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Yet Another Noob Diagram! (But pretty'ish)

pantechlife

Making pantech truck conversions a thing.
Joined
Oct 31, 2021
Messages
45
Location
Sydney, Australia
Hey all, while I've only been here for a short (but good) time, I've been cramming the forums and interwebs these last few weeks and gleaning the generous knowledge by yall, so hopefully I've graduated from iNoob to pretty-damn-inexperienced. I've gone and got the sum total of my learnings to date into a purty diagram with a bunch of details, power estimates and item specs links that I'd love to get yr feedback on!
Any gotchas, catastrophic oversights, suggestions?

It's a live whimsical board, anyone can comment: https://whimsical.com/elec-diagram-QzadYSZ1ub4d25eF7eymgr@2Ux7TurymNFgqMdV36oS , or see image or PDF (with links) attached.

Qs, and background:
  1. I bought an RV converted pantech truck, adorned with star trek interior metallic paint, from QLD border (peak-covid Australian state border lockdowns) and got it back to Sydney, to strip and renovate. It's got some 12v loads I'm keeping (water pump, hot water heather, fan, exhaust fan, fridge, lighting circuit [replace with led strips]) and a ~10yrs old Mod sine 3kw (3kwM) 230v inverter, which was running off (now dead) lead-acid truck batteries pretending to be house.
    I've been wondering if adding a 1kw Pure Sine Inverter (1kwPS)* is a good idea ($170ish), and dedicate it to: Laptops 2 x 45" 4k TV, Media Player, Xbox, Microwave (not at same time) - and whatever else it might manage. I'm thinking the rare power hungry stuff I might run would be fine on 3kwM (power tools mainly, tool/phone chargers) yet have read mixed reports re what does and does not work ok on mod sine - any experience re that here?
    (* I'd planned to buy a new 3kwPS, but I've run out of $ and need to get in truck asap!).
  2. I've got a 300a MRBF fuse for battery + inverter, my 2 x 200ah batteries in parallel are rated for 300a max-discharge-5-secs, 200a consistent. While I thought I'd never pull 300a this calc now tells me that single-phase AC, amps: 300, volts: 230, power factor: 0.02 [1800w "real" use] = 1380w. Now I'm confused - pulling 1380w would pull 300a and blow fuse!? Is that wrong?
  3. I found these Blue Sea circuit breakers - very cheap here in oz, all have interrupt Capacity: 3000A @ 14.7V - Links: 25a, 30a, 40a - are these suitable?
  4. I'm using a 50a AGU fuse down from the 40a MPPT before Busbar, manufacturer confirmed the MPPT has 2 fuses and we're on a busbar with 3/0 awg wire, thinking this is ok?
Thanks chums! ?
 

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4000 ac watts / .85 conversion factor / 10 volts low cutoff = 470.588235294 service amps
470.588235294 service amps / .8 fuse headroom = 588.235294118 fault amps.

That is cray cray.
 
I agree that 3000 watt inverter is too much for a 12 volt system. Going to a higher voltage and getting a 24 volt or 48 volt to 12 volt dc to dc converter is a better idea. At 24 volts, the amps are half what they are at 12 votls and at 48 volts amps are 1/4 what they are at 12 volts. Seems like magic, but wire pricing, and fuses are much less. Those higher voltage systems are safer for high wattage applications.

I have a 3000 watt inverter on a 24 volt system. I do run it several hours at 1800 watts from the inverter, which with the conversion factor is 2000 watts from the battery.

I use this rule for inverters I put in my RV:

12 volts: 1000 watts steady going briefly above that to warm a meal upon a microwave for a couple minutes at a time. I used 4/0 for the installation.

24 volts: 2000 watts constant use. I used 4/0 for the installation.

48 volts: 4000 watts constant use.

I have installed a 12 volt and upgraded to a 24 volt, but opted against going to 48 volts. There’s quite a few things I had installed that were not rated above 33 volts.
 
