Future proof solar and sizing dc-dc

[thehman]

Hi

I previously asked for feedback on my proposed electrical install. I was guided by members to have a deep dive into the prior responses / topics on the forum. Finding this in particular by dellmassive plus other posts and a bit of spreadsheet work has helped me get a handle of my usage, charging times, off grid capability etc. So thank you for that.

Thread '[Guide] DC-DC Charger (for leisure battery) -- How I Done It --'

3 Oct 2019

DC-DC Charger (for Leisure battery) -- How I Done It --

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Dellmassive`s -- "how I Done It" -- Thread
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Kit List And Stuff -- How I Done It & What I Use --
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I thought it was about time i addressed the whole DC-DC charger thing. . . .

The subject and viability is discussed at length over here > Stop/start...regen...smart Alternator... Dc-dc Charger For Leisure Battery Or Not?



Long story short the...

• Dellmassive
• auxiliary batteries dc - dc charger dellmassive how to guide leisure battery
• Replies: 673
• Forum: Electrics, Lighting, ICE, Security

• 

I have settled on the following spec. This gives me what I need in terms of off grid capability / days (Fridge, heater, couple of LED lights and USB ports).

Fogstar Drift 230ah battery (I wanted the heating as I spend time in colder climates, Alps winter).
30A Victron DC-DC Charger system
Victron 20A Battery Charger System
Electric hookup

I do want the ability to charge up 2x e MTB. But have decided this is probably better done when on the EHU rather than trying to handle this when off grid / off batteries, inverter etc.

Some questions...

In the dellmassive post above, this was mentioned with relation to sizing the DC-DC.

"So take your AUX battery size say 100Ah and go with 10-20% which is a recommended charge rate for SLA/AGM etc - thats 10-20A charger ."

So with a 230ah battery, this would imply my DC-DC needs to be in the range of 23A to 46A. My 30A proposed sits in the middle of that range. Does that seem ok??


However, I do have a big question over solar.

For my UK usage, I do not think this will help me. Purley because my UK trips (mostly shorter) will probably be catered for by my battery plus the odd nights hookup on a campsite.

But I do plan on longer trips in Europe and solar gives me options, but still not sure I need it.

So I have 3 options as I see it.

1. Install solar now

Pro: all out of the way now
Con: I may not need it

2. Install solar cabling now (and leave up behind ceiling which can be removed to drill a route outside for cabling).

Less invasive if I decide I need it for minimal cost.


3. Use one of the suitcase / folding chargers for trips to Europe if I find out I need solar.

If I went this route, how do you make the connection to your electric set up?

Are they any good?

 

[ben5560]

I am not an expert, but your battery choice is lithium, and AI says this:

Lithium (LiFePO4) batteries charge optimally at 20–50% of capacity. For my 100Ah battery as an example:

• 0.5C = 50A — This is the typical maximum recommended charge current for everyday use
• 0.3C = 30A — The "sweet spot" balancing speed and longevity
• 0.2C = 20A — Optimal for lifespan (+15% cycle life) but slower

I have it currently set at 50A on my new Victron XS 50, but may limit it now to 30-40 for longevity. That said though, the XS has been great so far, i dont have anything to compare it to but it just worked out the box, easy to set up, small / low heat and 50A... future proofed for a while!

 

[doncarlyon]

For the charger amp rating, check what your battery says...

My Renogy 100ah lithium says to charge it at 50A for instance.

 

[Drive Wayne]

I was forced to use a Renogy 220 watt suitcase solar panel when my flexi panel packed up. It worked very well when camping, especially if you had time to adjust the panels to the angle of the sun. Not so good with the van parked on the drive, but enough to power the necessary static power usage (Fridge, Cerbo, Ablemail and alarm system etc) while the van sleeps.
I left the solar cables wired into the Victron mppt and pulled them out when the panel was deployed. As an occasional use, it was fine, but I missed my permanent solar install.
We still take out the Renogy panels purely now to keep the Bluetti AC180 fully charged for the awning electricals.
Half a kW today from the 270 watt rigid, pleased with that!

 

[thehman]

Hi Drive Wayne,

Can I ask another question?

I think if I get a solar suitcase (for example 200W Portable Solar Panel) then I still have to have a Solar Controller (something like Victron Energy SmartSolar MPPT Solar Charge Controller 100V 20A).

So then, when I want to use the solar suitcase, I simply run the leads into the Solar Controller.

Is that how this fits together as a system?

 

[Drive Wayne]

Hi Drive Wayne,

Can I ask another question?

I think if I get a solar suitcase (for example 200W Portable Solar Panel) then I still have to have a Solar Controller (something like Victron Energy SmartSolar MPPT Solar Charge Controller 100V 20A).

So then, when I want to use the solar suitcase, I simply run the leads into the Solar Controller.

Is that how this fits together as a system?

I use the Victron 100/20. Works well with the Renogy 220 watt suitcase panels. Solar cables into the 100/20, a suitable length of cabling ending with MC4 connectors which then plug into the MC4 connectors on the panel. Keep a close eye on the MC4 separator tool, infact buy a spare! MC4's are good because of their waterproofness.
A good system to see if you find solar a useful proposition, before you put something more permanent on your roof.

 

[thehman]

Perfect, think I have a plan.

 

[CAB]

The Victron Orion 30A runs hot, the Orion XS 50A runs cooler.

For future proofing this is what you want.