Voltage meter on House batts? necessary?

[symondo]

Obviously with the negines on you also have the voltage guages for each battery connected to said engine

However - the house battery doesnt. In our setup once we've finished working out where placement is going we are aimiong to have 2 engine batteries (1 per engine) and 3 house batteries in parrallel (my dads preference)

would a volt meter attached to monitor the house battery be something of use? is it something others use or would it just be an un necessary addition

 

[jac]

Worth adding, just so you can keep an eye on the domestics and charge when they drop too low. You don't really want to discover your domestic batteries are flat when you really need them.

 

[VicS]

Obviously with the negines on you also have the voltage guages for each battery connected to said engine

However - the house battery doesnt. In our setup once we've finished working out where placement is going we are aimiong to have 2 engine batteries (1 per engine) and 3 house batteries in parrallel (my dads preference)

would a volt meter attached to monitor the house battery be something of use? is it something others use or would it just be an un necessary addition

How about a "proper" battery monitor such as BM1 or BM2 to fully monitor the house battery bank, and the engine battery voltages via a selector switch

 

[nigelmercier]

I can't think the last time I looked at the voltage on my starter battery, it's the domestics that run down.

 

[GrahamM376]

How about a "proper" battery monitor such as BM1 or BM2 to fully monitor the house battery bank, and the engine battery voltages via a selector switch

+1

NASAs are reasonably priced and give constant voltage and amps in/out reading, as well as a reasonable estimate of capacity left.

 

[MM5AHO]

Our 40 year old Rival will get its first voltmeters this winter.
40 summers without. And only the replacing of the main switchboard made it a thing to do, not the absence of them.

 

[William_H]

Well a voltmeter from China is so cheap and will tell you a lot so it is vastly better than nothing. Add a simple switch and you can switch to any number of different (isolated) batteries. Yes an amp meter for each battery is valuable but needs a shunt be inserted in the power cable so costs and installation becomes greater. A battery monitor is another step up having a cumulative amp/hour meter to tell you how much has gone in and how much has gone out hence gives a guess at charge state.
When buying a digital voltmeter look for one which can measure the voltage that is also used to power the meter. Many older types need an isolating power converter or 9v battery because the supply negative for the meter must be isolated from the negative being measured. (sometimes called 4 wire needs a battery or isolation supply)
olewill

 

[reeac]

A voltmeter will also confirm that the alternator is working. I always check mine after the first engine start of the day.

 

[Artic Warrior]

A voltmeter will also confirm that the alternator is working. I always check mine after the first engine start of the day.

That's exactly right,,Obviously it shows the voltage,,,and only take this reading after the batterys have stood for a few hrs or take
a reading each time you board the boat as then you receive a proper value rather than surface charge like after running the engine,
But mainly I want to see that the charge is going into the batterys and that the voltage rises after starting,,

 

[blackbeard]

If you have a GPS / plotter it's quite likely that you can persuade it to read battery volts.

 

[sailinglegend420]

.......Yes an amp meter for each battery is valuable but needs a shunt be inserted in the power cable so costs and installation becomes greater. A battery monitor is another step up having a cumulative amp/hour meter to tell you how much has gone in and how much has gone out hence gives a guess at charge state.....

An amp meter, or a battery monitor, is not needed just for a starter battery. A starter motor takes out so little each time the engine starts, maybe 1% or less of the battery capacity, so the Ah count is not important. The starter battery will also charge fully in about 10 minutes so you don't even have time to check the Ah count. A house battery should take out no more than 50% of the capacity over say 1-2 days so the Ah count, and the voltage, is always of interest. Every boat should have a Battery Monitor if they want to lengthen the life of their batteries.

 

[Whitty]

Merlin SmartGauge Battery Monitor £160 good bit of kit and easy to fit.

 

[symondo]

Some interesting reading there. Ill check out these links. Was just a thought as to monitor 'power state' of the house battery isn't something that is to hand like engine guages

 

[TQA]

A single digital volt meter and some switching so that you can see the state of both house a starter bats is essential.

Letting a lead acid battery run below 50% does damage, below 20% does lots of damage, even the special solid plate traction ones!

