Comparing Hymer Smart Battery System to cheaper alternatives

[paddymcc]

You don't live in the North or Scotland. I monitor and log all the data on a minute-by-minute basis and over the winter for a period of 90 days, my batteries were below 5C for 88 or 89 of those 90 days. Maybe some, or maybe most, folk don't need heaters in order to have a USABLE lithium setup, but I would, and most in this area and above would.
PREVENTING charging from cold is not the best solution. It just means all you can do is stop it charging and you just deplete the battery. With a heater you use that charging energy that in your setup you are throwing away to warm the battery to allow charging. A much better solution.
Does your battery not have an integral low-temp charge cutoff in the BMS anyway to prevent charging at low temps? Why do you have to add extra external circuitry to do that? I would avoid Lithium batteries that used a BMS that was missing such a fundamental function.

Agree Scottish and Finnish temperatures may be different. If I find it a problem I will fit a heating mat but in reality when I go away in the winter, which I do regularly, I heat up the van before I go on electric which will also heat the battery bay so it's not a problem.
My battery does come with a temp cut off in the BMS. As other people have said, it's better to have a belt and braces approach. The Votronic B2B comes with a supplied temp sensor and the warranty would be invalid if I didn't use it.

 

[Pausim]

100Ah of Lithium. 80Ah Safely Usable
300AH of Lead Carbon. 200Ah Safely Usable. (don't get sucked into the "can't go below 50%" rubbish)
Does your 320Ah LiFePO4 battery include heaters so it can be charged at low temp? does your 320Ah LiFePO4 include an Integral State of Charge Monitor?

Sorry, I thought we were discussing the Hymer Smart System. Your “superior” system is too complex for me to set up and I don’t have the spare payload for it. The Lead Carbon batteries you are using look a lot better than basic AGM ones but I see there are still issues about temperature compensation when charging. Unlike LiFePO4, Lead Acid batteries generally lose 20% plus of their output capacity in freezing conditions but I have no idea if that also applies to Lead Carbon.

If I lived as far North as you I might have to pay more attention to charging my Li battery in freezing conditions. It is never a problem for me when using my motorhome because the battery compartment is always warm. When it is in storage it gets an occasional automatic low charge but that is well within the manufacturers cold charging limits of:
1. 0°C to -10°C (32°F to 14°F) charge at 0.1C (10% of the battery capacity)
2. -10°C to -20°C (14°F to -4°F) charge at 0.05C (5% of the battery capacity)

 

[Hoovie]

Too complex? True, connecting a little black box with a cable in and a cable out can be tricky . I thought the discussion had expanded (you talked about your (non-hymer?) Lithium battery for example).
Many motorhomes have external (and unheated) battery compartments.
Also having a battery which you can charge at low temps means you have a setup where YOU decide where you go and when you go. Otherwise your touring gets limited to the places and times your batteries will let you. I much prefer a setup where the batteries don't dictate to me what is possible.

 

[The Wino]

Too complex? True, connecting a little black box with a cable in and a cable out can be tricky . I thought the discussion had expanded (you talked about your (non-hymer?) Lithium battery for example).
Many motorhomes have external (and unheated) battery compartments.
Also having a battery which you can charge at low temps means you have a setup where YOU decide where you go and when you go. Otherwise your touring gets limited to the places and times your batteries will let you. I much prefer a setup where the batteries don't dictate to me what is possible.

That's a bit like saying everyone ought to fit snow tyres even if they never use their motorhome in winter!. Different people use their motorhome in different ways if you use it all year round and a lot of electrical gear your system sounds really good but if you don't it's a waste of money and payload. We have very little electrical demand so don't need it. What suits one person won't suit another.
I'm pretty sure the Hymer system was designed at a time when lithium was really expensive and will be fairly quickly outdated. Your system sounds like it has some advantages over the Hymer system but if lithium reduce further in price I could see that too becoming too complicated. Ive not see one yet but sooner or later someone will probably come up with a fully integrated package that fits under a standard seat with a reasonable amount of lithium and a b2b maybe with other electronics included.

 

[Pausim]

Too complex? True, connecting a little black box with a cable in and a cable out can be tricky . I thought the discussion had expanded (you talked about your (non-hymer?) Lithium battery for example).
Many motorhomes have external (and unheated) battery compartments.
Also having a battery which you can charge at low temps means you have a setup where YOU decide where you go and when you go. Otherwise your touring gets limited to the places and times your batteries will let you. I much prefer a setup where the batteries don't dictate to me what is possible.

