Re: [electricboats] Parallel LiFePO4 Packs

Good Article.

I would use one of these two approaches:  either double each cell and build a single, double-capacity battery, with one BMS, etc.

Or, build two completely separate batteries, each with their own BMS, meters, etc.
And only run off of one battery at a time, never parallel them.

Upsides of the latter are the redundancy/failover you're interested it.
Downsides are that you're pulling at a higher C Rate, and most likely will use more Depth Of Discharge.
And of course the extra BMS/etc. overhead.

I've seen battery combiners for Ebike batteries that are basically a pair of diodes.
Eliminates any current flow between batteries while still allowing flow to the load from either battery.
Current levels for our use case are much higher than for Ebikes, so the diodes would need to be big, and probably expensive.
And they could get hot due to voltage drop, thus wasting energy.  And are another potential point of failure.

https://www.electromotivemods.com/shop/p/s1fmuuaawo86hdw5gduhknspnoks37

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Re: [electricboats] Parallel LiFePO4 Packs

I found this great article by Orion BMS that discusses parallel strings. Reading this really makes me lean toward parallel cells as you wise gents previously suggested.

Thanks again for all the valuable input.

Chris 

parallel_strings PDF Document · 408 KB

Sent from myPhone

On Nov 8, 2023, at 16:58, ChristopherH via groups.io <clh5_98=yahoo.com@groups.io> wrote:



Reuben,

From what I've seen, Victron only have BMS for their line of packaged batteries in the 12 and 24 volt ranges.

Chris 

Sent from myPhone

On Nov 8, 2023, at 16:55, Chris Hudson <clh5_98@yahoo.com> wrote:

John,

Thanks for your input and good point about having an ace in the hole!

Chris 

Sent from myPhone

On Nov 8, 2023, at 16:22, john via groups.io <oak_box=yahoo.com@groups.io> wrote:



I don't have a LOT of experience with this, but am now running my electric dinghy with two separate 48V ebike batteries.

I like keeping them separate so that if one gets accidentally discharged (or any other failure), I still have a second battery to get home on.

On Wednesday, November 8, 2023 at 01:59:35 PM CST, Myles Twete <matwete@comcast.net> wrote:

Thought: Dangerous for the switch unless it's a break-before-make or other exclusive-or arrangement.

 

Why: You've been running for hours on one string, then decide to switch to the other.  If you thought that you'd just use a standard marine battery combiner switch, you could accidentally switch to "ALL" position, which would then put both strings in parallel thru the switch, quickly shorting it and possibly melting the housing.  Might also have a problem with that type of switch switching between each string.

 

With Lithium-Ion there's something to be said for having separate strings---ability to switch and get a higher pack voltage again for a time giving higher power/speed than if the strings were paralleled and slowly going down together.  But really, a slowly dropping voltage is better than one that drops much faster due to not paralleling.  Not as much of a big deal with LiFePo, but still, I'd tend to think paralleling is better.

 

Just a thought.

-MT

 

From: electricboats@groups.io [mailto:electricboats@groups.io] On Behalf Of ChristopherH via groups.io
Sent: Wednesday, November 8, 2023 11:49 AM
To: electricboats@groups.io
Subject: Re: [electricboats] Parallel LiFePO4 Packs

 

Bobkart,

Thanks for the reply. Actually I'm proposing to have 2 independent 16 cell strings with the ability to parallel them at the 48V level with switches, not at the cell level. Thoughts on that?

 

Chris 

Sent from myPhone

On Nov 8, 2023, at 14:40, bobkart <couch45@msn.com> wrote:



Connecting two 230Ah cells together in parallel (sixteen times) would allow you to treat the 32 cells as one large 16S 48V x 460Ah battery

BMS, load, charger, capacity monitoring would be none-the-wiser.

 

One concern of that configuration that wouldn't otherwise come up is if one cell in a two-cell pair were to fail.

If the failure is a short, it would bring the other cell with it.

 

---

From: electricboats@groups.io <electricboats@groups.io> on behalf of ChristopherH via groups.io <clh5_98=yahoo.com@groups.io>

Sent: Wednesday, November 8, 2023 10:34 AM
To: electricboats@groups.io <electricboats@groups.io>
Subject: [electricboats] Parallel LiFePO4 Packs

 

Hi Group,
My Morgan Out Island 41 is ready for new batteries. I'm ready to embrace LiFePO4. When I originally converted to electric I built and glassed in 2 battery boxes to hold 2 banks of 8 (16 batteries) golf cart batteries. I always run with both banks in parallel, but have the ability to run on just 1 and this has worked well. Unfortunately this size battery box doesn't make efficient use of most individual LiFePO4 cells. I would however be able to use 32 X 230Ah EVE cells in 1 battery box, leaving the other box for some other purpose. My questions: I'd like to be able to run the 2 X 16S strings in parallel. Is this possible with LiFePO4? Is it safe to do this? Any precautions? Would I have 2 separate BMS units? How about capacity monitoring for the 2 banks in parallel? I have a Victron 48V/5KVA Victron Quattro charger inverter. 
Thanks in advance for any assistance/suggestions.

