24v solar for Adventure Trailer

#16
If you wan't a project, go for it. But a quiet generator combined with a small lead, or lithium battery may be a better option for cost, weight, and reliability. The smaller battery can handle your smaller loads, and when you need to use your larger consumers, start up the gen. A smaller 100AH or so lithium battery and a 50A charger would be a good combo with the gen. You can run the gen a few times a day to charge the lithium battery, thus avoiding running the gen at low loads. A 100W solar panel could handle lights and phone charging.

Obviously we don't know your specific needs, so we are mostly guessing. Does your work involved computers? Power tools? How often? How long?
 
#17
IMHO A generator is going to be lighter, cheaper and take up less space at the end of the day..
I don't disagree, but I cant stand when people fire up a generator. I would certainly not want to burden someone else to have to listen to mine. I will be doing my best to avoid being next to someone with a generator and also avoiding dealing with a cranky wife if I do.

I have a Predator 3500 inverter generator that I hope to use as little as possible. I have it to run the AC unit if necessary and as an emergency back-up if I have an extended work session and Solar cant keep up.
 
#18
What kind of daily usage (kilowatt hours) are you going to see? I am just thinking about your system size. You may have a good handle on what your usage is, but often folks with less experience (not necessarily you) over/underestimate their needs.

I totally understand the generator thing. I really don't like them, but an hour a day may not be a big deal. I try to remote free camp as often as possible though.
 

dreadlocks

Active member
#19
i can hardly hear my 2200 honda inverter on the end of a 100ft extension cord when its just charging my lipo battery @ 45A, if its running aircon its a bit more audible than the aircon its self and inaudible inside the trailer.. my 100A lithium lasts me a few days and then the genny fully recharges it from 20% SOC in ~6h or so.. last campsite we stayed at the Camp Host's gas powered golf cart was louder than our genny idling a charge in.. I hadda put a charging status light in my trailer because I could not hear if the thing ran out of gas or somebody stole it.

If your at a campsite with other people, then just dont fire it up at 6am like a dick head.. Was at pikes peak hill climb this year w/my generator running 2ft away from my camper.. could not hear it over some idiots 5kva construction genny on the other side of the camp, now that was obnoxious.. I make my coffee off my battery pack and then once everyone should be up and about I'll fire up the genny to recharge my battery, usually several other people already have theirs running and since my lipo charges so fast mine is off far before theirs are.

Mebe its just the places I frequent, but 2-stroke OHV's, gunshots and many other human caused noises are far more noticable than a nice, quiet honda.. and I'd rather be in a dispersed site where I'm the only one and I find my self much less obnoxous than others do.. I camp in forests, so getting 8h+ of solid direct sunlight to recharge a lead battery is neigh impossible, im going to put ~600W of solar on my camper to cut down on my generator use but only because I have a lithium battery that can take full power til 100%, if I can get 4-6h of direct sunlight (which would be a typical best case scenario, average I'd be lucky if I get 3-4h of direct sunlight unless im in middle of desert) it should keep my battery full and minimize my genny use.. but I have a trailer with enough roof to fit 600W of solar on nice and easy.

FWIW, I use on average ~20-30AH a day of DC.. which is not much compared to most.. just a single 100AH Lithium and a Generator did me very well this summer, so much that solar is now a very low priority and might be done next season, but if not meh.. im good w/power finally and its nice having excess capacity.
 
Last edited:
#20
If you wan't a project, go for it. But a quiet generator combined with a small lead, or lithium battery may be a better option for cost, weight, and reliability. The smaller battery can handle your smaller loads, and when you need to use your larger consumers, start up the gen. A smaller 100AH or so lithium battery and a 50A charger would be a good combo with the gen. You can run the gen a few times a day to charge the lithium battery, thus avoiding running the gen at low loads. A 100W solar panel could handle lights and phone charging.

