Batteries off grid - my findings - my fix

[Don Quixote]

Some of the post so far state "fully charged" - guys this is not possible in some cases as your charging system will not allow FULLY charged as they only charge at 13.8 and to get a fully charged rate you need 14.4 or better. On hookup, chargers are limited to 13.8V....enough to keep them alive, but not enough to charge them FULLY. On solar panels the same thing happens
This is why I started the thread as so many MH think they are fully charging and they in fact topping up only. As I have stated in first post "A battery needs about 120% INPUT to get to full charge... so ...your 110 leisure battery/batteries would need: 110 x 120% = 130 Amps per hour not possible from a small solar panel/panels or standard charging system fitted to most MH.

 

[Ivory55]

If the cage under a van holding the battery was insulated, ie 1" polystyrene around it. Would this help or would that make them to warm in the summer ? It's just that the space wasted under the van seem like it's begging to be used.

 

[Mike B]

 

[maz]

Some of the post so far state "fully charged" - guys this is not possible in some cases as your charging system will not allow FULLY charged as they only charge at 13.8 and to get a fully charged rate you need 14.4 or better.

All I know is that at this time of year with a good amount of daylight (not necessarily sun) by early afternoon the regulator has switched to 'float charging' and if I check the voltage reading before I go to bed it says 12.7v. That's full enough for me.

 

[andy63]

an interesting thread, so ill add my little bit.
for a small van i think my power consumption is quite high,
main items are a 65l waeco comp fridge, eberspacer hydronic diesel htr running a modular combitronic hot air and hot water system and a 12 v telly rated at 35w then led lighting .
i have a power management panel, and although it varies a bit i can draw 25 to 35 ah per night.

just back from 3 nights with no hook up and when i left the panel was showing a deficit of 56ah.
i had an 80w portable solar hooked up during the friday afternoon, all day saturday and about 4hrs on sunday in cloudy with spells of sunshine conditions...the fridge was left on continously , the heater used for about 4hrs and the telly run for about 3 hrs in total. the 5hr drive back has reduced the 56ah defecit back to 0ah on the panel..thats just with a 120 amp VSR connecting the leisure battery bank of 2x 110ah batteries to the altenator.

the 80w panel reduces the ah defecit down to a few ah's during the day so more or less caters for the fridge .

i noticed the panel has a pwm controler fitted and doesnt charge continously , would there be any benefit in fitting a small mppt controler ?? instead of the pwm thats fitted (any advice appreciated there )

seems to me to be a good move to have a power management panel that shows leisure battery usage in ah's or do most think just monitoring battery voltage to be a good enough guide.

ta andy

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[Wildbill]

just been off grid for five days never had a power shortage only have 80W on the roof
and even in winter it works good

 

[tambo]

In winter, 24/7 diesel blown heating, TV, satellite system, lights, charging phones and laptop, hairdryer, for 2 days at -5 to -20 or less!

We recharge every other day.

In the summer, those batteries save gas by boiling the kettle!

Are you full timing?

I suppose the most im ever in one place is 2 nights so my battery is charged when driving , heating is gas with fan assist which I forgot to mention in my usage and phone chargers etc,

Still seems a lot of expense in solar panels triple batteries etc .....glad I don't need them lol

 

[jonandshell]

Are you full timing?

I suppose the most im ever in one place is 2 nights so my battery is charged when driving , heating is gas with fan assist which I forgot to mention in my usage and phone chargers etc,

Still seems a lot of expense in solar panels triple batteries etc .....glad I don't need them lol

We take the van skiing each year, with no hookup, hence the need for decent batteries.
We have 3x 115 Ah traction monoblocs.

We don't have solar, the opportune charging that solar provides sulphates batteries quickly. Besides, they don't work in limited hours of daylight covered with snow!

We also don't have a generator, it is pointless for us to carry one.

