how to wire battery bank? wire size? log types?

minisolar

Hey

I will have a 6 battery bank of 6v 210ah agm each. https://www.interstatebatteries.com/products/gc2-hd-agm

I will hook them up for 12v with 630ah. 

They will feed a few small items on dc... a small fan and a few usb charging ports for phones/tablets. Inverter size is 1500 watt. 

What size wire should i use between batteries? Between batteries and inverter? 

What products should I use for the connections between batteries terminals? logs? or is there a better product out there? 

BB.

Wiring wise, look at your maximum currents:

• 1,500 Watts * 1/0.85 AC inverter eff * 1/21.0 volts inverter cutoff = 84 Amps max continuous (up to 2x surge for a few seconds or so).
• If 10% rate of charge: 630 AH * 0.10 rate of charge = 63 Amps charging
• Suggest 1.25x NEC wire/breakers/fuse deratings:
• 84 Amps * 1.25 NEC derating = 105 Amp branch circuit/fuse/breaker minimum rating (for inverter wiring)
• 63 amps * 1.25 NEC derating = 79 Amp branch circuit/fuse/breaker minimum rating (for charger @ 10% rate of of charge)

For the battery bank, you have three parallel strings... I would suggest that you design for 1/2 current flow (minimum) per string for a safety factor (so you don't overheat wiring/connections if you designed for 1/3 current flow per string).

NEC is relatively conservative for wire current capacity:

https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

High pressure crimped lugs are best... 

You can buy MTW (Welding rated) cables from our host Northern Arizona Wind & Sun:

https://www.solar-electric.com/search/?q=battery+cables

And many folks have purchased made up cables from their battery distributor.

You can get hydraulic crimpers pretty cheaply from Harbor Freight/etc.:

https://www.harborfreight.com/electrical/electrician-s-tools/wire-strippers-crimpers/hydraulic-wire-crimping-tool-66150.html

You can also get "hammer crimper" tools too (debate how good a crimp they make):

https://www.solar-electric.com/hacrtoforlal.html

-Bill

minisolar

Thank you Bill. 

I think I am reading this wrong. You say I need a wire that can support min 84 amps between batteries and inverter and 63 amps between batteries themselves? I then look at that chart but it seems like the higher the temp the more amp a wire can support?? seems like it will be the opposite for safety? 

I will always rather spend a bit more and be overly safe. Then what gauge is that for those connections? 

Also, do you agree that a 10/2 romex between generator and charger, between generator and ats, and between ats and panel - is ok? 

softdown

Serial connections realize a lot more current than parallel connections. There is that.
 At 12 volts you need to think big - four times more amps than a similar 48 volt configuration. But I can't advise on needed wire size. Plus I always go bigger than needed. 

BB.

When you have three battery strings in parallel, in theory, then each string should share 1/3rd of the current.

In practice, minor variations in wiring length, connector resistance, etc. can cause sharing to be somewhat unbalanced... I would use larger wiring for the battery interconnects just in case (using wiring rated for max current of bank such as 84 amps for each battery string would be fine).

Regarding 84 vs 63 Amps--I was just showing how you have to look at both your loads and charging source current (and usually you have an "84 amp" branch circuit+breaker to your loads and a second "63 amp branch circuit+breaker to your charging source, etc. for each wired branch circuit)... Usually loads average higher current than charging sources--But not knowing what you use to charge with/how many watts of solar and such--I used 10% rate of charge as an example. You may have 20% rate of charge current available, then that becomes the "maximum battery bus" current instead of the loads.

NOTE: I did make a mistake--Your battery bank is 12 volts, not 24 volts, so that 84 amps is wrong. (I don't what I was thinking when I wrote that--You said 12 volts--I am very sorry).

For a 1,500 Watt AC inverter (if you design to support full 1,500 Watt load):

• 1,500 Watts * 1/0.85 AC inverter eff * 1/10.5 volts inverter cutoff = 168 Amps max continuous
• 168 Amps * 1.25 NEC continuous current derating (suggested) = 210 wiring+breaker rating (200 amps would be fine too)

A 630 AH 12 volt battery bank--The maximum continuous load suggested would be:

• 630 AH * C/5 (5 hour discharge rate max for FLA deep cycle battery suggested) = 126 Amps
• 126 amps * 12 volts * 0.85 AC inverter eff = 1,285 Watt suggested max AC inverter load (continuous)

Your present battery bank design is pretty much right on the edge of supporting a 1,500 Watt AC inverter at full load--But using less than that max amount (smaller AC loads)--All should be fine.

If you know you are going to use ~750 Watts or less for the inverter, you can certainly wire your branch circuit to support 1/2 the current.

