Batteries losing charge

[M&H]

Hi all

 

We bought our narrowboat about 2 months ago with what look like fairly new batteries - in fact, a engineer who recently looked at the engine commented on that.

 

However, my wife noticed when charging her laptop that it would stop charging unless the engine was running at the time. I checked voltage at the battery after the last couple of engine runs and found the domestics looked well-charged. The last time I checked the multimeter read 13V immediately after running the engine, but checking it again less than an hour later it had dropped to 12.4V. This morning, 12 hours later, it was 11.7.

 

We don't use a lot of electrics. We have a 12V fridge, LED lights, water and shower pumps, and a thermostat for the central heating/water heating. The laptop gets charged about once or twice a day.

 

Before I jump to the conclusion that the batteries are kaput, I was wondering if there are any other potential causes for the drop in voltage.

 

I'm concerned that if there's an underlying problem, that new batteries will end up in the same situation soon after.

 

Thanks for any help folks can offer!

 

 

[Paul's Nulife4-2]

Hi ya,

What size Battery Banks, and what is the power usage on your Fridge, have you got an inverter swited on, even if it's not being used, have you got All LED lights or are there bulb tyips as well

Have you got Webesto/Eberspacher central heating/water heater.12v TV ect ect

Edited June 8, 2014 by Paul's Nulife4-2

[Paul C]

What kind of central heating and was it switched on at the time? Without knowing the current draw at the time, voltages are more/less meaningless for determining battery state of charge, although obviously if there's not enough voltage and the inverter trips out, then that shows poor battery health!

[M&H]

They're x2 110ah batteries. We only have LED lights. It's a Alde heater, but we didn't have it on. No TV, no inverter either. Since the last charge, we have probably had a light on for about an hour, the fridge, and the water pump a few times.

 

That's about all the power we've used.

 

Edit -- the fridge is a LEC, but I don't have a manual for it. I haven't figured out how to find out its power usage (I'm very new to this 'electricity' thing!).

Edited June 8, 2014 by M&H

[OldGoat]

Hi all

 

 

 

We don't use a lot of electrics. We have a 12V fridge, LED lights, water and shower pumps, and a thermostat for the central heating/water heating. The laptop gets charged about once or twice a day.

 

Before I jump to the conclusion that the batteries are kaput, I was wondering if there are any other potential causes for the drop in voltage.

 

I'm concerned that if there's an underlying problem, that new batteries will end up in the same situation soon after.

 

Thanks for any help folks can offer!

 

 

 

 

The 12V fridge is a 'gas guzzler' a LEC 12v (very old now) even more so because they were made in the days where insulation materials were poor and manufacturers skimped on it to maximise the interior capacity.

 

My guess is that it consumes about 70 amp hours per day - 1/3 of your theoretical capacity.

 

How do you charge your batteries?

 

"Run the engine for a couple of hours a day???"

 

AARRGGHH....

 

(Some more patient folks may be along shortly.)

[M&H]

 

 

The 12V fridge is a 'gas guzzler' a LEC 12v (very old now) even more so because they were made in the days where insulation materials were poor and manufacturers skimped on it to maximise the interior capacity.

 

My guess is that it consumes about 70 amp hours per day - 1/3 of your theoretical capacity.

 

How do you charge your batteries?

 

"Run the engine for a couple of hours a day???"

 

AARRGGHH....

 

(Some more patient folks may be along shortly.)

 

 

That's interesting to know about the Lecs -- when we bought the boat, the surveyor said it was a good fridge! It's clearly old though, so perhaps in its day.

 

Not sure on your source of frustration there OldGoat but you're on the money - couple of hours a day, and longer cruising at the weekends. That said, we're getting solar panels fitted (this week!) too.

 

Is there another way to charge batteries that you'd recommend? (we don't have shoreline connection.)

[Alan de Enfield]

 

Was anything running when you saw 11.7V.

