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12v Batty for RV Build

mykayel

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Joined
Feb 19, 2022
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I'm planning on building a building a 304ah (or 280ah) batty for my RV and I'm looking for a little advice. I've figured that I use about 50ah a day, I haven't measured this with a shunt, but only based on a two day trip where a drop in 100ah battery barely made it (based on measuring voltage) and I would like to be able to do a 4 day trip with room to spare. I would like cold temp protection as my batteries sit on my trailer tongue and I just don't want to worry about having issues. I will only be using the battery for running my RV's 12v systems and I do not plan on using an inverter. And I would really only be relying on the battery a few times a year in the spring and fall as otherwise in the summer we typically have electric sites as it gets too hot here.

The building a battery seems like a no brainer to me as I can get a set of 304ah cells for $500.

One of the things I am stuck on is which BMS to use and would like recommendations. I don't need high amp capacity. Bluetooth would be nice, but I don't think it is necessary. I want a quality unit that I won't have worry about failing. I've ready great reviews about the Overkill BMS, but at $140 I was looking for a cheaper option if there is a good option.

Lastly, I figure I will have to make my own "battery" box and I was curious if anyone had examples that they have done.
 
I found battery boxes more of a pain to make than I thought, and the nickel and dime stuff added up, so if you can find a case that would fit your 304 ah battery that would make it easy. If you can downsize to 280 ah, there’s plenty of these available from different vendors:


I build my own case, but it was a huge pain. From a vendor stateside shipped could be $110. This case looks like you could remove it easily, but the one I built is not getting removed.

I have an Overkill BMS 8S 24 volt. THat is actually a rebranded JBD BMS. Still has the sticker with the JBD part # on it. You could look at JBD. I consider some way of monitoring mandatory. Bluetooth is the only way for me. THe other ways I found don’t work for me: get up and look at a monitor, hooked through a USB (not easy for me), or not monitor at all.

The Lithium I built is in my signature block, RV Build part 2
 
The new heated chins model would check all of the boxes, heating pads, bluetooth, sealed plastic container for outdoor storage, etc. I know you say you want to DIY, but it's really hard to argue with these new models.
Check out Will's videos from earlier this week and follow the links to see the prices.

If you were to move them inside the RV, you would be better off and might not even need to pay for the heated version. The batteries like to live in the same temp ranges you would find comfortable, so keeping them inside should improve the lifespan of the units and improve reliablity.
 
The new heated chins model would check all of the boxes, heating pads, bluetooth, sealed plastic container for outdoor storage, etc. I know you say you want to DIY, but it's really hard to argue with these new models.
Check out Will's videos from earlier this week and follow the links to see the prices.

If you were to move them inside the RV, you would be better off and might not even need to pay for the heated version. The batteries like to live in the same temp ranges you would find comfortable, so keeping them inside should improve the lifespan of the units and improve reliablity.
The smart/heated Chins 300ah is $1400 which is a lot more than I want to spend; I should be able to do the same for about half that cost (or is my goal). I wish I could move the battery inside but is not practical for my RV. Even with one of the larger capacity drop in's, I'm still probably going to have to make/find some sort of battery box to accommodate such a larger battery and the connections for my disconnect, shunt, and RV wire hookups.
 
The smart/heated Chins 300ah is $1400 which is a lot more than I want to spend; I should be able to do the same for about half that cost (or is my goal). I wish I could move the battery inside but is not practical for my RV. Even with one of the larger capacity drop in's, I'm still probably going to have to make/find some sort of battery box to accommodate such a larger battery and the connections for my disconnect, shunt, and RV wire hookups.
If you do buy cells from china for DIY, you're looking at up to a 3 month wait for delivery, 1 and 1/2 if youre lucky.
 
One of the things I am stuck on is which BMS to use and would like recommendations. I don't need high amp capacity. Bluetooth would be nice, but I don't think it is necessary. I want a quality unit that I won't have worry about failing. I've ready great reviews about the Overkill BMS, but at $140 I was looking for a cheaper option if there is a good option.

You get what you pay for. Sure, you can go with a cheap Daly BMS. But be sure to buy two so you have a spare when the first one starts failing.

The JBD BMS has proven to the be very reliable. Ordering from Overkill Solar was a lot easier for me than buying a JBD from China as I wasn't sure what I was ordering from the Chinese websites. The warranty from Overkill can't be beat.
 
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