Full time off-grid camper, 2Kw PV, 11Kw Sinopoly, 24v, 1000+ amps

[SamO]

Hi All!
Overview of hardware and current project

2.4Kw PV (24x 100w on Roof wired 4s6p
400Ah of LiFePo4 Batteries (16/200a sinopoly prismatic cells)
24/3000/70 VA Victron MultiPlus II Inverter/Charger/Switch
Victron BMV-712 Battery Monitoring
Victron Venus GX - System Monitoring and Control
3x smart 220a battery protect switches
Smart charger 100/50
2X Smart charger 100/15
12x Maxwell 2.7v 3000f in series for 250f @ 32v
6 string Echo-Worthy solar combiner fusing and lightning protection

Installing a solar system on an 1997 24' camper for full time off-grid boondocking. System needs to supply 11Kw on a winter cloudy day in Az or NH. My plan is to maintain 5Kw in reserve, use 5Kw a day and be able to charge 11Kw/day.


SOLAR PANELS
24x 20v/100w mono panels configured 4s6p panels mounted flat. Roof top space is maxed. I'm building a roof over frame to support the panels 8" off the roof. At 8" vertical clearance, all my roof top vents except AC are under the panels and naturally vent out the open sides and back end..... I am a bit worried about the wind load as well as weight...ok back to the electrons...

My math shows:
- Summer 80v@33a for 2640w * 5.5hr= 14.5Kw/day
- Winter 80v@33a for 2640w * 4.5hr= 11.5Kw/day


STORAGE
LiFePo4 battery bank consisting of 16 sinopoly prismatic 220ah cells arranged as (8s2p) providing 400ah / 11Kw of usable storage at 28v.

help before I vaperize a hand
I have assembled 12 Maxwell 3000f 2.7v ultracaps in series for a total 32v max and 250f. I hope the caps will eliminate high draw voltage drops and extend battery life. I don't understand Farid's but I do understand 100a/s and a duty cycle of 1 million... I'm learning how to do inital charge.

Because I run at 28v rather that 32v, what do I lose in terms of farid's?
Is there a quick dirty way to relate watts to farid's .....

Do i need to fuse the ultracap to inverter connection?

If the caps were discharged without a connection to the batteries, when they are connected, is there a danger of the caps sucking the batteries dry?

I have two Victron 220a smart battery protectors in parallel, is that enough protection?

up coming solar related projects:
- Install 2 500w window AC's
- Remove roof top AC and replace with 4 solar panels.
- Replace canapé and mount 800w of flex solar panels that .
- camouflage battery bank case to look like diamond plate water tank with valves and pipes.

 

[Craig]

Did you have problems that led you to needing the ultracaps. Seems with 440 Am of battery you should easily be able to power the inverter.

I would worry the battery protects could get ruined if the ultra caps suck too much juice too fast.

Love the idea of camoflauging the batteries

 

[TechScott]

Let me preface the following "answers" with the fact that it's been many years since I went to engineering school but here's how I understand it:

Do i need to fuse the ultracap to inverter connection?
A general rule of electricity is that if wired to a power source or a power draw (or more practically an expensive component), a circuit should be fused. Period. It's all about safety and protecting the expensive bits.

If the caps were discharged without a connection to the batteries, when they are connected, is there a danger of the caps sucking the batteries dry?
If you connect a power source (voltage) to a capacitor which is below the capacitor's current state of charge (SOC), it will charge up to the voltage of the power source. Voltage generally flows in the direction of less voltage. If there's less voltage available than the capacitor's SOC, the battery and capacitor should equalize. So if the cap were discharged completely, it should attempt to recharge itself until its voltage is the same as the battery irregardless of what voltage the battery is.

Of course none of this takes in account what magic is going on in the balancer module between caps...

BTW, I found a great article here while recharging my mental capacitor.

More knowledgeable folks can chime in here ?

 

[SamO]

When it comes to the flow of electrons, I have no idea what I'm doing. I muck around, ask lots questions and try to understand enough to insure safety and not make magic smoke from expensive toys. That's why I'm here.

@Craig Did you have problems that led you to needing the ultracaps.

The inverter is installed and running on 120v, 28a mains supply. So I've had time to experiment. When I start the air-cond, the inverter throws an low voltage error but keeps going. I believe it the LRA at compressor start up. When one or both of the 120v chest freezers are running, and I start the air-cond, I have had the inverter shut down. I also run a 1100w microwave.

sooooo, if the system is stressed with a good power, I expect more problems when on battery. Everything runs great , I just want to eliminate the low voltage errors caused by three compressors, microwave and extend battery life. oh, and it's kinda cool to be able to say i have a thousands of amps available ...lol


"I would worry the battery protects could get ruined if the ultra caps suck too much juice too fast."

My worry as well, the bat protects are rated at 220a each, per manufacturer the battery has a C 2.5 discharge rating. But like all fusing.... better the fuse than the inverter or batteries. But for what I paid for battery protects, maybe i need protection for my protects...lol


"Love the idea of camoflauging the batteries"
too much money involved to not worry about security

@ techscott: "great article here " thank you....lots to digest there