Leisure battery discharging whilst driving

[Gooners on Tour]

I am currently in Bulgaria on the way back from Greece. I have a 200ah KS Energy lithium leisure battery that is discharging at 15-18 amps/hr whilst driving. If I turn the fridge off the discharge stops and then I see a few amps charging via Solar. The battery charges fine when Solar or EHU. I can see all this via the KS energy app.
The engine battery is charging fine, I have checked this with a multimeter. I have found a number of fuses in the vicinity of the leisure and engine batteries and also the B2B charger - all are fine. I have checked all battery connections and continuity between the batteries - again all fine.
The B2B has some LED’s which illuminate so there is power to it but after my basic fault finding I am beginning to suspect the B2B maybe faulty?
I would appreciate some technical input and/or some further checks I can try from some Funsters who have far greater knowledge on this subject than me!

Thanking you in advance.

 

[Lenny HB]

The input side of the B2B should be the same voltage as the starter battery, the output should rise as the battery charges up to about 14.2v.

How is your B2B triggered as a lot of problems arise if they are triggered by voltage sensing, always best to have them triggered by a D+ signal.

 

[Gooners on Tour]

The input side of the B2B should be the same voltage as the starter battery, the output should rise as the battery charges up to about 14.2v.

How is your B2B triggered as a lot of problems arise if they are triggered by voltage sensing, always best to have them triggered by a D+ signal.

Thanks for the quick response Lenny.
I’ve checked the input and output voltages and the B2B seems to be working. There is also 13+ volts on the output when the engine is not running with the ignition off which I did not expect?
How the B2B is triggered is a bit beyond my knowledge but there is a plug in the D+ terminal? I’ve attached some pics that may hopefully help. It’s a 2023 Ducato based A class if that sheds any light?
Any further thoughts will be much appreciated.

 

[Lenny HB]

13v on the output is the leisure battery voltage, as that is what it is connected to. Yes looks like it's wire to the D+, output voltage should rise with the engine running.

 

[Gooners on Tour]

Ah that makes sense - Thank you.
So with the engine off the output terminal reads 13.4v. With the engine running it reads 13.0v. So would you say the B2B is faulty?

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[Lenny HB]

Ah that makes sense - Thank you.
So with the engine off the output terminal reads 13.4v. With the engine running it reads 13.0v. So would you say the B2B is faulty?

Yep, it appears to be loading the leisure battery.

Is there a yellow led flashing as the number of flashes determines the fault. Also are the dip switches set correctly for the type of battery?

 

[Gooners on Tour]

Yep, it appears to be loading the leisure battery.

Is there a yellow led flashing as the number of flashes determines the fault. Also are the dip switches set correctly for the type of battery?

Yes the dip switches are set for lithium.
No yellow LED. There is a solid red LED which according to the user manual is bulk charging but the Leisure battery is already at 100% as we have been on EHU overnight. But I guess as the fridge is drawing 15-18a that is why the B2B is bulk charging?
Really appreciate your help with this Lenny

 

[AdrianChen]

If its a 25amp B2B, is it just struggling to keep up with the fridge at times, especially if its getting hot, or cables are thin etc....

Is the fridge on 12v during the tests when you get the voltage drop to 13v? What happens if the fridge is off or on gas?

 

[LithiumConvert]

Assuming you have a gas Crash Sensor try running the fridge on gas whilst driving.

Is the leisure battery then getting a charge?

 

[Lenny HB]

Now you have said the battery is at 100% it is obvious that the fridge is the current draw, the battery won't take a charge until it's depleted quite a bit.

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[Lenny HB]

Assuming you have a gas Crash Sensor try running the fridge on gas whilst driving.

Is the leisure battery then getting a charge?

Not a good idea, against Construction & Use regulations, a fridge has a naked flame. Better just to turn it off.

 

[Gooners on Tour]

If its a 25amp B2B, is it just struggling to keep up with the fridge at times, especially if its getting hot, or cables are thin etc....

Is the fridge on 12v during the tests when you get the voltage drop to 13v? What happens if the fridge is off or on gas?

Thanks for the reply but van is less than 2 yrs old and has been fine up until now. Problem only arisen in last 7 days.
As stated in previous posts, no drop if I turn the fridge off. Works fine on gas.

 

[Gooners on Tour]

Assuming you have a gas Crash Sensor try running the fridge on gas whilst driving.

Is the leisure battery then getting a charge?

Thanks for the reply. As stated in earlier post the leisure battery does not charge whilst driving. If I turn the fridge off I get a few amps charge from Solar.
I can just turn the fridge off whilst driving as I’m only driving 3-4 hrs at a time max. Would just like to get to the bottom of this.

 

[Gooners on Tour]

Now you have said the battery is at 100% it is obvious that the fridge is the current draw, the battery won't take a charge until it's depleted quite a bit.

Thanks Lenny but if the battery doesn’t charge until depleted why is the red LED indicating bulk charge?
As stated previously the fridge is definitely the current draw as if I turn it off then I get a few amps charge from solar but nothing near what I should be getting from a 25a B2B?
Also when I set off with the battery at 100%, upon arrival after 3-4hrs driving it is down to 50ish% so definitely not charging via B2B?

 

[Lenny HB]

It goes to bulk because of the fridge running but the battery should start charging when the battery down to 90%.
As Adrian says it could be something simple like the cables are too small.
But to lose 100 amps in 3-4 hours is a lot more than the fridge would take, then again BMS readings are not known for their accuracy.

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[suavecarve]

Can you take a screenshot of your Fogstar app when the motor is running and it is in bulk charge and one when it isn't running ?

