please advise: building my 1st 12V LiFePo4 battery for my RV

cmpct_cmpr

New Member
Joined
Sep 28, 2020
Messages
11
Hi folks,

came across @Will Prowse 's videos on Youtube just recently - amazing, thank you so much for the good work and your willingness to share your knowledge!

I live in Germany and started to dig into solar power on my small RV just some months ago, this is my setup:

2 x 100W flex panels on the roof, in a serial circuit
1 x Votronic charge controller SR220 duo digital, it has temperature control on the battery and an extra display (V/A/W/Wh)
The battery is still my old 12V lead-acid with 75 Ah.
Since this week, I have an Ective pure-sinus-converter with 1500W attached to the battery - what a joy to have 220V (standard voltage in Europe) in the RV when not connected to shore power at a campsite...

Next project: a bigger and better battery. I'd love to get a LiFePo4, but the prices!
After having watched some of Will's videos, I decided to give a DYI build a try.

cells
I plan to buy 4 of these 200Ah cells I found on Aliexpress:
https://www.aliexpress.com/item/400...=20200928122400251350816012500005223910_1&s=p
They ship from Poland, which is faster and avoids problems with customs charges. The cells are about $ 632
  • Do these seem ok, and reasonable?

bms
I am lost when it comes to a BMS. I'd like one with Bluetooth that works on my iPhone, just to take a look at the stats from time to time.
  • As far as I understood, I do not necessarily need temperature control, as my solar charger already has a temperature-sensor?
  • How many constant A should the BMS be able to deliver, given the 1500W converter?
  • Do I need to "program" the BMS? (I'd rather not!)
  • Can anyone recommend one that is available in Europe?
case
Finally, I want to put all in a box and replace my current battery with it. It is mounted under the drivers seat, so space is scarce, I have about 320 width, 240 length, 220mm of height available. This should work out well, the single cells are 174 x 57 x 201mm.

solar charger compatibility
I can change the settings of the solar charge controller to adjust its loading to a LifePo4.
  • Is this ok?

shore power charger compatibility
There's a built-in charger for the batteries in the RV, as soon as it is connected to shore power. It is optimized for gel or lead, it cannot be reconfigured to LiFePo4.
  • Is this a problem?

I appreciate your answers, comments and advice!
 

snoobler

Solar Honey Badger
Joined
Jul 10, 2020
Messages
8,430
Location
HBR, AZ
Hi folks,

came across @Will Prowse 's videos on Youtube just recently - amazing, thank you so much for the good work and your willingness to share your knowledge!

I live in Germany and started to dig into solar power on my small RV just some months ago, this is my setup:

2 x 100W flex panels on the roof, in a serial circuit
1 x Votronic charge controller SR220 duo digital, it has temperature control on the battery and an extra display (V/A/W/Wh)
The battery is still my old 12V lead-acid with 75 Ah.
Since this week, I have an Ective pure-sinus-converter with 1500W attached to the battery - what a joy to have 220V (standard voltage in Europe) in the RV when not connected to shore power at a campsite...

Next project: a bigger and better battery. I'd love to get a LiFePo4, but the prices!
After having watched some of Will's videos, I decided to give a DYI build a try.

cells
I plan to buy 4 of these 200Ah cells I found on Aliexpress:
https://www.aliexpress.com/item/400...=20200928122400251350816012500005223910_1&s=p
They ship from Poland, which is faster and avoids problems with customs charges. The cells are about $ 632
  • (1) Do these seem ok, and reasonable?

bms
I am lost when it comes to a BMS. I'd like one with Bluetooth that works on my iPhone, just to take a look at the stats from time to time.
  • (2) As far as I understood, I do not necessarily need temperature control, as my solar charger already has a temperature-sensor?
  • (3) How many constant A should the BMS be able to deliver, given the 1500W converter?
  • (4) Do I need to "program" the BMS? (I'd rather not!)
  • (5) Can anyone recommend one that is available in Europe?
case
Finally, I want to put all in a box and replace my current battery with it. It is mounted under the drivers seat, so space is scarce, I have about 320 width, 240 length, 220mm of height available. This should work out well, the single cells are 174 x 57 x 201mm.

solar charger compatibility
I can change the settings of the solar charge controller to adjust its loading to a LifePo4.
  • (6) Is this ok?

shore power charger compatibility
There's a built-in charger for the batteries in the RV, as soon as it is connected to shore power. It is optimized for gel or lead, it cannot be reconfigured to LiFePo4.
  • (7) Is this a problem?

