Camper van electrics

[Diver Fred]

Can you clarify please - when you say the van electrics shut down do you mean the Leisure side of the van electrics but not the vehicle side - so the engine will start or do you have to jump start the van?

 

[Harry Bloomfield]

Do failing batteries just stop delivering any power at all if overloaded.

The battery voltage will deteriorate.

 

[Harry Bloomfield]

For boats you can't have gas as they need a vent underneath them and if fitted the boat sinks.

So they are often compressor type, which use less power and cycle on/off.

Boats do have gas on them.

Absorption fridges do cycle on and off, or rather - the flame can adjust up and down to control the internal temperature.

 

[ericmark]

Back in early 70's we had blocking diodes and split charge relays, in theroy the blocking diode was best option, but in practice the 0.6 volt drop across the diode slowed down the charging, so the relay worked better, often double contacts one for fridge direct, and other to charge leisure battery, the BS 7671:2008 stipulated how the two supplies should be used, and to comply some sort of relay in the caravan was required, with a motor caravan not limited to 13 wires, so there are other methods available. But at 13.8 volt typical for most vehicles, the charge rate was very low, using an ammeter I would see maybe 30 amp for first few minutes after starting engine, but then it would drop to around 3 amp, with narrow boats with same system cruising all day (8 hours) was not enough to recharge the batteries, and with caravans and motor homes the engine likely runs for a much shorter time.

Two major problems arrived, one was the car turning off alternator under load, and only charging on over run, and the second was if the supply to caravan was lost it could also result in the loss of the anti snake system. So a major rethink was required. With caravans the problem was is the device fitted in the caravan or the tow car, this is not a problem with motor caravans, the device is the DC to DC inverter, this does all what the relays and blocking diodes did in the past the aim is to charge the leisure battery, but ensure it is disconnected from the starting battery when engine is cranked, also to ensure the fridge is only supplied when engine is running, the latter still normally uses a relay, but the DC to DC inverter also stops back feed so no relays or blocking diodes are required, and it can also stage charge the battery.

Stage charging has been for years the norm with mobility scooters, fork lifts and milk floats, but today it has moved to another level, in some cases up to 7 stages, basic idea is charge flat out until the voltage reaches 14.4 or 14.8 depending on type of lead acid used, then hold the voltage at that setting until the amps drops to a pre-set level, then drop the voltage to around 13.4 volt this should happen when battery is around 80% charged.

However there is a problem when the battery is used at same time as being charged, as the pre-set amps at which it drops the voltage may never be reached, so there is another system where the battery is pulse charged, often used with solar panel chargers, and narrow boats, Sterling Power seem to be the leaders in this, with some really large units, mainly aimed at the narrow boat.

Basic idea is it charges, then stops, and reads the decay in voltage to work out how much charge is required, they can also combine the output of two alternators, it is common for narrow boats to have one alternator for traction battery and one for the leisure battery.

Since there are fume dangers in using gas powered fridges these with narrow boats have been replaced with compressor type units, with are all electric, the absorption fridge is normal for a caravan which can be 12 volt, 230 volt and gas, the Peltier is the other method, uses DC only, not very efficient but popular with cool boxes as it can heat or cool by swapping polarity.

The voltage activated relay was very popular at one point, and can be used to power the fridge, so it only runs when the battery is charging, but as you can see over the years there have been many methods used, job one is find out what you have, also some systems can work against each other, the vehicle alternator could stop solar panel working and visa versa.

Durite and Ring also may systems, the mppt and pwm solar panel controllers often have an output for equipment so the controller knows how much is being used, they also often have duel inputs for solar and wind generators.

Although still lead acid, the absorbed glass mat or valve regulated lead acid needs more careful controlling and often the engine management computer controls the charging, we have moved on since the 70's, and even in the 80's some batteries did seem to fail fast, I know the Chevy sealed batteries would not give much warning they were going flat, sorry should say discharged, shape does not alter.