While I thought I'd never pull 300a this calc now tells me that single-phase AC, amps: 300, volts: 230, power factor: 0.02 [1800w "real" use] = 1380w. Now I'm confused - pulling 1380w would pull 300a and blow fuse!? Is that wrong?
You need to calculate draw numbers from the Source, in this case the batteries. So, looking at a couple different options and some napkin math:

1000w inverter /12v batteries = 83.3a * 85% efficiency = 95.8a of draw. So far so good.
3000w inverter / 12v batteries = 250a * 85% efficiency = 287.5a of draw so really pushing the limit of the spike draw.

Just for giggles:

3000w inverter / 24v = 125a * 85% efficiency = 143.75a and still well under your BMS limits.
 
Pv panels should be in series unless you anticipate shading problems.
 
Ok, I understand your points, yet I would neither be using that capacity, nor am I trying to add capacity.
I simply wouldn't, or plan to, hit 3k (in fact in my old rental flat - running a bunch of electrical heaters, toaster, oven - I calculated the circuit breaker breaking at 2kw - if we had things rated above that on at same time - it'd break and kill power. There's simply no way my truck would ever pull those loads).
I'm only considering adding 1kw Pure Sine if mod-sine would damage the critical things that I want to run off inverter - see Q1.

And if I have the 3kw and needed to things (that wouldn't be damaged) in excess of 1kw (but below 2kw) I cld use the 3kw.

As detailed above I planned to buy the 2kwPs but am tapped out $ wise!
 
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Here is my adaptation of your drawing including fuse ratings and wire gauges.
 

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1000w inverter /12v batteries = 83.3a * 85% efficiency = 95.8a of draw. So far so good.
3000w inverter / 12v batteries = 250a * 85% efficiency = 287.5a of draw so really pushing the limit of the spike draw.
And 2000w Inverter/12v = 166a - which would only be occasional spike needs (microwave, blender or somesuch)
3000w inverter / 24v = 125a * 85% efficiency = 143.75a and still well under your BMS limits.
My 2 batts in series to 24v would only supply 100a (150a 5-sec peak) though?
 
Here is my adaptation of your drawing including fuse ratings and wire gauges.
Wow, thank you - there's a lot to decode here, I hope you're ok with me posting the questions as they come to me - in the spirit of learnding:

Why 200a MRBF?
I already bought a 300a fuse as every diagram I've seen (that's anything close to my setup) starts at 250a and goes up to 400a. My batts can sustain load at 200a, burst 5-secs at 300a (why I previously asked if 300a was too low). While I don't have plans to hit those, there's no problem with 3/0 cables if I do, unless of crs I'm missing something here?

8g and 3/0 cable
I already had 3/0 (no runs longer than ~40cm) and bought some metres of 8g for the equally short runs I'll do in battery/fuse section, I'll also use most existing cabling to DC loads.
Yet you also detailed 4/0 for the 3kw inverter, even though no plans for 3kw loads?

You've detailed batt <->cable<->MRBF<->cable?
Isn't the MRBF fuse holder meant to be mounted directly onto the battery post? I found a pic online - exactly as per my battery, and had it on right of my diagram. I've attached the actual on my battery as I've understood it to be mounted.

Why 50a (and not 30a) fuse for a 22a (I mistakenly had as 24a) ac2dc?

No Battery Monitor shunt

While I'll definitely buy one eventually, between the battery/voltage meter on the battery itself, voltage display on mppt (and remote screen), I think I'll have enough info to work with in short term. Might even force me to get more related by doing calcs and using multimeter et al.
 

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I agree that 3000 watt inverter is too much for a 12 volt system. Going to a higher voltage and getting a 24 volt or 48 volt to 12 volt dc to dc converter is a better idea. At 24 volts, the amps are half what they are at 12 votls and at 48 volts amps are 1/4 what they are at 12 volts. Seems like magic, but wire pricing, and fuses are much less. Those higher voltage systems are safer for high wattage applications.
I was sold on 24v since starting research, but given the short cable runs I'll have, the existing 12v loads - with existing cabling, and that my 2 batts will only give 100a draw at 24v in series, I decided to stay with the existing 12v for now.

I have factored adding 2 more of same batts in future and having 200a draw, and using the larger 12v cabling will be safe for that upgrade too.

12 volts: 1000 watts steady going briefly above that to warm a meal upon a microwave for a couple minutes at a time. I used 4/0 for the installation.

