RV 24V system New

[johnprice752]

Update.
4 of my 8 batteries arrived. Assured the other 4 will be with me any day.
Guidance sort for the charge controller. Thinking of the this one. Panels in parallel 30v 16.6amp.
Your thoughts ??

 

[HRTKD]

Wiring in parallel is more expensive than series. To wire in parallel you're going to need 2-into-1 connectors (AKA Y connector).

I can't provide any guidance on that solar charge controller. Do you have a link to an English version? Link, not a screenshot.

 

[johnprice752]

Hi. Looking to build RV 24v system using 8 off 280a lifepo4 cells solar will be from 2 off 250w 30v 8a panels laid flat. Quistions 1 is a BMS vital if i do a bottot and top to start with.
2 is the top voltage cut of important as thinking of using my solar controller that doesn't have one. Lastly where best to get a 24v to 12v converter. Currently in Spain.
Thanks in advance john

wiring series/parallel does not drive MPPT vs PWM directly
series = lower amps, smaller wire
parallel = higher current, larger wire
as long as you don't exceed the input voltage requirements of the SCC then either will work
a PWM SCC should be cheaper & in real life the efficiency difference isn't enough to get excited about

another consideration for series/parallel solar panels is panel shading
it only takes a small bit of shade to reduce a panel to a fraction of it's output
if in series then the other panel takes the same hit
if parallel the 2nd panel will have full output

Amazon.co.uk

 

[HRTKD]

Amazon.co.uk

Read the reviews. As I suspected, it isn't really an MPPT controller. You get what you pay for.

 

[johnprice752]

Wiring in parallel is more expensive than series. To wire in parallel you're going to need 2-into-1 connectors (AKA Y connector).

I can't provide any guidance on that solar charge controller. Do you have a link to an English version? Link, not a screenshot.

Amazon.co.uk

 

[johnprice752]

Read the reviews. As I suspected, it isn't really an MPPT controller. You get what you pay for.

Having watched Wills comparison video on charge controllers. I didn't get the feeling it made much difference anyway ?

 

[johnprice752]

hi. Will VOC be 200vdc in series and 100 in parallel. Thinking of the EPEVER 20A Tracer 2210AN.
Will be opererating 24v. 8 Lifepo 280a cells. Plannels are flat

 

[HRTKD]

View attachment 40609hi. Will VOC be 200vdc in series and 100 in parallel. Thinking of the EPEVER 20A Tracer 2210AN.
Will be opererating 24v. 8 Lifepo 280a cells. Plannels are flat

Voc seen at the solar charge controller will be 37.4 times the number of panels in series. You can have no more than two of those panels in series before you exceed the solar charge controller's rated voltage input. A 2s2p configuration would be OK but it's way over paneled for that controller. The nominal wattage of that controller is 260 watts. Depending on how many panels you want, you probably need to step up to a higher rated controller.

Link to your solar charge controller (always provide that so folks helping you out don't have to chase it down):

https://www.epsolarpv.com/upload/cert/file/1811/EPEVER-Datasheet-Tracer-AN%EF%BC%8810-40A%EF%BC%89.pdf

 

[johnprice752]

Hi all.
Update. Bottom balance done. Full charge from solar achived. Reading 27.8v. 1 cell charged to 3.6. Others to 3.3. Ish. Only took 3½days to put 7.5kw in ?
Should i now do a Top balance as i don't think i will be ever running them low.
Also. As i have space in my mains distribution box. Can i use a 240v 20amp circuit breaker for my solar supply ?
PS currently using my battery power for heating the house via a fan heater and heating the hot water. ??
TIA John

 

[GSXR1000]

View attachment 42707Hi all.
Update. Bottom balance done. Full charge from solar achived. Reading 27.8v. 1 cell charged to 3.6. Others to 3.3. Ish. Only took 3½days to put 7.5kw in ?
Should i now do a Top balance as i don't think i will be ever running them low.
Also. As i have space in my mains distribution box. Can i use a 240v 20amp circuit breaker for my solar supply ?
PS currently using my battery power for heating the house via a fan heater and heating the hot water. ??
TIA John

you need compression..

 

[HRTKD]

Definitely agree on the compression, especially in a mobile environment. Yes, do the top balance. A circuit breaker between the PV and the MPPT is appropriate. Make sure it is DC rated, not AC rated.

 

[GSXR1000]

Definitely agree on the compression, especially in a mobile environment. Yes, do the top balance. A circuit breaker between the PV and the MPPT is appropriate. Make sure it is DC rated, not AC rated.

I put 3 vertical strips of vhb tape between each cell to lock then together and electrically isolate them

 

[GSXR1000]

Post in thread 'Just ordered Lifepo4 prismatic cell 3.2V 280Ah lithium lifepo4' https://diysolarforum.com/threads/j...-3-2v-280ah-lithium-lifepo4.14955/post-199146

 

[John Frum]

Bottom balance done.

Hopefully you meant top balance.

 

[johnprice752]

you need compression..

Compression and protection against breaking is in hand just not visible. Thanks though.

 

[johnprice752]

I put 3 vertical strips of vhb tape between each cell to lock then together and electrically isolate them

Sorry for my ignorance. VHB tape ?

 

[johnprice752]

Hopefully you meant top balance.

I did a bottom balance but now feel i would be better of doing top balance

 

[John Frum]

I did a bottom balance but now feel i would be better of doing top balance

Top balance is the way to go.
You BMS is going to attempt to do that by default and now its starting at the worst possible place.

 

[johnprice752]

Top balance is the way to go.
You BMS is going to attempt to do that by default and now its starting at the worst possible place.i haven't got a variable voltage charger. What voltage charger should i get to top balance ?

 

[John Frum]

If you are going to do classic parralel top balance then 3.65 volts.
If you are going to do let the bms do it then...
Set the charge voltage to 3.4 volts per cell and .1 c and let it charge until either a cell trips or the amperage goes to 0.
Configure the bms to only balance on charge and only at or above 3.4 volts.
When the cells converge within ~25 millivolts you can increase the charge voltage in 100 millivolt increments to get to your target charge voltage.
What is your target voltage?
Do you intend to use float, if so what float voltage are planning for?
What is your rebulk voltage target?