Our solution is Sterling alternator to battery charger. It charges our battery bank at up to 90 amps on just tickover. The batteries are six years old with all their original capacity.

This solution won't be suitable for everyone, but for our off-grid use, it is the ideal no-hassle solution.

 

[tambo]

We take the van skiing each year, with no hookup, hence the need for decent batteries.
We have 3x 115 Ah traction monoblocs.

We don't have solar, the opportune charging that solar provides sulphates batteries quickly. Besides, they don't work in limited hours of daylight covered with snow!

We also don't have a generator, it is pointless for us to carry one.

Our solution is Sterling alternator to battery charger. It charges our battery bank at up to 90 amps on just tickover. The batteries are six years old with all their original capacity.

This solution won't be suitable for everyone, but for our off-grid use, it is the ideal no-hassle solution.

Sounds like that works a treat then ....im guessing you use an inverter to work the hairdryer etc from the batteries

If anything that's something I could find useful as the other half doesn't half moan about no hairdryer despite me having longer hair than she has and I manage fine.
I was going to get an inverter but figured I'd need a pretty big one and don't really want to add more batteries to run it as I can survive without one

She has gas operated straighteners but no one's invented a gas hairdryer yet unfortunately

 

[jonandshell]

We have a 2100 watt inverter for running the 240 volt system.

Other duties involve running straighteners, the compressor for inflating the canoe and running the fridge whilst on the ferry!

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[Don Quixote]

just been off grid for five days never had a power shortage only have 80W on the roof
and even in winter it works good

But you don't say what you have been running each day amp wise and what batteries you have fitted.

 

[Wildbill]

But you don't say what you have been running each day amp wise and what batteries you have fitted.

I have two battery's think there 110 amps each.
80 W solar I run my lights and TV I don't get to anal abut it I don't know it just works.
we usually only stay one or two days in one spot.
I also run my lap top on a inverter think it's 300amp inverter but don't know for sure it just works.

 

[andyman]

2 x 85 amp batteries, and a 80 watt solar panel. 3 people in the motor home and all showering once a day and 3/4 hours tv each night.Only drove the motorhome about 10 miles in five days and full batteries when we left the site.
That was this summer in the UK.

 

[Don Quixote]

I have two battery's think there 110 amps each.
80 W solar I run my lights and TV I don't get to anal abut it I don't know it just works.
we usually only stay one or two days in one spot.
I also run my lap top on a inverter think it's 300amp inverter but don't know for sure it just works.

Bill, now we have some facts it makes sense if you're moving every day or two your MH is charging/topping up the 2 x batteries ready for your next stop. The solar panel is on a good day returning 6amps in the UK if you're lucky this time a year, so yes your system is working, however as I have stated your batteries are only getting topped up not fully charged that takes 2/3 days of non stop charging without load. Thank you for the info.

 

[Wildbill]

i

Bill, now we have some facts it makes sense if you're moving every day or two your MH is charging/topping up the 2 x batteries ready for your next stop. The solar panel is on a good day returning 6amps in the UK if you're lucky this time a year, so yes your system is working, however as I have stated your batteries are only getting topped up not fully charged that takes 2/3 days of non stop charging without load. Thank you for the info.

have been stopped for up to five days and still not had any problems if I did I would just ad another bank of battery's we will be home tomorrow and by the weekend they will be back up to full charge.
I am thinking abut BTB charger and 300W soler

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[Don Quixote]

i

have been stopped for up to five days and still not had any problems if I did I would just ad another bank of battery's we will be home tomorrow and by the weekend they will be back up to full charge.
I am thinking abut BTB charger and 300W soler

Bill don't waste your money on the solar panel just get the BtoB charger as it will do the job period. I will do a full review when I have mine fitted and tested.

 

[Wildbill]

I don't waste money searching skips franticly your talking to the world's greatest skip diver

 

[OldAgeTravellers]

Some of the post so far state "fully charged" - guys this is not possible in some cases as your charging system will not allow FULLY charged as they only charge at 13.8 and to get a fully charged rate you need 14.4 or better.

