Leisure battery goosed ?

[Marauder]

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So whats the use of a chocolate fire guard - or a battery that only works in summer ?

My MH trips are mainly to Scotland in Spring and Autumn - it's frequently below 0-5c temp range

Are Gel any better ? What's their story ?

There seem to be problems with every brainwave I get . . . . . .
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[autorouter]

How is charge time calculated?

is it 200ah / 20a = 10hours ?

That's basically how it's done. If you take 100Ah out of a battery bank, you would expect that you could recharge it by putting 100Ah back in.

For LiFePO4 batteries, that's about how it works, for 100Ah taken out you need to put back about 105Ah, because some charge is lost due to inefficiencies.

Lead-acid type batteries (flooded, sealed, AGM, Gel) are much less efficient. If you take out 100Ah you need to put back about 120Ah, because the charging process of this battery chemistry is quite inefficient.

 

[Marauder]

Ok
Thanks
But Lenny says LiFePO4 will work at low temps, but not accept a charge if cold.

the Polarmax seem to have heater element in base to overcome this. But if I'm in dodgy Scottish weak sun at less than 5c trying to charge from solar, I'm guessing much of the solar charge would go to heating the LiFePO4 before actually charging it ?

But would it be as much as the 20% overcharge for LA types you mention above ?

If Lithium max charge = C/2 - LA&AGM = C/5
what is rate for Gel batts

Maybe Gel is better option for me ?
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[autorouter]

C/5 is a general rule of thumb, for more detail you'd have to look at the specific manufacturer's data sheet. But Gels are generally less tolerant of fast charging and discharging than the other types. Fast charge/discharge creates heat. The space between the battery electrodes is filled with a gel rather than a liquid, so it doesn't transfer heat as well as a liquid.

In terms of energy, the overcharge is worse than 20%, more like 30%, because charging voltage is about 14.5V but the discharging voltage is more like 12.5V.

I don't know enough about the batteries or the heater elements to tell how much heat it takes to keep them above zero. In principle it's quite easy to calculate. You'd have to know the 'thermal mass' of the battery, ie the energy required to heat the whole battery by 1 degree C. Then if you knew the heater wattage, you could calculate how much energy it would take to get them from say -5C to +2C, and how long it would take to do that. Also I think it's common to put the batteries inside the MH, within the winter protection shell,so they are less exposed to cold.

 

[peterc10]

Winter trips will be no problem for our lithiums. Our batteries are inside the motorhome which will always be warm when we are using it.

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[Lenny HB]

So whats the use of a chocolate fire guard - or a battery that only works in summer ?

My MH trips are mainly to Scotland in Spring and Autumn - it's frequently below 0-5c temp range

You must like it cold we like our van aroud 22° regardless of outside temp so not a problem for the batteries.

Are Gel any better ? What's their story ?

As autorouter says they take longer to charge (need a long absorbtion phase) and not keen on high discharge currents.
But they are very reliable and often last over 10 years.

I have 3 x 78 ah Gels two are 6 years old & one 5 years old all still performing like new apart from age related small loss of capacity.

 

[Shrimp]

Our lead acid batts packed up, we can’t afford Lithium so got two used but fairly new Gel batts, that are far better than the lead acid ones, really pleased with them.

 

[Marauder]

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Aaargghhh

It's just like a nightmare

except i'm still awake

and it really is happening
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[h1ghway1]

I found a YouTube video explaining the Hymer panel..and the strange thing is the volts drop on battery 1... which is the starter battery ..
anyway I'm getting a professional to investigate next week.. thanks for all the input

 

[Marauder]

I have 3 x 78 ah Gels

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Thanks Lenny

So 3x78/5=46.8 What is amps of your EHU charger ?

Why did you go for relatively small 78ah when 100ah seems the norm ?

I see your point about temp inside van. But I only put heating on when I need it, to conserve Hab Batt power.

So heater is off overnight when I'm in sleeping bag ( I open the fridge door at night to get it cold & close it in morning ! )

What would happen to Lithium if warm charging in evening, and temp drops (to 0c) overnight whilst on EHU for eg - or even on solar ?
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[Marauder]

new Gel batts, that are far better than the lead acid ones

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what makes them better, in your experience ?
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[Lenny HB]

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Thanks Lenny

So 3x78/5=46.8 What is amps of your EHU charger ?

Why did you go for relatively small 78ah when 100ah seems the norm ?

I see your point about temp inside van. But I only put heating on when I need it, to conserve Hab Batt power.

So heater is off overnight when I'm in sleeping bag ( I open the fridge door at night to get it cold & close it in morning ! )

What would happen to Lithium if warm charging in evening, and temp drops (to 0c) overnight whilst on EHU for eg - or even on solar ?
.
_

The standard gel battery is 80 ah, Exide GS 900, the Sonnenschine is 78 ah almost identical battery both made in the Sonnenschine factory. 80 ah Gel has more avaliable power than a 100 wet lead acid.

I just have the standard 18 amp EBL but my batteries are hardly ever changed via EHU my 300 Watts of solar takes care of charging.

