trickle charging starter battery & PSU modification

[Mccoatup]

You could certainly buy the components for cheaper. You could also certainly DIY one, although I assume you'd only do this if you enjoyed it as a hobby, I can't imagine anyone actually valuing their time so cheaply that they'd build one themselves rather than shell out £27! Personally, I'd quite happily pay £27 to remove the worry that my starter might go flat every time the van is left for a bit, or for extended wild camping.

Having read about the Votronics unit in this thread I built my version of it into the cupboard at the back of the van.
I did this as (a) I enjoy it, (b) I can and (c) I'm retired! Just added a low voltage cut-off module which I had lying around in case the van battery tries to take too much out of the leisure one. And a couple of LEDs on the worktop side of the cupboard to show when it's charging and if the low voltage cut-off has been reached. PTC fuse to be added too, but hasn't arrived yet.

 

[rod_vw]

Got a few pics of your setup?

It's not elegant and was never meant to be but it's safe and does the job as far as tests have shown yet. The components actually tuck out of sight under the fuse boards within the box which has a clear screwed down lid. The whole thing is on extended looms and slides under the left front seat from the rear.





Circuit diagram...

 

[Dellmassive]

It's not elegant and was never meant to be but it's safe and does the job as far as tests have shown yet. The components actually tuck out of sight under the fuse boards within the box which has a clear screwed down lid. The whole thing is on extended looms and slides under the left front seat from the rear.

View attachment 71257

View attachment 71258

Circuit diagram...

View attachment 71259

side post . . . . . . .

love it.

well done.

mind me asking why a 55W bulb instead of a power resistor?

and

whats the max Amps it will pass?

and whats the diode spec? and forward volt drop across it?

 

[rod_vw]

The bulb - because it was in a box in the garage.

A 55W bulb will drop 12v across it when passing 4.5A. I didn't bother to work any of it out, just put the circuit together first of all with a 21W bulb an nominally saw a trickle of about 0.4A then upped the bulb type to the old 55W halogen and saw a trickle of around 0.9A to 1A.

The diode spec is dubious, it was this eBay item 272689955724 and probably from China imported by the thousand.

The fuse & fuse holder - again because it was in a box in the garage,

As you can see there was no serious technical design, it was simply scratch built at the vast cost of 85p, what had I got to loose?

If you hear no more about this assume it works successfully over time, I'll let you know if I have to change or remove it.

 

[Dilbert]

mind me asking why a 55W bulb instead of a power resistor?

The advantage of a bulb is that it is a PTC (Positive Temperature Coefficient) device. This means its resistance increases with heat; i.e. the more current that is drawn the higher the resistance will go and limit the current at the top end. The worst that can happen with a bulb is that it lights up if the starter battery is very low.

I tried power resistors and all sorts of fancy current limiting circuits. The difference in voltage between the source battery and load battery is too small to allow active circuits to work correctly. A power resistor will get very hot in a low starter battery (high current) scenario. A PTC fuse could prevent this but it will still cycle on and off.

The simple solution is to use a bulb. I just used 2 capless wedge 501 5W bulbs in parallel. That provided enough current to offset any parasitic draw on the starter battery without too much heat if the bulbs were to glow. The box has 2 LED voltmeter displays - one for the source, one for the load. These are switchable otherwise they will use more energy than the parasitic draw. The charging is also switchable so I can use the box for other voltage measuring purposes. A 6A diode in series with the bulbs prevents any reverse charging.

The unit is just temporarily connected between two 12V sockets in the van when parked up for long periods. The 2 plugs are both fused at 2A for additional protection.

 

[rod_vw]

The advantage of a bulb is that it is a PTC (Positive Temperature Coefficient) device. This means its resistance increases with heat; i.e. the more current that is drawn the higher the resistance will go and limit the current at the top end. The worst that can happen with a bulb is that it lights up if the starter battery is very low.

I tried power resistors and all sorts of fancy current limiting circuits. The difference in voltage between the source battery and load battery is too small to allow active circuits to work correctly. A power resistor will get very hot in a low starter battery (high current) scenario. A PTC fuse could prevent this but it will still cycle on and off.

