A 5,000 watt inverter has burnt out my Power Controller/Charger

[aandncaravan]

If you read the enquiry below that has come through today, you will see a few flaws in the installation.

The enquirer has connected a 5,000 watt Inverter to his habitation area batteries and uses it to power the 1,500w 230v Air Conditioning Unit while driving.

With losses, the 75% efficient Inverter probably tries to draw about 150 amps from the habitation batteries.

 

All the power the Alternator can muster will go through the Arsilicii Charger/Controller and then onto charge the hab batteries and ultimately the Inverter.

 

You can see how passing 150amps through a Charger/power controller designed for around 20 amps might burn it out?

But better than that, the Arsilicii AL310 power controller, which is also the 'Split charge relay', is about 15 years old suggesting the Alternator power is probably less than a 110Amp?

 

So after around 40 amps is taken off the Alternator's 110a cability to run the engine, etc. it leaves about 70 amps to replenish the 150 amps taken from the habitation batteries by the Inverter.

That assumes the Alternator can run flat out and doesn't melt in the process.

 

Clearly the inability of the Alternator to replace the current being drawn will lead to the Hab batteries discharging during the drive, probably in less than 2 hours.

 

 

He was sold the Inverter, with advice given on how to install it to run the Air Con, by a big name 'electronics' accessory company.

 

The enquiry we received went :

"Hi , I’ve just read through your wed page on the split chargers , very informative! And greatly appreciated. I currently have the Arsilicii AL310DF unit , and I’m having issues with the burnt out connectors on the unit. My system consists of 2no 110Ah leisure battery’s.

Reading through your information it seems I need to up grade my AL310 charger/controller. Can you supply one to suit my requirements please ? Also I’m feeding a 5,000w inverter which runs an AC unit while driving ( only running at 20>25% output , so not using to full 5,000w). this inverter is wired directly to the battery bank. Would this draw from the inverter through the battery bank cause a back feed into the split charger , and can I do anything to stop this using a different system?

Many thanks in advance, if you could provide one of your products I will gladly purchase directly from yourself.

Regards M".

 

 

They are probably lucky the Arsilicii burnt out, as it is a lot cheaper to replace than an Alternator.

 

We declined to supply any kit that would just melt on the next use.

 

 

 

[aandncaravan]

I have had an email saying I am wrong in the way I am quoting Alternator power ratings in the post above.

 

The emailer states that while a 120amp Alternator might be able to cope with a peak of 120amps for a very short period of time, it will overheat and burn out if asked to deliver that for more than a few minutes. The rating is peak, short term use only.

 

The continuous power capability is likely to be just 60 amps for a 120amp rated Alternator, around half of the Alternators rated output but maybe 2/3rds for a heavy duty Alternator.

 

He sent me links to a specialist web site https://www.zena.net/htdocs/alternators/alt_inf2.shtml where this is discussed.

A brief extract added here -

 

"...... it cannot produce this amount of power for more than a few minutes without overheating and potential damage.

The most power that such an alternator can be expected to provide continuously is about 1/2 the maximum rated output power -- maybe as much as 2/3 for a "heavy duty" design".

 

 

So, not liking to be 'wrong' I spoke to someone we used to get our spares from in the days when we rebuilt Alternators, and he has confirmed the above But he says 65% of the rated output is probably more realistic as a continuous current draw for a Motorhome Bosch unit, probably less for the Lithuanian 'copies'.

He cited the Astra 1.7 Diesel 70amp Alternator as an example because it's vacuum pump restricts airflow into the Alternator making it prone to overheating if it is used hard.

 

 

I didn't think that alternators would love running at peak output for long, but didn't realise the continuous draw rating was so low.

 

 

One other 'interesting' fact was that a motorhome Alternator could deliver over a third of it's rated output at idle. I had thought it would be just a handful of amps until the engine got up to a fast idle. He'd had in a 180amp upgrade Alternator in for rebuild that delivered 65amps at idle versus the '100' versions 30amps.

 

I guess I am still living in the days of a 70amp Alternator!!

 

 

 

 

[mikefitz]

Hi Allan, very interesting report on alternators and a poor electrical installation of an air conditioner.

