Looking for a way to charge my vehicle battery

[missoo]

Hi guys,

On my self-converted RV (renault master 3), I have some issues with the engine battery. While I am parked, there is a too high consumption of the electronic equipments. Therefore, after few days opening the doors without driving, my engine battery is empty ... (I have already spend several weeks looking where this issue is coming from, according to the manufacturer, everything is normal, it is just that this renault master is not made to be a van).

As I have 430 W of solar panel with a 280 Ah LifePo4 battery, I would like to use some of my solar energy to sometimes charge the battery of my vehicle to avoid discharge.

Is there any equipment that would do that ? I mean, that would switch the charge between lithium battery and vehicle battery depending of the charge.
After some researchs, I would say that as my two batteries are made of two different technologies it could be a problem..

I am looking for the cheapest and easiest way to do that.

I hope you could help me with that !

Thanks!

 

[mikefitz]

I have some issues with the engine battery.

Have you had the battery tested or replaced? Have you with a meter checked what current is being drawn from the battery and attempted to find which circuit is causing the issue. Anything you add will still be draining power, although small, from your system.

As soon as you open the doors on a van like the Renault the various electronic modules power up expecting a start sequence. This may involve switching lamps in the cab or load area, have you checked there are no such lamp circuits left live?

I have used this simple circuit ( below) for years first with lead acid service battery now with lithium service battery. There are several low coat systems on sale under various names, guessing you are in Europe , one such system, 'Battery Master'.
The basis of all these systems is to bleed a limited one way current from the service battery to the engine battery when the service battery is under charge or high float. They can be complex or simple. My circuit , use at your own risk.

Mike

 

[missoo]

Hi and thanks for your answer,

Yes the battery has been tested before for this problem, now it has been replaced for a brand new one but the issue is still the same.

I know that my consumption is 1,7 A for 40 minutes (even with lights switch off). After 40 minutes it goes back to few mA but every time I open a door, it is 1,7 A again for 40 minutes... If I don't drive for several days it is draining my battery.

I have check each fuse, and I know which ones get a high consumption but I don't know which equipment in particular are responsible for it.
The yellow ones are the ones consumming.

I will try to translate them as I can :/ (I have got numbers associated if needed for understanding)
- Radio, multifunction screen, plug for audio and alarm :
- Central Unit/ body controller (?), indicator light and back fog lamp
- Stop light, inside lights



About the battery master, I guess it is that https://shop.motorhomefun.co.uk/product/battery-master/.
Would it be the same as this one ? https://www.cbe.it/en/csb2/

I was thinking of installing the last one, but I didn't know if it would work with lithium battery. Also, I called 3 different "solar professionnal" and they didn't know much about it.
By the way, which technology is usually used for engine batteries ? Lead ?

 

[DJSmiley]

This is a known problem with some self-converted Renault Master vans.

On many newer cars, the ECU powers a lot of equipment. After shutting down the engine and leaving the car, the ECU will enter standby mode. (Usually 15-60mins after leaving the car)
However, if you don't lock the car and frequently open the doors (which you usually don't when you're in the van) the ECU isn't going into standby, or is woken up, repeating the 15-60min process, eventually draining the starter battery.

The starter battery is a lead-acid one. If your secundary battery is also lead-acid, you can easily fix this by adding a small diode and resistor. However, since the LFP voltage is lower than the voltage a lead-acid battery is happy with (14.2V is recommended for LFP, lead-acid likes 14.6-14.8V), that's not going to work. to a certain amount it works, you might give it a try, as @mikefitz already mentions.

That CSB thing seems pretty equal, only for a higher cost (with some small additional electronics to detect voltage, but no rocket science involved)
The diode+bulb (or resistor) works just as fine.

If you really want to topup the starter battery optimal, you have some other options.
- Replace the solar charge controller with one with dual output.

