Battery power management.

[MAIZEE]

Hi again, as you are aware i recently asked for help regarding a generator but i thought it was best to let you know the problems we are having rather than for us to jump from one thing to the other as someone on here may have the answer.

 

We bought the boat in Jan 2009, it was 2 1/2yrs old but unused.

We found that the batteries took a long time t charge but lasted only 4 to 5 hrs........4 batteries 135's i am told. 1 starter battery.

After battling on we decided to buy new batteries and looked forward to better performance. Alas they still arn't lasting anything like friends of hours.

The main things on are the TV and lap top though the lap top is probably an hour a day.

The fridge is on 12v.

 

We were going to have a sterling battery management system installed but today someone told us to have the advarc one....we were also told to have the twin alternators parralleled but what is the best answer if any......

 

Thank you all so much

Lois

[GeoffS]

Hi again, as you are aware i recently asked for help regarding a generator but i thought it was best to let you know the problems we are having rather than for us to jump from one thing to the other as someone on here may have the answer.

 

We bought the boat in Jan 2009, it was 2 1/2yrs old but unused.

We found that the batteries took a long time t charge but lasted only 4 to 5 hrs........4 batteries 135's i am told. 1 starter battery.

After battling on we decided to buy new batteries and looked forward to better performance. Alas they still arn't lasting anything like friends of hours.

The main things on are the TV and lap top though the lap top is probably an hour a day.

The fridge is on 12v.

 

We were going to have a sterling battery management system installed but today someone told us to have the advarc one....we were also told to have the twin alternators parralleled but what is the best answer if any......

 

Thank you all so much

Lois

 

Smartgauge and Smartbank without a doubt.

Smartgauge

[Denis R]

Lois, I agree with Geoff. Before I fitted a Smartgauge I had absolutely no idea what was really happening with my batteries. The Smartgauge will tell you the painful truth...

I was totally deluded by my perception of the the state of charge of my batteries and the current draw of the 12V fridge before...

[Phil Ambrose]

Smartgauge and Smartbank without a doubt.

Smartgauge

 

And please do a thorough energy audit, dont' forget things like lighting, pumps etc. You have to establish exactly how much power you are using to know how to manage it correctly. You mentioned your friends last much longer but are they using as much?

 

Phil

[Justme]

The fridge is using about 20-25% of your total capacity per day.

 

With no other use the fridge would use all the power in 4 to 5 days.

 

And thats assuming that the bats are actually getting a full charge.

[Iain_S]

I agree with the usefulness of Smartgauge. The other thing that comes to mind is : Do you have split charge diodes? If so, that could be knocking a volt or so off the charging voltage.

 

Iain

[Albion]

I agree with the usefulness of Smartgauge. The other thing that comes to mind is : Do you have split charge diodes? If so, that could be knocking a volt or so off the charging voltage.

 

Iain

 

Agreed, that is where the Smartgauge/Smartbank plus heavy duty split charge relay come into their own.

1. You know exactly what state your batteries are in.

2. There is no significant voltage drop across the relay as opposed to the diode.

However, if the OP is intending to have an alternator controller fitted they often use battery voltage sensing which can overcome diode losses.

 

Also, it is complicated by the output voltage of the alternator. If it is a modern one that puts out higher voltage than early ones then an alternator regulator is a waste of time.........see the Smartgauge technical pages for further info.

 

This is a complex topic that is difficult to pin down without having a full understanding of the system fitted to the boat in entirety.

If Maizee is anywhere near Dave Reynolds at the Blue Lias marina area then I would recommend that his advice is sought.

Roger

Edited February 21, 2010 by Albion

[MAIZEE]

thanks for the replies guys.

Just wanted to check as i didn't mention it before, we have a powermaster 3k pure sine inverter. Does this fit in with the advice.

 

Just checked batteries, when i posted earlier 1.14pm we had just fully charged and had 4 bars on the inverter, just checked again and theres 2. tv fridge and 30 mins lap top....

[mayalld]

thanks for the replies guys.