 

Basically your batteries may have gone beyond the point of no-return. You quickly need to get them charged up to 12.6-12.7 volts and see if they hold charge.

 

Are you charging via the engine ? What size is your alternator and how many hours a day are you running it ?

Do you have a land line and battery charger ?

Do you have a generator and battery charger ?

Are you on the bank or in a marina - do you have power available ?

 

With 2x NEW 110a batteries you have (according to the theory) 110 amps available, as it is not recommended to drop below 50% charge. You are using (as has been suggested) 70 amps for the fridge.

 

You need to do a proper audit of your electrical consumption and have the batteries checked/tested, as they may be 'well used' and only providing 60 / 70 or 80 amps.

[Alan de Enfield]

 

 

Not sure on your source of frustration there OldGoat but you're on the money - couple of hours a day, and longer cruising at the weekends. That said, we're getting solar panels fitted (this week!) too.

 

Lets say your alternator is 55 amp, when its running at low revs (tick-over or canal cruisng) its probably putting out 35 amps (mine does).

You are running it for 2 hours so you are prodcuing 70Ah

 

Your fridge is taking 70Ah - thats everything your alternator is producing

 

You are running pumps, computer chargers, lights, TV etc, and every amp they are consumimg comes "out of the store" (battery) progressively flattening it.

 

You probably need to run the engine 4 hours per day to replace what you use, and 8 hours at weekends to top it up a bit.

 

How much solar are you getting ?

It would be worth doing some reading up on electrical systems and batteries.

 

As your battery becomes charged it becomes harder and harder to push the 'amps' into it, such that it may take 4 hours to get from 50% to 80% charge and another 8 hours to get the last 20% in.

[M&H]

 

Was anything running when you saw 11.7V. Yes -- the fridge only.

 

Basically your batteries may have gone beyond the point of no-return. You quickly need to get them charged up to 12.6-12.7 volts and see if they hold charge. I've had no trouble getting them up to that voltage by running the engine, but they don't hold their charge.

 

Are you charging via the engine ? What size is your alternator and how many hours a day are you running it ?

Do you have a land line and battery charger ?

Do you have a generator and battery charger ?

Are you on the bank or in a marina - do you have power available ?

We don't have any method of charging the batteries other than running the engine at the moment. The alternator is 70a, according to a Canal & River Rescue engineer.

 

With 2x NEW 110a batteries you have (according to the theory) 110 amps available, as it is not recommended to drop below 50% charge. You are using (as has been suggested) 70 amps for the fridge.

 

You need to do a proper audit of your electrical consumption and have the batteries checked/tested, as they may be 'well used' and only providing 60 / 70 or 80 amps.

How do you measure the power consumption of, say, a fridge? I've read about measuring amps by putting a multimeter in the circuit, but in practice where would you do this? (frustratingly, the well-marked fuse box includes everything but the fridge!)

Thanks!

[M&H]

 

Lets say your alternator is 55 amp, when its running at low revs (tick-over or canal cruisng) its probably putting out 35 amps (mine does).

You are running it for 2 hours so you are prodcuing 70Ah

 

Your fridge is taking 70Ah - thats everything your alternator is producing

 

You are running pumps, computer chargers, lights, TV etc, and every amp they are consumimg comes "out of the store" (battery) progressively flattening it.

 

You probably need to run the engine 4 hours per day to replace what you use, and 8 hours at weekends to top it up a bit.

 

How much solar are you getting ?

It would be worth doing some reading up on electrical systems and batteries.

 

As your battery becomes charged it becomes harder and harder to push the 'amps' into it, such that it may take 4 hours to get from 50% to 80% charge and another 8 hours to get the last 20% in.

 

 

Thanks again! That does clarify things nicely.

 

We're getting 200W solar panels, along with an MPPT regulator.

 

I invested in a copy of Nick Calder's book, figuring that it would save me money in the long run. But I guess I'm a slow learner!

[bottle]

M&H

 

I haven't welcomed you to the forum, so welcome.

