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Old 07-07-2021, 06:39 PM   #1
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Planning to add solar

I have a, new to me, 2005 Itasca Meridian 36G. Has 3 house batteries, inverter, charges from alternator, and generator. Trying to decide what I need in the mountain of stuff available. What I think I need:

3x 12v100AH LiFePO4
1x MMPT
1x DC-DC charger
1x shunt



So I guess my question is do I have to replace the original inverter? I think I plan to stick with the LA batteries for the chassis, will that change things?
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Old 07-07-2021, 09:29 PM   #2
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You might need a new charger if your existing converter on invert/charger isn't configurable enough to support LiFePO4. I don't like relying on the BMS system (assuming you batteries have one) to protect the batteries. I think you can get more life out of the batteries if you are careful with how you charge them and not over charge them or hold them at a high state of charge. This can be hard to manage with an older charger that isn't configurable.

You're going to need circuit breakers or fuses and cut off switches for your solar.
A battery monitor will be useful to have but your solar charge controller might include one.
A charge controller with a good remote that includes the battery monitor would be ideal.

You might not need the DC-DC charger if you have a battery isolation manager between the house and chassis batteries but the DC-DC charger can be a good way to limit the current from the alternator.
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Old 07-07-2021, 10:02 PM   #3
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Build your own lifepo4 battery

For under $700 you can build your own 280ah lifepo4 battery. There are plenty of videos on the internet that show you how.
I'm planning on using the dc to dc charger not only to charge from the alternator, but also to charge from my current converter which does
not have lifepo4 settings.

I bought this BMS Bluetooth version with fan for mine.

https://a.aliexpress.com/_mPRBOb3



I bought these Cells, but it can take up to 2 months to get them. I ordered them June 4th, so I'm still waiting to get them.

https://a.aliexpress.com/_mqGLfuD

For the charging issue with the alternator I bought a DC to DC charger with lithium settings.

https://smile.amazon.com/dp/B07Q4SVX3M/ref=cm_sw_r_cp_apa_glt_fabc_2VMB4N44YNQTWEFKJB2P


Once I get this in place I'll work on the solar panels.
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Old 07-08-2021, 12:10 AM   #4
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I just pulled the plug after doing all the research and decided to simplify things by skipping Li batteries for now. My config might not be the bee’s knees system, but it surely made it a much more manageable upgrade. I didn’t need to touch my existing converter and my existing FLA batteries still have plenty of life- and the most “green” option is to use up their useful life!

I ended up getting an upgraded MPPT and I’m designing my cabling and placement of all the new solar equipment with the eventual switchover to Li batteries in mind, once my FLA wear out. The biggest change for my rig is placement, as that the Li need to be inside rather than in the under stairs (but exposed) area the FLA currently are. This means my solar controller will be a little further from the FLA than recommended, but I already have some beefy cabling connecting the two locations.

I got a cheap Chinese shunt and device to measure FLA SOC for peanuts. When I switch to Li in a couple years, the BMS are already coming with Bluetooth and ability to check SOC directly on the battery- so that should all be pretty standard and cheaper in the future.

The decision to leave out Li for now meant it was so straightforward:
-Panels and mounts
-Mppt controller (with Li charging profile for future)
-Cabling to hook it into existing circuit
-Resettable fuse between panels & PV controller (protects circuit and gives me a “shutoff” for the panels)
-Fuse between PV controller and battery+
-shunt and SOC meter @ battery -

Everything else is existing, including my WFCO converter, and no need to add DC-DC.

If you do go Li, you need all the above, plus swap out your converter for one with a Li profile (or at least a programmable one), and as mentioned a dc-to-dc to prevent the Li from pulling too much current and possibly burning out your alternator. [some folks swear you don’t need one. If your batteries are always >80% SOC when driving, IMO, they are probably right, otherwise it’s cheap insurance.] Instead of a separate Dc-to-dc and MPPT, you can get a single device to do both those- like https://www.renogy.com/dcc50s-12v-50...ger-with-mppt/
Even with that, you’ll still need a new converter to handle the Li on a/c (gen or shore) power.
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Old 07-08-2021, 08:20 AM   #5
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Thanks guys! The reason I am thinking to go LiFePO4 batteries is that my SLAs are pretty much kaput. If I have to replace, might as well go Li saw a review of the Chins batteries and they seem good and the "price is right"... Thinking of replacing my 3 current SLAs with this:

https://smile.amazon.com/dp/B08N53GF81

I've been looking at the Renogy DC-DC/MPPT:

https://www.renogy.com/dcc50s-12v-50...ger-with-mppt/
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Old 07-09-2021, 05:46 PM   #6
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Quote:
Originally Posted by rblackburn View Post
Thanks guys! The reason I am thinking to go LiFePO4 batteries is that my SLAs are pretty much kaput. If I have to replace, might as well go Li saw a review of the Chins batteries and they seem good and the "price is right"... Thinking of replacing my 3 current SLAs with this:

