Free 7 Day Trial RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Free 7 Day Trial ×


Reply
 
Thread Tools Display Modes
 
Old 12-01-2021, 02:27 AM   #1
Mini-Skoolie
 
Join Date: Mar 2021
Location: Utah
Posts: 15
Chassis: 2006 Thomas Freightliner C2
Engine: Mercedes MBE 906
Pulled the trigger on some EVE 304 AH cells

Hi, so for the last several months of our buildout, I had been planning on getting 8 Duracell 6v GC2 batteries. I kept checking Sam's Clubs website and availability was concerning me. DIY LiFePO4 batteries are also comparatively reasonably priced. Sooo I bought 8 304 AH EVE cells (approx 7300 WH). The sales rep told me that they were already shipping to a warehouse in Texas so they told me to expect them within the next few weeks. We will see if that is accurate. Regardless, I need to buy the rest of the components to put together these batteries.

I want to test these cells as soon as I get them in a controlled setting (not in my bus). What is the best way to test their capacity and things? I want to be able to do so within 15 days of receiving them in case something isn't quite to spec so that I can get a refund.

I will be using a 24v system. I felt that doing an 8S configuration would be the best. What do you experienced folk say? Is 8S best? Or would a 4S2P system be better?

The two BMS brands I've been seeing are Daly and JBD. I know I can order Daly from a distributor here in the US. I imagine an 8S 200A BMS would be the way to go? Where do you buy JBD BMS if that is better?

The cells will come with 8 bus bars to connect the cells together. Should I use those or are there better options for a skoolie?

I've seen Will Prowse use a yellow clear tape to bind all the cells together and compress them somewhat. Is that the way to go for putting the packs together?

If you're curious about the rest of my system. I will have 1360 watts of solar on the roof. An LV2424 Hybrid Inverter charger MPPT charge controller combo. None of this is installed, but I have the solar panels and the inverter already.

I would appreciate any feedback from you experienced battery builders out there. Hopeful that all 8 cells will arrive in good condition. I spoke to one other skoolie that ordered 16 of the same cells from the same distributor and had great luck so I am hopeful.

Thanks!

Ross&Hailey is offline   Reply With Quote
Old 12-01-2021, 11:25 AM   #2
Bus Crazy
 
joeblack5's Avatar
 
Join Date: Dec 2015
Location: pa
Posts: 2,245
Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford 1998 e350 4x4 7.3 2 mercedes 2004
Engine: 7.3 powerstroke & MBE906
Best you go to a more specialized diysolar forum and read what all can go wrong and how to avoid that. A mobile application is a lot more challenging with vibration and dirt abrasion.. then extra thought to stay ahead of Murphy if your battery is involved in a fire.

Good luck,
Johan
joeblack5 is offline   Reply With Quote
Old 12-01-2021, 01:16 PM   #3
Bus Nut
 
Rwnielsen's Avatar
 
Join Date: Jun 2020
Location: Long Beach, CA
Posts: 606
Year: 1998
Coachwork: Blue Bird
Chassis: TC1000, 40' MPV
Engine: 5.9 Cummins/B300 trans
Rated Cap: U/K
What you're doing is almost exactly what I'm putting together, 8S, 24 volt x 2. I ordered 16, 200Ah cells for 400Ah @ 24 volt. I've been looking at the Daly 100a, 8S as well. Amazon carries them and I'll need two. They also have step down (24-12) transformers of various wattages for heaters and refers and such.. I'm not familiar with JBD but I'll take a look at them. With regards to series/parallel, I read (here, I think) that you series for voltage and parallel for amperage...somebody more knowledgeable will be around shortly. My next spendy item will probably be some form of charger until I get solar panels. I'm making my bus almost entirely DC and have been using misc generators while I work on it.
Rwnielsen is offline   Reply With Quote
Old 12-01-2021, 04:36 PM   #4
Bus Nut
 
Join Date: Apr 2020
Location: Northern California (Sacramento)
Posts: 634
Year: 1999
Coachwork: El Dorado Fiberglass
Chassis: Ford E450
Engine: V10 Gas
I did a 280 Ah DIY using Eve cells and a Daly 250A BMS.

Your biggest challenge will be to charge them up to capacity-that's a lot of juice.

Then you need to discharge them and track the amp hours you get out of them. That's how you know the cells are good, that they actually deliver the full amp hours specified.

You'll need the BMS to ensure no single cell drops below 2.5 for that discharge test. I also recommend you buy the Victron Smartshunt to track amps in and out of the system for the test and for general use.

Agreed you should watch Will Prowse for the build. Some other random things (today is busy, apologies, not a lot of time to reply but want to help get you started).

