trickle charging starter battery & Psu modification

Lowlec

EWKY
T6 Pro
having not used The van for 3 weeks,and only use it on weekends Or every other in normal times!..the starter battery was down to 11.8v so I decided on utilising my fixed solar panel on my pop top as a permanent fit & forgot solution to maintain the starter battery,I also wanted to utilise this modification as a power supply to the original van electrics!.When the engine isn’t running the dc/dc charger Becomes a power supply unit to the interior lights,radio etc and still maintains the starter battery too (ie the solar panel/leisure battery powers the radio & cab lights when parked up!). As it stands my 120w solar panel usually gets my leisure battery up to 100% soc and to float by 09:30 on most mornings,with the panel sitting idle for most of the day!.

I've been installing Victron kit for years and done this set up on a mates boat a few years back to keep his bow thruster battery topped up.I have installed a small victron 12/12 dc charger rated at 9amps,the 9 amps is important!(touch on it later).
By using the load output of the Victron mppt to supply the dc/dc charger,and the victron bmv relay to switch it on,it is fully configureable and a controllable stand-alone system that I can control from my phone from anywhere if needed.I also wanted this mod to switch off automatically when the engine is running,as not to interfere With the smart alternator set up!
Although this mod is Intended for trickle charging, I have the option of force charging the starter battery with up to 9Amps if it ever become depleted!

the ‘cause and effects‘ for the charger to engage are as follows.....
1....sun needs to be out and charging the leisure battery to absorption stage.
2....the leisure battery Has to have a 99% soc minimum to switch the unit on.
3....the starter battery must be below 13.6v(ie. no alternator running)
until the above parameters are met the starter battery will not be charged by this set up,and the leisure battery takes precedence to avoid cycling!


120w Fixed solar panel on top of pop top roof

22B898FD-8F2D-4B84-9CA0-2CC2112CD926.jpeg

Setting the output of the charger prior to van install,I’ve gone for 13.2v of trickle charging of the starter battery.

8A0E8410-A8A1-4B62-B49E-18F7BA8A82EA.jpeg

Work in progress....
the victron family is expanding!

8A08D5A4-63C7-4C54-A6B6-B4918C5C6654.jpeg

All cabled up...
The reason you need a small dc/dc charger is because the output of the mppt is 15A.......and the start up/inrush current Of the charger can pull up to 12amps if the target battery has a low Soc!.so if you choose a larger dc/dc then the mppt would detect a short on the output and shut down if the inrush current was larger than 15amps.(also you are only trickle charging)

D593020A-54B8-4504-9E8B-CCB738C253B0.jpeg

A7FF26BB-B1D1-4B7D-97C4-D5E557A90E7A.jpeg
The reason for the black tape over the terminals....when you mount the dc/dc horizontally you reduce the ip rating of the unit
 
Last edited:
As we can see below first thing this morning....sun was up and starter battery was charging,because the battery was so low it started pulling 7.4Amps initially then settled down to 3 amps out of the load terminals of the mppt....

494F2E2D-52D3-46E0-8DD5-EDA7B444EF60.jpeg

The next test was to turn off the pv production on the mppt to drain the battery down to 98% to make sure it turned itself off...obviously during this time the leisure battery was charging the starter battery!(force charging)

8AF65F35-1F08-4AE7-8766-CE08020C7821.png

as per the image...lo & behold, the battery hits 98% soc and the charger stops outputting charge to the starter battery, ie DC loads Is now at 0Watts

B677EFCD-A38B-4E2F-A506-F0E85997EC7F.jpeg
 
Last edited:
A lot of people on the forum just use ‘Battery Master’ style boxes (about £25?) to maintain the starter. I have one basically built in to my mppt. They’re very simple but work in a totally fit-and-forget kind of way.
 
What we are
A lot of people on the forum just use ‘Battery Master’ style boxes (about £25?) to maintain the starter. I have one basically built in to my mppt. They’re very simple but work in a totally fit-and-forget kind of way.
as per above...this is fully controllable to my set up!..and totally isolated from the starter!....not just relying on a diode and few resistors! As you mentioned.
control it remotely,very inexpensive to do.btw way the van came with a Ctek 250.....that went in the skip!
 
What we are

as per above...this is fully controllable to my set up!..and totally isolated from the starter!....not just relying on a diode and few resistors! As you mentioned.
control it remotely,very inexpensive to do.btw way the van came with a Ctek 250.....that went in the skip!

