280AH 4S, Compressed with Heaters in a 27 Series Battery Box

JeepDaddy

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Feb 1, 2021
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253
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Kent, WA
A few pics of my 4S 280AH build with 150A JBD BMS with cell compression, Bluetooth, active balancer, and two 10W heaters all shoehorned into a marine 27 series battery box. The packing foam that the batteries came in makes great insulation and hold the battery in place.
 

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FilterGuy

What, me worry?
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Nov 26, 2019
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Los Gatos CA
A few pics of my 4S 280AH build with 150A JBD BMS with cell compression, Bluetooth, active balancer, and two 10W heaters all shoehorned into a marine 27 series battery box. The packing foam that the batteries came in makes great insulation and hold the battery in place.
Nice!!
How do you like the JBD 150A BMS?

I see you are using the B+ power Connections on the BMS. B+ battery connections on a FET based BMS is very unusual and in the ads on line, it looks like the B+ connection is optional to use. Do you know why it is there and what it does?
 

JeepDaddy

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Do you know why it is there and what it does?
B+ is to power the two heater circuits built into the board. The heaters are powered by the top two ports above the B+ marking in the pic. I don't think it's required for anything else.

I like the BMS so far. No problems.
 

FilterGuy

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Nov 26, 2019
Messages
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Location
Los Gatos CA
B+ is to power the two heater circuits built into the board. The heaters are powered by the top two ports above the B+ marking in the pic. I don't think it's required for anything else.
Interesting. I don't know of any other DIY BMSs with that capability. Nice. Do you have much info on what wattage it can run and what algorithm it uses for deciding when to heat? Is it only if there is charge current or will it drain the battery to heat?

I am starting to like this BMS..... I am going to have to try it in my next 24V, 3000W build.
 

JeepDaddy

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Feb 1, 2021
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Location
Kent, WA
The seller says each of the two ports can support 10 watts max. They turn on at the lower temperature charge cutoff and back off at the release value. I bench tested this to be true. I do like that built in feature. As shown, I put 2 10W silicone heating pads, one on each port, on an aluminum sheet under the cells. We'll see how it works in practice this winter. I think the v1.5 and newer boards have this, although today I just saw a pic of a v1.5 board without the heating circuits.
 

shadowsteve

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Feb 11, 2021
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245
I'm building two units the same as yours and with the 150A JBD. My boards have the heater plugs on the board but I didn't get any cables with the board. It looks like power and temp sensor on each connector.

Did your board come with the cables?

What is the small board by the BT module? Balancer?

Did you top balance your cells before hooking them up and cycling them? Mine are all the same cell voltage but it'll take forever to top balance them with my 10A supply.
 

curiouscarbon

Science Penguin
Joined
Jun 29, 2020
Messages
2,221
A few pics of my 4S 280AH build with 150A JBD BMS with cell compression, Bluetooth, active balancer, and two 10W heaters all shoehorned into a marine 27 series battery box. The packing foam that the batteries came in makes great insulation and hold the battery in place.
The wiring you have done looks wonderful.

I really like your small heater approach.

The aluminum casing has ~200 W/mK thermal conductivity and should diffuse the heat very nicely into the cell material.

LiFePO4's weakest spot to me is the low temperature charging limitation. After that energy density.

Great work, love to see it.
 

Fpoet

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Joined
Nov 9, 2020
Messages
70
A few pics of my 4S 280AH build with 150A JBD BMS with cell compression, Bluetooth, active balancer, and two 10W heaters all shoehorned into a marine 27 series battery box. The packing foam that the batteries came in makes great insulation and hold the battery in place.
Great set-up. I love the fact that the heating circuits is integrated into the BMS. My heating circuit is also made up of 10W heating pads (with an external thermostat), however the wiring and wire insulation on the pads are much more flimsy compared to yours. Would you mind sharing your source for the pads?
 

