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
Setting the output of the charger prior to van install,I’ve gone for 13.2v of trickle charging of the starter battery.
Work in progress....
the victron family is expanding!
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)
The reason for the black tape over the terminals....when you mount the dc/dc horizontally you reduce the ip rating of the unit
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....
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)
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
Pv enabled,and both batteries receiving a charge.
As the day moves on both batteries reaching float.
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
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
Setting the output of the charger prior to van install,I’ve gone for 13.2v of trickle charging of the starter battery.
Work in progress....
the victron family is expanding!
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)
The reason for the black tape over the terminals....when you mount the dc/dc horizontally you reduce the ip rating of the unit
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....
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)
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
Pv enabled,and both batteries receiving a charge.
As the day moves on both batteries reaching float.
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
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