Lithium vs Lead Acid. Some Facts !

[eddie]

I have a fly, that stung me, like a Wasp would, turned it was a wasp, but I was convinced it was a fly? My mate said he had a moth, but that would only work at night, like a butterfly vampire

Turned out it was a Dragonfly!

Things are close to, but nothing is better than Lithium Batteries.

Can’t afford them? Don’t want them? Fine! don’t buy them, but don’t try to rubbish them to justify that.

Like reading that motorhomes are crap and a waste of money on a tent forum.

 

[tonyidle]

Ok here goes....My name is Michael and I abuse batteries
On my brand new motorhome my AGMs lasted just over a year. We use the inverter a lot during the winter months - Hair Dryer etc and only BritStop hop around so batteries very rearly get their full charge. I do have 150W of Solar, but UK is only good for a little charge mid Summer. So I replace batteries like for like at much cheapness as dealer agrees, should have lasted longer, but look at the inverter!! 18 months later probably because we drove further in between stops and went abroad for better sun, batteries OK, but failed if using too much or inverter.
Call to the Bitzmeister to fit a B2b and changed to Lithium in Jan this year. Sooo happy with the change, still abuse the batteries cos I am one of those who couldn't care less, but I don't blame anyone else - Well except Jane...I dont have a monitor as I am sure the batteries will always be ok and this would probably become obsessive. The B2b takes care of the charging whilst driving short hops and Solar for when we are static and the batteries give max power for far far longer.

A little more solar would do no harm?

 

[tonyidle]

I know Jim posted earlier that mos Lithiums advise installing a B2B.

I find that hard to understand considering the better performance of those batteries. Maybe somebody can explain the logic.

As I have posted elsewhere I would certainly encourage B2B use for lead/acid, but only if one moves regularly - they are not much use for 2 weeks on a site if no EHU, unless you want to annoy the neighbours by runnng your engine.

Geoff

I suspect that as the Lithiums can handle a very high charge rate (and therefore less time to full charge) that you won't get the full benefit from a simple alternator charge. You may not, of course, need the most they can give but if you do a B2B is better than relying on the alternator alone.

 

[autorouter]

If you absolutely abused the Lithiums they would last 10.95 years ( cycled every day to 100% discharge)
If you totally molly coddled the Gels they would last 7.53 years (cycled every day to only 20% discharge

I think you missed the small print to the right of the graph:

"This chart illustrates the expected cycle life as a function of DOD to 70% of initial capacity"

The "100%" is in fact 100% of 70% DOD. In other words they never get discharged to below 30%.

It's still impressive though - over 4000 cycles at 70% DOD. Compared to Gels for the same conditions that's about 700 cycles at 70% DOD. 10.95 years is better than 1.92 years.

 

[autorouter]

Haven't got fifteen minutes to watch it so what is the result?

I think this video is very interesting, but it only addresses the one scenario of repeated fast and deep battery discharge. In that situation the Lithium wins by a mile. While this is undoubtedly a realistic scenario for some situations, especially if the user does not own the vehicle, it does not resemble much MH use.

For example, most MHs do not have an inverter, or anything that will draw a very high current. Most MH owners do not let the batteries discharge down to 30%, and many keep them above 50%. In that scenario, lead-acid 'leisure batteries' last very much longer, and are perfectly viable options for careful motorhomers with modest power demands.

But I'm sure if Lithiums were the same price as Lead-acids, we'd all be using Lithiums.

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[Gromett]

But I'm sure if Lithiums were the same price as Lead-acids, we'd all be using Lithiums.

That is the single most accurate statement so far. The ONLY disadvantage of Lithium batteries is their "up front" cost. TCO is a different matter altogether.
In every other specification and requirement LiFePO4 cells beat Pb by a massive amount.

 

[HandyAndy]

I think you missed the small print to the right of the graph:

"This chart illustrates the expected cycle life as a function of DOD to 70% of initial capacity"

The "100%" is in fact 100% of 70% DOD. In other words they never get discharged to below 30%.

It's still impressive though - over 4000 cycles at 70% DOD. Compared to Gels for the same conditions that's about 700 cycles at 70% DOD. 10.95 years is better than 1.92 years.

70% wording is the capacity left of the battery after 100% discharge for however many cycles.
Not how far they discharge it in each cycle.

 

[autorouter]

I think you missed the small print to the right of the graph:

"This chart illustrates the expected cycle life as a function of DOD to 70% of initial capacity"

The "100%" is in fact 100% of 70% DOD. In other words they never get discharged to below 30%.

70% wording is the capacity left of the battery after 100% discharge for however many cycles.
Not how far they discharge it in each cycle.

