Going Lithium-Iron Phosphate

[cruisersl]

Originally Posted by rowiebowie

Your pocket book will smart for a while, but you'll smile when you realize you have over 3x'd your usable power.

I suggest a combined Inverter/Charger of at least 2000 watts. Also, add a DC to DC charger between your chassis battery and new lithium coach batteries plus a battery monitor. I went with all Renogy setup, but there are other more & less costly options.

Make sure all components have a charging profile for lithium batteries (including solar controller if you also have roof panels) and that you draw no more than 40 amps from your engine alternator when charging while driving.

Why 40A max? Why not 50A? Renogy's 50A DC DC MPPT comes to mind - works great in my van (2004 Dodge Sprinter 2500 T1N) - so far (~ 1000 miles).

[rvsprinterguy]

Originally Posted by markopolo

Do you have a link to the Cots unit?

Not yet... still deciding.

[rvsprinterguy]

Honeyboy, thanks for relating your experience with your Li battery pack. I'm probably going to go with a DC-DC charger. Right now, the batteries, the PD 600 watt charger, and a Renogy inverter are on my bench. Currently, I'm using the setup as a UPS for my garage freezer.

[booster]

Originally Posted by rvsprinterguy

Honeyboy, thanks for relating your experience with your Li battery pack. I'm probably going to go with a DC-DC charger. Right now, the batteries, the PD 600 watt charger, and a Renogy inverter are on my bench. Currently, I'm using the setup as a UPS for my garage freezer.

It would be interesting to know if Honeyboy is charging with the original isolator and cabling to the coach from the alternator as those would both help limit the charging current to the batteries do to voltage drop and probably circuit breakers, if still used.

[GallenH]

Hypothetical situation: Single 100AH Lithium battery with a battery monitor.
Battery charged via alternator through a B2B which sets LiPo4 profile.
Battery charged via solar panels with controller which sets LiPo4 profile.
Battery charged via convertor with controller which sets LiPo4 profile.

Am I wrong in seeing a lot of controller redundancy? I mean couldn't the solar and convertor go also into the B2B directly without their own controller algorhythms trying to establish the correct timing of the charge cycles?

I know that there must be a reason that escapes me.

thx.glenn

[GeorgeRa]

Originally Posted by GallenH

Hypothetical situation: Single 100AH Lithium battery with a battery monitor.
Battery charged via alternator through a B2B which sets LiPo4 profile.
Battery charged via solar panels with controller which sets LiPo4 profile.
Battery charged via convertor with controller which sets LiPo4 profile.

Am I wrong in seeing a lot of controller redundancy? I mean couldn't the solar and convertor go also into the B2B directly without their own controller algorhythms trying to establish the correct timing of the charge cycles?

I know that there must be a reason that escapes me.

thx.glenn

Some (KISEA) B>B devices can take two inputs from solar and altenator.

[hbn7hj]

Originally Posted by GeorgeRa

Some (KISEA) B>B devices can take two inputs from solar and altenator.

They sure do, works very well.

[hbn7hj]

Originally Posted by cruisersl

Why 40A max? Why not 50A? Renogy's 50A DC DC MPPT comes to mind - works great in my van (2004 Dodge Sprinter 2500 T1N) - so far (~ 1000 miles).

That is a Mercedes sprinter spec for the maximum from their alternator to the coach battery.

[GallenH]

How are isolators/separators wired? IOW does the engine alternator output go to the engine battery and then go to the isolator/separator which passes to the cabin battery. IOW does it pass through the engine battery where the cabin battery is seen as an additional current draw and the purpose of the isolator is simply to prevent the draw on the cabin battery from ever depleting the engine battery.

Alternator--->engine battery-->isolator-->cabin battery

or is it

Alternator-->isolator-->engine battery
-->cabin battery

Sorry but my return/spacing doesn't seem to work. What th 2nd one is supposed to show is all alternator output going directly to the isolator which splits the output sending some to the engine and some to the cabin.