We never use heating at night van never drops below 15 ° unless we are very high up in the mountains.

 

[Shrimp]

Gels work better than the leads for us, they last better and seem to charge quicker.
I’m not up on the tech side of it all but they seem to give us more power from our solar!

 

[Lenny HB]

they last better and seem to charge quicker.

You are probably thinking they are charging quicker because you think they are fully charged when your monitor says 100%. But with gels when they reach the charged voltage they are only 80% charged and need another 4 to 8 hours to reach a full charge.

 

[Marauder]

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So I think forget the Lithium for me. Far north of Scotland is almost the arctic circle - van interior frequently below zero in mornings.

So now Gel seems to be best option/ compromise ( for at least the next 2 or 3 minutes )

If I'm calculating charger size, for 200ah bank of Gel, do I assume C/5 ( =40a charger) - would Gels be happy with that, or is it too much charge ?
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[autorouter]

Usually the charge rate isn't so important, especially for a mains charger when on hookup. It's usually connected for many hours, overnight for example, and has plenty of time to completely fill the batteries, even if it's only a 20A charger. It might become important if you were running a generator and had to minimise the running time, so you might want a 40A charager in that situation.

Solar isn't usually a problem either. You'd be lucky to get 40A from anything less than 500W of solar panels, even in summer.

The B2B is a different matter. You are probably trying to fill up the batteries as fast as possible, to minimise the driving time. Some combination of fast charging from a B2B to about 80%, followed by a slow charge for several hours from solar to finish the charging, would be the ideal method.

 

[ChrisL]

So now Gel seems to be best option/ compromise ( for at least the next 2 or 3 minutes )

Have a look at lead carbon gel, they may be what you're looking for, i had three of these fitted about a year a go, no issues so far, note there are many lead carbon agm batteries around so make sure that if you decide to go for lead carbon you don't buy the agm ones by mistake.

12V 110AH Expedition Plus Lead Carbon Gel Ultra Deep Cycle Battery (EXP12-110C) - Alpha Batteries

Ultra Deep Cycle Lead Carbon GEL Battery

www.alpha-batteries.co.uk

 

[Marauder]

You are probably thinking they are charging quicker because you think they are fully charged when your monitor says 100%. But with gels when they reach the charged voltage they are only 80% charged and need another 4 to 8 hours to reach a full charge.

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So how do you tell when they ARE fully charged ?
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[Lenny HB]

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So how do you tell when they ARE fully charged ?
.

Educated guess unless you have a good battery monitor.

 

[Tombola]

What would happen to Lithium if warm charging in evening, and temp drops (to 0c) overnight whilst on EHU for eg - or even on solar ?

if they have low temp cut off they will stop charging at around 2 deg, but will still be able to operate for usage (i.e. heat mat)

If you like it that cold, and dont use gas Id save my money and get a tent in my car boot or sleep with the battery to keep it warm

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[Marauder]

Usually the charge rate isn't so important, especially for a mains charger when on hookup. It's usually connected for many hours, overnight for example, and has plenty of time to completely fill the batteries, even if it's only a 20A charger. It might become important if you were running a generator and had to minimise the running time, so you might want a 40A charager in that situation.

Solar isn't usually a problem either. You'd be lucky to get 40A from anything less than 500W of solar panels, even in summer.

The B2B is a different matter. You are probably trying to fill up the batteries as fast as possible, to minimise the driving time. Some combination of fast charging from a B2B to about 80%, followed by a slow charge for several hours from solar to finish the charging, would be the ideal method.

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Overnight is fine, as Batts wont be zero charge (200/20=10hrs). ( What's lowest SOC for Gel to avoid damage ? Lenny says it's 12.5 for LA)

But 240v 1Kw gennie only 4amps output ? so 110ah (2x100ah@50%SOC) / 4a charge = 27.5hrs ?
Thus 40a charger makes no difference till gennie outputs 10Kw ?

So for B2B situation, the C/5 calc is not relevant ? How do I decide what size B2B ?
After the B2B charge to 80%, it will probably be dark nighttime after the drive, so no solar.


Thanks Lenny & ARouter et. al. for your input, I am starting to get my head around it - and it's only taken a year to grasp the basics . . . .
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[Marauder]

if they have low temp cut off they will stop charging at around 2 deg, but will still be able to operate for usage (i.e. heat mat)

If you like it that cold, and dont use gas Id save my money and get a tent in my car boot or sleep with the battery to keep it warm

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So are you saying that when lithium get cold, they use up power to heat themselves ? How much power ?

Don't particularly LIKE it, just comes with the territory. And actually, the reason all my battery research began, is that batteries don't keep the heater going long enough for even minimal use before they expire !
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[Tombola]

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So are you saying that when lithium get cold, they use up power to heat themselves ? How much power ?

Don't particularly LIKE it, just comes with the territory. And actually, the reason all my battery research began, is that batteries don't keep the heater going long enough for even minimal use before they expire !
.

yeah Ive got every praise for you in those temps, dont mind a but of cold me self tbh. but if you've got it use it is my thinking.

