Battery choice under stress conditions

[gblcia]

Hi everyone on forum,

Looking for battery option which would secure following, while i want to be sure i am not compromising battery logetivity in any way(so if i would do 4k cycles at have remaining 80% capacity or more would be fine).

Here are conditions/scenerio:

Atm i am working on mounting 320W solar panels on the roof small caravan with 100/30A Victron MPPT. Because i intend to stay fully off-grid during winter time in Scotland i can see i will need extend PV array -> i think i will be able to accomodate additional 200W-400W on mounts when caravan is stationary and will just mounted at place i stay for long time.

Lets say i would be coming back to caravan at 6pm evening temp. is about 5C inside.

Now i would use 2kw inverter for 3 minutes boil water coffe and simultaniously washing machine on other inverter take 250w and charging batteries 80watts for my dewalt tools. Also I would use computer on DC 80W, lights 20W, let my head lamp charge and phone - 20W. Fridge would take up to 60W.
Big Inverter(planning to have 1 small 400W and 2kw) would go for short time like 5-10 min max.

Its not realistic typical day scenario, but it can get close to this smth like - 2600W discharge rate 216 amp draw. To me sounds very unhealthy for battery life(just in terms of discharge rate).
NOTE: i spoke to diff. sale representatives one did comment that doing discharge over 0.5C isnt good for battery life, other said its not problem, refering going that their batteries can handle 3200W 200ah(https://roamerbatteries.com/shop/p/12v200ah) - though different batteries, here lies confussion for me AND If someone can give opinion here).

To sort and be save here better to go for 2*100Ah batteries which are in total higher rated than single 1*200Ah, almost double?

There is low temp in play, so i wonder how discharge change once we getting close to 0C? say what difference between 0-10 and 10-25 in operation towards longetivity?

They have range for batteries you can go charge -30C so eventually i can go for these yet, might be overkill.

Dod should not be the problem, i would just set limit to myself that i won't cross 50% unless it is really neccesery. I found i would use on average 55-80Ah per day in worst case scenario.

Kettle 2Kw 6 min - 17 amph
Toaster 1Kw 5 min - 7 amph
Laptop 65W 3 hours - 17amph
Fridge 150w in 12h - 12.5 amph
phone charge 15w 3 hours - 4amph
Head lamp 4w 3 hours - 3amph
Lights 20w 5 hours - 8amph
+- 70 amps

I want to know boundaries, if all iam suggesting is just stupid use, which will cause big problem to battery, i would need to change usage and would use rather GAS or using lower rated appliances or just avoid big inverter all together, but i am more about to expanding system rather than restrict it, thats why i am asking this way.

Second thing is charging, if i would get 600W solar panels and manage to push more than 50A to the battery at some point during the day, how this can effect battery life(not temporarily - its more about really long term), again lets say scenario when temp are low 5C?
I am taking into account that i will be managing heat by insulation, yet just would like to know where is limit for battery to be charged with high current?


There are also batteries using heater, yet what is draw for heater and how it would be in winter, how much heater takes from PV yield during the day -> so it makes it sense to use or not( i guess depends on temp. need to regulate and weather conditions - very hard to say, but practically does someone using this or have good idea if this can make sense or not?)

NOTE here: those batteries which can be charge up -30C dont have any heating as they claim, so efficiency here can be better in this regards.


There batteries where 300ah capacity has only 26 Kg, heater inc. etc.

Lithium Leisure Battery - Fogstar Drift 12v 300AhDefault Title

300Ah Fogstar Drift Lithium Leisure Battery | Grade A LiFePO4 cells, High Discharge BMS, Bluetooth, Heating | Lowest Prices in the UK. 10 Year Warranty.

www.fogstar.co.uk

This is a bit suspicious when i look at others e.g 200ah renogy is 27kg. Price for this is very very low, but i suppose there might be some catch.

Appriciate any comments advices, its first battery purchase with practically 0 exp., so you might find a lot of irrelevant what i am asking but better say than be sorry later.

