Motor Mover / Battery Query

[otherclive]

We recently had a similar problem,sometimes the mover worked other times it wouldn't.couldn't understand it.Then checked the battery connections,found both positive and negative connections slack,after tightening connections mover works every time.

Another possibility could be the wires in the terminals may be loose and not sufficiently clamped by the screws. Assuming it’s the normal rubbish type of fitment usually supplied.

 

[GrinningGrandad]

Just thought I would post an update on this issue.
.
I had the Motor Mover installer back who did some checks and (unsurprisingly) said it was nothing to do with the MM and must be a battery fault. Before I rang the dealer I thought I would do some checks (to rule out an obvious error on my part and also to provide some detail for the dealer). We were due to go away in 10 days so thought I would emulate our previous trip but this time take voltage readings at various intervals before, during and after our trip. One thing I did notice was the MM cable and the charger cable were poorly stuffed in together on the battery terminal clamp and the screw was quite loose so I removed the MM cables completely.

Day 1 : After 24 hours EHU at home with just the charger/power supply connected I got 13.69V
Day 2 -3 : I disconnected and removed the battery completely and it dropped to 13.08 V ( At this point I also connected the EHU and took a reading from the loose charger cables and got 13.79 V)
Day 4-6: Connected back to the charger in the caravan with no EHU & no MM and it eventually dropped to 12.90 V
Day 7-8 : Connected the MM to the battery (There were spare terminals on the battery so I connected the MM to those instead), No EHU, and it dropped to 12.86
Day 9 (Day before departure) With EHU it went to 13.47
Day 10 (before setting off) : Removed EHU - 13.19V ; Used MM for 5 mins and it dropped to 12.75V ; Connected to car and started engine, went to 13:20 V
(on arrival at site - 2 hours later) 13.05V
(after using MM for 5 mins) 13.05V
(after EHU on site for 4 days) 13.77V
Day 14 (Removed EHU just before departure) 13:09 V
(after using MM for 5 mins to hitch up) 12.80 V
(on arrival at home 2 hours later before using MM) 12.99V
(after using MM for 5 miniutes) 12.73 V

Apologies about all that info.

There were a couple of anomalies, it seemed to charge more during the out journey (fridge turned onto 12v) than the return journey (fridge turned off) even though it was the same time/distance. Using the MM both times at home used quite a bit of power yet it didn't use any whilst pitching up despite it being on gravel and moving onto a ramp.
However, as my manual says 12.7 V is 100% charged and it never dropped below 12.75 I am assuming, with my limited knowledge, that everything is OK. I know the charger is working correctly, I know the battery is holding charge and I know it's being charged whilst driving. After all that, as mentioned a few times on here, it could have been simply loose connections on the battery.

 

[ProfJohnL]

There has been another thread running where a mover apparently stops while in use. The information about battery voltages is interesting, but they key measurement is the battery voltage when the mover is operating. If the battery cannot sustain enough current to power the mover, the terminal voltage will drop, and the mover may trip out on low voltage.

A damaged battery may well be able to produce enough voltage to show normal levels when unloaded, but a high resistance cell will cause a significant voltage drop when asked to deliver a currentl.

 

[otherclive]

Just thought I would post an update on this issue.
.
I had the Motor Mover installer back who did some checks and (unsurprisingly) said it was nothing to do with the MM and must be a battery fault. Before I rang the dealer I thought I would do some checks (to rule out an obvious error on my part and also to provide some detail for the dealer). We were due to go away in 10 days so thought I would emulate our previous trip but this time take voltage readings at various intervals before, during and after our trip. One thing I did notice was the MM cable and the charger cable were poorly stuffed in together on the battery terminal clamp and the screw was quite loose so I removed the MM cables completely.

