Originally Posted by 1der
Since the Lithium batteries will be inside due to low temperature intolerance, the AGM's could be inside as well, and thus not suffer the 40% drop in capacity. Closer to 200 Ah would be available to cover the three days.
This is true. The lithiums will discharge just fine in any temp - you just can't charge them below 32 degrees. The other problem is that with a 200 Ah AGM is that we'd need to recharge that daily. We're not willing to use a generator, and if it's snowing, the solar panels are useless. That means *a lot* of idling. AFAIK - there is just no way to get around the fact that the absorption phase takes a really long time on an AGM. We need at least 48 hours of power draw from the batteries, so a 200 Ah internal AGM won't really cut it.
My guess though is with D5 fan and requisite water pumps, plus fridge and other draws, you would be looking at around 100 amps draw per 24 hr period. So, 48 hrs without charging and and you are into the AGM's less desirable sub 50% territory.
Yep - if we want to have water in the winter, we really need at least a 400 Ah AGM setup as a minimum. If we could get a 10K lb GVWR in a Sprinter 144 4x4, we'd def do a big AGM bank. But, as of now if you want a 144 WB Sprinter 4x4, you only have the option of 8500 lb GVWR. Going with a long van opens up the weight range, but those are too big to take offroad IMO.
I fully understand exploring new technology/solutions, and the attractiveness of "new" and unique. If that is what you want, more power to you to explore! I spend numerous crazy hours thinking about how to do something different/better/cheaper, I get it, ask some of the members who know me, I am nuts! Truly, I understand. But I also look at reliability, life cycle costs, maintenance as major components of the final decision.
It's less about new and unique, and more about utility. If we keep with AGMs, having water in the winter would be difficult to impossible given the AGM weight we'd need. Not only do we not have the payload to carry a large AGM bank, we don't have a way to recharge them in snowy conditions short of a generator or idling all day. With lithium, we get a weight savings and rapid recharge. I mean, that is almost a game changer in my book. We looked at every conceivable possibility and it seems like there is just no way around the long absorption phase with AGMs. We could survive for 10 days in the winter with lithium (limited by only water supply). How long do you think it takes to take a 400 Ah AGM bank from 50% to 100% without solar or a generator?
But you are asking and thus I am offering:
A few things come to mind just for discussion - why go with a D5 and the extra draw of the water pump(s)? You could go with two D2's, run both for occupant heat, run one for maintenance heat and reduce the draw for heating to about 20 amps for 24 hrs. This would also reduce your fridge draw requirements by keeping the interior around 40 degrees and you could have redundancy. Your fridge would use around 20 to 25 amps per 24 hr period. This gets you to nearly four days consumption without any recharge. And what if you go two more days and the batteries drop to 30% capacity left? They will still recharge many, many times before they need to be replaced. At the cost differential of a Li battery vs AGM, you can replace AGM batteries quite a few times. The AGM will take a heavy charge up to about 90% then needs to taper off pretty quickly for the last 10%. So, I do not really see charging as a huge factor between Li and AGM. Hot water would have to be by some other system without the D5.
Two D2's would cost the same as the D5. We consider the engine as a secondary heat source. It becomes more of a technology problem when considering we need to monitor interior temp and notifying us of a low-temp issue. A remote car start would then be used to get things heated up. From earlier posts I made on here inquiring about how long it takes to recharge an AGM bank with idling, it was indicated it would take a *really long time.* When I look at charts, they show a charge current of 60 amps for a charge current. Lithiums will take up to 400 amps. Is my information wrong? If I can keep a 400 Ah AGM bank topped off by idling for an hour a day, I may consider going that route. 1 hour is the max I'd want to idle the van daily for a variety of reason.
One area that the AGM cannot compete on is floor space required for battery capacity. The Li batteries will take up about half the space and 1/4 the weight of similar effective usage AGM bank (unless the AGM's are considered usable down to 30% capacity, which somewhat narrows the gap). This is a big plus for Li.
Plus, AGM's need special venting considerations. No such issues exist with Lithiums. It's personal preference whether you feel safe around lithiums, but we certainly do. Propane is explosive - lithiums are flammable.
But the robustness, tolerance, simplicity, and significant cost savings (this last is a bit arguable when looking at ten year time spans) around the AGM batteries is what was a strong consideration for me. One or two inadvertent mischarges on a Li bank could fry 5k in batteries very quickly, along with the other systems such as a flat plate, water lines, etc. which would also fail in a freezing condition.
The battery monitors are fairly robust, and generally the same tech as what exists today. There are a lot of protections build into them (over/under voltage, over/under temp, etc. If you buy the BMS from the lithium maker, their warranties are pretty good if something goes wrong. The battery itself for our requirement is under $4k, but still a financial risk. Considering the absolute loss in depreciation on the van itself, the risk of a battery failure seems palatable for us given what we gain by way of winter usage. We easily spend a few grand each year in hotels and gas getting to and from the mountains in the winter. Lithiums is def not a slam dunk win, and I would say for most people's usage, it's not worth the risk or cost.
Seems a bit precarious having a flat plate, water pumps, Li batteries, water lines all relying on a cutting edge configuration where the failure, if it occurs, is very expensive.
I would agree. While the D5 and BMS systems have all been around for a long time, nothing is fool proof. But, the BMS systems that control a Victron lithium battery are the same exact systems that control lead acid batteries. They're just set for lithium profiles. The D5 has been around a really long time and is pretty reliable. To me, that's really comforting. What I hope is that we can eventually an auto generator start system tied in with the remote engine start, and the AGS system will trigger an engine start based on interior temp or voltage. AGS systems tied to auto engine starts already exist and are fairly common. Adding in interior temp monitoring should be fairly simple to do. If we could get that added in the next few years, then we'd have the heating redundancy that we desire.
Are you back country skiing? Virtually all the towns we visited on our six week ski trip earlier this year did not allow overnighting at the resort nor did the towns look favorably on boondocking or parking where snow clearing was required. This resulted in our staying at Rv parks for many nights, not all, but most of which had power.
Yes. So, trail heads for BC skiing and Loveland is our main mountain for inbounds. They're fine with dirtbags in the lots as long as you can move the van for plowing. Crested Butte city is also fine with vans as long as you stay out of the way and nobody complains about your parking. Jackson is our main long-term stay where we'll frequently be for 5 days or more. They're good with boondocking.
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R so I only got the basics. But for ME, I use both DC to DC charging AND solar. Solar is portable panels I can set up away from the van to allow me to park the van in the shade and still get power. DC to DC charging doesn't do well if you are in camp for a 4 day festival for example, or on a hunting / fishing trip with friends. If you start up and go every morning, then solar is no need and on the contrary just extra effort and stuff. So use case is very important here...
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