Obviously we don't know your specific needs, so we are mostly guessing. Does your work involved computers? Power tools? How often? How long?
I was originally considering building my own battery with cells as I was intrigued by the idea and the costs (I have been following Jehu Garcia on youtube for the last year and belong to Second Life Storage group on Facebook). After some consideration, I decided against it and started looking into "drop in" options like Battleborn and Renogy. Once I actually sat down to look at my needs for a REALLY graphics hungry computer, 2nd 32" monitor, Cellular boosters & antennae, lighting, along with all of the stuff the wife and kid need for homeschooling, I ended up looking at 170ah units thinking that was still smaller than I really wanted. When the option for a really solid S-module fell into my lap for $500 from a friend who is building an off-grid powerwall, I decided it was worth the effort to learn what I needed to utilize it.

I am a consultant and am deadline and "deliverable" driven. Projects vary from 1-2 days to 3 weeks in duration. I often find myself working 18 hours a day to complete a project and need to be able to do so at any given time. My work allows me to live a great lifestyle, and the expense of a robust solar / battery system with the redundancy of a Generator (if needed for "back-up") is really just "insurance" that my overlanding adventure will not impact my Professional credibility or ability to earn. I can not "not deliver" on an agreed date. I dont want to listen to a generator buzzing away while I am trying to concentrate whether at 7am, 3pm, 11pm or 3AM. I am often working at these times to allow myself the ability to enjoy life with my family during "normal" working hours.

I understand I likely will never need the capacity that the Tesla Module provides and am barely utilizing its capabilities for this fractional C system. I love the flexibility that Lithium provides and honestly would not even consider another option now. At this point, the options are to utilize a very well engineered battery module with a few additional safeguards required for safety, or spend some $$ on a 170AH Battleborn or similar.

I certainly value opinions on why I should not pursue this option, and want to hear about real life experiences with them that might dissuade me from it. I am much more interested in hearing from the people who are doing things with the lithium cells and learning about the requirements / options / safeguards etc. I value all of the opinions and information I have seen so far on this thread. I have a lot of time to plan and purchase components, then will have a month to install the system when I return to the States. Keep the info coming, I really appreciate it!
 
#21
i can hardly hear my 2200 honda inverter on the end of a 100ft extension cord when its just charging my lipo battery @ 45A, if its running aircon its a bit more audible than the aircon its self and inaudible inside the trailer.. my 100A lithium lasts me a few days and then the genny fully recharges it from 20% SOC in ~6h or so.. last campsite we stayed at the Camp Host's gas powered golf cart was louder than our genny idling a charge in.. I hadda put a charging status light in my trailer because I could not hear if the thing ran out of gas or somebody stole it.

If your at a campsite with other people, then just dont fire it up at 6am like a dick head.. Was at pikes peak hill climb this year w/my generator running 2ft away from my camper.. could not hear it over some idiots 5kva construction genny on the other side of the camp, now that was obnoxious.. I make my coffee off my battery pack and then once everyone should be up and about I'll fire up the genny to recharge my battery, usually several other people already have theirs running and since my lipo charges so fast mine is off far before theirs are.

Mebe its just the places I frequent, but 2-stroke OHV's, gunshots and many other human caused noises are far more noticable than a nice, quiet honda.. and I'd rather be in a dispersed site where I'm the only one and I find my self much less obnoxous than others do.. I camp in forests, so getting 8h+ of solid direct sunlight to recharge a lead battery is neigh impossible, im going to put ~600W of solar on my camper to cut down on my generator use but only because I have a lithium battery that can take full power til 100%, if I can get 4-6h of direct sunlight (which would be a typical best case scenario, average I'd be lucky if I get 3-4h of direct sunlight unless im in middle of desert) it should keep my battery full and minimize my genny use.. but I have a trailer with enough roof to fit 600W of solar on nice and easy.

FWIW, I use on average ~20-30AH a day of DC.. which is not much compared to most.. just a single 100AH Lithium and a Generator did me very well this summer, so much that solar is now a very low priority and might be done next season, but if not meh.. im good w/power finally and its nice having excess capacity.
I cant say I have any experience with Generators and quite honestly the whole idea is new to me. We have been tent campers our whole lives and tend to stay in tent only campsites and sites where generators are not allowed. So, while I appreciate your experience and acceptance of them, it is hard for me to want to rely on them.