Or even get a MorningStar 300 Watt AC inverter.

Higher temperature rated wire uses insulation designed to run at hotter temperatures... That is why you can see one wire rated "differently" vs insulation type... Of course, wire running "hotter" is wasting more of your solar power (as waste heat). Using heavier wiring will save on voltage drop and waste heat.

https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

10 AWG copper wiring is typically rated for 30 Amps max... Your 1,500 Watt inverter and 3,000 Watt genset (guess) may output:

• 1,500 Watts / 115 VAC = 13 Amps max
• 3,000 Watts / 115 VAC = 26 Amps max

So, from the "nominal" max current point of view, 10 AWG Romex would seem to work (assuming ~3,000 Watt genset and 3 kWatt max AC loads).

-Bill

softdown

How did we go from 126 amps to 13/26 amps? Answer is going from 12V DC to 120V AC. But these wires are handling 12V DC loads. I'm guessing ~ 4AWG. It would be easy to look up, I am frying other fish today. 

minisolar

Thank you so much Bill. Super informative! 

Great progress here with your help: 

1. My genset is 2000watt so 10awg is good.
2. Wire between batteries and inverter per you spec should be 2/0 as well as between my batteries for parallel and series connections. right? 

I will test how much my freezer conversion pulls as well as my ductless next time I go. They both go on and off for cycling the compressor so continuous they are not pulling too much. 

My plan is to have generator run during the night feeding ductless ac, fridge, and iota battery charger. I spoke with IOTA tech support. They said that at max the IOTA 30amp model I have will pull is 850 watts when in bulk mode and drop all the way down to 26 watts for final stage... I believe my ductless pulls about 350-400 watt and the same for my freezer but will verify when I am there next time. 

This means my geneset should be able to charge and support my load during the night with room to spare.

During the day we usually do not run the ac unless for a small stretch of 2 hours when my son naps but the fridge is obviously on 24/7. 

We do kick in our 750 watt microwave and 900 watt toaster for lunch and breakfast but never at the same time and for very short amount of time obviously so the max the inverter will need to supply is really fridge + toaster which I think will push it to the edge but that is really only for 5-10min. I will also run a test on toaster and microwave to see how much it pulls in real life. 

The two other "big items" - rv water pump and propane water heater will only run with fridge at the same time so again I am well below the 1500 watt inverter max supply. 

Another 24/7 item will be a 12v fan which is part of my toilet. They spec it at 12v 2.5 watt / 210ma so again not a big draw at all. 

Once you confirm the 2/0 wire and circuit breaker size - I will update my wiring diagram and post that. 

BTW... the IOTA tech support guy was really nice and emailed me a diagram of how to wire my batteries and iota. I am attaching the diagram here - is he correct? He said that all wires need to be same length and gauge. 

softdown

Nice diagram by Iota - that is the best way to do it. But there are issues with some numbers that I see:

I hope you use Energy Star fridge and freezer - or smallish ones if not. My fridges and freezers all run around 150 watts - or less. Unless in defrost mode which takes 500 or 600 watts. 

Well pump is an  unknown - they are often by far the largest load. You need to know the pump size and well depth to get an idea of that draw. 

We have, so far, well pump, fridge, freezer, a/c. toaster, microwave, rv water pump, IOTA 30A charger, What about internet? Laptop? TV? Cell phone signal booster? Security system? Another kid? Lights? Video games for the kid? 

Solar panels? 

On six batteries? This is going to be tight. You are on the right track but I predict a desire for more available energy. 

2/0 cable sounds good though overkill for the parallel connections. Common code seems to be 4/0 serial and 2/0 parallel - for those who have solar code that is. 

minisolar

Thank you Softdown. 

A few notes:

It is an RV pump. Not well pump. Ac is ductless 22 seer so it used about 300 watts when on... I think I am good with my plan of no solar panels and overnight charge with genset. All the items you mentioned will never run at the same time. 

I gave a run down of loads a while ago and Bill broke it down and it showed that on 6 batteries that I fully charge at night using generator then use it through the day - I should be good. 

Thank you for the 4/0 series and 2/0 parallel. If Bill agrees - that is what I will do. 

I am trying to figure out the best way to connect the lugs to the cable. I will have my electrician friend suggest a way as well. What is the absolute best way? torching so metal? 

Wheelman55

Either:
A. purchase pre-made cables from NAWS or from Polarwire or
B. Buy bulk cable, lugs, shrink tubing, cable cutter, cable stripper and a professional quality crimper, then assemble them yourself. Polarwire has excellent cable, lugs, crimpers, etc. 

https://store.polarwire.com/

You’ll spend less money with option A. You’ll get exactly what you want with option B. 