Examples are eg the Votronic Duo (also sold as Alden) or the Epever Duoracer. Those have a seperate output for a second battery (Lead-acid charging profile for eg a starterbattery).
That will keep the starterbattery topped up using the proper charge profiles (whereas the HH battery can have a different chemistry / charge profile)

Another option is using a seperate charger. If you have an inverter running frequently, you might just hookup a simple charger for the starter battery, powered by the inverter and the LFP battery.
Drawbacks are the efficiency is lower, since you will have both the inverter losses and the charger losses, so overall efficiency is decreased. But with enough solar that's not going to be an issue.


Last option might be: Modify the doors. Usually, when in the van, you're primary using the side door. Front driver/passenger doors aren't used that much. If you are able to bypass the detector switch in the door, the van thinks the doors are closed, and doesn't detect opening of the door (thus waking up the ECU and draining).
Disadvantage is any lights usually triggered by the door also aren't powered on on the modified door, since the car has no sense anymore of the actual door status (It just thinks it's closed)

If you're barely using the backdoors this might be the easiest (and cheapest) workaround. Off course you also can apply this to the back doors as well if you really want. Usually, it's some kind switch which is pressed by the door, or some contacts. If you have the original lights (triggered by the doors) its easy to figure out what does trigger this.

 

[missoo]

Thank you so much for your explanations.
Too bad I chose a Renault !...

What are the issues if I charge my lead-acid battery with my LFP ? It means that the LFP will never be able to fully charge the lead-acid battery as the LFP voltage is lower ?
Can it damaged my lead-acid battery ?

Ok for the CBE. I can try the diode + bulb option. Is it "hard" to do ? Are there any risks associated? (I have build my LFP battery... but electricity do scares me !!).

Is this system charging my engine battery only when the secundary battery is fully charged or all the time ?

I have also thought of replacing my MPPT with a dual output but my Epever is brand new and it breaks my heart to replace it already :/ Also I have check and it seems the MT50 doesn't go on the duoracer...

I am not sure I want to use my inverter with a charger... It seems less convenient.

I am also thinking of installing a small solar panel (50W) with a dedicated PWM of 5A ...

Not excited about it either.

I don't know what is the best solution here... I don't understand why the latest Renault are the only campervans suffering from this problem !
What is wrong with french people ???

 

[circus]

Usually a dc to dc battery charger charges the house battery with you car. I don't see why it wouldn't charge your car with the house battery if wired correctly. They're mainly used to limit current.

What are the issues if I charge my lead-acid battery with my LFP ? It means that the LFP will never be able to fully charge the lead-acid battery as the LFP voltage is lower ?
Can it damaged my lead-acid battery ?

Probably not, it's a matter of limiting current in the wire.

 

[mikefitz]

Also, I called 3 different "solar professionnal" and they didn't know much about it.
By the way, which technology is usually used for engine batteries ? Lead ?

Lead acid is almost universally used for starter batteries due to the low cost and the ability to deliver high amps or the starter typically 500 amps.

The 'professionals' over the years have caused much me much grief, there are very few out there that are OK.

battery master, https://www.roadpro.co.uk/product/02e02-battery-maintainers/votronic-battery-master-c8451/C8451

They don't differ much from my circuit, this is what you get from Votronics,


You may notice my circuit uses a low volt drop diode, this gives adequate performance with a lithium service battery and a LA starter. The circuit use will cost only a few £.

Consult the vehicle handbook before considering using any type of battery charger on the engine battery with it still connected to the van circuits, many manufactures only advise charging with the battery disconnected.

Mike

 

[mikefitz]

What are the issues if I charge my lead-acid battery with my LFP ? It means that the LFP will never be able to fully charge the lead-acid battery as the LFP voltage is lower ?
Can it damaged my lead-acid battery ?

for a maintain duty the objective is not to charge the engine battery, that will be carries out by the alternator, but to keep up with the power lost to the van electronics. The engine battery will not be damaged by connecting to the lithium.
You could connect the two batteries with a suitable cable, fused at each battery, and charge the batteries in parallel as short term measure. (only when parked)

Is this system charging my engine battery only when the secondary battery is fully charged or all the time ?

With my bulb diode circuit there will be a small current almost all the time if the engine battery is slightly discharged. When the Lithium is under charge the current will increase, (if the engine battery need more charge). But its not a charger, it will only make up for the losses. It wont help a discharged engine battery.

why the latest Renault are the only campervans suffering from this problem

My van has a similar problem but not as significant as yours. Are you sure there is not an issue with say the radio staying in an active state for the long period or lighting being on ( I know of one van conversion where a interior light was panelled over ). I see from the tests that the lighting circuit is taking power, try turning them off. Getting back to the radio, there is often a programmable period for the radio to be active before it powers down, check this.

Depending how van body computer detects 'door open' it may be possible to disable one or more of the doors. If its a simple 'plunger switch' in the door frame you could tape it in the 'shut' position.

Mike

 

[time2roll]

This works on many RVs including mine.

Trik-L-Start

 

[missoo]

You may notice my circuit uses a low volt drop diode, this gives adequate performance with a lithium service battery and a LA starter. The circuit use will cost only a few £.

Do you have any picture of your circuit ?
Have you welded the components on a board as we can see on the Votronic battery master ?

Consult the vehicle handbook before considering using any type of battery charger on the engine battery with it still connected to the van circuits, many manufactures only advise charging with the battery disconnected.

Does "battery charger" include battery master ?
My van circuits are totally indepand from my engine battery. Does it mean it's safe?
Also I have charged my engine battery many times without disconnecting it...

But its not a charger, it will only make up for the losses. It wont help a discharged engine battery.

Allright. I guess it's exactly what I need, to maintain charge.

Are you sure there is not an issue with say the radio staying in an active state for the long period or lighting being on ( I know of one van conversion where a interior light was panelled over ). I see from the tests that the lighting circuit is taking power, try turning them off. Getting back to the radio, there is often a programmable period for the radio to be active before it powers down, check this.

The radio is always off. I had two lights in the back of my van, but I removed them.
In the front, I also have two lights, but I tested the current with lights on it rises to 2,3 A. If I removed the light bulbs, it goes back to 1,7A.
I will check if I can program something on my radio....

Depending how van body computer detects 'door open' it may be possible to disable one or more of the doors. If its a simple 'plunger switch' in the door frame you could tape it in the 'shut' position.

I am not sure it's that easy on my RV but it's not a long-lasting solution.

 

[missoo]

Last option might be: Modify the doors. Usually, when in the van, you're primary using the side door. Front driver/passenger doors aren't used that much. If you are able to bypass the detector switch in the door, the van thinks the doors are closed, and doesn't detect opening of the door (thus waking up the ECU and draining).
Disadvantage is any lights usually triggered by the door also aren't powered on on the modified door, since the car has no sense anymore of the actual door status (It just thinks it's closed)

If you're barely using the backdoors this might be the easiest (and cheapest) workaround. Off course you also can apply this to the back doors as well if you really want. Usually, it's some kind switch which is pressed by the door, or some contacts. If you have the original lights (triggered by the doors) its easy to figure out what does trigger this.

@DJSmiley It doesn't bother me if lights aren't powered anymore as I don't have lights in the back of my van.
However, what happens if I doesn't close perfectly the side door (which happens often) and that I lock my RV?
Is the vehicle going to "think" that it's really closed as the detector is bypassed ?
What would happen is that I could get robbed if I get distracted...

I believe the diode + bulb is a good (and cheap) option but I am not sure of how to do it yet.


Last question, is there a way to monitor the engine battery capacity ? I would appreciate having a screen telling me when it gets low ....

 

[missoo]

Hi guys,

I have just read that the "battery master" (if they are similar to the french "répartiteur de charge") could totally drain the secundary battery.

It would be because when it's a lithium technology the voltage is not dropping sufficiently during the discharge to stop the battery master.
(I am not sure I understood correctly everything).

Is it right ? What can we do about that ?