The whole BLM options out west are completely foreign to me. I dont even know the regulations / protocol for Generator use out there. We are also "tent camping" still, just a little higher off the ground. We aren't in a trailer to help attenuate the sound. My wife struggles with migraines sometimes so I would like to be able to avoid anything that makes her uncomfortable. She is a sport for putting up with my madness (and my crazy 8YO boy).

I like that the extra capacity might allow us to go a few days between charging (PV or Genny) and that Lithium likes to be charged hard and fast. I would like to understand more about the 3500w generator and the best way to charge with it. I have a reasonable understanding of Solar Charge controllers as they relate to Lithium, but what are people using to make a connection from the Generator or Shore Power connection?

Though I am interested in the potential for charging from the vehicle with a DC/DC charger, I think I will likely spend some time on the road without it to see if I think the investment would be warranted.
 
#22
Given the cost of setting this system up right, solar controllers, wiring , safety bits, you need to have a fulled defined plan, and system design before you jump in. Obviously you understand this. The first step is to make a electrical usage budget, and define your usage case(s). How long will you drive? What kinda power do your systems use? How long is your worst case scenario? Once you get this firmed up, then you can assess if the telsa module is a good fit and worth the effort to build into your system. You may find that 2 or 3 kwhr of storage is more than enough when combined with a DC-DC and some solar. Or you may need 5 or more kwhr.

Have you put a watt meter on your computer(s)? My modeling PC uses between 200-500W depending on load. LED backlit monitors are usually less than 60W.

Flat mounted solar modules combined with seasonal various can dramatically alter their output. In some cases my 640W array only makes 1.1kwhr a day over a 3-4 day period.

useful calculator here.
https://pvwatts.nrel.gov/
 
#23
Given the cost of setting this system up right, solar controllers, wiring , safety bits, you need to have a fulled defined plan, and system design before you jump in. Obviously you understand this. The first step is to make a electrical usage budget, and define your usage case(s). How long will you drive? What kinda power do your systems use? How long is your worst case scenario? Once you get this firmed up, then you can assess if the telsa module is a good fit and worth the effort to build into your system. You may find that 2 or 3 kwhr of storage is more than enough when combined with a DC-DC and some solar. Or you may need 5 or more kwhr.

Have you put a watt meter on your computer(s)? My modeling PC uses between 200-500W depending on load. LED backlit monitors are usually less than 60W.

Flat mounted solar modules combined with seasonal various can dramatically alter their output. In some cases my 640W array only makes 1.1kwhr a day over a 3-4 day period.

useful calculator here.
https://pvwatts.nrel.gov/
I do know the consumption of my Laptop is right around 300W and the monitor is another 50W +/- I had used some calculators a while back to figure out that I felt a 100AH battery was not nearly enough and a 170AH though better was still lighter than I would like. I'm happy to get into it again, but I think I am past that point quite honestly.

My current drivers:
  • I have access to a Tesla module in great shape for less than 50% of the market value and likely less than I could pick up a "drop in" option with 1/5th the capacity.
  • Using the Tesla Module is driving me toward a 24V system and I feel that I am comfortable with both the advantages and disadvantages of going 24v
  • I have the real estate to mount (1) 300W 24V panel flat on the Jeeps Pioneer roof rack. I am looking at options to store the 2nd panel in slides under the rack or in slides under the rooftop tent for deployment when camp is set-up. There is no possibility I will run more than the 2 panels (600W). I plan to fabricate a system that will allow the removal of the panels to be placed at camp with the trailer when I need to work and the family takes off on me.
  • I would need a good Solar Charge Controller whether going with a 100Ah BattleBorn or the Tesla Module. I understand I may pay more for one with the ability to adjust the parameters to work best with the Tesla Module. I'm fine spending the money here. From what I have researched, I like Victron offerings but want to look into Sterling.
  • I have a fairly robust 3500w inverter generator - I am interested in the most efficient way to charge the battery with this unit when I need it due to lack of PV input.
  • DC/DC while driving is something I would like to consider down the road as an add option if it looks worthwhile based on our lifestyle.
  • I figured I would use a Victron Battery protect to protect against over discharging.
There have been some great recommendations here for over charging protection which I intend to incorporate (monitors and relays). I understand the need to watch temps and maintain balance and have no problem incorporating this. It makes sense to me and seems easy enough. (I used to balance charge 3S Lipos for RC racing)

So I am happy to run some calculators if one feels I should, but I would much rather design something that is more than I need than "maybe almost enough to meet my needs if I am careful...."
 
