LiFePO4 Battery Build

NOCO 8D battery box will fit 3 battery assemblies quite nicely. Now the question is will it fit between the engines??

Secondary question, haw to install the BMS and wiring. Need to come up with a nest...

If nothing else, if your looking for a good battery box, they seem very robust.


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Doooh. Just realized #4 cell in the wrong orientation. Have to redo that.

Edit...Repositioned, re-taped and added a 1/16" neoprene bottom to each battery.

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Fits between the engines and under the step.

Plenty of room for a 3rd battery if so desired, or BMS, and other assorted electronics. Lid has cutout for 4/0 wire.

Now to see if I can fashion a nest for the BMS and active balancers, and finish the internal wiring.

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Nice clean install! Do you not have a bilge pump there?
 
What’s the consensus on adding capacity over time?

Can you start with a small system and add more batteries two years down the road, or would you need to create a fresh set?
 
What’s the consensus on adding capacity over time?

Can you start with a small system and add more batteries two years down the road, or would you need to create a fresh set?

Best practice would be to get them all at once, all the same capacity, matched.

But lots of people add cells over time. You just won't have as much capacity the further from spec the cells are.
 
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Best practice would be to get the all at once, all the same capacity, matched.

But lots of people add cells over time. You just won't have as much capacity the further from spec the cells are.
The good thing about these batteries as long as they are properly charged and discharged they will remain a peak performance for years. Adding capacity as long as that capacity is the same profile should not be an issue for quite a few years. Lead acid batteries loose performance within a year or so and the reason that adding new capacity tends to be hard on the new batteries. The only thing I would say on the lithium is the new capacity must be on a separate BMS; but then it has to be....
 
Made a little progress today after accumulation various pieces and parts to wire it up, mount things and keep them insulated and secured.

BMS wires are 2/0 crimped with adhesive heat shrink and braid wrapped.
Other end of BMS connected to a 1/4”x1” copper bus bar. Inverter leads will connect up to this. That whole assembly will be attached to a couple pieces of ABS attached to the case.

The Positive leads are individually protected with a MRBF fuse on the battery terminal, positive leads also crimped, shrink wrapped and braided. Positive bus in in the lid assembly set off on isolators.

All the bus bars still need to be shrink wrapped to reduce open metal. Then I need to go back and clean up all the leads, tighten all the connection’s and secure the temp probes…generally straitened things up.


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Finally made a push to get this thing assembled an in the boat for the summer.

Cut and made the 2/0 internal leads. Used mesh braid and locked in place with shrink wrap.

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Cut and drilled the BMS mounting board and mounted the active balancer boards (not sure if the do anything but what the hell.) Everything sitting on 1/4 risers mostly to keep the electronics safely off the board. A little air flow underneath doesn't hurt.

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Batteries all wired up, temp probes mounted, and ready to button up.

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Finished battery pack with Bluetooth module mount on the side.

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First one in the box. Positive lead is a little long, I'll have to shorten that up.

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Added shrink wrap to the bus bars to reduce exposed metal/short potential
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Had a change of plans. I don’t like all this metal bus bar floating around in the box sight unseen. Just not clean enough for my liking. Additionally, while LiFePO4 batteries are “lighter”…2-3 of them is still massive and impossible to manhandle in the bilge.

I had a discount coupon for a SFK V3 battery box that’s made to fit my taller 304’s, so I thought I would try one…they have a good return policy, so low risk. I have to say, this thing is solid, goes together well, keeps everything in its place , keeps wires well organized and is more compact that what I'm able to do DIY.

These will fit in a standard battery tray, and are much more manageable. After seeing how everything goes together, I ordered a second box.

These will also allow me to move them much closer to the inverter, and other batteries, and make a cleaner more manageable install (at some point)!

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Finished up both batteries this weekend. Went back and torqued all the bus bars down and added blue loctite to all nuts/bolts. All wires loomed and zip tied in place. Temp sensors placed and secured.

Ready to install in the boat.

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What cost do you have in each battery?
Since I changed packaging about 3 times…a lot more than If I had purchased off the shelf, and prices has been dropping over the course of the build.

But starting today….

SFK Battery Kit $200
JBD 200A BMS $200
4x304 Ah Eve Cells @$135 = $540
4s Active balancer $25
Misc wire/terminals $50

So roughly $1000 each.

My issue is getting the current flow necessary to support a 2800W inverter @ 12V.

if I were starting from scratch, I’d go with a 24V version and off the shelf batteries that Will recommended….probably the SOK marine versions.

Oh well. Learned a lot and had a good time. Probably build 1 more to be able to get several hours out of the front AC…we shall see.
 
Since I changed packaging about 3 times…a lot more than If I had purchased off the shelf, and prices has been dropping over the course of the build.

But starting today….

SFK Battery Kit $200
JBD 200A BMS $200
4x304 Ah Eve Cells @$135 = $540
4s Active balancer $25
Misc wire/terminals $50

So roughly $1000 each.

My issue is getting the current flow necessary to support a 2800W inverter @ 12V.

if I were starting from scratch, I’d go with a 24V version and off the shelf batteries that Will recommended….probably the SOK marine versions.

Oh well. Learned a lot and had a good time. Probably build 1 more to be able to get several hours out of the front AC…we shall see.

Thanks for the insight. Good project and great learning opportunity nonetheless.
 

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