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Sterling Power LiFePO4 (Lithium) Leisure Batteries


veletron

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Hi

 

I have been looking at Sterling Power's range of LiFePO4 Lithium batteries. I am thinking these are just Chinese imports that Sterling has put its name to, however, Sterling enjoys a good reputation so I am thinking that they would not put their name to any old thing.

 

Cost has come right down for Lithium to £540 for a 100AH battery, less if you shop via eBay. These appear to be well thought out and matched to the Sterling B2B which I already own (has a lithium setting).

 

I rather like the idea of having twice the usable power of my current lead-acid pair, as well as having a 30KG weight saving.

 

Anyone have any experience of these?

 

Karen

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As a Varta 95ah is only about £150 and about 26kg and guaranteed for 2 years, I am afraid I don't see the advantage or requirement of paying over 3 times the price, never mind the supposed "32KG" weight gain? With solar and B2B we manage to run Laptops, phones ,Tv etc and don't use hook ups and free camp for months often. Get more solar if you need it, it will last 20 years...
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Based on your calcs re the Varta 95, If a lithium lasts 8 years then it represents good value. NB: I get 3 years out of a set of LA's

 

The key for me is usable power. Drain a lead acid flat and it will do 20 cycles, do the same with lithium and it will still do thousands of cycles. Usable capacity of a lead acid is about 50% dod if you want it to last a couple years while lithium will do 80% dod and still last 6000cycles.

 

My issue is one of capacity, I have 200W of solar - there is no more space on the roof! I have a 60A B2B. I am needing to use my work laptop for a full working day. It pulls a steady 10A@12V so 80AH in a working day (it's a beast of a laptop as required for my job!). My choices are hookup or lithium, but I would like not to be stuck on a campsite (that's assuming I can even book one!).

 

I escape to the hills every weekend, driving back home for mon-fri has become a bit nuts given that all I need is an internet connection, laptop and reliable power supply to work from the van!

 

This is my main reason for considering lithium. Looking to fix my work/life ballance!

 

Karen

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steve hill - 2021-05-17 7:55 PM

 

As a Varta 95ah is only about £150 and about 26kg and guaranteed for 2 years,..

Which Varta battery are you referring to, please?

 

This TAYNA link

 

https://www.tayna.co.uk/search/varta%20lfd

 

lists Varta batteries in the “LFD” range that has been often recommended here as being particularly suitable for ‘general’ motorhome leisure-battery usage.

 

There’s no 95Ah LFD battery, but the popular-size LFD90 90Ah battery that weighs around 24kg can be obtained for around £93.

 

https://www.tayna.co.uk/leisure-batteries/varta/lfd90/

 

Next up is the LFD140, weighing around 37kg with an asking price of £145-£170.

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No personal experience of Sterling batteries but they performed well in independent tests by a boating magazine and recorded a capacity in excess of the specification.

https://www.pbo.co.uk/gear/lithium-batteries-for-boats-reviewed-12-of-the-best-lithium-boat-batteries-tested-62244/2

Sterlings own test against lead acid batteries under worst case conditions,

 

I do have experience of lithium batteries in a RV application and confirm that they live up to expectations. Charge very quickly and deliver power at almost constant voltage until near empty.

 

All lithium battery cells are made in China. There are degrees of quality in both the cells that make up the battery and the way the battery is assembled. To prevent the battery from user abuse, all are fitted with a battery protection circuit , often called a BMS, a battery management system.

Depending on the battery, this BMS will have maximum allowable charge and discharge currents, so this must be taken into account when selecting a battery. A typical quality 100Ah battery will have a continuous charge current of 50 A, and a continuous discharge of 100 A. Most will offer a number of charge and discharge cycles at their maximum ratings in the region of 2000 cycles.

