DIY Lithium

xsilvergs

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Which 30 amp b2b do you have? Which mppts?
I have Victron. The MPPT's are great and allow you to customise settings and can upload data to the cloud (with a GX device) for review at a later date if you are that way inclined. The B2B is the Victron Orion TR Smart, it is very basic but once again fully customisable via Bluetooth app from a phone.

There are other makes available but for me Victron takes some beating. They also have a 5 year warranty (I think) but hopefully you'll never need to call on it.
 

Philip Tomlinson

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So the cyrix li ct is a smart split charge relay which will also allow charge to flow from solar to the starter battery? This is all you use to get significant charge from your alternator to your Diy Lithium leisure battery?
Can you set the max charge current to protect the alternator?
Yes, the cyrix is bi-directional so when your LiFePO4 battery reaches 13.7v for more than 2 minutes is will connect the starter battery to top it up. You can disable this via the enable pin.

The alternator protects itself as it is a modern Bosch unit fitted with an ic that monitors RPM and temp and throttles the current if required. Most vans built in the last 10 years have this kind of alternator. Also the cyrix has over current protection set at 120A and my alternator is 150A. Because of the circuit resistance I normally get around 90A whilst driving and 40A on tickover.

I know there is a video from Victron showing a 200Ah dumb (no BMS) lifepo4 battery connected DIRECTLY to an old boat alternator, which has nothing to do with motorhomes as we never connect directly to the alternator, we connect to the starter battery that regulates the current due to its higher internal resistance.

A few people have mentioned the above video to me and I always ask “does the person who showed you this sell B2Bs?”

I am not anti B2B with LiFePO4, but they are not needed, if they were Victron would not sell the Cyrix-li-ct.

58198725-F98F-498D-A396-26E0CEE4223F.jpeg
 
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wildebus

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FWIW, I tend to go with a B2B with Lithium rather than a Cyrix because it does control the current better than just allowing the battery to take what it wants from the Alternator (it is not unusual for older vans - especially VW Transporters - to start having issues with the extra strain of charging a leisure battery on top of the Starter and I prefer not to get the blame for what was a weak alternator when the red light comes on).
 

Philip Tomlinson

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FWIW, I tend to go with a B2B with Lithium rather than a Cyrix because it does control the current better than just allowing the battery to take what it wants from the Alternator (it is not unusual for older vans - especially VW Transporters - to start having issues with the extra strain of charging a leisure battery on top of the Starter and I prefer not to get the blame for what was a weak alternator when the red light comes on).
Yes, every van needs to be inspected and have a suitable system installed. Charge current can be limited using cable size (resistance) to. I think B2Bs are great for lead-acid, but for vans built in the last decade they are most likely not required.
 

Derekoak

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Today I took a screenshot from the Victron VRM of my lithium battery voltage with my engine running. My van is a 2013 Ducato with the standard 150A bosch alternator. My solar is switched off. The voltage you can see is the charge voltage from starter battery via a victron Cyrix-li relay. Please note there is only 9w going into the batteries which will be the self consumption of the four BMS units with their bluetooth radios on.

View attachment 97575View attachment 97576
The screenshot shows your equalisation voltage is above absorption so I assume manual equalisation happens. How often do you need to do that? Can your shunt reset from drift only during equalisation?
 

Harryw

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I don't use equalisation as the BMS do all the cell balancing.
If you select default Lifepo battery it will disable equalisation and also temperature compensation. Then you can trim the Bulk and absorption values to what you want, in doing so it then reverts to being a user defined battery but with those two still disabled ……
 
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Harryw

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Your sea shipping is a DDP price so is all inclusive tax paid delivered to your door.

As Phil says check your UPS (Air?) price as the important ‘DDP’ is missing from the quotation…. You could be liable for VAT and import duties…

as an aside I didn’t think they could airfreight that quantity of Lifepo4 due to regulations?

both mine and Phil’s came on a freight train, rather than a ship…
 

1 Cup

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If I’ve got this right Jeff, that’s 1240ah and about £1700. Phew! Have you ordered any BMS’s?
Hi 15kw. BMS , not yet but watching off gride garage from down underr. He's Andy just repacled his old one -BMS / broken one . L will need 4. Llooking at 200amp. Each and larger bus bars.
So about 2k plus 3.5k at victron.
 

1 Cup

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So I think this manufacturer ? For 16 cells 4 battery's.
BMS QUCC 200 amp
1621900323793-1807392845.jpg
 
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Harryw

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DDP is a internationally recognised term, Delivered Duty Paid, where the seller takes responsibility for all costs incurred.

For the avoidance of doubt just state clearly in your request you’d want a DDP price delivered to your door.
 

wildebus

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This may be of interest to those building their own lithium batteries...
So the battery is made of cells - usually 4 for a 12V Battery the way most folk are building them on this thread.
Cells look something like this ... (I think these are probably Winston, available via the Czech Republic pre Brexit)
1622026652812.png

What is inside the cell? Here is a photo from what I reckon is the same cell that I saw on the Victron Community Page
1622026793628.png
1622026849208.png

I bet not what you expected to see?

I was looking at these as I heard a comment from Victron about how you should only use the Lithium Batteries upright and not lay them on their side. I can't find that video again so don't know if it was for a specific product or general advice, but a comment on the community page said "As far as I know the cell manufacturers all say 'dont do it' because of stress internally where the poles are connected to all the (very thin) anodes / cathodes." - and note the guy says "all say 'don't do it'", not some.
So thought it worth mentioning this for consideration and thought when folk are working out how to package their DIY blocks and fit them into their vehicles. You see loads of very neat installations with side-mounted lithium batteries in and I wonder if the makers (marketers) of those batteries are sure the cell pack providers have warrented their use that way?
I recall seeing a Will Prowse video where he had a leaky lithium and it was down to a poor casing design with side-mounted cells not being correctly supported. This could be more common then realised and problems just waiting to happen?
 
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