Leisure battery. Charging

[ivecotrucker]

I to some extent agree Steve121 that that was true of older alternators & possibly still is to some extent but modern alternators have come on a lot. Ours happily chucks out 14.3 - 14.4 V & around 5 - 10 A into a fully charged leisure bank that has just come straight off a mains-powered intelligent recharge.

 

[Steve121]

I to some extent agree Steve121 that that was true of older alternators & possibly still is to some extent but modern alternators have come on a lot. Ours happily chucks out 14.3 - 14.4 V & around 5 - 10 A into a fully charged leisure bank that has just come straight off a mains-powered intelligent recharge.

I don't doubt what you're saying, but 5 - 10A into a fully charged battery? That doesn't sound like a well regulated system.

I've got an older engine, dating from 1998, with a 24V military spec. alternator, so a split relay wasn't an option! I was lucky enough to find a brand new Durite 24V - 12V B2B for a mere £120 - much cheaper than fitting a second alternator (for which the engine has a mounting point).

 

[ivecotrucker]

Apologies Steve, I was being too economical with words. Initial charge will be up to c. 10 A but quickly falls to around 1 - 2 A (beyond accuracy of meter at very low currents) after a few seconds; I was just pointing out that modern alternator regulators are better than they were.
Sounds like you got a bargain there !!.

 

[sparrks]

My first thoughts were "Glad I inserted and that should give me sufficient room to back pedal." With respect to the stuff written by Charles Sterling. If you do take someones word as a given it's not comfortable when you read a piece by them that you doubt.

Then I was thinking about fast blow fuses and possibly using micro circuit breakers.

An interesting thread. Amazing what you can still learn about an old subject - thanks Sparrks, I never knew the figures on DC fuse blow rates were so poor, quite worrying & certainly food for thought.

Your link to Sterling is not what I'm talking about. Using a simple split charge relay means you will be relying on the alternator's regulator to charge your batteries. According to fairly extensive research I did a few years ago standard alternators do not allow batteries to reach anywhere near a full charge. A B2B charger uses advanced electronics, not diodes, to ensure close to 100% charge, presumably using similar techniques to those in sophisticated mains powered multi stage chargers.

The breaking currents and disconnection times I quoted are for 240v ac and are from the 17th Edition regs. However, I believe the current is the deciding factor not the voltage and to a lesser extent ac/dc. From the Bussmann catalogue a GG1000 Low Voltage Fuse Links to BS88 & IEC269 is as follows rated voltage ac = 1000v ac, 250v dc Interrupting rating 80kA@550vac and 40kA@250vdc - notice the much lower breaking current with dc as opposed to the rms voltage.

Note: To clarify the mention of GG1000 Low Voltage Fuse Links to BS88 & IEC269 see below

Table 2.1 - Voltage Classification

Extra-low Voltage Not exceeding 50 V ac or 120 V dc

Low-voltage Greater than extra-low voltage but not exceeding
1000 V ac or 1500 V dc between conductors
--600 V ac or --900 V dc from any conductor to earth

My purpose of posting was to show the difference in outcome between a short circuit and an overload situation, in the short circuit the fuse should blow instantaneously (or near as) whereas in the scenario referred to earlier with the discharged battery a large current could flow through the fuse but not be enough to blow the fuse for several minutes and maybe causing damage.

A B2B achieves the higher charging rate by boosting the charge voltage and holding that voltage for longer than an alternator would. I personally use one and am very pleased with it.

 

[molly 2]

Thanks again for all you comments. I did think about testing with a multi meter but was concerned about blowing. The meter as it has a 10 amp max. Not sure what would happen. If I over loaded the meter would it destroy the meter or just give daft reading. I am going to the seven bore meet for 4 nights and have concerns about running out of Leccy i was hoping that driving around would keep the battery topped up?,I have one 85 amph battery all led lights trumatlc blown air heating and a nesh wife How long is a piece of string hmmm.

 

[Tow Itch]

Thanks again for all you comments. I did think about testing with a multi meter but was concerned about blowing. The meter as it has a 10 amp max. Not sure what would happen. If I over loaded the meter would it destroy the meter or just give daft reading. I am going to the seven bore meet for 4 nights and have concerns about running out of Leccy i was hoping that driving around would keep the battery topped up?,I have one 85 amph battery all led lights trumatlc blown air heating and a nesh wife How long is a piece of string hmmm.

Quick sort of answer Molly.
Sorry I have sort of moved this on but If I get people who know better than I to help I think there are 2 main questions 1) the safety (I'd not panic for the moment) 2) how efficiently this sort of system charges.
But you might want some quick put me on answers. Everyone else I'll get back with a fuller answer and some questions later.