-get a 10 amp controlled power supply so you can systematically top off each cell to 3.65 precisely. If you bulk charge and don't allow for soak, the cells will not be at capacity and that will throw off both your top end balancing and your capacity test;
-Build the battery without tape; make a frame and provide a little compression instead so you can reconfigure and swap out cells over time without major surgery. I put a thin rubber mat between the cells to prevent rubbing/wear;
-get an active balancer so you can confirm all cells are precisely at 3.65 for the capacity test. See the Off Grid Garage videos to pick one out;
-do your discharge test at a low rate. For my battery I discharged at about 20 amps per hour or less. Same rational, discharge rate may distort your results if it is too high;
-build your battery in groupings so that you can remove a bank without taking down the whole system.

I wish I could recommend Daly. They are fantastic at returns, which is a good thing as you'll see lots of online comments about the device not working right. I was good with my device for a few weeks, then one day it freaked out and said everything was overdischarged. It wasn't (simple multimeter test), and I bought another BMS, but before I swapped them out I plugged the Daly back in and it's worked fine ever since.

I have 480 watts of solar and it produces about 36 amp hours of charge per California day in November. I am parked where the house blocks the bus until after lunch, and I've throttled the charge controller back to 80%, and only have the fridge on the inverter, so maybe it produces more? Point is, with 1500 or so watts of solar you may never bring those batteries up to full charge (or keep them there if your usage is high).

Love the idea of deep storage though.
Rucker is offline   Reply With Quote
Old 12-01-2021, 05:00 PM   #5
Mini-Skoolie
 
Join Date: Mar 2021
Location: Utah
Posts: 15
Chassis: 2006 Thomas Freightliner C2
Engine: Mercedes MBE 906
Quote:
Originally Posted by Rucker View Post
I did a 280 Ah DIY using Eve cells and a Daly 250A BMS.

Your biggest challenge will be to charge them up to capacity-that's a lot of juice.

Then you need to discharge them and track the amp hours you get out of them. That's how you know the cells are good, that they actually deliver the full amp hours specified.

You'll need the BMS to ensure no single cell drops below 2.5 for that discharge test. I also recommend you buy the Victron Smartshunt to track amps in and out of the system for the test and for general use.

Agreed you should watch Will Prowse for the build. Some other random things (today is busy, apologies, not a lot of time to reply but want to help get you started).

-get a 10 amp controlled power supply so you can systematically top off each cell to 3.65 precisely. If you bulk charge and don't allow for soak, the cells will not be at capacity and that will throw off both your top end balancing and your capacity test;
-Build the battery without tape; make a frame and provide a little compression instead so you can reconfigure and swap out cells over time without major surgery. I put a thin rubber mat between the cells to prevent rubbing/wear;
-get an active balancer so you can confirm all cells are precisely at 3.65 for the capacity test. See the Off Grid Garage videos to pick one out;
-do your discharge test at a low rate. For my battery I discharged at about 20 amps per hour or less. Same rational, discharge rate may distort your results if it is too high;
-build your battery in groupings so that you can remove a bank without taking down the whole system.

I wish I could recommend Daly. They are fantastic at returns, which is a good thing as you'll see lots of online comments about the device not working right. I was good with my device for a few weeks, then one day it freaked out and said everything was overdischarged. It wasn't (simple multimeter test), and I bought another BMS, but before I swapped them out I plugged the Daly back in and it's worked fine ever since.

I have 480 watts of solar and it produces about 36 amp hours of charge per California day in November. I am parked where the house blocks the bus until after lunch, and I've throttled the charge controller back to 80%, and only have the fridge on the inverter, so maybe it produces more? Point is, with 1500 or so watts of solar you may never bring those batteries up to full charge (or keep them there if your usage is high).

Love the idea of deep storage though.


Thanks for the help! I'm surprised by your solar bringing in so little... That is only 430 WH if you're on a 12v system... Which is only about 1 hour of good sun with 480 watts... I know the sun isn't great during the winter months but that's still some shocking data. What other BMS did you end up buying?
Ross&Hailey is offline   Reply With Quote
Old 12-03-2021, 11:48 PM   #6
Bus Nut
 
dzl_'s Avatar
 
Join Date: Jul 2019
Location: California, Bay Area
Posts: 888
Quote:
Originally Posted by Ross&Hailey View Post
Hi, so for the last several months of our buildout, I had been planning on getting 8 Duracell 6v GC2 batteries. I kept checking Sam's Clubs website and availability was concerning me. DIY LiFePO4 batteries are also comparatively reasonably priced. Sooo I bought 8 304 AH EVE cells (approx 7300 WH). The sales rep told me that they were already shipping to a warehouse in Texas so they told me to expect them within the next few weeks. We will see if that is accurate. Regardless, I need to buy the rest of the components to put together these batteries.

I want to test these cells as soon as I get them in a controlled setting (not in my bus). What is the best way to test their capacity and things? I want to be able to do so within 15 days of receiving them in case something isn't quite to spec so that I can get a refund.

