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Just Starting

TomM

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I am just starting to plan a solar/lithium battery system for my 5th wheel for both boon docking and camping at normal RV parks. The plan is to follow Will's 24 volt / 2000 watt design and components. The book is on order. I have not done a power budget yet, but when I boondocks with just a generator and lead acid batteries, I used 30-40 AH per 24 hr period.

I have not started buying parts yet as I have some questions:

1. I notice the plan does not include an isolation switch between the 24-12 volt converter and the 5th wheel 12V buss. That seems like a good idea to me. Any comments?

2. If don't have said isolation switch, what happens when I hook the 7-way connector from my truck to the 5th wheel? When it supplies 12V to the 5th wheel buss will that feed back into the 24V system?

3. What happens when I connect shore power to the 5th wheel? Then there will be two systems supplying power to the 120V AC system and the 12V DC buss.

4. If there are several cloudy days and the batteries run out, how do I recharge the 24V batteries with shore power or the generator?

Here is the proposed major component list from Will's suggested 24V:

1. 6 Renogy 100W solar panels, three sets of 2 panels hooked in series to provide ~36V for charging the 24V batteries, ~16 amps charging current.
2. EPEver MMPT MT50, 1200W, 24V designed for 150V and 40A.
3. 2 SOK 200AH, 12V LiFePO4 batteries hooked in series to produce 24V.
4. Giandel 3000W, 24V, pure sine inverter to run lights and the microwave.
5. UXCel 24-12V converter, 40A

Feedback?

Thanks, Tom
 
30-40Ah @ 12 or 24V?

1. never a bad idea.
2. only if the 7 way connector provides a means of charging the 5th wheel 12V battery.
3. Depends on how you configure it.
4. With an inverter/charger instead of just an inverter.

Components:
1. Fine, but Renogy tend to be a little pricier for no good reason, and their support is notoriously sucky based on feedback on this forum. 3S2P may be a little better for efficiency for low light charging, which may be advantageous for panels on a flat roof.
2. Fine.
3. Meh, but I'm a snob. I'd rather build a 24V 280Ah battery for $1k rather than buy SOKs.
4. Fine, but it doesn't have a charger function.
5. Maybe

Is your trailer 30 or 50A?
 
OK, so how do you build a 24V 280Ah battery for $1k? I looked at building my own battery but based on the links on Will's site it was actually more expensive than the SOK for same 200AH.
 
You buy 8 280Ah cells through trusted sources on Alibaba. Takes 45-60 days to get here. I bought 9 in case there was an issue with one of them, and the shipped price was $969. I'm looking for a suitable BMS. I've found a number of options for less than $150.

30A simplifies things since there's no concern with the 240V associated with 50A.

Imagine installing an inverter charger/between your RV umbilical and the AC panel. This would entail simply attaching the umbilical to the unit's AC-in and then attaching the inverter output to where the umbilical was attached. If you have an automatic transfer switch with an onboard generator, there's just an additional layer to deal with.

This essentially leaves the trailer system intact and functional as-is on the existing 12V system with the converter powered by the off-grind inverter. This is not particularly efficient, but if you have plenty of capacity, it's offset by the convenience.

This inverter:


is about $100 more than the Giandel but with a charger function as well. Thus, if the umbilical is powered via shore or generator, it will also top-off the 24V battery.
 
I opened an account with Alibaba and looked at 280AH cells. There seems to be 1000 suppliers. How do you choose one?
 
My sig is getting too fluffy, had to trim it down somewhat. Also it appears that if people are using phones to access the site, some do not see signatures... I cannot verify that myself as I use a PC to surf the web....

BTW: She only has 700 280AH cells left (as of end of business Nov.23) before the next batch comes in at a higher price point (EVE is upping cost for everyone). S&H costs are improving as she's connected with a new shipping broker with better pricing, that should be reflected soon.

Link to Amy's shop.
Shenzhen Luyuan Technology Co., Ltd. - Lifepo4 battery, LTO battery (alibaba.com)
 
Has anyone tried the BMS from Amy? I am looking at 8 lifepo4 cells, 280 Ah, for $931 shipped. If her BMS is good I will include that in the order.
 
Amy is awesome! I just bought 8 LiFePO4 280Ah cells with buss bars and bolts for $843 delivered to my house. I decided to use the Overkill Solar BMS.
 
Those are Chargery's but she will likely be carrying a couple of other others to choose from. There will be more goodies for a battery builder / assembler added to support the clients for a one stop shopping solution if so desired... also getting several bits in one shipping box saves bucks for everyone... that also is an extra bonus...
 
The Overkill BMS arrived a couple of days ago, the (8) 280Ah LiFePO4 should ship tomorrow.
 
I want to re-post the link to Amy's shop:
Link to Amy's shop.
Shenzhen Luyuan Technology Co., Ltd. - Lifepo4 battery, LTO battery (alibaba.com)

Amy has been fantastic. I did, however, have an issue that was not her fault. Initially Alibaba would not accept my credit card so I had to click on the "Appeal" button and send additional identifying information. Alibaba was supposed send me an e-mail when my card was approved but they never did. I finally had to contact Alibaba customer service to find out my card had been approved. Amy had no input to any of the financial approval.

Once my card was approved she had the cells shipped in two days.
 
Attached is my proposed wiring diagram for the 24V system. Please look it over. My plan right now is to manually isolate the system when on shore power. I wish now I had used and inverter/charger with an auto transfer switch.

Component list:
1. 3 Rich Solar 200W, 24V solar panels hooked in parallel to provide ~37V, ~16 amps charging current (not ordered).
2. EPEver MMPT MT50, 1200W, 24V designed for 150V and 40A (not ordered).
3. Home built 280Ah, 24V LiFePO4 battery. 8 cells ordered and in transit.
4. Overkill Solar BMS for 8 cell, 24V LiFePO4. Received.
5. Giandel 3000W, 24V, pure sine inverter to run lights and the microwave. Received.
6. UXCel 24-12V converter, 40A. Received.
 

Attachments

  • 24V Wiring Diagram pdf.pdf
    75.7 KB · Views: 7
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