#24
If you are set on going big, that's fine. The engineer in me would prefer to know what you have and what you need. Which usually means some basic math. That way you know how many days you can go with/without solar, how fast you can recovery the average days usage etc. You are building a complete system, and there are few skilled professionals that would build a similar system without crunching the numbers.

So you plan on charging from the gen if the sun goes away for a bit. That's part of the detailed usage cases I was describing. It is very difficult to give good advice without all the information.

Figuring out your peak charge rates is necessary to determine your cell balance needs. Higher rates mean more balancing current. Though if you stay out of the knee at above 98%, your balance current drops pretty quick. Nothing wrong with 24V, you just cut your wiring sizes by half, and choose components that are 24V. Lots of boats, big RVs, and small aircraft use 24V, so finding parts won't be hard.

Knowing your peak current (charge and discharge) is necessary for choosing wire sizes, inverter capacities etc.
 
#25
If you are set on going big, that's fine. The engineer in me would prefer to know what you have and what you need. Which usually means some basic math. That way you know how many days you can go with/without solar, how fast you can recovery the average days usage etc. You are building a complete system, and there are few skilled professionals that would build a similar system without crunching the numbers.

So you plan on charging from the gen if the sun goes away for a bit. That's part of the detailed usage cases I was describing. It is very difficult to give good advice without all the information.

Figuring out your peak charge rates is necessary to determine your cell balance needs. Higher rates mean more balancing current. Though if you stay out of the knee at above 98%, your balance current drops pretty quick. Nothing wrong with 24V, you just cut your wiring sizes by half, and choose components that are 24V. Lots of boats, big RVs, and small aircraft use 24V, so finding parts won't be hard.

Knowing your peak current (charge and discharge) is necessary for choosing wire sizes, inverter capacities etc.
Gotcha. I appreciate the input and the help. I'll prepare some info....
 

dreadlocks

Active member
#26
get a 100ft 10awg extension cord from HF and its far enough away that even in a tent it will be far more tolerable, stuff it behind a rock or tree and it makes it real quiet.. you already got the genny, put it to use.. I recently converted from tent camping and camped at tons of sites and almost never found a camp that didnt allow genny use in the day time.. yeah they all restrict hours of operation and some may require them to be the quieter ones but outright genny bans are fairly rare outside national parks.. now that you got a trailer those tent-only sites wont be welcoming you anyhow and most camps that allow trailers will allow gennys.. Ive even had night time bans lifted because sub freezing temps were going to run everyone's furnaces all night and most people were gonna wake up with a dead battery w/out electricity.

If your in national forest land you can camp anywhere you want, no quiet time.. run it all night long if you want, if there is anyone nearby the'll be several hundred yards down the road and wont hear a thing.. plenty of room to take that extension cord to its limit.. however having data signal for work is going to be the harder part, if your planning on working your going to need to stick somewhat close to civilization.

I'd also look into a newer computer, a new i5-9600K complete system can draw less than 50w idle, less than 100W w/single threaded tasks, and less than 150W fully loaded.. and it outperforms most previous generation i7 CPU's.. monitor power also goes up exponentially with size, so go with the smallest size you can tolerate.. yeah a 30in might be great, but a 22in might be half the power load and far more practical.. Solid state drives use virtually no power compared to spinning disks, so thats another thing to consider.

and I agree, you needa determine your base loads before you start throwing a ton of money into this or you could end up in a terrible position.. Calculators are great and all but nothign beats real world testing, get your self a watt-o-meter, both AC and DC versions.. run each appliance for 24h in typical environmental conditions and figure out how much power they draw a day, then add up all your appliances and that is your minimum budget..

