Battery Management Systems - Best value for money

[Clive A]

I am considering including a battery management system in my electrics. There is a variety of systems on offer, with impressive sounding statistics (accompanied with impressive prices!), but to a lay-man all the numbers mean little.

Any advice on how to choose the right system would be greatly appreciated.

 

Clive

 

Love, Light 'n' Peas

[chris w]

You want to be able to monitor volts, amps and state-of-charge of the batteries.

 

Amps should definitely be monitored by the use of shunts and not an in-line ammeter. This avoids the potentially high losses due to routing cables through an ammeter.

 

There is no ampere-hour meter (AH) on the market which will give you an accurate output. They can measure AH used approximately but, when recharging, one needs to put back almost another 50% of which the AH meter will not take account. Most of them also ignore the "Peukert" factor which is the factor whereby the more current you draw, the higher the AH you use over and above a straight linear calculation. I have the Sterling Power Management System which does all the above but will not accurately display the AH put back nor take into account the Peukert factor.

 

The "Smartgauge" will apparently give a very accurate measure of State-of-Charge (not AH) as a percentage on both charge and discharge, will also show volts but will not measure current. So a combination of more than one system may be the best course.

 

Chris

Edited December 14, 2008 by chris w

[Justme]

Perhaps if you list exactly what you want to monitor more specific advice can be offered.

 

My (multi part) system that I am just installing will monitor

 

battery volts

solar volts

wind volts

volts at inverter

battery SOC %

amps from solar

amps from wind

amps consumed by inverter

amp/h made by wind

amp/h made by solar

amp/h consumed by inverter

 

 

Some of that can be viewed on remote panels,some via pc connections & some directly on the equipments panels. Some of it is live data only & some is recorded for later use.

 

 

Justme

[Nickhlx]

Perhaps if you list exactly what you want to monitor more specific advice can be offered.

 

My (multi part) system that I am just installing will monitor

 

battery volts

solar volts

wind volts

volts at inverter

battery SOC %

amps from solar

amps from wind

amps consumed by inverter

amp/h made by wind

amp/h made by solar

amp/h consumed by inverter

 

 

Some of that can be viewed on remote panels,some via pc connections & some directly on the equipments panels. Some of it is live data only & some is recorded for later use.

 

 

Justme

 

 

Sounds like a full time job ! I too hope to be able to monitor most of those that I will eventually have ( no solar / wind generators planned yet). I hope to be able to incorporate the Smartgauge system as doing several of these tasks over an above the standard management system.

 

Nick

[Gibbo]

A problem here is what do you mean by a "battery management system"?

 

As other replies here have shown many people consider this term to be the name for something to monitor your batteries. Others believe it to be the entire battery charging/monitoring system. A view I hold.

 

However others (particularly Adverc) consider a "battery management system" to be an alternator controller! (WTF?) A thoroughly bad use of the term in my eyes. It doesn't manage the the batteries. It manages the alternator.

 

So what exactly do you mean by "battery management system"?

 

Gibbo

[chris w]

I monitor:

 

1. Volts and amps out of the starter battery alternator

 

2. Volts and amps out of the domestic battery alternator

 

3. Inverter volts and amps consumed by the inverter

 

4. Volts and total amps (in/out) of the domestic batteries

 

5. Ampere-Hours (in/out) of the domestic batteries (within the limitations of an AH gauge).

 

Chris

[Gibbo]

I monitor:

 

1. Battery State of Charge percentage display

 

I don't even look at all the rest of it anymore. Especially the amphours counter.

 

Gibbo

[Justme]

I monitor:

 

1. Battery State of Charge percentage display

 

I don't even look at all the rest of it anymore. Especially the amphours counter.

 

Gibbo

 

 

My amp/h counter is so I can see if the solar & wind are producing a viable amount of power over time rather than just looking at a snapshot amps reading when you actualy take a look (IE when its extra sunny for the solar or howling a gale for the wind).

 

Justme

[Clive A]

I was under the impression that a battery management system reduces the time spent running the engine to charge the batteries, by maintaining a steady charge rate; which I'm told gradually falls as the battery gets closer to full charge. The lower running costs are my main concern - all I expect from the "flashing lights" is tell me when I need to turn the engine on and off!

 

Clive

 

Love, Light, 'n' Peas

[Gibbo]

I was under the impression that a battery management system reduces the time spent running the engine to charge the batteries, by maintaining a steady charge rate; which I'm told gradually falls as the battery gets closer to full charge. The lower running costs are my main concern - all I expect from the "flashing lights" is tell me when I need to turn the engine on and off!

 

As I suspected. You are talking about an alternator controller.

 

Time for a fight

 

I'll get mi popcorn.

 

Gibbo

[MikeV]

...all I expect from the "flashing lights" is tell me when I need to turn the engine on and off!

Smartguage is probably best for this part. You could even have an alarm/light driven by the Smartgauge alarm output set to come on whenever the state-of-charge drops below 50% - or whatever % SoC you deem the minimum you would like to retain before commencing charging.

