85 amp leisure , not over a year old .
I have thought about a 115 amp , sure it will give me the back up power in storage , but i have noticed that the solar controller only intervenes at a certain voltage range , at the most sunny part of the day is when my 85 would begin to need food ,this is when the controller would see that its time to bulk charge , i have watched it in the past few days and it does slam the amps in at this stage .
If i was to upgrade to 115 i may well miss this point as the battery would not be so hungry , its kind of like when it goes into float charge at 1 in the afternoon , you just know that the controller is probably binning off a good ammount of ampage .
What you think Spruce ?
Its my opinion that you should just stay with what you have at the present and work with that. The reason for thinking this way is that if you start changing things too much then you will never know what works and what doesn't. You are already experiencing the moving goal posts of the weather and shorter daylight hours as we head toward winter, so adding further changes won't help with your experiment. Once you identify what you are lacking, you can then make better solution assumptions, ie., a bigger panel etc.
Having a bigger battery will give you a bigger storage cushion but it will also take longer to recharge. Then again, if the 85amp battery is fully charged over a weekend and the solar panel isn't being fully utilised then that's a shame. In summer your panel is going to fully charge that battery with excess current being shed/wasted. But as we head into winter the proverbial goal posts will keep moving backwards.
Before this last weekend you will have been 'bench' charging your battery pretty regularily. You haven't needed to so far this week. At 75% charge you might get through today and tomorrow without having to bench charge. If you can then you will have the weekend (provided you aren't working) to let the panel recharge your battery.
You will have a pretty good idea where you are on Sunday evening. If your battery still needs some charge then you might have to bench charge it on Sunday evening. But if you aren't working on Monday then you could leave everything another day and access the situation on Monday evening.
Its just that you want to not let the battery drop to far below 12.4v which is 50% charged. But for the odd experiement it won't be the end of the world doing this. However, you obviously need to have enough power to complete a day's work.
The MPPT controller will suck out everything the panel produces in the early morning. It will be a fractional amount, so could only be described as trickle charging. Once the panel gets into full sunlight the trickle charging will become a boost or bulk charge. Unfortunately you need that extra donge and android/apple app to see exactly what the MPPT controller is doing over the course of the full day and every day of the week.
You already know that your panel isn't going to be sufficient to fully charge your battery in winter, but what you are looking to do is supplement your daily power consumption as efficiently as possible to reduce the number of times you have to bench charge it.
I believe that your experiement will help a few others to go the solar route, but will now realise that it isn't the soul solution for all seasons. If solar works for pretty much 3 of the 4 seasons, then it could well be a wfper's next must have.
I also think that if you also had a split charge relay (which aren't expensive and depending on your van's charging system) could could have replenished that shortfall with a journey time of 1/2 and hour's driving home last night and 1/2 an hour's driving this morning.
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