 

Mike

 

 

 

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Wow our i7 laptops use 2A and the TV is 3A and of course are not on more than 10 hours a day so with solar or driving topping us up we never flatten the battery. Answer is go somewhere sunny to work as the solar will easily keep you charged, or retire he he!
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mikefitz - 2021-05-18 11:53 AM

Sterlings own test against lead acid batteries under worst case conditions,

Yup, saw the video. Impressive killing of lead-acid in that video. I am pretty hard on batteries myself, but I do get 3 years out of them!

 

I'm an electronics & software engineer by trade, so fully understand the tech etc, but little info out there on longevity, and one would want a £540 battery to last 10 years! That said, the Sterling test probably represents several years of real world usage done over 6 months.

 

I have placed an order now for 2x100AH LiFePO4 as the 120's wont fit, so I will either be boring you all with tales of Lithium being the future, or tales of woe to save others the bother!! I am hoping that the B2B will work better with the lithium's, with my LA, it runs at maybe 50-55A for an hour, but then the batteries steadily draw less juice despite being nowhere near full. Will be nice if the LiFePO4's do the 55A until like 90% full before tapering off.

 

The laptop is an octa-core i9 graphics workstation with a high end video card, 64GB memory, 2TB SSD etc. Power draw comes down to a more reasonable 60W when its just word-processing! The laptop screen is not big enough so I have an old dell 28" monitor that I take away too that draws another 30W.

 

Karen

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Well they showed up and they are installed. The sun is not doing much to charge them. A new mains charger which is LiFePO4 compatible and charges at 50A shows up today (again Sterling Power), the existing mains charger did not have a gel setting on it so was 14.7V/13.8V the boost is too high for LiFePO4 and at that cost I don't want to be killing them!

 

Some pics here (scroll to the end). https://photos.veletron.com/index.php?/category/222

 

NB: those angle brackets have served me well, they have just been re-adjusted for their third battery type. Far more versatile that an off-the-shelf battery tray.

 

Struggle lifting out my old 140AH Exide's @ 30KG a pop, Loved the ease of getting those new ones in. Will have to wait to next weekend to see how they perform, rubbish weather this weekend.

 

When the Mains charger shows, it will take the position of the existing B2B under the passenger seat while the B2B moves to where the old mains charger was - wont fit the other way.

 

Karen

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veletron - 2021-05-21 9:50 AM

 

Well they showed up and they are installed. The sun is not doing much to charge them. A new mains charger which is LiFePO4 compatible and charges at 50A shows up today (again Sterling Power), the existing mains charger did not have a gel setting on it so was 14.7V/13.8V the boost is too high for LiFePO4 and at that cost I don't want to be killing them!

 

Some pics here (scroll to the end). https://photos.veletron.com/index.php?/category/222

 

NB: those angle brackets have served me well, they have just been re-adjusted for their third battery type. Far more versatile that an off-the-shelf battery tray.

 

Struggle lifting out my old 140AH Exide's @ 30KG a pop, Loved the ease of getting those new ones in. Will have to wait to next weekend to see how they perform, rubbish weather this weekend.

 

When the Mains charger shows, it will take the position of the existing B2B under the passenger seat while the B2B moves to where the old mains charger was - wont fit the other way.

 

Karen

Karen

 

Be keen to see how you get on with lithium.

 

I had to replace my LAs last year and was tempted by lithium but at that time cost from Sterling was way higher than that currently listed.

 

I have 45A B2B + solar with lithium settings to suit Sterling batteries ................... but mains charger would need to be changed!

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Will Prowse is doing lots of cheap LiFePO teardowns and there just is no pattern to what you might get. Some are quite decent build quality, others are appalling. Personally I wouldn't be gambling because unless you open the case, you just don't know what you got. With a known company I assume there is at least some quality control you can count on but who knows...

 

One recent video here

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  • 3 weeks later...

(Very) Early days yet but initial observations:

 

1) The cell voltages (12V LiFePo4's have 4 cells) balanced themselves over the 1st week, the BMS doing its job, the bluetooth app for the batteries shows what's going on

 

2) The charge limit was 3.75V per cell, reading online, this is too high, between 3.65 and 3.75V there is less than 1% of capacity. I changed the limit to 3.65V using the bluetooth app.

