Starting the engine from the leisure battery.

[Amarillo]

I have just made a 5 metre extension lead so that our fridge can be powered in the driveaway awning.

It got me wondering... If I managed to flatten the engine battery, could I safely get the engine restarted using the leisure battery with the leads and connectors I have.

The extension lead is Anderson to Anderson with 6mm2 cable.

I have a ring terminal to Anderson lead with a 50 amp fuse, connected directly to the leisure battery.

In daylight, the leisure battery is being continuously charged from solar panels with up to 15 amps.

Being totally non technical, what I think might work is:
1. Remove one Anderson connector from the long extension lead.
2. Tape the positive lead contact to the positive battery terminal.
3. Tape the negative lead contact to the engine block.
4. Plug the extension lead Anderson connector into the leisure battery's Anderson connector.
5. Leave in sunshine all day.
6. Disconnect all leads and try to start the vehicle.

What I am unsure about:
1. Is 6mm2 cable sufficient to recharge a flat battery from a fully charged battery of the same type?
2. Is a 50 amp fuse OK?
3. If recharging a flat battery from a charged battery, without drawing current, would it be better to connect the two negative battery terminals?

Have I missed anything else? Would there be a better way to do things?

 

[MattBW]

If the battery has a cranking rating then you may be able to, worth checking first though. I guess the battery would charge the engine battery if connected up.

 

[ArunAlec]

Didn’t you fry the last battery with that 12v kettle?
Don’t do it!️️

 

[Loz]

If one is fully charged and the other fully flat then the current inrush might be higher than 50A also you will get a volts drop over the 6mm cable if its too long, (you don't say how long your extension is?)

 

[B J G]

I've seen it done with a car (big Volvo) and caravan leisure battery with no problems.

personally I'd just connect the 2 batteries for 10-15mins to let the engine battery take some power from the leisure battery and then try the engine normal start without the leisure battery connected. On an emergency situation.

 

[WelshGas]

I have just made a 5 metre extension lead so that our fridge can be powered in the driveaway awning.

It got me wondering... If I managed to flatten the engine battery, could I safely get the engine restarted using the leisure battery with the leads and connectors I have.

The extension lead is Anderson to Anderson with 6mm2 cable.

I have a ring terminal to Anderson lead with a 50 amp fuse, connected directly to the leisure battery.

In daylight, the leisure battery is being continuously charged from solar panels with up to 15 amps.

Being totally non technical, what I think might work is:
1. Remove one Anderson connector from the long extension lead.
2. Tape the positive lead contact to the positive battery terminal.
3. Tape the negative lead contact to the engine block.
4. Plug the extension lead Anderson connector into the leisure battery's Anderson connector.
5. Leave in sunshine all day.
6. Disconnect all leads and try to start the vehicle.

What I am unsure about:
1. Is 6mm2 cable sufficient to recharge a flat battery from a fully charged battery of the same type?
2. Is a 50 amp fuse OK?
3. If recharging a flat battery from a charged battery, without drawing current, would it be better to connect the two negative battery terminals?

Have I missed anything else? Would there be a better way to do things?

Yes you can, but some provisos.
1. Do not try to start Engine with the 2 Batteries connected.
2. The Engine Battery is unlikely to be totally flat.
3. Basically you are putting 2 Batteries in parallel, but they will have dissimilar voltages. 4. Not something to do on a regular basis but as an emergency only.
5. Don’t tape the connectors it might have a high resistance. Either wire the appropriate Anderson connector permenantly to the Engine Battery or make up a lead like this.

 

[Amarillo]

Didn’t you fry the last battery with that 12v kettle?
Don’t do it!️️

No. It seems I did little or no harm at all to the leisure battery by using a 12 volt kettle. It appears that the solar charger is just an incredibly unreliable way to monitor the state of the battery.

 

[briwy]

Probably a better solution is a LiPo jump start battery. fairly inexpensive now, can be stored near the battery under the bonnet and has USB, torch and 12v outputs as well so useful for other things as well.
Of course you have to remember to keep it charged up but it negates the risk of damaging the leisure battery.

 

[kp64zl]

How about just getting a pair of jump leads? Usually someone around to help. Simpler.

 

[18hunts]

My understanding is they are different types of battery. The main battery is designed to give a high current for a short period to start the engine. The leisure battery is designed for slow discharge at a constant rate with no huge peaks in demand like a starter motor. It has the potential to reduce the life of the battery.

 

[18hunts]

I quote
"
9. WHAT IS THE DIFFERENCE BETWEEN A CAR BATTERY AND A LEISURE BATTERY?
A car’s battery is designed to provide a very large amount of current for a short period of time – known as micro-cycling (except for stop/start vehicles). This surge of current is needed to turn the engine over during starting. Once the engine starts, the alternator provides all the power that the car needs. Used in this way a car battery can last a number of years. To provide a large amount of starting, a car battery uses thin plates in order to increase the plate surface area.
A leisure battery is designed to provide a steady amount of current over a long period of time. It can provide a surge when needed but less than a car battery can. Leisure batteries are also designed to be discharged over and over again (something that would ruin a car battery very quickly). To accomplish this leisure batteries sometimes use thicker plates and glass mat separators are added to increase the life of the positive plates.
The purpose of a leisure battery is to provide power for trolling motors, uninterrupted power supplies (UPS) and other accessories for marine, recreational vehicle (RV), commercial and stationary applications."