Petr

 

[Hardergamer1]

You are on a very steep learning curve, and you have jumped into the deep end, as the problem you have got it expecting much more energy from solar in winter and in Scotland, I put some links in, so you can see how you will end up with much less energy than you think.

I give you some pointers in no order that will save you some pain, and help thinking along the lines of just how much bigger sized solar system is needed for all what you have listed.

First you said you have 320w of solar, but you add up to 400w more meaning 720w, which will give you about 1kwh on a good day and less than 10wh on a bad day, and this is with the south facing 65-75* angle needed in winter in the UK, and with "pvoutput.org" (Scotland systems linked) you can see how much power others are getting around you in Scotland.

Have you used tools like PVGIS? As that's by far the best tool to use in the UK/EU to give you an idea of how much energy you can receive with your setup and needed angles etc, It also has an excellent part for off-grid, so you can work out the needed battery bank size along with the needed size solar array.

I have never used "Roamer" batteries, but they do seem a bit overpriced, But Frogstar and Frogstar-Wholesale is one of the best places to buy Li-lon cell's/batteries in the UK, with NKON.nl being the best I have found in the EU/UK but NKON is only for DIY battery building, have you thought about using Lifepo4 cells to build your own battery bank? As it can be cheaper.

If this was me, I would think about adding a much bigger mobile array, one you can fold away or one that extends from your roof like an awning, you could buy new full sized 400w+ panes for about £130 each, or buy flexible 100-200w panels to build an array which you can fold away and/or strap to the roof etc, look on YouTube as many have done just that, with one channel talks about caravanning in Scotland in winter, (linked).
Have you brought anything yet like the inverter? As if not, I would change to 24v or above now, as this will give you better efficiency and mean you can use much smaller cabling sizes etc, which will make your life easier when wiring your battery bank up.

Lastly, how are you going to generate power when you have bad weather for a week? First, I would add a split charge system from the tow vehicle, and a small 4stroke generator, and think about a micro wind turbine which you can erect using scaffolding poles from the caravan tow hitch with some guidelines, a friend has done just this near Fort William and is making much more power than his 2kwh solar array with a 300w wind turbine.

I hope you good luck.

See what others in Scotland are getting: https://pvoutput.org/list.jsp?sid=78861

PVIGS: https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html

YouTuber who has some helpful caravanning in Scotland and solar/batteries:

 

[gblcia]

i mean i know in winter no chance solar will produce it... i am not from mars kinda person. Even with 700w 1000w i wont be able to do much in winter time here in UK. But i will extend the field thats where is going to anyway. Have rough exectation during months and will be pleased if i got diesel heater running, laptop for some time, light, just basics...no kettle or anything what takes power that comes later with bigger field etc...i called this science fiction anyway for now

 

[gblcia]

Due to circumstances i am more into what realistic what not, how much turbine can generate compare to panel on average i would be asking plus how much space payload takes so whats efficiency of it - i will be looking at it myself have rought idea as you second person talking about it, worth to look at it then. my roof is already full of panels, that 400w panel needs extra rack and would be stationary. Besides i have big taskslist of just make van solid as damp are still issue, therefore, structural integrity, dont have that much background as i am foreigner and don't have stable home, but somehow i am going , for me would be better if someone throw down some comparable numbers e.g. given how they decided and why with numbering that tell most, its more practical for me. Things like generator i can add anytime, without much planning, my payload is limited....hard thing is more like make things happend and imlementation than offering much ideas, i have them full list, detailed implementation is more important for me atm

 

[gblcia]

i didnt go for roamer as they seems to much money for not much music, compare to FGS drift. Anyway with solar and everyting its experimental process, like with fixing damp, making water not freez in pipes, doing insulation, fixing caravan in way that leek wont meter on critical parts, choosing heater, trying to fix gas pipes, closing old fridge vents, working with jigsaw day and night...its just process for failing and learning, and now i added more talking to people and communication as it makes things easier 2do, not always but there is smth into it, if there is someone really skilled and willing to explain, TBH not many but i found ppl on chat who helped answered any question on spot - specific, rephrase it so i did understand and showed comprehansion, that what i call good job.