The simple solution is to use a bulb. I just used 2 capless wedge 501 5W bulbs in parallel. That provided enough current to offset any parasitic draw on the starter battery without too much heat if the bulbs were to glow. The box has 2 LED voltmeter displays - one for the source, one for the load. These are switchable otherwise they will use more energy than the parasitic draw. The charging is also switchable so I can use the box for other voltage measuring purposes. A 6A diode in series with the bulbs prevents any reverse charging.

The unit is just temporarily connected between two 12V sockets in the van when parked up for long periods. The 2 plugs are both fused at 2A for additional protection.

That's a great bit of kit, I just went for the simplest and cheapest solution as it is really only needed whilst the van is getting minimal use.

I did think of the plug-in idea between two accessory sockets each on different batteries but erred on the side of simplicity.

 

[Lowlec]

The advantage of a bulb is that it is a PTC (Positive Temperature Coefficient) device. This means its resistance increases with heat; i.e. the more current that is drawn the higher the resistance will go and limit the current at the top end. The worst that can happen with a bulb is that it lights up if the starter battery is very low.

I tried power resistors and all sorts of fancy current limiting circuits. The difference in voltage between the source battery and load battery is too small to allow active circuits to work correctly. A power resistor will get very hot in a low starter battery (high current) scenario. A PTC fuse could prevent this but it will still cycle on and off.

The simple solution is to use a bulb. I just used 2 capless wedge 501 5W bulbs in parallel. That provided enough current to offset any parasitic draw on the starter battery without too much heat if the bulbs were to glow. The box has 2 LED voltmeter displays - one for the source, one for the load. These are switchable otherwise they will use more energy than the parasitic draw. The charging is also switchable so I can use the box for other voltage measuring purposes. A 6A diode in series with the bulbs prevents any reverse charging.

The unit is just temporarily connected between two 12V sockets in the van when parked up for long periods. The 2 plugs are both fused at 2A for additional protection.

View attachment 71339

A very crude method of topping up the starter battery!
The victron dc/dc, control charges The starter battery,with current indication Proper heat dissipation and no parasitic drain on the leisure battery as such.
People spend thounsands on their VW T6’s and resort to things like this!..
...just saying saying!

 

[sparkzer]

Just to lower the tone a bit further...my solution i think has to be the simplest and cheapest, however does require some consideration when to use.

2 fused cigarette lighter plugs back to back via a length of wire and a diode in the back of one of the plugs. Where is the current limiting resistor i hear you ask!?! - there isn't one...i just only plug it in when the starter battery is charged (thus at a similar level to the leisure battery, which due to solar is always full) and therefore is used to maintain the starter battery and not charge it, offsetting the parasitic drain whilst its sitting on my drive going nowhere for weeks on end.

This was really only meant to be an 'experiment' until i could get my hands on a power resistor of which I've 100's at work...however never evolved further.

Worst case is if i plug in the cable when the starter battery is flat and an imbalance in voltages one of the 2A fuses will blow however the cable and diode are rated well in excess of the fuses.

Long term i plan to change the solar charge controller to a unit with a 2nd output, but until now and during Covid..the above is working fine.

 

[Dellmassive]

Lol... I like it.

I'll start a new thread and move these mod over there....

Plus I have something in the pipeline that's a more suitable fix for the people who dont feel comfortable with the electronics.

 

[rod_vw]

A very crude method of topping up the starter battery!
The victron dc/dc, control charges The starter battery,with current indication Proper heat dissipation and no parasitic drain on the leisure battery as such.
People spend thounsands on their VW’s and resort to things like this!..
...just saying saying!

I've spent thousands on this VW and it could still be considered as crude but it's still going after 74 years!



6 volt electrics, no syncromesh, cable brakes and I'm still happy to drive it to Germany to events.