Although I have seen narrow boats with fridges worked on battery, they tend to have at least 330 Ah of battery, often more, they also carry ballast so weight of battery is not a problem, they just remove some ballast, but with motor caravans the weight of the battery is a problem, so normal is to use mains or gas when parked, and 12 volt only when moving from site to site.

But if you detail what your system is, then easier to advice.

 

[ericmark]

Boats do have gas on them.

Absorption fridges do cycle on and off, or rather - the flame can adjust up and down to control the internal temperature.

I am sure there are ways to fit gas fridges on a boat, but I am under the impression it is hard to comply with the RCD with gas fridges? (RCD = Recreational Craft Directive) my point is for boats the 12 volt compressor fridge is preferred, with gas or 230 volt the output is controlled, sorry did not make myself plan there, but with 12 volt often there is no control, not always of course, exceptions to every rule.

The gas control has also changed, it use to use a pilot flame, but today often uses 12 volt to ignite the gas, I know years ago a small dumpy gas bottle powering only the fridge would only last 3 weeks, but now with no pilot flame they last a lot longer, however when I started caravanning around 1956 as a 5 year old the 12 volt was only used for one inside light until the gas lamp was lit, the water pump was foot operated, a dome in the floor, and even when we did start using electric water pumps there was a foot controlled back up.

The last caravan I had did not have a single gas lamp, I could run for around 2 days normal use on battery, maybe being very careful could last a week, where when I was a boy the battery would last a month, my dad would get same battery for car and caravan and swap them around every three weeks.

The habitation controls today get rather complex I know it took me some time to work out what the one in my caravan did, one shown is from a motor home. I know mine caused a problem with the new radio, as every time one plugged in the car, supply to radio was lost for a few seconds, which would cause the radio to switch on in demo mode. Had to swap fuse supplying radio to one live at all times.

But there are so many systems, one simply can't cover all the options one might find, and as an auto electrician back in the late 60's early 70's I still spent a few hours working out what the bank of 5 relays in the caravan were designed to do, and I would stand no chance of working it out remotely.

OK by 1980 I had moved to mains electrics, so my auto electrics knowledge was a little dated, still remember the third brush dynamo with free wheel though.

 

[Harry Bloomfield]

but with 12 volt often there is no control, not always of course, exceptions to every rule.

My three way, has control on mains, or gas - but none once on 12v. None is necessary, because the 12v wattage, is barely enough to keep the contents cold on the move. My routine has always been to run it on mains, for at least a day or two before setting off, and switching to 12v whilst in transit. If I stopped on route, over to gas for the duration.

The last caravan I had did not have a single gas lamp, I could run for around 2 days normal use on battery, maybe being very careful could last a week, where when I was a boy the battery would last a month, my dad would get same battery for car and caravan and swap them around every three weeks.

I quite liked the gas lighting, apart from the usual breakage of the mantles of the expensive in transit. I learned to stop that, by spraying them with hairspray. I would keep two caravan batteries, one on charge in the boot, one in use, before hook up's became common.

My current caravan has 12 to 18 lamps scattered around it, originally quartz task lights. I replaced those with LED's simply to reduce the load and the heat from them.

 

[ericmark]

There seems to be some special lamps now for caravans and narrow boats, most are 10 - 30 volt and also very good as to lumen per watt, typical Wattage: 2.8W Lumens: 353L (Warm White) or 365L (Cool White) so over 100 lumen per watt, but most house hold MR16 bulbs are no where near as efficient. However 350 lumen is not that much, and they are all designed for DC with a smooth supply expected from a battery, not the type of supply one would get from a switch mode power supply.

My dad wrote into a caravan mag with his suggestion to stop mantels breaking, it was a large washer and spring, he got a small payment, but it was then adopted by near every caravan manufacturer.

The heat from the lamps was often enough to keep caravan warm, without those gas lamps my last caravan had to have central heating to keep us warm, things did move on, old gas fires got the van very damp, new types had balanced flues.