https://smile.amazon.com/dp/B08N53GF81

I've been looking at the Renogy DC-DC/MPPT:

https://www.renogy.com/dcc50s-12v-50...ger-with-mppt/
My son has a recent Renogy DC-DC charger. His is not multi-stage so can take the LiFePO4 batteries to 14.6V and hold them there. That can be problematic. He's okay with it because he only engages the DC-DC charger when on the road and running 1200W of mini split A/C (100 amp load). The DC-DC charger supplies only 30 or 60A so carries part of the load and never gets the voltage above what the solar controllers are holding (float at 13.6V) (he has 2 kW of solar to do the normal charging). A DC-DC charger with three stages would be preferable.

My experience has been good with Epever MPPT solar controllers.
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Old 07-23-2021, 06:09 PM   #7
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Quote:
Originally Posted by hclarkx View Post
My son has a recent Renogy DC-DC charger. His is not multi-stage so can take the LiFePO4 batteries to 14.6V and hold them there. That can be problematic. He's okay with it because he only engages the DC-DC charger when on the road and running 1200W of mini split A/C (100 amp load). The DC-DC charger supplies only 30 or 60A so carries part of the load and never gets the voltage above what the solar controllers are holding (float at 13.6V) (he has 2 kW of solar to do the normal charging). A DC-DC charger with three stages would be preferable.

My experience has been good with Epever MPPT solar controllers.
If his lifepo4 batteries have a good BMS it will stop the charging when the batteries reach full charge. So there is no reason to worry about over charging the batteries. His solar controller should be set to charge lifepo4 to 14.6v.
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Old 07-23-2021, 06:35 PM   #8
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Something that seems to have been missed on this thread is the purpose of the DC to DC converter, to protect the vehicle alternator from the high draw of the LiFePo batteries. Just something to think about, even if the BMS protects the battery it will not protect the alternator to the best of my knowledge.
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Old 07-23-2021, 06:44 PM   #9
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You didn't say what you're getting for panels. I'd recommend you start out with 4-500 watts worth, and keep to FLA batteries for now. Lots of upgrades needed to switch to Lithium. Try out solar, see how it works with your camping patterns (both use and parking in the sun), and decide on Lithium after a bit of playing.
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Old 07-23-2021, 11:21 PM   #10
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Originally Posted by nvs4602 View Post
If his lifepo4 batteries have a good BMS it will stop the charging when the batteries reach full charge. So there is no reason to worry about over charging the batteries. His solar controller should be set to charge lifepo4 to 14.6v.
You'll have to suggest some "good" BMS models. I have experience with several and none halt charging at 100%. They only halt charging at some voltage that is always higher than one should use (e.g., above 14.4-14.6).

The best I've used is the Overkill. It's great because one can choose his own settings. For instance, one can set the charge cut-out voltage at, say, 14.6 while the solar controller is set to charge only to only 14.4V. Unfortunately, my Lifeblue has a great BMS in most respects, but does not curtail charging until the battery hits 16.0 volts. 16.0 V is higher than anyone should take a 12.8 V LiFePO4 battery.

Because the SOC monitor in a BMS has to sit at 100% for a while as the battery fully charges, the SOC cannot be used to halt charging. A LiFePO4 that has been cycled for a while (weeks) but has not been topped off on any of the charge cycles can sit at 100% for an hour while the battery gets its last 10% of charge. Been there, done that.

The BMS is often given credit for more than it actually does. Most BMS are designed to prevent catastrophic damage, not limit modest abuse that can shorten LiFePO4 life.
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Old 07-24-2021, 10:42 PM   #11
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I'm going to use a Daly BMS with balance leads and Bluetooth app

https://a.aliexpress.com/_mNZIdiJ

I will also use cells to build my battery. And not using the pre-made batteries like BattleBorn's.
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Old 07-27-2021, 10:17 AM   #12
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Quote:
Originally Posted by nvs4602 View Post
If his lifepo4 batteries have a good BMS it will stop the charging when the batteries reach full charge. So there is no reason to worry about over charging the batteries. His solar controller should be set to charge lifepo4 to 14.6v.
A disaster waiting to happen if this advice is followed.
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Old 07-28-2021, 02:57 AM   #13
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A disaster waiting to happen if this advice is followed.
You should explain your comment. If you can't you should not comment at all. I'm curious as to why this would be wrong..
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Old 07-28-2021, 03:41 AM   #14
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Interesting new video from Will Prowse on a new 100aH 12.8v LiFePO4 "Zooms" brand battery on Amazon for $399.

He likes it. (Chins clone. No low-temp charging cutoff, so you'd need that extra. But, $399 . . . )

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