Trouble choosing between more solar, another battery or...nothing

[12-volt-vanlifer]

I think you might benifit from subscribing to the forum.

Do you have a real name, make life more easier for us old farts, well this one anyway, put it in your siganture maybe.

Huh, what bearing do either of those have to the discussion?

My name is Steve if that helps you.

 

[Pudsey Bear]

Oh NOOOOO, not another Steve

Actually, it does help me, a bad memory since childhood Steve, I have a little spreadsheet where I keep some members' names because I like to address some people by their proper names, others by my opinion of them

 

[Alshymer]

I normally run with 100w & 100ah, I now have 170w the most I've ever had, we have always wildcamped so we've never have hook up or sit wasting diesel, on the other hand we don't waste energy either so it's always worked for us, I am looking at Lithium fr the first time as my LB is well fecked and has been for some time, but now I need to charge my wheelchair battery.

 

[Pudsey Bear]

Was there a question there?

 

[Alshymer]

Hi
I just bought an Eco-Worthy 280 with Bluetooth.
Very pleased so far.
It was 429€ here in France but cheaper without the Bluetooth.
Try the manufacturer’s website for bargain prices.
Regards
Martin

 

[Moped]

Re The Ecoflow alternator charger - "Not sure how this is different to running the existing dc-dc charger as the engine is running/idling and using the alternator in both cases?"

Not much different really as long as you have a high wattage B2B charger. As long as the alternator has enough spare capacity to take it of course without overheating!

The Ecoflow is a smart unit and will adjust the flow rate automatically so as not to damage the alternator if vehicle power is being used by air con, wipers, lights and fridge in 12v DC mode. It only uses spare capacity up to 800w.

No doubt B2B chargers do this also. Nice to rapidly charge a 100wh lithium battery from 0-100% in 90mins of travelling. We get 2 days use from 100wh so really it requires 45min of driving daily to top up.

 

[merl]

The 100w of solar per 100Ah if battery is a decent rule of thumb for favourable conditions but extra batteries are only relevent if you have spare capacity to charge them and the OP specifically mentioned those less than perfect periods. The rule of thumb dates back somewhat to lead acid and in real terms of capacity lithium out performs LA considerably Ah/Ah. I've got 200Ah of lithium and 240W of solar and personally I find I need more solar, and much more solar in less than perfect conditions.
I know you've had a bad experience previously WRT discharging a LFP too far previously Steve but you really can take them lower than 70% discharged, you'd get nearly an extra 30% capacity from your battery if you took it down to 90% instead and that's perfectly acceptable.

 

[Nabsim]

You ask for our opinions, your choice if you take any or none.

I have 300W solar on the roof (2 x 150W panels in parallel), I use diesel heater for warmth and unless solar is good I use gas for cooking. I have a 110ltr compressor fridge and my 12V usage is approximately 65Ah per 24 hours. 1 have 2 x 100AH dumb lifepo4 batteries fitted at the end of 2018 and still perform as on day 1.

I like to park off grid for a couple of weeks at a time summer and winter usually all in the UK. I am not full time but usually do around 10 months a year in the van.

A typical year I am good on solar for around 7 months which leaves 5 months I could struggle. I carry a generator and have 2 x 30A mains chargers to top up my battery as and when needed. Genny is much cheaper than extra servicing or repairs to a big diesel engine, downside is I have to carry it and I need to carry petrol. Neither are a problem for me.

Before I carried the genny I was snowed in somewhere for 8 days, I had to run my engine for an hour each day to keep a bit of power with the fridge switched off. When the roads were opened again I drove out and for the first 6 or 7 miles I had lots of smoke coming out the van exhaust, that was enough for me to not want to do it as a normal thing (that was sat with food on throttle holding it at 1200 rpm as well).

Last Winter I spent in Scotland, weather wasn't too bad, I didn't get snowed in anywhere but was very cold and snow about. I ended up moving every day or two instead of sitting for weeks and I didn't need to use the genny at all.

