Off grid night time battery charging?

[Vic. Parsons.]

Hi folks.
We are currently using two 100Ah Banner energy bull batteries and we have 260w of solar charging them during the day. One of the panels is 80w mounted on our old Oyster satalite and tracks the sun all day.

Given that lead acid gets better charge from a full 24 hour trickle charge to fully charge them, the night time period is of course a time of zero charging and maximum usage, so by the morning the batteries may have recovered slightly on voltage but then have to make do with a day of solar to bring them back up, but often they are not really fully charged even after an 8 or 10 hour period.

So, what I'm wondering is, if we installed a small Lithium ion battery of say 50ah which is charged off a separate solar panel (maybe the 80w sun tracking one), Would it be possible to use this battery as a trickle charging source during the night to give the lead acid a decent night time charge so that they're back on song by the morning and don't need as long to fully recharge during the day?

I don't really want to go down the route of changing over entirely to Lithium due to the charge routines being different to lead acid and of course the cost, but thought this might perhaps be a good compromise.

Any thoughts?

 

[Richard n Ann]

You simply need more solar IMO.

 

[tonka]

My first thoughts are.
1. What regulator do you have ? Changing from PWS to MPPT will make improvement on charging.
2. How old are the Banners ? Maybe they need changing, even if not to old they could have had a lot of use.
3. The idea of using LI-ON just to trickle charge lead acid seems a bit in-effective.

 

[Vic. Parsons.]

You simply need more solar IMO.

So more solar will allow a full 24hr trickle charge?
The solar we have will put in lots of amps until it goes onto "float charge".
This as I understand it, is the point at which the battery is being trickle charged to bring the amp capacity of the battery up.
At this point, the amps going into the batteries from solar is quite low, regardless of the number of watts of solar available.

Perhaps I'm not understanding it correctly, but the extra amps from solar will only bring the batteries to float charge quicker, they won't however make much difference once trickle charging begins?

 

[Jev88]

Can't see the point carrying an extra battery to charge my battery? Just get more solar or add to your battery bank.

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[Vic. Parsons.]

My first thoughts are.
1. What regulator do you have ? Changing from PWS to MPPT will make improvement on charging.
2. How old are the Banners ? Maybe they need changing, even if not to old they could have had a lot of use.
3. The idea of using LI-ON just to trickle charge lead acid seems a bit in-effective.

Our Banners are now 2 years old, being maintained (electrolyte topped up) every 4 months and are pretty much in constant use, and we're using the original Hymer Schauldt equipment.

 

[Two on Tour]

I would have thought that once your hab batteries and the lithium battery voltages have equalised then that's the end of the trickle charge.

 

[tonka]

Our Banners are now 2 years old, being maintained (electrolyte topped up) every 4 months and are pretty much in constant use, and we're using the original Hymer Schauldt equipment.

Maybe check the regulator.. It could be the LR1218 which is PWS technology.
Like a few on here i have recently changed mine for a Votronic MPPT regulator but you also have the easy option of the LRM1218..

I cant really comment further as only changed 2 weeks ago and fitted new Varta 90 batteries at the same time, so its all still under test. I am seeing a higher charge rate first thing in the morning on the few days we have been away.

Schaudt LR 1218 - Solar Regulator

The Schaudt LRM 1218 Solar Regulator is the best, most cost effective way to connect Solar Power to the Schaudt Elektroblock range, i.e the EBL 99 and EBL 100. The box includes all cables and instructions to use a EBL 99 to charge both the Starter and Habitation batteries.

www.aandncaravanservices.co.uk

.

 

[68c]

I thought 'float' was merely a maintenance charge to counteract any very small discharge to battery internal discharge, burglar alarms, controllers etc, and is at a lower charge voltage to the main 'absortion' charge. Once you enter 'float' your batteries are fully charged.

 

[Vic. Parsons.]

Can't see the point carrying an extra battery to charge my battery? Just get more solar or add to your battery bank.

Funny thing is, some Belgian freinds bought a new Hymer with one Lithium battery and two gel batteries, with the lithium there to top up the gels.

I would have thought that once your hab batteries and the lithium battery voltages have equalised then that's the end of the trickle charge.

I was thinking more along the lines of the Lithium battery substituting for the solar during the night.

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[DBK]

The solar we have will put in lots of amps until it goes onto "float charge".
This as I understand it, is the point at which the battery is being trickle charged to bring the amp capacity of the battery up.
At this point, the amps going into the batteries from solar is quite low, regardless of the number of watts of solar available.

Float charge occurs when the batteries are fully charged. They don't need further charging.

I think finding room for a third 100Ah battery would be a better move plus trying to reduce your energy consumption. Optimizing your solar would help if it isn't. Does the tracking panel have its own MPPT controller? It should I think.

 

[The Wino]

Do you ever have to limit the use of anything you would like to use because the batteries are low if not save the money

 

[Off da Grid]

How much power are you using?
I have a 255watt panel on a Votronic mppt 350duo one 110A Leasure and 1 110 starter both lead acid and these get fully charged by lunch time at the latest if the suns out in the morning.

 

[Vic. Parsons.]

This is our current charge amps:

and voltage readings:

 

[dunnah01]

Sounds like it would work in theory but you'd need a DC/DC charger to limit current from lithium battery and a VSR to turn on the DC/DC charger when the solar voltage to the lead batteries drops to a low level at dusk

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[SomeoneElse]

I thought the idea of a battery was to store energy. IE charge by day use at night. If you are charging 24hours a day what's the point you are never going to use it.