 

Smartgauge is less accurate as to when to turn the engine off, but good enough if you want to keep it simple.

 

I'm not going to get into the battle on how best to to charge your batteries to minimize the engine running time!! I'd get your flak jacket and hard hat ready though!

 

In my own case I'm usually cruising for enough hours a day such that the batteries are fully charged vs my overnight usage, or I'm in the marina where I plug in the mains charger. So minimizing the engine running time is not a big issue for me. //Mike

Edited December 15, 2008 by MikeV

[chris w]

I was under the impression that a battery management system reduces the time spent running the engine to charge the batteries, by maintaining a steady charge rate; which I'm told gradually falls as the battery gets closer to full charge.

Clive

All chargers do that, even alternator controllers and mains drive multistage chargers. They can't prevent that happening. What an alternator controller will give you is a higher current at those particular revs as compared to a basic regulator. But the current will still tail off as the battery charges and the battery terminal voltage increases.

It's just Ohm's Law.

 

A Battery Management System will give you lots of info (some of it occasionally accurate and useful) about State-of-Charge, Ampere-Hours, volts and currents.

 

Chris

Edited December 15, 2008 by chris w

[Denis R]

I was under the impression that a battery management system reduces the time spent running the engine to charge the batteries, by maintaining a steady charge rate; which I'm told gradually falls as the battery gets closer to full charge. The lower running costs are my main concern - all I expect from the "flashing lights" is tell me when I need to turn the engine on and off!

Having wasted a fair wad in the past on alternator controllers I didn't need, take my advice, check the voltage of your alternator. If it's 14.4Volts, go and lie down in a darkened room until the feeling for a 'battery management system' wears off.

Then fix yourself up with a SmartGauge - shows you what the pretty lights show, only in figures - turn your engine on when it shows 50%, turn it off when it shows 100%. Job done.

[Justme]

Then fix yourself up with a SmartGauge - shows you what the pretty lights show, only in figures - turn your engine on when it shows 50%, turn it off when it shows 100%. Job done.

 

Or wire the output of the smartguage to a engine start module & it can then start the engine when the volts or SOC reach a set level & then run the engine till either a V or SOC is reached & or then run for X time on top.

 

OH & dont turn it off when it hits 100% cos its not 100% till after a long absorbtion phase as well.

 

Justme

[Roger Gunkel]

I use the NASA BM1 battery monitor, which seems to be popular with the offshore fraternity, but not very common on the inland waterways.

 

It monitors battery voltage, amps in/out, charge rate, discharge rate, state of charge, time to discharge/charge and can be set up for bank capacity etc. The monitor is a 4" square LCD screen with on/off backlight and different screen selection buttons. It came with a shunt and all connection cables and has been simple to fit and use and very effective.

 

Roger

[Justme]

I use the NASA BM1 battery monitor,

 

 

I have a similar one (Sterling ProCounter) but it is able to monitor 4 shunts (amps) & 4 sepperate voltage points plus amp/h on one of the shunts.

 

Not fitted it yet as I was waiting for extra shunts to arrive.

 

Did consider the NASA one as well but the 4 shunt option sold it for me.

 

Justme

[Roger Gunkel]

I have a similar one (Sterling ProCounter) but it is able to monitor 4 shunts (amps) & 4 sepperate voltage points plus amp/h on one of the shunts.

 

Not fitted it yet as I was waiting for extra shunts to arrive.

 

Did consider the NASA one as well but the 4 shunt option sold it for me.

 

Justme

 

If I had an electronics system the size and complexity of yours, I would agree with having the flexibility of the extra shunts and monitoring points. I couldn't justify the extra expense for my own pretty standard setup, so the Nasa does a great job for the price. You'll find it very satisfying being able to see whats going on when you get your system wired in.

 

Roger

[Big John]

I use the NASA BM1 battery monitor

I have 6x110Ah (which I make 660Ah) but the NASA bm says it will cope with 650Ah. Is this within probable practical tolerances?

[sternwag]

We have a sterling AB1290 which i guess is considered to be an alternator manager fitted to our 1974 boat with lister sr2 and 90 amp alternator. It seems to charge the 6 x 110 domestic battery bank to full charge within 1.5 hours a state never achieved with a days chugging before it was fitted. We use a multimeter permanently connected to the 12 v electrics for monitoring purposes along with the lights on the AB1290. We have recently fitted 2 x 85w solar panels these on a sunny winters day negate running the engine at all. On an overcast day a 20/30 min run seems to provide all the power needed for pumps, lights fans and laptop. Unit has been installed 4 months now so battery life, reliabilty still in question.

[chris w]

We have a sterling AB1290 which i guess is considered to be an alternator manager fitted to our 1974 boat with lister sr2 and 90 amp alternator. It seems to charge the 6 x 110 domestic battery bank to full charge within 1.5 hours a state never achieved with a days chugging before it was fitted. We use a multimeter permanently connected to the 12 v electrics for monitoring purposes along with the lights on the AB1290. We have recently fitted 2 x 85w solar panels these on a sunny winters day negate running the engine at all. On an overcast day a 20/30 min run seems to provide all the power needed for pumps, lights fans and laptop. Unit has been installed 4 months now so battery life, reliabilty still in question.