Yes XS amps will kill a multimeter.
How about not using the multimeter to measure amps but to give an indication of charge by measuring the voltage across the battery.
N.B. the voltage will deceive with an excessive reading when you have just charged because the plates have a surface charge. It will show less than a true voltage when you are discharging. The only true readings are after the battery has been left uncoupled for 6 hours or so. I realise that won't happen. Though you can get indications. Are you on you tod or is there someone else in the van? Can we hardwire the multimeter to the battery (Eventually you may choose a dedicated voltmeter) This is all so someone can observe what is happening.
Questions with a battery in good charge (12.70V plus) what voltage is showing across the battery when you first fire up the engine? I'm not sure what to expect as the starter battery will have a demand at this point. But if the voltage jumps to above 13.8 volts the rate of charge is better than you would get from a zig unit if on EHU. Every extra 0.1V is good right up to 14.5V especially at the start. After about 1/2 an hour or say 40 mins does the voltage drop? If so you have a thermostatically controlled alternator. What does it drop to?.
What sort of battery do you have? Wet Lead Acid Unsealed, Wet Lead Acid Sealed, Gel, Glass Mat, Other? This would affect the sort of charging you want.
A battery in full charge is generally +12.7V 50% charge 12.2V but remember 50% isn't 50% left it's the minimum charge you want in a battery as further discharge may damage future recovery. See Battery voltage and state of charge - Energy Matters Remembering what I said before about readings been affected by whether you charged or discharged the battery last.
You can gain a rough idea by looking at the wattages of the LEDs and dividing these by 12 and multiplying by the hours left on for the Amp hours used. The unknown is the heater. Propex are notionally (I've never tested one) pretty linear in their current drain Espacher Diesel heaters take a big whack of power on initial lighting Trauma? You could try to measure the current demand off the heater. Does it give an indication of the wattage of the blowers?

From your tale I've not perceived if the charging is coming from you driving down or if it's daily driving or you might have a drive 1/2 way through the 4 days?
Where did the 20Amp (Hours) usage figure come from?20 Amp hour over 4 days, per day? Truma power consumption did you get the figure from one of these pages? Truma - Trumatic E 2400 liquid gas heater
Fall back positions do you know people who you will be visiting, do frequent a local pub? Strapping chap to lift out battery and 4 or five hours on charge solves most problems.

There was a lot to be said for Trauma/Carver fires and Riviera heaters.


Sorry it's not what you need now but it can get down to practically seeing how far you can push things. Then applying practical experience, and if you can afford or want different possible solutions.
Do hang in as we may get some positive points from this by the end.

 

[molly 2]

Quick sort of answer Molly.
Sorry I have sort of moved this on but If I get people who know better than I to help I think there are 2 main questions 1) the safety (I'd not panic for the moment) 2) how efficiently this sort of system charges.
But you might want some quick put me on answers. Everyone else I'll get back with a fuller answer and some questions later.

Yes XS amps will kill a multimeter.
How about not using the multimeter to measure amps but to give an indication of charge by measuring the voltage across the battery.
N.B. the voltage will deceive with an excessive reading when you have just charged because the plates have a surface charge. It will show less than a true voltage when you are discharging. The only true readings are after the battery has been left uncoupled for 6 hours or so. I realise that won't happen. Though you can get indications. Are you on you tod or is there someone else in the van? Can we hardwire the multimeter to the battery (Eventually you may choose a dedicated voltmeter) This is all so someone can observe what is happening.
Questions with a battery in good charge (12.70V plus) what voltage is showing across the battery when you first fire up the engine? I'm not sure what to expect as the starter battery will have a demand at this point. But if the voltage jumps to above 13.8 volts the rate of charge is better than you would get from a zig unit if on EHU. Every extra 0.1V is good right up to 14.5V especially at the start. After about 1/2 an hour or say 40 mins does the voltage drop? If so you have a thermostatically controlled alternator. What does it drop to?.
What sort of battery do you have? Wet Lead Acid Unsealed, Wet Lead Acid Sealed, Gel, Glass Mat, Other? This would affect the sort of charging you want.
A battery in full charge is generally +12.7V 50% charge 12.2V but remember 50% isn't 50% left it's the minimum charge you want in a battery as further discharge may damage future recovery. See Battery voltage and state of charge - Energy Matters Remembering what I said before about readings been affected by whether you charged or discharged the battery last.
You can gain a rough idea by looking at the wattages of the LEDs and dividing these by 12 and multiplying by the hours left on for the Amp hours used. The unknown is the heater. Propex are notionally (I've never tested one) pretty linear in their current drain Espacher Diesel heaters take a big whack of power on initial lighting Trauma? You could try to measure the current demand off the heater. Does it give an indication of the wattage of the blowers?