yeah that tesla battery is gona be cheap, but how much is a 24v charger adequate for it gonna cost (I got a 630w AC charger for my 100A Lithium, your gonna want a few thousand watts to quickly charge that thing)? you should also be looking past 24v solar.. Panasonic HIT is what i'mna be using its like 65v, the MPPT controller will gimme the charge voltage I want.. Also hooking up a undersized solar and undersized AC charger up to a very large bank is totally ass backwards and leaving much of the Lipo benefits on the table when it takes several days of no usage to get it back up to full.. its a much better position to be in with oversized charging sources for your battery bank, especially solar since you almost never get its full rated outputs.. if 650W of Solar and/or AC is the sweet spot for my single 100AH battleborn, neither are going to be near adaquate for a lithium system several times its size/capacity... If you do really need that capacity, you may end up using that generator far far more than you ever wanted since your never going to get enough power to keep the Tesla batteries in good shape otherwise.. then your right back where you started, just with alot less money and room.

When I jumped to Lithium Batteries, the capacity I needed actually went down in the real world.. I needed far more capacity with lead weights because the batteries charged so slowly, charge/discharge effencies were terrible and variable with larger loads.. with lead 24h at 10A does not equal 12h at 20A, you'd be lucky to get 8h.. then a vast majority of the capacity was untouchable or else id risk junking the batteries.. I was planning for >300AH of lead and concerned I may need more still, but with Lithium 100AH is quite sufficient for me.. since I can charge it up in a few short hours, instead of all damn day it means I dont need as much capacity as I would otherwise, now running generator daily for a couple hours is no big deal, and there is no pressure on me to get it back to 100% SOC.. its far better than lead where you gotta run it all day because its gotta soak in absorb mode and the things dont last if you let leave em partially charged for days on end.
 
Last edited:

dwh

Tail-End Charlie
#27
You will need an inverter. Also a charger. So maybe you should get an inverter/charger. But they aren't cheap (or small). Look at Xantrex, Magnum or Samlex.

Very few standalone chargers (or the charger section of an inverter/charger) will put out over 50a@24v to the battery. Your 3500w gen is basically capable of 30a@120v, which roughly translates to 300a@12v. So you could run 4x50a@24v battery chargers and still have ~1,000w left over to run the computer.


I'd look at a samlex 2224. 2200w sine wave inverter, programmable 70a charger. Has separate AC inputs for grid and gen. Also has an input to allow a feed into the the system from the solar charge controller. Also has an optional remote head unit that can datalog to an SD card.


http://www.samlexamerica.com/products/ProductDetail.aspx?pid=574
 
#28
get a 100ft 10awg extension cord from HF and its far enough away that even in a tent it will be far more tolerable, stuff it behind a rock or tree and it makes it real quiet.. you already got the genny, put it to use.. I recently converted from tent camping and camped at tons of sites and almost never found a camp that didnt allow genny use in the day time.. yeah they all restrict hours of operation and some may require them to be the quieter ones but outright genny bans are fairly rare outside national parks.. now that you got a trailer those tent-only sites wont be welcoming you anyhow and most camps that allow trailers will allow gennys.. Ive even had night time bans lifted because sub freezing temps were going to run everyone's furnaces all night and most people were gonna wake up with a dead battery w/out electricity.

If your in national forest land you can camp anywhere you want, no quiet time.. run it all night long if you want, if there is anyone nearby the'll be several hundred yards down the road and wont hear a thing.. plenty of room to take that extension cord to its limit.. however having data signal for work is going to be the harder part, if your planning on working your going to need to stick somewhat close to civilization.

