Damage to starter battery when charging leisure battery from mains

[Scottiec33]

Hi all, I have a Durite VSR on a T5.1. It's not start/stop.
The starter battery recently failed, despite Halfords testing and saying it was okay.
The leisure battery is an AGM xtreme.
I have a mains battery charger that is kept separate to the system for our cars and is AGM compatible.
People say to just connect the charger to one battery or the other and it'll be fine. However, if I connect to either battery then the relay opens and you have two uneven batteries?
I've noticed that the leisure battery needs a top up so how should I charge it to avoid damage to either battery but also make sure I get a full charge into the AGM leisure battery?
The leisure battery is under the driver's seat and so I need to remove the seat to get access.

 

[roadtripper]

Do you have different battery types between the main starter battery and the leisure battery?

 

[Lubrown]

Hi all, I have a Durite VSR on a T5.1. It's not start/stop.
The starter battery recently failed, despite Halfords testing and saying it was okay.
The leisure battery is an AGM xtreme.
I have a mains battery charger that is kept separate to the system for our cars and is AGM compatible.
People say to just connect the charger to one battery or the other and it'll be fine. However, if I connect to either battery then the relay opens and you have two uneven batteries?
I've noticed that the leisure battery needs a top up so how should I charge it to avoid damage to either battery but also make sure I get a full charge into the AGM leisure battery?
The leisure battery is under the driver's seat and so I need to remove the seat to get access.

When the cheapo split relay in our t5.1 packed in I replaced it with another split relay but added a circuit breaker either side. These act as a fuse but I figured by pressing the ‘test’ button could break the circuit manually to suit. The 240v inlet and fuse board can then charge the leisure battery only if needed.

I did this not as I was worried about charging two batteries with a relay in between (maybe I should be? No idea!) but to allow us to fully focus on keeping the fridge going like the clappers or charging a low starter battery if something had gone wrong.

Not saying this is good practice as I’m no electrician… plus I’ve never actually used it the way I intended! Both batteries seem finecwhether I use the onboard 240 panel or just solar hooked up to the leisure battery by crocodile clips.

Have the feeling I’m about to learn something

 

[Scottiec33]

Do you have different battery types between the main starter battery and the leisure battery?

Yes. Starter is normal lead acid and leisure battery is Agm and requires higher voltage to fully charge.

 

[Lubrown]

Meant to add a link to the type of circuit breaker I used. Something like this…

80A Circuit Breaker Fuse Reset 12-48V DC Waterproof For Boat Marine RV Caravan 769894711477 | eBay

I have batteries of the same type though.

 

[Scottiec33]

When the cheapo split relay in our t5.1 packed in I replaced it with another split relay but added a circuit breaker either side. These act as a fuse but I figured by pressing the ‘test’ button could break the circuit manually to suit. The 240v inlet and fuse board can then charge the leisure battery only if needed.

I did this not as I was worried about charging two batteries with a relay in between (maybe I should be? No idea!) but to allow us to fully focus on keeping the fridge going like the clappers or charging a low starter battery if something had gone wrong.

Not saying this is good practice as I’m no electrician… plus I’ve never actually used it the way I intended! Both batteries seem finecwhether I use the onboard 240 panel or just solar hooked up to the leisure battery by crocodile clips.

Have the feeling I’m about to learn something

Thank you for the reply. Yes I did think perhaps I need a circuit breaker so I can control which battery I charge. See what comments follow!

 

[roadtripper]

Yes. Starter is normal lead acid and leisure battery is Agm and requires higher voltage to fully charge.

Using a VSR to link two batteries with different charging profiles isn't ideal, have you considered using a DC-DC charger instead?

As well as being kinder to both batteries it should solve the issue of them connecting when you don't want them to.

 

[Lubrown]

Thank you for the reply. Yes I did think perhaps I need a circuit breaker so I can control which battery I charge. See what comments follow!

I just had a check on the instructions for the VSR I fitted and it doesn’t mention anything about the batteries being different types. Personally I’d think if it was important they would say don’t connect batteries if different types?
They’re here for general interest…
https://www.12voltplanet.co.uk/user/downloads/Manual-Cyrix-ct-120-EN-NL-FR-ES.pdf

 

[Scottiec33]

Using a VSR to link two batteries with different charging profiles isn't ideal, have you considered using a DC-DC charger instead?

As well as being kinder to both batteries it should solve the issue of them connecting when you don't want them to.

Thank you. You're dead right and I have. I'm just limited on money at the moment and where I can spend on the van. It's on the list for the future.

 

[Scottiec33]

I just had a check on the instructions for the VSR I fitted and it doesn’t mention anything about the batteries being different types. Personally I’d think if it was important they would say don’t connect batteries if different types?
They’re here for general interest…
https://www.12voltplanet.co.uk/user/downloads/Manual-Cyrix-ct-120-EN-NL-FR-ES.pdf

Thanks I'll have a read

 

[roadtripper]

I just had a check on the instructions for the VSR I fitted and it doesn’t mention anything about the batteries being different types. Personally I’d think if it was important they would say don’t connect batteries if different types?
They’re here for general interest…
https://www.12voltplanet.co.uk/user/downloads/Manual-Cyrix-ct-120-EN-NL-FR-ES.pdf

I'm surprised they don't because generally the minimum charge voltage of an AGM battery is above the maximum charge voltage of a standard wet lead acid.

So if you connect two of those together it's likely the higher voltage AGM battery will try and over charge the lower voltage wet lead acid.

While they are connected a charger designed for wet lead acid will under charge the AGM, but worse a charger designed for AGM will over charge the wet lead acid.