 

Batteries and the use of is one of the most topical threads on the forum.

 

To cut to the nub of the problem....

 

You are using more power than you are generating.

 

You need to charge more and/or use less.

 

Solar will help but not in the winter.

 

The last time I checked the multimeter read 13V immediately after running the engine, but checking it again less than an hour later it had dropped to 12.4V. This morning, 12 hours later, it was 11.7.

 

Take this at face value, the 13v you saw was not the SOC (State of Charge) of the battery bank it was surface charge, normal just after charging, when it dropped to 12.4 that was somewhere nearer the correct SOC (possibly).

 

The 11.7 points towards flat.dead batteries, you used to much, it is advisable to not let your batteries go below 12.2 (off load) {50% SOC}

 

You could search the forum and good luck

 

and/or have a look at these to sights

 

http://www.batteryfaq.org/

 

http://www.smartgauge.co.uk/technical1.html

 

 

You can always come back for clarification

Edited June 8, 2014 by bottle

[M&H]

Many thanks, Bottle. I must say, this is probably the most helpful forum I've ever used.

 

Those links look really useful, and answer quite a few other questions I'd been wondering about.

 

Based on what the surveyor told me when we bought the boat, I'd assumed the fridge used around 40ah, which would be within our power-consumption budget.

 

Looks like I'm fridge (and battery) shopping this week.

[OldGoat]

Coo - I thought I'd get flamed for being a bit stroppy (I get frustrated when the same questions come up almost every week and perhaps the OPs could do a little research first - Ho Hum)

 

Buying a new 12v fridge will be costly and I don't think (know) that they won't be that much more efficient. The Shoreline models are based on more up to date LEC models. The problem with any boat fridge design is that folks want a reasonable capacity in a very small space - so efficiency is compromised.

FWIW I'd spend your money on:-

more batteries ? 4 x 110 a/h - Trojans would be a good idea.

Beef up your power generation with a second alternator or a larger power output single one - 110 Amp would be a good size.

Consider something like an Adverc controller - but that is controversial.

 

I'm sorry but, if you're living aboard and want some home comforts, then you're going to have to spend a bit or you'll always have problems.

 

 

[matty40s]

You will also find that your water heater/CH system will use a fair bit of leccy for start up and driving the circulation pump.

Two batteries seems very inadequate for your stated usage.

Edited June 8, 2014 by matty40s

[bottle]

Many thanks, Bottle. I must say, this is probably the most helpful forum I've ever used.

 

Those links look really useful, and answer quite a few other questions I'd been wondering about.

 

Based on what the surveyor told me when we bought the boat, I'd assumed the fridge used around 40ah, which would be within our power-consumption budget.

 

Looks like I'm fridge (and battery) shopping this week.

 

Lets take that as correct, so you have 2 * 110 amp.hr battery bank, that means the bank is 220 amp.hrs.

 

but as above it is recommended not to let your batteries go below 50% SOC (this is not set in stone, just a generalisation and to give probably the best cost.

implications)

 

Therefore you have 110 amp,hrs available your fridge uses 40 amp.hrs

 

So in theory you have 60 amp.hrs

 

but (that little word again)

 

it is very doubtful that 110 amp.hrs is available, batteries age, not fully charging them makes them lose capacity.

 

Worse case scenario you batteries are old and worn out so you only started with 40 amp.hrs capacity, your fridge needs all that, hence the very low reading 11.7 in the morning.

 

In an ideal world we would all charge our batteries to 100% every time we use them but the amount of energy required (diesel) would be expensive so we all compromise.

 

As Alan said in post #8 that last little bit takes a long time and a lot of diesel.

 

Everyone has their own way of doing it, personally I always charge to 95% SOC, every time and at least once a month do a full charge to 100%.

 

Killing to birds with one stone so to speak, if I knew I would being a long day, then I would leave the engine running to get to the 100%

 

I now have solar and that does the last little bit instead of the engine/generator.

