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Open Roads Forum  >  Do It Yourself Modifications and Upgrades (DIY)

 > How to build a LiFePo4 battery bank.

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StirCrazy

Kamloops, BC, Canada

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Posted: 09/27/21 09:14am Link  |  Quote  |  Print  |  Notify Moderator

FWC wrote:

otrfun wrote:

Overkill BMS's seem to have a very good rep; however, to my knowledge they don't make BMS's larger than 120a. For those who have 2000-3000w inverters with 200-300a current requirements what options do they have? Daly makes a few 150-250a models, but they have a somewhat sketchy rep. I suppose one could parallel multiple Overkill 100-120a BMS's and LifePo4 battery packs.


Running several in parallel is not a bad idea, it would be the same as running several drop in batteries in parallel. It spreads the load (and heat) across multiple devices, and provides redundancy as well. On the down side, you would need to look at several screens on the app to see what each pack is doing, but that is not a huge deal. If you are handy you could also merge the data from each BMS into one stream as the protocol is open source.

To give credit where credit is due - these are not Overkill Solar's BMS, they are just retailing/rebranding LLT powers BMS.


yup and if you go to there site you can get a 200amp version.

https://www.lithiumbatterypcb.com/produc........rge-current-for-12v-converter-power-ups/

Steve


2014 F350 6.7 Platinum
2016 Cougar 330RBK

StirCrazy

Kamloops, BC, Canada

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Posted: 09/27/21 09:19am Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

I put the 2x Overkill BMS and some fuses on a small shelf in the box. This is actually two separate batteries. Each has 2 cells in parallel and 4 in series so 8 cells per battery.

I expect to get this into my front compartment next weekend.

[image]


I like that setup. only questions I have is the use of the rachet strap and the potential for the hooks to damage the side of the battery cell. and I cant see any isolater between the cells. if the rachet strap is temporary how do you plan on compressing the cells to get better life out of them or are you, not worring about it as the charge rater will be lower than .25C and no risk of any heat?

Steve

time2roll

Southern California

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Posted: 09/27/21 10:11am Link  |  Quote  |  Print  |  Notify Moderator

I plan on minimal compression with two zip-ties around the box. The straps are temporary to hold the cells in place to fit the bus bars. If using ratchet straps I would re-thread them to eliminate the hooks.

I decided to skip the separators. They are wrapped nicely in the standard blue vinyl. Easy to overthink everything. Have not really read any issues with skipping the separators even though some insist something is needed. Not intended to be a bulletproof off-pavement design.

The box wall next to the fuses is floating (movable). There will also be heat pads, one per cell, on the outside controlled with a thermostat. They are 15w silicone pads. I will run two in series for maybe 4 watts each, 64 watts for the entire block.

The lid will come later. The sides will most likely stay open. More pictures in a week assuming I make progress.

To be installed into this space:

[image]

Member Pianotuna will be pleased to see my battery wiring will finally get balanced [emoticon]


2001 F150 SuperCrew
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pianotuna

Regina, SK, Canada

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Posted: 09/27/21 07:21pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll,

Hurrah!


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, soon to have SiO2 batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

StirCrazy

Kamloops, BC, Canada

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Posted: 09/28/21 07:57am Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

I plan on minimal compression with two zip-ties around the box. The straps are temporary to hold the cells in place to fit the bus bars. If using ratchet straps I would re-thread them to eliminate the hooks.


ok perfect, I dont think with that size of a bank your going to get anywhere near the charging rate that would require more compression anyways haha

time2roll wrote:

I decided to skip the separators. They are wrapped nicely in the standard blue vinyl. Easy to overthink everything. Have not really read any issues with skipping the separators even though some insist something is needed. Not intended to be a bulletproof off-pavement design.


ya the only reason I ask, is a lot of people have been putting something thin in that will prevent that vinal from getting scratched or worn off exposing the metal under it and a possible short, but I don't know how tough that vinal coating is and if it is nessasary

time2roll wrote:

The box wall next to the fuses is floating (movable). There will also be heat pads, one per cell, on the outside controlled with a thermostat. They are 15w silicone pads. I will run two in series for maybe 4 watts each, 64 watts for the entire block.

Member Pianotuna will be pleased to see my battery wiring will finally get balanced [emoticon]


that looks almost exactly like mine is set up haha. so I imaging you are self powering the pads from the battery bank? I was thinking of doing some sort of heating pads but make them so I could power them directly from the solar controler (load termanals I believe, have to read up and see how that works) so as I am driving the batteries will be kept warm. I am also going to move them into the empty space under the stairs of the 5th. right now the cold air returns for the furnace are in the steps so the warmed air will always flow through there and there is room for 4 battery packs under there easy. do you have a link to the heating pads your using?

Steve

time2roll

Southern California

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Posted: 09/28/21 07:11pm Link  |  Quote  |  Print  |  Notify Moderator

Heat pads: 50 x 100 mm fit nicely on the 70 x 200 mm cell edge.
I am gluing them on with Permatex high temp red silicone gasket maker adhesive.

https://www.aliexpress.com/item/1005001620200397.html

[image]

* This post was edited 09/28/21 08:04pm by time2roll *

time2roll

Southern California

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Posted: 10/02/21 06:40pm Link  |  Quote  |  Print  |  Notify Moderator

Installed and working....

[image]

pianotuna

Regina, SK, Canada

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Posted: 10/02/21 08:13pm Link  |  Quote  |  Print  |  Notify Moderator

Time2roll,

I guess that is totally the end of dragging around a generator for you! I hope it works wonderfully well.

Itinerant1

Itinerant

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Posted: 10/02/21 08:33pm Link  |  Quote  |  Print  |  Notify Moderator

Yes, very nice and welcome to the world of lfp. [emoticon]


12v 500ah (5,120Wh usable), 20 cells_ 4s5p (GBS LFMP battery system). 8 CTI 160 watt panels (1,280 watts)2s4p,Panels mounted flat. Magnum PT100 SCC, Magnum 3012 hybrid inverter, ME-ARC 50. Installed 4/2016 been on 24/7/365, daily 35-45% DOD 1,800+ cycles.

S Davis

Western WA

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Posted: 10/04/21 09:46pm Link  |  Quote  |  Print  |  Notify Moderator

My 12 EVE 280ah cells showed up today, building three 12v 280ah packs. I am going to run two in the truck with a spare on the shelf.


EVE 280ah

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