 

[lpdsn]

Well a voltmeter from China is so cheap and will tell you a lot so it is vastly better than nothing.

Exactly. I bought an LED one for £2.50. Add in a simple on off switch and some wire and the whole project costs less than the bus fare to the marina & back.

 

[Amulet]

+1 for battery monitor (BM1 from NASA in my case)

 

[Andrew G]

If you have a GPS / plotter it's quite likely that you can persuade it to read battery volts.

Blackbeard - how does that work? Andrew
(To the OP: +1 for House battery voltmeter or monitor (I have an additional one near the batteries with a three-way switch - House / Starter / Anchor))

 

[srm]

Digital voltmeter on house batts was very useful on my last boat as batts were charged with wind generator and engine. However batts failed afer five years as I was probably over estimating the level of charge. Fitted new boat with 400 amp AGM house bank, plus wind gen and solar panels for generating as well as engine and shore power charger, (and a towed generator if I need more charge when sailing down wind). With all this a battery monitor on the house bank has made managing the batts much easier. No guess work, I can see amps going in (or out) and cumulative total amps in or out since last reset of the monitor. This is my main measure as the "content gauge" under reads which is probably due to different full charge voltage for AGM batts.

If you will charge with more than one source I suggest battery monitor rather than voltmeter. Have used the NASA clipper for last 3 years.

 

[sailinglegend420]

..... a battery monitor on the house bank has made managing the batts much easier. No guess work, I can see amps going in (or out) and cumulative total amps in or out since last reset of the monitor. This is my main measure as the "content gauge" under reads which is probably due to different full charge voltage for AGM batts.....

In most battery monitors the battery voltage has nothing to do with the Ah capacity gauge reading correctly. But it appears that Nasa do use the battery voltage to help "integrate" the Ah capacity because their units do not allow two very important battery parameters to be programmed for different batteries - Peukerts Constant and the Charge Efficiency. For AGMs these two value are very different to the Nasa built-in fixed settings. Peukerts constant maybe 1.12 for an AGM and 1.25 for an FLA battery. Peukerts law is logarithmic, so a small change of 0.13 makes a huge difference. The Charge efficiency of an AGM is maybe 98% - an FLA maybe 85%, that means about 125 Ah needs to be put into an FLA battery to show an increase of 100 Ah, whereas an AGM needs only 102 Ah to raise the capacity by 100 AH.

For a Battery Monitor to display the Ah capacity properly the battery parameters have to be correctly input to the units software on installation, but many people leave the default settings as they are. As batteries age Battery Monitors all become more inaccurate as these battery parametres change - especially the battery capacity. Also battery monitors must be set to 100% full when they are know to be 100% full - which will only be after a long period of charging - maybe 24 hours. This is best done manually and not left to the automatic re-sync feature of many BMs.

A very well respected marine engineer in Maine, USA, found that “perhaps 7 out of 10 battery monitors he sees installed by both pro's and DIY's are wired incorrectly (shunt wiring problems) and 9.5 out of 10 are programmed incorrectly.”

 

[Amulet]

A very well respected marine engineer in Maine, USA, found that “perhaps 7 out of 10 battery monitors he sees installed by both pro's and DIY's are wired incorrectly (shunt wiring problems) and 9.5 out of 10 are programmed incorrectly.”

Mmm... I wonder what he means by "incorrectly" my NASA's are not wired according to the instructions, which require that the shunt be directly connected to the -ve of the battery. The (very) fat wire to where they are wired does not cause a detectable voltage drop. I have measured it under massive load. I'm therefore confident in their readings despite their "incorrect" wiring. "Peukert's equation" - the expression NASA uses - bestows spurious credibility on what is, in my opinion, essentially a rule of thumb. However it all seems to work pretty well for me. I also have the problem that the NASA instrument asks for the battery capacity. Older batteries lose capacity, and the NASA advice was to guess how much the real capacity is. However, I think the monitors are a great piece of kit giving me a general picture of how the batteries are doing, and having them there has often alerted me to a failure to switch the fridge off under sail and such like.