BB.

You can always start with what the AC Inverter recommends for DC wiring size... But many times the wiring suggested is pretty light weight.

You can see the difference in rates between marine use and NEC use:

https://www.westmarine.com/WestAdvisor/Marine-Wire-Size-And-Ampacity

AWG Wire Specs

Wire Size (AWG)	Nominal OD	Weight per 1000'	Stranding Number of 30 AWG	Cir.Mil. Area	Square mm	Ohms per 1000'	Max Amps
18	7/64"	12lb.	16	1,600	0.823	6.48	20
16	1/8"	16lb.	26	2,600	1.31	4.00	25
14	9/64"	23lb.	41	4,100	2.08	2.50	35
12	5/32"	31lb.	65	6,500	3.31	1.75	45
10	7/32"	44lb.	105	10,500	5.26	0.98	60
8	5/16"	86lb.	168	16,800	8.37	0.62	80
6	11/32"	118lb.	266	26,600	13.30	0.40	120
4	13/32"	178lb.	420	42,000	21.15	0.24	160
2	15/32"	277lb.	665	66,500	33.62	0.157	210
1	17/32"	350lb.	836	83,690	44.21	0.127	245
1/0	9/16"	437lb.	1064	105,600	53.49	0.099	285
2/0	5/8"	549lb.	1330	133,000	67.43	0.077	330
3/0	11/16"	675lb.	1665	167,800	85.01	0.062	385
4/0	13/16"	837lb.	2109	211,600	107.20	0.049	445

https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

Size	Copper Conductors					Aluminum Conductors Copper-Clad Conductors
		60° C (140° F)	75° C (167° F)	90° C (194° F)			60° C (140° F)	75° C (167° F)	90° C (194° F)
AWG Kcmil		Types	Types	Types			Types	Types	Types
		TW	RHW	TBS			TW	RHW	TBS
		UF	THW	SA			UF	THHW	SA, SIS
			THWN	SIS				THW	THHN, THHW
			XHHW	FEP				THWN	THW-2
			USE	FEPB				XHHW	THWN-2
			ZW	RHH				USE	RHH,
				THHN					RHW-2
				THWN					USE-2
				XHHW					XHH, XHHW
									XHHW-2, ZW-2
18		-	-	14			-	-	-
16		-	-	18			-	-	-
14 *		20 (15)	20 (15)	25			-	-	-
12 *		25 (20)	25 (20)	30			20 1	20 1	25 1
10 *		30	35 (30)	40			25	30 1	35 1
8		40	50	55			30	40	45
6		55	65	75			40	50	60
4		70	85	95			55	65	75
3		85	100	110			65	75	85
2		95	115	130			75	90	100
1		110	130	150			85	100	115
1/0		125	150	170			100	120	135
2/0		145	175	195			115	135	150
3/0		165	200	225			130	155	175
4/0		195	230	260			150	180	205

You can see that 4/0 in marine is "rated" for 445 Amps and the NEC table is rated for 195-260 Amps.

NEC is generally assuming that the wiring is in conduit--And you would have less cooling effect from air flow.

So, for the Cable from the DC input to the inverter to the battery bus bar anywhere from 2/0 to 4/0 is certainly going to work (based on NEC). 4/0 cable is thick, expensive, and a pain in the butt to work with. Make sure you are OK with using that stiff cable in your wiring.

continue next post

BB.

Would I tell you to go to 2 AWG (210 amp max Marine limit)--That is pretty light weight.

For the battery bank--You are drawing pretty much all the current the battery bank can sustain... If you want to go with 1/2 of the bus current as "worst case average" (~200 amps / 2 = 100 Amp battery series string) would be OK if you want to save money or have issues with "bending" the heavier cables.

The other issue is that you want to watch the voltage drop... For a 12 volt battery bank, I would suggest a maximum wiring drop of 0.5 volts at rated current for entire wiring path (allows for 1.0 volt drop at 2x starting surge current). Remember everything adds to voltage drop (connections, fuses, circuit breakers, etc.).

For example, say you want 2/0 cable and 5 feet from inverter to DC battery bus. Using a simple voltage drop calculator:

• 2/0 cable
• 168 amps inverter max current
• 12 volt bus
• 1x pair of cables
• 5 feet one way run (this calculator assume 2x run for cable length):

https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.2557&voltage=12&phase=dc&noofconductor=1&distance=5&distanceunit=feet&amperes=168&x=0&y=0
Voltage drop: 0.13
Voltage drop percentage: 1.09%
Voltage at the end: 11.87

And assume 2 AWG cable for battery to battery connection:

• 2 AWG
• 168a/2 = 84 amps per battery string (worst case)
• 12 volt bus
• 1x pair of cables
• 1 foot run or 1/2 foot (because this is only one cable, not a +/- pair of cables)

Voltage drop: 0.013
Voltage drop percentage: 0.11%
Voltage at the end: 11.987

Add 0.13 for inverter cable drop + 0.013 volts for battery string drop = 0.143 volts estimated worst case drop at room temperature. Certainly well under the 0.5 volt drop for a 12 volt DC inverter maximum voltage drop I would suggest.