Yes you're right. They repeatedly discharge the battery at different percentage discharges until the capacity falls to 70% of what it was originally.

That 100% DOD point is unbelievably good. They presumably wouldn't put it on the graph unless they had actually done the discharges. The Gel graph only goes down to 80%.

 

[funflair]

Yes you're right. They repeatedly discharge the battery at different percentage discharges until the capacity falls to 70% of what it was originally.

That 100% DOD point is unbelievably good. They presumably wouldn't put it on the graph unless they had actually done the discharges. The Gel graph only goes down to 80%.

With a lithium battery doesn't 100% DOD just mean discharged to the level that the BMS cuts off ? if Gel had a similar protection system 100% DOD would be quoted.

Martin

 

[Steve and Denise]

Well I think if my 2 X 160 Gels die after reading all off the info on here I would definitely go down the route of 4 X 84ah Lithiums as I have 2 chargers fitted and according to the info I have been told the Schaudt charger on the van has a suitable charge voltage ie higher than the alternator, similar to a B2B.

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[Pausim]

There often seems to be confusion between the different types of lithium batteries, particularly concerning safety. If you are confused or interested the LiFePO4 Battery Safety video here

Tech Videos | All About Lithium Batteries | RELiON

Answers to some of the most common technical related questions about lithium battery from RELiON Battery.

relionbattery.com

may be of interest. It is obviously partly aimed at promoting the product but I found some useful information in it.

 

[HandyAndy]

With a lithium battery doesn't 100% DOD just mean discharged to the level that the BMS cuts off ? if Gel had a similar protection system 100% DOD would be quoted.

Martin

100% discharge is "around"
3.6 volts per cell Full
2.5 volts per cell Flat

or in 12v terms that equates to
14.4volts Full
10 volts Flat

The absolute limit numbers are usually slightly above and below that for BMS cut off
3.8 volts high limit (overcharge disconnect)
2.1 volts low limit (Low voltage threshold)

lower than 2 volts would damage the cell beyond use
Higher than 4.2 volts per cell would damage it but it remains "saveable" to a certain extent.

 

[Sid52]

How come my 3 year old lithium phone battery is knackered then? I never let it go lower than about 30%
Also my ipod touch 5 hardly lasts an hour off it's charger nowadays ?

I thought that with my 6 year old phone. However once I'd checked that everything had been copied to the new phone I restored the old phone to factory settings. Guess what, with a few apps reinstalled and recharged the phone kept its charge for days. It was all the accumulated crap over 6 years that was draining the battery.

 

[Hercs74]

I have read this thread with great interest. I am very new to MH world having only recently bought a Bürstner. I currently have a Varta LA95 95Ah Professional Dual Purpose AGM leisure battery, soon to have a second added (FOC by dealer). I also have a 100w roof mounted solar panel. As far as I am concerned and can tell all works fine. I am going to check the leisure battery voltage next week as the vehicle has been parked up in storage for 23 days. I’ll be interested to see its voltage. What I’d like to know is thoughts on my set up. Is the solar panel suitable enough? The leisure batteries adequate? What is the science behind and relating too solar panel wattage and charging in relation to the varying Ah battery sizes.

Thanks

 

[two]

I have read this thread with great interest. I am very new to MH world having only recently bought a Bürstner. I currently have a Varta LA95 95Ah Professional Dual Purpose AGM leisure battery, soon to have a second added (FOC by dealer). I also have a 100w roof mounted solar panel. As far as I am concerned and can tell all works fine. I am going to check the leisure battery voltage next week as the vehicle has been parked up in storage for 23 days. I’ll be interested to see its voltage. What I’d like to know is thoughts on my set up. Is the solar panel suitable enough? The leisure batteries adequate? What is the science behind and relating too solar panel wattage and charging in relation to the varying Ah battery sizes.

Thanks

It's as long as a piece of string.
Required battery capacity will depend on how much you use before you are able to recharge (by solar, EHU, or driving).
Solar input will depend on weather, shading and your location.
Vehicle charging (whilst running the engine) will depend on how long you drive for.
So there are far too many variables to be sure. It's best you see how you go and learn from experience.

If we thought about fuel tank size, most of us could have got by with a smaller one (assuming none of us have ever run dry) but how much smaller? We may manage on a tank half the size but that would require closer management.

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[Lenny HB]

Ditch the AGM and fit a couple of Gel batteries much more reliable, that's what I did (actually fitted 3 Gels).
100 watts of solar is fine for keeping the batteries topped but if you intend to do off grid camping you need 300 - 400 watts but even that is nowhere enough for using in the winter in the UK.

