Choosing Between a Single Large Lithium Battery or Two Smaller Ones

[dawsey]

I also spoke to Roamer and KS Energy. Roamer guy told me I needed to place pretty much all of the electronics in my motorhome to use a lithium battery which sent me off speaking to motorhome installers who were utterly confused with what I was wanting doing so I had mostly given up but then I spoke to KS energy and they said their battery would work just fine with the equipment I had and I installed it and so far it has been absolutely amazing. I basically swapped out my old battery for the LS Energy battery and now we are drowning in power and I can run a 3kw inverter Very happy.

Be very wary of overloading the alternator, and/or blowing the fuses or maybe the Electoblock due to overload (if not using a B2B). Unlike Lead Acid, Lithiums have low internal resistance and will take whatever the alternator can supply. Lithium batteries would likely also not take well to long journeys where they reach full charge and are then held at the 14.4V of the alternator as opposed to their float voltage, it may well seriously damage them in the medium to longer term, and will almost certainly reduce their life.

Charging lithiums via the old split charge relay system is going to, sooner or later, compromise the Alternator and its wiring, the elektrobkock and the batteries. One or all will fail early.

The safe solution for older campers is to charge the lithiums via a B2B connected between the starter and the leisure batteries, and use a 50A ideal diode to discharge the leisure batteries via the normal 12V control block (eg the Electroblok). EHU won’t charge the lithiums, but it doesn’t need to.

 

[Pedro Pallent]

The only thing to be wary of is overloading the alternator, and/or blowing the fuses or maybe the Electoblock due to overload if not using a B2B. Unlike Lead Acid, Lithiums have low internal resistance and will take whatever the alternator can supply.

Got advised that new chassis’s don’t need a B2B as the alternator regulator is a smart thing

 

[Niall B]

I also spoke to Roamer and KS Energy. Roamer guy told me I needed to place pretty much all of the electronics in my motorhome to use a lithium battery which sent me off speaking to motorhome installers who were utterly confused with what I was wanting doing so I had mostly given up but then I spoke to KS energy and they said their battery would work just fine with the equipment I had and I installed it and so far it has been absolutely amazing. I basically swapped out my old battery for the LS Energy battery and now we are drowning in power and I can run a 3kw inverter Very happy.

I had a similar positive experience with KS Energy.

 

[Pedro Pallent]

I had a similar positive experience with KS Energy.

Me too, it’s who I bought my battery from, arrived next day. Been excellent since

 

[JockandRita]

I have to say, I think I'd be drawn on the 2 x separate 12v Lithium batteries myself as opposed to 1 x large one, as I already have a setup to isolate my 2 x banks of 2 x 90A SLAs from each other.

Cheers,

Jock.

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[dawsey]

Got advised that new chassis’s don’t need a B2B as the alternator regulator is a smart thing

I am only referring to the older stuff.

 

[Lenny HB]

Got advised that new chassis’s don’t need a B2B as the alternator regulator is a smart thing

Only if the converter has fitted a B2B otherwise the leisure battery won't get anything like enough charge into it. Not all converters fit a B2B as standard.

 

[Garry - June]

I have been running 2x KS Energy 155ah Lithium's since last summer... i researched all the blurb on their website and went with them because the charge parameters are ideal for my EBL as they state... so despite a lot of folk saying you cannot do it for me it has been just a simple drop in replacement for my old 300a of lead acids.. I charge them directly from 430w of roof solar through a Votronic MPPT.. and if required a further 300w of portable rigid suitcase panels though another totally separate Votronic controller... i regard the on board original charger as just a back up... I have not fitted or felt the need to fit a B2B charger... the reasons i fitted two batteries is as others have stated... the size for the place i installed them, and also the output current when used with my 3000w inverter.. and I agree if something should malfunction with one whilst travelling abroad then i could simply remove and continue on one battery alone... I monitor them through Bluetooth app and can monitor each individual cell so you can see exactly what's going on.. We fulltime in our van and just to add, by far the biggest improvement to the whole van has been switching out the old 3 way fridge freezer for a compressor model... the difference in power consumption has really been eye opening..

 

[dawsey]

Charging via solar is all fine in summer, but if you used your van in the depths of winter your solar wouldn’t be enough (I have 600W, not enough). In which case you’d have to charge from the alternator.

