|
| Author |
Message |
pabear89
Member
|
# Posted: 16 Jul 2020 01:50pm
Reply
Have been setting up my coach for living in the woods.
I have been building up my power station to keep from running the gen and testing as I go.
What I have so far is a 6000w inverter powered by 3 commercial grade 1475 amp napa batteries with 800w solar system charging them with another 400w set up to be added soon.
As of now it is running a large fridge that pulls 35w running (per meter) and powering the coach 12v system.
It is keeping the batteries charged completely without having to start the gen.
I can plug in the 120v power cord to the coach to the inverter and run the 120v plugs and appliances.
My coach has a 55 amp converter that charges the battery when shore power is hooked up.
What would be the problem with leaving the converter on and it charging the battery bank powering the inverter?
The converter pulls 7 amps to run and supplies 55 amp charge output.
My power usage is lees than the amount of the power the converter is supplying so would it keep the battery bank charged at night and help back up the solar during the day?
Goal is to not run the gen if i can.
Thanks for any info you can supply to someone new to this off grid living.
|
|
Brettny
Member
|
# Posted: 16 Jul 2020 04:56pm
Reply
Your wanting to use your onboard charger to charger your battery bank via your inverter connected to the batterys your trying to charge with the onboard charger?
Just to clarify your going to charge your batteries useing your onboard charger that requires 120v and not run your generator?
|
|
pabear89
Member
|
# Posted: 16 Jul 2020 06:35pm
Reply
yes but more to maintain the bank when the solar panels are dark.
I had the coach hooked to the inverter with 2 batteries and it allowed the 120 plugs and converter to work but the coach was hooked to the 3rd battery alone.
It charged the battery fine.
Was tossing the thought of hooking the 3rd battery in line to spread the load and keep from running the gen.
|
|
ICC
Member
|
# Posted: 16 Jul 2020 06:52pm
Reply
I am not following the power flow.
There is a battery bank that is charged by some solar panels.
There is an inverter powerred by that battery bank that runs assorted things.
There is a generator but we don't want to run it, so we will not count that.
You are in the woods, so there is no shore power, unless the generator is run but we are not going to do that.
The coach has a converter like most RV's do. The converter is usually powered by shore power which in the woods there is none. Is that correct? No shore power, no generator run?
So if that assumption is correct where is the power to operate the converter and charge the batteries coming from?
I must be misunderstanding something?
|
|
pabear89
Member
|
# Posted: 16 Jul 2020 07:04pm - Edited by: pabear89
Reply
shore power is the inverter when the coach is plugged in to it for short time to charge the 3rd battery for coach.
Right now the solar panels are hooked to the 2 battery bank that powers the inverter.
Have been using the inverter to run the large fridge and assorted power tools during the day and the 800w solar is keeping up.
have a 400w panel set to hook to the 3rd battery but not there yet.
The gen is a back up for winter as here in the PNW sun is not always dependable.
My thought is making a loop from the inverter using the coach converter to maintain the battery bank and hook the 3rd battery inline.
So as of now the coach only charges the 3rd battery when plugged in to the inverter. it has no solar yet so it needs a small charge every 3-4 days from the coach converter but will have solar soon to keep from having to do that.
more confused yet?
|
|
mj1angier
Member
|
# Posted: 16 Jul 2020 07:50pm
Reply
So battery bank 1 is the starting battery for camper
Battery bank 2 is the deep cell bank being charged by solar.
You want to charge bank 1 with bank 2 buy using inverter hooked to on board converter, right?
Yes, it will work but is wasting a lot of juice by controverting from 12v to 110ac back to 12v
If bank 1 just need a small amount to keep it topped off, I would just get it a small solar panel for it.
|
|
ICC
Member
|
# Posted: 16 Jul 2020 08:27pm
Reply
Quoting: mj1angier Yes, it will work but is wasting a lot of juice by controverting from 12v to 110ac back to 12v
That is the key.... using some DC battery power to run an inverter that produces AC that is then put thru a converter to provide DC to charge another battery is very wasteful. I have trouble understanding the logic that would make anyone believe that was okay. As described the process will work, but is a waste.
|
|
ICC
Member
|
# Posted: 16 Jul 2020 08:31pm - Edited by: ICC
Reply
The Lead Acid battery is not 100% efficient at storing electricity - you will never get out as much as you put in when charging. Overall, an efficiency level of 85% is often assumed.
