12v Battery & Mover

[Robtel]

Hi All,
Not sure if this should be under "technical" or " equipment & accessories" but it seems technical to me, (might not be to others).
I used my mover to get my caravan up the drive at the end of last week prior to going away. Due to road layout its easier to use the mover to get the van up and swung around before hitching up. The powrtouch normally copes with the sloping drive without problem but this time about halfway up the mover cut out, stopped dead. Left it a minute or two, reset red mains switch and it started again but only for a few feet then same again. All the lights on the hand control were illuminated and the handset battery is less than a year old. My first thought was the caravan 12v leisure battery, checked the reading on that via the onboard voltmeter ( which I know is not reckoned by many to be accurate) that was showing 12.8v. Phoned powrtouch, they also reckoned it sounded like a leisure battery problem and that the power was dropping below 12v when the mover was being used and that would cause the unit to cut out.
Anyway we got away o.k., used the mover very sparingingly on site, just to line up for alko hitch lock and then final hitching up when coming away. Arrived home and used the mover to position van on bottom of drive way, that would be a good couple of minutes worth of use. Here's where it gets technical, at least as far as I'm concerned. This was when i got the multimeter out and checked the battery with that rather than the onboard version. Battery was reading 12.9v, that was after using the mover to position it. I switched on all the internal lights, checked again, down to 12.8. Engaged the mover, then disengaged it (auto engage model) checked again 12.7. I then started to run the rollers while off the wheels and checked while they were moving, down to 11.8.
So my questions are: Should the reading drop below 12 as the powrtouch tech guy said it shouldn't when the mover is being used? Anybody any idea what sort of draw a mover has? I think what I'm really wondering is that my battery might be on the way out, showing fully charged but not producing the power when asked.
Any thoughts, comments, suggestions welcome.

Thanks
Rob

 

[RogerL]

It's normal for the voltage of a lead-acid battery to drop under load, the more the current draw the bigger the drop.
As batteries age they gradually lose capacity, they may show 12.8v fully charged but in the worst case can drop to 9 or 10v under load - if that happens the battery is time-expired.
Motor movers can draw 90 A at start-up but settle down at a little less - the problem is that leisure batteries simply aren't designed for that current load, anything above 20 A will stress the battery, which is why a 110 Ah leisure battery is recommended as an 80 Ah really can't cope - by comparison a 60 Ah car battery copes admirably with a motor mover as it's designed for 400A starting current. Problem with a car battery is that it's only practical if always on EHU as they don't like deep discharge.
You don't say how big or old your caravan battery is, nor how it's charged - caravan on-board power supplies don't do batteries any favours as they don't charge them fully and allow sulphate build-up - which is why some top models use a dual-stage power supply and proper smart charger.

 

[woodsieboy]

Hi Rob,
We have had similar events occur with our powertouch mover,in our case it was not a battery problem,suggest you try moving the caravan with the lead connected to the handset and if it moves without cutting out it suggests a signal problem,also examine the brushes on the motors,we changed our brushes and all was OK again.

 

[Sproket]

If it's dropping to below 12v with the rollers running free my own thoughts are the battery is on its way out as they normaly dip down but come back above 12v after the initial surge of power, also due to the voltage dropping, the main brain box will be cutting out.....

Would it be possible to connect longer leads to your multimeter & pop it in the window & see what the reading is when the mover is under load ??
Or use one of these to see what amps the motors are pulling when under load

 

[Robtel]

Thanks to all for the helpful replies.
The battery is a 100Ah, agewise I reckon it must be about 6 years old, might even be older. I charge it with the on board caravan charger, and also with a "proper" smart charger every now and then, one that goes up to 14.8v.
The mover itself is less than a year old so I am inclined to think it's time for a new battery, rather than new brushes or similar.
Last time I was in I noticed my local tyre & exhaust depot was advertsing battery testing, do you reckon it would be worth getting it confirmed. What is it they do to test a battery anyway, anything different to what you cn do at home?
Thanks again
Rob

 

[Damian]

A battery in good condition will , on start of the mover , drop slightly but recover to continue to provide a full 12v+, which is what the mover needs to operate correctly.
If your battery dropped to 11v and remained there,under a NO LOAD situation (as you had with rollers disengaged) it will probably drop to muchless,,,maybe as low as 2v under load.
That is the battery on its way out, and certainly not good enough to power the mover.

A garage testing a battery will do a 30Amp drop test on it, which for a leisure battery is not a good thing to do.
However , it will show up any failing cells.

 

[Sproket]

Hi Rob
They would probably do a drop test......
http://www.batteryfaq.org/

But you have already done that with activating the mover with your multimeter attached to the battery...
Time for a new battery me-thinks

 

[Robtel]

Thanks Sprocket and Damien. Oh Well, a new battery then! Great!