Power systems (fuel) - help me decide

[luthj]

Now, if you did let things freeze over, and used the lithium route, would that in itself cause damage to the batteries so long as you warmed them up prior to charging? Of course that means you would either need to use them to run the diesel heater, or get the genset going for a hour or so until the interior and cubbies are warm.

Lead can definitely work for your usage, its just a matter of balancing the total system cost and performance.

Lithium batteries can be safely discharged at low temps, usually down to -20C. Storage use usually a bit lower than that. Some cells will see damage if allowed to drop to very low temps. Lead can also freeze if allowed to discharge below 50% in very cold weather as well.

Any good lithium install will have a BMS that manages charge/discharge cutoffs, and will prevent damage due to high/low temps. There is a bit of a learning curve so its not as simple as lead.

 

[Joe917]

What is your base vehicle and what is the habitat? level of insulation? Seems like draining the water is the best bet. A hydronic diesel heater will warm things back up in no time.

 

[luthj]

With some careful planning its possible to design a water system that will drain well enough to handle a freeze. At least without blowing out all the lines.

 

[Chorky]

Lead can definitely work for your usage, its just a matter of balancing the total system cost and performance.

Lithium batteries can be safely discharged at low temps, usually down to -20C. Storage use usually a bit lower than that. Some cells will see damage if allowed to drop to very low temps. Lead can also freeze if allowed to discharge below 50% in very cold weather as well.

Any good lithium install will have a BMS that manages charge/discharge cutoffs, and will prevent damage due to high/low temps. There is a bit of a learning curve so its not as simple as lead.

Yes exactly correct. I do like the lithium idea because of many reasons. But I'm just not sure for my particular case it's the better way to go. I suppose I could attempt the led route, being cheaper, and if it proved not to work well could swap to lithium. Would the charging components be different? I seem to recall recently reading on another thread that the charging managers for lithium setups being specific to lithium batteries.

What is your base vehicle and what is the habitat? level of insulation? Seems like draining the water is the best bet. A hydronic diesel heater will warm things back up in no time.

I have a '97 F350. But this setup would be going in a 15-24' cargo trailer converted to a nice (not 'basic') full time, long term, livable space capable of significant travel (mostly due to work situations). The insulation level is not known yet, but the plan would be for the standard 1 or 2" walls based on trailer framing studs, but with additional 1-2" framing and insulation to add thickness, insulation factors, and a variety of other reasons.

With some careful planning its possible to design a water system that will drain well enough to handle a freeze. At least without blowing out all the lines.

I have been thinking about this a lot lately actually. It wouldn't be too difficult either, just would have to make sure that the low point drains are actually lower than the rest of the system, and make sure water tanks are tilted correctly to not have any puddles remaining. A few small spoon full amounts here and there probably wouldn't cause any damage. But a cup full certainly could.


Any of you here also run a diesel genset?

 

[grizzlyj]

Would the charging components be different?

Some manufacturers say not, and some don't produce lithium specific chargers anyway. But have you read shade's link in post 31 above?

 

[shade]

Would the charging components be different?

We were discussing this in another thread.

Basically, if you have a good LFP setup with the ability to program it, the same system could be used with a lead battery. Here's what I'm doing, and it would work well with a variety of battery chemistries due to the flexibility of the programming. Otoh, a system built for a lead battery may not be able to work well with an LFP battery. It really depends on the programmability of the charge sources more than anything else.

 

[luthj]

Most charge sources aren't adjustable enough for lithium packs. Mostly due to float and absorb logic. Its not a simple yes/no answer though.

Don't mistake a "lithium" profile name for being usable. Know and understand the feed/care needs for lithium before making choices in that area.

 

[Chorky]

We were discussing this in another thread.

Basically, if you have a good LFP setup with the ability to program it, the same system could be used with a lead battery. Here's what I'm doing, and it would work well with a variety of battery chemistries due to the flexibility of the programming. Otoh, a system built for a lead battery may not be able to work well with an LFP battery. It really depends on the programmability of the charge sources more than anything else.

