[Paul-Carter]

I am totally with Neddy on this.

[Nut17]

I agree completely that the first priority is to fit as much solar as is practicable, but if you are touring down South over the colder months, a reliable robust DC - DC charging set up is a life saver.

[scubadoo]

Remember we are talking about a Toyota Hiace van here.

The maximum solar I could fit without it overhanging and looking stupid on the curved roof was 280W. They looked ridiculous when I originally tried them east-west.
Unless the roof profile has drastically changed on the newer models 600W or even 400W would prove to be a tricky installation.

Our extra LWB van in 2013. 2x 140W.

Click image to enlarge

No DC-DC converter/chargers were involved. Alternator charging was an important part of our travels at times.

If the alternator proves to be non "smart" then I think the added expense of any 20-40A DC-DC device is somewhat unjustified, not necessary and will seriously restrict any alternator charging to your proposed 100Ah lithium battery .

[mattn]

I am not an expert, by take is alternators and lithium batteries, especially in modern vehicles, can play together badly if not carefully implemented. Lithiums take a huge charge - a 100AH battery could easily try to take over 100A from an alternator, which is in addition to the vehicles own requirements. In vechile alternators are not really designed for this kind of continuous current and can become overheated. As said, I am not an expert, not idea if this is a problem in practice of if the systems are engineered well enough to cope. (Useful read here

A DC-DC charger does isolate the systems and all the issues of mixing different battery types and associated different battery charging requirements. Personally I think I would be heading down the Dc-DC charger route, sized after confirming the alternator can safely deliver the current the charger is rated for.

I also agree adding solar is better than adding or perfecting in vehicle charging, but the OP specifically indicated he did not want to do that. If the roof space has run out, portable panels are also an option for increasing capacity. Its not hard to imagine a system where additional panels are mounted under roof mounted panels on slides, giving an easily stored, easily deployed additional panel for only a little extra height.

[scubadoo]

To the OP. Unless your alternator proves to be of the "smart" variety your installation can easily be accomplished if your new battery is the "drop in" type with a VSR and quality MPPT solar controller setup. I like and use Victron products but your choice. The five year warrantee, full Bluetooth programmability and very regular software updates swayed me.

Our 300Ah Lithium battery has survived without any DC-DC device between the alternator and battery for 6 years of full time travel. No smoke yet.
The battery still delivered in excess 300Ah (4008Wh) in my latest capacity test 4 days ago.
I remain somewhat bemused with the recent fascination of these often unnecessary devices and struggle to grasp their purpose for most motorhome setups especially for a relatively straightforward Hiace van installation. Special requirements and caravans perhaps. At least it is not my money.
I note that in Australia many RVers have already bypassed any "smart" alternator limitations.
Many advertisers have done a great job in creating the "need" for everyone.

Advising people to spend money unnecessarily is not in my DNA.

In the meantime we will keep on trucking with our direct 90A until full alternator charging.

[toyotahiacefan]

Thanks everyone for so many replies, I had drafted a reply myself earlier but it got somehow lost. I will try to remember what I said:

1. Solar is definitely interesting but I want to get a somewhat working setup going before Christmas. With fixing solar to the roof, placing the roof gland, laying cables and what not that the alternator charging is something I can get something going faster.
2. Based on previous vacations I know that we seldomly stay in one place for a few days. When we do we still do day trips with the vehicle. So this is why I believe that the alternator heavy and first) strategy suits us. Maybe I need to think about a bigger battery then, to have a bigger buffer.
3. Regarding smart alternators, VSRs and DCDC chargers: I will check the alternator for its "smartness" and its nominal output. I understand that the numbers of nominal Amp output can probably not be sustained over a longer time without damaging it. I think I was initially under the impression that I needed a DC-DC charger to "protect" or rather properly charge the battery.
4. Regarding AGM and Lithium: I wanted to go with Lithium because of lower weight (remember it's a Hiace). I was also a bit surprised about the fact that you should not discharge AGMs below 50% and that they don't charge as fast.
5. I am after a system that is robust and that I do not have to tinker with and that I can trust is doing the right thing and is not damaging my vehicle (or more specifically the alternator) or the battery.

After only one thread I have noticed the different camps in this forum . Stay kind to each other!

Ok after all your input I am currently thinking this:
I believe that I will still go with a DCDC charger to limit the load on the alternator and I will choose the charger based on the available amps in the alternator with a big safety margin. The Renogy devices still look good to me.
I am considering getting a bigger battery, would the 100Ah/200Ah Sunnytechs (http://sunnytech.co.nz/product/12v-200a ... 4-battery/) play nicely with the Renogy? Do people have experience with that combination?
Do I need a separate low-voltage protection for the battery? The product page says "BMS Discharge cut off 9.2V". Is this ok to protect from over-discharge?

[Nut17]

The current crop of LiFePO4 batteries from Sunnytech are pretty good value. They use latest technology prismatic construction cells. With a full BMS including cell balancing taking a 12 volt battery to 9 volts will not cause any problems. You will extract the full 200 AH from a 200 AH battery without taking the battery below 12 volts. I have yet to install my Renogy DC DC charger so cannot comment on its suitability, but it does have a lithium setting so should be fine.

[Neddy]

I was surprised about the fact that you should not discharge AGMs below 50%

Ah, but that is NOT a fact!
Here is a "Life Cycle vs Depth of Discharge" graph for a $319 120Ah C10 battery (150Ah at C100).

Drawn down to 50% for each and every discharge, it should last for 1000 cycles. Used for, say, 100 nights a year, that's 10 years. The sky doesn't fall in if you go below the 50% level, of course. 70% discharging it down to just 30% every time should still give a life of 600 cycles, for instance. It is of course, the average drawdown figure that is the most important. With ours at 30Ah, the 100Ah AGM battery should last many years. (I got over 10 years use out of a set of cheap, bottom of the market AGM batteries.)
Lithium batteries are much better for high Charge/Discharge installations but we have no need for either characteristic - so for us, there is no point in paying a lot extra for them.