SO....im not sure on what ones use what current, but I know they do self heating lithiums now like the renogy one. Will still use some current but dont know how much.
also watch out for the operatong temps, some will cut off normal usage at lower temp than others.
I see Two on Tour uses one here https://www.motorhomefun.co.uk/foru...pad-for-lithium-350x260x175-w-x-h-x-d.248938/

batteries and heaters dont mix well, you want gas or diesel for heatng really. I have done it in the past with my 400ah, but nah

 

[ChrisL]

The Gel batteries I linked to can be charged down to -20 C, max charging current = 20 amps per battery and I have a Victron Smart 30 amp B2B charger, I seem to use around 40 amps from the batteries over the course of an afternoon and evening and the batteries are topped back up to 100% after about 3 - 4 hours driving, I have around 300 watts of solar as well.

 

[KimSteve]

Im in a 1999 Hymer B584 with a 100w solar panel and a battery manager.

My batteries are at least 6 years old and lead/acid wet.

I'm currently traveling around North Yorkshire and normally find a site with EHU.

I'm off grid last 2 nights and as the weather has been great not using much electric , just a low wattage LED in van .

After about 30 minutes usage I noticed the Battery Alarm flashing on the Hymer Panel 104 above the rear door.

I find one reporting above 12 volts and the 2nd reporting just over 10... this happened last night as well but by morning battery levels where back to just under 14v on both so I'm thinking the solar panel
has topped up and the alarm was quenched.

I'm thinking this indicates a knackered battery... I'm thinking I will need to replace the leisure batteries.

I'm not technical and don't have any practical skills , but what does the forum think ?

What you might want to try is a CTek charger which will offer the battery a conditioning cycle which can repair in some cases.

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[autorouter]

But 240v 1Kw gennie only 4amps output ? so 110ah (2x100ah@50%SOC) / 4a charge = 27.5hrs ?
Thus 40a charger makes no difference till gennie outputs 10Kw ?

At 240V, each amp carries 240/12 = 20 times more energy than an amp at 12V. That's more or less what voltage means.

So 4 amps at 240V is 4 x 240 = 960W. A 40A 12V charger would use 40 x 12 = 480W, which is well within the capacity of a 1kW generator, it would only be running at half its power output.

So at 40A, to output 110Ah would take 110/40 = 2.75 hours. That's in theory, in reality it would probably take about 3.5 hours.

 

[autorouter]

So how do you tell when they ARE fully charged ?

If it's a mains charger the voltage will drop from the absorption voltage (about 14,5V) to the float voltage (about 13.5V) when the charger decides the battery is full. Mains chargers have the advantage that their supply side is constant and unlimited. With solar or B2B there's the added complication that the input supply might drop off, when the engine stops or the sun goes down, before the battery is full. It will more or less resume charging where it left off when the supply comes on again.

 

[autorouter]

So are you saying that when lithium get cold, they use up power to heat themselves ? How much power ?

Lithium batteries can be used to supply power when they are below zero degrees, down to about -20 degrees. The problem is you shouldn't charge them when below zero.

So if you have a possible charging supply, but the batteries are too cold, you have two choices. You can either wait for the weather to change and the batteries to warm up above zero, or you can put a heat mat under them, and feed this charging power to the heat mat until the batteries are warm enough to charge again.

 

[h1ghway1]

Got it sorted today at Battery Solutions in York.
The owner Jon did a great job in about an hour.. starter battery ok..both Leisure batteries failed..seats out and new batteries fitted and on my way.
I would highly recommend this guy, Russ , thanks

 

[Peregrinator]

Im in a 1999 Hymer B584 with a 100w solar panel and a battery manager.

My batteries are at least 6 years old and lead/acid wet.

I'm currently traveling around North Yorkshire and normally find a site with EHU.

I'm off grid last 2 nights and as the weather has been great not using much electric , just a low wattage LED in van .

After about 30 minutes usage I noticed the Battery Alarm flashing on the Hymer Panel 104 above the rear door.

I find one reporting above 12 volts and the 2nd reporting just over 10... this happened last night as well but by morning battery levels where back to just under 14v on both so I'm thinking the solar panel
has topped up and the alarm was quenched.

I'm thinking this indicates a knackered battery... I'm thinking I will need to replace the leisure batteries.

I'm not technical and don't have any practical skills , but what does the forum think ?

It's obvious one of your batteries have gone, depending how long, it would bring the other one down too, so both need replacing, you can get cheap deep cycle batteries, and that's what you need, stay away from normal lead acid, they are no good for what you need, Shops like Halfords sale so called leisure batteries, but most are not (just normal car batteries) make sure it actually says deep cycle battery on the label, then check the date on the label too, anything over one year leave well alone, and when comparing Batteries, do not take any notice of NCC reports, they are fake, NCC do not test Batteries, they take the reports from independents but mostly from the Battery manufacturer themselves, Believe it or not, the NCC are sponsored by the Battery manufacturers. There seems a lot people try to hang on for as long as possible on their faulty batteries, it's ok as long as they have not gone too far i.e. not bulging at the sides, so please check them, and if they are even slightly bulging, get rid of them right away, because they are ripe to explode.

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