 

3) Once any cell reaches the limit above, the BMS disconnects incoming charge, battery is 'fully charged'

 

4) Drawing power from the battery causes the charger to reconnect until the disconnect voltage 3.65V per cell is reached again

 

5) There are two mosfets in the BMS one for charging one for discharging, both individually controlled by the BMS

 

6) The batteries soak up solar better than my old lead acid's and I note from my BM100 Amp/Hour counter than the batteries are more efficient than my old lead-acid's eg if I draw 100AH, adding 106AH brings be back to full charge. On my old batteries 130AH of charge would be required to replace 100AH drawn

 

7) Discharge voltage much more constant vs SOC (compared to my old LA's) Starts at 13.6 volts calls to about 13.2Volts with 20% remaining

 

8) Even with my inverter pulling 100A the battery voltages don't 'dive' 100A of draw knocks just 0.1V off the voltage. This has advantages for both inverter and switched-mode loads in that a higher voltage results in less current being pulled P=I*V In contrast loading my fully charged LA's would see the voltage dive from 12.8V to under 12V.

 

9) My Sterling B2B works better with the new batts vs the old LA's. With the old batteries, it might have started at 50A, but this gradually dropped off such that by the time the cells were 75% full they (pair) were pulling <20A between them. This meant that charging took an age. The lifePo's will pull the full 50A until they are 95% full before it drops off. My B2B is a Sterling 60A unit, but remember that's input current; the boosted output current is more like 50A due to higher voltages and the fact that nothing is 100% efficient.

 

Sorry for the geek-speak!!

 

Will need to wait for winter for a proper test!

 

Karen

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Thank you for this Karen.

 

I went ahead and installed 2 of these as well. They've not been tested in use yet, but I noticed on delivery that Cell low cut off was not the same; Battery 1 - 2.75v Battery 2 - 2.00v Big difference. After speaking to Sterling I altered these to 2.5v.

 

I have a Schaudt 45A B2B and a Votronic 25A mains charger, both set to lithium (14.4v). At 70% SOC (and checked separately!) I'm getting 13.7v at batteries, not 14.4V. If I pull the output fuse the voltage at mains charger rises to 14.4v so I suspect the CBE DS520AN Distribution Box is pulling the volts down, so I'll try mains charger connected directly to batteries to check.

 

My B2B is in the supply between starter and Distribution Box and worked great with LA batteries, but only 13.7v at lithium batteries?

 

In both cases though the charge current is to spec and batteries charge to 100% SOC FAST according to app!

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For maximum life, I would say that 2.5V per cell is too low. See the SoC chart here: https://diysolarforum.com/threads/lifepo4-voltage-chart.3156/

 

In normal operation of course you won't get anywhere near it anyway so it's a means of protecting the battery from low SoC if you leave something turned on. I have set mine to 3V giving a cutoff at 12V. When I manage to get the batteries down to a low SoC (winter!), I'll refine this for when the inverter is running to avoid it getting a it's juice cut due to supply voltage drop at low SoC.

 

Karen

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veletron - 2021-06-09 8:59 AM

 

For maximum life, I would say that 2.5V per cell is too low. See the SoC chart here: https://diysolarforum.com/threads/lifepo4-voltage-chart.3156/

 

In normal operation of course you won't get anywhere near it anyway so it's a means of protecting the battery from low SoC if you leave something turned on. I have set mine to 3V giving a cutoff at 12V. When I manage to get the batteries down to a low SoC (winter!), I'll refine this for when the inverter is running to avoid it getting a it's juice cut due to supply voltage drop at low SoC.

 

Karen

Thank you Karen I'll alter mine to 3v as well :-D :-D

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  • 3 weeks later...

Hi

 

I'm between houses and WfV at the moment and hardly any sun this past few days. The 2x100AH LiFePO4's have been holding up well with 174AH discharge from a starting point of 100%. Could not have done that with my Exide LA's. Still 35% indicated as remaining. Hungry laptop + inverter is the source of most of that drain.