Of course the lengths are pure guesses on my part. And I cut back on the cable size a bit (to NEC ratings) assuming that these will be bare wires and not in conduit of some sort. I would be pretty sure that these AWG ratings are still much heavier than you would see in the inverter's manual.

Engineers--Always accused of "over designing" a solution . Sometimes, that is true. Sometimes you need to take into account the worst case conditions--You don't want to lose power 100 miles in the middle of no-where.

-Bill "dancing around the question" B.

minisolar

Wheelman55  - sold. You are right. Why fuss with this. I work in real estate and have an account in a good electrical supply store so let's assume I can get at least the cable for a really good contractor price but still... I think I have enough on my plate plus I will assume they will make better connection on those cables but that is not a given to be honest. 

Bill - I will rather not work with crazy wire if I am really doing an over over kill. My inverter will not be 5ft away. Probably like 3ft. Then from your post 4/0 to from battery to inverter is way over kill same for 2/0 for between batteries? Yes they are not going in conduit. They will be bare and in a shaded wooden closet that is closed up (anti theft)

Then I am well bellow voltage drop using 2 awg between batteries (parallel and series?) and 2/0 between batteries and inverter? 

More specific questions:

1. assuming I will buy pre amde cables like wheelman suggested - I never met a gc battery in person (haha). Are those terminals threaded? I have seen some cranking down a nut on top of the lugs? if not - then what parts do I need to make those battery to battery connections? 
   
2. Looking at the IOTA diagram I have - I will need to combine 3 wires from positive with 1 wire to iota then the same for the negative. I am assuming the correct way is to use a bus terminal for this? 
3. The whole "power system" (inverter, charger, ATS, batteries, and so on) will be house in a closed wooden closet. I will drill some holes for air flow... Should I put in a fan in there? I think I will also run a battery power thermometer in there 
4. I bought this: https://www.amazon.com/gp/product/B07W8MVNSJ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1                  Let me know if it is no good and I will return it. This is for my 12v loads - 2x usb charging ports, toilet fan. I believe this connects directly to the bus terminal where the iota connects to? 

I will wait for your final word on wire size and then I will update my diagram (maybe use the nice iota one with my added stuff. 

BB.

I probably underestimated the battery to battery bus connection lengths--It really depends on how you wire them (and if you use a bus bar or not)... But 2 AWG from battery to bus bar even at 2 feet is not going to be an issue with voltage drop or current capacity.

And voltage drop wise, 2/0 to the inverter is not an issue. Current capacity, again, 2/0 should be fine.

You say you are going to use a wooden closet (in cabin/home or outside)? Ventilation to prevent electrolyte fumes from getting into living space... And using gypsum board or concrete backer board for wall, concrete board or tiles for floor to reduce fire hazards would be good (wiring not in conduit, so reducing ability of red hot wire/dripping flaming insulation from setting area on fire--Not a bad idea).

You need to figure out the brand/model of GC battery. Depending on mfg., they can have several terminal options, from a standard round post to a "flag" with a hole to put a nut and bolt through (I am not in the battery business--Just from what little I have seen).

There are multiple ways of attaching the cables together... Stack of cables with terminal ends on a brass bolt to various bus bar options... And bus bars with holes and binding screws.

Poster 2manytoyz has a section on his solar power system--Much of it was DIY. Lots of photos:

http://2manytoyz.com/

Our host has bus bars... The ones with the binding screws and holes appear to be 1/0 AWG maximum size (no 2/0 that I could find with a quick look).

https://www.solar-electric.com/search/?q=bus+bar

Pre-wired E-Panels are an option for larger systems... You can see how they do some of the wiring internally:

https://www.solar-electric.com/lib/wind-sun/E-Panels-explained.pdf

The automotive style fuse box... I am not a big fan of automotive fuses (reports of melting fuse bodies even at less than rated load)--But should be a good start. Breakers are a good option too--No replace fuses need to be stocked, and they make nice on/off switches too.

Not at your place. I am not an electrician, etc... I can give you information, but you need to make these decisions. I cannot make them for you.

