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travellerw
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# Posted: 21 Jun 2025 11:42am
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I took a quick look at the manuals for your devices. Based on the manuals it looks like the Inverter and MPPT controller would work with LFP batteries.
The MPPT controller has fully adjustable voltages in "User" mode.
The inverter has a wide enough voltage range to work! However, the low voltage shutoff may not work. That not a huge deal as the BMS on the batteries will protect them.
The battery charger is the problem. It could still be used if you monitored it closely. I wouldn't trust it in automatic mode though. I also would not let it float the batteries. If you added a Victron BMV-700 to the system then you could use that while using the charger. The BMV-700 will tell you the state of charge so you can shut the charger down long before you get to %100 and voltages that aren't good for LFP. Not an ideal solution but it can work (I did a similar thing on one of my systems for 3 years).
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gcrank1
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# Posted: 21 Jun 2025 11:51am
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As a back-up charge plan (which I have yet to use) Id run the gen 1/2 to 1 hr of a morning to power the ac charger and top up from overnight usage. At that I dont think Id have to keep much of an eye on it.
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MtnDon
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# Posted: 21 Jun 2025 11:51am - Edited by: MtnDon
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We used GC-2 golf cart batteries from Sam's Club when we built our first system. They lasted 9 years with gentle use. Much better pricing than Trojans at the time.
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FishHog
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# Posted: 21 Jun 2025 02:44pm
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Even trojan batteries will die fast if your undercharging them daily. If your going to do something to get by for a year, go with the cheapest deepcycle batteries you can find. Or spend the time, make sure your batteries and charging system are the proper size for your needs and spend the money once.
All your usage items will have a power spec. Do an energy audit based on that and your best guess at use. Its not that hard and then you will know if you have the right size and just a bad batteries or if your under sized and killing your batteries.
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groingo
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# Posted: 21 Jun 2025 06:36pm
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Best advice, keep it simple, looks like you already have the tools, inverter, charge controller, I would do an energy consumption test to see what is using how much juice then double the result and build around that. For cooking I would go with Propane or wood, refrigeration...try to avoid go with canned food or freeze dried, vacuum cleaner....oh hell no, get a good broom! Like I have learned, "Electricity is NOT your friend, find work arounds wherever you can, that is half the fun!
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Brettny
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# Posted: 21 Jun 2025 06:42pm
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My system is built with Sam's club GC2 batteries..and two other brand ones i added a year later. For the WH that your paying for lithium is the way to go. Lead acid batteries really need to be 50% the cost of lithium to even break even and there definitely not that cheap. Lithium can take alot of amps until there nearly full. Lead acid need a longer slower charge, this really sucks in winter.
You may find that just getting the same WH lithium battery will suit your needs. And if not add another, if still not add another.
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zorro
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# Posted: 28 Jun 2025 03:54pm
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Thanks for all the info guys much appreciated
I am trying to understand as much as possible, though not succeeding too well I feel
So my batteries are essentially dead - it was 8 x 6v/235ah (11280WH) in a 24v set up ( lead acid)
Next year I will do a full assessment of my system and plan a major upgrade
For this year I just need to get something up and running
I plan on moving my panels (3x340W) to a better sunnier position
So a question
Would these work for me set up in a 24V system) seem to get reasonable reviews
4x12.8V/280ah (14336wh)
https://shorturl.at/7p7sN
And using this charger from the generator to top them up as needed
https://shorturl.at/nmQBE
Would this work to at least get me through this year?
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gcrank1
Member
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# Posted: 28 Jun 2025 06:07pm
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I see nothing (did I miss it?) in that about them being 'series capable', only parallel. And Id want that in writing not just 'yeah sure' from a csr on the phone.
That charger looks to be a Trickle Charger; ie, to me the supposed 20a may start there then kick back to a lower amps after what, maybe 10-15min?
