Smartgauge

[smileypete]

I almost hate to ask this for fear of getting my head ripped off but here goes...

 

We have one of these -

 

http://www.mastervolt.com/marine/products/system-panels/masterlink-micc/

With the above I'd only rely on the voltmeter to tell me when to recharge.

 

If the batt voltage stays below 12.2 all the time, it's time to recharge.

 

Good way to remember is '12.2, work to do...'

 

If this seems a bit too much hassle, by all means get a Smartgauge....

 

I'd only use the amp-hour counter, with a bit of caution and experience, just to help predict when the above voltage is reached.

 

Edit: If you like I can just as simply explain how to see when the batteries are fully charged, using the ammeter.

 

cheers,

Pete.

Edited September 19, 2010 by smileypete

[Doorman]

Amp hour counters, based on a shunt, measure amps going in and out and add or subtract that from the size of your battery bank to give an estimation in percent of how much is left in that bank. Problem is the size of that bank is constantly reducing so it's a case of 'shifting sands' and the reading will be increasingly inaccurate. The SG uses a different principle and is the only monitor that gives an accurate estimate of power left in battery banks despite varying battery capacity.

 

 

That's it, I'm having one!

[Guest]

 

If the batt voltage stays below 12.2 all the time, it's time to recharge.

 

cheers,

Pete.

 

Define all the time though??

 

So I'm guessing I've basically got nothing more than a volt/amp metre with a nice LCD display, if so fair enough...

 

If I've got this correct, the SG may actually say 'hang on', you don't actually need to charge your batteries just yet, I'll let you know when you need to??

 

Am I correct??

[Keeping Up]

With the above I'd only rely on the voltmeter to tell me when to recharge.

 

If the batt voltage stays below 12.2 all the time, it's time to recharge.

 

Good way to remember is '12.2, work to do...'

 

If this seems a bit too much hassle, by all means get a Smartgauge....

 

I'd only use the amp-hour counter, with a bit of caution and experience, just to help predict when the above voltage is reached.

 

Edit: If you like I can just as simply explain how to see when the batteries are fully charged, using the ammeter.

 

cheers,

Pete.

 

The problem with just using a voltmeter to tell you when to recharge is that the voltage reading applies only when the battery is off-load (ie there is nothing switched on). The battery voltage may well be under 12.2, simply because you have things switched on, and it may not necessarily mean that you need to recharge.

[Guest]

Edit: If you like I can just as simply explain how to see when the batteries are fully charged, using the ammeter.

cheers,

Pete.

 

But I'm not interested in if the batteries are fully charged - the info. I would be after is how long to go I've got before I need to re-charge - again I suspect this is the info. a Smartgauge can provide?? yeah/nay??

[bottle]

The Smartgauge tells you the percentage left in the battery of the total that was available when/if the battery was fully charged.

 

I will try a simile, think of the batteries as a container, when the container is full the reading is 100% you then use some of that container but you should not use more than 50%, it will not tell you in time (minutes hours) how long you have got before a re-charge is necessary.

 

The more you use the quicker a re-charge is required.

 

Now here is the clever bit, when charging a battery you cannot get it back to where it was before, its an age thing, the Smartgauge knows this and very cleverly works out when the battery is back to its maximum SOC (state of charge) it is capable of and will read 100%.

 

With an ampere,hour counter all that does is read amps in, amps out but to re-charge a battery you need to put back approximately 1.5 times what you took out, this is where the ampere, hour meter falls down.

[Guest]

Thanks Keith - also just clocked the FAQ on the Smartgauge web site.

 

Get it now.

 

- thanks.

[smileypete]

Define all the time though??

Well if big load is switched on, the voltage will drop right down, but will bounce back mostly when the load is removed.

 

If the voltage rises back above 12.2 then fine, if stays below 12.2 all the time it's time to recharge.

 

 

So I'm guessing I've basically got nothing more than a volt/amp metre with a nice LCD display, if so fair enough...

 

If I've got this correct, the SG may actually say 'hang on', you don't actually need to charge your batteries just yet, I'll let you know when you need to??

 

Am I correct??

Sure, for £150ish it will do it in real time and with better accuracy.

 

That said, an amp hour counter can do it in real time and with good accuracy, but only when used properly along with a voltmeter and ammeter.

 

Relying on an amp hour counter alone is worse than useless, but that's not the fault of the thing itself, just the way it's (mis)used.

 

cheers,

Pete.

[WotEver]

There's a good paper on battery testing here (clicky)

Co-incidentally I foolishly left the car doors open all day Saturday while I was doing some work outside. When I went to start the car on Sunday, surprise, surprise, I had a flat battery. I checked it with a multimeter and it was reading around 11.9V. Because I only have a tiny 20 year old trickle charger at home which would have taken most of the day to get enough into the battery to start the engine I decided to be lazy and use my free-with-my-bank-account AA membership to get a boost.