My big concern is fire. You have a large battery bank, lots of DC current, exposed wiring, that operates unattended. If the system is built outside--Perhaps you don't need gypsum/bathroom backer/concrete backer boards/grounded metal sheet for backing, etc. to reduce the chance of fire as much (system on gravel pad, a bit away from buildings--Although, in California brush and forest fires are always a big concern because of our dry summers--And as our now bankrupt utility found out, a worn out $30 power line hanger causing a fire that wiped out a town).

https://newsofthenorthbay.com/2019/12/state-report-pge-inspection-negligence-caused-camp-fire/

Other things like having wiring come in from bottom of panels/bus bars (drip loops)--If there is a chance of water getting in... Water can follow the wring to the terminal connections and cause corrosion/etc.

-Bill

minisolar

Great so 2 awg and 2/0 it is. After diagram is completed I will build it in 3d sketchup to see how far things will be from each other to know exactly my wire lengths. 

This is the battery I will be buying https://www.interstatebatteries.com/products/gc2-hd-agm

I cannot see where it says the connection type of the terminal. I will give them a call tomorrow.

I'll be returning the fuse box after your comment and get circuit breakers instead. My 12v load are really minimal. usb charging ports and a fan. In the future maybe some ceiling lights and ceiling fan but that is it... 

I came across these circuit breakers: 
https://www.amazon.com/dp/B07LD7HM5M/ref=pd_luc_rh_sspa_dk_huc_pt_expsub_2?spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyOUFCODNTTVNUQlhKJmVuY3J5cHRlZElkPUEwMzg2NzA3MTU1VExNOEJMSkFGWSZlbmNyeXB0ZWRBZElkPUExMDI0MDQwMzFUUk1aOUdPVEpSWSZ3aWRnZXROYW1lPXNwX2h1Y19tcmFpJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ&th=1

and this one 

https://www.amazon.com/gp/product/B07TJ3C4WB/ref=ox_sc_act_title_1?smid=A2AF8XMIDUY3TS&psc=1

In the comments they say it is not automatic reset which is good. 

Let me know which one looks better to you. 

I think I will run one of these: https://www.amazon.com/gp/product/B083LLY3DG/ref=ox_sc_saved_title_10?smid=A2XOFAIBRI2UCF&psc=1

As well as that fan I mentioned earlier off one 10amp circuit breaker. That sounds good? 

After your comment on the fire hazard: I will line the inside of that wooden closet in 5/8 fire rated drywall and the "floor" of the closet with 5/8 cement board. The closet will not sit on the ground - I will mount it to the wall about 4ft up from the ground. 

Are ventilation holes fine are do I need a small pc fan as exhaust? I think I will run a thermometer probe in there to keep track of the temp in these hot months. 

I will try to finally update my diagram after my kids sleep tonight and post it. 

Wheelman55

Mini...the wire that you’ll get from Polarwire is extremely fine stranded, so it is very flexible.  Tony Candela (ceautoelectricsupply.com) has even finer stranded wire...his wire is also a bit more expensive than even Polarwire:).

Wire from either of these companies is a joy to work with.  It is a night and day difference vs the stiffer welding cables.  I want to say that Schneider uses Polarwire inside their XW inverters and PDPs??

If you do decide to “roll your own” cables, it’s pretty easy...just a bit of a commitment in tools.

mike95490

Wheelman55 said:

Mini...the wire that you’ll get from Polarwire is extremely fine stranded, so it is very flexible. 
...
...
...
If you do decide to “roll your own” cables, it’s pretty easy...just a bit of a commitment in tools.

That fine strand wire requires the right style of connector and you are going to invest in a 15 ton hydraulic crimp tools for that gauge. Thats a bit of tool commitment.   You might shop around for some pre-terminated cables in the size you need.
https://www.solar-electric.com/battery-interconnect-cable-00-awg-18-inch-mtw-red.html

MTW  (machine tool wiring) is flexy cable with a UL rating.

minisolar

wheelaman you got me sold on buying those cables!

Thank you for the tip.

I have enough on my plate and would love to not have to worry about making cables. 

minisolar

Also, I noticed that the battery spec says this: "Termination : UT"

I found on Trojan website (not same brand battery but still) that UT stands for Universal Terminal. 

See here: https://www.solarelectricsupply.com/media/product-images/Batteries/Trojan/terminal-types.gif

Then if that is indeed the type of terminal on those Interstate batteries: what will be the best kind of connector for those cables?  

Another question while I am working on diagram... If my Battery charger is connected to an outlet that is power by the genrator and then the charger connects to a bus terminals for the pos and neg of the batteries to charge them then... when I switch off the generator wouldn't power flow from batteries back to the charger and maybe all the way back to my generator? If yes then how do I prevent that? 

minisolar

Updated diagram attached. 