 

[stuartforrest]

I have been running 2x KS Energy 155ah Lithium's since last summer... i researched all the blurb on their website and went with them because the charge parameters are ideal for my EBL as they state... so despite a lot of folk saying you cannot do it for me it has been just a simple drop in replacement for my old 300a of lead acids.. I charge them directly from 430w of roof solar through a Votronic MPPT.. and if required a further 300w of portable rigid suitcase panels though another totally separate Votronic controller... i regard the on board original charger as just a back up... I have not fitted or felt the need to fit a B2B charger... the reasons i fitted two batteries is as others have stated... the size for the place i installed them, and also the output current when used with my 3000w inverter.. and I agree if something should malfunction with one whilst travelling abroad then i could simply remove and continue on one battery alone... I monitor them through Bluetooth app and can monitor each individual cell so you can see exactly what's going on.. We fulltime in our van and just to add, by far the biggest improvement to the whole van has been switching out the old 3 way fridge freezer for a compressor model... the difference in power consumption has really been eye opening..

I know its off topic but which compressor fridge did you switch to. Can you run the fridge off the batteries. Our 3 way fridge is garbage whereas the fridges on our boat run off batteries just fine so long as we start our generator or engines every few days when its not so sunnny.

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[autorouter]

Got advised that new chassis’s don’t need a B2B as the alternator regulator is a smart thing

Don't know who would give advice like that. The whole point of a smart alternator is that it doesn't charge the starter battery during normal driving and cruising. It waits until you lift off the accelerator or actively apply the brakes to turn on and send charge to the battery. The idea is that it is using otherwise wasted energy by loading the engine only when it's not trying to increase or maintain speed.

In order to do this, there must be space left in the battery, so it mostly keeps the starter battery at less than full, typically 60% or so. If you connect your leisure battery in parallel with a split charge relay, it will get exactly the same treatment. Is that what you want?

A B2B takes power from the alternator in the same way that other things like lights, fans etc do. It takes power into a proper multistage smart charger which converts it into the voltage and amps that the battery needs. It's a good idea with standard alternators, and essential with smart alternators. Also a good idea with lithium batteries anyway.

 

[Kerrone]

Looked into having lithium fitted to our 2012 Dethleff Esprit but the cost has put me off

 

[BOWHOUSE52]

As in the title, whats the thinking on Lithium batteries, is it better to have one large one or 2 smaller ones? My thinking is if you only have one and it goes boobies up your stuffed and if you have 2 the duff one can be isolated from the bank. Or are they that reliable that one would be ok?

Very true just done mine 2x100 amp not tried them yet but so much lighter

 

[TrudeandDall]

I also spoke to Roamer and KS Energy. Roamer guy told me I needed to place pretty much all of the electronics in my motorhome to use a lithium battery which sent me off speaking to motorhome installers who were utterly confused with what I was wanting doing so I had mostly given up but then I spoke to KS energy and they said their battery would work just fine with the equipment I had and I installed it and so far it has been absolutely amazing. I basically swapped out my old battery for the LS Energy battery and now we are drowning in power and I can run a 3kw inverter Very happy.

I spoke with Roamer too. The tech guy initially told me that because their batteries require a 14.2v charge and my lithium settings on the B2B were 14.4v (which seems to be a pretty universal Lithium setting) then I should change my B2B. Also as the nearest that I could get (the Gel setting) on my EHU charger was also 14.4v then it would have to be changed too. KS and all of the other Lithium people specify 14.4v charging, so are happy with existing chargers. When I cancelled my original Roamer order due to the charging issues, the owner contacted me and said that they could set the BMS not to alarm at 14.4v which would make the battery fit with my existing charging equipment. Seems that it depends on who you talk to at Roamer when it comes to suitability of your existing charging equipment.
So I ordered the 230ah seat base, but I never got to use it : as it arrived faulty and was returned for a refund.

 

[Lenny HB]

Looked into having lithium fitted to our 2012 Dethleff Esprit but the cost has put me off

View attachment 711286

With those prices someone was taking you for a ride.

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[dawsey]

Looked into having lithium fitted to our 2012 Dethleff Esprit but the cost has put me off

View attachment 711286

Doing it yourself would cost approx £1200 in all the parts and two days if you really take your time and a ‘day’ of working on your van is 10-4 with a tea break every hour and half an hour for lunch (as any work in van is for me , half a day if you really know your van or are an electrician

 

[Garry - June]

I know its off topic but which compressor fridge did you switch to. Can you run the fridge off the batteries. Our 3 way fridge is garbage whereas the fridges on our boat run off batteries just fine so long as we start our generator or engines every few days when its not so sunnny.

We switched from a Dometic RMD 8505 to an RCD 10.5 compressor , apart from needing to lower the shelf the fridge sits on approx 2 inches it was a perfect fit for the old housing. ... the difference in power consumption is huge... not cheap I admit.. but as I say we fulltime so could justify it ,we paid £2290 for ours, but aside from the economies, it actually turned in to a blessing in disguise as when we removed the old one we discovered it had started to leak refrigerant (amonia) so was soon to be kaput anyway. With this new fridge and running on solar and batteries alone we have been able to go approx 6 days even throughout this winter before we need to switch on the EHU to boost the lithiums back up, We also ran for a month on EHU on our fulltime pitch so we could assess the energy use, with the old unit our monthly electric bill was £55 .. with the compressor it was £20 .. i predict within a couple of weeks and the improved weather (higher sun) then we wont need the EHU at all.