Do what works for you

 

[12-volt-vanlifer]

The 100w of solar per 100Ah if battery is a decent rule of thumb for favourable conditions but extra batteries are only relevent if you have spare capacity to charge them and the OP specifically mentioned those less than perfect periods. The rule of thumb dates back somewhat to lead acid and in real terms of capacity lithium out performs LA considerably Ah/Ah. I've got 200Ah of lithium and 240W of solar and personally I find I need more solar, and much more solar in less than perfect conditions.

Indeed, you understand the situation.

I know you've had a bad experience previously WRT discharging a LFP too far previously Steve but you really can take them lower than 70% discharged, you'd get nearly an extra 30% capacity from your battery if you took it down to 90% instead and that's perfectly acceptable.

Well it isn't that I had a problem discharching them that low, my manufacturer specifically told me I could discharge to 0% if I wanted. The problem was I was not aware that you are unable to recharge it if you deplete to 0% as it will not be able to power the components that recharge it!

I was under the false impression that the solar charge controller would power itself and as soon as the sun came up the battery would come back to life. Not so! Had to return to shore to remedy that but lesson learned.

I had considered a low voltage disconnect to prevent that again but I watch it so anally day by day now I doubt I would let it happen again.

You ask for our opinions, your choice if you take any or none.

Yes, thanks for your real world example. Useful data there.

I have 300W solar on the roof (2 x 150W panels in parallel), I use diesel heater for warmth and unless solar is good I use gas for cooking. I have a 110ltr compressor fridge and my 12V usage is approximately 65Ah per 24 hours. 1 have 2 x 100AH dumb lifepo4 batteries fitted at the end of 2018 and still perform as on day 1.

I like to park off grid for a couple of weeks at a time summer and winter usually all in the UK. I am not full time but usually do around 10 months a year in the van.

A typical year I am good on solar for around 7 months which leaves 5 months I could struggle. I carry a generator and have 2 x 30A mains chargers to top up my battery as and when needed. Genny is much cheaper than extra servicing or repairs to a big diesel engine, downside is I have to carry it and I need to carry petrol. Neither are a problem for me.

Hmm, for me I have only struggled for december and january. Probably the difference is you have higher consumption. I only run the bare essentials, no fridge or other 'luxuries' but laptop I must confess is my vice as an inveterate surfer. I use it for hours a day but it is not frivolous stuff. It is nearly all posts like this and other research for off grid living. If not research then buying the various accoutrements for the lifestyle.

Can you tell me how much of the year your 200Ah stays topped up to nearly full/full? As your solar is the same as I have currently it is a good comparison. I question how much use the second hundred Ah would be in, at a guess, months September, October, November. December and January it is a given solar is off the table. Then January, February, March.

I only bought the 3rd panel, bringing me to 300W, before winter and of course was disappointed to see it didn't help nearly at all for then but as soon as January came around I do recall it shot up like a phoenix from the ashes and I was not having to watch my usage again almost overnight.

I don't remember how long it took though until I was hitting full battery days. Also this was before the extra load I have added of about 12Ah per day which will be a sizeable hit.

I think I might go with no action while we come into autumn and then see how I fare. It will only be a day's job to add another battery so can just get it as the situation may arise. If I am not still getting full battery days with just one then I will have saved a few hundred quid!

Before I carried the genny I was snowed in somewhere for 8 days, I had to run my engine for an hour each day to keep a bit of power with the fridge switched off. When the roads were opened again I drove out and for the first 6 or 7 miles I had lots of smoke coming out the van exhaust, that was enough for me to not want to do it as a normal thing (that was sat with food on throttle holding it at 1200 rpm as well).

Yes this was something I investigated too but did not like the idea of having to deal with two different fuel types and diesel generators being so much more.

Last Winter I spent in Scotland, weather wasn't too bad, I didn't get snowed in anywhere but was very cold and snow about. I ended up moving every day or two instead of sitting for weeks and I didn't need to use the genny at all.

