Dethleffs battery (2 Viewers)

[MH newbie]

Hi, we have had a new Dethleffs Trend T6757 since last October and due to lockdown it has been in storage for the most part. Whilst in storage we have had to start it up every few days and if we leave it longer then the battery is dead and we have to jump start it.
Has anyone else had this problem as the dealer is saying there is nothing wrong with it?
We also have a solar panel fitted but have no way of seeing how much charge that is giving, if any.

 

[Stanbrook]

Dethleffs Trend T6757 is a great choice

Welcome to the best motorhome site on the internet.
The only sure way to stop the battery going flat is to put more charge in than the out going load.

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2016 motorhome manual:

Briefly press the "12 V" button (Fig. 188,18). The 12 V living area power supply
is switched off. The "12 V" indicator goes out.
Activating battery separation
(transformer/rectifier
without battery cut-off
switch):
Switch off 12 V power supply.
Press button for living area battery (Fig. 188,14) and hold it down for approx.
10 seconds. The "V" volt (Fig. 188,2) and "A" ampere (Fig. 188,3) symbols flash
three times. The living area battery is disconnected from the 12 V power
supply.
Deactivating battery
separation (transformer/
rectifier without battery cut-
off switch):
Press the "12 V" button (Fig. 188,18) and hold it down for approx. 5 seconds.
The "V" volt symbol (Fig. 188,2) flashes three times. The living area battery is
connected to the 12 V power supply. The indicator lights up after approx. 2 sec-
onds.
9.11.3 Batteries gauge
The voltage and charging/discharging of the living area battery or the starter bat-
tery voltage can be indicated using the batteries gauge.
Displays: Press button for living area battery " " (Fig. 188,14). The "V" volt symbol
(Fig. 188,2) lights up. Depending on whether the battery is being charged or
discharged, the "A" ampere symbol lights up white or red respectively. The
battery voltage and current of the living area battery are displayed using the
LEDs in the gauge.
Press button for starter battery " " (Fig. 188,15). The "V" volt symbol
(Fig. 188,2) lights up. The battery voltage of the starter battery is displayed
using the LEDs in the gauge.

I am afraid all leisure batteries go flat sooner or later...

 

[MH newbie]

Hi - thank you for your reply and yes we are really pleased with it.
We have made sure that everything is turned off so the only thing using power is the alarm. Is it normal for the MH battery to have to be jump started that often?

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[Stanbrook]

You could use a clamp on DC ammeter about 15quid to check out the current draw at the starter and leisure battery leads.

 

[Richard n Ann]

Don't buy that one though as it's AC only on the clamp...

Get the little Uni-t one...

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[MH newbie]

Ok, thank you both - we will look into purchasing to try to identify the problem.

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[MH newbie]

One other thing that is baffling me (as you can tell first motorhome!). The dealer said that the vehicle battery on the control panel will never show as fully charged (it has never gone above half level on the control panel but the leisure one is fully charged). Can anyone explain why that would be?

 

[cmcardle75]

Hi, we have had a new Dethleffs Trend T6757 since last October and due to lockdown it has been in storage for the most part. Whilst in storage we have had to start it up every few days and if we leave it longer then the battery is dead and we have to jump start it.
Has anyone else had this problem as the dealer is saying there is nothing wrong with it?
We also have a solar panel fitted but have no way of seeing how much charge that is giving, if any.

Yes, this is completely normal. A unused modern motor vehicle will run its battery down somewhere between a week and two months. One fitted with an alarm/tracker will be on the shorter end of this.

Running the engine in idle for a short period while will not substantially charge the battery. You need a few hours of actual driving to fully charge the battery. At idle, the alternator will not provide as much power, taking many hours (which will damage the engine). Running it for 15 minutes will only put a bit of charge back in. However, due to the chemistry, you may be fooled into thinking it is fully charged, as just that little bit will be enough for the starter motor to sound healthy when used.

In storage, it is best to disconnect the battery. If you need the alarm/tracker to be running, then you'll need to find an alternative method of battery charging. Your choices are solar (but can be difficult in the depths of winter), electric hookup (you might not have this facility), or going down to storage every few weeks and swapping out the engine battery with one you've just freshly charged at home.

Regularly running down the battery may have damaged it and it will no longer have as high a capacity as when new.

 

[Pausim]

Your solar panel may be looking after the leisure battery but not providing any charge to the engine battery. The engine ECU always demands some power and alarms and trackers add to this demand. The cab radio will also need a small supply to retain it’s memory but I have heard that some cab radios go into a standby mode instead of fully shutting down and use a lot more even though they appear to be off. Perhaps worth looking at the radio manual to see whether this might be contributing to your problem.

These permanent demands are sometimes called Parasitic but this is misleading because they are necessary to maintaining the operational readiness of the devices. The term Quiescent Current better describes the power needed when the device is not operational.

Running diesel engines for short periods, particularly on tick over, is bad for them. They need to get properly hot under load i.e being driven.

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[Lenny HB]

No not normal you should be able to leave a Ducato at least 3 to 4 weeks.

If it was a stock van you bought rather than a factory order the battery has it has probably been left to go flat by the dealer and it is now goosed and you need a new battery. You will probably need a new leisure battery as well.
Also sounds like the solar has not been set up to charge the engine battery.

You should never start and leave a modern diesel running on tickover should always be driven straight off after starting can be very costly otherwise.

 

[MH newbie]

Yes, this is completely normal. A unused modern motor vehicle will run its battery down somewhere between a week and two months. One fitted with an alarm/tracker will be on the shorter end of this.

Running the engine in idle for a short period while will not substantially charge the battery. You need a few hours of actual driving to fully charge the battery. At idle, the alternator will not provide as much power, taking many hours (which will damage the engine). Running it for 15 minutes will only put a bit of charge back in. However, due to the chemistry, you may be fooled into thinking it is fully charged, as just that little bit will be enough for the starter motor to sound healthy when used.

In storage, it is best to disconnect the battery. If you need the alarm/tracker to be running, then you'll need to find an alternative method of battery charging. Your choices are solar (but can be difficult in the depths of winter), electric hookup (you might not have this facility), or going down to storage every few weeks and swapping out the engine battery with one you've just freshly charged at home.

Regularly running down the battery may have damaged it and it will no longer have as high a capacity as when new.

Thank you, that is very informative and helpful.

 

[autorouter]

One other thing that is baffling me (as you can tell first motorhome!). The dealer said that the vehicle battery on the control panel will never show as fully charged (it has never gone above half level on the control panel but the leisure one is fully charged). Can anyone explain why that would be?

Your MH is nearly new, so it might have a smart alternator. These will not fully charge the vehicle battery. They load the engine during braking and overrun, converting the braking effect into electrical energy stored in the vehicle battery. They need to have space in the battery to allow this, so they keep the battery at less than full most of the time. There will be a battery-to-battery (B2B) charger (sometimes called a charge booster) to give the leisure battery a full charge.

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[Pausim]

There will be a battery-to-battery (B2B) charger (sometimes called a charge booster) to give the leisure battery a full charge.

Better to say there should be a B2B rather than will be. I had a Hymer on a Mercedes chassis with a smart alternator and they had overlooked the need for a booster. The leisure battery charging was very poor until I fitted a B2B. I would hope that a new Dethleffs would now have one but I am not sure all our converters will have yet noticed the need for them.