Alternators - leave them alone and forget about them

[Jeff F]

Yes

And it's own MRBF

Mrbf? Failure expectation?

 

[Simi 60]

Mrbf? Failure expectation?

Nope

I carry lifejackets, EPIRB and flares as well
Doesn't mean I expect to sink.

 

[rslifkin]

Mrbf? Failure expectation?

MRBF is a type of fuse.

 

[Jeff F]

Gotcha. I don't pay that much attention to fuses. I'm sure I will at some point.

Getting back to my case, reject batteries could make great Xmas gifts. Tons of practical RW applications. They're just the runts of the litter, usually.

 

[Jeff F]

I'm going to change MBMS to BBMS. What I'm really describing is a bank BMS that allows you to easily and effectively make use of a variety of drop-in solutions, each having their own BMS.

It's also easy to imagine an LA connection as well. Then if your current system does what you want leave it alone, add a BBMS and have some good clean fun.

Not hard to manage with smarts.

 

[twistedtree]

We paid less than $2 usd/ 12v ah

Matched and batched EVE 280ah 3.5v cells X 24 (8 makes a 24v @ 280ah batt)
A 200amp 24v JBD BMS and a 200 amp MRBF for each

Made 3 x totally independent batteries and, the boat will run on one - for the first few days we did just that as proof of concept
$3650 USD and that included delivery to the door China to Oz

Some assembly required

Can you explain how the BMS hooks up? I can't make heads or tails of the description on Alibaba.

 

[twistedtree]

Rather than a BBMS + drop ins, why not raw cells + BMS as Simi has done? I did the same at home and it's certainly the cheapest route. Plus you get full functionality.

 

[Jeff F]

Right. I think most people do charge to full capacity regularly, so hopefully internal balancing works as designed.

In a parallel bank having an individual battery cut out in boundary cases - very low or very high SoC - may not be a problem as much as a cue that the battery is out of balance. Maybe you try to fix by cycling the battery a few times on the bench.

With a BBMS that's dead easy. Switch the battery offline and dial the BBMS down a bit. No rush to address.

In my imaginary world

 

[Jeff F]

I have to think that BBMS exists somewhere in the RW.

 

[Jeff F]

Rather than a BBMS + drop ins, why not raw cells + BMS as Simi has done? I did the same at home and it's certainly the cheapest route. Plus you get full functionality.

Mmm. Depends on scale. I have 3 300 ah drop ins, each with 200a BMS.

So if 200a is enough in/out, no adv/disadvantage. Why build your own?

Edit to add: BBMS makes it easy for dummies, as my dear old dad would say.

Let's identify a RW win with a BBMS for me. Instead of periodically checking health of drop ins periodically (hello, are you awake?) I bolt on a BBMS, run the pack at 300a and ignore.

I can't wait.

 

[Simi 60]

Can you explain how the BMS hooks up? I can't make heads or tails of the description on Alibaba.

Yeah, some of the instructions didn't translate well to Chinglish.

This pic from our supplier in China worked well
No words needed
You can see cell 6 gets a lot of wires
All done with 6mm heat shrink eye terminals

 

[Simi 60]

Our actual BMS was this model, same wiring

 

[Barking Sands]

Rather than a BBMS + drop ins, why not raw cells + BMS as Simi has done? I did the same at home and it's certainly the cheapest route. Plus you get full functionality.

I guess I should share this to help with my perspective. The number 1 reason I am resistant to building my own battery + BMS is actually due to appearance. And no I dont mean appearance as in I think its ugly, but appearance susceptible to bias from a potential surveyor or Insurance company or possible future buyer. There is an entire lagging subgroup right now of lithium haters and old school curmudgeons that spit venom at anything lithium as well as other groups that are very fearful of anything with the word lithium. We have all seen this in action and its very persistent.

I think the old adage "If you are explaining you are losing" when dealing with Insurance, Surveyors and potential buyers could be problematic.

We really dont know what insurers will do over the coming years. I personally think they will be more apt to look for a manufactured battery assembly from a reputable manufacturer with all the certs. And then the surveyor sees something like the Epoch batteries and will just move on by.

But if a surveyor has to sign off on a homemade battery with balance wires and comm cables everywhere and then you tell him the BMS is this and that and I got the cells from China and then you just hook it all up and then program that.....

So this is my perspective of the middle ground. I dont want to pay Victron prices and I do want to install it myself. The appearance of a "typical" battery system might be worthwhile in key situations.

 

[Jeff F]

I guess I should share this to help with my perspective. The number 1 reason I am resistant to building my own battery + BMS is actually due to appearance. And no I dont mean appearance as in I think its ugly, but appearance susceptible to bias from a potential surveyor or Insurance company or possible future buyer.

Bingo. I went down that path, and don't do superbly neat work.

For me it was a non starter. Followed Simi's progression and made notes

Edit to add: there was a thread here not long ago that also directed my thinking. I swapped from AGM to lithium. Swapping back is trivial.

 

[Simi 60]

I. There is an entire lagging subgroup right now of lithium haters and old school curmudgeons that spit venom at anything lithium as well as other groups that are very fearful of anything with the word lithium. We have all seen this in action and its very persistent.

I think the old adage "If you are explaining you are losing" when dealing with Insurance, Surveyors and potential buyers could be problematic.
.

