Battery monitor

[NormanS]

I have probably a fairly normal set up with a single 12v battery for engine starting, and a bank of three 12v for services. I would like to fit a battery monitoring system which could show:-

The voltage in each bank. The charge being accepted by each bank. Possibly some idea of the remaining available amphours in each bank. Anything else which you think is desirable.

Has anyone any particular recommendations, or particular makes / types to avoid.

Thanks in anticipation

 

[Paddingtonbear]

Smartgauge. No connection what so ever, don't even own one but are standard kit on most military and emergency vehicals and they are British

 

[Porthandbuoy]

I fitted a 1,off,2 switch and a simple LED panel mounted voltmeter bought off e-bay. Total cost about £15.
With the switch on position 1 it tells me the voltage in the 'house' battery. Position 2 gives the voltage in the engine battery. Both batteries are 110 Ah Elecsols.
Fully charged and rested (isolated for half an hour) they read 12.6V or thereabouts. Elecsol claim 10.7V is fully discharged but I've never been anywhere as low as that.

When running the engine, and the main battery switch in the 'both' position, it tells me the alternator volts at the batteries. When it reaches 14.4V I consider them charged.

I've nothing against a SmartGauge, love one in fact, but they're the price of a new battery.

 

[Barry Jones]

Smartgauge. It will show you the voltage at each bank and the %SOC in the service bank. A lot more accurate than a battery monitor using a shunt and counting Amps in and out.

Very accurate indication of % SOC and takes into account degradation of battery with age.

Also, simplicity itself to fit.

I have probably a fairly normal set up with a single 12v battery for engine starting, and a bank of three 12v for services. I would like to fit a battery monitoring system which could show:-

The voltage in each bank. The charge being accepted by each bank. Possibly some idea of the remaining available amphours in each bank. Anything else which you think is desirable.

Has anyone any particular recommendations, or particular makes / types to avoid.

Thanks in anticipation

 

[NormanS]

Thanks for these responses.

Can you confirm that the Smartguage doesn't actually show the amps being put into each battery bank by the alternator?

It seems to show the voltages and the SOC. Maybe that's enough?

 

[theforeman]

another vote for smartguage - have had one for 2 years - reliable piece of kit.
it does not show the amps in or out. it is recommended that it be wired in such a way that it will show only the voltage on the engine start battery and both voltage and soc ( shown as a %age ) on the house bank.
not sure about your charging system, but i believe that to fully charge a battery you require an alternator capable of charging up to 14.4 volts.
i have used the smartguage in conjunction with a 90amp prestolite alternator, a 550 cca engine start battery and a house bank of 1 x 110Ah + 1 x 100Ah batteries and a 1-1+2-2-off switch.
the alternator could charge either bank up to 14.40v and on 1+2 could charge up to 14.35v.
so far as i can tell the smartguage is highly accurate and really tells you all you need to know.
a dawdle to install - 3 wires connected directly to the batteries and 2 x 3amp in line fuses.
usual disclaimer - no connection etc.

 

[longjohnsilver]

I've installed 2 of these

http://www.campervanstuff.com/shop_stuff/index.php?mod=product&id_prd=1080

and have been very pleased, they are accurate and give me all the info I need to know about my batteries, which is particularly important on a mooring without power.

 

[Barry Jones]

Thanks for these responses.

Can you confirm that the Smartguage doesn't actually show the amps being put into each battery bank by the alternator?

It seems to show the voltages and the SOC. Maybe that's enough?

Correct. Not really necessary. If you want to see Amps, you can get inexpensive digital ammeters off EBay.

Accuracy is the thing and having fitted lots of systems, I believe the Smartgauge SOC reading to be the key.

 

[noelex]

There are not any battery monitors available to do all you want, if you include AHrs for the statr battery.

All battery monitors (with the exception of the smartgage which is not really a battery monitor) will measure
House battery volts
House battery amps
House battery AHrs

Many will also measure start battery volts.

Only the Sterling monitor will also measure start battery amps (but not amp hours)

For most boats this is adequate. The start battery uses very little AHrs to start the engine and these are quickly replaced by the alternator.