Yeah, your way is definitely more flash, and arrays of blue boxes are definitely a crowd pleaser on the forum! Worth highlighting the simple/cheap way though in case anyone reading just wants to keep their starter topped up as simply as possible.

No idea about the ctek, never used one.
 
Since doing this set up today,and putting proper loading on my solar panel(van facing east!)....I’ve pulled the maximum out of my panel!......

120w panel.........127w max recorded!....lying flat on the pop top

@Dellmassive

B435851C-9658-4A15-8E1D-CA1BC4235A53.jpeg
 
Last edited:
as per above...this is fully controllable to my set up!..and totally isolated from the starter!....not just relying on a diode and few resistors! As you mentioned.
control it remotely,very inexpensive to do.

I would rather pay £60 for the Victron than the £30 for the Votronic diode and resistor!

However, although a very elegant solution, it is over the top for me as simple trickle charge is all that is required and a diode will prevent cycling.
 
Since doing this set up today,and putting proper load on my solar panel(van facing east!)....I’ve pulled the maximum out of my panel!......

120w panel.........127w max recorded!....lying flat on the pop top

@Dellmassive

View attachment 71110
Awsome.... you done well there for 127w.... out of a 120w panel.

What's the panel spec?
 
Side thread.....

@Dilbert . . . Did you see the tear down I done on the Votronic trickle charger?




.
 
Last edited:
@Dilbert . . . Did you see the tear down I done on the Votronic trickle charger?

Thanks @Dellmassive ... I missed this but as we suspected. The PTCs will at least stop it doing anything stupid if the Starter battery is very low.

Thanks for the heads up. :thumbsup:

I have got a diode and a 10W 12V bulb. Can't hurt anything and bulbs are PTC devices. Enough to stop the parasitic draw flattening the starter battery.
 
Yeah, your way is definitely more flash, and arrays of blue boxes are definitely a crowd pleaser on the forum! Worth highlighting the simple/cheap way though in case anyone reading just wants to keep their starter topped up as simply as possible.

No idea about the ctek, never used one.
@t0mb0 have you got a link to those boxes you mentioned pls . . . ?

Battery Master’ style boxes
 
@Lowlec

and you add your setup over here please.



***************************************
Copy & Paste the below to add your setup:

Solar Panel:
Mobile Panel:
Solar charge controller:
DC-DC charger:
EHU Charger:
battery bank:
Battery Monitor:
Inverter:
other:

***************************************
 
@t0mb0 have you got a link to those boxes you mentioned pls . . . ?

Battery Master’ style boxes

I'm pretty sure it's the gizmo you linked to in the tear down above?? Although maybe it's only Roadpro that refers to it as a 'Battery Master'.

 
I'm pretty sure it's the gizmo you linked to in the tear down above?? Although maybe it's only Roadpro that refers to it as a 'Battery Master'.

gotcha . . . yeh same thing.

Im not saying it dont work, . . . . just saying its over priced for what it is.

I've noticed a few people on T6F have them.
 
gotcha . . . yeh same thing.

Im not saying it dont work, . . . . just saying its over priced for what it is.

I've noticed a few people on T6F have them.

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.
 
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.
Agreed.

@t0mb0 can you add your setup to the list pls? :



***************************************
Copy & Paste the below to add your setup:

Solar Panel:
Mobile Panel:
Solar charge controller:
DC-DC charger:
EHU Charger:
battery bank:
Battery Monitor:
Inverter:
other:

***************************************

.
 
Thanks @Dellmassive ... I missed this but as we suspected. The PTCs will at least stop it doing anything stupid if the Starter battery is very low.

Thanks for the heads up. :thumbsup:

I have got a diode and a 10W 12V bulb. Can't hurt anything and bulbs are PTC devices. Enough to stop the parasitic draw flattening the starter battery.

Strange coincidence, I have just fitted a very similar circuit between the leisure +ve and the starter +ve on my T6.

I have a fuse (7Amp) a diode (rated @ 10Amps) and a 55W spotlight bulb. The 55W bulb is to limit the current drawn should the starter battery be very low and I try to start the van. I think the trickle charge from leisure to starter is about 1.0Amp when the solar has the leisure up over 13.5v and the starter is down below 12v, obviously that drops rapidly as the voltage difference between the two batteries approach the forward volt drop figure across the diode.

However the figures work out this seems to keep the starter battery topped up during the periods of non-use. Outside the current lock-down this will never occur as the vehicle is used regularly so this bit of circuit may well be removed eventually.

Cost to me having all but the diode to hand was 85p!
 
Back
Top