 

Karen

 

16246230763842.jpg.06f5fc5d6249af21cdf70bc075830b82.jpg

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Thank you for update.

 

Don't want to usurp your thread but we've just had 2 weeks away with our two Sterling lithiums and we are delighted with charging etc :-D

 

Question: the battery terminal studs are short, with plain washer and a locking washer. Because these studs are relatively short I find it difficult to get all the accessory leads connected!

 

For example, the mains charger, solar controller and B2B all have temp sensors connected to negative. These can be shared between the two batteries but there are other accessories to accommodate - voltage sensor for B2B, mifi charger, inverter etc

 

Do you find it a fiddle to accommodate everything on the studs? Do you remove the washers to create more space, or maybe longer studs are available?

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Its poor practice to have multiple connections at the battery posts. The ideal method is to use positive and negative buss bars, with a single short cable link to the battery post.

https://www.12voltplanet.co.uk/4-point-positive-distribution-block-busbar.html

Having multiple cable terminal connections on the battery post will over stress the post and lead to unreliable connections. Best practice is to have no more than 2 connections per stud.

 

Its probable that the lithium battery installs are incorrectly fused. The BS standard for 12v systems in leisure vehicles requires suitable over current protection at the power sources, the batteries, for all cables connected . Lithium batteries under fault conditions can deliver very high currents, several thousand amps. Most available fuses do not have the necessary interrupt rating. With a 12v systen its recommended to use a MRMF, (cube fuse) as close to the battery positive post as practical,

https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

 

Hopefully the BMS protection built into the battery will offer over current protection, but this is not guaranteed and depends on semiconductor circuits and fet switches to disconnect.

 

Mike

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Hi

 

Sorry for the delay responding. I only have one cable per terminal from the batteries. I common the -ve cables using the current shunt from my BM1 current monitor while the +ve is commoned with a covered bus bar.

 

I've also made use of where my inverter is located to use the studs on this as a link point for my B2B and batteries.

 

See pics. The other box you can see in pics is an aux fuse box for the many gadgets I have in the van! Due to inverter use, the whole lot is wired using 4AWG welding cable. Batteries are fused at 80A individually close to the battery using resettable fuses.

 

Karen

 

16250904794770.jpg.ae6bed0708bade74d11ef347b8b70c6a.jpg

16250904795241.jpg.2770235c4eed79c7549347f31b258874.jpg

92748639_1625090479548201.jpg.d243d8b07e13cfff48d2e7ce893025c5.jpg

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Thank you Karen.

 

Most of my wiring is commoned on busbars, though the inverter is taken directly off the batteries. I've used 4awg cable between batteries and busbars. The inverter comes with 4awg cable (Sterling 1800w).

 

I'll alter inverter cabling to meet at busbars.

 

How have you fitted temp sensors? They are supposed to be direct on negative post. I have 3 to accommodate - B2B, mains charger and solar regulator. Could I put these on busbar too?

 

Arthur

 

PS a lot of the cabling in my van came in convoluted conduit and I've continued that practice, but it does look untidy compared to yours, so no photos from me :-S :-S

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Quote,

 

' They are supposed to be direct on negative post. I have 3 to accommodate - B2B, mains charger and solar regulator. Could I put these on busbar too?'

 

On a lead acid battery the negative post is connected to the lead plates, has a good thermal path to the battery core temperature and thus is an ideal mechanical ( and electrical) point to attach a single wire thermal probe.

 

On a lithium battery the negative post is connected within the battery case to the output side of the BMS protection module by a cable.

As such, its more likely to measure the temperature of the cable and BMS rather than the temperature of the cells that make up the battery.

However they need to be connected somewhere if necessary to control the charge process, so connecting to the battery post is perhaps the better option rather than the buss bars.

 

Lithium batteries do not need temperature compensation of the charge voltages so unless the chargers are using temperature monitoring for low temperature charge disable, ( less than 5C) or battery overheat ( over 45C), they are not needed.

 

Mike

 

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