Day 1 : After 24 hours EHU at home with just the charger/power supply connected I got 13.69V
Day 2 -3 : I disconnected and removed the battery completely and it dropped to 13.08 V ( At this point I also connected the EHU and took a reading from the loose charger cables and got 13.79 V)
Day 4-6: Connected back to the charger in the caravan with no EHU & no MM and it eventually dropped to 12.90 V
Day 7-8 : Connected the MM to the battery (There were spare terminals on the battery so I connected the MM to those instead), No EHU, and it dropped to 12.86
Day 9 (Day before departure) With EHU it went to 13.47
Day 10 (before setting off) : Removed EHU - 13.19V ; Used MM for 5 mins and it dropped to 12.75V ; Connected to car and started engine, went to 13:20 V
(on arrival at site - 2 hours later) 13.05V
(after using MM for 5 mins) 13.05V
(after EHU on site for 4 days) 13.77V
Day 14 (Removed EHU just before departure) 13:09 V
(after using MM for 5 mins to hitch up) 12.80 V
(on arrival at home 2 hours later before using MM) 12.99V
(after using MM for 5 miniutes) 12.73 V

Apologies about all that info.

There were a couple of anomalies, it seemed to charge more during the out journey (fridge turned onto 12v) than the return journey (fridge turned off) even though it was the same time/distance. Using the MM both times at home used quite a bit of power yet it didn't use any whilst pitching up despite it being on gravel and moving onto a ramp.
However, as my manual says 12.7 V is 100% charged and it never dropped below 12.75 I am assuming, with my limited knowledge, that everything is OK. I know the charger is working correctly, I know the battery is holding charge and I know it's being charged whilst driving. After all that, as mentioned a few times on here, it could have been simply loose connections on the battery.

What a tour de force. Glad you found the problem. Although I’ve lost track of the number of times I have advised users to check the cable tightness as it’s more likely to be loose cables in the terminals than loose battery terminals.

 

[Hutch]

Done the same myself, check all cable tightness, even the ones one the Blue box ( power touch) for security.

 

[bertieboy1]

Prof,
High resistance produces the least (smaller) volt drop,low resistance produces the higher volt drop.

 

[otherclive]

Prof,
High resistance produces the least (smaller) volt drop,low resistance produces the higher volt drop.

Doesn’t voltage drop equal IxR. So for a given current increasing resistance will increase voltage drop.

 

[bertieboy1]

Otherclive,Your correct but omitted the whole story !.You conveniently forgot that I=V/R so for a low resistance eg 12/1 = 12 amps but for a high resistance 12/100 =0.12 amps.
The lower resistance produces the higher current and therefore the largest volt drop

 

[ProfJohnL]

Otherclive,Your correct but omitted the whole story !.You conveniently forgot that I=V/R so for a low resistance eg 12/1 = 12 amps but for a high resistance 12/100 =0.12 amps.
The lower resistance produces the higher current and therefore the largest volt drop

Hello Bertieboy

I'm not absolutely clear which of my comments you are questioning, but within this thread (which I have reread) I have not made any claim that is described by your equations. Perhaps if you could quote my comment, I can address the specific points you are queerying.

 

[Guzzilazz]

Bertieboy should be clearer... He is referring to Voltage drop AT THE BATTERY TERMINALS... and in that context he's absolutely right. A dead short will result in a huge current being drained from the battery and therefore a large Voltage drop on the battery. However, the voltage drop (using the term in the conventional sense along the circuit) in the short will be tiny and the current will be huge

 

[bertieboy1]

Hi Prof,
If you read the post you will see it's not addressed to you but to "Otherclive"

 

[ProfJohnL]

Otherclive,Your correct but omitted the whole story !.You conveniently forgot that I=V/R so for a low resistance eg 12/1 = 12 amps but for a high resistance 12/100 =0.12 amps.
The lower resistance produces the higher current and therefore the largest volt drop

Hello again Bertie,

I suspect you have not clearly understood the issue of a high resistance battery cell and its effect on the ability of a multicell battery to deliver current.

Caravan and car batteries are multicell batteries usually of 6 cells connected in series. In a fully charged battery in good condition each cell will have a terminal voltage of approx 2.3V. This gives the whole pile a terminal of 6 x 2.3v = 13.8V. This is the EMF available within the battery.

