I might be plugged into the mains at some points and a CTEK mains charger will be charging the battery, at the same time things like lights, pumps, etc. are draining the battery. At the same time the DC250S may be providing extra charge from the solar panel. Then once off mains the compressor fridge will be switching on and off and the solar and or alternator may or may not be providing some current to the battery.

I found this comment on another forum, which didn't reassure me:

It is more appropriate to batteries that are regularly charged to 100% Such as happens with shore power. Off grid where soc fluctuates widely due to shorter charging times not giving 100% and multiple charging sources the poor thing just hasn't got a clue. Gibbo told me the reason I got the wrong readings off the smartgauge was because I undercharge my batteries. I do, it's a decision I make, not an ignorance. In those circumstances it was wildly inaccurate. . It is my opinion that it doesn't cope very well at all with solar. It also struggles with 0-1-2 battery switches. The thing it really couldn't cope with was my use of a laptop while the sun was shining.

Also, without a shunt I cannot measure the amps going into or out of the battery, which is something I like to check regularly - so I can see how much I am really drawing at any point in time.

And I think dimensionally the SmartGauge is a bit big for where it needs to go.

So I'm not saying 100% no, but I am a bit sceptical that it is right for me.

The Victron is probably in the lead at the moment. But I'll do some more research - it isn't hugely urgent.

Cheers,

Steve.

[Toshbins]

I have NASA Clipper monitor on the boat. Very clear and easy to use. ~The compressor fridge does cut out before the batteries are exhausted as far as percentage charge is concerned as the voltage drops too low. Having said that the batteries are getting on a bit (Had the boat 5 years and no idea how old the batteries are).

[sabconsulting]

In the end I went for the Victron battery monitor. Fitted it last night. Looks good so far. Can set an alarm on the state of charge (warning you if it drops too low). And can cycle between voltage (to 2 decimal places), amps going in or out, % state of charge, watts and estimated hours remaining at the current battery drain rate.

I have also made the move to an AGM battery - a Rolls 105Ah battery. I could fit a physically bigger battery by mounting it on its end. Rolls (like some of the other higher quality AGM battery suppliers) publish a graph showing the number of charge / discharge cycles the battery should accept before it fails plotted against the depth of discharge each cycle is to. The Rolls, like with another AGM manufacturer showed a graph indicating the battery was capable of being discharged to only 20% remaining charge over 500 times before it dies. Flooded cell leisure batteries that quote this will often say the battery will only support maybe 50 to 80 cycles down to 50% charge.

So let's see how we get on with the AGM battery.

Cheers,

Steve.