I know that the nominal voltage 48v is not necessarily 48 volts, but rather like 51 or 52 volts, I can't remember. However I'm wondering why not do 15s versus 16s with my lichen 3.2 volt 280ah lifepo4 cells. If I do 15s then I will be saving about $400 on my two BMSs.
15s vs 16s
- Thread starter Stewfish
- Start date
schmism
Solar Addict
how does 15s save you $400 on BMS?
what 48v inverter and charge controler do you plan to use? What is the acceptable voltage range for those items?
what 48v inverter and charge controler do you plan to use? What is the acceptable voltage range for those items?
A batrium wm5 is $660 and only does 15s but says its for 48v systems then add on a Multimon for another 15s at 190 then its 190 for every 15s if I ever want to expand down the road. Otherwise to get 32s it's $1260 for the wm4 and 32 blockmons that individually monitor each cell. I haven't seen a BMS that can manage 32s and Batrium can. I need to do 32s with the wm4 or 15s2p with the WM5+MM8
Wm5 -
Daly also cannot communicate between the two strings.
MPP LV6548 high and low cutoffs are 44v to 66v.
So 44v ÷ 15 = 2.9v max discharge at 15s possible
66v ÷ 15 = 4.4 max charge possible
Lifepo4 cells
Wm5 -
- 10 to 15 cells in series (suitable to typical 48v lithium battery)
Daly also cannot communicate between the two strings.
MPP LV6548 high and low cutoffs are 44v to 66v.
So 44v ÷ 15 = 2.9v max discharge at 15s possible
66v ÷ 15 = 4.4 max charge possible
Lifepo4 cells
Last edited:
CAD
That's different
"15s" seems to be shorthand for 15 series cells, and "16s" 16 series cells.
OzSolar
Whatever you did, that's what you planned.
MisterB1959
Solar Enthusiast
- Joined
- Oct 22, 2022
- Messages
- 360
could a 15s battery be split into 3 4s (12v) batteries easily enough? i assume it requires a bms and busbars along with a case of some sorts? i am thinking of picking up a cheap 15s and increasing the amount of power in my motorhome (RV) - is there anything i should be aware of?
No.
First off, you need 16 cells and a 15s battery is short by 1.
There are better ways of getting more battery storage in your RV.
MisterB1959
Solar Enthusiast
- Joined
- Oct 22, 2022
- Messages
- 360
i dont want 48v in my RV ... i want 12v .....! - and 15s (15 cells) work perfectly well, not as good as 16s (16 cells) but a 15s battery still produces 48v - although i am happy to be shown that isnt true ...!
4 cells of a 48v battery would give me 12v wouldnt it? the only issue is how many amp hours, which will be dependant on what the cells are?
as i said, i am happy to be put right as i am still very much a novice!
4 cells of a 48v battery would give me 12v wouldnt it? the only issue is how many amp hours, which will be dependant on what the cells are?
as i said, i am happy to be put right as i am still very much a novice!
But do the math.
15 / 4 = 3.75
You could make 3 sets of 12V batteries from a 15s battery, but have 3 cells left over.
If you got a 16s battery, and split it into groups of 4, then you'd have 4 sets of 12V batteries, no cells left over.
But really, if you want 12V batteries, just buy 12V batteries. Don't buy a 48V and hack it up. 12V (12.8V) LFP batteries are fairly plentiful at this point.
MisterB1959
Solar Enthusiast
- Joined
- Oct 22, 2022
- Messages
- 360
Thanks for the clarification. It's just that I've been offered 2 x 15s at a very cheap price and wondered if it was worth me having a play and learning a lot more. I could make up 1 x 16s and 3 x 4s but as I have found out they are only 50ah cells, the 16s would not really be practicable on its own for my home use, hence my thoughts on making the 4s batteries for 'RV' use or even fishing/picnics etc.
I suppose hobbies cost money and learning a lot more about something 'cheaply', is better than throwing a lot of money at it
@SeaGal - you blasphemer, you!! Lol - @£300 for two pre used 15s batteries to play around with?? Should I deal or no deal??
LOL...re "@£300 for two pre used 15s batteries to play around with?? Should I deal or no deal??"
Hmmm.. not enough info... if they are AAA's, then no, if they are 100Ah, then yes
MisterB1959
Solar Enthusiast
- Joined
- Oct 22, 2022
- Messages
- 360
lol, im sure the cells are 50ah and the batteries are 2.4kw each ....
Idk, NEW 280Ah cells are under $100 in many sites now, and prebuilt 16S 100Ah packs with bms are approaching 800.
50Ah are selling all day long for 500
If i was buying USED 15S 50Ah, i wouldnt pay over 235... (50% of new cost...)
MisterB1959
Solar Enthusiast
- Joined
- Oct 22, 2022
- Messages
- 360
The price is for two ....if I can get them for that of course ...
Well now, if I could only read, I wouldn’t have posted my response. Which required me to post this…
I stand corrected!
So, I had these further thoughts at about 3am...
- The battery packs you are considering could have welded contacts and no studs - that may make them difficult to re-configure, depending on your DIY skills.
- The battery packs may be pouch-style and not prismatic (will be pouch if they are Pylontechs) - again that may make it harder to house differently.
- Fogstar's price for EVE 230Ah cells (currently out-of-stock, though) are only £40 each, so, if it were me, I'd go down that route for building some 12V packs for your motorhome.
EVE LiFePO4 230Ah Prismatic Cell (Grade B)
Eve Prismatic LiFePO4 230Ah Cells DIY LiFePO4 Batteries for off-grid, energy storage, solar batteries and leisure batteries. UN38.3, Specification Reports & MSDS. UK Stockist. Low Prices. Next Day Delivery.
www.fogstar.co.uk
MisterB1959
Solar Enthusiast
- Joined
- Oct 22, 2022
- Messages
- 360
@SeaGal Thanks as always !!!
www.gumtree.com
Other Household Goods for Sale in Gillingham, Dorset | Gumtree
Find great local deals on other household goods for sale in Gillingham, Dorset ✅ Shop hassle-free with Gumtree, your local buying & selling community.
Similar threads