For what follows I will use assumed values which are reasonable, but each battery design will be slightly different and the values will change due to environmental conditions and age.

Battery cells cannot produce an unlimited peak current. They have limits which are determined by the cells internal resistance. In a good battery each cell’s internal resistance will be in the order of
0.002 Ohms (2 mOhms).

As all the cells are connected in series, each cell's internal resistance is added to the total for the battery giving a total of about 0.01Ohms for a caravan leisure battery capable of sourcing about 80A

If a good battery is asked to produce 80A, the current flowing through the combined internal resistance will cause the terminal voltage to droop by (Amps x Resistance ) 80 x 0.01= 0.8V

Battery internal resistance will tend to increase with age and other factors over time, which is why older batteries are less able to power high current loads. If each cell were to produce a resistance of 0.01 Ohms then an 80A load would produce a drop in terminal voltage of 80 x 0.06 = 4.8V. That would mean instead of 13.8V the terminal voltage would be only 9.8V and many movers would cease to work with such a low supply voltage.

The type of fault I was trying to explain was when just one cell in a battery may have developed a greater internal resistance, it would have a similar effect as above in terms of current sourcing capabilities.

 

[jayw]

rather than starting a whole new thread on a similar topic, our 2006 fleetwood has a battery, could be the original, that is dead. when i hook the car up with the 2 leads, the towing lights work, courtesy of the black lead, but no power from the grey lead. i connected the battery and still no power. i'm assuming the tow plug is wired correctly (fitted by a towbar specialist), 13pin, then using a splitter to provide 2 sevens, the 2 cables from the caravan are then plugged in. would a new battery solve the problem? Is it a fuse, dodgy cable or the specialist towbar fitter rigging the 13pin for the 7 towing electrics (forgetting about the others)? How could i diagnose where the problem is, please? Thanks in advance

 

[Damian]

Quote " i'm assuming the tow plug is wired correctly (fitted by a towbar specialist)"

First mistake..... NEVER assume anything.

Depending on what car you have and what the fitter used to connect your wiring, such as a car specific loom, it may well be that the 13 pin socket is not fully wired and that the connections for the battery charging and fridge are not present.
It is also the fact that if wired correctly, when connected to the car the 12v system is isolated except for the fridge and battery charging circuits.
You also say the present battery is dead, either charge it, if will , or get a new one.

 

[bertieboy1]

Hi Prof,
Wrong again !,nothing I have said is incorrect,I know perfectly well about batteries and their construction/makeup.
It doesn't matter whether the resistance is internal or external (usually cabling sometimes the load) to the battery,the result is the same - the inability to produce a high or sufficient current for the device to operate.
The fault found is slack wiring/terminals and that manifests itself as a resistance hence the inability of the mover to work

 

[Damian]

Ok, calm down !!!!!

Each person has their own take on what is right and what "should" be right.

If that does not fit with your own perception, don't take any notice, but DONT try and start an argument,,,,,,,,,,,the topic will soon be removed

 

[Icaru5]

With all due respect Damian, in this particular case, I don’t believe that Bertieboys response was even remotely aggressive or antagonistic.

Whilst I don’t doubt that the majority of them are made with the best of intentions and despite often being completely incorrect, particularly of late, the seemingly hubristic responses from the forum member “ProfJohnL” do seem to have been composed by someone who mistakenly considers themselves to be a higher power, or at least an authority of sorts, often unnecessarily digressing into other areas or topics merely to prove a point and to demonstrate a certain level of understanding of physics or electrical theory to those perceived to be less well informed, instead of focussing on the primary objective of this forum, which I understand is to provide helpful, friendly advice to those seeking the same, rather than to make people feel like they are standing trial for asking a couple of questions.

 

[Damian]

With all due respect Damian, in this particular case, I don’t believe that Bertieboys response was even remotely aggressive or antagonistic.