I will be using a 24v system. I felt that doing an 8S configuration would be the best. What do you experienced folk say? Is 8S best? Or would a 4S2P system be better?

The two BMS brands I've been seeing are Daly and JBD. I know I can order Daly from a distributor here in the US. I imagine an 8S 200A BMS would be the way to go? Where do you buy JBD BMS if that is better?

The cells will come with 8 bus bars to connect the cells together. Should I use those or are there better options for a skoolie?

I've seen Will Prowse use a yellow clear tape to bind all the cells together and compress them somewhat. Is that the way to go for putting the packs together?

If you're curious about the rest of my system. I will have 1360 watts of solar on the roof. An LV2424 Hybrid Inverter charger MPPT charge controller combo. None of this is installed, but I have the solar panels and the inverter already.

I would appreciate any feedback from you experienced battery builders out there. Hopeful that all 8 cells will arrive in good condition. I spoke to one other skoolie that ordered 16 of the same cells from the same distributor and had great luck so I am hopeful.

Thanks!

So when you receive your cells, they will be at a partial state of charge (SOC), probably about ~30% SOC +/-. The will also not be balanced. So before you will be able to do a true capacity test you'll want to balance the cells.


Top Balancing (basic description):

This involves connecting all the cells in parallel, connect to a proper power supply and charge them until ~3.6 Volts AND current drops away to near zero, at this point your cells will be balanced. Because there will be no BMS protection in this process, its important that you understand what you are doing before you do it (read up on it), and you are present and attentive during the last portion. Here are two links (general explanation and guidelines, read both).



This is what top, bottom and unbalanced cells look like in visual terms:



Capacity testing:

At this point your cells are at 100% state of charge and top balanced. Once your cells are top balanced, you can rearrange them into a series configuration and wire up the BMS. You'll need a way to accurately track amp-hours consumed (not a voltage based battery monitor). Some BMS's can do this, as can many battery monitors like the Victron BMV, or a shunt or hall effect sensor. Probably you will have purchased something like this already for your system (since you'll want to know state of charge). Alternatively, you can use a dedicated capacity test like shown in this video, but those small testers will take a long time for a full pack. You'll want to make sure you set your BMS to disconnect the battery when the first cell hits the low voltage cutoff. That is 2.5V for most lifepo4 cells, you could use a little higher value of 2.6-2.8 if you want, it'll skew capacity a little bit, but not much since you are in the lower knee.


Alternatively you could use one of thos little capacity testers in the video to test each cell individually, in which case you could do that first, before top balancing. As you can see there is more than one way to do this (and a lot of wrong ways ) to some extent it will come down to what components you have on hand/are convenient to you.


As to taping your batteries, I wouldn't personally do that, there are better ways to secure batteries, Will's old tape method was one of the most commonly criticized things in this videos. Remember he is demo'ing usually free cells on a bench, and trying to keep things as simple as possible. As to how to properly secure your cells, you can get as nerdy/professional or as basic as suits your personality. If you ask your manufacturer (EVE) they will state that cells should be compressed at a constant 12PSI / 300KGF for maximum longevity. They have fancy ways of doing this. A DIY way is to use two pieces of plywood, threaded rods, and springs calculated to apply the proper force. Its a little technical, lots of people opt not to go that far but its growing in popularity. In the spec sheet you should have for your cells, they will list one cycle life specification for compression, and one for no compression. Both are over 2500 cycles if I recall correctly, but compression supposedly adds at least 1000 cycles. DIYsolarforum, is where you would want to go for more info on securing/compressing cells.



As to BMS, between the two, I would choose the JBD BMS, you can buy from a US based seller called "overkill solar," they have a website, and also sell on amazon. This is my top reccomendation for a BMS for beginners/less technically inclined folks. It has a bluetooth app, its fairly simple, it has good documentation (written by overkill solar), and the seller I mentioned offers good beginner friendly support if you need it. The only reason you might choose Daly over JBD/Overkill, is that the 8S JBD BMS is limited to 100A, if that is not enough (100A @ 25.6V = 2560W) you will need to look elsewhere. Daly is not a bad BMS either, and is available in higher current ratings, you definitely want to oversize it though (add 20% to 50% to the size you think you need). Both daly and JBD are cheap chinese commodity BMS's, but they are two of the brands with decent track records. JBD wins out when it comes to documentation/finding community support/help.
dzl_ is offline   Reply With Quote
Old 12-04-2021, 02:44 AM   #7
Bus Nut
 
dzl_'s Avatar
 
Join Date: Jul 2019
Location: California, Bay Area
Posts: 888
Here is the datasheet for the EVE 304Ah cells if its something you need/don't have. Give it a look, and let me know if you need help interpreting anything, cell datasheets are a fundamental resource to knowing your cells.
dzl_ is offline   Reply With Quote
Reply

Tags
battery, diy, electrical, lifepo4, questions

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 12:47 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2022, vBulletin Solutions, Inc.