 

[Hercs74]

So could someone explain the workings. I appreciate there are many variables. But more interested in the basic theory calculations around the battery Ah and relevance of solar wattage. I would like to learn and understand. Thanks

 

[two]

We assume a 12V system, then measure power in terms of how long (hr) current (A) is drawn for. If you were to install an "Amp counter" that would do the arithmetic for you and also indicate the amount of power left in your batteries.
If you use theory, you need to decide how long you use everything electrical each day and what current it draws (very tedious).
Whatever you use over a period will have to be put back.
Solar is attractive because it's free. But it's also unpredictable and weakens as you go North.

 

[autorouter]

What is the science behind and relating too solar panel wattage and charging in relation to the varying Ah battery sizes.

The science is about how much energy you use, and how you generate and store that energy. All these quantities are hugely variable from person to person, rain or shine, summer or winter.

In summer, some people only use electricity for the water heater and fridge controls, water pump and phone charger. A 100 watt panel will do all that easily. In winter, on some dark days even the 4000 watts on my house roof hardly gives enough to charge a phone.

The battery is an energy store for the time there's no energy generated. Overnight, through a bout of cloudy days, or between sites with hookup. The engine alternator, maybe boosted by a B2B charger, can charge up the batteries if you are driving a couple of hours or more.

You will always have to control and manage your energy use in a motorhome, even on a site with hookup. Whole books have been written on the subject. If you're interested, here's one:

https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf

 

[DBK]

So could someone explain the workings. I appreciate there are many variables. But more interested in the basic theory calculations around the battery Ah and relevance of solar wattage. I would like to learn and understand. Thanks

Edit: Autorouter types faster than me but here's my three pennyworth....


There isn't really any science involved other than resolving the three factors involved:

Storage capacity
Usage
Generating capacity

All three can be measured in Ah or amps used per hour. By generating capacity I mean whatever is used to recharge the batteries be that from solar, running the engine (going for a drive ) EHU, generator or even fuel cell.

There is no rule which says for every X Ah of batteries you need Y watts of solar.

If your usage is very low a single small battery and solar panel might be all you need, and if you move on every day you may not even need the solar panel. Don't forget it wasn't so long ago virtually no one had solar and probably only had a single battery.

The thing to draw from the above is what solar and batteries you need are almost entirely decided by your power usage. I say "almost entirely" because even if you don't need solar when touring there is a good case for having at least one panel so the batteries can be kept topped up when the vehicle is not being used.

In your case, I suggest with two batteries and 100W of solar just see how you get on. Just a few years ago this was the setup folk aspired to. You may find you have sufficient or decide to add more solar, or as I did, a battery to battery charger.

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[Lenny HB]

So could someone explain the workings. I appreciate there are many variables. But more interested in the basic theory calculations around the battery Ah and relevance of solar wattage. I would like to learn and understand. Thanks

Really depends on your usage and the time of year and country you are in so not a straightforward answer.
An ordinary flooded battery should not be taken down below 50% DOD (Depth of Discharge) to preserve their life, Gels can be taken down to 80% and Lithium down to almost zero but 5% is the norm.

As an example in October we use around 30 a/h a day in the UK our 300 watts of solar if it's a bright sunny day will put back in around 20 a/h but the slightest bit of cloud the output falls off. If it's raining all day may only get a few a/h from the solar.

Although a 100 watt panel can produce around 25-30 a/h a day in the this would only be in mid June with a perfectly clear sunny day. With a flat roof mounted panel you only get the full output for 2 or 3 hours around midday in June, as the sun's angle changes the output rapidly falls.

A basic PWM solar regulators are OK for summer use but a good quality MPPT regulator with give a lot more power on dull days and well worth the expense if you are using your van outside the summer months.

 

[autorouter]

If you have enough solar to cope with dull days and spring/autumn, you will probably have too much in the height of summer. A good MPPT controller will act as a multistage smart charger, and avoid overcharging the batteries. Any energy not required is simply wasted, converted to heat. Some of the better controllers have an extra output that can power an AES fridge with the excess solar power.

 

[Lenny HB]

Some of the better controllers have an extra output that can power an AES fridge with the excess solar power.

It doesn't actually power it from the solar it switches the fridge to 12v. I have a Votronic controller set to switch the fridge, found I had to fit a mains powered relay to switch it off when on EHU, due to the stupid Dometic firmware that kept the fridge on 12v when on EHU.

 

[Richard n Ann]

Any energy not required is simply wasted, converted to heat

What? Any energy not required is simply not used. I must be reading this wrong ?

