24v Lifepo4 & solar set up

[Madoxen]

24v Lifepo4 & solar set up

Hi All I am feeling a little lost and need a push in the right direction with the electrical set up of the Pretty Ugly build.
We have decided on going 24v and not 48 as I had suggested in the past.
We are not wanting to carry gas on board so will be going electric/ diesel , with the exception of a very small gas fired miniQ webber for out door cooking.
Internally we are looking at 12 - 24v setup, an Induction cooker, 24/240v fridge and separate freezer setup both chest type or maybe draw.
Heating will be hydronic diesel eberspacher and a electric backup cylinder for heat and water.
It is possible but am not sure if it can be done with the power have a small ac unit for the sleeping area.
I was not planning on a generator but I might need to keep one for emergencies and the occasional linked house bank and gen welding if things go wrong I think this requires me to go the easysolar route not individual components.
The items I have already are
1 - 32 x 3.2V @ 280 Ah lifepo4 cells ( I am not sure I will need to use all 32 cells I could or might use just the 16 to make a 24v system), what are your thoughts. The surplus cells will be used on equipment at work so not wasted either way.
2 – 4 x 550w solar panels with the following spec. (2200 W)



3 – the merc Actos 1835 truck with its 24v setup (starter bats etc)

The items I need to figure out are many, but some are listed here

1 - Victron smart solar or Victron ?? MPPT controller ( which one ) , I was thinking of either series set up or a series parallel setup or would I be better to do a duel MPPT setup to have redundancy ? which version would be best suited for the panels and batteries that I have
In series I think they are 200v 11.24 A
In series parallel they are 100v 22.5A
Duel system would be 100v 11.24A - into each controller
2 - BMS system for the batteries
3 – Battery monitor most likely the BMV 712
4 - A way of linking or charging the truck batteries from the house and vice a versa
5 – I know there must be a lot that I have missed but what am I missing from the above

I would like to go down the Victron route but the BMS maybe Orion BMS2 or Jr 2 as another member has recently gone.

does any one have suggestions on best way to go ,

thanks

 

[dreadlocks]

SmartSolars are sized by Voltage Input / Amperage Output, how many amps of charge current do you want for your LFP bank @ 24v.. doubt you'll wanna run those in a series, you'd pay alot more money for it and not really matter.. You'll probably want like a 150/70, those are actually 60V panels, you could run 2x Series and 2x Parallel for two 1000W 120V strings.. Input power will be 2200W @ 120V (18A) and Output Power would be 2200W @ 70A (31V)

Leave your truck batteries isolated, the mixed chemistries will fight eachother and pingpong back and forth.. use jumper cables if it gets to that.. mebe some jump posts for truck near house or vice versa.

 

[Madoxen]

how many amps of charge current do you want for your LFP bank @ 24v.

Hello Dreadlocks thanks for your reply , I was after as many amps charging as is sensible from the above components , was thinking or looking at the 85 or 100 but that would be pointless if the panels will not feed it . I guess I was looking for advice on what will be best one to go for .

Leave your truck batteries isolated, the mixed chemistries will fight each other and ping pong back and forth.. use jumper cables if it gets to that.. mebe some jump posts for truck near house or vice versa.

Yes that is a good way to go but will that not stop me from being able to charge the house bank from the alternator on the go ?

doubt you'll wanna run those in a series, you'd pay alot more money for it and not really matter.. You'll probably want like a 150/70, those are actually 60V panels, you could run 2x Series and 2x Parallel for two 1000W 120V strings.. Input power will be 2200W @ 120V (18A) and Output Power would be 2200W @ 70A (31V)

alot more money for it as in coz it would need the 250/100 mppt ? if so yes i see that now more expensive for no real gain.
if i wanted redundancy would i need to get 2 x the 150/70 or would it be more like the 150/35 @ roughly half the price of the 70?

would it be daft/silly to double up on it

 

[Madoxen]

Having just reread the specs on the 150/70 and 150/35 the 70 definitely has a lot more going for it, and would be cheaper than 2 of the 35s just no redundancy, but how often do these things go up in a clowd of smoke ? eek famous last words there lol

 

[dreadlocks]

Charge rate for most LFP is 0.4C max, where 1C = Capacity in AH, so if you had 200AH you'd be shooting for ~80A.. thats gonna depend on your final pack size, but the SmartSolar has programmable output so if you go a lil large you can derate it if needed.. for 2000W @ 24v the 150/70 is well sized despite the battery under it.. the 10% over paneling is NBD, and good because you'll never see 100% output outta solar anyhow.. not worth it to pay substantially more for a charger that'll never see the difference but once or twice a year.

