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beginner camper battery help ? :)

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hrchonda

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hi guys

please help, iv bought the parts in the pic and just wondering on a couple of questions.

1) is the mega fuse to high? i bought this first then ended up settling on a 200a BMS. should i get a smaller fuse?
2) i haven't bought a inverter yet and i wondering what one i should i purchase? brand wise and in terms of output do i get a 2000w inverter or get a 3000w (future proofing a little as more cells are on route) and be very conscious that it doesnt exceed the BMS's 200a?
3) im a complete novice, this my first build. if you see where iv went wrong or could recommend improvement id be very grateful.

thank you
 

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I would go 3000w with the intention of doubling your current capability in the future.

Once you start plugging things into a smaller inverter, you quickly find your limits and start considering a bigger inverter in the future anyway.
 
The cell count is going to determine your inverter choice. While you can string 12v batteries into a 24v or 48v setup later, you can't string 12v inverters to run on 24v.

200a of BMS limits you to a 2kw inverter. You could theoretically put a 3kw in there but your battery will not provide enough to feed it.

The fuse size is going to be inverter wattage ÷ voltage × 1.2. Until you have an inverter don't buy a fuse. Instead of the 300a mega fuse, consider a breaker so it can be used as a disconnect for servicing.
 
hrchonda said:
went wrong or could recommend improvement
Click to expand...
A few points.
The Victron 100 30 and 100 50 are great controllers but can only accept up to 16mm2 cable . 16 mm2 is OK.
Four 100 watt panels produce a maximum of 30 amps at a voltage of 13.5 so either a 100 30 or 100 50 will be suitable .

The mega fuse is not a suitable type for a lithium battery, either a ClassT, HRC, or MRBF is needed. As for fuse value size at 125% expected maximum current. 50mm2 cable is good for just over 300 amps. With a 2000 watt 12v inverter, fuse at 200 amps.
Fot MRBF use this holder direct on the battery, ( a master fuse, (not breaker) is needed at the battery, between battery and buss bar.

Blue Sea MRBF Terminal Fuse Block – 30 to 300A – 5191B-BSS – Camper-Camper

camper-camper.co.uk camper-camper.co.uk

Your battery at 280 Ah is good with 400 watts of solar, unless you have a very high power demand, its a good starting point.

You have more cells on order . Assuming you want to keep to a 12v system , make up a 4S battery with a 200 amp bms and use in parallel with the original.

Depending on your application further advice could be useful to help you build an effeive system, what is the application, hobby, small home, van conversion, boating?

Mike
 
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Rednecktek said:
MegaFuse... which shouldn't be used for LFP...
Click to expand...
Interrupt rating of Mega fuse is 2000 amps , MRBF is 10,000 amps at 12volts. Depends on how lucky you are. In addition Mega fuse is not ignition safe.
 
Rednecktek said:
The cell count is going to determine your inverter choice. While you can string 12v batteries into a 24v or 48v setup later, you can't string 12v inverters to run on 24v.

200a of BMS limits you to a 2kw inverter. You could theoretically put a 3kw in there but your battery will not provide enough to feed it.

The fuse size is going to be inverter wattage ÷ voltage × 1.2. Until you have an inverter don't buy a fuse. Instead of the 300a mega fuse, consider a breaker so it can be used as a disconnect for servicing.
Click to expand...
that was my first plan regarding the batterys in series but the bms i bought doesnt support it, infact after buying it i found this line "☆Doesn't Support Series Connection and parallel Connection". tho i cant understand why parallel wouldnt work.

disconnect just bought on amazon thank you!
 
mikefitz said:
A few points.
The Victron 100 30 and 100 50 are great controllers but can only accept up to 16mm2 cable . 16 mm2 is OK.
Four 100 watt panels produce a maximum of 30 amps at a voltage of 13.5 so either a 100 30 or 100 50 will be suitable .

The mega fuse is not a suitable type for a lithium battery, either a ClassT, HRC, or MRBF is needed. As for fuse value size at 125% expected maximum current. 50mm2 cable is good for just over 300 amps. With a 2000 watt 12v inverter, fuse at 200 amps.
Fot MRBF use this holder direct on the battery, ( a master fuse, (not breaker) is needed at the battery, between battery and buss bar.

Blue Sea MRBF Terminal Fuse Block – 30 to 300A – 5191B-BSS – Camper-Camper

camper-camper.co.uk camper-camper.co.uk

Your battery at 280 Ah is good with 400 watts of solar, unless you have a very high power demand, its a good starting point.

You have more cells on order . Assuming you want to keep to a 12v system , make up a 4S battery with a 200 amp bms and use in parallel with the original.

Depending on your application further advice could be useful to help you build an effeive system, what is the application, hobby, small home, van conversion, boating?