 

[DBK]

If you have enough solar to cope with dull days and spring/autumn, you will probably have too much in the height of summer. A good MPPT controller will act as a multistage smart charger, and avoid overcharging the batteries. Any energy not required is simply wasted, converted to heat. Some of the better controllers have an extra output that can power an AES fridge with the excess solar power.

That's a bit misleading. A charger doesn't "waste" energy, it just stops it being generated in the first place if it isn't needed. In the case of an MPPT controller it let's the panel voltage rise so power is reduced. Other types of controller effectively disconnect the panel so it produces no power. Either crudely like a shunt controller or many times a second with a PWM controller.

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[tonyidle]

If you have enough solar to cope with dull days and spring/autumn, you will probably have too much in the height of summer. A good MPPT controller will act as a multistage smart charger, and avoid overcharging the batteries. Any energy not required is simply wasted, converted to heat. Some of the better controllers have an extra output that can power an AES fridge with the excess solar power.

Most solar controllers are smart enough not to over-charge. The better (MPPT) controllers are multi-stage and ensure that the battery is fully charged. Once it is then excess power from the panel goes nowhere and definitely isn't converted to heat. Heat is produced to a limited extent when there's good solar output and the batteries (or hab systems) are drawing a heavy current.

 

[tonyidle]

That's a bit misleading. A charger doesn't "waste" energy, it just stops it being generated in the first place if it isn't needed. In the case of an MPPT controller it let's the panel voltage rise so power is reduced. Other types of controller effectively disconnect the panel so it produces no power. Either crudely like a shunt controller or many times a second with a PWM controller.

Not like a shunt controller. That type short-circuits the supply to regulate and isn't seen anywhere other than on permanent magnet alternators. The old analogue controllers used series regulation.(and they did get hot!).

 

[autorouter]

That's a bit misleading. A charger doesn't "waste" energy, it just stops it being generated in the first place if it isn't needed.

Yes, I meant to say that there's no need to worry about having too much solar panel wattage. The controller won't overcharge the batteries. The unused energy is converted to heat in the solar panel, in the same way that solar energy is converted to heat in a metal roof or anything else.

 

[SteveJulesMontycame2]

This thread has been a real education. But it raises a host of questions for me about what we need to fit in our van to change to Lithium. Perhaps some on here with technical knowledge/ experience would be able to make suggestions or advise the best way forward. I'm thinking the first thing we need is a B2B to get more charge into the batteries when driving, Lithium batteries to increase the useable capacity and a new mains charger to cope with the demand of the Lithiums when on hook up.

We have a 2017 Adria Matrix (semi integrated) on Fiat Ducato chassis with Euro 6 150bhp, 2.3 litre engine. The van is fitted with 2 x 80Ah AGM habitation batteries (now 2 years old) and the standard factory fitted (engine) charging system. A Nordelettronica NE237 sits in the battery box for mains charging. According to the handbook, this only puts 18A out, without a Lithium profile. We have 2 solar panels fitted, with a Votronic MPPT 350w charge controller. We have been electrically self sufficient whilst living off grid to date. We also have a 1200w Votronic inverter. It is only now, we have had a few overcast days and the AGMs have run down to 75% a couple of times.

Votronic market the VBCS 12V triple charger that includes B2B, mains charger and a solar controller, one device in place of three. One with a 30A B2B but the mid range one with 45A B2B would appear to maximise the B2B output under 50A for Lithium.

Questions I have are;
Q1: Are Lithiums the standard battery dimensions? Will I be able to fit 2 x 100 Ah Lithiums in the space?
Q2: How much power can we take from the alternator for the B2B? Will the van alternator power the 45A B2B? Or would the 30A be sufficient? The van is Euro 6, but earlier I read Fiat does not fit smart alternators to Moho chassis. Is this an issue?
Q3: What brand of Lithium? Earlier someone suggests the BMS are not all the same quality and there is a lack of common build standards. There also would appear to be a wide range of prices at the moment from Battery Mega Store to Relion to Sterling. Is it buy cheap, buy twice? What is it about the expensive ones that makes them any better?

Sorry for the long question, trying to sort this out in my mind as much as on the van!

 

[HandyAndy]

Generally the lithium takes up a smaller profile than the equivalent lead acid but not by a great deal.

as long as the engine rpm is elevated (driving) then the alternator canprobably do upwards of 100 amps without issue but I would, for peace of minds sake fit a temperature probe on it and either a display to manually watch the temps or a B2B that can dial things back using temp input.

Brand wise, I'm not going to stray away from victron when I do mine.
Newer chemistry developments have a greater watt pr kilogram ratio so you'll get better performance and better overall capacity with the newer stuff (read that as the larger manufacturers will be quicker out of the gate with latest tech, take from that what you will about the price point.

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