Head Scratcher

[tonyreptiles]

Several people have tried to get to the bottom of this problem without success.

Can anyone here solve it?

 

The set up:

1 x Starter battery

2 x 110 Leisure batteries

Split relay

Inverter

Running a laptop and occasional phone charging

No fridge

No TV

 

After running my engine for a couple of hours I get enough power for around a day and a half of working on my laptop.

I turn the inverter off when laptop battery is full and on again after it has drained.

 

HOWEVER

 

If I run my engine and try to use my inverter whilst is running the batteries drain flat.

This is true even if I switch my inverter on after the engine has been running for an hour already.

When I say the batteries run flat this refers to all of the batteries including starter, making it impossible to re-start the engine after switching it off.

 

I know I am getting plenty of charge from the alternator as the batteries charge fine if I don't use the inverter during that time.

They also charge fine via the battery charger.

 

Any ideas as to what the problem could be?

 

Cheers

TR

[blodger]

A bit more info would be helpful:-

 

What engine, fast or slow running?

 

What alternator/regulator and amps?

 

I am guessing that you are an air cooled lister with an old ACR alternator?

[WotEver]

Is the wiring completely 'normal'? By which I mean Alternator direct to domestics, with split-charge relay connecting starter battery (or the other way around), and inverter connected directly to the domestics?

 

No other relays of any kind?

 

Tony

[Iain_S]

If the alternator re-charges the batteries after inverter use, but the batteries discharge if the inverter is on while alternator turning, then somethng must be shuttng down the alternator when the inverter is switched on. Does the charge warning light come on? How long does it take for the batteries to go flat? Does it happen when cruising, or with engine idling for battery charging?

 

Iain

[tonyreptiles]

Is the wiring completely 'normal'? By which I mean Alternator direct to domestics, with split-charge relay connecting starter battery (or the other way around), and inverter connected directly to the domestics?

 

No other relays of any kind?

 

Tony

 

 

It is a BMC 1.5 with wiring as described above.

 

Cheers

TR

 

If the alternator re-charges the batteries after inverter use, but the batteries discharge if the inverter is on while alternator turning, then somethng must be shuttng down the alternator when the inverter is switched on. Does the charge warning light come on? How long does it take for the batteries to go flat? Does it happen when cruising, or with engine idling for battery charging?

 

Iain

 

The batteries re-charge fine at slightly over tick-over revs so long as I don't switch on the inverter at any point. Ignition light goes off etc.

Alternator is kicking out the right amount, according to the man with the meter.

 

Today's test involved running the engine for an hour, then switching on the inverter whilst the engine was still running.

20 mins later the inverter started to squeal its warning - and this whilst the engine was still running!

As expected, once the engine (and the inverter) were switched off, all batteries were flat and could not re-start engine.

 

Baffled!

TR

[Gibbo]

I think you've got quite a big inverter and there is an additional hefty load on that you don't know about.

[Iain_S]

(snip)

Today's test involved running the engine for an hour, then switching on the inverter whilst the engine was still running.

20 mins later the inverter started to squeal its warning - and this whilst the engine was still running!

As expected, once the engine (and the inverter) were switched off, all batteries were flat and could not re-start engine.

 

I take it that the inverter runs OK for more than 20 minutes with engine off? (Which would suggest a load on inverter which is not present unless the engine is running)

 

Iain

 

Edited to add : Cross posted with Gibbo

 

Edited to add wild thought : Immersion heater, which is only supposed to come on when shore power connected?

Edited October 1, 2010 by Iain_S

[blodger]

I'd do two things to observe the outcome.

 

1. Swop out the alternator

 

2. Swop out the inverter

 

Obviously, not at the same time and easier said than done if you have not alternatives to what is fitted; beg, steal or, borrow?

[WotEver]

I think you've got quite a big inverter and there is an additional hefty load on that you don't know about.

But what hefty load would only connect when the engine is running?

 

Makes no sense to me, this.

 

Tony

[Gibbo]

But what hefty load would only connect when the engine is running?

 

Makes no sense to me, this.

 

Not a clue. Definitely something silly somewhere.

 

The easy solution is to borrow a DC clamp meter and see where the power is going. Should take about 3 seconds.

[smileypete]

HOWEVER

 

If I run my engine and try to use my inverter whilst is running the batteries drain flat.

This is true even if I switch my inverter on after the engine has been running for an hour already.

When I say the batteries run flat this refers to all of the batteries including starter, making it impossible to re-start the engine after switching it off.

 

...

 

Any ideas as to what the problem could be?

What's the battery voltage and current doing while the engine is running and before/during/after the inverter is switched on?

 

What energises the split charge relay? Where is the battery charger plugged in?

 

cheers,

Pete.

[Keeping Up]

Trying to think of an oddball solution - does the inverter actually work properly after you've switched it on with the engine running? Just wondering if there's a faint possibility that the inverter objects to the high battery voltage during charging and stops oscillating so that it presents a high current drain to the batteries - or something like that?

[tonyreptiles]

I take it that the inverter runs OK for more than 20 minutes with engine off? (Which would suggest a load on inverter which is not present unless the engine is running)

 

Iain

 

Edited to add : Cross posted with Gibbo

 

Edited to add wild thought : Immersion heater, which is only supposed to come on when shore power connected?

 

 

Yes, I get a good day and a half of trouble free work time after 2 hours of engine running.

There's nothing aboard that could pull power - no TV/Games console/Fridge/immersion heater. (I have a gas boiler)

Just lights, car radio, laptop and occasional phone charger and water pump.

 

The cruncher is that the batteries are fully drained by using the inverter whilst the engine is running.

 

Aaaaaaggghhhh!

TR

[alan_fincher]

The cruncher is that the batteries are fully drained by using the inverter whilst the engine is running.

