Technical - Alternator or Inverter charging?

[weldted]

Ahh!, I see many thanks.

[aandncaravan]

Sorry forgot to attach the chart, probably the effect of 'Chemo Brain', so attaching it now.

 

 

May we point out that the reason this works for Weldted is that his Inverter is connected to the Starter battery, the results may be very different if your Inverter is connected to the Habitation battery as is the norm.

 

Where the Inverter is connected to the habitation area batteries, we strongly suggest you don't run the Inverter with any load if the engine is started.

[weldted]

Update, 18 days later.

 

Please note, my inverter is connected to my STARTER BATTERY not the leisure ones. Boxer 130 but engine battery is the one specified for the three litre.

Procedure as follows start engine, turn on inverter. Fridge (ses) set to auto mains battery charger on.

Fridge switches to mains voltage, appears to run cooler than when on 12 volt or gas, batteries recover to a higher rate of charge than when on 12 volt from engine alone. As to conflict of charging systems, I have 300 watt of solar a mix of 2, 90 watts 3, 40 watts all 17.5 volt. Linked to one junction box on the roof with 4 mm cable, then 6 mm cable down to Solar Boost 2000E blue point Mppt controller, then 8 mm to batteries.

240 volt supply via 2000 watt pure sine wave inverter when engine running under passenger seat plenty of space around to allow free flow of air for cooling fans, remote control easily reached from drivers seat. On board mains charger 20 amp starts of at 14.4 volts drops down to 13.8 when sufficient charge is reached. Plus split charge relay also charging leisure batteries when engine running. A right mix and match confounds all principles but for me it works. So far not needed mains hook up. Just have to remember to switch off inverter when parked. Solar panels around 10 years old, engine battery 3 years old, inverter 5 years old. In Portugal (raining) Hard hat on await comments!!

[Tracker]

Happy, if wet, New Year Ted, I'm no electrical expert and I suspect many other will wince at the complexity and cost but I think it's a brilliant system in it's conceptual simplicity, if somewhat more complicated in the actual practical execution!

 

I reckon you could make a good living fitting it to other's vans, those amongst us fed up with the umbilical cord syndrome and lack of true independence so beloved by so many!

 

I am not criticising, far from it, but for us just plenty of good leisure battery capacity and enough miles to recharge them properly satisfied most of our needs most of the time and we even did without any solar supplement in the later years as I understood batteries and charging more - mainly thanks to Alan and a few others on here.

 

Good luck and enjoy the rain - hopefully it is at least warmer than our rain!

[weldted]

Depending on requirements I suppose is the main factor, but being an inquisitive soul blessed with what if, led me to experiment. I am probably not the best at explains things in the simplest of terms but with fairly heavy use of tv and sky dish led me to establish this set up. Once fitted the only control required is turning the inverter on and off. Beacause my Elddis ehu socket is in a locker with a cut out for the cable my lead from the inverter is inside the van and rather than have any switch gear only either the lead from the inverter or the mains power lead can be plugged in at any one time so no possibility of two mains power sources at once.

[weldted]

Hi, would welcome your thought as the subject seems to have run out of comments.

Now on day 22, all wild camping no mains hook up at all. Very pleased with system so far. Fridge definitely runs better on inverter than 12 volt or gas. Have notice if I have been driving and using inverter, if I switch the inverter off with the engine running there is no charge going in from the alternator for a few mins but then start to show charging. If I turn engine off with inverter on input stays the same. Does this mean the split charger is not putting any charge in whilst inverter is running and letting the mains charger take over. The rate of recovery of the batteries is definitely much better using the inverter to run the mains charger than relying on 12 volt alone.

[aandncaravan]

"Hi, would welcome your thought as the subject seems to have run out of comments.