 

It all comes down to planning your usage and the time that you use the power.

 

If your batteries are truly that flat, then the best way to charger them would be with mains powered charger, preferably of the 'Three stage' type and not a car battery charger and it will possibly take 24 hours to get them fully charged.

 

You are not going to be able to achieve that with an engine and alternator.

 

Well you could but you know why it would not be sensible and you should not run your engine for charging purposes between 20:00 hrs and 08:00 Hrs.

[eggpie]

The 12V fridge is a 'gas guzzler' a LEC 12v (very old now) [...]My guess is that it consumes about 70 amp hours per day

Based on what the surveyor told me when we bought the boat, I'd assumed the fridge used around 40ah

 

I think it depends which LEC model you have. Some of the older ones may be gas guzzlers, but I have a newer LEC one that uses a lot less power (it's essentially the same as the Shoreline models, using LEC cabinets and a 12V Danfoss compressor). It might be worth checking which one you have before you go shopping, given the surveyor's high opinion of it.

 

I think you're still using more power than you're creating though Fix that before you replace the batteries, or you'll end up doing the same thing to the new ones.

 

[nb Innisfree]

Our Lec fridge doesn't use any gas at all...

[frangar]

You will also find that your water heater/CH system will use a fair bit of leccy for start up and driving the circulation pump.

Two batteries seems very inadequate for your stated usage.

The OP said it was an Alde gas CH boiler....these use very little electric....just a small circulation pump....one of the reasons I think they are much better than a diesel unit....oh and they are pretty reliable too!

 

I agree with others though....you need a much bigger battery bank and a better means of keeping it charged.

 

Cheers

 

Gareth

[M&H]

OK, thanks everyone. I've switched off the fridge for now and will monitor the batteries for a day or two -- which I hope will give me a sense of their health and the draw the fridge was taking.

 

It seems to me that sorting out a better charging system would be more important than more batteries, right?

 

If so, does the choice of alternators available depend on the engine (we've got a BMC 1.5)? Would a double alternator be better than a single, more powerful alternator?

 

Anyway, I got to go drink a lot of beer before it gets warm.

[Paul C]

OK, thanks everyone. I've switched off the fridge for now and will monitor the batteries for a day or two -- which I hope will give me a sense of their health and the draw the fridge was taking.

 

It seems to me that sorting out a better charging system would be more important than more batteries, right?

 

If so, does the choice of alternators available depend on the engine (we've got a BMC 1.5)? Would a double alternator be better than a single, more powerful alternator?

 

Anyway, I got to go drink a lot of beer before it gets warm.

 

Before you start looking at 2nd alternator, wait until you have your solar power setup and see if the charging's enough then. If your usage of the boat coincides with nice weather, then 200W solar would certainly be useful. We too have a small alternator (55A I think) but also 200W solar, we're able to leave the fridge on all the time and when visit, there is enough 'excess' power (in fact the batteries are mostly on 100% now) to charge the laptop, use a few lights, occasional microwave use, water pump etc. I even used 30Ah of grinder at the start of the week (the boat is currently out the water, being blacked) before I got the mains connection and the solar's brought the batteries to 100% again.

[Arthur Brown]

What is kaput is the charging cycle. However it may have permanently killed the battery anyway.

 

Get the batteries fully charged, by shore line or generator power. The measure of fully charged is probably 'til the charge current drops to 1amp.

 

Consider getting a solar panel or two, Consider using another alternator Cramming the bulk charge into the battery by diesel is good, letting the sun do the long absorbtion and float phases is good too.

 

Probably best that you go for a cruise.

 

Two alternators lets you take more power from an idling engine -better use of fuel- also it lets you direct one at the starter battery and one at the leisure battery.

[OldGoat]

Two alternators is less complicated in terms of circuits; a small one (the original) for the starter battery and the other one for the domestics.