My touring has never been constrained by my batteries.

What I have in mine is a fairly clever box in the form of a microprocessor-controlled programmable relay of my own specification (I call it the 'VSDR Lithium Controller')

That doesn’t make it sound like a simple solution that is available to all and easily fitted.

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[Hoovie]

My touring has never been constrained by my batteries.

That doesn’t make it sound like a simple solution that is available to all and easily fitted.

If someone is unable to install a relay, they should not be doing any electrical work on their vehicle to start with.

 

[Raul]

Hoovie, can you elaborate on that magic box please? Is it a programmable battery combiner? I’m interested in a static installation, where lead is 7 years old, but well looked after with logs and about 80% capacity is still there. It’s just peak power delivery that slowed down. I would need 15-20kwh if I would go all Li, and at least 2 stages of protection as it can be left alone for months. If I add Li to the existing, I could get away with 7-10kwh.
I had a idea with Argo diode, but haven’t explored deeper. Thanks.

 

[Hoovie]

That's a bit like saying everyone ought to fit snow tyres even if they never use their motorhome in winter!. Different people use their motorhome in different ways if you use it all year round and a lot of electrical gear your system sounds really good but if you don't it's a waste of money and payload. We have very little electrical demand so don't need it. What suits one person won't suit another.
I'm pretty sure the Hymer system was designed at a time when lithium was really expensive and will be fairly quickly outdated. Your system sounds like it has some advantages over the Hymer system but if lithium reduce further in price I could see that too becoming too complicated. Ive not see one yet but sooner or later someone will probably come up with a fully integrated package that fits under a standard seat with a reasonable amount of lithium and a b2b maybe with other electronics included.

If they never intend to drive in cold temps ("snow tyres" are incorrectly named), then Winter Tyres are not necessary, that is correct. But IF they do, it is nice to be prepared, is it not? I have Cross-Climates on my Motorhome as for over half the year in the north and Scotland, it is below an average of about 7C (surprising, eh?). You could also save money on wipers if you never drive in the rain?

 

[Hoovie]

Hoovie, can you elaborate on that magic box please? Is it a programmable battery combiner? I’m interested in a static installation, where lead is 7 years old, but well looked after with logs and about 80% capacity is still there. It’s just peak power delivery that slowed down. I would need 15-20kwh if I would go all Li, and at least 2 stages of protection as it can be left alone for months. If I add Li to the existing, I could get away with 7-10kwh.
I had a idea with Argo diode, but haven’t explored deeper. Thanks.

it is in essence similar to a uni-directional VSR but working in the opposite manner.
I pre-programme the settings to the charge requirements of the LiFePO4 Lithium batteries but they can be reconfigured via Bluetooth if the optional BT adapter is fitted.
Like you, but in my Motorhome - so a smaller setup - I had Lead Batteries that were still very decent but wanted to explore the benefits of Lithium and after some researching, then testing and evaluation, followed by some fine tuning and added control, found that the combination of Lead and Lithium was a near-perfect setup in terms of power delivery and cost effectiveness. I then developed the VSDR concept as a fully standalone device (200A Latching Relay with +VE in, +VE out and 0V (same as any relay) connections) which requires no external control. So all you do is get your Lithium Battery/s, the VSDR and connect up and you instantly have the benefit of Lithium in a day-to-day basic, plus the backup of Lead on those occasions if you need more energy for heavy loads or your Lithium is depleted.

It is, I think, a great solution for extending the Lead life significantly as well as you end up with far fewer cycles on the Lead Batteries, instead using up the Lithium Cycles, which are so high it really doesn't matter you have done that - as by the time you have eaten into those cycles, the chances are that:
Replacement Lithiums will be way cheaper;
Some other technology a lot better has come along;
The batteries BMS has failed anyway (cheap Chinese electronics are not designed for a 10 year service life. Maybe the lithium cells will last 10 years, but will the BMSes?);
Or your need for the battery has just gone away (finished motorhoming say?).

If you do a search on "VSDR wildebus" you will find some more details.

 

[Pausim]

If someone is unable to install a relay, they should not be doing any electrical work on their vehicle to start with.

