More lithium battery advice needed please

[DuncT]

Morning all.

New member so please bear with me.

I've recently purchased a 2019 Knaus Van I (a class body) and want to upgrade to a decent lithium battery setup (attached pics of current setup).

I know/think I need to replace the mains charger along with adding a B2B charger and think I can pull the fuses within the EBL to stop the existing chargers working?

Could anyone please advise on the best way of connecting these new chargers as I'd ideally like to keep the current bits working (control panel functions for lights, water pump etc) and ideally use the current wiring so I believe I need to stick with a 30a b2b rather than a 50a?

I plan to go with Victron kit and around a 300ah battery. I will add solar once I've figured out how to get the wires down to the relevant places.

Any help/advice will be greatly appreciated

 

[lorger]

Not able to answer your technical question but we have a 2020 Knaus and the charger has a lithium setting so I’d double check that first, we’ve had a lithium for 2 years now with no issues.

 

[DuncT]

Not able to answer your technical question but we have a 2020 Knaus and the charger has a lithium setting so I’d double check that first, we’ve had a lithium for 2 years now with no issues.

Thanks for the reply. The EBL unit in our van only has a setting for AGM or Lead acid so I think it does need bypassing.

 

[Carpmart]

The thing is with lithium and applying the logic of, ‘we won’t need to plug in’ being one of the main drivers and accepting that it’s logical to install a decent DC DC charger and solar; the reality is you won’t use a mains charger.

If you do, keep an eye on the battery and don’t leave it for too long once it’s charged, in other words, switch off the charger. The battery doesn’t care what profile your charger has, all it sees is current which it accepts and stores. The BMS will protect the LifePo4 so with occasional use, really nothing to worry about!

There is a desire on this subject from many on MHF to quote ‘the optimal setup’ as the only setup… unless you will be charging from the mains regularly, which kind of negates the need for the setup you’re considering, I wouldn’t bother! Nothing bad will happen!

 

[bigtwin]

There is a desire on this subject from many on MHF to quote ‘the optimal setup’ as the only setup…

Indeed, of all the battery types available LiFePO4 is the most suited to an imperfect setup. In fact, such a setup (not charging to 100%) will extend the battery life, not compromise it.

I can understand the desire to obtain that last 1% but it really is a case of diminishing returns for each £ spent chasing it.

As I’ve said before there is a flourishing community in the boating world that use a hybrid lead acid/LiFePO4 battery bank that retains existing lead acid charging regimes (all detailed on the “12 volt boating group” on FB). If you’re chasing the last few percent then the arrangement is probably not for you.

Ian

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[Jev88]

Indeed, of all the battery types available LiFePO4 is the most suited to an imperfect setup. In fact, such a setup (not charging to 100%) will extend the battery life, not compromise it.

I can understand the desire to obtain that last 1% but it really is a case of diminishing returns for each £ spent chasing it.

As I’ve said before there is a flourishing community in the boating world that use a hybrid lead acid/LiFePO4 battery bank that retains existing lead acid charging regimes (all detailed on the “12 volt boating group” on FB). If you’re chasing the last few percent then the arrangement is probably not for you.

Ian

Have you got a link for the summary of leaving a car battery linked to a new lithium. Many general.sites advise against mixing etc etc ... But I know people have been doing it for some time and mention not fully charging the lithium is an advantage for longevity.

 

[DuncT]

Indeed, of all the battery types available LiFePO4 is the most suited to an imperfect setup. In fact, such a setup (not charging to 100%) will extend the battery life, not compromise it.

I can understand the desire to obtain that last 1% but it really is a case of diminishing returns for each £ spent chasing it.

As I’ve said before there is a flourishing community in the boating world that use a hybrid lead acid/LiFePO4 battery bank that retains existing lead acid charging regimes (all detailed on the “12 volt boating group” on FB). If you’re chasing the last few percent then the arrangement is probably not for you.

Ian

Thanks for this.
I'm not bothered about chasing the absolute maximum potential/setup. Just want something that's safe & works.

So can I just keep my existing setup and swap the lead acid battery for a lithium? And I assume disable the alternator charging and replace with a b2b item. Like the Victron 30a one.

Would it maybe be best to get a leisure battery with built in Bluetooth so I can monitor what's happening?

Cheers

 

[bigtwin]

Have you got a link for the summary of leaving a car battery linked to a new lithium.

No, other than to the FB group that I mentioned, but if you do a Google search you’ll find information. The important key word is ‘hybrid’.

Many general.sites advise against mixing etc etc ...

Yes, they do, but LiFePO4 and lead acid batteries actually work very well together in a hybrid arrangement. The vast majority of the work is done by the LiFePO4 leaving the lead acid sitting on a nice float from the LiFePO4 battery.

But I know people have been doing it for some time and mention not fully charging the lithium is an advantage for longevity.

Outside the boating world there are relatively few people who have gone hybrid. If you’re referring to simple ‘drop in LiFePO4 replacements’ then, yes, I believe that many people have. However, there are caveats (that I’m not sure that all of those who have done drop-ins will have noted). LiFePO4 batteries have a much lower internal resistance than LA so can draw significantly more current than LA do so there is the possibility that the existing wiring system may be inadequate. There can also be concerns that the alternator can be damaged either from overheating (because of the current being drawn by the charging LiFePO4) or from voltage spikes in the event that the LiFePO4’s BMS operates to isolate the battery. In the latter case that is extremely unlikely as the engine battery remains in circuit to absorb the spike (that, in fact, is one of the purposes of the LA battery in the hybrid arrangement used in the boating world).