I'd also look into a newer computer, a new i5-9600K complete system can draw less than 50w idle, less than 100W w/single threaded tasks, and less than 150W fully loaded.. and it outperforms most previous generation i7 CPU's.. monitor power also goes up exponentially with size, so go with the smallest size you can tolerate.. yeah a 30in might be great, but a 22in might be half the power load and far more practical.. Solid state drives use virtually no power compared to spinning disks, so thats another thing to consider.

and I agree, you needa determine your base loads before you start throwing a ton of money into this or you could end up in a terrible position.. Calculators are great and all but nothign beats real world testing, get your self a watt-o-meter, both AC and DC versions.. run each appliance for 24h in typical environmental conditions and figure out how much power they draw a day, then add up all your appliances and that is your minimum budget..

yeah that tesla battery is gona be cheap, but how much is a 24v charger adequate for it gonna cost (I got a 630w AC charger for my 100A Lithium, your gonna want a few thousand watts to quickly charge that thing)? you should also be looking past 24v solar.. Panasonic HIT is what i'mna be using its like 65v, the MPPT controller will gimme the charge voltage I want.. Also hooking up a undersized solar and undersized AC charger up to a very large bank is totally ass backwards and leaving much of the Lipo benefits on the table when it takes several days of no usage to get it back up to full.. its a much better position to be in with oversized charging sources for your battery bank, especially solar since you almost never get its full rated outputs.. if 650W of Solar and/or AC is the sweet spot for my single 100AH battleborn, neither are going to be near adaquate for a lithium system several times its size/capacity... If you do really need that capacity, you may end up using that generator far far more than you ever wanted since your never going to get enough power to keep the Tesla batteries in good shape otherwise.. then your right back where you started, just with alot less money and room.

When I jumped to Lithium Batteries, the capacity I needed actually went down in the real world.. I needed far more capacity with lead weights because the batteries charged so slowly, charge/discharge effencies were terrible and variable with larger loads.. with lead 24h at 10A does not equal 12h at 20A, you'd be lucky to get 8h.. then a vast majority of the capacity was untouchable or else id risk junking the batteries.. I was planning for >300AH of lead and concerned I may need more still, but with Lithium 100AH is quite sufficient for me.. since I can charge it up in a few short hours, instead of all damn day it means I dont need as much capacity as I would otherwise, now running generator daily for a couple hours is no big deal, and there is no pressure on me to get it back to 100% SOC.. its far better than lead where you gotta run it all day because its gotta soak in absorb mode and the things dont last if you let leave em partially charged for days on end.
Thanks for the detailed response - Much appreciated.

As discussed, this type of camping is new to us. Your suggestions all seem to make sense and I am sure I will settle in to some acceptable generator use. Our goals are to spend as many nights off the grid on BLM (or similar) land as possible. When I see that I may have to hunker down for work for extended periods we will likely look for accommodations in areas that provide more amenities and the ability for the family to explore / road school without me.

While I certainly understand the typical approach to running calculations to figure out what makes the most sense for your use, I am looking at this from a little different mindset. One of the things that has attracted me toward Lithium is the thought that once the system is set up properly and have safeguards in place, it is pretty flexible in the way you use that power. More importantly, I understood it to be more flexible in how you REPLACE that power. That being the case, I did not understand that potentially over-sizing my storage capacity would be very detrimental.
  • I dont really know how I will utilize the system, as we have never done this before. I may be in a position to charge every day with the Genny if PV is not keeping up, I may be so focused on work or working during inclement conditions that I would prefer to not deal with running Generator. We may decide to break camp early and roll to take advantage of a lull in work or weather opportunity to run a trail we have our eyes on. I may decide not to deploy the 2nd PV panel because we have to move quickly the next day.
  • I know I need to ensure I have enough power to satisfy my professional needs. If I'm in a position where we have inclement weather and generator dies, having the reserve capacity to stay put and finish a project could be a really big deal to me. That could be 2-3 days.
  • My wife suffers from migraines and often needs to recharge with a nap. Having a system with some buffer that might allow us to run the AC unit for an hour would be nice. She is also more inclined to need to turn on the AC in the middle of the night (hot flashes). If we had the capacity to handle an hour of AC at night without having to get up and start the generator for her, I would REALLY appreciate that.
Please don't think I want to just slam this together without doing my due diligence or learning. I am happy to provide all of the information that you all are looking for in order to help me learn / participate. I can go through calculations if you like but had done this early on and figured 100ah wasn't enough and began to look at 170ah of storage.