Mike
Click to expand...
iv the lf280k v3 cells. with the double pole terminals, would it still be ok to use that fuse youve recommended on only one? or do i look into class t's?

im not 100% percent i can parrallel or series with this bms. (more homework required i cant see why i couldnt parrallel) tho jk have clearly said "☆Doesn't Support Series Connection and parallel Connection"

i chose 12v initially because its safer and id never done this before and because i could take a charge from the alternator with a dc to dc. but the more ive learned and the more iv spent, i kind of want to do the house or at least some of it. not being able to power the 9.5kw shower will always feel like a fail. i think my best bet is biting the bullet throwing my newly bought jk bms in the cupboard and finding a bms that will allow 5 12v battery's in either series or parallel. that leads to the next question :)

if i have 12v battery's in parallel for say a month or two in summer in my camper. could i then take them out of the camper and wire them in series to power a 48v house inverter? or is that bad for them?

thank you
 
Rednecktek said:
Suprisingly most DIY BMS's don't support series connections for some reason. Not sure why.
Click to expand...
i took it as a given this could be done. deff in parrallel. i thought id bought the best 4s-8s BMS there was then boom i read the dreaded line
 
At that point just pull the BMS's all together and build a straight 48v 16s battery. Then you just need to buy a single BMS instead of trying to find 4 BMS's that will run in series.
 
Rednecktek said:
At that point just pull the BMS's all together and build a straight 48v 16s battery. Then you just need to buy a single BMS instead of trying to find 4 BMS's that will run in series.
Click to expand...
i know im trying to have my cake and eat it but i need 12v for the camper (and iv bought 12v mppt an cable etc) and now would also like 48v for my house.

if i have 12v battery's in parallel for say a month or two in summer in my camper. could i then take them out of the camper and wire them in series to power a 48v house inverter? or is that bad for them?
 
If the batteries allow for it then there isn't any problem. The limitation is on the BMS side, the cells themselves won't care.

Like I mentioned though, when you go to 48v, just take the cells out of the old batteries. Any wear they may have taken over the months of use is in the low single digits percentage wise at worst.
 
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hrchonda said:
lf280k v3 cells. with the double pole terminals
Click to expand...
It's a problem terminating the positive and negative. Perhaps modifying a battery buss bar to make a more reliable connection.
hrchonda said:
i have 12v battery's in parallel for say a month or two in summer in my camper. could i then take them out of the camper and wire them in series to power a 48v house inverter?
Click to expand...
Possible but impractical. 4 off 280 Ah batteries in a Euro van requires a carefully engineered instalation, and more battery than can be charged or realistically used.
It's possible to put 4 batteries each with its own BMS in series, but issues tend to exist over time, with the batteries getting out of balance with each other. A better engineering solution is to use a 16 S BMS with a dedicated 16 cell battery.

As a newcomer to all this I suggest you continue with the van build, a 12v 280Ah battery with your BMS and a 2000 watt inverter and 400 watt of panels. Carry out more research on the house solar, in particular local regulations on what equipment is allowed and to what extent is DIY possible. Also consider house insurance issues.

with regard to your BMS, serial and parallel operation, more investigation is needed, I cannot see any resion why parallel operation is not allowed.
 
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mikefitz said:
Possible but impractical. 4 off 280 Ah batteries in a Euro van requires a carefully engineered instalation, and more battery than can be charged or realistically used.
Click to expand...
with electric bikes, electric cooking, A/C And heating i could deff use it, charging's the issue, the Victron 100/50 allows for 700 watts or 900w over paneling. coupled with a 50a dc to dc of the alternator. in theory 100a charge. maybe a 2nd mppt would be needed 0.5c of my cells would be 140a charge.
mikefitz said:
It's possible to put 4 batteries each with its own BMS in series, but issues tend to exist over time, with the batteries getting out of balance with each other. A better engineering solution is to use a 16 S BMS with a dedicated 16 cell battery.
Click to expand...
agreed 16s bms is the answer, but sadly 12v is needed. would there be a way to reduce issues or at least mitigate them slightly. or regular maintaince or additional hardware to achieve this that you know off?
 
Take a look at the Renogy 3000W inverter, we've had it in for about ten months now (alongside a Fogstar 304AH lithium) and it's been brilliant. I particularly like it's pass through facility when in electric hook up.
I started off with a 1000w, then 2000w inverters, I wish I had gone for the 3000w inverter in the beginning!! We can power the microwave and kettle at the same time with power left over. We also now use George foreman grill, instead of a gas BBQ, electric pizza oven, air fryer and sometimes a crock pot. With only 200w of solar BUT a newly installed 60A DC to DC soon puts the power back into the battery when driving for an hour or two.
My biggest regret was not going for the biggest lithium I could afford, but to be honest we haven't ran out of power yet !
 
hrchonda said:
with electric bikes, electric cooking, A/C And heating i could deff use it, charging's the issue, the Victron 100/50 allows for 700 watts or 900w over paneling. coupled with a 50a dc to dc of the alternator. in theory 100a charge. maybe a 2nd mppt would be needed 0.5c of my cells would be 140a charge.

agreed 16s bms is the answer, but sadly 12v is needed. would there be a way to reduce issues or at least mitigate them slightly. or regular maintaince or additional hardware to achieve this that you know off?
Click to expand...
Do you have electric driven slides, jacks etc.? Do you boondock a lot?
 
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