Do these batteries look appropriate? Great deal.

[OldSmokey]

Here's the breakdown of my power usage:

Lights: ~200W total in the RV. On for 5-6 hours a day max.
Water: powered by 90W pump, only on when using water (let's say 1 hour a day?)
Laptop: ~90W power adapter. Generally on this thing a lot, let's say 8 hours a day (more now, but traveling, I assume that will decrease).
Phone: using as hotspot, will need to keep plugged in = 10W for ~12 hours day
Speakers: 120W x 2 = 240W, plus about 200W max from the subwoofer and its amp, and then I have an audio interface that uses 24W = ~470W total, probably on for 6 hours out of a day.
Misc: random power tools, things I'm using occasionally when working on projects, let's say 200W, for 1 hour a day.

Total power per day:
+200W for 6 hours = 1200Wh
+90W for 1 hour = 90Wh
+90W for 8 hours = 720Wh
+10W for 12 hours = 120Wh
+470W for 6 hours = 2820Wh
+200W for 1 hour = 200Wh

TOTAL: 5150Wh / day

With that said, seeing as I'd be smart to have a battery bank that won't see < 50% DOD, 10kwh seems like a good mark, especially considering I should plan for reserves. Yeah?

As for the solar panels, yeah, I had planned to have about 1500W on the roof. There should be plenty of room for 6*250W or 300W panels. I also had ideas to put them on the sides, on hinges, that I'd prop up when stationary, but only if that's necessary.

@OldSmokey... the T-105 is a 6V battery? What's the deal here, guys? Should I not have any batteries in parallel at all, or is that always going to be a requirement at some point, to meet the 12V, whatever Ah I need (10kwh @ 12v = ~800Ah). With a 6V battery, I'd go in series twice, then everything else in parallel. I'm a little confused as I don't see a way around having to do some in parallel.

8x T105 is approx 10.8 Kwh like your initial value, but that's not your real issue here. your power estimate I think is way off..


My wife and I boondock a lot and our first power estimate was high like yours, after some analysis our figures decreased a lot.
here are some estimates based on real world numbers that we average with our RV combined with your consumption with an inverter for 120V loads.


first are 12 Volt loads..

Lights: we have 18 lights in our RV, they are LED and 5 watts each. Rarely do we have them all on at one time, our average use is
6 on at any one time so call that 30 Watts for 5 hours = 150 Wh

Water: Our pump is typical rv and is a 100 Watt motor, we have 2 showers at 5 mins each and approx 10 mins other usage
so call that 20 mins at 100 W per day. ( 20 minutes runtime is a LOT of water.. ) = 34 Wh

Fridge on propane is approx 18 W and assume 75% duty cycle 18 * 24 * 0.75 = 324 Wh

Phone via 12 V USB adapter : 10W * 12 = 120 Wh

total 12 Volt Wh rounded up is approx = 628 Wh



next is 120 V loads via inverter.


Speakers, well we dont have any, but I assume you will not be at full tilt with these for 6 hrs ?
perhaps a reasonable estimate is more like 200 W so let's say 200 * 6 = 1200 Wh

Misc:.. ok, 200 it is .. = 200 Wh


Laptop: I have a Dell laptop with 90W supply, in actual use my Kill-A-watt shows an average demand of 25W.
so thats 25W for 8 hrs = 200 Wh

so this total is : 1600 Wh, now allow for inverter efficiency of 85% = 1882 W

your total battery Wh is now approx: = 1882 + 628 Wh = 2510 Wh


the second issue is that you have not accounted for cloudy days.
we have experienced 3 consecutive days without sun, you need capacity or "autonomy" to cover this before you
get the generator out. if you read Sunking's tutorial he states to cover this with battery capacity for 5 days

so using 2510 Wh and 50% DOD we get approx 2510 Wh * 5 days * (100%/50%) = 25100 Wh and using 48V = 523 Ah capacity
if you go 4 days then 2510 Wh * 4 Days * (100%/50%) = 20080 Wh at 48 V = 418 Ah.. that's a good match for a 6 Volt Trojan L16P
so eight of those would cost approx $2400 and weigh approx 910 lbs

1500 W panels requires a 30A minimum controller at 48 V
charge rate is a little low at C/13 however

also you will need a 48V to 12V buck converter to provide 12V power
and a combined 48V inverter/charger is a reasonable option.


please read the offgrid and battery tutorials to get a better idea..