View attachment 545563

Ha its funny you just posted this because I just spent the morning reading your whole other thread! Pretty slick system you have planned. I was hoping I guess that there could be a simpler system, and less costly too be honest. However, this is great info, and following your other thread. That video on page 3 was also enlightening. I'm surprised that's the case half the time. Why build an alt to push more power than it's capable of running.... It also gives me more desire to want to run a genset for big charging when solar isn't going to work (like in winter). Especially since my big battery draws will mostly be in a trailer, and considering if I have other fuel based components (whether diesel or gas/lp) then having a larger amount of fuel storage and auto gen starting would probably be a good way to go.

But, I also plan a battery system for the truck to run truck related gear such as compressors, a small fridge just for beverages or long drives from the grocery store, a water pump, some 'work' lights, radios, etc... So in that case, I'm wondering if a DC/DC charger with a small single solar panel would be better in the end than just a battery isolator. Possibly to reserve maxing the alternator only when needing heavy winching pulls, and also add the capacity to have an on board charger to maintain batteries after heavy use from a standard wall outlet. **(Dual batteries factory for the truck, but probably need dual batteries in the bed for the truck equipment)** It would appear I'm dusting off the surface of a really deep hole that needs to be dug haha.

I'm still just not sold on lithium for my application too though. Yes they may be a better option because of charging and discharging capacities, but for my particular situation of an absolute necessity of full automation while gone for extended periods of time - I'm concerned that lithium is just too finicky for that.

 

[Alloy]

I have been thinking about this a lot lately actually. It wouldn't be too difficult either, just would have to make sure that the low point drains are actually lower than the rest of the system, and make sure water tanks are tilted correctly to not have any puddles remaining. A few small spoon full amounts here and there probably wouldn't cause any damage. But a cup full certainly could.

Did it on our trailer but it has only been tested down to 10F so far. I'm hoping to get it down lower this year.

All Upunor PEX water lines are slopped toward the low point drains. Valves for the low point drains are in heated space with the PEX running out the bottom.

Tanks (2-90gal) are insulated with 2" XPS and sloped 1/4" per foot with drains out the bottom. Tank drains are 3/4" x 6" polyethethlyne pipe plugs that run inside 1 1/2" PVC pipe. The 1 1/2" PVC is glued into the 2" XPS insulation to prevent water that is draining from the tanks from flooding the tank compartments.

 

[shade]

Most charge sources aren't adjustable enough for lithium packs. Mostly due to float and absorb logic. Its not a simple yes/no answer though.

Don't mistake a "lithium" profile name for being usable. Know and understand the feed/care needs for lithium before making choices in that area.

Very true. Many "lithium" capable chargers use voltages that border on abusive for LFP batteries, with no ability to manually adjust them.

One of the reasons I started paying attention to Victron gear was for their firmware updates that allow the products to become more capable over time. I also think having control over the programming is important for the long term viability of a charger, since new chemistries may perform better using parameters that aren't even considered today. Research can also change charging recommendations over time. For example, Winston used to recommend a cell balancing voltage of 3.8V/15.2V, which is now considered far higher than necessary.

 

[shade]

I'm still just not sold on lithium for my application too though. Yes they may be a better option because of charging and discharging capacities, but for my particular situation of an absolute necessity of full automation while gone for extended periods of time - I'm concerned that lithium is just too finicky for that.

It's not for everyone. I know LFP based systems are used in situations like you described, though. Victron offers remote monitoring if there's cell signal available, and I think the system can be controlled remotely, too. I haven't looked into it since that's not a point of interest for me, but it's a very useful capability.

 

[Alloy]

I'm still just not sold on lithium for my application too though. Yes they may be a better option because of charging and discharging capacities, but for my particular situation of an absolute necessity of full automation while gone for extended periods of time - I'm concerned that lithium is just too finicky for that.