Great post well written John, but I can't agree with your generalisations. I have two 80watt panels wired in series through a good MPPT reg. Which puts out 14.5 volt and 10amps till the batteries are full then settles back to a float charge. Even after a heavy night of usage we are fully charged before lunch. You live in Spain we live in the South of France, I certainly wouldn't be without my Solars. Even on our annual visits to the UK we have no problems. In fact I will soon be replacing my two ageing panels with two 100watt ones so
I can get enough out to run the AES fridge while in Morocco so as to reduce the gas usage and inevitable flue cleaning. The panels I have will manage it but are on their limit. Out of interest we have 2x110 hab batteries, we also have a Gasperini for emergencies but it has only been used a few times when our batteries failed, sulphated up when we just had a standard solar reg.
Steve

 

[eddie]

All these posts are good as they make people think. There is no universal panacea in my opnion, as there is no "standard" weather. If you guaranteed that you would have fantastic sun all the time you could survive on less battery power and a single battery! However, we don't get dawn to dusk sunshine every day. A B2B system is excellent for those that tour, and less so for people that do lots of short trips.

Generators get a lot of abuse of forums, but can be excellent. Remember thought that the majority of 220 volt chargers fitted as standard to the majority of motorhomes, are designed to have mains available 24 hours a day seven days a week, so don't have a massive output, so running a genny with a standard charger could have little overall effect on the true state of charge.

Like all things if money is no object then a more balanced charging regime can be set up.

On my own van, I have 390 watts of solar panels, regulated by Victron MPPT regulators. A very large battery bank. A large built in generator, which charges the batteries via a 100 Amp multi stage mains charger. When the generator isn't running or mains is not available all of the 13amp sockets in the motorhome are ready to use powered by a 2000watt pure sine wave inverter.

This also acts as a interface when mains is available. If the maximum power available from EHU (Electric Hook Up) is say 12 amps and the necessary draw is 16amps the unit recognises the shortfall and automatically, temporarily, suspends charging (which improves the situation anyway) and "inverts" the missing four amps to avoid tripping anything or inconveniencing the occupants of the motorhome (my wife!)

When the engine is running we charge the battery banks from the engine with a factory fitted (my van was ordered in the states) charging system, that we would call a B2B system. I have seen amperages as high as nearly two hundred amps being registered on the battery management computer on start up, so I am confident that whilst touring we have all the power we need.

Not everyone needs all of this, but it is my job, so I like to think that irrespective of what the weather does, we can use our motorhome without compromise. We are not good at turning things off and having to turn one thing off to turn another thing on.

If you look at luxury boats they have a similar set of problems, and the solutions are similar to set ups that I have described above.

If its sunny, save it in batteries. If there is hook up use it. If there's no hook up and it's been overcast for a week, use the inverter. If your driving, use the inverter to do as many things as you can whilst driving, cook, charge things up, cool things down. If your not driving, there's no hook up and your parked in an aire, or a car park or a field on your own, start the generator.

Not everyone has room for loads of solar panels, or the payload or space for a generator or extra batteries, and not everyone can justify the cash on loads of toys, so it is individual choice, but there are choices available should you want to investigate a little deeper.

But buyer beware!!! Not everyone needs solar panels, B2B's, extra batteries or generators. So if you buying a van, especially for the first time, suck it and see! You may find that the set up on the motorhome suits you very nicely and isn't a problem!

Many of our customers buy a van and never travel very far, always use sites with hook up, and may stay overnight without hook up the odd weekend through the Summer months. For them, to be dragging extra weight would be daft, as would the cost of such equipment.

However, many of our customers, do want to be more independent, and whilst some are happy to be frugal in the power usage, many (me included ) want to be able to use the van, up to a point with out compromise irrespective of where we are!

 

[jonandshell]

Spot on Eddie!