Being able to install a relay has nothing to do with it and I would prefer not to be talked down to in this way.

You describe your set up as including “a fairly clever box in the form of a microprocessor-controlled programmable relay of my own specification (I call it the 'VSDR Lithium Controller')”. This does not describe a simple relay but one you have specified and sourced specifically to your requirements, you have even given it a name. If it was an off the shelf relay that is widely available then it would not be one of your own specification.

I do not want this to turn into a slanging match. I am happy to acknowledge that your system is a clever and cost effective solution to your needs.

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[Raul]

it is in essence similar to a uni-directional VSR but working in the opposite manner.
I pre-programme the settings to the charge requirements of the LiFePO4 Lithium batteries but they can be reconfigured via Bluetooth if the optional BT adapter is fitted.
Like you, but in my Motorhome - so a smaller setup - I had Lead Batteries that were still very decent but wanted to explore the benefits of Lithium and after some researching, then testing and evaluation, followed by some fine tuning and added control, found that the combination of Lead and Lithium was a near-perfect setup in terms of power delivery and cost effectiveness. I then developed the VSDR concept as a fully standalone device (200A Latching Relay with +VE in, +VE out and 0V (same as any relay) connections) which requires no external control. So all you do is get your Lithium Battery/s, the VSDR and connect up and you instantly have the benefit of Lithium in a day-to-day basic, plus the backup of Lead on those occasions if you need more energy for heavy loads or your Lithium is depleted.

It is, I think, a great solution for extending the Lead life significantly as well as you end up with far fewer cycles on the Lead Batteries, instead using up the Lithium Cycles, which are so high it really doesn't matter you have done that - as by the time you have eaten into those cycles, the chances are that:
Replacement Lithiums will be way cheaper;
Some other technology a lot better has come along;
The batteries BMS has failed anyway (cheap Chinese electronics are not designed for a 10 year service life. Maybe the lithium cells will last 10 years, but will the BMSes?);
Or your need for the battery has just gone away (finished motorhoming say?).

If you do a search on "VSDR wildebus" you will find some more details.

Thank you for the comprehensive explanation, I had a look at wildbus, great concept, just need to source and work with something at 48v. The ones available off the shelf are 12/24v only. I will look into Argo diodes where you can program certain thresholds to combine and separate two different battery banks. They are SSR instead latching.

 

[Coolcats]

My take on this is that anything a manufacturer does will have an associated price tag travel world for example are offering a 95ah battery for £350 and a 105ah Lithium for £999.00. The first question I would have for Hymer is why did they go for the design they have and why did they not go for a full lithium set up. It would be interesting to hear the argument why they took this approach, Hymer are not daft so the answer would be an interesting one. The second point is the €2500 Euro is actually £2100. I did ask one U.K. dealer what the cost would be for the Hymer lithium set up and the cost quoted was £3500, which in my opinion was to higher price to pay so would I be happy to pay a couple of grand for the Hymer version yes I would. But it will also be interesting to see what Hymer do in the next couple of years or so with thier approach to EV and lithium power.

 

[Hoovie]

Thank you for the comprehensive explanation, I had a look at wildbus, great concept, just need to source and work with something at 48v. The ones available off the shelf are 12/24v only. I will look into Argo diodes where you can program certain thresholds to combine and separate two different battery banks. They are SSR instead latching.

SSRs would be a good way to go and very reliable. The MTBF is generally rated for over a hundred years even with frequent switching, so for the type of applications we are discussing, perfect if you can find one with sufficient current handling capabilities (the SSRs I use are relatively low current, but as I use them for 230V AC, that is ok).
Latching Relays are great as well as take no power and again very reliable, and far more so than the typical EMR relays.
12V and 24V components are pretty simple to source but 48V is certainly more tricky. I would be interested in what you can find - I have had questions regarding a 24V setup, which is not a problem, but not yet on 48V and frankly if I did have a question on that, I would have no answer or solution right now.
Only on the forum for around another 2 weeks until sub expires and not sure if PMs work with no sub, but can always be contacted via website.