[zamboni]

I ruined a half dozen Makita 9.6 volt batteries using a MSW inverter.

Now and then i hear a story like this, but i don't understand why it happens and have never found an explanation. Any ideas?

The charger is just a transformer so it shouldn't care if it's seeing MSW or PSW -- the xfmr would smooth out the MSW input anyway, right? But the batteries are still getting ruined, presumably over-charged? Does something in the charger's controls rely on a perfect sine input to set charging voltage or duration somehow? I can't even guess, but this is one of those tiny issues that i can't understand and it gets under my skin.

The closest I've found via Google is a statement that the types of cordless tool battery chargers which are susceptible to MSW usually "have a warning label stating that dangerous voltages are present at the battery terminals when charging." Which might mean something to someone on here, but it still doesn't explain the situation to me.

[Mike90250]

Devices built for sine wave power , dont always like square wave power. Anything inductive generally consumes 20% more power as heat. Chargers vary in their performance, early DeWalts died in minutes, later models lasted forever. Kill-A-Watt meters die in minutes. The difference in the power quality between square and sine wave is huge,

[zamboni]

Devices built for sine wave power , dont always like square wave power. Anything inductive generally consumes 20% more power as heat. Chargers vary in their performance, early DeWalts died in minutes, later models lasted forever. Kill-A-Watt meters die in minutes. The difference in the power quality between square and sine wave is huge,

Littleharbor did say he smoked the batteries without mentioning the charger. I can easily accept the chargers dying on MSW input, but this is not the first time i've heard someone say the batteries were ruined. I realize i could just be getting tripped up by word choice, but nobody ever says "batteries and charger". I guess if the batteries are toast the charger must be, too...

Aside from trial and error, can you advise a way to tell if some as-yet-invented device will be cooked by a MSW inverter? I've heard some people say that if it's got a "regular" cord and not a wall-wart, that is an indicator. Truth?

[Mike90250]

Aside from trial and error, can you advise a way to tell if some as-yet-invented device will be cooked by a MSW inverter? I've heard some people say that if it's got a "regular" cord and not a wall-wart, that is an indicator. Truth?

Nope, its a wild guess. All depends on what the circuit is. power bricks are now often switch mode supplies, and should be insensitive to sq or sine wave.

[littleharbor]

Littleharbor did say he smoked the batteries without mentioning the charger. I can easily accept the chargers dying on MSW input, but this is not the first time i've heard someone say the batteries were ruined. I realize i could just be getting tripped up by word choice, but nobody ever says "batteries and charger". I guess if the batteries are toast the charger must be, too...

Aside from trial and error, can you advise a way to tell if some as-yet-invented device will be cooked by a MSW inverter? I've heard some people say that if it's got a "regular" cord and not a wall-wart, that is an indicator. Truth?

The charger didn't act strange other than give me a charged light and the batteries would last about 5 minutes before they died, ala a sulphated FLA battery. I ended getting an all new Nimh. 18 volt Makita cordless setup with a different battery format so I trashed all the old batteries. BTW in case anybody's interested, the old batteries were the long 9.6 volt NiCad's.

[Sunking]

The charger didn't act strange other than give me a charged light and the batteries would last about 5 minutes before they died, ala a sulphated FLA battery.BTW in case anybody's interested, the old batteries were the long 9.6 volt NiCad's.

No offense offered here but you cannot compare FLA to Nickel. They react the same when dead, they full the charger thinking they are charged up, then when you put a load on them crash. But internally and the failure mode is completely different.