Just wanted to check as i didn't mention it before, we have a powermaster 3k pure sine inverter. Does this fit in with the advice.

 

Just checked batteries, when i posted earlier 1.14pm we had just fully charged and had 4 bars on the inverter

 

What makes you think your batteries were fully charged?

[Keeping Up]

... However, if the OP is intending to have an alternator controller fitted they often use battery voltage sensing which can overcome diode losses.

 

Also, it is complicated by the output voltage of the alternator. If it is a modern one that puts out higher voltage than early ones then an alternator regulator is a waste of time.....

 

As your first sentence says - not a waste of time if you're using diodes.

[MikeV]

I can also can endorse a SmartGauge, but would also say an Ammeter is a vital tool in seeing how much current individual appliances are drawing. I actually have two. One measures the total current in/out of the domestic battery bank so you can see the charge/discharge rate. The other one just measures the appliance load, so even when you are charging you can see what proportion of the available charge current is being used by appliances. The former is essential IMHO, the latter is a luxury.

 

By switching on individual appliances you can see what current they draw. If your new batteries are 4 x 135AH then your usable capacity at best is half that, eg. 270Amp Hours, so it should power a fridge using 3 Amps for about 90 hours (3.75 days). Higher current devices hammer the batteries much harder so you will get less capacity than you think you have. If you use your inverter a lot with heavy loads (e.g Microwave, Washing Machine) then that will significantly reduce the effective capacity.

 

A 3Kw inverter can theoretically draw around 300 Amps with a full load which would flatten the batteries in less than 30 minutes. This assumes you do not take them below 50% charge beyond which they start to become seriously damaged.

Edited February 21, 2010 by MikeV

[Albion]

As your first sentence says - not a waste of time if you're using diodes.

 

Yes, but it does depend on which route you take, diode or relay, which is why we need to understand exactly what is fitted before anyone can make definitive recommendations.

Roger

[ditchcrawler]

As your first sentence says - not a waste of time if you're using diodes.

But the OP has twin alternators so why would she have a diode splitter or relay, she was actually talking of parallelling them up.

[magnetman]

Where are Chris W and Gibbo when you need them?

 

Oh, I know

 

The recession has hit Chris W where it hurts and Gibbo has sold his business so no longer needs to use the forum to promote it

[Keeping Up]

Yes, but it does depend on which route you take, diode or relay, which is why we need to understand exactly what is fitted before anyone can make definitive recommendations.

Roger

Agreed

 

But the OP has twin alternators so why would she have a diode splitter or relay, she was actually talking of parallelling them up.

She wouldn't - I was replying to Albion's earlier post

[MAIZEE]

What makes you think your batteries were fully charged?

 

 

Well exactly, from snippits on the forum i am guessing that though my batteries seem fully charged looking at the inverterr that isn't the case maybe.

 

for anyone else trying to help this is our set up.

 

IZUZU 42HP WITH TWIN ALTERNATERS not paralleled.

POWERMASTER 3KW INVERTER, stops batteries discharging too much.

BANK OF 4 NEW 135 BATTERIES. AND 1 STARTER BATTERY.

 

we have control panel wth on off switches for lights, fridge, sockets etc and a 2 way switch showing the starter battery and leisure battery levels.

we have a MICROWAVE BUT NEVER USE IT.. and a washing machine that has just been used on holidays but will be used ore often once living aboard.

 

is there anything else you need to know

If anyone could just say... do this , do that, fit this fit that and thats the best you can do that would be great.......

 

would more batteries be the answer....or shouldn't we ne having a problem

Edited February 21, 2010 by MAIZEE

[blackrose]

Lois, I agree with Geoff. Before I fitted a Smartgauge I had absolutely no idea what was really happening with my batteries. The Smartgauge will tell you the painful truth...

I was totally deluded by my perception of the the state of charge of my batteries and the current draw of the 12V fridge before...

 

How did you get your Smartgauge to tell you the current draw of your fridge? My Smartgauge has no ammeter.