 

[Amarillo]

I quote
"
9. WHAT IS THE DIFFERENCE BETWEEN A CAR BATTERY AND A LEISURE BATTERY?
A car’s battery is designed to provide a very large amount of current for a short period of time – known as micro-cycling (except for stop/start vehicles). This surge of current is needed to turn the engine over during starting. Once the engine starts, the alternator provides all the power that the car needs. Used in this way a car battery can last a number of years. To provide a large amount of starting, a car battery uses thin plates in order to increase the plate surface area.
A leisure battery is designed to provide a steady amount of current over a long period of time. It can provide a surge when needed but less than a car battery can. Leisure batteries are also designed to be discharged over and over again (something that would ruin a car battery very quickly). To accomplish this leisure batteries sometimes use thicker plates and glass mat separators are added to increase the life of the positive plates.
The purpose of a leisure battery is to provide power for trolling motors, uninterrupted power supplies (UPS) and other accessories for marine, recreational vehicle (RV), commercial and stationary applications."

I’ve checked. Both my engine and starter battery are the same Varta AGM battery.

Edit
Both my engine and /leisure/ battery are the same Varta AGM battery.

 

[WelshGas]

My understanding is they are different types of battery. The main battery is designed to give a high current for a short period to start the engine. The leisure battery is designed for slow discharge at a constant rate with no huge peaks in demand like a starter motor. It has the potential to reduce the life of the battery.

But he wasn't planning on using the Leisure Battery to start the engine but just to increase the charge level of the Engine Battery so that it can start the engine on its own.

 

[WelshGas]

I quote
"
9. WHAT IS THE DIFFERENCE BETWEEN A CAR BATTERY AND A LEISURE BATTERY?
A car’s battery is designed to provide a very large amount of current for a short period of time – known as micro-cycling (except for stop/start vehicles). This surge of current is needed to turn the engine over during starting. Once the engine starts, the alternator provides all the power that the car needs. Used in this way a car battery can last a number of years. To provide a large amount of starting, a car battery uses thin plates in order to increase the plate surface area.
A leisure battery is designed to provide a steady amount of current over a long period of time. It can provide a surge when needed but less than a car battery can. Leisure batteries are also designed to be discharged over and over again (something that would ruin a car battery very quickly). To accomplish this leisure batteries sometimes use thicker plates and glass mat separators are added to increase the life of the positive plates.
The purpose of a leisure battery is to provide power for trolling motors, uninterrupted power supplies (UPS) and other accessories for marine, recreational vehicle (RV), commercial and stationary applications."

This is an outdated explanation. Many vehicless, California included, now have Stop/Start, Rejenerative Braking and Smart Alternators. These vehicles use specialised batteries, in fact often AGM which are just relabeled Leisure Batteries and sometimes not even relabeled.

 

[TripleBee]

This is an outdated explanation. Many vehicless, California included, now have Stop/Start, Rejenerative Braking and Smart Alternators. These vehicles use specialised batteries, in fact often AGM which are just relabeled Leisure Batteries and sometimes not even relabeled.

The leisures batteries are batteries used as starter batteries in other cars with Start/Stop function (AGM).
It is just the name that is different. The name follows the intention of use.
I don't have start/stop on my California (not BMT, luckily), and the 2 leisure batteries are worth 3x my starter battery.

 

[MattBW]

If one is fully charged and the other fully flat then the current inrush might be higher than 50A also you will get a volts drop over the 6mm cable if its too long, (you don't say how long your extension is?)

Sounds like if you wanted to do it, may be safer to do so through some sort of charge controller otherwise proper jump cables or take the battery out?

 

[Amarillo]

Sounds like if you wanted to do it, may be safer to do so through some sort of charge controller otherwise proper jump cables or take the battery out?

I was thinking that it would be safer to connect the starter battery to the solar panels and just leave in sunshine for a few hours.

 

[AlanC]

But he wasn't planning on using the Leisure Battery to start the engine but just to increase the charge level of the Engine Battery so that it can start the engine on its own.

Starting the engine with the leisure battery is just what Tom is wanting to do, i.e. jump start the engine with the leisure battery as you would do with another car.

Alan

 

[Amarillo]

Starting the engine with the leisure battery is just what Tom is wanting to do, i.e. jump start the engine with the leisure battery as you would do with another car.

No. The way I was considering starting the engine with a flat starter battery was to connect the leisure and starter batteries in parallel, let the charge in both equalise, disconnect the leisure battery and try to start the engine.