Nicads and NiMh have on eneat thing about them, they can be sometimes be restored to usable capacity if you have a charger made to do it like one of the Hobby chargers.

[littleharbor]

I realize we're talking apples and avocados here with the two different technologies. The description I gave was based on the similar ,"full-no capacity-empty way the batteries acted. I was told by another tech one time that the batteries could be reconditioned but it was a long process and he didn't seem to care to offer any more details. BTW, that was decades ago and now that we're in the lithium cordless tool battery age those old Ni-cad's seem quite primitive.

[Sunking]

Restoring NiCd and NiMh is not hard. NiMh is still a popular and good choice for power tools and why you still see them offered. If you want to know more just shout.

[littleharbor]

I do have some 18 volt NiMh. batteries that APPEAR to fully charge, in 10 minutes, and will run the drill for a brief time. Next time I go to use this tool the batteries are dead. They won't hold a charge. Still a very good drill motor I only use for honey do's around the house.

BTW I have adapters for the lithium batteries making them usable in the older format NiMh tools.
Sure I'd like to learn how to recondition these batteries. Bear in mind I'm not an electronics guy, just a dumb retired carpenter, so if you can dumb it down that would help.

[rw3iss]

OldSmokey Thank you for the breakdown, definitely helps. My estimation is probably-definitely off a decent bit, realistically. I have a kill-o-watt meter, will plug it into my entire setup here and see what gives.
And thanks a lot zamboni, very useful as well. I'm gonna read up some more and maybe get back to this thread a little while from now, so excuse me if I'm a bit absent.
Cheers, guys. Thanks a ton for all the help.

[Sunking]

I do have some 18 volt NiMh. batteries that APPEAR to fully charge, in 10 minutes, and will run the drill for a brief time. Next time I go to use this tool the batteries are dead. They won't hold a charge. Still a very good drill motor I only use for honey do's around the house..

OK not sure what your capabilities are or equipment, but here is the readers digest version. You must do a deep deep discharge to around 0.9 volts per cell so that the cells do not climb above 0.9 volts when rested. You may need to go down to 0.5 vpc to knock the memory off. The crystals has dried out and settled in the bottom. You got to heat them up to break up the crystals and re-hydrate. No delussion they will never be full capacity but 50% is realistic and usable.

Then perform a normal charge at C/2 which will not take immediately followed by a Forming Charge. A FC is a constant current C/10 charge for 10 to 16 hours until the cells get warm. A constant voltage is not going to work on Nickel battery, it must be CC and the voltage can go as high as 1.6 vpc.

Here is some more details, but I will warn and say it takes a special charger capable of doing this like a Hobby Charger. There is a risk of venting. Many hobby chargers has a Nickel Reforming program. If you like to tinker with batteries, consider getting a hobby charger like an iCharger with a 12 volt 10 amp power supply. You can charge any kind of battery of today and tomorrow, or even make up your own algorithm. You can analyze the battery to see it is even worth messing with. I make adapters to charge all my power tolls with them plus all my RC plane batteries. For $150 you get a great mult-tasker that can charge lithium, nicket, lead, or whatever. I can hook you up with details, just ask.

[littleharbor]

Thanks Sunking, I will do some more reading and look into the hobby charger.

[zamboni]

Nope, its a wild guess. All depends on what the circuit is. power bricks are now often switch mode supplies, and should be insensitive to sq or sine wave.

Dang, that's frustrating. I've got PSW but always thought it's nice to have MSW as a budget option if you have a well-defined use situation. But based on what you're saying above, the only thing i'd dare plug into a MSW is a resistive heater.

So a simple "visual inspection" can't do it...Is there any way to test a given device (like with a DMM or Oscilloscope) -- perhaps while it's on mains power -- to see if MSW will smoke it? I'm thinking for example of the OP's stereo equipment, which likely has just a regular 120VAC plug, and which likely is also too expensive to risk a "see what happens" testing approach.