The downside is mounting extra pulleys and a mounting bracket for the alternator.

I don't know how easy it is to put the extras on a small BMC.

 

AS it's a small engine you'll need to run it faster than tickover.

 

Solar is great - but a bonus. Don't rely on it for base charging.

 

 

[Alan Saunders]

Laptop batteries, e.g. Li-Ion, are much more expensive per watt-hr, than lead-acid batteries. They too degrade with age and useage and become less efficient. Better to power the laptop from the 12V adapter and do the power intensive operaiations when the engine alternator or the solar power has spare capacity.

 

My, reasonably efficient, 10" Laptop runs for ~seven hours on its 11.1V 6.6Ah battery (<6A at 12V). My old, 15" Laptop with a 'desktop' processor needed a 96W (8A at 12V) power supply.

Recharging a laptop battery from 10% to 100% via an 80% efficient 12V adapter could account for 8Ah for a small, efficient Laptop or 20Ah for a large, inefficient PC with a dying battery.

 

As a "rule-of-thumb' a small 12V 'fridge uses the (50%) capacity of a 100AH battery per 24hrs. One additional (leisure/house) 100A battery may be adequate for daily cruising.

 

As others have said, even if the batteries "look new" a few cycles to minimum voltage or below will ruin them!

 

Alan

 

... The laptop gets charged about once or twice a day. ...

[Richard10002]

. The last time I checked the multimeter read 13V immediately after running the engine, but checking it again less than an hour later it had dropped to 12.4V. This morning, 12 hours later, it was 11.7.

 

We don't use a lot of electrics. We have a 12V fridge, LED lights, water and shower pumps, and a thermostat for the central heating/water heating. The laptop gets charged about once or twice a day.

 

Before I jump to the conclusion that the batteries are kaput, I was wondering if there are any other potential causes for the drop in voltage.

 

 

It looks like you live on your boat and dont have access to shore power.

 

I spent a lot of time on my boat until recently. I have 3 x 110Ah varta batteries, and am considering increasing this to 4 x Trojan T105s which will give 450Ah. I have a Honda Eu20i generator which provides 240V through the shore power connection, and charges the batteries through a Sterling Pro Combi S 2500W inverter charger, which charges at 70A max. I also hav a 100W solar panel and a PWM controller.

 

If I had my time again, I would buy a Victron inverter charger with less power than the Sterling, but the Sterling does the job.

 

100W of solar contributes almost nothing if I am on board - it is really good at keeping the batteries topped up and healthy if I leave the boat for 3 or 4 days a week. If I were spending more time on board, I would fit a couple of 200W panels and an MPPT controller.

 

In terms of bang for buck and security of power throughout the year, if I were in your position, I would get a bigger battery bank, a Kipor generator, and a 50A, or so, battery charger. Then I would sort out a good sized solar bank.

 

Running the engine is fine for charging batteries, but it's easier to replace a generator than a worn out engine.

[nicknorman]

Yes OP, you need to get a handle on whether you are charging the batteries enough (sounds like you aren't). The best way to do this on the cheap is to buy a DC clamp-meter such as the UNI-T 203 (£30 from ebay) and clamp it over the lead from the alternator to the batteries. With the engine running, this will show the charge current. You will be able to see the best rpm (ie minimum) to get max current out of your alternator, and how that rpm can be reduced as the charge progresses (because the batteries will take less charge as they get fuller).

 

Most importantly it will allow you to know when to stop charging - ie when the batteries are fully charged, which is when the charge current falls to some low value around 1 or 2% of the rated capacity (say 4A in your case).

 

It will also allow you to check the charging voltage is reaching 14.4 or thereabouts during the latter part of the charge.

 

On fridges, the forum is full of doom about how much power they take. We have a 3 year old Shoreline and I don't really notice its power consumption, it's pretty low.

 

Once you are sure the batteries are fully charged you can then see if they are delivering near their rated capacity. If not, replace them and /or increase the bank size.