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zorro
Member
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# Posted: 28 Jun 2025 06:28pm
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I need to check on the series connection potential - good point
And I missed that the charger was a trickle charger - that will not work for what I need
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zorro
Member
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# Posted: 28 Jun 2025 06:50pm
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Some info here
Yes, you can connect Eco Worthy lithium-ion batteries in series, but with some important considerations. Eco Worthy's BMS (Battery Management System) typically allows for up to 4 batteries in series. Connecting them in series increases the voltage of the battery bank. For example, four 12V batteries connected in series will create a 48V system
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gcrank1
Member
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# Posted: 28 Jun 2025 09:28pm
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Do a DEEP search online for user experience with that (or any brand) you are considering. And watch out for 'reviews' that are really done by shill for the company.
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zorro
Member
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# Posted: 28 Jun 2025 09:50pm
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So in theory (once I do a bit more research), these 8 batteries should work for me?
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Brettny
Member
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# Posted: 29 Jun 2025 06:48am
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You would be almost doubling your battery capacity with those lithium batteries. I wouldnt worry about the 120v charger until you use the system a bit. 20a charger with no transfer switch is prety small and that charger may not do 20a continuously. You have to consider any useage off the battery is going to be taken away from the chargers ability to charge. So if your charger is 20a and your useing 5a your only really putting 15a into the batteries. With a transfer switch all the load of the inverter would be transferred to the generator so the charger would be putting 20a into the battery. Inverter chargers do this automatically. Very few inverters do this.
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gcrank1
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# Posted: 29 Jun 2025 08:35am
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Rule of thumb changing to LFP is that for a given AH bank size you can have half as many than LA (since you can/should only use 1/2 the AHs of LA).
Even at that you may want to expand the array, or in your case where you weren't keeping up with the LA you Need to expand.
Now if you want to expand your bat-bank AHs/Wts you def, without a doubt, Need to expand the array.
So I'd do 2 big LFP 12v to series into 24v (the size and weight would be more manageable than 1 Huge 24v) with always the option to add more (you dont have to age match LFP) and look at adding more array (panels are cheap now) even iff you need to get another SSC, not for All the array but to make separate units to feed the bat-bank (you can charge from multiple sources).
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zorro
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# Posted: 29 Jun 2025 10:45am - Edited by: zorro
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Interestingly, the charger I already have seems to do 24v and lithium
https://shorturl.at/YkbDG
Large charging capacity design (75 Amp at 12Vdc; 37.5 Amp for 24Vdc) charges a 100 amp hour battery in under an hour up to 90% charge Listed to UL 458 and CSA 22.2 NO. 107.1
Charges AGM, lead acid, GEL and LiFPO4 batteries. Power supply up to 75 amps at 12Vdc or 37.5 amps at 24Vdc.
So this may work as well
In terms of increasing my panels, I believe my CC is already at the max with the 3x340 panels I have…….. need to check but pretty sure that is the case
Would need to swap out the CC before I add anymore I think
Biggest task is finding a spot where I can move my panels to with better sunlight - where they are ( when set up 5 years ago) seems to be pretty shaded now with a lot of trees - and these are BIG TREES not easily taken down
This may involve running the MC4 cable in excess of 100’ to achieve a better spot
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gcrank1
Member
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# Posted: 29 Jun 2025 12:17pm
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You can used your existing SCC with the array size you have, just as you have been. If/when you do more array you put that on its own SCC. That way you maximize current equipment and build in some redundancy.
Shade is an array's output KILLER, and may have been the big contributor to the chronic undercharging which likely did in your LA (which always want to be kept fully charged).
LFP wont be compromised by not being fully recharged daily, though that will reduce the available AHs. Even so you'd possibly still have more available AHs than with the LA.
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MtnDon
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# Posted: 29 Jun 2025 12:47pm - Edited by: MtnDon
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Quoting: zorro Interestingly, the charger I already have seems to do 24v and lithium
Yes and No. Did you read my post of June 20 and travellerw's post of June 21? We both pointed out that your charger is "sort of rated for LFP" batteries, BUT has only pre-selected voltage settings that are sub-optimal. Sub-optimal to the point of it being very possible to damage LFP cells if the charger was not monitored carefully and manually shut down.
Read those posts again if our caveats were forgotten or misunderstood.
LFP are great batteries but are very unforgiving if voltages are not carefully observed.
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zorro
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# Posted: 29 Jun 2025 01:17pm
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Thanks for all the info
Honestly I have read every post but some of it confuses the hell out of me - and that is NOT the posts - that is me!