 

AA man came along and clipped on his handheld computerised battery tester. "It measures conductance and all sorts of clever things" he told me. It then spat out a piece of paper which read "Replace Battery". I said to him "Well it would, wouldn't it? It doesn't know that I've dragged the battery down, it just thinks the battery can't hold a charge". After some quite strong persuasion from me he reluctantly put his booster cables on, left it a few minutes and then started the engine. After leaving it ticking over for about 15 mins (with 13.85V coming from the alternator) we stopped the engine. left it ten minutes and then 'tested' the battery again. The result this time? Tired but acceptable with a printed out "Pass" slip. I know the battery is old and tired (and I've just about destroyed it with the weekend's antics) but it should continue to start the engine for quite a while longer yet.

 

I wonder how many unneccessary battery sales AA agents have made just because "Computer says 'No'".

 

Tony

[Gibbo]

 

Relying on an amp hour counter alone is worse than useless, but that's not the fault of the thing itself, just the way it's (mis)used.

 

 

This is only partially correct.

 

I've got as much interest (both financially and anorak-wise) in amp.hour counters as any other sort of battery monitor. I've designed two in the past and I'm actually working on one right this very minute.

 

They do not work for state of charge unless a full recharge is done after almost every cycle. And you certainly can't wait longer than two cycles before performing a full recharge otherwise it will run out of sync so far that it might as well not be there. An out of sync amp.hour counter is actually worse than nothing.

 

They do not work for state of charge once the battery has aged and lost capacity unless the user actually runs a good discharge test and resets the battery capacity.

 

They do not work for state of charge unless Peukert's exponent is regularly rechecked and entered (by running two almost complete discharges at different rates and manually calculating it) because it changes as the batteries age.

 

There is no point trying to argue otherwise.

 

If not doing all the above is "the way it's (mis)used" then you're right.

 

But it is the batteries that are being used not the monitor. If a battery monitor can't monitor the batteries the way they are normally used, and the battery useage pattern has to be drasitcally changed to enable the monitor to work then the monitor is useless.

 

I'm not alone in this opinion Pete. Everyone who sells them or (as I was) is involved in technical support calls gets absolutely sick and tired of trying to explain away why the displayed SoC bears little or no resemblance to the reality. That's why I designed what I did.

 

The MOD's latest generic vehicle spec states absolutely specifically that amp.hour counters are not to be used for SoC monitoring in any military equipment/vehicles and that they will only accept model based devices. The US DoD have made a similar statement but that hasn't yet been officialy released as a specification. They both state this because they absolutely know for a fact the amp.hour counting doesn't work.

 

Amp.hour counters do have many uses, but monitoring SoC is not one of them.

 

 

<big snip>

 

I wonder how many unneccessary battery sales AA agents have made just because "Computer says 'No'".

 

 

There are three major problems with that type of device.

 

1. Many of them don't work very well.

2. The operator has to know what he's doing otherwsie he'll get totally silly results.

3. If someone tries to operate one without reading (and understanding) the manual they can often report that even a brand new battery is knackered.

[smileypete]

Just to repeat what I said earlier...

 

'With the above [Mastervolt panel] I'd only rely on the voltmeter to tell me when to recharge.

 

If the batt voltage stays below 12.2 all the time, it's time to recharge.

 

Good way to remember is '12.2, work to do...'

 

If this seems a bit too much hassle, by all means get a Smartgauge....

 

I'd only use the amp-hour counter, with a bit of caution and experience, just to help predict when the above voltage is reached.'

 

 

And...

 

'That said, an amp hour counter can do it in real time and with good accuracy, but only when used properly along with a voltmeter and ammeter.

 

Relying on an amp hour counter alone is worse than useless, but that's not the fault of the thing itself, just the way it's (mis)used.'

 

cheers,

Pete.

[Gibbo]

Relying on an amp hour counter alone is worse than useless, but that's not the fault of the thing itself, just the way it's (mis)used.

 

But it's this bit that I'm objecting to because it's wrong.

 

It is the fault of the amp.hour counter.

[nb Innisfree]

The only use for an amp hour counter that I can see is to work out what your power consumption is over a certain period, saves doing a power audit and is more accurate, apart from that it is pretty much useless.

[smileypete]

The only use for an amp hour counter that I can see is to work out what your power consumption is over a certain period, saves doing a power audit and is more accurate, apart from that it is pretty much useless.

Well I did say...

 

'I'd only use the amp-hour counter, with a bit of caution and experience, just to help predict when [12.2V] is reached.'

 

For that I would find it very useful.

 

cheers,

Pete.

[nb Innisfree]

Well I did say...

 

'I'd only use the amp-hour counter, with a bit of caution and experience, just to help predict when [12.2V] is reached.'

 

For that I would find it very useful.

 

cheers,

Pete.

 

To predict when 12.2v is reached I would just use a voltmeter?