 

[Scottiec33]

I'm surprised they don't because generally the minimum charge voltage of an AGM battery is above the maximum charge voltage of a standard wet lead acid.

So if you connect two of those together it's likely the higher voltage AGM battery will try and over charge the lower voltage wet lead acid.

While they are connected a charger designed for wet lead acid will under charge the AGM, but worse a charger designed for AGM will over charge the wet lead acid.

That's exactly what I was thinking and why I reckon my starter battery ultimately failed. I don't want to shell out again. I guess I'll just disconnect the VSR and charge the leisure battery directly by removing the drivers seat and leads etc.

 

[Salty Spuds]

Hi all, I have a Durite VSR on a T5.1. It's not start/stop.
The starter battery recently failed, despite Halfords testing and saying it was okay.
The leisure battery is an AGM xtreme.
I have a mains battery charger that is kept separate to the system for our cars and is AGM compatible.
People say to just connect the charger to one battery or the other and it'll be fine. However, if I connect to either battery then the relay opens and you have two uneven batteries?
I've noticed that the leisure battery needs a top up so how should I charge it to avoid damage to either battery but also make sure I get a full charge into the AGM leisure battery?
The leisure battery is under the driver's seat and so I need to remove the seat to get access.

Hi all, I have a Durite VSR on a T5.1. It's not start/stop.
The starter battery recently failed, despite Halfords testing and saying it was okay.
The leisure battery is an AGM xtreme.
I have a mains battery charger that is kept separate to the system for our cars and is AGM compatible.
People say to just connect the charger to one battery or the other and it'll be fine. However, if I connect to either battery then the relay opens and you have two uneven batteries?
I've noticed that the leisure battery needs a top up so how should I charge it to avoid damage to either battery but also make sure I get a full charge into the AGM leisure battery?
The leisure battery is under the driver's seat and so I need to remove the seat to get access.

Connect the charger to the leisure battery & leave the VSR to do its stuff. The VSR will open when the engine is off & only close when the starter battery is close to fully charged. It will then close & start charging the leisure battery, if it needs it.

 

[roadtripper]

Connect the charger to the leisure battery & leave the VSR to do its stuff. The VSR will open when the engine is off & only close when the starter battery is close to fully charged. It will then close & start charging the leisure battery, if it needs it.

That would be true for the older one way VSR, but both of the ones mentioned in this thread are dual direction so will also close when the leisure battery is charged from the mains.

That would be fine with a conventional wet leisure battery as they have the same fundamental chemistry and charge profile as the starter, it's a problem when the leisure battery is AGM and charged to an AGM profile.

 

[Dellmassive]

Yes. Starter is normal lead acid and leisure battery is Agm and requires higher voltage to fully charge.

This is a problem and not advised.

AGM battery's will always have a higher voltage.

So the batteries will never balance.

The best thing to do is replace the starter battery with a AGM one..... As close to the size as the other.

Then the engine charge will be more balanced.

You can then also connect your mains charger to the starter battery.... Which will start to charger, then kick in the vsr. And charge the LB.

The mains charger will take twice as long to charge... Depending on the size of the charger.... You will be looking at 48hrs plus for a full charge.

 

[Scottiec33]

This is a problem and not advised.

AGM battery's will always have a higher voltage.

So the batteries will never balance.

The best thing to do is replace the starter battery with a AGM one..... As close to the size as the other.

Then the engine charge will be more balanced.

You can then also connect your mains charger to the starter battery.... Which will start to charger, then kick in the vsr. And charge the LB.

The mains charger will take twice as long to charge... Depending on the size of the charger.... You will be looking at 48hrs plus for a full charge.

Thank you and accept this isn't advised. Can you clarify the following though.... So if I connect the AGM rated mains charger to the starter battery, the VSR will open. But does the charger then ultimately subject the starter battery to a voltage that is too high and/or for too long (because of the leisure battery) and therefore damage the starter battery?

 

[roadtripper]

Perhaps what's not clear here is why do you need to regularly connect an auxiliary charger?

If you have a VSR then the engine will be charging the starter correctly and the AGM will be at least reasonably charged.

Is it because you spend some time on EHU or the van is parked up and you need to maintain the charge?

 

[Scottiec33]

Perhaps what's not clear here is why do you need to regularly connect an auxiliary charger?

If you have a VSR then the engine will be charging the starter correctly and the AGM will be at least reasonably charged.

Is it because you spend some time on EHU or the van is parked up and you need to maintain the charge?

We typically use it for 2-3 nights away without hookup but with some driving sorting the three days. Main draw is the compressor fridge.
The vans been in constant use and AGM battery quite new. There's been no draw recently but voltage on the AGM only showing about 12.62 and should be close to 13v for full capacity.
That's why I want to top it up. I'll have to go for a B2B charger soon but having read articles it may be that ventilation requirements prevent me placing up under the drivers seat and then I'd have to add extra wiring and routing if that was the case.
Many thanks all for help.

 

[roadtripper]

Have a look at @Dellmassive extensive threads on chargers, many people get them under the seat bases. While I think they work better with getting a charge signal wire through from the van electrics some are able to detect charging in the same way a VSR does, so you may be able to change over with minimal disruption.

In the meantime I'd charge everything to a normal lead acid profile, your AGM won't go to max capacity but there will be lower risk to your new starter battery.

 

[Scottiec33]

Have a look at @Dellmassive extensive threads on chargers, many people get them under the seat bases. While I think they work better with getting a charge signal wire through from the van electrics some are able to detect charging in the same way a VSR does, so you may be able to change over with minimal disruption.

In the meantime I'd charge everything to a normal lead acid profile, your AGM won't go to max capacity but there will be lower risk to your new starter battery.

Many thanks. Will do.