Driving Charges my batteries only 10% per hour

[Charleerodgers]

This can’t be right surely? I’m lucky today as I have plenty of solar but the last week I have had to drive charge and the rate is so low I can’t see this being right. Can anyone advise what they think it should be around please.
I live in my van, I have 2x 100amp Victron lithium batteries (just upgraded) 400watts of solar panels with Victron MPPT controller and a Ctek d250 charge controller. Van is Vw crafter 2018 with smart alternator.
any advice would be appreciated. Btw I am not in anyway technical so if you could dumb down your replies, even more appreciated.
thanks

 

[Raul]

How do you charge from alternator to the house battery? I have the same van, and I use a battery to battery charger, instead of a split charge relay. It’s a must with smart alternators.

 

[Jim]

You'll likely need a B2B charger

 

[Charleerodgers]

The ctek is the battery to battery charger I believe

 

[Charleerodgers]

This is what I have installed

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[Revolvor]

The ctek is the battery to battery charger I believe

Yes you are right, the CTEK 250D is a combined Solar Charge Controller and B2B - as long as the connection from the Van battery to the CTEK unit has been made correctly. Do you have wires connected to all four terminals? With the CTEK, the original split-charge relay must be de-energised when the engine is running, for the B2B to be effective.

 

[Charleerodgers]

Yes all terminals have connections and to be honest I think it is wired correctly as everything works. I just expected that driving would charge them much faster. If I go down to 30% soc (which I have been doing frequently since not allowed unnecessary travel) without solar I have to drive for 7hours to get back up to 100%. This is not how lithium was sold to me

 

[autorouter]

The CTEK 250D contains a 20amp B2B charger. You have 200 amp-hours of battery capacity. 20 amps for 1hour is exactly 10% of your battery capacity, so it's working exactly as designed.

I'm sure your alternator is quite capable of very much more, but you'll need a beefier B2B. A 40A or 60A B2B would be much better.

Lithium batteries can charge/discharge at faster rates than the equivalent lead-acid batteries. A 100A charger would be fine. You could even get away with a 200A one, but that might be too much for the alternator.

 

[Pausim]

autorouter has hit the nail on the head. I have a 45A B2B on a single 100Ah battery which is over 40% per hour, you need a much beefier B2B.

 

[Charleerodgers]

Ah ok thanks. So it’s the ctek that’s underpower. Can you recommend a 100a battery to battery charger instead then please?

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[Charleerodgers]

I think the solution is the ctek smartpass as that will give 140ah when used together with the 250d

 

[Pausim]

I have a Votronic VCC1212-45 which I am very pleased with. It has a range of LiFePO4 profiles, including one suitable for Victron LFP.

 

[Pausim]

I know nothing about the Smartpass but if that is what it does it sounds ideal.

 

[Charleerodgers]

Yeah it does. Hope I’m right. This van has been a relentless money pit so this and a swap out for a bigger inverter and hopefully I can finally stop spending.
many thanks for your help?

 

[ctc]

Try putting the headlights on to fool the alternator, works on mine.

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[Revolvor]

I think the solution is the ctek smartpass as that will give 140ah when used together with the 250d

If you have room, a Smartpass can easily be added, using supplied connectors.

 

[Lenny HB]

Even for charging at 20 amps the cables to and from your B2B look far to small this will cause a volt drop and reduce the charging current.

 

[Revolvor]

Even for charging at 20 amps the cables to and from your B2B look far to small this will cause a volt drop and reduce the charging current.

This is from the manual -

 

[Lenny HB]

That says 4mm sq in & 10mm sq out, in & out are carrying roughly the same current and the input is normally a longer run than the output. Input.
Input and output cables need to be the same size. If keeping the same unit I would be inclined to fit 16mm sq on both input and out to minimise volt drop. If you change to a higher current unit you will need much larger cables.

 

[Revolvor]

If using the Smartpass, then input and output require 16mm2, or 25mm2 for longer runs.
My main reason for getting one is that solar and alternator inputs are sychronised, and both supply a "smart, 5-stage" charge.