 

I am more familiar with the leisure boat market and inadequate electrical installations. The poor boat owner is often is a much worse situation than a motorhome owner when he discovers a faulty system on arrival in the Canaries or the Caribbean that was installed in Southampton, or worse still has problems in the middle of an ocean.

 

I am not fully aware of all the facts in your report so my assumptions may be incorrect.

 

You say the enquirer had a 1,500w 230v Air Conditioning Unit, if the 1500w refers to cooling watts then the actual power requirement is around 650 watts of electrical energy This would reduce the current draw from the batteries to quite a bit less, say 70 amps.

 

However, this is still far too much current to pass through the motorhome electronics that has small cross section area wiring and low current capacity relays.

If the installation had been carried out correctly with heavy duty cables and relays I think it could have been successful, subject perhaps to the alternator being up rated.

 

Your enquirer was given poor advice. For Dometic air condition units, all the information for installation is available from Dometic together with suitable inverters and installation kits.

 

As for alternators, I agree that their continuous output is less than the rating, but suggest this is down to the mechanics rather than a ' burn out ' limit. I wont comment on the information from Zena, other than to say that they are trying to sell their product!

 

For example if we take the 150 amp alternator fitted to many Fiat vans and motorhomes, its actual maximum output at typical engine cruising speeds is around 100 to 120 amps.

 

At idle I can confirm that even with the standard 150 amp alternator, 50 amps plus is available at 800rpm.

 

I have added a couple of graphs pulled from the internet showing the output at various speeds. A typical 140 amp car alternator and a special Zena high output alternator

.

Mike

[aandncaravan]

Thank you.

The 1500w was at 230v, Michael has since measured the actual 12v current using a clamp meter at 135amp, so a bit lower than my 150a estimate.

 

But even if a successful setup could be created with a mega 220a alternator, as your chart shows the charge drops off, the minute the vehicle hits traffic and the engine drops to idle speed.

Depending on how long the drive is in town, will determine how much the Habitation battery discharges.

 

 

 

 

 

[Keithl]

It sounds as though he'd be better with a 2,000 W generator strapped to the rear bumper :D

 

Keith.

[plwsm2000]

I don't quite see the point of having AC only while driving unless the person does not have cab AC. My cab AC does a reasonable job of keeping us cool while on the move.

When stationary (obviously no alternator current), the hab batteries would not last more than an hour or two even with a large battery setup with a 75Amps draw on them.

 

[aandncaravan]

plwsm2000 - 2018-05-17 7:54 AM

 

I don't quite see the point of having AC only while driving unless the person does not have cab AC. My cab AC does a reasonable job of keeping us cool while on the move.

When stationary (obviously no alternator current), the hab batteries would not last more than an hour or two even with a large battery setup with a 75Amps draw on them.

 

His decision for going this route was explained in a later email -

 

"But for my needs , To keep cool while driving on the continent this was my only option rather than install AC into the cab at a cost of @ 2.3K....( I’m well below this cost using the inverter )".

 

When decent ceiling Air Con costs around £1800 + Inverter + ultra heavy duty battery bank, etc he can't be far off £2.3k? Especially now he has burnt out the £390 Arsilicii Power controller/charger.

 

I think once he adds on the running costs of a set of destroyed batteries and new £700 Alternator every 6 months, he may change his mind?

 

 

The Dometic 'DC' kits apparently get around the issue by including a battery voltage monitor that just shuts down the aircon for long periods of time if the Alternator is struggling. I suspect it also includes a charger to bypass the Arsilicii Controller.

 

 

 

I suspect Mr Fiat didn't anticipate anyone would be mad enough to run a 180amp Alternator flat out for hours at a time when he designed all the drive pulleys and belts?

If you add this 135a Inverter draw to the potential 35amps for the engine ECU, Injectors, radiator fans, lights etc. that is pretty near a maxed out 180amp alternator.

I can see that getting very hot and literally burning out.

 

 

Bosch have just introduced a 'temperature protected' Alternator for trucks because so many get driven to their limits in modern trucks and fail through overheating. The Alternator has circuitry that backs down the charge if it starts to get hot. That indicates that the cooling design of alternators, even these new 'protected' ones, isn't adequate for long term running near peak power.

 

 

With the above type of kit being sold and some of the huge battery banks out there, maybe a 250a version would be a good idea as standard fit in a Motorhome?