From your tale I've not perceived if the charging is coming from you driving down or if it's daily driving or you might have a drive 1/2 way through the 4 days?
Where did the 20Amp (Hours) usage figure come from?20 Amp hour over 4 days, per day? Truma power consumption did you get the figure from one of these pages? Truma - Trumatic E 2400 liquid gas heater
Fall back positions do you know people who you will be visiting, do frequent a local pub? Strapping chap to lift out battery and 4 or five hours on charge solves most problems.

There was a lot to be said for Trauma/Carver fires and Riviera heaters.


Sorry it's not what you need now but it can get down to practically seeing how far you can push things. Then applying practical experience, and if you can afford or want different possible solutions.
Do hang in as we may get some positive points from this by the end.

thanks for info I won't fry my meter now, my 20 amp was guess at 24 hours use running my heater at 1 amph, my van is almost new so should have up to the minute electronics I will set off with both batteries fully charged my on board charger charges both batteries the voltage to my leisure is about 14.5v after starting the engine.also have 2x12 amp agm batteries from. A mobility scooter as short term back up.my electronics are cbe pc200 with a cbe 516 mains charger. Bazz

 

[Rob H]

Leisure Battery Charging.

Hi Molly,

I'm supposing you've got a good quality 240v hookup leisure battery charger maybe Waeco or similar.

Your vehicle alternator is designed to supply 1) for a short period, a heavy charge to your vehicle batter, (probably a wet cell lead acid battery), to replace the electrical energy used in starting your vehicle, 2) it then drops down to a just a couple of amp trickle charge for your vehicle battery plus whatever electrical load your vehicle system demands at any time, heater, windscreen wipers, headlamps etc, , any heavier charge would damage your vehicle battery in the long term (overheating and excessive gassing).

Your leisure batteries could be ... wet cell lead acid, or gel lead acid or absorbed glass matt lead acid. The last two have different charging requirements (to achieve maximum battery effectiveness and life) from your vehicle battery, combined with voltage drop in wiring from your engine bay to your leisure batteries, your leisure batteries will never achieve maximum charge and consequently have a shorter useful life charged from your vehicle alternator

To cut to the chase, if pays to invest, ... to adequately charge your leisure battery / ies from your vehicle alternator suggest you research 1) Having its regulator removed and a specialised external alternator regulator fitted. I believe Sterling do one but its expensive.
2) Bond a solar panel on your vehicles roof, start at considering a 12v (really bout 18v) 100w panel or 10% of your leisure battery capacity, with a solar regulator matched to the panel output and a charge profile output matched to your leisure battery bank .... WC LA, or GEL LA or AGM LA. Look at Victron regulators and intelligent combiners.

Hope this helps.

Rob H.

 

[Tow Itch]

Sorry to be slow with this but the expert opinion bit:

Whoa, a bit heavy for a Friday night. Sorry I don't have my regs book at home any more as I now work in the office but I'll have a go.

Fuses blow simply by overheating and take time. The larger the current the less time they need. Close protection (a cartridge fuse) should blow within 4 hours at 1.5 times the rated current. Breakers typically have a thermal part for overload and a magnetic part for short circuit.

This gives a typical characteristic for fuses of various ratings.

link

Time in seconds is the vertical axis and current on the horizontal. It shows a 60A fuse will take about 1200A to blow in 0.1 seconds and about 6 seconds at 100A.

We protect cables by coordinating the protection to what the cable will withstand. A PVC cable will normally run at 70deg max conductor temperature at full load although I usually choose them not to get any where near that otherwise people start getting worried. The modern XLPE cables run at 90deg.

When a fault occurs, the current will increase and cause the cable to start heating up. PVC cable can rise to a conductor temperature of 145deg before being damaged. So we want the fuse to blow before the cable reaches 145 deg.

The impedance of the circuit (posh word for resistance) limits the fault current. We want enough fault current to blow the fuse within 0.4 seconds for sockets and 5 seconds for lights etc., (to protect people), but we want the fault current limited to below the amount the cables and switchgear and relays, contactors etc will withstand for the duration of the fault (to protect the equipment).

Circuit breakers are good for overloads (a small amount of excess current) but fuses are better for short circuits (a large amount of excess current). We can use a fuse to back up a circuit breaker so the breaker trips on overload but the fuse trips on short circuit. That way the fault withstand current of the breaker may be less than the prospective (max possible) fault current in the circuit.

