LiFePO4 Lithium Batteries - the lazy way

[auslander]

Just now, MtB said:

 

 

 

Mr Sterling's listing on ebay is sketchy and lacking in detail at best!

 

In addition to the temperature limits being user-configurable, are charge and discharge disconnect voltages user-configurable too please? 

 

Muchly thanks. 

 

 

With the Daly BMS, yes, high and low voltage disconnects are programmable via the phone app.

I should also mention that one of the issues with the Daly BMS is that they don't register power draws below 2amp. So if you have a few LED lights on and the WiFi router, mine shows 0amp draw but in reality it is probably close to 1-1.5amps. Do this over 24-48 hours and the battery charge % in the app doesn't reflect reality. I've just become accustomed to watching voltage like you would with any other system.

[MtB]

1 hour ago, auslander said:

With the Daly BMS, yes, high and low voltage disconnects are programmable via the phone app.

 

Mnay thanks. One further question if I may...

 

Are the re-connect voltages separately settable, or does one have to accept the hysteresis decided by Daly?

 

I.e. if I wanted to disconnect the charger at say 3.4v per cell (approaching fully charged), could I set it to re-connect only when the first cell falls to say 3.2v? (approaching fully discharged.)*

 

 

* Ok one can quibble about the actual voltages! 

 

 

[Naughty Cal]

3 hours ago, auslander said:

With the Daly BMS, yes, high and low voltage disconnects are programmable via the phone app.

I should also mention that one of the issues with the Daly BMS is that they don't register power draws below 2amp. So if you have a few LED lights on and the WiFi router, mine shows 0amp draw but in reality it is probably close to 1-1.5amps. Do this over 24-48 hours and the battery charge % in the app doesn't reflect reality. I've just become accustomed to watching voltage like you would with any other system.

This is the only problem we have with our Sterling Lithium battery. It doesn't register small loads.

 

We often find after an evenings use the next morning the SOC is still showing 100% because we have only used light loads all evening.

 

Like you we just use the voltage as a rough indicator of SOC. 

 

Likewise the cycle counter is no use to man nor beast if you are only using light loads.

 

Next time we go out in the van we are going to make a conscious effort to use more power between charges.

[auslander]

1 hour ago, MtB said:

 

Mnay thanks. One further question if I may...

 

Are the re-connect voltages separately settable, or does one have to accept the hysteresis decided by Daly?

 

I.e. if I wanted to disconnect the charger at say 3.4v per cell (approaching fully charged), could I set it to re-connect only when the first cell falls to say 3.2v? (approaching fully discharged.)*

 

 

* Ok one can quibble about the actual voltages! 

 

 

No, I don't believe you could configure it like that out of the box. There is a UART port that you could connect another device (arduino, rasp pi, etc) to hack that functionality in.

[peterboat]

On 14/02/2022 at 22:29, TheBiscuits said:

I've bitten the bullet and taken the lazy route for Lithium batteries.

 

https://sterling-power.com/products/pre-order-lithium-batteries-12v-leisure-battery-5-year-warranty

 

I can't source good quality bare 3.2v cells and a beefy BMS delivered to the UK including VAT, import duty and shipping for those prices - and even if I could get close they wouldn't come with a warranty.

 

They are not quite drop in replacements, but they are very close.  Sterling insist on a battery-to-battery charger between them and an alternator or the 5 years guarantee is invalidated.  

 

The batteries include a suitably sized Daly BMS inside the case - charge at 0.6C, continuous discharge at 1.0C to 1.5C depending on which one you pick, so 300A continuous discharge from the 200Ah version.

 

I've added a 60A B2B charger and hopefully will now only need to replumb a few alternator and battery cables.

 

Discount prices for pre order, stock expected mid-February so the discount won't last much longer.

 

Spec sheet and full range here: https://sterling-power.com/collections/lithium-100ah-battery/products/lithium-batteries

 

Having been bitten by a few dubious aliexpress sellers - and having got credit card refunds - I gave up on DIY, although I was intending to use the Daly BMS as a simple solution anyway.

 

 

Just looked at the 150 batteries they are similar weight to my Valence ones, but it seems that they are 200ah?

Edited February 18, 2022 by peterboat

[TheBiscuits]

3 minutes ago, peterboat said:

Just looked at the 150 batteries they are heavy! 38 kilos are you sure that they aren't LAs in disguise 

 

?  The 300Ah ones are 33 kilos, the 150Ah ones are 18 kilos according to the spec sheet.