 

[Lenny HB]

Lack of solar is your problem once past October to get any useful solar input you need 500 -600 watts minimum.

Trickle charging only maintains an already charged battery for a proper charge of a wet cell it needs to be charged up to 14.4v the have an absobtion charge of an hour at 14.4v volts with the current limited to about 1 amp, then the charger should reduce to 13..6-13.8v to maintain it.

If you haven't got a good MPPT regulator it's worth changing for Votronic or Victron.
Hymers are normally fitted with Gels as standard, why on earth anyone would swap them for Banners is beyond me. Gels will give greater capacity but need a longer absorption phase to fully charge.

 

[Nasher]

It all sounds a bit over complicated and sun dependent to me - here in Wales it may rain occasionally.....


How about getting a generator?

 

[Vic. Parsons.]

It all sounds a bit over complicated and sun dependent to me - here in Wales it may rain occasionally.....


How about getting a generator?

"Here in Wales it may rain occasionally"........I've lived in Wales for 35 years and I think about 20 years worth were rainy days.......

Generators and the fuel to run them take up way too much space and load capacity, they annoy any neighbours and are IMHO a false economy, it would be cheaper to just drive somewhere to charge the batteries.

 

[Pausim]

Sounds like it would work in theory but you'd need a DC/DC charger to limit current from lithium battery and a VSR to turn on the DC/DC charger when the solar voltage to the lead batteries drops to a low level at dusk

I agree. I think a direct connection of such different battery types is likely to cause problems.

If your panels are only making (say) 20Ah per day having an extra battery of any type is not going to mysteriously add any more to it. Indeed powering a DC/DC charger is going to waste some power.

I think of my leisure battery as a bank account, if you take out more than you put in it gets shut down. An increase in the size of the battery bank is like a bigger overdraft, it puts off the day of reckoning but does not cure the problem.

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[Shrimp]

Perhaps you ought to have a battery to charge the battery to charge the battery to trickle charge the other batteries so you can keep the main batteries up!

 

[Littlewheels]

If you are £loaded and you want to load your batteries in the Grey of day or Black of night You have the option of Efoy.

Technology - How the EFOY fuel cell works

The EFOY fuel cell is the ideal power generator for your 12 V and 24 V battery. EFOY fuel cells are based on DMFC (Direct Methanol Fuel Cell) technology.

www.my-efoy.com

 

[Raul]

You are using more than your harvest, and what you see is a deficit charging. Expect some sulphation on you banners as you only tickle them instead of given them a good charging rate. You don’t need to charge 24hrs, the time is given by the rate of charge and depth of discharge, end off. If you take out 50ah and your charger is a 5a capable them makes a 10hr charge plus inefficiencies. If you would use a 20a charger then time would be reduced to 2,5hrs plus inefficiencies. Get more solar and better charge controller instead of the Li battery. What you will trying to achieve, is filling a bucket with holes from another bucket, and not safe to directly connect a Li fully charged to a discharged lead. That’s bonkers. The Li has the ability to discharge a very high current into your knackered lead , and this is only done with a battery to battery charger to be safe.

 

[Vic. Parsons.]

I didn't ask this question because I don't have enough battery power or solar power for that matter, I asked out of curiosity because this is pretty much the set up our Belgian freinds have on their brand new Hymer, with two gel batteries and one lithium.
I hadn't even considered it as a possibility, but presumably, Hymer has.

 

[Raul]

If he’s got it, doesn’t mean is right, plus we don’t know the gubbins he might have to safely charge from Li to gel, gel is even slower that flooded. You can not mix or directly connect two different chemistries without damage. It has to be a charger between them, to manage the current from Li into the other.

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[Nasher]

Generators and the fuel to run them take up way too much space and load capacity, they annoy any neighbours and are IMHO a false economy, it would be cheaper to just drive somewhere to charge the batteries.

Don't take life too seriously, no-one gets out alive - there was a smiley on the end of my post.......

 

[Pausim]

I didn't ask this question because I don't have enough battery power or solar power for that matter, I asked out of curiosity because this is pretty much the set up our Belgian freinds have on their brand new Hymer, with two gel batteries and one lithium.
I hadn't even considered it as a possibility, but presumably, Hymer has.

That Hymer set up includes a lot of sophisticated electronics which they call “integrated discharge management”. It looks quite clever, it manages charging and discharging the batteries. However it costs over £2,000 and for that money I would simply opt for two good LiFePO4 batteries.

 

[Pausim]

If you are £loaded and you want to load your batteries in the Grey of day or Black of night You have the option of Efoy.

Technology - How the EFOY fuel cell works

The EFOY fuel cell is the ideal power generator for your 12 V and 24 V battery. EFOY fuel cells are based on DMFC (Direct Methanol Fuel Cell) technology.

www.my-efoy.com

I have an Efoy and it does just that. Charges whatever the weather, day or night and wherever you are parked. Including nice shady spots. I use 40 or 50Ah per day with a single 100Ah LiFePO4 battery. The Efoy runs quietly for 8-10 hours (no solar), turns on when the battery is about 40% discharged and stops when it is full. I need reliable electricity because I have a CPAP machine that runs all night. With the Efoy I simply don’t have to worry.

The Downside is it is not a cheap option.

 

[mikebeaches]

Err-hum, would it not be easier to just pay for a mains hook-up for the night!

Otherwise, it all sounds way too complicated and expensive to me...

 

[Spriddler]

Perhaps you ought to have a battery to charge the battery to charge the battery to trickle charge the other batteries so you can keep the main batteries up!

............but I don't know why she swallowed a fly.......

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