 

[cyberyacht]

With those prices someone was taking you for a ride.

I had a not dissimilar quote a couple of years back from VanBitz.

 

[Lenny HB]

I had a not dissimilar quote a couple of years back from VanBitz.

A couple of years is a long time ago with Lithium.

 

[Clive Mott]

The shape and size of your battery locker are the biggest factor. Also look at how cold it might get as, lithium needs special protection. Look very carefully at the features of the BMS.

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[Clive Mott]

And in the last 3 years prices have halved. 100AH with 100A BMS that also stops charging below zero. stops discharging below minus 20, protects against over and under voltage and lets you monitor it remotely on your smartfone via bluetooth. All for less than £450.

 

[Diabalo]

The shape and size of your battery locker are the biggest factor. Also look at how cold it might get as, lithium needs special protection. Look very carefully at the features of the BMS.

Plenty of room but the locker is external in the skirt so have been looking at the self heating ones. I don't use the van in the winter so may just stop the solar charging when the temp drops too low.

 

[Diabalo]

I e-mailed KS Energy this morning and asked them is it better to have one large one or 2 smaller ones?

Their reply came back pretty quickly.

A single battery is preferable unless you require very high current use, for example to power an inverter.

A single 200A can supply 1800watt inverters, but a x2 100A bank of those would run 2500watts, three 3600 watts etc

 

[dawsey]

This may be the case for the batteries which that outfit supplies. When looking for any battery, look at maximum discharge current. Usually, but not always, the larger the battery the larger the maximum discharge current.

For example:
Renogy 100ah - maximum discharge current 100A
Renogy 200ah - maximum discharge current 200A

As these will be (carefully) connected in parallel, in that manufacturers case, 2 x 100ah has the same maximum discharge current as 1 x 200ah, 200A.

A 200A discharge current will power a 2500W invertor.

 

[Lenny HB]

A 200A discharge current will power a 2500W invertor.

At full power a 2500w inverter will draw up to 230 amps depending on the efficiency of the inverter and that it not allowing for peak start up loads.
Although most people won't use the inverter at full power peak currents could well exceed 200 amps.

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[Raul]

The LFP does not dive much unless is under 50% charged, you will se a 12.8v. Most of the time will sit at 13.2v and above. I have a oven that draws 1440 on victron display. The max amp draw at that time is 114A or less. Being a resistive load is pretty much PF1 and all the power delivered is used.

Two batteries in parallel a very good think no doubt, but they need to be wired to a buss individually with their own fuse. They need to be treated as two individual sources. If one develops a fault, and is wired to the next, it will be to late to disconnect it. You do not wire one lithium to the next, and pick a -ve from one and a +ve from the other. I noticed this practice it’s been mentioned above, and someone may be taking this as good advise.
Each battery has to be individually fused at least. No wonder vendors recommend one instead of two, as is outside of their control how you use them, and may come back to them.

 

[Peppadog]

Thats interesting Raul. I am just about to wire in 3x50ah lithiums. I was intending to take a 16mm2 pair of cables from under the seat where they will live, to the 50amp breaker 1.5m away before a bus and distribution to b2b, mppt and 800w inverter. All victron. Sounds like I should fit 3x 50amp breakers after each battery under the seat, then bus, then off to the component cupboard?

 

[Guigsy]

Two batteries for redundancy is fine, provided one on its own can provide the power you need. If you have something 'critical' that needs the ampage output or energy capacity of both batteries, you're just doubling your chance of a failure.

 

[Raul]

Thats interesting Raul. I am just about to wire in 3x50ah lithiums. I was intending to take a 16mm2 pair of cables from under the seat where they will live, to the 50amp breaker 1.5m away before a bus and distribution to b2b, mppt and 800w inverter. All victron. Sounds like I should fit 3x 50amp breakers after each battery under the seat, then bus, then off to the component cupboard?

You have few options: 1;outback dc breakers near the battery, 2; mrbf cube fuse on battery terminal, or 3;bring all 3 batteries to the buss bar on mega/midi anl fuse. The later you will need all tree positives individually run to the buss. The first two option, you can combine the conductor, after the protection point.
I used the third option, in my case are two batteries with 600mm run to the buss bar fused with midi anl.

 

[G1969]

Tied into another thread, I am arranging to upgrade to lithium. My intention is for 1 - 460ah battery but would I be better with 2x 230ah?

I would welcome any installer/ electrical experts comments about the pros and cons of either please.

Thanks

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