[peterboat]

Just now, TheBiscuits said:

 

?  The 300Ah ones are 33 kilos, the 150Ah ones are 18 kilos according to the spec sheet.

I looked at the wrong batteries and saw 38 instead of 33

[peterboat]

10 minutes ago, TheBiscuits said:

 

?  The 300Ah ones are 33 kilos, the 150Ah ones are 18 kilos according to the spec sheet.

I now have worked it out they put charging first and capacity later so I am totally confused! on phone at moment with small screen 

This is where it went wrong I think 

Edited February 18, 2022 by peterboat

[TheBiscuits]

Ah, yes the 24V 150Ah is the same as the 12V 300Ah.  it's just wired 8S rather than 2P4S.

[TheBiscuits]

24 minutes ago, peterboat said:

Just looked at the 150 batteries they are similar weight to my Valence ones, but it seems that they are 200ah?

 

As I understand it, the Sterling AMPS batteries are actually larger capacity than they say, and the BMS is factory set quite conservatively and password locked so end users can't fiddle with them.

 

That's why they can give a five year warranty on them as long as they are not connected directly to an alternator.

It also means you can use the full badged capacity rather than leaving a margin top and bottom.

 

The safety margin is still there but you can't use it anyway.

[Naughty Cal]

28 minutes ago, TheBiscuits said:

 

As I understand it, the Sterling AMPS batteries are actually larger capacity than they say, and the BMS is factory set quite conservatively and password locked so end users can't fiddle with them.

 

That's why they can give a five year warranty on them as long as they are not connected directly to an alternator.

It also means you can use the full badged capacity rather than leaving a margin top and bottom.

 

The safety margin is still there but you can't use it anyway.

One of the boating magazines did a test on various different Lithium batteries and as you say found that the Sterling AMPS batteries were indeed a larger capacity than advertised. Some 20% higher so the 100ah is in fact 120ah.

 

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

[TheBiscuits]

19 minutes ago, Naughty Cal said:

One of the boating magazines did a test on various different Lithium batteries and as you say found that the Sterling AMPS batteries were indeed a larger capacity than advertised. Some 20% higher so the 100ah is in fact 120ah.

 

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

 

Thanks, I'd not seen that before I picked my new batteries.

 

It confirms what I suspected though, the correct BMS, preferably oversized for the cells, is the key to good lithium batteries.

[MtB]

58 minutes ago, TheBiscuits said:

That's why they can give a five year warranty on them as long as they are not connected directly to an alternator.

 

 

I've been wondering about this, as the customer's alternator is not part of the contract anyway when buying batteries.

 

Then I realised it is a simple way to head off claims that "Hey, recharging your battery overheated and destroyed my alternator"!

[auslander]

9 minutes ago, TheBiscuits said:

 

Thanks, I'd not seen that before I picked my new batteries.

 

It confirms what I suspected though, the correct BMS, preferably oversized for the cells, is the key to good lithium batteries.

Could you expand on this please? How would an oversized BMS contribute to battery health?

[peterboat]

4 minutes ago, auslander said:

Could you expand on this please? How would an oversized BMS contribute to battery health?

It can balance cells quicker 

[MtB]

7 minutes ago, peterboat said:

It can balance cells quicker 

 

 

Cell balancing is probably one of the less important functions of a BMS. 

Edited February 18, 2022 by MtB
spelling

[peterboat]

1 minute ago, MtB said:

 

 

Cell balancing is probably one of the less important functions of a BMS. 

Given that I only have a battery balancing board on my batteries and they are still ok I am not so sure of that 

[TheBiscuits]

6 minutes ago, auslander said:

Could you expand on this please? How would an oversized BMS contribute to battery health?

 

A lithium battery is the bare cells connected together with the BMS.

 

Most of the cheap ones skimp on the BMS.  I've seen 300Ah batteries that only allow discharge at 50A and charge at 25A which isn't much cop for charging fast on a boat and then powering a big inverter from the battery.  

 

By contrast, the Sterling 200Ah uses a big enough BMS that it is rated for a maximum continuous discharge of 300A (1.5C).  It can spike much higher than this briefly.  It can also be charged at 150A.

 

The same cells fitted with a much smaller capacity BMS would be far less useful as a battery.  There's also the thought that using power electronics close to their maximum rating is a good way to shorten their lifetime.  A BMS that can handle 500 A current is not going to overheat when delivering 50 or 100A.