I appreciate your answers, comments and advice!

---------------------------------------

(1) I can't speak to any specific experience with those cells, but pricing appears close to typical. I recently had 8X Xuba 280Ah cells quoted for $900 total delivered to my door.

(2) Lithium needs a low-temperature cut-off, i.e., they should stop charging below freezing, or the cells will be damaged. I do not see that your charger has this feature:


(3) 1500/12 = 125A minimum. More is better.

(4) Depends on which one you buy. Most have reasonable default settings.

(5) No recommendations.

(6) Per the linked manual above, you have many options for LiFePo4 (LFP). Good.

(7) Yes and no.

Yes - if the same 12V is powering the inverter and the inverter is powering the RV, then the inverter is powering the charger charging the batteries powering the inverter. If you turn off the inverter while on shore power, then that's fine. If you turn off the charger while using the inverter, that's fine.

No - Gel is usually a safe choice with LFP. Charge voltage of 14.2V or lower and a float voltage of 13.6V or lower.
 

DavidHouse

New Member
Joined
Sep 23, 2020
Messages
5
The price on the 200 Ah batteries that you mention is good if the batteries are in fact new. I ordered an identical looking set of batteries from Aliexpress (different reseller, BLS batteries, but same picture) a couple months ago and they shipped used batteries instead. That could be okay depending on your expectations but I returned the batteries (painful process, they are not eager to do returns) and got new 100 Ah cells from Overkill solar. Not as high a rated capacity, but I figure I can count on them not giving out at the wrong time and lasting the full expected lifetime. Here's a video of the used cells that I returned if you want to judge for yourself:
 

Gazoo

Dumb Dumb
Joined
May 12, 2020
Messages
2,794
Location
Texas
I would be careful ordering no brand cells. If they will supply the spec sheet so you know the manufacturer and other things, and they guarantee the cells are new then it should be ok. I have read the reviews and the sellers replies.
 

cmpct_cmpr

New Member
Joined
Sep 28, 2020
Messages
11
(1) I can't speak to any specific experience with those cells, but pricing appears close to typical. I recently had 8X Xuba 280Ah cells quoted for $900 total delivered to my door.

(2) Lithium needs a low-temperature cut-off, i.e., they should stop charging below freezing, or the cells will be damaged. I do not see that your charger has this feature:


(3) 1500/12 = 125A minimum. More is better.

(4) Depends on which one you buy. Most have reasonable default settings.

(5) No recommendations.

(6) Per the linked manual above, you have many options for LiFePo4 (LFP). Good.

(7) Yes and no.

Yes - if the same 12V is powering the inverter and the inverter is powering the RV, then the inverter is powering the charger charging the batteries powering the inverter. If you turn off the inverter while on shore power, then that's fine. If you turn off the charger while using the inverter, that's fine.

No - Gel is usually a safe choice with LFP. Charge voltage of 14.2V or lower and a float voltage of 13.6V or lower.

Hey @snoobler, thank you so much for your complete reply of my many questions!

Regarding the 1st part of (7), my inverter has an Integrated mains priority circuit; when connected to shore power, it will disconnect from the battery and provide shore power, when shore power is off switch back to draw from the battery. I haven't wrapped my mind around this yet, but as far as I understand it would prevent the scenario you describe, wouldn't it?

In this case, I'd have to disconnect the built-in 230V sockets from the shore power inlet, and connect them to the inverter's 230V outlet instead. Then connect the inverter's 230V inlet to the shore power inlet.
 

cmpct_cmpr

New Member
Joined
Sep 28, 2020
Messages
11
The price on the 200 Ah batteries that you mention is good if the batteries are in fact new. I ordered an identical looking set of batteries from Aliexpress (different reseller, BLS batteries, but same picture) a couple months ago and they shipped used batteries instead. That could be okay depending on your expectations but I returned the batteries (painful process, they are not eager to do returns) and got new 100 Ah cells from Overkill solar. Not as high a rated capacity, but I figure I can count on them not giving out at the wrong time and lasting the full expected lifetime. Here's a video of the used cells that I returned if you want to judge for yourself:

Thanks for that heads-up, @DavidHouse. Too bad they sent you damaged cells. I think I will look for a different seller.
 

cmpct_cmpr

New Member
Joined
Sep 28, 2020
Messages
11
I would be careful ordering no brand cells. If they will supply the spec sheet so you know the manufacturer and other things, and they guarantee the cells are new then it should be ok. I have read the reviews and the sellers replies.
what would be brands to look for?
 
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