Please look at my circuit breakers and wire size to let me know if I am good. I didn't put the gauge for the 12v wires but probably 14 awg since it is about 15ft away from batteries but I haven't checked those charts yet about volt drop. 

The genset will be wired to ATS as the dominant so when it is on the ATS will send it's power to the panel and when unplugged it will revert to the inverter. 

You will notice that I am putting an inlet between ATS and panel. That is for if I want to run panel directly from generator or inverter without using ATS in case I have some issue or something. 

Questions:

1. since the inverter only has an outlet on it.. I guess I need to wire a male plug to some wire to feed ATS? 
2. Need circuit breaker between charger and batteries? 
3. Need something to prevent reverse current (blocking diode?) between Battery charger and batteries so it doesn't send current from batteries to my genset? 

Wheelman55

mike95490 said:

Wheelman55 said:

Mini...the wire that you’ll get from Polarwire is extremely fine stranded, so it is very flexible. 
...
...
...
If you do decide to “roll your own” cables, it’s pretty easy...just a bit of a commitment in tools.

That fine strand wire requires the right style of connector and you are going to invest in a 15 ton hydraulic crimp tools for that gauge. Thats a bit of tool commitment.   You might shop around for some pre-terminated cables in the size you need.
https://www.solar-electric.com/battery-interconnect-cable-00-awg-18-inch-mtw-red., html

MTW  (machine tool wiring) is flexy cable with a UL rating.

Mike. I’ve been using a Greenlee K09 for years. It’s a long handled hand crimper that crimps 8 gauge through 4/0. New they are approx $300 US, less if found used on eBay. https://www.greenlee.com/us/en/product-overview-k09-syncro

Stiil the best bang is pre-made:)

softdown

What I was trying to say is that parallel wires can be smaller. Like 2AWG.  4/0 wiring is for big set ups. Don't waste your money on that. 

BB.

You have to check with your brand/model of charger, but a battery charger should not drain the battery bank.

For safety, generally a minimum of 6 AWG from battery bank to ground rod (good idea if you have lightning in the area), and between major "metal" like your AC panel, Inverter chassis, charger chassis.

The generator (Honda eu2x000i?) has a "floating AC output". If the inverter is a pure/true sine wave inverter, it also will have a floating AC output. Your main panel can have a grounded Neutral bus--Or an optional grounded neutral bus (usually a screw that ties the neutral bus to chassis ground).

If your AC inverter is a MSW (modified square/sine wave) type--Generally you have to leave the AC output "floating". You cannot ground bond an AC neutral to safety ground--It will short out the inverter.

For floating AC from genset and/or PSW inverter, it is your choice to float or ground bond the AC neutral. Most everything will work fine (issues with auto/spark ignition for some stoves, florescent tube lights may not start reliably).

If you have lightning in the area, surge suppressors on DC and AC lines is not a bad idea.

-Bill

minisolar

BB. said:

You have to check with your brand/model of charger, but a battery charger should not drain the battery bank.

For safety, generally a minimum of 6 AWG from battery bank to ground rod (good idea if you have lightning in the area), and between major "metal" like your AC panel, Inverter chassis, charger chassis.

The generator (Honda eu2x000i?) has a "floating AC output". If the inverter is a pure/true sine wave inverter, it also will have a floating AC output. Your main panel can have a grounded Neutral bus--Or an optional grounded neutral bus (usually a screw that ties the neutral bus to chassis ground).

If your AC inverter is a MSW (modified square/sine wave) type--Generally you have to leave the AC output "floating". You cannot ground bond an AC neutral to safety ground--It will short out the inverter.

For floating AC from genset and/or PSW inverter, it is your choice to float or ground bond the AC neutral. Most everything will work fine (issues with auto/spark ignition for some stoves, florescent tube lights may not start reliably).

If you have lightning in the area, surge suppressors on DC and AC lines is not a bad idea.

-Bill

Yes my inverter is pure and my pain panel has the neutral bus connected to the ground because of genset float. I do not have lighting issues in my area I think.. Upstate ny. 

I have a ground rod that my main panel is hooked to. Should I run all the grounds (battery bank, inverter, charger, and so on) run to the sane ground rod or is it a good idea to make another one? Separate one?

Do I need a circuit breaker between charger and battery bank? 

I'm going to order cables next week and as soon as I get them - build the set up and post photos 

BB.

Personally, I like a ground rod close to the "thing" (fixed typo--thing, not think) (solar racking, main power panel, etc.) for lightning grounding.