Edited February 21, 2010 by blackrose

[Albion]

Well exactly, from snippits on the forum i am guessing that though my batteries seem fully charged looking at the inverterr that isn't the case maybe.

 

for anyone else trying to help this is our set up.

 

IZUZU 42HP WITH TWIN ALTERNATERS not paralleled.

POWERMASTER 3KW INVERTER, stops batteries discharging too much.

BANK OF 4 NEW 135 BATTERIES. AND 1 STARTER BATTERY.

 

we have control panel wth on off switches for lights, fridge, sockets etc and a 2 way switch showing the starter battery and leisure battery levels.

we have a MICROWAVE BUT NEVER USE IT.. and a washing machine that has just been used on holidays but will be used ore often once living aboard.

 

is there anything else you need to know

If anyone could just say... do this , do that, fit this fit that and thats the best you can do that would be great.......

 

would more batteries be the answer....or shouldn't we ne having a problem

 

Lois, you say : a 2 way switch showing the starter battery and leisure battery levels: How are the battery levels indicated on this panel, volts, row of leds showing state of charge or another indication?

It would be handy to know what voltage you are getting across the domestic battery terminals while the engine is running and shortly afterwards when you have drawn some current from them. Also the voltage at the domestic alternator terminals during charging would help to indicate potential losses somewhere in the charge cabling.

A simple Smartgauge would give a good indication of true battery levels after it had self-learnt, but that won't solve your present problem.

Adding more batteries, if the existing ones are truly not getting fully charged, won't really make the problem any better it will just mean that you have more poorly charged batteries. We need to establish whether your batteries are truly fully charged, partially charged or whether it is excessive demand of some sort that is flattening them (and from you description that seems unlikely).

Roger

[smileypete]

is there anything else you need to know

If anyone could just say... do this , do that, fit this fit that and thats the best you can do that would be great.......

 

would more batteries be the answer....or shouldn't we ne having a problem

What would help is to have an digital panel voltmeter which measures the voltage at the domestic batteries to +-0.5% accuracy or better.

 

Also a panel ammeter that measures the charging current from the alternator.

 

A good marine electrician should be able to supply and fit these no problem.

 

Trying to get battery and charging problems diagnosed on a forum without the above is not going to be easy...

 

A Smartguage is also very very helpful for day to day use, but not really a replacement for the above, I think.

 

cheers,

Pete.

[MAIZEE]

Lois, you say : a 2 way switch showing the starter battery and leisure battery levels: How are the battery levels indicated on this panel, volts, row of leds showing state of charge or another indication?

It would be handy to know what voltage you are getting across the domestic battery terminals while the engine is running and shortly afterwards when you have drawn some current from them. Also the voltage at the domestic alternator terminals during charging would help to indicate potential losses somewhere in the charge cabling.

A simple Smartgauge would give a good indication of true battery levels after it had self-learnt, but that won't solve your present problem.

Adding more batteries, if the existing ones are truly not getting fully charged, won't really make the problem any better it will just mean that you have more poorly charged batteries. We need to establish whether your batteries are truly fully charged, partially charged or whether it is excessive demand of some sort that is flattening them (and from you description that seems unlikely).

Roger

ALBION, thanks for asking.....battery levels areindicated as volts. On the inverter here are a row of led lights and a voltage. when the batteries are low the voltage on the inverter seems to be about 12.2 and once charged around 14... i cant hing off hand but i will do some proper monitoring tomorrow and post on here.

How do i check the voltage at the domestic alternator terminals.....

 

I bet your sorry you got involved now.....everyones fantastic

[Albion]

ALBION, thanks for asking.....battery levels areindicated as volts. On the inverter here are a row of led lights and a voltage. when the batteries are low the voltage on the inverter seems to be about 12.2 and once charged around 14... i cant hing off hand but i will do some proper monitoring tomorrow and post on here.

How do i check the voltage at the domestic alternator terminals.....