[Cinimod]

I have a SG for sale if anyone is interested PM me - only used for about 3 months, now we have to sell our lovely girl...

[Nickhlx]

I have a SG for sale if anyone is interested PM me - only used for about 3 months, now we have to sell our lovely girl...

PM sent.

Nick

[ditchcrawler]

The AA sell a lot of new batteries, it even made Watchdog on the TV

[WotEver]

The AA sell a lot of new batteries, it even made Watchdog on the TV

They tried to sell me one a couple of weeks ago after I'd left the doors open on my car all day Saturday and drained the battery down to <12V. The guy put a 'battery tester' on it and said "Look - it's failed, it needs replacing". I replied "Of course it's failed, it's flat because I flattened it". After 30 minutes of running the engine he tested it again... "Oh, it's passed now".

 

I know I haven't done it any favours but it's still starting the engine healthily on these cold mornings.

 

Tony

[Mrs Humdinger]

I've been trying to convince Mr Hum that we need a Smartgauge, but he's not convinced. He did perk up a bit when I said that it would probably make the batteries last twice as long (bit of a generalised sweeping statement I know), so am sure he will come round.

 

I am convinced that as per our past usage pattern we have not been re-charging the batteries enough - using a very basic rule of thumb of if you take an hours worth of power out, you need to put 2 hours worth back in. I read that somewhere but am not sure how right that is.

 

Anyway, following our recent trip up the Severn (when the current was way way too strong to be out, the freezing cold, the boating in the dark because of the current, getting a brick thrown at us at Worcester, and Mr Hum nearly having a nervous breakdown - he says he's never going out in the boat again!!), shore power beckons. We have a Mastervolt Mass Combi Inverter/Charger thingy.

 

My question is, what is best practice. We only use the boat at weekends, and at present switch everything off at the isolaters when we leave. Now we have shore power, should I leave the charger switched on all the time and just let it do it's thing, or switch it on periodically? Is it better to discharge/recharge once than lots of little discharges/recharges??

[WotEver]

My question is, what is best practice. We only use the boat at weekends, and at present switch everything off at the isolaters when we leave. Now we have shore power, should I leave the charger switched on all the time and just let it do it's thing, or switch it on periodically? Is it better to discharge/recharge once than lots of little discharges/recharges??

We have shore power from the marina and I leave our Victron permanently on. It's supposed to be intelligent and do the occasional equalising charge, but I have no idea if it actually does do, as I've never arrived at the boat when it was doing anything other than ticking over with fully charged batteries.

 

Tony

[nb Innisfree]

I've been trying to convince Mr Hum that we need a Smartgauge, but he's not convinced. He did perk up a bit when I said that it would probably make the batteries last twice as long (bit of a generalised sweeping statement I know), so am sure he will come round.

 

I am convinced that as per our past usage pattern we have not been re-charging the batteries enough - using a very basic rule of thumb of if you take an hours worth of power out, you need to put 2 hours worth back in. I read that somewhere but am not sure how right that is.

 

Anyway, following our recent trip up the Severn (when the current was way way too strong to be out, the freezing cold, the boating in the dark because of the current, getting a brick thrown at us at Worcester, and Mr Hum nearly having a nervous breakdown - he says he's never going out in the boat again!!), shore power beckons. We have a Mastervolt Mass Combi Inverter/Charger thingy.

 

My question is, what is best practice. We only use the boat at weekends, and at present switch everything off at the isolaters when we leave. Now we have shore power, should I leave the charger switched on all the time and just let it do it's thing, or switch it on periodically? Is it better to discharge/recharge once than lots of little discharges/recharges??

 

If batts are below approx 80% SoC then they will take all the amps you can throw at them bulk charge) when 80% is reached then the batts resistance will reduce the charge going in (absorption charge) so when below 80% SoC and doing a bulk charge an hours use will take just over an hour to replace. When above 80% SoC and doing an absorption charge it can take much longer than 1 hour to replace 1 hours usage, this is why 1.5 times usage is needed to replace power, it's a rule of thumb, not exactly true just a rough guide.

 

Batteries don't like being discharged less than 5% of capacity but the problem with float charging is if it is left too long on a normal float voltage it can damage batteries, better to have a reduced float voltage which some chargers do, Victron have a so called 4th stage which reduces float voltage automatically after a certain period and then gives them an occasional boost.

 

Personally I would leave batts disconnected and off charge provided they are fully charged to 100% SoC and if they are only being left for a week, if they are not fully charged but nearly then they need to remain on float for a while, say, 48 hours to top them up, maybe a timer to switch charger off after this period? If a longer period without use is envisaged and a Victron type of float charge isn't available I would opt for an occasional float charge. Another prob with leaving shore power connected is of course the risk of galvanic corrosion if no isolation transformer is being used.

 

That's my take on it, see what more knowledgeable people than me think of it of which I'm sure there are lots!