Do what works for you

Of course this reminds me that one can always just change their habits to tighten their belt on the consumption front. It is my laptop that drinks all the juice from day to day so I can just decide to do other stuff. Of course it happens to be the time of year you want to be inside more than doing stuff outside away from a screen but so it is.

I was working outside most of winter. In fact I didn't have any heating at all for much of the coldest times when it was down to the minus figures because of course the dc-dc charger konked out during the holiday period when everywhere was closed to couldn't send it for inspection but that was also the time when I ran the battery to nothing leaving me unable to recharge it until I got to mains to give it a boost.

That was unforeseen though and not fun but point is I was outside and working during the coldest times and soon warmed up. It would not be a hardship if I still had heating in the van to come back to once I finished for the day. That time I would just dive into my double sleeping bags!

 

[12-volt-vanlifer]

I know you've had a bad experience previously WRT discharging a LFP too far previously Steve but you really can take them lower than 70% discharged, you'd get nearly an extra 30% capacity from your battery if you took it down to 90% instead and that's perfectly acceptable.

I added more but went over the edit time.

Was writing that a disconnect might not be a bad idea after all then to squeeze all I can from the current battery without the constant concern of running it down to nothing and being unusable. I leave it at 30% as I start to get antsy to want to get back into the green but if I knew there was a disconnect which would go off automatically I wouldn't feel I had to constantly be watching the voltage manually knowing it would kick in and preserve functionality.

So if it did switch it off there would still be enough to power the charge controller and dc-dc charger.

90% seems to be taking it right to the wire though. What voltage does it lose functionality? Perhaps 10.0V and 0%? I know when I ran it right down last time, when I checked on the multimeter it was reading 4V.

 

[Nabsim]

The 5 months where solar doesn't work for me is an approximation. Generally you could say November to the end of March. Because of my usage I work on two and a half days if no solar then I either need to move to charge or get the genny out. I am retired so not working, I am out a lot with the dogs but not like a day at work. I am in a 7.5 meter motorhome and will be in and out with the dogs so it can get uncomfortable if no heat in bad weather.

In January down in Wiltshire (a good few degrees warmer than the Highlands or Peak District) a couple of years ago my diesel heater packed up. I stuck it for about a week with no heating but that was enough, (really should fit a little wood burner).

All fitting another battery does is give you more storage which equates to being able to sit longer before you have to recharge if no solar. If you only have 2 months of the year your solar isn't enough you may manage other ways.

Do you park up on sites or lay-bys/byway type places? If on sites you have the option of leaving a panel out leant against your van while at work, (not advisable if leaving it alone in a lay-by lol). Tilting panels give so much more power than flat on the roof over the Winter months. If you have access to mains during the day you could go for a power station (hackery/ecoflow/bluetti et al) and charge while away from the van. Depends if your outside work has a cabin with power or if you are out on your own.

Another option may be a Juicey Brucie cable with main charger(s) then go and an EV charge point when you need power. Charging that way is much cheaper than a night on a site although you have initial cost of cable and charger(s) if you don't already have charger.

My battery are dumb and don't suffer from the switching off and not being able to recharge although I have only flattened them twice I think since I fitted them. I do something at 20% state of charge these days, doesn't take so long to charge up then

 

[merl]

90% seems to be taking it right to the wire though.

Well no.....99% would be taking it yo the wire, 90% still leaves you 10%

What voltage does it lose functionality? Perhaps 10.0V and 0%? I

That's correct, it loses functionality when the BMS switches off to protect the battery from over discharge, this is usually 10v but more accurately it's when any one cell drops to 2.5v so if the pack isn't particularly well bottom balanced the cut off can be slightly higher.
Your problem with initiating the recharging process after the battery has gone into protection mode could be down to the particular BMS that's contained in your battery but it could down to your solar charge controller which won't initiate until it thinks it's connected to a battery, it does this by looking for for voltage on the output connections and of course you won't have voltage if the BMS has cut off. Did you try starting the engine and charging from the alternator?

 

[wildebus]

I don't worry about Lithium Batteries going down low. The BMS in a Lithium Battery is designed in such a way that if they report 0% or shut off, the cells themselves are not actually at 0%, so there is internal protection built-in.