[GallenH]

Yes. The KISEA deals with the output of the alternator and solar which is exactly what I was asking. But what about the shore convertor? I assume that you could set its profile to = the B2B KISAE's profile but I was just curious if you could also route the convertor through the B2B like the solar panels (provided there was some setting on the convertor which, instead of trying to mimic a staged profile, would be a constant out). Probably a silly question.

[GallenH]

In your diagram earlier in this thread it seems like you placed the shore convertor in a position where it could charge either the AGM or the LiPo4 or both. Wouldn't the charging profiles be different? How did you deal with that?

[GallenH]

So here's my thought about a hybrid on an old 97 PW with a single 100AH AGM.

1. Add 200AH of LiPo4. Primary objective = run a compressor fridge. I "think" that my existing PD convertor/charger and my 136AH alternator would handle 200AH. But I'm not sure.
2. The primary use of the 200AH LiPo4 would be to run the fridge and the bank's output would be directly connected to the fridge.
3. The existing AGM would run all other cabin needs (lights, water pump, furnace fan, etc.)
4. All charging sources (alternator, solar, shore charger) would charge the LiPo4 bank with, possibly, the provision via an A-B-AB switch to do both.
5. The LiPo4 bank would also be switched to charge the AGM when needed.

I suppose the system could be switched so that the alternator charges both the LiPo4 and the AGM but I'm not sure that a 136A alternator could handle that (300AH worth of battery). In this setup a B2B would be needed coming into the lithium and an additional one going into the AGM....I think.

Harry and @Michael have done great work in this hybrid area. Also Blueboy1 in Ca has built a non-hybrid system that supports a compressor fridge on my exact platform with additional AGM+solar.

Any comments/observations GREATLY welcome.

thx.glenn

[avanti]

Originally Posted by GallenH

How are isolators/separators wired? IOW does the engine alternator output go to the engine battery and then go to the isolator/separator which passes to the cabin battery. IOW does it pass through the engine battery where the cabin battery is seen as an additional current draw and the purpose of the isolator is simply to prevent the draw on the cabin battery from ever depleting the engine battery.

Alternator--->engine battery-->isolator-->cabin battery

or is it

Alternator-->isolator-->engine battery
-->cabin battery

Sorry but my return/spacing doesn't seem to work. What th 2nd one is supposed to show is all alternator output going directly to the isolator which splits the output sending some to the engine and some to the cabin.

Your question isn't really well-formed.

Batteries, charging sources (including alternators), and their loads are all wired in parallel, not in series. Nothing goes "through" anything else, with the exception of the isolator, which either connects or isolates the positive side of the parallel connections on the coach side from those on the chassis side. When it is closed, all the chassis stuff is in parallel with all the coach stuff (and thus, everything is at the same voltage). When it is open, that parallel link is broken, and there are two independent systems, each with its own voltage.

It looks more like this:

|<---------Alternator
|<---------Engine Battery
|
V
isolator
^
|
|<----------Cabin Battery

[hbn7hj]

You are missing a good way to charge your lithium batteries. It would take a lot of solar (300 watts) to charge 200AH of lithium especially since you intend to use them. Solar should charge lithium only.

You need a B to B charger from the alternator (40 amps) or a generator with charger. At that rate the engine would need to run two hours a day or so without solar. Driving daily would take care of that, sitting will leave you way behind.

Lithiums charge quickly. You should have a 100 amp source to take advantage of that.

I choose generator but I don’t think you are going there. Just an opinion.

[GallenH]

I think I understand. So when you're driving along, the alternator is charging the chassis battery and, simultaneously, the cabin battery.

When you stop driving, and the alternator is out of the picture, does the chassis battery continue to charge the cabin battery?

I'm assuming that the isolator must have some way to disconnect the potential drain on the chassis battery from the cabin battery. That, as I understand it, is the purpose of the isolator: to protect the chassis battery from being drained by the cabin battery so that you don't end up in a situation where your chassis battery is dead and won't start the RV.