Your House bank you'll charge through Orion DC Chargers more than likely.. that way you can control the voltage and current going into the bank.. probably gonna need multiples in parallel to get the output your looking for

 

[dreadlocks]

For 24v you need 8 3.2v cells in series.. so if you take your 32/8=4, so you got 4 series you can parallel.. 280 * 4 = 1120 AH * 0.4 = 448A Charge Current at max, >10kw lol, 0.4C is gonna be a pipe dream if you use all those cells, you'd be looking at like 50A 220v EV chargers for that, half the cells are 224A max charge rate on a 560AH bank.. just charge those as fast as you can, but you will need to limit it to a rate your alternator(s) can safely output for constant duty in the worst temps, minus any engine loads/lights they gotta run too.. no matter how you build your pack its gonna smoke out a couple high amp alternators PDQ if they are unregulated.. alternators typically dont have power drains capable of hundreds of amps for many hours solid wired up to em directly as part of their design.

 

[Madoxen]

280 * 4 = 1120 AH * 0.4 = 448A Charge Current at max, >10kw lol,

seeing it written like that does make it sound crazy.

you'll charge through Orion DC Chargers more than likely..

probably gonna need multiples in parallel to get the output your looking for

the biggest 24/24 isolated orion i can see is a 17A 400w is it safe to parallel say 3 of them for example if I have a 2nd alternator rated at 100amps ? ( which I do ) just not attached yet lol

I really do appreciate your input and opinion on this thank you . From the looks of it I have a lot of planning and saving to do to get the setup I would like for long term travel.

 

[dreadlocks]

ayup

 

[john61ct]

The ex-Humvee alternators can do 400A at 24V, but need a fair bit of custom work mounting them never mind the robust wiring.

 

[dreadlocks]

that would be frigging incredible to charge a bank that size at max rate.. but if your going to attempt it, GTFO the internet and go hire some engineer who'll put this together in a way that aint gonna result in a fatality heh.. you are way beyond our paygrade.

 

[Madoxen]

Trouble is finding a humvee alternator in NZ. Would be pretty amazing to charge the whole bank on a leisurly drive

 

[DiploStrat]

Without knowing all of the details here, I have a 24v MB 917AF and I charge a 12v camper bank with a REDARC BCDC1240D which outputs 40A. Sterling Power makes a similar battery to battery charger that outputs up to 70A for the same price. I have a 24v/100A alternator which, I believe, is actually a MB option. Using a battery to battery (B2B) charger is dead easy and addresses issues like the danger of a depleted lithium bank overloading your alternator. With the Sterling B2B you get a ton of profiles and you can dial in any custom profile that you may want.

When I bought the truck it had a rather pedestrian PWM solar controller with a terrible profile for AGM. I am in the process of replacing this with Victron MPPT controller, putting the panels in series for (hopefully) better performance in lower sunlight, and all of the other claimed benefits of MPPT over PWM.

Might this be an easier way? A lot depends on the availability of 24v vs. 12v appliances, etc.

 

[john61ct]

Get EV level gear going, direct DC charging standards are at high rates.

Just how fast can you quick charge a Chevy Volt pack (in...

www.diyelectriccar.com

 

[DiploStrat]

Interesting.

At the same time, I am hearing some chatter about the benefits of slowing the charge to assure better cell balancing. ReLion, for example, cut their recommended charge rates when their batteries are paralleled. As a total novice at the world of lithium, I wondered if this might possibly be to allow the two independent BMS more time to get their act together.

And, after looking at a tear down of a single 100Ah Battle Born battery, I am beginning to believe my buddies who insist that, if you have the skills, you are much better off assembling your own battery with a single BMS controlling the cell balancing. And you avoid the cost of materials and wiring of say, two or four redundant BMS.

Would appreciate your thoughts.

 

[john61ct]

Yes the drop-ins are usually extremely crippled via their inaccessible BMS wrt charge rate, usually a tiny fraction of what the cells themselves can handle.

To the point that they are pretty much irrelevant if you want fast charging.

I very strongly believe it is stupid to let a BMS dictate your use case.

Buy the BMS that accommodates what you want to do.

And balancing really is not dependent on your BMS's limitations, plenty of other ways to get that job done, if/when that specific function needs doing at all.