JeepDaddy

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Messages
253
Location
Kent, WA
I'm building two units the same as yours and with the 150A JBD. My boards have the heater plugs on the board but I didn't get any cables with the board. It looks like power and temp sensor on each connector.

Did your board come with the cables?

What is the small board by the BT module? Balancer?

Did you top balance your cells before hooking them up and cycling them? Mine are all the same cell voltage but it'll take forever to top balance them with my 10A supply.
My BMS came with the heater cables. They have an overtemp disconnect thermostat built into the cable assembly that you can see in the third picture.

Yes, Thats an active balancer by the BT module. I'm not sure I need it now that I have a few good cycles on my battery.

I would highly recommend top balancing your cells. Spend several days now top balancing and you will save yourself problems down the road. 10A will get you there, it will just take time. The voltages being the same at less than close to 100% SOC means pretty much nothing.
 

shadowsteve

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Joined
Feb 11, 2021
Messages
245
My BMS came with the heater cables. They have an overtemp disconnect thermostat built into the cable assembly that you can see in the third picture.

Yes, Thats an active balancer by the BT module. I'm not sure I need it now that I have a few good cycles on my battery.

I would highly recommend top balancing your cells. Spend several days now top balancing and you will save yourself problems down the road. 10A will get you there, it will just take time. The voltages being the same at less than close to 100% SOC means pretty much nothing.
Thanks. As per a comment Will made in a video I'm charging the pack as a 4S prior to top balancing as it was at such a low voltage (3.330v cells).

I'll have to see about getting the heater cables from somewhere or making a set
 

kite

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Jun 24, 2021
Messages
29
hey @JeepDaddy thanks for making this post. I was torn between building a plywood box, buying something bigger, or re-using a plastic battery box from one of the group 31 lead acids I'm replacing in my van. Your post gave me confidence I could make a 4s 280ah battery fit in the box (and space) I already have, and I'm really glad I did. I don't mean to hijack your thread here but figure I'll add details of my variant in case it helps someone down the line.

My primary requirements were:
  1. low relative motion, I'm driving an old sprinter down plenty of nasty roads and there's nothing smooth about it
  2. low stress on cell terminals with the inevitable relative motion that does occur
  3. some compression but not the high (in my opinion) 12 psi that others are aiming for
  4. distribute pressure across entire cell face to avoid pressure points where bare cells would make contact if pressed directly against each other
The build:
  • 1/2" plywood end plates, slightly thinned out at the bottom to fit inside the tapered box. I would have used thicker if space allowed
  • 1/8" foam from McMaster between each cell and end plate ("Flame-Retardant Oil-Resistant Blended Buna-N Foam").
  • compression with 1/4" bungee cord. I bought 50ft of this. I hung a few weights from single length of bungee and found that at 50% elongation the tension is ~ 5lbs. So, each wrap all the way around the assembly at 50% stretch = 10lbs force. 50' bungee at 50% elongation could get me 22 wraps = 225 lbs. 225lb/56 = ~4psi. I ended up doing 14 wraps and it feels super solid. Pressure ~ 2.5 psi (with just under 150lbs total force. I can pick it up and shake it around by the loops of line of line on each end plate and nothing moves at all.
  • after compressing I made 2AWG cell interconnects instead of bus bars. It was easier to do diagonal than U-shaped loops so I did that with a slight arc
  • the 120A JBD BMS doesn't span the entire length of the cells so I put a plate across the top, solidly mounted to one end plate and bungeed down to the other to account for expansion/contraction. I had to raise the lid by 3/4" by adding spacers inside the lid where it sits on the lip of the box
  • discharge on/off switch mounted to the lid. The BMS app is great but it's nice being able to switch the discharge off and know it's off right at the battery when making connections
  • battery main studs on the sides of the box
 

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shadowsteve

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Messages
245
Nice setup with the battery box usage. I built plywood boxes for my 280's as I put them in a long config to suit the long version of the JBD 150A BMS I have. Haven't yet decided how to bring power out of the pack. I can either have cables long enough to reach a bus bar or use binding posts. I don't want them on the outside of the box though as then they are exposed to the other stuff in the install location (RV basement)
 

kite

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Joined
Jun 24, 2021
Messages
29
I don't want them on the outside of the box though as then they are exposed to the other stuff in the install location (RV basement)
Yeah it's a little bit of a risk. I got these covers that almost completely cover the live portion of the post. They definitely protect from anything bumping against the top of the post which is the most likely scenario.
 