 

[The Wino]

it is in essence similar to a uni-directional VSR but working in the opposite manner.
I pre-programme the settings to the charge requirements of the LiFePO4 Lithium batteries but they can be reconfigured via Bluetooth if the optional BT adapter is fitted.
Like you, but in my Motorhome - so a smaller setup - I had Lead Batteries that were still very decent but wanted to explore the benefits of Lithium and after some researching, then testing and evaluation, followed by some fine tuning and added control, found that the combination of Lead and Lithium was a near-perfect setup in terms of power delivery and cost effectiveness. I then developed the VSDR concept as a fully standalone device (200A Latching Relay with +VE in, +VE out and 0V (same as any relay) connections) which requires no external control. So all you do is get your Lithium Battery/s, the VSDR and connect up and you instantly have the benefit of Lithium in a day-to-day basic, plus the backup of Lead on those occasions if you need more energy for heavy loads or your Lithium is depleted.

It is, I think, a great solution for extending the Lead life significantly as well as you end up with far fewer cycles on the Lead Batteries, instead using up the Lithium Cycles, which are so high it really doesn't matter you have done that - as by the time you have eaten into those cycles, the chances are that:
Replacement Lithiums will be way cheaper;
Some other technology a lot better has come along;
The batteries BMS has failed anyway (cheap Chinese electronics are not designed for a 10 year service life. Maybe the lithium cells will last 10 years, but will the BMSes?);
Or your need for the battery has just gone away (finished motorhoming say?).

If you do a search on "VSDR wildebus" you will find some more details.

You said about cheap Chinese electronics I'm now wondering where your components are made!!

 

[Hoovie]

You said about cheap Chinese electronics I'm now wondering where your components are made!!

In the UK!!

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[AgeingAndrew]

If you do a search on "VSDR wildebus" you will find some more details.

Gosh, lovely and simple and so easy to fit. It makes throwing away AGMs for a full Lithium refit look like a daft idea. As it uses bog standard lifepo4 batteries together with existing AGM/LA etc, it will be pretty cheap to implement while giving the best of lifepo4 and AGM.

I hope you sell loads of them Hoovie.

 

[Hoovie]

Gosh, lovely and simple and so easy to fit. It makes throwing away AGMs for a full Lithium refit look like a daft idea. As it uses bog standard lifepo4 batteries together with existing AGM/LA etc, it will be pretty cheap to implement while giving the best of lifepo4 and AGM.

I hope you sell loads of them Hoovie.

Glad it makes sense. (I was beginning to wonder TBH ). I think Lithium Batteries are great but they are not perfect by any means and Lead still has advantages. This setup really does, IMHO, combine the benefit of both technologies.

 

[Hoovie]

Thought I would just add a little graph to show how a Hybrid system can work under a greater load ....
SOCvsLoad by David
Usually it is the Lithium providing the energy for normal (lights, TV, water pump, etc) use, and only when the Lithium gets low does the Lead join the party in a noticable way.
However, when the load gets quite high, like in the example above with the current in excess of 80A, the Lead comes in to assist. In the graph you can see the Lead SOC (State of Charge) starting to drop from its normal straight line while the current is high. and then level out again once the load has gone.
How much assistance it gives is a factor of the SOC of the Lithium and the SOC of the Lead (which overall determines the system voltage).
This load sharing is an important aspect of a Hybrid system and is actually a benefit over a 100% Lithium setup, where the load may be beyond the capability of a Lithium Battery due to the limitations of its BMS, but where a Lead Battery has no similar issues other than voltage sag. In the example above, the load was a 850W Water Heater, but it could have been the Microwave just as easily, which would have had an approx 120A current draw. 120A is beyond the capability of most LiFePO4 batteries and would cause them to fault and shut off. Even the typical 200Ah LiFePO4 battery is still only fitted with a 100A BMS.

It would be interesting to know if the Hymer Hybrid system has any quoted current draw limits? Have they taken advantage of load-sharing to allow currents in excess of the max rated current for the BMS fitted in the Lithium? A very popular addition to motorhomes seems to be these pod coffee makers and off-grid, the current draw on the battery via a suitable inverter will certainly be more than 100A.

(As an aside, my own 100Ah LiFePO4 Battery in the Hybrid system has a 150A BMS which was important while I was evaluating and monitoring how the Hybrid system would operate in 'real life' but I have never exceeded 100A from the Lithium alone while operating in a Hybrid system).

 

[paddymcc]

Alternatively buy a system with adequate BMS for the expected maximum current draw. Mine has a the ability to cope with 250A constant current draw with a peak current of 500A. I doubt if I will need it but I know that it's there if necessary..