And to connect "all safety grounds" (solar racking, AC panels, DC negative ground bus, etc.) to the local (to power system) ground rod/cold water pipe. This 6 AWG (minimum) ground wire between "all the power system exposed metal" so that if there is a short circuit (DC hot to ground, or AC hot to ground), the 6 AWG will "short out the cable" and pop the fuse/breaker back at the energy source (typically the DC Battery Bus, and the AC main panel).

If you did not tie the "metal together"--You could, for example run a 120 VAC flood light for the yard mounted on the solar racking--And get a short to 120 VAC hot. Without the 6 awg wire back to the power shed, the metal structure can become energized and shock/electrocute somebody touching the metal/walking in wet grass/in the rain.

Breakers and Fuses are always placed "close" to the major source of current (like the Battery bank) and are sized to "protect" the wiring from starting a fire if there is a short. So, yes, having a breaker near the + battery bus for the + wire back to the charge controller is required to protect that wiring from a short.

We are so used to not seeing fuses on car batteries... First the cables going to the starter are generally heavy enough to take a short, and take the battery "dead" before overheating/catching fire. And many times, cars use "fuseable" links (wire designed to also be a "fuse")--So it looks like there is no fuse between the battery + and the cabin power connections--When there is really a "fuseable link" in the circuit.

-Bill

minisolar

Thank you Bill. I do not have solar panels or charger. My current rod in the ground, which has all the ground lines from my panel run to it - is about 10ft away from where my power system will be. I can either have another rod for my power system or just run that 6 awg to that rod. What do you think? 

Another question - can my battery charger cause damage to my 12v items (fan, usb charger, and battery monitor) since it will be sending a high voltage to the batteries while charging? 

I am working on a 3d model for all the parts so I can post it here and then estimate cable lengths and order from teh site wheelman recommended 

BB.

Since you have a low chance of lightning in your area... There is really no reason for a second/multiple ground rods (each near a structure/device that would need lightning grounding). Just tie all of the "metal" (associated with DC and AC power) together with 6 AWG cable (and/or EMT conduit, etc.) should take care of the issue with shorts to ground, etc.

The question of damage to "12 volt devices" on a deep cycle battery from over voltage.

Many "12 volt" adapters are designed for automotive use... Where ~12.4 volts seems to be the maximum working voltage. We have had a few reports of things like a 12 volt adapter for a laptop where a deep cycle battery charges at ~14.75 volts, and can EQ at 15 to 16 volts.

In fact, there are many 12 VDC AC inverters that will shutdown/alarm at 15.0 volts, and others that will take 16-17 volts or so (similar for 24 and 48 volt inverters too). For folks in Canada and other cold climates, charging over 15 volts is not uncommon in winter (charge controllers raise charging set point as ambient/battery temperatures drop.

Using an AC inverter limits the "12 volt" bus variable voltage (10.5 to 15.0+ VDC) "issues" to just the AC inverter.

When you have lots of DC loads, then you are looking at many devices that may not even have their min/max voltages listed, or are "outside" the DC Bus voltage range of a deep cycle 12 volt battery.

You can find 12/24 VDC USB adapters--Which would take care of the 15-17 volt VDC battery bus issues nicely:

https://www.amazon.com/s?k=12+24+volt+DC+usb+charger&ref=nb_sb_noss

Another way around the issue is to use "buck/boost" switching power supplies... For example take a wide range of 10.5 to 17+ VDC and regulated 13.8 Volts (typical "rated operational voltage" for HAM radios):

https://www.amazon.com/s?k=buck+boost+converter&crid=388OIEUYHFPVN&sprefix=buck+boost%2Caps%2C242&ref=nb_sb_ss_ac-a-p_1_10

You need "buck" to drop from "high voltage" to 13.8 volts. And you need "boost" to raise input voltages to 13.8 volts.

-Bill

minisolar

Thank you Bill. 

I will tie them all to the rod I have using a 6awg. When you say 6 awg you mean that all the connections should be using 6 awg or will I need different gauge to different device (for example different ground gauge from batteries to rod than from iota?) 

My near future dc loads will be: fan taht draws 210ma, and two usb ports drawing amp each. I found the best one I think: one that supports high charge 3.0 while not having those silly led and volt meters built in which take power for absolutely no reason. 

https://www.amazon.com/gp/product/B07QZZP2PT/ref=crt_ewc_title_dp_1?ie=UTF8&psc=1&smid=A3DB9O4735M3ED

Assuming I will run these 3 dc loads off same circuit breaker and that they will be about 10 ft away from battery - does a 20 amp circuit breaker work or do I need a different size? 

I am assuming that I just use bus terminals for these as well? So I will have a positive and negative bus terminal that will connect directly to batteries (and circuit breaker on positive line between batt and bus) then from bus terminals I will run to each device?