Smokin

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Joined
Sep 8, 2021
Messages
216
Truck innertubes cut into strips wrap cells and use for compression
 

DIDDLYV

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Joined
Mar 1, 2021
Messages
91
What is the plate you have the battery warming pads affixed to and is there anything between the plate and the bottom of the batteries? I may make a similar set up with batteries turned on side to fit in my current battery bin.
 

JeepDaddy

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Joined
Feb 1, 2021
Messages
253
Location
Kent, WA
What is the plate you have the battery warming pads affixed to and is there anything between the plate and the bottom of the batteries? I may make a similar set up with batteries turned on side to fit in my current battery bin.
It's a sheet of 0.040" aluminum in "Pepsi Blue". I got twice as much as I need for $4 on eBay. The heater pads are attached with RTV silicone gasket sealer to it and the battery cells sit right on top of it.
 

DIDDLYV

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Mar 1, 2021
Messages
91
Thanks, was wondering if you think there will be an issue with the thin plastic insulator on cells wearing thru and causing shorts in the battery. If the case is actually connected to the negative pole of the cells this is moot.
 

Mike Jordan

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Joined
Jun 15, 2020
Messages
414
hey @JeepDaddy thanks for making this post. I was torn between building a plywood box, buying something bigger, or re-using a plastic battery box from one of the group 31 lead acids I'm replacing in my van. Your post gave me confidence I could make a 4s 280ah battery fit in the box (and space) I already have, and I'm really glad I did. I don't mean to hijack your thread here but figure I'll add details of my variant in case it helps someone down the line.

My primary requirements were:
  1. low relative motion, I'm driving an old sprinter down plenty of nasty roads and there's nothing smooth about it
  2. low stress on cell terminals with the inevitable relative motion that does occur
  3. some compression but not the high (in my opinion) 12 psi that others are aiming for
  4. distribute pressure across entire cell face to avoid pressure points where bare cells would make contact if pressed directly against each other
The build:
  • 1/2" plywood end plates, slightly thinned out at the bottom to fit inside the tapered box. I would have used thicker if space allowed
  • 1/8" foam from McMaster between each cell and end plate ("Flame-Retardant Oil-Resistant Blended Buna-N Foam").
  • compression with 1/4" bungee cord. I bought 50ft of this. I hung a few weights from single length of bungee and found that at 50% elongation the tension is ~ 5lbs. So, each wrap all the way around the assembly at 50% stretch = 10lbs force. 50' bungee at 50% elongation could get me 22 wraps = 225 lbs. 225lb/56 = ~4psi. I ended up doing 14 wraps and it feels super solid. Pressure ~ 2.5 psi (with just under 150lbs total force. I can pick it up and shake it around by the loops of line of line on each end plate and nothing moves at all.
  • after compressing I made 2AWG cell interconnects instead of bus bars. It was easier to do diagonal than U-shaped loops so I did that with a slight arc
  • the 120A JBD BMS doesn't span the entire length of the cells so I put a plate across the top, solidly mounted to one end plate and bungeed down to the other to account for expansion/contraction. I had to raise the lid by 3/4" by adding spacers inside the lid where it sits on the lip of the box
  • discharge on/off switch mounted to the lid. The BMS app is great but it's nice being able to switch the discharge off and know it's off right at the battery when making connections
  • battery main studs on the sides of the box
I just did a search for 280ah batt box builds. I have looked at a few. I like this best. I may steel every inch of that
 
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