 

It just costs more for the bigger BMS so people trying to go cheap get the wrong one for the job.

[auslander]

4 minutes ago, peterboat said:

Given that I only have a battery balancing board on my batteries and they are still ok I am not so sure of that 

It was my impression that if the cells were to become unbalanced, you would simply lose total capacity as voltage limits would be hit earlier than other cells. The BMS would prevent any damage because they monitor the voltage of each cell individually.

1 minute ago, TheBiscuits said:

 

A lithium battery is the bare cells connected together with the BMS.

 

Most of the cheap ones skimp on the BMS.  I've seen 300Ah batteries that only allow discharge at 50A and charge at 25A which isn't much cop for charging fast on a boat and then powering a big inverter from the battery.  

 

By contrast, the Sterling 200Ah uses a big enough BMS that it is rated for a maximum continuous discharge of 300A (1.5C).  It can spike much higher than this briefly.  It can also be charged at 150A.

 

The same cells fitted with a much smaller capacity BMS would be far less useful as a battery.  There's also the thought that using power electronics close to their maximum rating is a good way to shorten their lifetime.  A BMS that can handle 500 A current is not going to overheat when delivering 50 or 100A.

 

It just costs more for the bigger BMS so people trying to go cheap get the wrong one for the job.

Using power electronics close to their maximum rating reduces lifespan is a good point.

[peterboat]

19 minutes ago, auslander said:

It was my impression that if the cells were to become unbalanced, you would simply lose total capacity as voltage limits would be hit earlier than other cells. The BMS would prevent any damage because they monitor the voltage of each cell individually.

Using power electronics close to their maximum rating reduces lifespan is a good point.

When I bought my batteries I did proper top balancing which was a long time ago 4 or 5 years I think? since then they have remained balanced. I have 6 domestic batteries, 30 x 36 volt drive batteries, 8 on my electric truck and 3 x 48 volt batteries on my electric car. At the moment they all seem to be working ok. Most are Valence batteries, but car has lithium polymer which I built into 48 volts banks with a battery balancing board on them.

[Richard10002]

On 17/02/2022 at 07:18, Alistair1357 said:

I took a simpler route for my LiPo4 bank. I don't charge them via alternator. Solar only. And a genny for winter necessity. 

Same here, (mainly). Solar when available, genny when solar isn't keeping up.... like now

 

Except that, since my 240v charger failed in November 2020, (??), I do have a Victron Orion 30A DC to DC charger which charges the Li bank from the the alternator, as a back up. 

 

As a consequence,  I also get the opportunity to charge when the engine is running if I want to.

 

 

[nicknorman]

 

1 hour ago, TheBiscuits said:

Most of the cheap ones skimp on the BMS.  I've seen 300Ah batteries that only allow discharge at 50A and charge at 25A which isn't much cop for charging fast on a boat and then powering a big inverter from the battery.  

 

By contrast, the Sterling 200Ah uses a big enough BMS that it is rated for a maximum continuous discharge of 300A (1.5C).  It can spike much higher than this briefly.  It can also be charged at 150A.

 

The same cells fitted with a much smaller capacity BMS would be far less useful as a battery.  There's also the thought that using power electronics close to their maximum rating is a good way to shorten their lifetime.  A BMS that can handle 500 A current is not going to overheat when delivering 50 or 100A.

 

It just costs more for the bigger BMS so people trying to go cheap get the wrong one for the job.

 

1 hour ago, auslander said:

Using power electronics close to their maximum rating reduces lifespan is a good point.

 

 

All of which is why I went for a bistable relay rather than MOSFETs to provide the emergency disconnect.

[MarkH2159]

On 18/02/2022 at 08:10, MtB said:

 

 

 

Mr Sterling's listing on ebay is sketchy and lacking in detail at best!

 

In addition to the temperature limits being user-configurable, are charge and discharge disconnect voltages user-configurable too please? 

 

Muchly thanks. 

 

 

Yes and yes.

 All voltages are user configurable.

Cell High/Low Voltage disconnect, Pack Sum High/Low voltage disconnect, Balance start voltage, Cell differential Balance start etc etc.

[TheBiscuits]

 

I'm a bit concerned about balance control on these Sterling batteries ...

 

[nicknorman]

Why, looks ok to me? Balancing can only occur when the battery is nearly fully charged.