The efficiency will depend on a number of factors including the rate of charging and discharging. The higher the rate of charge or discharege, the lower the efficiency.
The state of charge of the battery will also affect charge efficiency. With the battery at half charge or less, the charge efficiency may be over 90%, dropping to nearer 60% when the battery is above 80% charged. That is one reason the absorb stage takes so long compared to the bulk stage.
The same thing applies to an inverter. There will also be losses as most inverters might reach 85% efficiency under some conditions; maybe less at times.
Everytime the energy is changed from one type to another we lose efficiency.
|
|
|
pabear89
Member
|
# Posted: 16 Jul 2020 08:35pm
Reply
No not the idea i'm working thru.
I want to keep the coach plugged into the inverter so I have the 120v plugs working to use the tv, microwave and coffee pot.
It works now as long as there is sun to the panels but will drain down using it at night watching tv.
I have a 400w panel set for the 3rd battery.
My thought is after the panels are set hooking all 3 batteries in parallel to the inverter.
Now each battery will have 400w solar controlled charge with sun.
If I plug the coach into the inverter, its converter will be sending 55 amps to the battery bank as needed.
Sort of my hamster wheel circling the power.
|
|
ICC
Member
|
# Posted: 16 Jul 2020 08:47pm
Reply
Quoting: pabear89 If I plug the coach into the inverter, its converter will be sending 55 amps to the battery bank as needed. Sort of my hamster wheel circling the power.
No. That is like looking for a perpetual motion machine. No such thing.
|
|
pabear89
Member
|
# Posted: 16 Jul 2020 09:02pm
Reply
So its like BigFoot and Unicorns not possible till someone finds it.
guess I'll keep dreaming.
|
|
ICC
Member
|
# Posted: 16 Jul 2020 09:06pm - Edited by: ICC
Reply
Dream on. 
|
|
Brettny
Member
|
# Posted: 17 Jul 2020 07:46am
Reply
Quoting: ICC No. That is like looking for a perpetual motion machine. No such thing.
This is where I was going but wanted to make sure I was reading things right. Lol
|
|
ICC
Member
|
# Posted: 17 Jul 2020 09:25am
Reply
Quoting: mj1angier If bank 1 just need a small amount to keep it topped off, I would just get it a small solar panel for it.
That is the best solution for the starting battery in an RV. Simple straight forward solution that works. I do that on my RV as well as having small solar chargers on the trucks and equiopment that may sit un-used for months at a time.
Should keep in mind that un-necessary cherge cycles, as in the described system for DC-AC-DC causes wear and reduces lifetime total cycles.
|
|
Brettny
Member
|
# Posted: 18 Jul 2020 09:00am
Reply
How long do you expect not to run the RV engine? Any battery that is in decent condition should be able to go 6 months with out a charge. If you want it to have it's own solar pannel for a backup remember that you alreaty have that in the forum of a whole other battery bank, 120v charger and generator.
You could also use a marine 2 bank battery switch. They are not that much money and it gives you the ability to charge and start the RV off both banks, bank 1 or bank 2.
https://www.ebay.com/itm/Pactrade-Marine-Boat-Dual-Battery-Selector-Disconnect-Switch -w-Lock-250A-6-32V/273483471245?epid=19002490924&hash=item3face2998d:g:tzYAAOSw6YtZOa Pw
There are cheaper ones but this is a name brand with a key.
|
|
Aklogcabin
Member
|
# Posted: 18 Jul 2020 09:54am
Reply
Guess I’m I bit crazy too. I don’t see it as perpetual motion as the sun energy and gasoline for the generator are added to provide for the energy used. Genny n sun charge the batteries. Value depending on the price of gas.
|
|
|
