12v battery monitor

[Moondaisy]

I will soon be fitt.ing some new domestic batteries. Is there a monitor available so I can make sure I charge them when needed? I have a built in volt meter but would like something more accurate.

 

Many thanks.

 

I have recently fitted a NASA monitor. brilliant. delighted with it. I hear from others that their service, when needed, is excellent

[Roger Gunkel]

I have recently fitted a NASA monitor. brilliant. delighted with it. I hear from others that their service, when needed, is excellent

 

I also fitted a Nasa BM1 battery monitor last year, which has been excellent in monitoring battery performance, amps in and out, voltage, state of charge etc.

 

It was just over £80 when I bought it and it was chosen partly for the price, but also because it showed amps and volts as well as SOC, and was a vey neat small unit. There has been much discussion over the accuracy of the Nasa compared to the Smartguage, and I would be the last to dispute that the Smartguage is a more accurate measure of the SOC and an excellent piece of equipment. However, it is not the only monitor available and after some initial adjustment over the first weeks after fitting, I checked my Nasa readings against both multimeter and SG readings and found it to be accurate enough to give me full confidence in what it shows.

 

If you want the most accurate SOC reading available and don't mind the extra cost, get the Smartguage. If you want acceptable SOC plus amps and volts then the Nasa is an excellent buy in my opinion.

 

Roger

[Top cat]

Now this may be heresy but I have found amp hour counters to be very accurate in another application -recharging lithium polymer batteries used in model aircraft. Ok it'sdifferent chemistry but I get very consistent results usually to within a pecent or so. Lipos are fussy beasts and would soon fail if the charge was more than a few percent out. Are lead acid batteries so different in their charge / discharge charecteristics ? Why do amp hour counters have such a bad reputation?

 

At the moment all I have on the boat is a an Adverc multimeter reading volts and as we cruise most days we are not pushing the batteries very hard, that seems to work well enough. But we expect to be stationary for a few days later in the year and I'm considering whether I need a more sophisticated system? I'm not sure how far to go , just add a shunt to measure amps, get a NASA or go for a Smart guage .

 

Regards

 

TC

[Lee J]

Yes it does.

 

Which then leads to the question of "what does 0% mean?"

 

There's quite a large section on this on the website so I don't have to keep emailing people the same answer. I don't actually expect anyone to read it

 

0% does not mean completely flat as a pancake. 0% is the borderline between actually running the battery down seriously low and the place where immediate irreversible battery damage results. It basically equates to what the manufacturers state is the specific gravity when flat.

 

When it reaches this level there is still some power available, but it will not do the battery any favours to try to use it.

 

Gibbo

 

Gibbo,

 

I've been very carefull not to let my batts discharge below 50% (on th SG) as I though this was the point of no return with respect of battery damage. Am I being overly cautious based on your above answer. (In reality I start pacing the companionway worriedly when they get to 65%)

 

Lee

[Gibbo]

Gibbo,

 

I've been very carefull not to let my batts discharge below 50% (on th SG) as I though this was the point of no return with respect of battery damage. Am I being overly cautious based on your above answer. (In reality I start pacing the companionway worriedly when they get to 65%)

 

Lee

 

Discharging down to zero percent is a different matter altogether than discharging to 50%

 

Discharging to zero percent will do immediate, irreversible, damage to the battery. It will never work properly again. It relates to actually breaking the battery.

 

Dischagring to 50% is to do with getting economical life out of the batteries.

 

http://www.smartgauge.co.uk/50percent.html

 

Gibbo