I really appreciate all the support from people here and apologies if I missed something or forgot an earlier response
Thanks for the info on using my existing CC and then adding another with extra panels at some point
And thanks for the clear info on my charger - I won’t be using that to minimise any risk involved
Do you have any recommendation on a charger I could get as I don’t think my 3 panels are going to output enough for the proposed 4 lithium batteries - even if I move the panels to a sunnier spot
But again, thanks for all the help - I would be at a total loss without it
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gcrank1
Member
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# Posted: 29 Jun 2025 01:30pm
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You would only be using the charger while there running the gen so it wouldn't be like totally unmonitored. What you dont want to do is have the charger possibly overcharging, but the high voltage disconnect of the bms should stop that. You dont want the bms to be doing that on a regular basis, it may compromise the bms kinda like constantly tripping a circuit breaker.
That all to say IF you run the gen+charger enough to bring the bat-bank to 80-85% when the solar isn't quite making enough you would be Ok, 'IMO'.
Just dont leave it all running while you go away for the afternoon.
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zorro
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# Posted: 29 Jun 2025 01:42pm - Edited by: zorro
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Thanks for the info
The longest the generator ever runs is 20 min max - and that is only when someone wants a longer shower
Generally, it runs for 5 minutes to Make a cup Of coffee or fill the water tanks
But NEVER more than 20 minutes at any time
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gcrank1
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# Posted: 29 Jun 2025 02:34pm - Edited by: gcrank1
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A couple years ago our gen use was limited like that so I left the charger on the bats so whenever the gen ran it was feeding some in, worked fine.
Now if something happened to me and someone else decided to run the gen 'all day'.....probably would be a fail-safe to not be always plugged in?
The solar thing gets weighty when considered as a whole. Break it down to The Storage System, The Charging System and The Power Output System. Yes, they have to work together but breaking it into system separation seems to help organized the thinking for me.
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MtnDon
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# Posted: 29 Jun 2025 09:51pm - Edited by: MtnDon
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Quoting: gcrank1 Now if something happened to me and someone else decided to run the gen 'all day'.....
That sort of thought is smart.  Most of us are not alone and accidents and other unplanned events do happen. Others may have to suddenly pickup and carry on doing things we used to do. I don't want to leave puzzles behind for those I love.
I have put together a user manual for our cabin complete with pictures and several videos. There are enough things that are different from the way things work in your average home I thought it was a good idea.
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Brettny
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# Posted: 30 Jun 2025 06:07am
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Quoting: zorro The longest the generator ever runs is 20 min max
Maybe more generator use was needed? I'm kind of the total opposite. Il let my generator run for hours to take the initial heat/cool load off the batteries. It always gets ran with the microwave even though the inverter can do it. I have no other large draws becids construction tools.
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FishHog
Member
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# Posted: 30 Jun 2025 07:27am
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Quoting: MtnDon I have put together a user manual for our cabin complete with pictures and several videos. There are enough things that are different from the way things work in your average home I thought it was a good idea.
Its a great idea, I've run my wife through all our systems and she takes detailed notes that make sense to her.
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Nobadays
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# Posted: 30 Jun 2025 10:02am
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Quoting: MtnDon I have put together a user manual for our cabin complete with pictures and several videos.
This is something I really need to do! Our kids really want us to move back to Oregon so we are closer as we are getting up there in years. If we sold the cabin it would really benefit the new owners to know how all the systems work.... primarily the water system and the electrical/solar. Winterizing is also a task that trial and error has dictated a process that prevents overwinter damage.
Thanks for the prod!
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zorro
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# Posted: 30 Jun 2025 10:49am
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Now that is a great idea
If I drop dead tomorrow, my wife or 2 boys would have literally no idea (I am not much better, but I try!!)
I really need to look at this covering….. the well, pump, solar, winterizing, opening/closing down, generator maintenance etc
A great idea!
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gcrank1
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# Posted: 30 Jun 2025 12:48pm
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Ive found it helpful for me to do 'documentation' After I have just done whatever it is. ALL is fresh in my mind and the steps are clear.
Then I re-write it all so someone else can understand it, lol
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