 

[sparkzer]

I've spent thousands on this VW and it could still be considered as crude but it's still going after 74 years!
6 volt electrics, no syncromesh, cable brakes and I'm still happy to drive it to Germany to events.

sometimes the simplest solutions are the best, more to the point if you understand whats going on yourself..you can keep things ticking along nicely

 

[SB6]

Sorry.

l know this is an old thread.

But, would the following item, work the same way as the Voltronic does, for charging the starter battery when the vehicle is on EHU and the leisure battery is full?

CSB2 - CBE

Electronics for Caravanning and Boating

www.cbe.it

Thanks

 

[Dellmassive]

I've not come across that one....

I've have a look at the specs.

More information here;

[Guide] Battery Maintainer (for Starter battery) -- How I Done It --

[Guide] Battery Maintainer (for Starter battery) -- How I Done It -- Right so its that time of year again . . . . . . . . Winter & (Lockdown 2020) The van might be layed up not being used, which will lead to a flat battery in around 3 weeks. The cold weather doesn't help the battery's...

www.t6forum.com

.

 

[Dilbert]

would the following item, work the same way as the Voltronic does

It looks very similar if not the same as the Voltronic. It certainly has the same functionality and will keep your starter battery topped up from the leisure battery.

 

[SB6]

Thanks for the reply’s.

From what i’ve read, it gets a lot of good reviews on Motorhome and Caravan forums.

 

[rod_vw]

I've just added to a six year old thread on the Motorhome Fun Forum asking users for their comments on the CSB2.

See Best place to wire in CSB2 split charger

Maybe someone will comment.

 

[Dellmassive]

@Lowlec

can we have an update on your setup? . .

how is it performing over the winter months? . . maybe some VRM Portal shots?

out of interest . . what type of cable is the blue/brown stuff? . . . looks beefy

 

[Lowlec]

@Lowlec

can we have an update on your setup? . .

how is it performing over the winter months? . . maybe some VRM Portal shots?

out of interest . . what type of cable is the blue/brown stuff? . . . looks beefy

@Dellmassive
system works flawlessly with a victron lithium battery installed the set up is much more stable and predictable,
for the winter months with low/no sun I’ve installed a powercon connector up behind the rear tow point,very discreetly to power up the mains charger,which in turn triggers the mppt and tops both batteries up.
as for the cables tri-rated 6mm for mppt & 16mm for dc/dc charger
upgraded the venus to a Cerbo utilising the the inputs and outputs to control various bits of kit on the van remotely with feedback To the VRM,so I can tell when the eberspacher etc is running.
screen shot below is a typical day In the charging cycle.

 

[Grantls]

Hi Guys, I've just bought one of the Votronic trickle chargers to keep my starter battery topped up from the leisure battery, with the leisure battery being topped up from a solar panel on the roof. Before I install it I'd like to know what stops the starter battery draining the leisure battery if the van is parked indoors with no sunlight? Wouldn't the starter battery become a parasitic drain on the leisure battery? Thanks.

 

[Dellmassive]

Hi Guys, I've just bought one of the Votronic trickle chargers to keep my starter battery topped up from the leisure battery, with the leisure battery being topped up from a solar panel on the roof. Before I install it I'd like to know what stops the starter battery draining the leisure battery if the van is parked indoors with no sunlight? Wouldn't the starter battery become a parasitic drain on the leisure battery? Thanks.

View attachment 119661

Yes . . .

in that black box is just a diode and resistor.



more info here:

[Guide] Battery Maintainer (for Starter battery) -- How I Done It --

[Guide] Battery Maintainer (for Starter battery) -- How I Done It -- Right so its that time of year again . . . . . . . . Winter & (Lockdown 2020) The van might be layed up not being used, which will lead to a flat battery in around 3 weeks. The cold weather doesn't help the battery's...

www.t6forum.com

.







you will better off getting the Smart Unit.


The AMT12-2 has internal smarts to stop the constant drain. (there is a BT & APP for it coming soon too)

AMT12-2 12V 2AMP Trickle Charger - Battery Maintainer - Battery Saver | eBay

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