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New LifePo4 Battery Build Questions?

srssrs

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Nov 16, 2021
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Adding Solar and LifePo4 to Winnie View 2014J model. I am going to replace 2 - Group 27 LA batteries but want to keep them in the same location (under the steps). My area to work with is 7-3/4" wide by 22" long. I believe I can fit 2 - Lifepo4 batteries in place of those if I build with 4 - EVE230 cells. I would end up with a battery that has these dimensions: 6.85" w by 8.48" long by 8.05" high. I would like to find a battery box or enclosure that would accommodate these cells. I will end up with 2 batteries of 230ah each and would wire them in parallel to keep my output at 12v. (same as the stock LA batteries). This will give me aprox. 460ah of LifePo4 batteries in the same area that I originally had only 160ah of LA batteries. I will use 3 - 215w solar panels mounted flat on my roof to charge with.

Does anyone know of a battery box that will accommodate these cells (it cannot be over 11" long)? What BMS would you recommend for each battery? What solar charger would you recommend I look at?

I will also add a transfer switch, smart charger, and a dc-dc charger to protect my alternator.

Thank you,
Steve
 
Adding Solar and LifePo4 to Winnie View 2014J model. I am going to replace 2 - Group 27 LA batteries but want to keep them in the same location (under the steps). My area to work with is 7-3/4" wide by 22" long. I believe I can fit 2 - Lifepo4 batteries in place of those if I build with 4 - EVE230 cells. I would end up with a battery that has these dimensions: 6.85" w by 8.48" long by 8.05" high. I would like to find a battery box or enclosure that would accommodate these cells. I will end up with 2 batteries of 230ah each and would wire them in parallel to keep my output at 12v. (same as the stock LA batteries). This will give me aprox. 460ah of LifePo4 batteries in the same area that I originally had only 160ah of LA batteries. I will use 3 - 215w solar panels mounted flat on my roof to charge with.

When considering usable capacity, you're talking about replacing 80Ah of LA (50% capacity usable) with 368Ah (80% capacity usable) or a 4.6X increase in usable battery capacity.

Got nothing for a box.

BMS would depend on your anticipated loads. I'd get a clamp ammeter and measure battery current when operating things like slides or any high-drain items. If you plan to run an inverter, you divide the inverter power by 0.8 (inefficiencies) and divide by 12V - that's the amps you need to deliver.

215W * 2 / 12 = 35.8A - any 30-40A MPPT controller would work. Rare you'll get the full output of the panels flat on the roof, so 30A is probably okay, but if you never want to lose a drop, 40A. If you think you might add another panel in the future, it might make sense to go 50-60A.
 
I have a 2008J and fit 8x 206Ah cell (2P4S) and a Victron 100/30, Overkill BMS and breaker for an inverter in there.

The compartment is much larger than the opening. I press fit 2” foam on 4 sides and bottom for insulation. For a battery “box”, i made a carrier with just a bottom and ends, held together on top with a 2x2.

The key of course is getting it to fit in the opening AND being able to wire it up.
The bottom tray has edges that stick up maybe a half inch to cradle the grp 27’s. There is quite a but of room outside this bottom cradle. I pressed foam in bottom with slits to fit around the cradle so bottom was flat and would accept bigger cells.

Hopefully this makes sense. You should remove batteries to get a better idea about the compartment to make sure you know what tou are working with (a pain, i know).

CE6A207A-CB99-4AFA-B2F9-7AA9958EB987.jpeg
 
Mister Sandals,
Thank you for all that. It is very helpful since I pretty much have the same space limitations and battery box construction on my 2014 model. I like the way you approached using as much of the compartment and at the same time insulating and protecting the Lifepo4 cells. I also appreciate the photo.

I'm pretty confident I can squeeze a few more ah's of batteries into that space using EVE230 cells. Is there a specific reason you went with the 206's? This is my 4th V/N over the past 15 years so I do understand the need for as much reserve battery power as possible. As much as I have loved driving and traveling in these rigs, I found myself constantly monitoring my batteries as there was never enough power when boondocking (my first choice when camping). Lifepo4 and solar has recently changed all that.

Do you use one BMS for all 8 cells even though they are 2P4S? I am not familiar with the Overkill but will check it out. I have not ordered my cells just yet but contacted Amy from powerwholesale.net yesterday and they are 2 weeks out from having these. My total cost will be about $900 for 8 cells.

I have other questions for you but thinking perhaps we can communicate directly? Not sure others are interested in reading about specifics. Thank you.......Steve
 
Mister Sandals,
Thank you for all that. It is very helpful since I pretty much have the same space limitations and battery box construction on my 2014 model. I like the way you approached using as much of the compartment and at the same time insulating and protecting the Lifepo4 cells. I also appreciate the photo.

I'm pretty confident I can squeeze a few more ah's of batteries into that space using EVE230 cells. Is there a specific reason you went with the 206's? This is my 4th V/N over the past 15 years so I do understand the need for as much reserve battery power as possible. As much as I have loved driving and traveling in these rigs, I found myself constantly monitoring my batteries as there was never enough power when boondocking (my first choice when camping). Lifepo4 and solar has recently changed all that.

