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Newby and some simple questions in my simple mind for a 5th wheel non-solar.

L0veless

New Member
Joined
Jan 25, 2021
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23
My 5th wheel has a converter but no inverter in the electrical panel, current wet battery is going out. want to upgrade to lithium. I have 2 generator that were used twice last year for one night each so we don't do any real boon docking. Watching a lot of videos I feel pretty confident in building the battery. so on to my thoughts.

1. my plan is to build a 12 volt 280ah battery, install 4000w inverter next to the battery then run my 30 amp cord(I use for my generator) from the inverter back into my rigs 50 amp socket. my thoughts are the 5th would think its plugged in and run both 120v and 12v. my draw is about 8-10 amps but would like to hit the air conditioner for an hr to cool things off.

2.The 5th wheels built in charger is for lead acid, hoping it would charge the batteries while driving, knowing I wont get full charge but then when I tie up to shore power I can plug it in. Then I can top off the battery with a lithium charger plugged into a 120 source in the 5th wheel.

3. since I haven't used my generators I'm wanting to leave them home and free up space, weight and maintenance. use this set up going from point a to point b.

3. to me this seems too simple I'm Hoping someone will point out my errors. will this set up "fry" something in the coach?

4.another question my plan is to upgrade my golf cart to 48 volt lithium next year, do I need a 48 volt charger for that or will the 12 volt work?

thank you
 
1. 4000W is a massive inverter for 12V. 4000W/12V = 333A. 50A sockets are powered by 240VAC. You need to sort out 30/50A, 120/240VAC, shore, generator, inverter, etc.

2. Depends on the make and model. "Hope" is not a good plan. Identifying the unit and it's charge parameters is critical.

3. Okay. You'll need to makes sure your battery has enough capacity. Your battery has about as much capacity as running a 4000W generator for 50 minutes.

3. See #1.

4. I assume since you have a 48V charger for your 48V golf cart battery, not a 12V charger. As with the converter, it depends on the charger's voltages.
 
1. 4000W is a massive inverter for 12V. 4000W/12V = 333A. 50A sockets are powered by 240VAC. You need to sort out 30/50A, 120/240VAC, shore, generator, inverter, etc.

2. Depends on the make and model. "Hope" is not a good plan. Identifying the unit and it's charge parameters is critical.

3. Okay. You'll need to makes sure your battery has enough capacity. Your battery has about as much capacity as running a 4000W generator for 50 minutes.

3. See #1.

4. I assume since you have a 48V charger for your 48V golf cart battery, not a 12V charger. As with the converter, it depends on the charger's voltages.
I am an RV fulltimer. That should work. The best solution, which you probably know, would be to buy a high quality inverter charger (Magnum, Victron) which would give you the ability to use specific charge and cut-off parameters that you can customize specifically for lithium. If you have a 50 amp shore input you take one leg out of the main box in your fifth wheel to the inverter/charger and that feeds a subpanel with the circuits you want to be able to power off the inverter. But, that is more seamless and more expensive, not necessary, so yes, your plan will work. Unless you already have the inverter I would consider going with 3,000. Remember you have propane available for the fridge (? maybe you don't) and water heater. I have a magnum 3012 and had few problems other than needing to shut things off to run the microwave etc. I have run the air conditioner for 3-4 hours off a 600Ahr lifepo4 bank but that really taxes everything and if you are in a situation where you don't have shore power, you really can't afford to burn through your batteries. (It is fun to do as an experiment but there really is almost no scenario where it makes sense). I would not design my system with the AC in mind. So I think Snoobler correctly identifies the issue of (1) 4000 watt inverter is huge and will cost you in excess weight, energy expenditure and heat production) (2) while the lead-acid charger will work short term, it is not ideal and you need to be able to really target your charge and discharge parameters or you both risk the life of your Lifepo4 and the ability to use it optimally. If you are going to spend the money to do that I would disconnect the lead-acid charger and get an inverter/charger that works together and actually can do everything properly. Finally, Snoobler does not mention this but you really need to add a god ammeter to the picture. Voltage readings on a lifepo4 battery are extremely misleading. You need to know the actual amps in and amps out to the battery or you will get stuck. I suggest the Victron 700 series or the Bogert trimeter. The Aili (spell?) unit on amazon is not perfect but it will work leagues better than relying on your fifth wheel's existing voltage indicator. If I was just going to go out for a week a year or a weekend now and then I would trust what you propose as long as you add at least Aili ammeter. However much much better systems are available. This web site deals with solar which you can ignore and does not include LiFEPo4 batteries (come back here for that) but does an excellent job of discussing how to incorporate an inverter into an rv. http://www.jackdanmayer.com/rv_electrical_and_solar.htm https://www.amazon.com/AiLi-Voltmet...t=&hvlocphy=1013377&hvtargid=pla-569360505489
 
I am an RV fulltimer. That should work. The best solution, which you probably know, would be to buy a high quality inverter charger (Magnum, Victron) which would give you the ability to use specific charge and cut-off parameters that you can customize specifically for lithium. If you have a 50 amp shore input you take one leg out of the main box in your fifth wheel to the inverter/charger and that feeds a subpanel with the circuits you want to be able to power off the inverter. But, that is more seamless and more expensive, not necessary, so yes, your plan will work. Unless you already have the inverter I would consider going with 3,000. Remember you have propane available for the fridge (? maybe you don't) and water heater. I have a magnum 3012 and had few problems other than needing to shut things off to run the microwave etc. I have run the air conditioner for 3-4 hours off a 600Ahr lifepo4 bank but that really taxes everything and if you are in a situation where you don't have shore power, you really can't afford to burn through your batteries. (It is fun to do as an experiment but there really is almost no scenario where it makes sense). I would not design my system with the AC in mind. So I think Snoobler correctly identifies the issue of (1) 4000 watt inverter is huge and will cost you in excess weight, energy expenditure and heat production) (2) while the lead-acid charger will work short term, it is not ideal and you need to be able to really target your charge and discharge parameters or you both risk the life of your Lifepo4 and the ability to use it optimally. If you are going to spend the money to do that I would disconnect the lead-acid charger and get an inverter/charger that works together and actually can do everything properly. Finally, Snoobler does not mention this but you really need to add a god ammeter to the picture. Voltage readings on a lifepo4 battery are extremely misleading. You need to know the actual amps in and amps out to the battery or you will get stuck. I suggest the Victron 700 series or the Bogert trimeter. The Aili (spell?) unit on amazon is not perfect but it will work leagues better than relying on your fifth wheel's existing voltage indicator. If I was just going to go out for a week a year or a weekend now and then I would trust what you propose as long as you add at least Aili ammeter. However much much better systems are available. This web site deals with solar which you can ignore and does not include LiFEPo4 batteries (come back here for that) but does an excellent job of discussing how to incorporate an inverter into an rv. http://www.jackdanmayer.com/rv_electrical_and_solar.htm https://www.amazon.com/AiLi-Voltmet...t=&hvlocphy=1013377&hvtargid=pla-569360505489
Dhasper,
Thank you for your input, Posted this same question on an RV board,only mistake brought up was I for got to isolate the battery from the coach.
I don't want to go with any thing hard wired yet only because we might sell soon and upgrade Coach. as stated earlier when tied up to shore power I can hook up portable Lithium charger to top off. I can easily take everything replace with a wet battery. Decided on a 3,000/6000 watt inverter. No need for anything bigger since I will only draw 10- 15 amp at most other then air conditioner start up. fridge runs propane so very little usage there and water heater is both propane/ electric so little usage there.

again thank you for your input and the link
Happy Trails
 
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