So, for a start, would it be possible to temporarily introduce a basic multimeter directly into the feed to the inverter, to prove what current it's drawing with the engine running, and without.

 

Is the inverter fused ?

 

Presumably it can't be drawing a lot more than the value of any in-line fuse it has, or that would blow, (although many fuses will carry a current quite a bit more than the actual value stamped on them).

[Keeping Up]

A basic multimeter may well be destroyed if the inverter is taking a very high current.

 

I still think my first check would be to see if the inverter is actually producing 240v ac when the engine is running

[Chalky]

Silly question but have you checked the alternator belt? I've seen this before on a car where it would start at night to go home from work, but not the next morning. The reason was that at night there was a heavy load on the alternator (headlights, heated rear window & fans) and the alternator couldn't charge the battery. In the morning it was light and the the loads weren't on. It charged ok. Your inverter & batteries along with the batteries could be presenting the same load. The belt did not appear to be slipping but when replaced and re-tightened it was fixed. Took me ages to get to the bottom of that one.

[alan_fincher]

A basic multimeter may well be destroyed if the inverter is taking a very high current.

Correct, of course!

 

That's not what was in my head when I typed it - I meant to say ammeter - i.e. just a cheapy old style in-line moving iron type.

 

Of course if the OP could borrow a clip on type that could handle DC amps, he'd not then even need to disturn any wiring to do such a test.

 

Sorry - I hope I've not caused him to destrow a multimeter, (although some are fused, I think ?).

[Chalky]

What's the voltage across the batteries with the engine running and no inverter and with the engine running and the inverter? This would give you an indication if the alternator can produce the current. If it can't I'd look for a mechanical solution first - drive belt etc. The charge warning light tells you that the alternator can produce enough power to self excite, it doesn't tell you that it can charge the batteries.

 

Also have you tried pulling the domestic fuses/turning off the domestic power and just leaving the inverter on with the engine running. This would give you a clue if you've got something in the domestic system that's causing a problem. If things are OK then put the fuses back in 1 at a time until the problem returns - that will show you the problem circuit.

 

If you've not got an ammeter sometimes the battery cables can have sufficient volt drop to act as shunts and allow you to measure the current, however if you can use that trick your cables are too small.

 

You say that you have a split charge using a relay and that both battery banks go flat. Is there a voltage sensitive relay controlling the split charge relay or not. If not then adding one should at least stop the starter battery going flat.

[ditchcrawler]

Several people have tried to get to the bottom of this problem without success.

Can anyone here solve it?

 

The set up:

1 x Starter battery

2 x 110 Leisure batteries

Split relay

Inverter

Running a laptop and occasional phone charging

No fridge

No TV

 

After running my engine for a couple of hours I get enough power for around a day and a half of working on my laptop.

I turn the inverter off when laptop battery is full and on again after it has drained.

 

HOWEVER

 

If I run my engine and try to use my inverter whilst is running the batteries drain flat.

This is true even if I switch my inverter on after the engine has been running for an hour already.

When I say the batteries run flat this refers to all of the batteries including starter, making it impossible to re-start the engine after switching it off.

 

I know I am getting plenty of charge from the alternator as the batteries charge fine if I don't use the inverter during that time.

They also charge fine via the battery charger.

 

Any ideas as to what the problem could be?

 

Cheers

TR

You mentioned Battery Charger, I don't suppose that your inverter is feeding 240 volts to your charger and the charger is trying to stuff it back into the battery. The higher voltage from the charger shutting down the alternator regulator.

[WotEver]

You mentioned Battery Charger, I don't suppose that your inverter is feeding 240 volts to your charger and the charger is trying to stuff it back into the battery. The higher voltage from the charger shutting down the alternator regulator.

Hey, now that's a good thought.

 

Tony

[MtB]

Hey, now that's a good thought.

 

Tony

 

Yes possibly, but this doesn't explain the flat starter battery as well as flat domestics. I think we can conclude the split-charge relay is not working correctly at least!

 

Mike

[Iain_S]

Yes possibly, but this doesn't explain the flat starter battery as well as flat domestics. I think we can conclude the split-charge relay is not working correctly at least!

 

Mike

 

But it might be doing what it's told If it is wired from the engine start switch or an oil pressure sensor, it won't disengage. Wired from "F" or "W" on the alternator, it won't disengage if there is any alternator output at all.

 

In the battery charger scenario, I'd expect even a Smartbank to maintain the connection between the batteries until the invertor cut out and the charger voltage disappeared.

 

Iain

[Radiomariner]

But it might be doing what it's told If it is wired from the engine start switch or an oil pressure sensor, it won't disengage. Wired from "F" or "W" on the alternator, it won't disengage if there is any alternator output at all.

 

In the battery charger scenario, I'd expect even a Smartbank to maintain the connection between the batteries until the invertor cut out and the charger voltage disappeared.

 

Iain

This seems the most likely explanation as to why it is both batteries that discharge.

The best sugguestion so far I think is the loose belt. OK under normal use, but the load when the inverter is on allows slippage and batteries discharge through the thus non productive alternator.

It is worth a try

[Pretty Funked Up]

I'd put my dollar on the charger running off the inverter as well.

If its a split charge relay, then it will drain both banks. If its a splitting diode, then its probably faulty.

Has the op. tried unplugging the charger and then testing? (check belt tension for good measure)

[Iain_S]

I'd put my dollar on the charger running off the inverter as well.

If its a split charge relay, then it will drain both banks. If its a splitting diode, then its probably faulty.

Has the op. tried unplugging the charger and then testing? (check belt tension for good measure)

 

Although why doesn't this happen when the engine is not running, even discharging the cabin battery only?

 

I think we've reached the stage when more investigation is required by OP.

 

Iain