Your system has to be tailored to one's individual needs.
If not, you are wasting good money and payload on kit that you just don't need!

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[Don Quixote]

Eddievanbitz, that is a very good to the point post thank you.

 

[UK Pete]

I have 100w solar panel 240 ah battery bank, and a sterling batt to batt ,a webasto water and blown air heating system, when i want to heat up water or have heat i turn on the van, this way the draw from the webasto is not all from the batteries and also i am putting a charge into the batteries as the van is running usually about 156 mins, this system allows me to go for as many days as i want off grid, the sterling attached to the van alternator is the best generator you can have in my opinion
pete

 

[peterc10]

So As I have stated in first post "A battery needs about 120% INPUT to get to full charge... so ...your 110 leisure battery/batteries would need: 110 x 120% = 130 Amps per hour not possible from a small solar panel/panels or standard charging system fitted to most MH.

I am not sure that is correct. The 110Ah refers to the capacity of the battery, or to put it another way the amount of energy it will hold, not the rate that it has to be charged at. The 120% I think refers to the potential difference (i.e voltage) that has to be applied in order to get it full, which equates to 14.4 volts in a 12V system. And my charger can apply that amount both from EHU and solar, or so it says at least!

 

[tonyidle]

The big difference is you have 230 watt solar panel, which will make a huge difference. I not sure that it will 100% charge, but cannot be that far off.

Agreed. It's hard to be sure anyway without inconvenient testing. I judge it by when the staged charge voltage drops back to 13.8 from 14. 5.

 

[tonyidle]

I am not sure that is correct. The 110Ah refers to the capacity of the battery, or to put it another way the amount of energy it will hold, not the rate that it has to be charged at. The 120% I think refers to the potential difference (i.e voltage) that has to be applied in order to get it full, which equates to 14.4 volts in a 12V system. And my charger can apply that amount both from EHU and solar, or so it says at least!

No - it is correct. More needs to be put back than is taken out as the battery (any rechargeable battery) is not 100% efficient.

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[jonandshell]

And also the correct charging voltage for an open lead acid cell is 2.5 volts in order to achieve a 100% charge.
This equates to 6x 2.5 or 15 volts.

This rarely applied due to the excessive gassing and water useage, but that's what a cell works best with!

Sterling get close with their charging products at 14.8 volts.

Any lower voltage will not charge an open lead acid battery to 100% capacity. At normal voltages associated with normal motorhome charging systems, including mains, solar and the alternator, about 80% battery capacity is all you will get.

Partial charging causes sulphation on the cell plates. That's why most folks change their leisure batteries every ten minutes, and that's why our batteries are 6 years old and still have their full capacity. They have always been charged with a Sterling B2B and latterly a Sterling A2B charger.

Of course, having decent quality traction monobloc batteries helps too, they are still going strong despite continual 80% discharges.
Sticker-engineered starter batteries don't have a place in our van and never will due to our use age and energy requirements.

But, like Eddie correctly pointed out, you should taylor your system to your needs.

 

[tonyidle]

And also the correct charging voltage for an open lead acid cell is 2.5 volts in order to achieve a 100% charge.
This equates to 6x 2.5 or 15 volts.

This rarely applied due to the excessive gassing and water useage, but that's what a cell works best with!

Sterling get close with their charging products at 14.8 volts.

Any lower voltage will not charge an open lead acid battery to 100% capacity. At normal voltages associated with normal motorhome charging systems, including mains, solar and the alternator, about 80% battery capacity is all you will get.

Partial charging causes sulphation on the cell plates. That's why most folks change their leisure batteries every ten minutes, and that's why our batteries are 6 years old and still have their full capacity. They have always been charged with a Sterling B2B and latterly a Sterling A2B charger.

Of course, having decent quality traction monobloc batteries helps too, they are still going strong despite continual 80% discharges.
Sticker-engineered starter batteries don't have a place in our van and never will due to our use age and energy requirements.