A couple of specific thoughts / responses:
  • Panasonic HIT panels - Those look great! Almost all of the attributes make them look like the perfect panel for my use. How would I handle the high voltage? Would the MPPT optimizers be required to connect to a Solar Charge controller capable of handing 48V?
  • I would certainly be open to paying 2x as much for less than 1/2 the capacity if I felt I was causing damage to the Tesla Module. Am I misunderstanding their ability to be a bit laxed with charging? I understood this as a major advantage to the Lithiums and one that might allow me some flexibility in how fast / when I charge (I do understand they offer the ability to charge at significant rates, but did not understand that charging at slow rates was necessarily detrimental to the health of the battery).
  • I have been looking for some feedback on the best charger to consider for my 3,500w generator or typical 30A or occasional 50A shore power, with the understanding that I would gladly pay more for the ability to charge as quickly as possible when the opportunity arises. Spending $500 or more on a charger is not a concern if it offers more control of my ability to manage this system.
  • I have an 18" laptop monitor and (2) 42" monitors in my office to be efficient. I travel with my laptop and a 32" monitor and that makes me less efficient. If I could bring a 50" monitor with me I would. After 25 years looking at a computer, my eyes are suffering. I dont want to start looking at replacing my $3,500 laptop at the moment.
Hope I'm not repeating myself or appearing to not want to deviate, just trying to identify what is motivating me. Thanks again for the input.
 
#29
There is really no downside to oversizing a lithium bank other than space/weight used, and some longevity loss. Lithium banks get longer lives the lower their average SOC is. SO oversizing and still charging to 100% means the bank will spend more time at high SOC. If your charging is marginal is not an issue. Down to a point, The last few percent of capacity does a bit more wear on the bank. Essentially they can be infinitely cycled in the mid range of SOC. There is one gotcha. The cells will naturally have some variance in efficiency and capacity. So every 2-10 cycles you need to get the bank into the mid 90s soc for a few minutes while charging. This allows the balancers to bring all the cells up to the same SOC. If this doesn't happen, eventually one of the less efficient cells will drift down in SOC compared to the others. So the whole bank could be at 20% SOC, but one cell is down near 5%. At which point the BMS could drop the bank out to protect that one cell (or cell group).

I don't know if you need the power to run without gen or solar for 3 days or not. Thats a call you need to make. You could always move to a camp with electrical hookups.

putting a 1800w charger on the bank makes sense. Larger works with the 3500w gen, but make sure it can be de-rated to run from a 15A oulet, as those are often available at camps with marginal hookups.


What is the capacity of this 1/2 Tesla bank you are looking at? Number of cells? How are you going to wire them? How many parallel strings?

If you aren't going to use your work computer very often, then a larger bank would be okay with 600W solar. If you are using that computer setup often, a 600W setup is going to struggle meeting your needs in non-optimal conditions.
 
#30
You will need an inverter. Also a charger. So maybe you should get an inverter/charger. But they aren't cheap (or small). Look at Xantrex, Magnum or Samlex.

Very few standalone chargers (or the charger section of an inverter/charger) will put out over 50a@24v to the battery. Your 3500w gen is basically capable of 30a@120v, which roughly translates to 300a@12v. So you could run 4x50a@24v battery chargers and still have ~1,000w left over to run the computer.


I'd look at a samlex 2224. 2200w sine wave inverter, programmable 70a charger. Has separate AC inputs for grid and gen. Also has an input to allow a feed into the the system from the solar charge controller. Also has an optional remote head unit that can datalog to an SD card.


http://www.samlexamerica.com/products/ProductDetail.aspx?pid=574
Nice! This is very helpful. I will look into this unit or comparable units by the other MFR's. My early look into inverter / chargers were pointing me toward components for much larger off grid home systems. The cost seems reasonable considering that it would replace 2 components I would have to buy anyway, but for less money would be lacking on the ability to charge quickly.

Form factor looks great. A bit hefty at 60 lbs but not too bad considering the Tesla Module is only 55lbs...

So, this unit would take advantage of the power output of the 3,500w generator (something i have not wrapped my head around yet)?

Would this unit be programmable to the parameters preferred for Lithium vs more traditional Lead Acid or Gel type batteries?

Going to start looking into these as an option.....
 
Top