Now on day 22, all wild camping no mains hook up at all. Very pleased with system so far. Fridge definitely runs better on inverter than 12 volt or gas. Have notice if I have been driving and using inverter, if I switch the inverter off with the engine running there is no charge going in from the alternator for a few mins but then start to show charging. If I turn engine off with inverter on input stays the same. Does this mean the split charger is not putting any charge in whilst inverter is running and letting the mains charger take over. The rate of recovery of the batteries is definitely much better using the inverter to run the mains charger than relying on 12 volt alone"

 

 

Most Fridges are better on Gas and 240v than 12v, usually by a significant margin.

 

It depends on how efficient your Alternator charging set-up is. It is likely to be less efficient than a mains charger, especially if the Alternator is also providing 17amps Fridge 12v power, .

If the Alternator is slightly lower voltage, which I would expect on your vehicle, then the mains charger should dominate the charging and the Alternator should 'rest'.

But after you stop the mains charge from the Inverter the Alternator should slowly wake up and start putting in a charge which will depend on how charged the battery is.

 

If you turn off the engine and leave the Inverter on, it will go on charging the Habitation battery by draining the Starter battery, even if the engine is not running.

If you are concerned about this you could fit a 230v relay that interrupts 'mains' power to the charger, when D+ goes negative, i.e. the Alternator stops turning. When the Alternator starts spinning and the D+ signal becomes a 12v positive output it will re-energise the relay.

But suggest you carefully label the relay and wiring as handling 240v as many people might assume it is pure 12v.

 

 

Glad it is all working well, you have designed a clever, flexible solution to several issues.

 

 

[Alanb]

Perhaps I have missed something along the way, but it is my understanding that the "system" is comprised of an inverter powered from the starter battery, which is in turn supplying the onboard mains charger. This is in effect a B2B charger, but has the additional capability of running the fridge from the 240V output of the inverter.

The system becomes complicated by the fact that the original split charge circuit is still functional. This will effectively link the charger output back to the starter battery. In order for the system to comply with the laws of physics, a current will have to flow from the charger output via the split charge relay, associated wiring, and fuse, to the starter battery. (Chasing it's own tail .)

 

The above current flowing back via the split charge circuit will be such that the product of it and the circuit resistance is equal to the voltage difference between the charger output and the starter battery.

 

That is I(f) x R(sc) = V(diff),

 

Where I(f) is the current flowing back to the starter battery in Amperes

R(sc) is the total resistance in Ohms of the split charge path (including return path).

V(diff) is the voltage or potential difference in Volts between the charger output and the starter battery.

 

Resistance and voltage difference will be small, but the current could be several Amperes.

 

If the split charge circuit could be disabled, perhaps by removing the appropriate fuse connecting to the starter battery, the charger would only have to feed into the habitation battery. That should further increase the habitation battery charge current.

 

However if the vehicle is driven for sufficient time for the charger to drop back to its maintenance voltage, that is below the alternator output voltage, current would presumably flow in the normal direction, with little or no output from the charger. In this condition removing the fuse would seem prevent any charge going into the habitation battery.

 

As I said, have I missed something?

 

 

Alan

[weldted]

Whilst there are contributors with a greater depth of electric circuitry than myself, I can only offer the following. We are now at day 25 without hook up. whilst we are having a good deal of sunshine in Portugal the sun is still very low. I have been running with the inverter on whilst driving and have definitely seen an improvement in the condition of the charge rate to the batteries. The ses fridge is set to auto and when the engine is started it goes from gas to 12 volt which at idle 900 revs app my meter shows around 7 amps discharge from the leisure batteries recovering when in excess of 1200 revs. When the inverter is switched on the fridge switches to mains voltage and there is a charge in excess of 20 amps going into the leisure batteries. The charging rate falls as the batteries come up. As said before if I turn the engine off with the inverter still on the charging rate stays at whatever is shown on the meter. If the inverter is turned off with the engine running the charging rate drops to zero but a few minutes later the charging rate climbs up but not as high as when on mains charging.

[weldted]

Last post 31 days no hook up needed, mixture of long and short runs, three or four days parked up, some sunny spells but sun low, several overcast days. I would say on short runs two to three hours a definite increase in battery charge not so much on long runs, probably as stated on a previous post charger falls back to 13.8 when batteries are up and cuts out the split charger. Fridge much better running on mains when travelling, no noticeable increase in fuel consumption.