Whilst I don’t doubt that the majority of them are made with the best of intentions and despite often being completely incorrect, the seemingly hubristic responses from the forum member “ProfJohnL” do seem to have been composed by someone who mistakenly considers themselves to be a higher power, or at least an authority of sorts, often unnecessarily digressing into other areas or topics merely to prove a point and to demonstrate a certain level of understanding of physics or electrical theory to those perceived to be less well informed, instead of focussing on the primary objective of this forum, which I understand is to provide helpful, friendly advice to those seeking the same, rather than to make people feel like they are standing trial for asking a couple of questions.

Just to clarify I was not aiming my response solely at Bertieboy, I have seen the other posts and I agree that he was answering a rather terse response by a certain user.

I fully agree that some topics are made exraordinarily long and complicated by certain users seemingly intent on trying to prove their "one upmanship" and perceived intelligence being higher than the other mere mortals, like myself, who have managed to live a long time with day to day knowledge of how various things work, or more importantly don't work, and the fine detail is superfluous to the ordinary user.

I agree that bertieboys answer is more than good enough for the question asked and I have to say that long drawn out nitpicking by others just turns people off reading the forum.

 

[Icaru5]

With all due respect Damian, in this particular case, I don’t believe that Bertieboys response was even remotely aggressive or antagonistic.

Whilst I don’t doubt that the majority of them are made with the best of intentions and despite often being completely incorrect, the seemingly hubristic responses from the forum member “ProfJohnL” do seem to have been composed by someone who mistakenly considers themselves to be a higher power, or at least an authority of sorts, often unnecessarily digressing into other areas or topics merely to prove a point and to demonstrate a certain level of understanding of physics or electrical theory to those perceived to be less well informed, instead of focussing on the primary objective of this forum, which I understand is to provide helpful, friendly advice to those seeking the same, rather than to make people feel like they are standing trial for asking a couple of questions.

Just to clarify I was not aiming my response solely at Bertieboy, I have seen the other posts and I agree that he was answering a rather terse response by a certain user.

I fully agree that some topics are made exraordinarily long and complicated by certain users seemingly intent on trying to prove their "one upmanship" and perceived intelligence being higher than the other mere mortals, like myself, who have managed to live a long time with day to day knowledge of how various things work, or more importantly don't work, and the fine detail is superfluous to the ordinary user.

I agree that bertieboys answer is more than good enough for the question asked and I have to say that long drawn out nitpicking by others just turns people off reading the forum.

Thanks Damian.

 

[jayw]

Sorry, another question. If the caravan is lying up, should I disconnect the battery. I can't seem to find a master switch. I'm afraid there is a leak of power somewhere draining the battery and if left connected it will be drained in a few days. Thank you in advance

 

[Hutch]

Jayw, there are lots of item in your caravan , that although the master switch is off doesn't isolate things. In my case a 2013 Coachman 560, the fridge, the radio, and the security system all drains power. On some the tracker system does the same. On my storage site and my insurance policy I can disconnect the battery which means on those horrible times that I have to not go out for over 8 weeks with the battery only dropping to about 12.7 volts. So either find the power drain and remove the fuse for that, fridge and Even the power master panel. Or disconnect the battery.
Others might differ of course.

 

[otherclive]

I always remove the battery bring it home and put it on maintenance charge. Mainly for security but it helps to maintain charge as this last 12 months the van hasn’t been used very much.

 

[Craigyoung]

Ours has been in since year gone February , has not been disconnected but was a new one and we are out every 5 weeks in ours and gets put away when we come back , I just disvonnect the radio source and the TV booster cable aerial and that's it , I ain't had no problem with it stopping in .

 

[Dustydog]

Ours has been in since year gone February , has not been disconnected but was a new one and we are out every 5 weeks in ours and gets put away when we come back , I just disvonnect the radio source and the TV booster cable aerial and that's it , I ain't had no problem with it stopping in .

I have never disconnected any of my batteries. Like Craig the caravan is used all year round. However, the master switch is always turned off and the fridge fully switched off. The only other power drain may be the alarm system which actually uses its own built in power supply.
I guess there may be the chance of some sort of short circuit. Eg mouse 😛