1kw steady seems like a lot more than me, and none of my above Q's re adding the 1kwPS in addition to 3kwMS is about adding more load, it's simply re adding pure sine to be safe for mission-critical things like laptops and screens and microwave, and whatever else. I'm still pretty unclear about this aspect, and the more I write I'm thinking I should just get the 2kw pure sine on credit and be done with it!

I have installed a 12 volt and upgraded to a 24 volt, but opted against going to 48 volts. There’s quite a few things I had installed that were not rated above 33 volts.

Would be great to hear your gotchas re that 12v to 24v conversion!
 
Wow, thank you - there's a lot to decode here, I hope you're ok with me posting the questions as they come to me - in the spirit of learnding:
Will be glad to answer.
Why 200a MRBF?
I already bought a 300a fuse as every diagram I've seen (that's anything close to my setup) starts at 250a and goes up to 400a.
MRBF because it has good breaking capacity for a 12 volt nominal system.
MRBF because they are cheaper than class-t but fit for purpose in a 12 volt system.
200 amp because the aggregate matches the ampacity of the 4/0 awg return wire.
We fuse each battery individually because it will protect from a internal short within either battery.
My batts can sustain load at 200a, burst 5-secs at 300a (why I previously asked if 300a was too low).
Didn't see that.
Fuses ampacity ratings are about maximum continuous design load.
I usually fuse to the max rating of the wire because higher amp fuses have lower resistance.
Fuse breaking capacity ratings are about dead short supply.

While I don't have plans to hit those, there's no problem with 3/0 cables if I do, unless of crs I'm missing something here?
The 4/0 awg wire is for the aggegrate current of both inverters through both batteries.
4/0 awg is good for 400 fault amps.
If you look at my math from my first post in the thread you will see that 4/0 is undersized.
Exceeding 4/0 awg is giant pain in butt.
8g and 3/0 cable
I already had 3/0 (no runs longer than ~40cm) and bought some metres of 8g for the equally short runs I'll do in battery/fuse section, I also use most existing cabling to DC loads. Yet you're saying 3/0 will be insufficient for the 3kw inverter, even though I wont use 3kw loads?
3/0 cable is good for 350 fault amps.
350 fault amps is 280 service amps.
350 * .8 = 280
280 / .8 = 350

You've detailed batt <->cable<->MRBF<->cable?
Where?
1/0|UUU|<->200A_MRBF_fuse<->battery.1
Is this example the mrbf fuse should be on a carrier attached to the battery positive terminal
Isn't the MRBF fuse holder meant to be mounted directly onto the battery post?
It was initially designed to be used in a carrier that connects to the battery post.
It can also be used on fused busbars.
Finally it can be used in a terminal mount carrier on the stud of a busbar.
I found a pic online - exactly as per my battery, and had it on right of my diagram. I've attached the actual on my battery as I've understood it to be mounted.
Failure to parse.
Why 50a fuse for a 22a (I mistakenly had as 24a) ac2dc?
Because Its the max size fuse I would use for 8 awg wire.
 
In the picture the lug is not fused.
That doesn't look like an mrbf fuse but it does look like an mrbf carrier.
 
I was sold on 24v since starting research, but given the short cable runs I'll have, the existing 12v loads - with existing cabling, and that my 2 batts will only give 100a draw at 24v in series, I decided to stay with the existing 12v for now.
This is why i go with a 1000 watt limit for 12 volt:
The guy who wrote that is an MSE and designs and installs remote telecom equipment. I do make exceptions to that for surges and to warm, not cook a meal in a microwave for a couple miutes a day four to six times.

Would be great to hear your gotchas re that 12v to 24v conversion!
This is A link to part of it:
Along with the ” my RV build“ threads in my signature block. Part 2 was the upgrade.
 
Not fused, and actually not even connected.
Oh haha, yes I haven't even put together yet, that's not how I'm mounting! Was just showing where the mount would sit.

I bought this off local reputable oz ebay seller - the mount was cheaper w' fuse, than cheapest mrbf bluesea mount w' no fuse locally. If ebay fuse proves dodgy I'll buy readily available blue sea fuses.

The fuse body is ceramic yet the fuse itself looks weird? It does fit the mount pole and fitted nylon(?) nut (steel inside nut), mount seems quality. Pics:
 

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