 

[Lenny HB]

Can you take a screenshot of your Fogstar app when the motor is running and it is in bulk charge and one when it isn't running ?

That would be difficult with a KS Energy battery.

 

[suavecarve]

That would be difficult with a KS Energy battery.

But not impossible !


I ll be in the idiots corner if you need me

 

[Gooners on Tour]

Can you take a screenshot of your Fogstar app when the motor is running and it is in bulk charge and one when it isn't running ?

So today I have driven for just under 4hrs and the Leisure battery has discharged by 34% or 68a. I have attached screenshots from the KS Energy app, both with engine running, one with the fridge on and one with it off. The one running shows 17a/hr discharge which is pretty much spot on with driving time x discharge amps = 4x17 = 68a.
I think I’ve now convinced myself that the B2B is faulty but I’m more than happy for you more knowledgable guys to correct me if I’m wrong?!!!

 

[Lenny HB]

Probably not much wrong with the B2B just not mounted correctly.
Looks like it is under the seat with not much airflow and you probably have the heating on. If it's a 25 amp B2B and it's getting hot it is probably reducing it's output, this is normal.

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[Gooners on Tour]

Probably not much wrong with the B2B just not mounted correctly.
Looks like it is under the seat with not much airflow and you probably have the heating on. If it's a 25 amp B2B and it's getting hot it is probably reducing it's output, this is normal.

Thanks Lenny but it’s been absolutely fine for almost 2yrs from new? The problem has only arisen in the last 7 days?

 

[Lenny HB]

Thanks Lenny but it’s been absolutely fine for almost 2yrs from new? The problem has only arisen in the last 7 days?

Got me thinking now has the fridge been running from a relay switched by the D+ and that has failed and it is now taking power from the leisure battery.
But that wouldn't explane only getting 17 amps,
Have you seen a full 25 amps into the battery in the past.

I'm typing this thinking out loud so just guess work.

My van had a 25 amp B2B and with the fridge taking 15 amps I was only getting a 10 amp charge most of the time, so I replaced it with a 50 amp B2B.

 

[AdrianChen]

Got me thinking now has the fridge been running from a relay switched by the D+ and that has failed and it is now taking power from the leisure battery.
But that wouldn't explane only getting 17 amps,
Have you seen a full 25 amps into the battery in the past.

I'm typing this thinking out loud so just guess work.

My van had a 25 amp B2B and with the fridge taking 15 amps I was only getting a 10 amp charge most of the time, so I replaced it with a 50 amp B2B.

I cleaned my computer out with a bit of compressed air the other day - Cooling fans/filter/radiator were absolutely choked with crud sucked in by a the fans - does that B2B have a fan?

 

[Gooners on Tour]

Got me thinking now has the fridge been running from a relay switched by the D+ and that has failed and it is now taking power from the leisure battery.
But that wouldn't explane only getting 17 amps,
Have you seen a full 25 amps into the battery in the past.

I'm typing this thinking out loud so just guess work.

My van had a 25 amp B2B and with the fridge taking 15 amps I was only getting a 10 amp charge most of the time, so I replaced it with a 50 amp B2B.

Cant say I’ve ever paid much attention to it in the past. I’ve just got used to arriving somewhere and the battery is at 100%. I’ve only started looking into since the battery has been discharging whilst driving.

 

[Gooners on Tour]

I cleaned my computer out with a bit of compressed air the other day - Cooling fans/filter/radiator were absolutely choked with crud sucked in by a the fans - does that B2B have a fan?

No fan on 25a model.

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[Lenny HB]

Cant say I’ve ever paid much attention to it in the past. I’ve just got used to arriving somewhere and the battery is at 100%. I’ve only started looking into since the battery has been discharging whilst driving.

Have you used it much in the cold before with cab heating on full blast and running the leisure battery down more than usual?

 

[Gooners on Tour]

Have you used it much in the cold before with cab heating on full blast and running the leisure battery down more than usual?

Last November in SE Germany/Austria -15 degs some days. Battery always 100% on arrival.

 

[AdrianChen]

Charging at 0.4 amps with the fridge off does seem low for a 25amp B2B, especialy if you still have a solid red LED indicating its in bulk, so should be above 14.6v output, which is absorb (floats at 13.8v)....

Some thoughts:
Battery BMS has charging switched off?
Battery Cells badly imbalanced or a duff cell I think KS use cylindrical types - Can you check that on the KS - App?
Loose connection/bad fuse on output from B2B - In which case it would flip pretty quickly to float (Green LED) after starting
Poor connections (inc common Earth) or bad fuse on input or output

Or a bad b2b giving you the opportunity to upgrade

 

[AdrianChen]

Last November in SE Germany/Austria -15 degs some days. Battery always 100% on arrival.

Should be OK if battery in the warm - think they cut off charging at 0°c

 

[Gooners on Tour]

Charging at 0.4 amps with the fridge off does seem low for a 25amp B2B, especialy if you still have a solid red LED indicating its in bulk, so should be above 14.6v output, which is absorb (floats at 13.8v)....

Some thoughts:
Battery BMS has charging switched off?
Battery Cells badly imbalanced or a duff cell I think KS use cylindrical types - Can you check that on the KS - App?
Loose connection/bad fuse on output from B2B - In which case it would flip pretty quickly to float (Green LED) after starting
Poor connections (inc common Earth) or bad fuse on input or output

Or a bad b2b giving you the opportunity to upgrade

Think the 0.4a charging is from Solar, very overcast here!
I’ve checked all fuses and connections.
Unable to change any settings in KS app, it’s info only. Also cells are all balanced.