This coordination is just a small part of what I have to do when designing the electrics for large buildings.

The peak current with the 2 batteries and alernator etc. depends how it is wired. Basically you will have a network with 3 sources of potential(voltage), a load and various resistances. Everthing will have some resistance, some in the alternator, some in each cable, some in the load, some in each battery etc. Ohms law can be used to determine how much will flew in each part of the circuit. Amps = volts divided by resistance(ohms)

The relay will pass charging current from the alternator to the leisure battery, and the invertor will be connected to the leisure battery. If a heavy load such as an invertor is connected to the leisure battery it will draw current from each of the alternator, vehicle battery and leisure battery.

The current from the alternator and vehicle battery will pass through the relay, the current from the leisure battery will not. If the leisure battery is flat, it will contribute very little current to the invertor, if any, and will most likely draw charging current from the alternator and vehicle battery.

So the relay will pass the current flowing to the invertor and the charging current to the leisure battery.

The more current that is drawn, the more the voltage will drop in the vehicle battery and alternator and cables (due to resistance) and this will lower the current drawn by the invertor and leisure battery charging.

If there is a fault, the current will be drawn from the alternator and both batteries. The prospective fault current of a battery wil be the voltage divded by the sum of the resistance of the cables, fault and internal resistance of the battery. The alternator will also have a fault current. *As long as each battery and the alternator are individually fused with fuses with a high rupturing current (HRC) such as cartridge fuses, they should blow before cables or equipment become damaged as long as they are all correctly coordinated by the system designer.

Well these posts are certainly in the right section of the forum **

You are right TI, a split-charge relay arrangement will allow for complete charging of the battery.

Relays are commonly used in high vibration environments so to say that they are prone to vibration faults is wrong. Obviously a poor quality one may not perform correctly, but any poor quality component may fail to fulfil its intended purpose in more extreme environments.

It is also wrong to say that a relay is 'prone' to overloading. Overloading may damage any component, and therefore the circuit design must account for likely circumstances and protect accordingly.

Navver has covered the selection and sizing of fuses comprehensively. I would only add that the issue of fuses being better than circuit breakers for short-circuit protection is even more pertinent where DC circuits are concerned. There are very few safe and reliable DC circuit breakers. Even some from well-known manufacturers should not be touched with the proverbial barge pole, so I would never use the miniature ones offered as alternatives to automotive fuses. When an AC circuit breaker interrups a short-circuit, the resultant arc tends to be extingished as the AC waveform passes through the zero point. With DC, the voltage and current are constant and it is easier for the arc to be sustained with destructive consequences.

I have some questions of my own on this but it's taking time as I really have to sit down and think to even just phrase questions.

 

[pops]

pops

While on this subject, will a solar panel trickle feed mt Leisure battery to run lights, radio, Fridge..
:dnd:

 

[n brown]

While on this subject, will a solar panel trickle feed mt Leisure battery to run lights, radio, Fridge..
:dnd:

is that a compressor fridge or 3 way ? any set up will struggle to run a 3 way fridge

 

[steco1958]

Pops, yes the Solar (depending on size) will charge your leisure/vehicle battery (depending on installation configuration) the battery will then in turn feed all your 12v appliances.

Your fridge however will rarely if ever be used on 12v unless your engine is running

 

[Harmergeddon]

started engine and checked amps going in with the sterling and it showed 24 amps going in to the battery. Does the sound right to you guys?

No this is most definately not right, assuming your system is 12 volts not a 24 volt system.
If you are on a 12 volt system and your sterling is charging your 12 volt battery at 24 volts then it is likely to have boiled it dry by now.
I would expect a sterling to be charging in very cold weather a maximum of 15.5volts.
Are you on a 12 volt system?

 

[Tezza]

No this is most definately not right, assuming your system is 12 volts not a 24 volt system.
If you are on a 12 volt system and your sterling is charging your 12 volt battery at 24 volts then it is likely to have boiled it dry by now.
I would expect a sterling to be charging in very cold weather a maximum of 15.5volts.
Are you on a 12 volt system?

Hya....not 24 volts...24 amps. I'm sure it's not working correctly . A 4 hour run last night should have meant the 220 amp battery should have been charged fully. We have had the tv on for about 3 hours same with led's and esparcher for same time. Just checked battery voltage now and it's reading 12.43

 

[Harmergeddon]

Hya....not 24 volts...24 amps.

Opps my mistake misread your post. :beer: