Buy all your Marco Polo Accessories at the Club Shop Visit Shop


Electrical questions........ 123

Samebutdifferent

Active Member
Does anyone know where the green wires from the charger go, possibly starter battery live??

What is the black box in the charger compartment. Something to do with the seat electrics??

Does the MP have a B2B charger?? i watched the alternator output to the leisure battery whilst driving, it fluctuates between approx 13.4v - 14.4v and then spikes to 14.7v-14.9v when storing kinetic energy. I don't think this would happen if a B2B was fitted.
 

Samebutdifferent

Active Member
@SteveR I'm not an expert on the technology but as I understand it Smart alternators are controlled by the vehicles ECU, reducing voltage when not required and boosting when braking/coasting so harnessing kinetic energy thus reducing fuel consumption. The starter battery must always have spare capacity to allow room for this so is only ever charged to 80%

Voltage sensing relays (VSR) were commonly used in split charge systems, sensing the voltage output of the alternator and charging the leisure battery when the engine is running. With a smart alternator varying the voltage the auxiliary battery would have times when it wouldn't be charging, even though the engine is running.

Battery to Battery or DC to Dc chargers replace VSR's taking the fluctuating voltage from the Smart alternators and reduce or boost it to maintain a stable voltage. They can be set to a particular multi stage charge profile so a variety of batteries types can be efficiently and quickly charged.

I'm contemplating replacing the AGM leisure battery with a Lithium and It's frustrating that there are no wiring diagrams for the MP, and that the batteries and other components are very inaccessible. I've found a 3rd stop start battery under the drivers seat, not sure how that fits into the equation.
 

Epigram

Active Member
:D:D

Well, I have loads of spare time so do a lot of searching, (too much) read a lot, and fall down loads of rabbit holes in the process.
Keep us posted on your exploring rabbit holes especially if you come across a wiring diagram - my unternet searches have failed so far. Trying to do electrical work on an MP is akin to working out what an elephant is putting in its mouth by looking at the tail.
 

Grand Tourismo

Active Member
Keep us posted on your exploring rabbit holes especially if you come across a wiring diagram - my unternet searches have failed so far. Trying to do electrical work on an MP is akin to working out what an elephant is putting in its mouth by looking at the tail.
That's an easy one....banana's and cream buns. :D
 

Method7

Active Member
I've found a 3rd stop start battery under the drivers seat, not sure how that fits into the equation.
SBD I’m not sure if I misread this.. as far as I am aware the MP has 2 batteries 1 under each seat, I think the leisure battery is under the passenger seat RHD models...

I have a lithium battery on my motorbike, it’s a 1996 model and just did a straight swap for the lead acid. I’ve had no problems with it. It’s a fraction of the weight and smaller than the original..

Surely all this management is for the likes of Tesla and fast charging banks of lithium ?
 
  • Like
Reactions: Ian

Samebutdifferent

Active Member
SBD I’m not sure if I misread this.. as far as I am aware the MP has 2 batteries 1 under each seat, I think the leisure battery is under the passenger seat RHD models...

I have a lithium battery on my motorbike, it’s a 1996 model and just did a straight swap for the lead acid. I’ve had no problems with it. It’s a fraction of the weight and smaller than the original..

Surely all this management is for the likes of Tesla and fast charging banks of lithium ?

There is a third stop/start battery under the drivers seat behind the starter battery box, it's accessed by removing the plastic trim;

Stop:start.jpg

Yep lithium is the way to go, same physical size, much lighter, twice the capacity, can be charged quicker and more fully from an alternator. (with the right charging system) For my use it would mean off grid power 12 months of the year without an ugly solar panel on the roof.

Your bike has a standard alternator not a smart one, it hasn't regenerative breaking and it doesn't have a leisure battery that needs charging when the engine is running and disconnected from the starter battery when stopped.

All lithium batteries have a built in battery management system, it's for safety, your sitting on it after all, performance and longevity, it keeps all the cells equalised and prevents charging at -0c temps.

Because of the BMS some manufactures claim their leisure batteries are drop in replacements, in some cases they probably are, but I'd question that on an MP especially as there is so much info missing regarding the electrics. This is an interesting video by Vicron Energy How not to blow up your alternator

For reference the leisure/starter batteries are accessed by pulling the side panel/pocket off the driver/passenger seat.
This is the leisure Battery, the starter is similar.

Leisure battery.jpg
 

Method7

Active Member
Ha I’ve not managed to get that cover off from behind the drivers seat.. it was really tight and I gave up because I didn’t want to damage it. All these batteries just seem to be offsetting the environmental impact of just driving with non stop start. Thanks for the photo I wondered what was in there, I understand your caution regarding the battery change.
 

Samebutdifferent

Active Member
I pulled the leisure battery out and found the answer to question 3. Right at the rear of the battery compartment is what I believe is a split charge relay, showing a positive connection from each battery. No B2B charger.

Relay.jpg


Can't see how you gain access to work on the components in the battery box other than from where you insert the battery. You'd need to be a gynaecologist with auto electrical skills to work in there:D:D:D
 

SirN

New Member
I pulled the leisure battery out and found the answer to question 3. Right at the rear of the battery compartment is what I believe is a split charge relay, showing a positive connection from each battery. No B2B charger.

View attachment 1662


Can't see how you gain access to work on the components in the battery box other than from where you insert the battery. You'd need to be a gynaecologist with auto electrical skills to work in there:D:D:D
You will need to remove the seat.
 

Samebutdifferent

Active Member
You will need to remove the seat.

I've owned a VW and Fiat with batteries under the seat. With both removal of the seat was required to change the batteries, it was obvious that to gain access the seat had to be removed.


Im not so sure with the MP, they are very heavy and awkward to remove that's why I haven't tried.

Do you know for sure that access to all the electrical installation will be easy after the seat is removed?
 

Samebutdifferent

Active Member
@SirN removing the seat is the first stage, you then have to remove the complete seat box to gain access to the electrical installation. Not a quick and simple job.
 

enano

New Member
I've owned a VW and Fiat with batteries under the seat. With both removal of the seat was required to change the batteries, it was obvious that to gain access the seat had to be removed.


Im not so sure with the MP, they are very heavy and awkward to remove that's why I haven't tried.

Do you know for sure that access to all the electrical installation will be easy after the seat is removed?

It is not necessary to remove the seats. You can replace the batteries and work on the cabling around them simply by removing the plastic cover (pull firmly and it pops out).

Left side cover removed:

20200530190954.jpg


Then you simply remove two screws (see pic above, two screws that keep the black metal battery holder in place), move the cables aside, and pull firmly the battery out. It is heavy and will take some effort.

The following picture show the battery tray empty. It is not a large space to work in, but certainly much easier than with the battery in place :)

20200531210437.jpg


The right hand front seat is the same, but contains the main battery (for the engine).
The third battery someone mentioned in this thread is a small, auxiliary power source apparently for the electric parking brake and the automatic transmission. If you run out of battery and need a tow, you still need to release the parking break and switch to neutral... which you cannot do without battery. Thus, the Mercedes solution was to add a third battery (!).
 
Top