 

I bet your sorry you got involved now.....everyones fantastic

 

One of the first concerns is how accurate is the voltmeter that is in the panel. But we haven't much else to go on. The voltage at 14V will only be a temporary thing shortly after charging. It will settle to somewhere about 12.7 - 12.5 ish after a while or if a small load is applied to wipe off the surface charge. The batteries shouldn't be allowed to fall below about 12.2V ideally. What tells you that the batteries are low at that voltage, is it an indication by the inverter? Out of interest does the volt meter on your panel agree with the volt meter on your inverter pretty well, or are they miles apart?

 

The way that you check voltages properly is with a quality meter (such as a Fluke meter or similar) but most people won't have such a thing unless they've worked in the trade. Don't suppose you've got any sort of DVM (digital volt meter) anywhere have you? If you have then you can put the positive lead onto the heavy charge lead connection on the back of the alternator and the negative on the body of the alternator (unless it's a marine alternator of course which I doubt). You can do the same on the battery terminals. Take care with running engines and flying belts etc of course. This is much more complicated to explain than it is to do. Whereabouts are you based?

Roger

Edited to correct battery voltages

Edited February 22, 2010 by Albion

[Roger Gunkel]

ALBION, thanks for asking.....battery levels areindicated as volts. On the inverter here are a row of led lights and a voltage. when the batteries are low the voltage on the inverter seems to be about 12.2 and once charged around 14... i cant hing off hand but i will do some proper monitoring tomorrow and post on here.

How do i check the voltage at the domestic alternator terminals.....

 

I bet your sorry you got involved now.....everyones fantastic

 

How long and how often are you charging the batteries? You say that they show 14v when fully charged, but that figure suggests that you are checking the voltage immediately after charging and it is quite possible that you are getting that reading when in fact the batteries are only partially charged. It takes some time for the surface charge to drop to a true voltage reading and I believe that can be a number of hours. Those with more knowledge than I will be much more precise on that, but I am very suspicious of that 14v figure.

 

Roger

[Albion]

Where are Chris W and Gibbo when you need them?

 

Oh, I know

 

The recession has hit Chris W where it hurts and Gibbo has sold his business so no longer needs to use the forum to promote it

 

A tad cynical perhaps? I'm sure both were only trying to assist.

Roger

[mikevye]

IZUZU 42HP WITH TWIN ALTERNATERS not paralleled.

POWERMASTER 3KW INVERTER, stops batteries discharging too much.

BANK OF 4 NEW 135 BATTERIES. AND 1 STARTER BATTERY.

 

we have control panel wth on off switches for lights, fridge, sockets etc and a 2 way switch showing the starter battery and leisure battery levels.

we have a MICROWAVE BUT NEVER USE IT.. and a washing machine that has just been used on holidays but will be used ore often once living onboard

 

Dependant on the washing machine I know but powering one through an invertor takes some doing!

[deletedaccount]

ALBION, thanks for asking.....battery levels areindicated as volts. On the inverter here are a row of led lights and a voltage. when the batteries are low the voltage on the inverter seems to be about 12.2 and once charged around 14... i cant hing off hand but i will do some proper monitoring tomorrow and post on here.

How do i check the voltage at the domestic alternator terminals.....

 

I bet your sorry you got involved now.....everyones fantastic

 

I've got a powermaster inverter and the voltage reading is fairly accurate. I'm not sure about the bars as I never look at the main box, just the remote unit.

 

I've compared the inverter reading and the battery terminal voltage and the inverter generally reports slightly lower than actual charge, probably because of voltage drop and cos it's rounding down the voltage, eg 12.38 at the terminals will be 12.3 on the batteries. It's a pretty accurate guide though.

 

Like everyone else has said, the 14+ reading will be just after you've run the engine. 5 minutes later it'll read more accurately. 12.2 means you've used up half your battery capacity. The half you can use without damaging your batteries (much).

 

I find the reading is lower than the actual value if the batteries are under a load. They'll be an apparent .2/3v drop when I start up the central heating for example, which will magically re-appear a few minutes later.

 

batteries for the clueless.

 

If it's any consolation I always get loads less out of my batteries than I think, and I've got six of the buggers.

Edited February 22, 2010 by deletedaccount