But be it the air heating or the water heating, even when using gas, it still needed 12 volt electric control, so having a good battery charged up become essential, where early days one could do without a battery.

 

[SUNRAY]

Back in early 70's we had blocking diodes and split charge relays, in theroy the blocking diode was best option, but in practice the 0.6 volt drop across the diode slowed down the charging, so the relay worked better, often double contacts one for fridge direct, and other to charge leisure battery, the BS 7671:2008 stipulated how the two supplies should be used, and to comply some sort of relay in the caravan was required, with a motor caravan not limited to 13 wires, so there are other methods available. But at 13.8 volt typical for most vehicles, the charge rate was very low, using an ammeter I would see maybe 30 amp for first few minutes after starting engine, but then it would drop to around 3 amp, with narrow boats with same system cruising all day (8 hours) was not enough to recharge the batteries, and with caravans and motor homes the engine likely runs for a much shorter time.

But you wouldn't just add diode into the charging circuit and expect it to continue charging correctly would you?

 

[ericmark]

That was the standard Lucas CAV method. With the CAV regulator you had a Hi, Med, Low setting, but nothing with the Lucas, the new version uses a different type of diode. And I would with old Lucas alternators replace the three phase diode pack with a Durite one where the diodes for the excitation were same size as those to battery, and add a new set of three diodes for the excitation so alternator had two outputs. But as standard nothing. Today there are some replacement regulators designed to turn alternator in to a stage charging unit. But here is a copy of the instructions

As you can see nothing to lift voltage to compensate for drop across diodes.

 

[Old Salt]

My last gas boat

 

[SUNRAY]

That was the standard Lucas CAV method. With the CAV regulator you had a Hi, Med, Low setting, but nothing with the Lucas, the new version View attachment 306785uses a different type of diode. And I would with old Lucas alternators replace the three phase diode pack with a Durite one where the diodes for the excitation were same size as those to battery, and add a new set of three diodes for the excitation so alternator had two outputs. But as standard nothing. Today there are some replacement regulators View attachment 306786designed to turn alternator in to a stage charging unit. But here is a copy of the instructions
View attachment 306787
As you can see nothing to lift voltage to compensate for drop across diodes.

Well All I can add to that is it is b****y appalling, how can anyone expect that to work properly?

 

[ericmark]

Well All I can add to that is it is b****y appalling, how can anyone expect that to work properly?

It in the main didn't, it was good enough to work the single internal light in early caravans, but not really charge the second battery, only with the battery to battery inverter charging unit did we really start to charge the leisure battery.

 

[SUNRAY]

It in the main didn't, it was good enough to work the single internal light in early caravans, but not really charge the second battery, only with the battery to battery inverter charging unit did we really start to charge the leisure battery.

But what about the main battery?

 

[ericmark]

The main battery was closer to the alternator and did not seem to suffer having 0-6 volt less, the float charge for a lead acid is around 13.4 volt, but with the old cars we would set it higher than that, typical 13.8 volt some up to 14.2 volt, with the idea that it would average out, this applies to other items using lead acid like stair lifts, my parents stair lift was set around 32 volt, which worked fine if the stair lift was used 4 times a day, but when my father died it was only used on a rare time, and the batteries did not last.

Odd the Lucas dynamo was set to 16 volt open circuit, it never reached that voltage with a battery connected, but that was the open circuit volts taken from the Lucas workshop manual.

 

[SUNRAY]

From significant experience I'll say that setting the float voltage above 2.3V will kill the sort of batteries usually fitted in stairlifts fairly quickly. Speaking to someone, many years back, who used to work for a stair lift company advised me to reduce the float to 27.2 and the boost to 27.8. He also explained the need for work creation schemes in the industry

I have used those figures ever since and maintained large number of 12V 7 & 17AH for my portable use for a long time and way past those who used higher voltages.

Yes I recall adjusting both styles of Lucas regulator and yes I recall an unexpected open circuit voltage but they did revise that about 50 years ago to something like 14.8 IIRC when battery weights dropped as technology improved .