An alternator controller will give you more amps of charge than a normal regulator at the same revs. However, with respect, unless you're just using them to charge your torch, you will NEVER charge 6x110AH batteries in 1.5 hours. Multiply that by a factor of TEN (yes 10) and I would believe you.

 

You will only be partially charging them and they will have a short life expectancy due to sulphation.

 

How are you determining that they are FULLY charged? Whatever is telling you that is giving you incorrect information.

 

With your solar panels, even on the sunniest of days, I estimate you will only putting in about 30AH-40AH per day. Due to battery physics, for every 1AH you use, you have to put back, via charging, almost 1.5AH. For a typical NB, daily consumption would be of the order of 100AH per 24 hours. That means a recharge of almost 150AH to get them back to where they started.

 

Chris

Edited December 15, 2008 by chris w

[sternwag]

An alternator controller will give you more amps of charge than a normal regulator at the same revs. However, with respect, unless you're just using them to charge your torch, you will NEVER charge 6x110AH batteries in 1.5 hours. Multiply that by a factor of TEN (yes 10) and I would believe you.

 

You will only be partially charging them and they will have a short life expectancy due to sulphation.

 

How are you determining that they are FULLY charged? Whatever is telling you that is giving you incorrect information.

 

With your solar panels, even on the sunniest of days, I estimate you will only putting in about 30AH-40AH per day. Due to battery physics, for every 1AH you use, you have to put back, via charging, almost 1.5AH. For a typical NB, daily consumption would be of the order of 100AH per 24 hours. That means a recharge of almost 150AH to get them back to where they started.

 

Chris

 

Hi Chris

I expect you are correct, maybe our power usage is very low. We have background leds 16 on during darkness (16hrs a day) pumps for water in and out, halogen spots as needed during cooking. We also run laptop on 12v / 18v converter 4 hours a day on average. We have 2 inverters only on as needed for power tools, toaster, micro wave and low power lighting. Heating is wood burner, cooking gas. Im not sure when we are fully charged but have assumed it occurs when solar controller flashes green led. The AB1290 unit has a float charge indicator which is supposed to indicate a full charge. As you know most battery banks have a optimum charge and discharge range in which they operate efficiently so with this size of bank to our usage maybe we dont need to take hours to squeeze that last little bit of power in. I must say when moored, I notice all round me running generators and engines till 8 every night, we dont seem to need too.

[Roger Gunkel]

I have 6x110Ah (which I make 660Ah) but the NASA bm says it will cope with 650Ah. Is this within probable practical tolerances?

 

Can't see why 10ah more will make any difference! My bank was only 405ah, and I set the BM1 at about 350ah to allow for probable drop off in the battery performance as they get older. The figures shown on the monitor seem to confirm out what I get in practice. As quoted battery performance seems to vary from actual, according to age, temperatures, charging regimes etc, its probably always neccessary to jiggle with the settings for a while to get reasonably accurate status figures.

 

Roger

[Nickhlx]

Can't see why 10ah more will make any difference! My bank was only 405ah, and I set the BM1 at about 350ah to allow for probable drop off in the battery performance as they get older. The figures shown on the monitor seem to confirm out what I get in practice. As quoted battery performance seems to vary from actual, according to age, temperatures, charging regimes etc, its probably always neccessary to jiggle with the settings for a while to get reasonably accurate status figures.

 

Roger

 

 

Shouldn't 6 x 110 aH be nearer 750 aH ? Or shoud I sit nearer the front of the class ?

 

Nick

[Denis R]

Or wire the output of the smartguage to a engine start module & it can then start the engine when the volts or SOC reach a set level & then run the engine till either a V or SOC is reached & or then run for X time on top.

 

OH & dont turn it off when it hits 100% cos its not 100% till after a long absorbtion phase as well.

 

Justme

I like that idea - I'll have a rake through the manual and see if I can find a way to program it so it doesn't start the engine between 8pm and 8am

I forgot that seemingly minor aside about the absorbtion phase..... Without it the missing bit of the explanation should have been: "Then just renew your battery bank every 12-18 months."

Have to say that before fitting the SmartGauge, based on the before/after charging regime, I must have been habitually discharging the batteries way below 50%, which probably accounts for the first bank only lasting 2 years.

 

Edited: finger trouble.

Edited December 16, 2008 by Denis R

[Gibbo]

I like that idea - I'll have a rake through the manual and see if I can find a way to program it so it doesn't start the engine between 8pm and 8am

 

We've done a few of these. Set the alarm to trigger at 50% (or whatever your preferred figure is) and set it to run for X hours (as opposed to "until a certain charge status"). Then use a time switch in line with the alarm contacts so it can only fire up at certain times of the day.

 

Gibbo