DC to DC + MPPT

[slocumjoseph]

While I get the money together I’m in the process of gathering enough knowledge and confidence to install a solar system on my pop top. I thought I had a handle on the parts and connections needed and decided an MPPT controller was needed. However I’ve now learned about the all in one DC to DC charger and MPPT controller. It seems to make sense although the initial outlay is high it should be more logical and cheaper if one box fits all. Now after seeing Dellmassives excellent diagrams and deciding the “Leisure Battery & DC-DC with integrated MPPT” was the way to go, I see the next diagram shows the dual purpose DC to DC charger and the MPPT controller wired in as separate units. Is it for the people who already have an MPPT solar controller… or am I missing something?

 

[IestynD]

I've just spent a couple of days reading that thread also... I am changing to a Lithium battery (probably Sterling-Power job)... I don't think i need a DC-DC charger as i'm still T5.1 no smart alternator, no stop start technology.

However, what i gleemed from that thread was some people may not want an all in one unit. If it packs up when you are away your scr3wed - no easy way to charge the leisure battery. At least with seperates you have one or the other (engine or solar).
All of that said, these things are fairly chunky so having seperates kind of defies the campervan rules of smaller is better!

Lete us know what set up you end up going for. I think i'm sticking with my Victron MPPT and Victron Landside charger... plus teh old skool relay for charging. I just need to check thats going to work ok with Lithium before i spunk £400 on a battery!

Good luck

 

[Skyliner33]

I installed a separate DC-DC and MPPT. AN advantage of this is if one fails you still have the other to charge batteries. Also some of the combined units are not able to handle the larger solar panels, its worth checking this before making a decision.

 

[slocumjoseph]

Thanks for the quick replies. Perhaps I'm making a complicated subject even more complicated for myself. I'll try K.I.S.S. Watch this space.

 

[Dellmassive]

@slocumjoseph I need to update the thread and schematics to detail the combined units.

I'm running the Renogy DC50s at the moment.

All you need is the fused battery feeds from the starter and LB.

A good ground.

An IGN feed.

Then the PV panel feeds.... Most combined units have the PV NEG connected to chassis ground... Then a separate PV POS input.


...

 

[t0mb0]

I've just spent a couple of days reading that thread also... I am changing to a Lithium battery (probably Sterling-Power job)... I don't think i need a DC-DC charger as i'm still T5.1 no smart alternator, no stop start technology.

However, what i gleemed from that thread was some people may not want an all in one unit. If it packs up when you are away your scr3wed - no easy way to charge the leisure battery. At least with seperates you have one or the other (engine or solar).
All of that said, these things are fairly chunky so having seperates kind of defies the campervan rules of smaller is better!

Lete us know what set up you end up going for. I think i'm sticking with my Victron MPPT and Victron Landside charger... plus teh old skool relay for charging. I just need to check thats going to work ok with Lithium before i spunk £400 on a battery!

Good luck

I think you’ll need a DC-DC for lithium, I wouldn’t use a relay to connect a lithium to the starter/alternator even if it is a T5.1.

 

[Deaky]

I've just spent a couple of days reading that thread also... I am changing to a Lithium battery (probably Sterling-Power job)... I don't think i need a DC-DC charger as i'm still T5.1 no smart alternator, no stop start technology.

However, what i gleemed from that thread was some people may not want an all in one unit. If it packs up when you are away your scr3wed - no easy way to charge the leisure battery. At least with seperates you have one or the other (engine or solar).
All of that said, these things are fairly chunky so having seperates kind of defies the campervan rules of smaller is better!

Lete us know what set up you end up going for. I think i'm sticking with my Victron MPPT and Victron Landside charger... plus teh old skool relay for charging. I just need to check thats going to work ok with Lithium before i spunk £400 on a battery!

Good luck

You'll definitely need a DC-DC charger, your alternator output is designed to charge a wet lead acid battery not a lithium battery.

 

[slocumjoseph]

Thanks for that. So, would you recommend that if I'm building the system from scratch with factory supplied starter battery and 120amp hr wet cell leisure battery. One dual purpose DC to DC charger with integrated MPPT controller would have everything I need covered. Or is it risky, as has been suggested, to have all my charging eggs in one basket?

 

[Deaky]

Thanks for that. So, would you recommend that if I'm building the system from scratch with factory supplied starter battery and 120amp hr wet cell leisure battery. One dual purpose DC to DC charger with integrated MPPT controller would have everything I need covered. Or is it risky, as has been suggested, to have all my charging eggs in one basket?

If you can find a combined charger that will handle your solar panel then I see no issue. I don't see an issue with all you charging eggs in one basket, You've only got one alternator and one leisure battery and I'd guess they're just as likely to fail as your DC-DC unit.

 

[IestynD]

You'll definitely need a DC-DC charger, your alternator output is designed to charge a wet lead acid battery not a lithium battery.

Thanks Deaky - of course you are correct... I just spoke to the guys at Sterling-Power they said the same... it would kill my alternator as the battery would make it run full whack all the time so would get early fatique and fail.

Thanks for the head up

 

[Deaky]

Thanks Deaky - of course you are correct... I just spoke to the guys at Sterling-Power they said the same... it would kill my alternator as the battery would make it run full whack all the time so would get early fatique and fail.

Thanks for the head up

Plus it will supply the wrong voltage to charge and maintain the lithium which could damage the lithium battery