Do you use one BMS for all 8 cells even though they are 2P4S? I am not familiar with the Overkill but will check it out. I have not ordered my cells just yet but contacted Amy from powerwholesale.net yesterday and they are 2 weeks out from having these. My total cost will be about $900 for 8 cells.

While it saves you money with only a single BMS, the extra spend can save you headaches. If a 2P4S battery experiences a cell failure, you have to take the battery offline and attempt to determine which of the two cells has gone bad. You've pretty much ruined a day w/o power getting it sorted. If you opt for 2X 4S batteries, each with their own BMS, a single cell failure is obvious, and you still have the other battery to run things while you sort out the issue.
 
While it saves you money with only a single BMS, the extra spend can save you headaches. If a 2P4S battery experiences a cell failure, you have to take the battery offline and attempt to determine which of the two cells has gone bad. You've pretty much ruined a day w/o power getting it sorted. If you opt for 2X 4S batteries, each with their own BMS, a single cell failure is obvious, and you still have the other battery to run things while you sort out the issue.
Got it. I did check out the overkill bms and am assuming you used the 24v. model to monitor all 8 cells. I was considering using a bms on each battery even though an extra expense. Any reason I could not use a Daly bms? Is there a reason you prefer overkill?
 
Is there a specific reason you went with the 206's?
They were pretty much the biggest I could find at a reasonable price 2 years ago. And they fit in the opening.
Do you use one BMS for all 8 cells even though they are 2P4S?
Yes, that’s pretty much the only option for 2P4S.
I did spend a considerable amount of time matching the 2P pairs. I bought 13 cells to make a 4S battery for a greenhouse and a 2P4S for the RV. The best 8 are in the RV, matched strongest with weakest, second strongest with second weakest…

I think 412Ah is quite a bit of power. Over 4X what I had with stock lead acid batteries. And after just a couple years the lead acid batteries get weaker and weaker. I have 330W on the roof: between nacelles and in back of air conditioner (too close and sometimes shaded if not parked with this in mind). But I have never run low with this setup, even running a DVR, which is our biggest draw.

assuming you used the 24v. model to monitor all 8 cells
No, it’s a 4S battery so only an 4S BMS will work.
 
So again my plan is to build two 230ah 12v. batteries, each with 4 cells and wire each battery in parallel, as my original LA house batteries were wired. If I used the Overkill BMS for each battery, which model should I choose. Or, should I consider wiring my cells differently? They will all fit into the long compartment under the steps. Not certain if it is necessary to have my cells under some compression? I have read where some say that is not needed? I can build my own carrier or battery box if needed.
 
They were pretty much the biggest I could find at a reasonable price 2 years ago. And they fit in the opening.

Yes, that’s pretty much the only option for 2P4S.
I did spend a considerable amount of time matching the 2P pairs. I bought 13 cells to make a 4S battery for a greenhouse and a 2P4S for the RV. The best 8 are in the RV, matched strongest with weakest, second strongest with second weakest…

I think 412Ah is quite a bit of power. Over 4X what I had with stock lead acid batteries. And after just a couple years the lead acid batteries get weaker and weaker. I have 330W on the roof: between nacelles and in back of air conditioner (too close and sometimes shaded if not parked with this in mind). But I have never run low with this setup, even running a DVR, which is our biggest draw.


No, it’s a 4S battery so only an 4S BMS will work.
Can I also ask what smart charger you used to replace the stock charger? And, what automatic transfer switch you went with? My rig will occasionally use shore power, the diesel generator and solar. Also, any recommendations for an MPPT charge controller?
 
So again my plan is to build two 230ah 12v. batteries, each with 4 cells and wire each battery in parallel, as my original LA house batteries were wired. If I used the Overkill BMS for each battery, which model should I choose. Or, should I consider wiring my cells differently? They will all fit into the long compartment under the steps. Not certain if it is necessary to have my cells under some compression? I have read where some say that is not needed? I can build my own carrier or battery box if needed.

The BMS depends on how many amps you need to draw out of the batteries. If you need less than 240 amps, then the typical 120 amp 4s BMS will do fine. If you need more than that then look for the JBD 200 amp BMS.

Yes, the cells should be compressed. Don't skip this. Don't skip top balancing either.
 
Can I also ask what smart charger you used to replace the stock charger?
I replaced the stock Wafco charger long ago (before I got LiFePO4) with a Progressive Dynamics PD4645. It knows nothing of LiFePO4 and is not configurable so it charges to about 80% on shore power (rarely have shore power). Works just fine for that.
There isn’t a transfer switch. In the power compartment, the shore power cord plugs into a generator powered 30A receptacle (I keep it this was except when using shore power).

My SCC is a Victron 100/30. It’s burried in the shadow at the top of my pic in post #3. The solar cutoff switch is also pictured…I wondered if it would be in the way but it’s perfect there. I turn on solar a couple days here and there to keep batteries at storage levels between trips.

I like my 2P4S battery setup. I really like the idea of a single BMS. I am limited to 120A but that is not an issue, I have very little AC equipment…biggest is a DVR so a 600W inverter is plenty. If I really need the microwave, I fire up the generator but that is rare. (14 hours on generator in 12 years).
 
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