Can I run one line for usb ports and connect them like you would connect outlets or do I need to run two separate lines from bus terminal to each usb port? 

BB.

Battery banks can output lots of current into a dead short--Even relatively small banks of a 100 AH (they can supply 100 amps to start a car motor). You want heavy enough ground connections so that they can pop an upstream fuse/circuit breaker if there is a short. 6 AWG will work for upwards of 120 to 200 amp breaker. And 6 AWG will "fuse" around 600 Amps. And 6 AWG is usually heavy enough that it will not be mechanically damaged if somebody trips over it at the ground rod.

6 AWG also seemed to be the minimum needed to withstand a basic lightning strike without fusing from the lightning surge.

Of course, using the NEC requirements for minimum ground conductor size is a very good place to start. Another common practice for branch circuit wiring is to use a ground conductor that is the same size of the wiring. I.e., if you are using 14 AWG for ~10-15 amps (with fuse/breaker), then 14 AWG ground cable.

Most car lighter sockets/wiring assume protected by a 10 amp fuse--So I would be a bit leary of placing on a 20 amp circuit.

For example, your link suggested a 39 Watt max input. With "constant power" devices, the current is inversely proportional to the voltage. At lower input voltages, higher current requirement:

• Power = Voltage * Current; I=P/V
• Example: I=PV= 39 Watts / 11.5 volts = 3.4 amps
• I also suggest running at 80% of a fuse/wire rating, especially for Battery Charging which can run for hours at rated loads
• 10 amp branch circuit * 0.80 = 8 amps max continuous suggested
• 8 amps / 3.4 amp max load = 2.4 ~ 2 of your USB converters per 10 amp @ 12 volt circuit.

Could you use a 20 Amp fuse/wiring (12 AWG) * 80% = ~ 16 amps continuous ? Yes, it would work. But it is a question at what maximum current rating should one of these devices be exposed too... 10 Amp Fuse is conservative.

Remember that while P=V*I, there are also equations like P=V^2 / R, and P=I^2 * R -- meaning that if you double the voltage or current, the power to a short circuit is "squared" or 4x more. Why it is always best to understand your loads/devices and not connect a 2 amp load to a 100 amp circuit (crazy talk). The 2 amp device and its connections would probably be "toast" before it would ever blow a 100 amp fuse if there is an internal short.

There is also voltage drop to be worried about... Say using 14 AWG wire (good for 15 amp breaker/fuse according to the NEC) for 10 feet with 11.5 volts (battery bank under load, low state of charge) and 2x 3.4 amp loads. Using a voltage drop calculator:
https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=8.286&voltage=11.5&phase=dc&noofconductor=1&distance=10&distanceunit=feet&amperes=3.4&x=0&y=0
Voltage drop: 0.34
Voltage drop percentage: 2.99%
Voltage at the end: 11.16

Typically we suggest 1% to 3% voltage drop maximum, so a 10 amp circuit @ 14 awg @ 12 volt battery bus would work... Sending a single pair of 14 AWG cables to a pair of USB converters (you do not need to "home run" the wiring back to the battery bank for 2x USB devices per branch circuit).

Anyway--Suggestions. A thing to watch out for--Using 14 (or 12 and heavier) AWG wiring--Using solid conductor wiring is pretty stiff... Make sure there is no flexing (i.e., mounting USB devices on cabinet door using solid wiring)--Or the wiring can work harden and fail, or over stress the USB converter wiring tabs. Use fine stranded cable in "moving" device applications.

Does this all make sense?

-Bill

minisolar

I will re-read this after work to better understand everything. 

I just wanted to update that iota told me that my battery charger voltage will be:
Float - 13.6vdc

Absorption - 14.7vdc

Bulk - 14.7vdc

Then if that USB port I gave link to says it will work in 12/24 volt that means that a 14.7 won't hurt it?

Another interesting thing iota said, if I use their smart agm battery adapter, which I will use, then it won't do an equalization cycle. Makes sense? 

BB.

In the Amazon details:

Mount this USB socket and power it with a 10V-28V dc supply. Next you can charge your Phone, Pad, GPS, Camera, PSP, Car DVR, Rechargeable Headset and more.

In general, DC to DC switching power supplies should work from min to max voltage ranges.

Where we got into trouble was with earlier "universal" Auto-Switching power supplies for computers and such. They would "auto switch" based on ~90 to 132 VAC or ~180 to 264 VAC (there is a "natural voltage doubler circuit in a typical AC input power supply). And if you ran the supply between 132 to 180 VAC, it would either "brown out"  or "over voltage".

Modern Power Factor Corrected Power Supplies, usually run from 90-264 VAC range.

You have to read the specifications closely.

-Bill