The new Blue seas VSM battery monitor looks very good, but only the Sterling will give you amps for the start battery.
You can use a battery monitor and a separate ammeter or even 2 battery monitors, but providing you have comprehensive information on the house bank I think a basic reading of voltage is OK for the start bank.

 

[NormanS]

Many many thanks to all of you. I now have some thinking to do, but there would seem to be a clear vote for the Smartguage. Or maybe, as BJ suggests, the Smartguage + an ammeter. (I quite like to see that the alternator is doing its stuff.)

Thanks to everyone for their help.

 

[prv]

maybe, as BJ suggests, the Smartguage + an ammeter. (I quite like to see that the alternator is doing its stuff.)

I found myself convinced by Mr Smartgauge's article on the losses in typical alternator wiring. After my grand re-wiring project, I now have a single substantial cable from the alternator to the house battery, broken only by a heavy-duty fuse in a case on top of the battery. To add an ammeter, you'd have to add another set of connections to fit the shunt, plus the shunt itself has a resistance (that's the point). Maybe it's all negligible, but I still don't like the idea of adding extra resistance into the charging link (Even the fuse was added grudgingly, but the risk of shorting onto the engine was too much to ignore).

I'm quite happy with a voltage display to show that the alternator is charging, and the Smartgauge has this built in.

Pete

 

[halcyon]

I. To add an ammeter, you'd have to add another set of connections to fit the shunt, plus the shunt itself has a resistance (that's the point). I'm quite happy with a voltage display to show that the alternator is charging, and the Smartgauge has this built in.

Pete

To add an ammeter you can use a Hall Effect shunt no connections or volt drop.

Brian

 

[prv]

To add an ammeter you can use a Hall Effect shunt no connections or volt drop.

Thanks, hadn't come across those before.

I wonder why resistor-based shunts are still common though.

Pete

 

[noelex]

The rise in start battery voltage will show that the alternator is charging. Its not as good as an A, V, and Ahr reading on the start battery, as you desire, but is adequate. I have quite comprehensive battery information on 3 separate gauges on my boat, but do not have start battery AHrs.
I use solar power to top up the start battery to 100% every so often (which is a good idea for preserving the start battery). A normal battery monitor can display this charging current, which together with the start battery voltage (especially the minimum when starting) will give a reasonable indication of the state of the start battery.
The Smartguage is a very different product from a battery monitor. Its more like an intelligent voltmeter. IMHO it has a lot of limitations.

 

[Fr J Hackett]

Try one of these a bit of a faff to wire up but will do all you want.

http://www.xantrex.com/documents/Discontinued-Products/Link1000_OwnerGuide(975-0084-01-01_Rev-A).pdf

 

[noelex]

Try one of these a bit of a faff to wire up but will do all you want.

http://www.xantrex.com/documents/Discontinued-Products/Link1000_OwnerGuide(975-0084-01-01_Rev-A).pdf

A good battery monitor, but it will only measure start battery voltage not start battery current or Ahrs .

 

[halcyon]

Thanks, hadn't come across those before.

I wonder why resistor-based shunts are still common though.

Pete

Most firms are lazy, easy to sell a resistor shunt, Sealine have used Hall effect shunts for 22 years. Which now equates to a 24 year R&D programme, why you don't see more is a long long story.



Brian

 

[Conachair]

Fully charged and rested (isolated for half an hour) they read 12.6V or thereabouts.

Half hour might not be enough to tell much about the state of charge from voltage.. http://www.pbase.com/mainecruising/battery_state_of_charge

 

[cmedsailor]

All battery monitors (with the exception of the smartgage which is not really a battery monitor) will measure
House battery volts
House battery amps
House battery AHrs

Many will also measure start battery volts.

.

NASA BM1 does all these.

 

[jtwebb]

I am happy with my NASA BM1. It does only monitor the entire bank of course but I do like to know the current in and out and the Ah count. I have the big one in my boat and the better looking little on the my motorvan.