[benr8440667]

Good evening gents...

I have been looking at this thread with much interest. May I just quote Allan (aandncaravan)

“Where the Inverter is connected to the habitation area batteries, we strongly suggest you don't run the Inverter with any load if the engine is started”

please could someone please explain the reason for this warning? I am concearned as I have recently installed a large 2000w inverter wired in parallel to my pair of habitation batteries. I was thinking that i could just run my engine to help keep the batteries topped up whilst using large inverter loads. (e.g. microwave) for short periods. It sounds like i have made an error here! (p.s. as you may have guessed I am a relative novice with electrics, particularly the theory!) Many thanks.

 

 

[aandncaravan]

In most Power controllers, particularly on Continental built motorhomes, the Split charge relay mechanism is inside the Controller/charger. Therefore any current from the Alternator to charge the habitation batteries goes through the charger/controller then on to the habitation batteries.

If an Inverter is connected to the habitation battery and trying to pull 140amps from the Alternator through wiring and connectors designed for less than 50 amps, then something is going to give.

 

Have a look at our 'Add a second battery' webpage as it shows how adding just the load of a second battery to be charged by the Alternator can affect things and introduce fire risk : http://www.aandncaravanservices.co.uk/add-a-second-battery.php

 

 

Even on those vehicles with a separate Split charge relay, they are not usually designed with more than about 40 amp current handling as the Spade connectors/wiring to the relays are often just 6.3mm. The relays are rarely greater than 75amp versions.

 

 

We had one Motorhome in that had a burnt out control unit, a Calira 38/20, because the Dealer had converted the 'Mains only' roof mounted Aircon to run from an Alternator powered Inverter connected to the habitation batteries. All of the 120 + amps from the Alternator went down wiring not designed for that current, then through the Calira which burnt out.

 

 

Hence why we say above to run the Inverter directly from the Starter Battery/Alternator.

Although the Inverter is connected to the Starter battery, if everything is sized correctly the Starter battery won't supply any current, so long as the Engine is running at a speed needed to create that power, like a fast idle/mid engine speed.

 

 

However, I have my doubts about any Alternator based system supporting a load as big as a Microwave?

 

 

 

 

[benr8440667]

Thanks for responding to my question.

I have used the microwave (700w) with the engine running and it worked fine. Nothing seems to have melted yet. But from what you are saying it sounds like I may have been lucky. So am i to understand that if the inverter is drawing say 100 amps from my habitation batteries then this would be fine when the engine is off (assuming an adequate battery bank is in place) but if im running the engine whilst the inverter is drawing 100amps from the habitation batteries then the inverter will try and draw 100amps from the alternator instead of from the habitation batteries via the charging circuitry between the alternator and hab batts. And the problem with this is that the motorhomes standard wiring, alternator, battery charging system, etc are not capable of handling such a large current draw?

[aandncaravan]

If your Alternator is low power and/or it was spinning only slowly, then the power the Alternator would be able to provide might be very small, maybe as little as 15amps with the engine idling on a vehicle that age? Hence making the point, " so long as the Engine is running at a speed needed to create that power, like a fast idle/mid engine speed"

 

That is maybe why you had no issues, all the power was from the batteries with the Alternator not able to contribute anything through the engine idling or it being an older 90amp unit?.

 

I can't say if your Motorhome is capable of handling that load or not, it may have been modified over the years, but most modern standard systems will struggle.

 

In a nutshell yes, your summary is about right.