But, like Eddie correctly pointed out, you should taylor your system to your needs.

I'm not sure about 2.5v / cell for maximum charge (http://www.progressivedyn.com/battery_basics.html ). And your statement about the various charging systems isn't entirely accurate. It used to be true that caravan & motorhome chargers were set at the float voltage (approx. 13.8v) but that's changing. My 2005 Hymer for example has a staged charge that achieves 14.8v for a period before settling back to float. A decent solar controller will do the same. All vehicle alternators charge at a constant voltage of at least 14.2v with most nowadays at 14.5+v.

 

[irnbru]

Having read these posts several times in the hope the knowledge might sink in I need to ask can someone explain what a battery to battery charger is exactly for, how does it work etc. It sounds as if we might need one.

 

[Don Quixote]

I'm not sure about 2.5v / cell for maximum charge (http://www.progressivedyn.com/battery_basics.html ). And your statement about the various charging systems isn't entirely accurate. It used to be true that caravan & motorhome chargers were set at the float voltage (approx. 13.8v) but that's changing. My 2005 Hymer for example has a staged charge that achieves 14.8v for a period before settling back to float. A decent solar controller will do the same. All vehicle alternators charge at a constant voltage of at least 14.2v with most nowadays at 14.5+v.

Firstly 13.8 is FLOAT charge...... secondly all vehicle alternators charge at voltage of at least 14.2 is correct HOWEVER most charging systems fitted in motorhome these days DO NOT all 14.2 volts for a long period of time and step the voltage back to FLOAT charge of 13.8. If the voltage was allowed to stay at 14.2 or better the amps would be in the high 25/30/40 amps - if this was the case your batteries would charge in no time!!!!! BUT because it is stepped back this is why does it take 8+ hours of driving to charge the batteries.......

As I have stated already this is a "gray area that many do not understand" - why would Mr Sterling make the battery to battery charger if the system fitted in motorhome or boats for that matter have such a good system fitted already ??? - CBE or any other system fitted will only charge your batteries to 80% period. They DO NOT FULLY charge your batteries. it takes 2/3 days of charging with NO LOAD to fully charge batteries.

 

[eddie]

Most European motorhome have a "split charging system" People think that this means that when the engine is running, that the leisure battery(s) get charged and then the engine battery is charged. The reason that they're split is to ensure that the power that you use for lights heating and pumps doesn't flatten your engine battery.

However, when your driving the engine and leisure batteries are simply connected together. This has numerous consequences, if one battery is faulty, it will effect the other, if one battery is flat and you run the engine for a short time, you have two flat (ish) batteries, and as all motorhome start life being built on chassis designed to be delivery or builders vans, the charging system is designed for regular "stop start" driving more than occasional long runs.

Also the chassis manufacturer, installed one battery, very close to the alternator, with a very thick piece of cable, whereas motorhome manufacturers tend to locate the leisure battery(s) where there is a space and connect them together with a bit of wire no thicker than a boot lace!

German manufacturers like to connect Gel batteries to Lead acid batteries despite different charging voltages.....it goes on and on.

With a Sterling Battery to Battery (B2B) charger in essence it connects the leisure battery(s) to the B2B and the engine battery to the B2B using very thick cable (determined by the position of the leisure batteries)

When the engine is started the B2B isolates the B2B for a short time while it checks that the engine battery is OK then, sends a message to the alternator the battery is flat and needs a good strong charge, which the alternator provides. The B2B then says "thank you" and diverts this higher charge, through the correct gauge wire and charges the leisure battery(s) correctly and safely.

We average about a 35-40 Amp charge on engine tick over on most installations, which isn't to be sneezed at! Some manufacturers are seeing the light and installing "better" charging systems, so again, you need to know what you need, rather than throwing money at a "gadget" that you don't need (no reflection on the B2B with the word gadget, but buying anything that you don't need is a waste of money)

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