So can I just keep my existing setup and swap the lead acid battery for a lithium?

Many have (I have not) done this and reported no problems. However, see my previous comment above.

And I assume disable the alternator charging and replace with a b2b item.

Most would advocate replacing the standard split charge relay arrangement with a B2B but not everyone does that. Again, see my earlier comments above.

Would it maybe be best to get a leisure battery with built in Bluetooth so I can monitor what's happening?

Most LiFePO4 batteries these days come with a bluetooth BMS but yes, information is power.

Like all these things, if you don’t understand the issues, it is best left well alone or trusted to the professionals.

Ian

 

[oldiesontour]

Thanks for this.
I'm not bothered about chasing the absolute maximum potential/setup. Just want something that's safe & works.

So can I just keep my existing setup and swap the lead acid battery for a lithium? And I assume disable the alternator charging and replace with a b2b item. Like the Victron 30a one.

Would it maybe be best to get a leisure battery with built in Bluetooth so I can monitor what's happening?

Cheers

Bluetooth Can be useful for altering parameters & turning charge/discharge on/off but a battery monitor (shunt) is more useful to most,so neither essential but both desirable perhaps.

 

[MichaelT]

We don't have a mains charger and have been off grid for 6 weeks, batteries topped up with solar and 50a B2B. We use air fryer, electric kettle, remoska, slow cooker, hair dryer, coffee machine etc and run fridge about an hour a day off the inverter.

I 200a KS and 1 280a Fogstar batteries.

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[LostInSpace]

and replace with a b2b item. Like the Victron 30a one.

I have seen reports that the Victron 30A runs too hot.
Our Hymer came with the Schaudt WA 121545 which works very well.

Would it maybe be best to get a leisure battery with built in Bluetooth so I can monitor what's happening?

Depends if you like playing with bluetooth.
A shunt based meter from Sterling Power or Roadpro will do the job very nicely without bluetooth.

 

[Pugsy]

Thanks for this.
I'm not bothered about chasing the absolute maximum potential/setup. Just want something that's safe & works.

So can I just keep my existing setup and swap the lead acid battery for a lithium? And I assume disable the alternator charging and replace with a b2b item. Like the Victron 30a one.

Would it maybe be best to get a leisure battery with built in Bluetooth so I can monitor what's happening?

Cheers

I would go for the Victron 50A DC-DC charger instead of the 30A one.
The 30A is a lot bigger and heats up more than the 50A,plus the 50A is adjustable if you want to change voltage settings the ,30A is not.
Just my thoughts of course.

Cheers Cris .

 

[DuncT]

I would go for the Victron 50A DC-DC charger instead of the 30A one.
The 30A is a lot bigger and heats up more than the 50A,plus the 50A is adjustable if you want to change voltage settings the ,30A is not.
Just my thoughts of course.

Cheers Cris .

Would you/anyone know where this should be connected to? Can I fit the unit where my existing EBL unit is and then use the relevant cables to each battery?
Or do I have to run new wiring from the DC charger to each battery?
I'd obviously rather the first option and I'd read that if I stick to 30a then the current wiring is fine.

 

[MichaelT]

Would you/anyone know where this should be connected to? Can I fit the unit where my existing EBL unit is and then use the relevant cables to each battery?
Or do I have to run new wiring from the DC charger to each battery?
I'd obviously rather the first option and I'd read that if I stick to 30a then the current wiring is fine.

If you putting in 2 (or more) batteries connect them to bus bars then run cables to the bars and set it up to the size of the combined batteries. Would also fit a shunt to give you more accurate measurements of SOC etc. Shunt should be first thing off the battery negative then all feeds from there.

 

[Pugsy]

Would you/anyone know where this should be connected to? Can I fit the unit where my existing EBL unit is and then use the relevant cables to each battery?
Or do I have to run new wiring from the DC charger to each battery?
I'd obviously rather the first option and I'd read that if I stick to 30a then the current wiring is fine.

Hi, I wouldn't want to give advice on how to connect it as I am just learning all the lithium set up at the moment.
I have a far better understanding now than a few weeks ago after a lot of research and I am booked in at Off-grid power solutions RogerIvy to get an installation beginning of April when I get back from Spain .Roger is a member on here and offers a 10% discount to funsters. I am sure the more experienced electronic funsters can answer your question with the correct info about your setup.

Good luck it is a minefield changing stuff.

Cheers Cris .

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[LostInSpace]

Would you/anyone know where this should be connected to? Can I fit the unit where my existing EBL unit is and then use the relevant cables to each battery?

Depending on how the EBL is wired (and what version it is), you may be able to disconnect the high power cables from the back of the EBL and connect them just to the B2B instead.

That is basically how Hymer have wired our new Exsis-I. The battery wies to the back of EBL are not needed. (And there is no D+ to the EBL either.). Battery charging is done via other low power connections - with smaller fuses.

 

[DuncT]

Depending on how the EBL is wired (and what version it is), you may be able to disconnect the high power cables from the back of the EBL and connect them just to the B2B instead.

That is basically how Hymer have wired our new Exsis-I. The battery wies to the back of EBL are not needed. (And there is no D+ to the EBL either.). Battery charging is done via other low power connections - with smaller fuses.

This sounds exactly the sort of thing I want as it'll be easy to add.

I've attached the manual for my EBL unit which does have a positive and negative going to the engine and leisure battery.

So would I just disconnect these from the EBL and fit the b2b charger between the wires? Or leave them connected to the EBL, pull the fuse that deals with the split charging and connect the b2b charger onto these wires.

Thanks again for the help.