The main reason why it may not be a good idea to go that low is not for Battery Protection, but to avoid being out of power.

 

[Pudsey Bear]

I'm confused as to why the laptop is taking so much power; it sounds like running on 12V is inefficient.

I use mainly my Dell, and it needs 240V, but at home not an issue. I do take it in the van, but the battery lasts a decent while, and I only use it when I really need to.

I do have a Chromebook, and that charges from a USB-C, so a ciggy socket 5v charger would run that, but could you do what you need on a Chromebook? I tend to get around 5-6 hours before it needs to be charged, and it charges faster than it discharges.

 

[12-volt-vanlifer]

Did you try starting the engine and charging from the alternator?

Yes I mentioned that already, that the dc-dc charger wouldn't work either because it required power from the leisure battery to startup, so the same case as the solar charge controller.

 

[12-volt-vanlifer]

I don't worry about Lithium Batteries going down low. The BMS in a Lithium Battery is designed in such a way that if they report 0% or shut off, the cells themselves are not actually at 0%, so there is internal protection built-in.

The main reason why it may not be a good idea to go that low is not for Battery Protection, but to avoid being out of power.

That is not the worry, as I have stated in the thread. The worry is depleting the battery so it is not functional so I am unable to charge it back up again until I get back to mains power, thus ending my self-sufficiency until it is rejuvenated.

I'm confused as to why the laptop is taking so much power; it sounds like running on 12V is inefficient.

Why do you say 'so much power'? I already queried elsewhere about how much it is using and they told me it is low. It is taking 20W and also reading articles that is about as low as they go for full laptops.

It is just I use it many hours a day which adds up.

The average seems to be 45W or more.

The difference for me is that I was actually using a super low power tablet before, but didn't know it at the time. I checked my notes and that was only using 7W! As that was all I had used before then I did not know that it was low, it was just what it was.

I use mainly my Dell, and it needs 240V, but at home not an issue. I do take it in the van, but the battery lasts a decent while, and I only use it when I really need to.

240V does not give any indication of the power consumption.

I do have a Chromebook, and that charges from a USB-C, so a ciggy socket 5v charger would run that, but could you do what you need on a Chromebook? I tend to get around 5-6 hours before it needs to be charged, and it charges faster than it discharges.

Chromebook from what I read uses similar to what I have already.

 

[colinm]

I'm confused

Wait till you get to the bit about wanting to use the leisure battery to keep the engine running in case of alternator failure.

 

[Pudsey Bear]

Confused is my normal state.

 

[barryd]

I'm confused as to why the laptop is taking so much power; it sounds like running on 12V is inefficient.

I use mainly my Dell, and it needs 240V, but at home not an issue. I do take it in the van, but the battery lasts a decent while, and I only use it when I really need to.

I do have a Chromebook, and that charges from a USB-C, so a ciggy socket 5v charger would run that, but could you do what you need on a Chromebook? I tend to get around 5-6 hours before it needs to be charged, and it charges faster than it discharges.

Laptops use hardly anything if kept fully charged and just surfing or watching stuff. They use a fair bit more if you start gaming. Booth of ours use about 12-15w just watching stuff or surfing the net. You still have all the other stuff though, lights, heating, pumps I guess.

I only know what I have learned from the experts on here but it sounds to me like the OP just needs to match the batteries to the solar which is the rule of thumb I believe. January and December though. Personally I would be hooked up!

 

[wildebus]

Wait till you get to the bit about wanting to use the leisure battery to keep the engine running in case of alternator failure.

That is not a problem
I had my Alternator die a few months ago. Simply connected a mains charger to the starter battery, plugged into a van socket fed by an inverter driven by the leisure battery and bob's your uncle Did this and then drove to the garage around 15 miles away for them to change the alternator.

And by leaving the B2B enabled, the leisure battery was getting charged by the mains charger, so had perpetual power








(PS. I DID turn off the B2B ; ) )