Is that correct? And how does the isolator control that?

thx.glenn

[GallenH]

You are correct in assuming that I'm steering away from adding a generator. I know that you've been pondering adding a compressor fridge to your B. Have you? You have been the pioneer in exploring hybrid. What did you come up with. Or have you decided to stay with 3-way.

[hbn7hj]

I have a compressor conversion for my class C but the absorption cooling unit seems to have improved or moving the freezer sensor from the door to the cooling plate makes me feel better about it. I got 6F temps all summer so the compressor stays in the hallway in the house. Even with 400 amp hours of lithium I’m not looking forward to providing another 40 amp hours a day. As long as it works the original stays but it will not be replaced with an absorption unit. I did have trouble with the ARP unit this summer. The boiler temperature sensor relocated itself and kept showing an over temp boiler on AC or DC but worked fine on propane. Just fixed it today. Hopefully all is well.

The Dometic 2663 did sometimes not relight when needed at 10,300ft, about once every two or three weeks or so. I activated the temp alarms and kept an eye on it.

As for the Roadtrek, same thing, as long as it works, it stays. I expect a NovaKool will draw less power than a compressor converted Dometic 2663 in the C but I am resisting the conversion because it works as is. The ARP has provided no problems, either.

To convert the Roadtrek to compressor I would also have 200 AH of lithium instead of 100. I have a Kisae set to charge 40 amps to the lithium from the alternator while it is also charging the FLA, 100 watts of solar, and a 60 amp charger powered by the generator. With a generator solar is trivial but handy. Fifteen minutes of generator is a days solar.

It would help to rewire the fridge power around the battery contactor. Contactor off when not in the coach but refrigerator still runs. I do that even with the low power absortion fridge. It helps.

Starlink may add as much as 10 amps of 12 volt power use so if that happens there will be other changes made with the Roadtrek.

[GallenH]

So, H, what I'm thinking is that when I'm not driving, I can replenish my 100AH AGM each day with my 100W portable solar panel. I've done it consistently when I've boondocked at Cibola near the Colorado river and also when we were in the Arches for 4 days. So if I had 200AH of Lithium dedicated solely to the fridge, I figure that would give me c.160AH which, if my fridge was drawing 50AH/day, would give me 3 days of fridge. That would be without driving or directing any solar to the lithiums.

Does that make sense?

[GallenH]

Incidentally, perhaps one thing that I haven't thought very much about is how I use the RV. Those times at Cibola and the Arches where I sit for days are not typical and probably will not be repeated. People always talk about estimating your typical use in terms of AH/day. Good practice. But it appears that while it is a great goal to be totally self-contained and replenishable, it's not always in someone's use pattern. Many people on this list talk about seeking out more comfortable camping venues where they have hookups. Perhaps a compromise is to periodically camp at campgrounds where you do have electrical and top off your batteries there knowing that the next night you will be without that external power but your 200AH will do fine with the fridge. IOW treat the Lithiums/AGMs like you would an occasional dump.

We recently drove from AZ to MN and back. Every campground, even state park ones, had electrical hookup. Once we were by a lake in beautiful scenery with spread out campsites, once in Iowa where we were the only ones there. Both had electrical. Maybe some of the trip planning could take that into consideration.

[hbn7hj]

Originally Posted by GallenH

So, H, what I'm thinking is that when I'm not driving, I can replenish my 100AH AGM each day with my 100W portable solar panel. I've done it consistently when I've boondocked at Cibola near the Colorado river and also when we were in the Arches for 4 days. So if I had 200AH of Lithium dedicated solely to the fridge, I figure that would give me c.160AH which, if my fridge was drawing 50AH/day, would give me 3 days of fridge. That would be without driving or directing any solar to the lithiums.

Does that make sense?

Yep.

Why don’t we put 200 watts on the roof? I am just spoiled by being able to get my lithium battery to 100% in less than an hour, usually less than 30 minutes. Winter travels are going to add furnace draw. I‘m running TV and DVD so I’m used to burning more power in the evening. I’ll look up the cost of 200 watts for the roof.