I was at the same place 2 years ago. Since then the battery protection has improved allot.

Having a reliable heating system is the key.

If I was building from new all the heat ( battery/ floors / HW) would be hydronic with a back up.

Availability of diesel makes it apealling but it has a high Ah load vs. a household propane boiler doesn't..... so maybe both.

 

[Chorky]

It's not for everyone. I know LFP based systems are used in situations like you described, though. Victron offers remote monitoring if there's cell signal available, and I think the system can be controlled remotely, too. I haven't looked into it since that's not a point of interest for me, but it's a very useful capability.

Watched the video, that is pretty darn cool!! But I'm often in areas with no cell coverage, so there is that too.

I was at the same place 2 years ago. Since then the battery protection has improved allot.

Having a reliable heating system is the key.

If I was building from new all the heat ( battery/ floors / HW) would be hydronic with a back up.

Availability of diesel makes it apealling but it has a high Ah load vs. a household propane boiler doesn't..... so maybe both.

Yeah and that right there is the problem. If you go the LP route, you of course have more volatile fuel, heavier weights, less BTU. If you go diesel, you have higher AH requirements.

One question to be answered would be the realistic AH values used by a diesel air/water heater over a 24 hour time in -10 to +15 degree temps. After all rated specs and real life can be quite different.


Taken from shade's other thread he has going:
QUOTE="dreadlocks, post: 2693932, member: 191280"]
yeah Ive had my genny through both FLA and then w/LFP.. I hated it with FLA, running the engine for a few measly amps during absorb is a huge waste of fuel and takes forever.. at idle the genset is discarding a ton of energy.

With LFP I like it much more, just an hour is really all I need if I'm entirely engine dependent.. and there is no pressure to ever get it back to 100% (unless you loose SOC calibration lol).. with my ~50AH a day usage, and my 40A shore charger.. I only need an hour of runtime and I've got ~40AH back in.. if I run it for half an hour I get ~20AH back in.. If the sun is setting and I'm not where I want to be w/my SOC, its very minimal genny time to get me back to where I want to be.

For those going off an alternator w/LFP, just a half hour to an hour drive every day may be all you really need.. and IMO thats pretty easy to achieve unless you just like parking in one spot for weeks on end w/out moving an inch.
[/QUOTE]

I also agree with this that using genset to charge acid batteries are not optimum at all. As I recently found out within the last 6 months via others on this forum, the amount of time required to recharge AGM batteries even just from a 24 hour use is extensive due to the slow charge rate. Which is why lithium is so desirable.

There in again is the ongoing argument I have with myself....
Stick with LP, the easy route, but heavier and significantly less BTU's
Go diesel for higher BTU and larger fuel storage capacity
and
stick with acid - easy, cheap (in the short run) but relatively simple
go with lithium - expensive, 'better' but more finicky and possibly risky for my situation


Food for thought someone also mentioned on another thread, somewhere, they saw a led battery freeze at +10F. No doubt I will see significant days of below zero this winter. That's going to be tough enough to get the truck to start ha!


At some point I am going to just have to pull the trigger and go with a decision - and in all reality it will likely be a middle of the road cheaper side of the options due to life realities. But, still want to iron out ALL the good/bad of all possibilties.

 

[luthj]

Espars ratings for their air heaters and hydronic heaters are very accurate. The D2 uses about 1.8A on high power, the D4 uses about 3.5A. The hydronic heaters have the water pump, and are a bit higher, especially if you need an interior blower. You can basically work out AH per kW-hr as a good average figure. Then you can estimate your heating needs in kW-hr (or BTU), and work out electrical power needs.

 

[shade]

Food for thought someone also mentioned on another thread, somewhere, they saw a led battery freeze at +10F. No doubt I will see significant days of below zero this winter.

Whatever house battery chemistry you select, you'll want an insulated battery box with some type of automated heating circuit for when it's unattended for weeks. Yea! Another project within a project.