Some people have no idea.
They need to do some research and try and keep up with the world or stop doing what they are doing

But if a surveyor has to sign off on a homemade battery

8 LFP cells joined by busbars and a BMS to monitor is as much a homemade battery as the 8 AGM joined with cables and lugs with a Victron battery monitor attached that we used to have

 

[Barking Sands]

Some people have no idea.
They need to do some research and try and keep up with the world or stop doing what they are doing





8 LFP cells joined by busbars and a BMS to monitor is as much a homemade battery as the 8 AGM joined with cables and lugs with a Victron battery monitor attached that we used to have

SIMI..you are preaching to the choir. But we still have to deal with these people in the mean time.

 

[Jeff F]

SIMI..you are preaching to the choir. But we still have to deal with these people in the mean time.

Right. And you're not in the USA, where if it's imperfect it's garbage.

Simi, you did the right thing for your wants, needs, skills and budget. And it's as fast moving field. I really benefited from following along.

 

[Jeff F]

Catch up, man. Go back and start from the beginning.

Sorry I was snarky. I felt like you were butting in. You weren't of course. I was just on a bit of a roll [emoji28]

 

[Jeff F]

Maybe you try to fix by cycling the battery a few times on the bench.

Further to that, bench testing and cycling 50ah is far easier and faster than bench testing 200ah, as I'm sure you recognize.

 

[Jeff F]

Look to the future. It could well be 'marine' drop ins selling at twice the price of the same battery going in a lawnmower. I want no part of it.

OTOH a $500 marine device that facilitates generic LFP drop ins would get a lot of attention, and not just from me.

 

[Jeff F]

I have to think that BBMS exists somewhere in the RW.

My thinking is not entirely original. Now that I think about it, my 2001 Prius and all following had 1.2v Nmh cells bundled into 7.2v modules. The BMS was attached to 14.4v pairs. This on a 230v battery.

Interesting analogy. When a pair started drifting, the BMS would initiate a full battery cycle. Remember that the target SoC for the battery was 60-80%.

When that didn't work driver alerts started appearing.

When things escalated further the battery started shutting down.

The killer was heat in the middle of the battery.

 

[twistedtree]

Yeah, some of the instructions didn't translate well to Chinglish.

This pic from our supplier in China worked well
No words needed
You can see cell 6 gets a lot of wires
All done with 6mm heat shrink eye terminals

So it monitors voltage at each cell, up to 8 of them?


Any cell temp monitoring?


What's the thing in the upper left with big pos and neg cables? I think those are the loads?


Is the battery disconnect a solid state switch inside the device? On yours, which I think is a different model, I see a contactor.


Does it do balancing, and if so, when?


Thanks.

 

[twistedtree]

I guess I should share this to help with my perspective. The number 1 reason I am resistant to building my own battery + BMS is actually due to appearance. And no I dont mean appearance as in I think its ugly, but appearance susceptible to bias from a potential surveyor or Insurance company or possible future buyer. There is an entire lagging subgroup right now of lithium haters and old school curmudgeons that spit venom at anything lithium as well as other groups that are very fearful of anything with the word lithium. We have all seen this in action and its very persistent.

I think the old adage "If you are explaining you are losing" when dealing with Insurance, Surveyors and potential buyers could be problematic.

We really dont know what insurers will do over the coming years. I personally think they will be more apt to look for a manufactured battery assembly from a reputable manufacturer with all the certs. And then the surveyor sees something like the Epoch batteries and will just move on by.

But if a surveyor has to sign off on a homemade battery with balance wires and comm cables everywhere and then you tell him the BMS is this and that and I got the cells from China and then you just hook it all up and then program that.....

So this is my perspective of the middle ground. I dont want to pay Victron prices and I do want to install it myself. The appearance of a "typical" battery system might be worthwhile in key situations.

I couldn't agree more, and this is a big part of why I paid more for an engineered and manufactured battery system for the boat. For some questions the answer just needs to be a simple "Yes", not an explanation.

 

[Jeff F]

I couldn't agree more, and this is a big part of why I paid more for an engineered and manufactured battery system for the boat. For some questions the answer just needs to be a simple "Yes", not an explanation.

Moneybags

 

[Simi 60]

So it monitors voltage at each cell, up to 8 of them?

That model does up to 24 cells
The diagram shows what to do with the spare wires for 8 cell monitoring (group on cell 6)

Any cell temp monitoring?

Mid point

What's the thing in the upper left with big pos and neg cables? I think those are the loads?

Power distribution posts are illustrated.

Is the battery disconnect a solid state switch inside the device? On yours, which I think is a different model, I see a contactor

.

Ours has a contacor
On various forums there is claimed superiority of the more robust contactors over mosfets

Does it do balancing, and if so, when?

Balancing is observed when the battery is nearing full
Some cells get very slightly out of balance in the last minutes of charge
When I say slightly like 0.05v difference

As soon as charging has stopped and load takes over they show as balanced

 

[Simi 60]

I couldn't agree more, and this is a big part of why I paid more for an engineered and manufactured battery system for the boat. For some questions the answer just needs to be a simple "Yes", not an explanation.

If the surveyor doesn't understand lifepo4 batteries I would get rid of him and find one who does.

What else doesn't he understand?
What else is he missing?


If it makes you or him feel better they do make boxes in almost any shape you like to "hide" everything away out of sight out of mind just like the "engineered and manufactured battery " guys do.
I could even slap a sticker on it (-;

Me, I prefer to see what's going on.

.

https://m.alibaba.com/showroom/24v-battery-box.html