 

 

 

 

 

 

[benr8440667]

I’m fairly sure my vans electrical setup is still fairly factory, aside from the inverter which I have added. Now that it has been brought to my attention that i could potentially cause damage to my motorhomes electrical system running the engine whilst drawing large inverter loads from the habitation batteries, I will only use high power appliances with the engine off. I suppose i will need to add another battery or two to my existing pair (i will do my homework regarding overloading and indeed destroying my system with an increased battery bank, as your link above clearly shows!) to allow me to use the microwave, kettle, etc. I also plan on adding some solar panels to charge the hab batts. I dont think wiring the inverter to my engine start battery will suit my needs as i will be running various small ac loads, freezer, extra beer fridge, etc constantly whilst off mains ehu. So I would flatten the battery. Also it sounds like my alternator isnt up to the big loads anyway. Once again many thanks- I am extremely appreciative to you for giving up your time to share your expertise. Top bloke.

[benr8440667]

Hi again Allan. Can i say that i spent a couple of hours reading through the guidance section on your website (aandncaravanservices.co.uk) lastnight. The amount of good information that you have put on there is immense. It made my brain ache eventually! I wish I had stumbled across it before I fitted my inverter as i may have proceeded differently having read some of the stuff you have put on there. I advise anyone who plans on making any electrical modifications or repairs to their motorhome/caravan to read through that first. You seem to have included sections advising on just about everything i have wondered about doing to mine. Great work- Many thanks for posting it all online for the benefit of all and for highlighting it to myself.

[weldted]

Now back at French cottage, 63 days away, no hook up, ses fridge set to auto always switched to 240 when inverter on and mains battery charging with engine running, used microwave several times, can use up to fifteen mins (800 watt) without running engine any longer run engine to protect ability to start, charged Gtec multi numerous times whilst travelling, kept two iPhones and one iPad charged (USB via 12 volt) noticed iPad consumed app 1 amp at 12 volt when charging (all adds up) had some help from 300 watts of solar two 100 amp batteries. but sun still low except towards the end of the holiday a quite a few overcast days, mixture of 3/4 days parked up some long runs etc. Very pleased with result as opposed to previous long holidays just relying on solar and driving. No noticeable increase in fuel consumption 5,800 miles travelled. But please note the inverter is connected to my engine battery not the leisure ones.

[Tracker]

Sorry to run off topic Ted but I can't find the original thread - did you resolve your steering / handing issue?

[aandncaravan]

Weldted, I think you have created a really nice solution to several issues.

That it clearly works well without fundamentally altering or bypassing the 12v Charger/controller at the heart of a modern motorhome means you won't suffer the side effects that sometimes result, like when fitting 'conventional upgrades'.

 

It is simple, so very easy to remove to revert the vehicle back to standard later.

 

 

The only thing I would suggest you are careful with is running a high load, like the Microwave, without the engine running at fast idle.

Although the Starter battery might still start the engine after 15 minutes of Inverter/microwave draw, to provide that level of current on it's own the Starter battery will have been stressed significantly.

I am guessing the power taken from the Starter battery will be around 100amps for 15 minutes, if so that is a heck of a lot to ask of a battery and you might find it's life is less than a couple of years?

I would suggest you always run the engine at fast idle when the Inverter is in use, that way the Starter battery will be more within it's comfort zone.

The higher 14.4 voltage of the Alternator should also assist in making things more efficient.

 

If the battery does need replacement in the future, can we suggest it is replaced, not by the usual Varta LFD90 recommendation, but the larger L1 (020 and 110Ah size) usually allocated to the 3 litre engine?.

 

 

Congratulations on creating such a simple, effective solution by clever lateral thinking.

 

 

[weldted]

Thanks for your comments Allan, engine battery is the one fitted to the three litre engine, normally engine is running if microwave run for more than five mins. But on an odd occasion have run for a bit longer without engine on such as a late stop to be considerate to others. Other than that very pleased with results.

[weldted]

Hi Tracker re the steering, van has been examined by Peugeot and an control tech no obvious faults discovered. I have also gone through everything myself, when I fitted the semi air, everything was torqued down van driven for about ten miles torqued again. Just check torque again all correct no sign of any movement have taken everything loose out of van, weighed it 3560 kg still same problem? Have ordered two 225/70 R15 agilis camper car tyres so all four will be the same, but I don't think that is the answer.