Well I may have been here a few weeks, but never really introduced myself :)

[Stupid Monkey]

So, I'm in the UK and run MTB events, actually the most popular enduro series in the UK. This means from Feb-October each year I'm 80% of the time away from home, in my campervan. I run 7 events at 6 different venues roughly 1 per month from late March onwards. I've admin (laptop/internet) work to do everyday and stints building MTB trails "on site". Rather than commute me and my dog just live in the truck and have a more relaxed life (no wife/kids to think about).

So as well as the "normal" RV loads that my current setup supplies including heating a 50L hot water tank on dump load I'd also like to run the entire event from solar/inverter rather than use a generator. This is as much for marketing as "environmentally good" as for saving money. But its also safer, with topping up a hot generator with petrol scores very high on my risk assessment. I've other enviro things happening for 2020, including plastic reduction.

At the 2-day events the timing kit (3 laptops, 3 TV's) arent a big load, neither is the PA system, but I also have the "Bar and Bean" serving drinks coffee/beers etc all day (14 hours), coffee machine is 1500w, gas urn for hot water for tea/hot choc, and running a couple of chest freezers as fridges (better insulation) for the cold drinks/milk

Hence the ~11.5 kw/hr bunch of cells to run all this.

I'm hoping that I'll also be able to ditch the generator for my daily food cooking (I do like my halogen oven) or at least from later in the year, maybe not in feb/march when there isnt a lot of sun, but we'll see.

I have room to have 3x the Solar I have (750w) but after reading about how Lithium doesn't like to float all the time I'm sticking with the 2 panels i have now to start with. That should be 3kw/hrs a day, 1 for the fridge/freezer in the RV, 1 for the oven and 1 for everything else & hot-water tank heating for shower.

The 7500kg camper (16,500lbs) also has 50L hot water tank heated by 300w 12v heater on dump load, and I've also ordered a small counter-top dishwasher and small (boat) washing machine, and a domestic 50/50 split fridge freezer.

If anyone thinks I'll end up needing more solar then shout, its easy enough for me to add panels, I could even add 2-4 vertical mounting on the side for winter use if I wanted. I read that you should angle panels to the same degree as latitude, and I'm between 52 and 54 over the 6 venues, so that's closer to 90 (vertical) than horizontal although if you adjust for mid-summer sun at 23.5 lattitude then the effective angle is 30 - and best on the roof horizontal.

I change my mind every hour on putting extra panels on or not ..... but if in Feb i end up running the genny for an hour at night to cook my food, at least my 30A mains charger (victron) can also pump power in

March's event, as well as 1 of the 2 October events have mains electric - not any van-life i have at the venue building before, but its mainly the march/june and August events that are the 3 big ones with lots of work to do beforehand where I'm on site for 6-8 weeks each

Pics for .... well, give you an idea.

My 2019 events you tube playlist, 30mins, if interested https://www.youtube.com/playlist?list=PLp_0utnQ9y8QXNai0S-1v2b_cAGVSW0iu - or just watch round 2 if just 1 round/5 mins

 

[Deleted member 783]

Seems like a lot of fun! (I mean no wife and kids ?)

 

[Supervstech]

If the charge controller is properly setup, it will not float your lithium no matter how much solar you have.

 

[Stupid Monkey]

If the charge controller is properly setup, it will not float your lithium no matter how much solar you have.

maybe float is the wrong word, but hold at max charge which from reading isnt ideal for long life?
Maybe I've got the downsides over-exaggerated? I'm still learning, its a steep curve.
Certainly would be easier with another panel especially when its not very sunny.

Happy to take advice from those that know best

 

[Deleted member 783]

I think you want to just stop and disconnect the charger when you are full with LIP, but I'm definitely still learning too. I believe their low self discharge rate makes floating pointless? Someone will correct me.

 

[gnubie]

Float is a legacy term from lead acid but it's still commonly used to describe charger states. People still see 'float' and 'lithium' break into panic because they fail to understand that.

In practical use, ie where the battery is part of a system that is always supporting a load, you set the float voltage to be at a point where the lithium battery would be resting anyway. By keeping the float voltage at that point the battery will not suffer ill effects. This is the only practical way of doing it in a system that is actively supporting a load by the SCC and the battery (ie, every single off grid system). With the variability of the load the battery is pretty much always going to have some current available to it. The only way to prevent that with today's solar chargers is to charge the battery up, then put it the cupboard and forget about it.

It is possible to set up a control circuit so that when the battery reaches the desired state of charge current can no longer flow into the battery, only out but then you have the situation where as the load on the system ebs and flows current flows out of the battery, then the SCC increases its output to support the load and current flows back into the battery. OMG. We now have another thing to wring our hands over, micro-cycling (and yes, people are already wringing their hands over that and have been for years and years in the lead acid world).

*edits to include more thoughts*

 

[Stupid Monkey]

I think you want to just stop and disconnect the charger when you are full with LIP, but I'm definitely still learning too. I believe their low self discharge rate makes floating pointless? Someone will correct me.

Well i could put disconnects on the panel --> MPPT wiring, but I also have a few smart dump loads to think about.

Anyway, as it happens the video Will put out less than an hour ago covered the voltages etc that can be inputted into the BMS and what sort of time-lengths without any discharge are ok and when you should think about doing something about it. As I've only solar to charge, and not plugged into a mains charger at a park for months on end its something I'm less concerned about now.

So that's just cost me money on panels and MPPT ...