The leads I have are nowhere near up to the job of cranking the engine.

 

[AlanC]

No. The way I was considering starting the engine with a flat starter battery was to connect the leisure and starter batteries in parallel, let the charge in both equalise, disconnect the leisure battery and try to start the engine.

The leads I have are nowhere near up to the job of cranking the engine.

Ah sorry, I misunderstood your first post.

Alan

 

[jepotherepo]

Why not give up with jump leads or trying to connect you battery and pop one of these under your flexiboard for emergencies https://www.amazon.co.uk/dp/B01I3IIQWY/?tag=unique09f-21

 

[R_Sargeant_CH]

I have just made a 5 metre extension lead so that our fridge can be powered in the driveaway awning.

It got me wondering... If I managed to flatten the engine battery, could I safely get the engine restarted using the leisure battery with the leads and connectors I have.

The extension lead is Anderson to Anderson with 6mm2 cable.

I have a ring terminal to Anderson lead with a 50 amp fuse, connected directly to the leisure battery.

In daylight, the leisure battery is being continuously charged from solar panels with up to 15 amps.

Being totally non technical, what I think might work is:
1. Remove one Anderson connector from the long extension lead.
2. Tape the positive lead contact to the positive battery terminal.
3. Tape the negative lead contact to the engine block.
4. Plug the extension lead Anderson connector into the leisure battery's Anderson connector.
5. Leave in sunshine all day.
6. Disconnect all leads and try to start the vehicle.

What I am unsure about:
1. Is 6mm2 cable sufficient to recharge a flat battery from a fully charged battery of the same type?
2. Is a 50 amp fuse OK?
3. If recharging a flat battery from a charged battery, without drawing current, would it be better to connect the two negative battery terminals?

Have I missed anything else? Would there be a better way to do things?

With a horrible old Yank V8 Motor Home That I owned many years back, there was what appeared to be an ordinary 12v starter relay linking the leisure and engine batteries, activated with a simple push button marked “Battery boost”. Seemed to me to be the same functionally as using jump leads. Very cheap to implement.

 

[Christine Kirk]

Two types of battery, leisure and starter, don't put a high load onto the leisure battery it isn't designed to take it!
Our experience with various machines is that the ones that are used on a regular basis don't have starting issues; our T4 Caravelle is now 20years old and at 270K + miles is only on it's second battery, whilst our MG TF is on it's third battery at 12years old and 36K miles. Starting a machine with a flat battery needs jump leads and a starter battery; our Kubota digger can need a bit of a battery help to start if it's been stood for months, however perhaps the alternator needs attention so the battery isn't getting a full charge.
So advice is, don't try to use the leisure for anything other than what they are fitted for .
If the charging system is working correctly driving the vehicle regularly will give reliable starting, if it doesn't have the battery checked and replace with the correct one. (check the charge rate)
Buy a high quality battery like YUSSA or Bosch as our experience is that they are a better product, and give a better life.
If you aren't using the VW much hook up a battery conditioner such as a "Cetek".

 

[WelshGas]

Two types of battery, leisure and starter, don't put a high load onto the leisure battery it isn't designed to take it!
Our experience with various machines is that the ones that are used on a regular basis don't have starting issues; our T4 Caravelle is now 20years old and at 270K + miles is only on it's second battery, whilst our MG TF is on it's third battery at 12years old and 36K miles. Starting a machine with a flat battery needs jump leads and a starter battery; our Kubota digger can need a bit of a battery help to start if it's been stood for months, however perhaps the alternator needs attention so the battery isn't getting a full charge.
So advice is, don't try to use the leisure for anything other than what they are fitted for .
If the charging system is working correctly driving the vehicle regularly will give reliable starting, if it doesn't have the battery checked and replace with the correct one. (check the charge rate)
Buy a high quality battery like YUSSA or Bosch as our experience is that they are a better product, and give a better life.
If you aren't using the VW much hook up a battery conditioner such as a "Cetek".

Interesting what you say about Leisure and Engine batteries. The VW battery replacements for both types of batteries are the Varta LA80 for Leisure use and Varta F21 for Starter. Both are AGM and both have the exact same Specifications according to Varta and the LA80 are described as Dual Use. Sold at differing prices and different Warranty periods.

 

[yossarian]

Two types of battery, leisure and starter, don't put a high load onto the leisure battery it isn't designed to take it!

Accurate but in the 'olden days.'

Starter batteries were typically characterized by 'sponge lead' plates and optimized for starter loads. Using as a deep cycle would destroy them in short order.

Deep cycle batteries would often have plates built on something like a calcium grid. Reduced surface area meant unsuitability as a starter battery.

Anyway today we have to deal with start stop systems etc and AGM construction seems to be flavour of the day for both applications. Carbon infused plates were touted for modern deep cycle batteries but I've not seen any in the wild yet.

I'd be surprised if the F21 and LA80 differed by more than a sticker.