Regards,
Chris Hudson

Sent from myPhone

Re: [electricboats] sevcon controlled electric drive does not rotate

I don't think it happens that much.  When I called Thunderstruck it took a fair amount of back and forth to figure it out and they said that they had never seen it fail before.  This is my second year using the motor with no issues since.

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Re: [electricboats] sevcon controlled electric drive does not rotate

That's it!  Once you take the 3 screws off you'll see the board mounted underneath with a bunch of gunk holding it in place.

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Re: [electricboats] Parallel LiFePO4 Packs

Reuben,

From what I've seen, Victron only have BMS for their line of packaged batteries in the 12 and 24 volt ranges.

Chris 

Sent from myPhone

On Nov 8, 2023, at 16:55, Chris Hudson <clh5_98@yahoo.com> wrote:

John,

Thanks for your input and good point about having an ace in the hole!

Chris 

Sent from myPhone

On Nov 8, 2023, at 16:22, john via groups.io <oak_box=yahoo.com@groups.io> wrote:



I don't have a LOT of experience with this, but am now running my electric dinghy with two separate 48V ebike batteries.

I like keeping them separate so that if one gets accidentally discharged (or any other failure), I still have a second battery to get home on.

On Wednesday, November 8, 2023 at 01:59:35 PM CST, Myles Twete <matwete@comcast.net> wrote:

Thought: Dangerous for the switch unless it's a break-before-make or other exclusive-or arrangement.

 

Why: You've been running for hours on one string, then decide to switch to the other.  If you thought that you'd just use a standard marine battery combiner switch, you could accidentally switch to "ALL" position, which would then put both strings in parallel thru the switch, quickly shorting it and possibly melting the housing.  Might also have a problem with that type of switch switching between each string.

 

With Lithium-Ion there's something to be said for having separate strings---ability to switch and get a higher pack voltage again for a time giving higher power/speed than if the strings were paralleled and slowly going down together.  But really, a slowly dropping voltage is better than one that drops much faster due to not paralleling.  Not as much of a big deal with LiFePo, but still, I'd tend to think paralleling is better.

 

Just a thought.

-MT

 

From: electricboats@groups.io [mailto:electricboats@groups.io] On Behalf Of ChristopherH via groups.io
Sent: Wednesday, November 8, 2023 11:49 AM
To: electricboats@groups.io
Subject: Re: [electricboats] Parallel LiFePO4 Packs

 

Bobkart,

Thanks for the reply. Actually I'm proposing to have 2 independent 16 cell strings with the ability to parallel them at the 48V level with switches, not at the cell level. Thoughts on that?

 

Chris 

Sent from myPhone

On Nov 8, 2023, at 14:40, bobkart <couch45@msn.com> wrote:



Connecting two 230Ah cells together in parallel (sixteen times) would allow you to treat the 32 cells as one large 16S 48V x 460Ah battery

BMS, load, charger, capacity monitoring would be none-the-wiser.

 

One concern of that configuration that wouldn't otherwise come up is if one cell in a two-cell pair were to fail.

If the failure is a short, it would bring the other cell with it.

 

---

From: electricboats@groups.io <electricboats@groups.io> on behalf of ChristopherH via groups.io <clh5_98=yahoo.com@groups.io>

Sent: Wednesday, November 8, 2023 10:34 AM
To: electricboats@groups.io <electricboats@groups.io>
Subject: [electricboats] Parallel LiFePO4 Packs

 

Hi Group,
My Morgan Out Island 41 is ready for new batteries. I'm ready to embrace LiFePO4. When I originally converted to electric I built and glassed in 2 battery boxes to hold 2 banks of 8 (16 batteries) golf cart batteries. I always run with both banks in parallel, but have the ability to run on just 1 and this has worked well. Unfortunately this size battery box doesn't make efficient use of most individual LiFePO4 cells. I would however be able to use 32 X 230Ah EVE cells in 1 battery box, leaving the other box for some other purpose. My questions: I'd like to be able to run the 2 X 16S strings in parallel. Is this possible with LiFePO4? Is it safe to do this? Any precautions? Would I have 2 separate BMS units? How about capacity monitoring for the 2 banks in parallel? I have a Victron 48V/5KVA Victron Quattro charger inverter. 
Thanks in advance for any assistance/suggestions.

Regards,
Chris Hudson

Sent from myPhone

Re: [electricboats] Parallel LiFePO4 Packs

John,

Thanks for your input and good point about having an ace in the hole!

Chris 

Sent from myPhone

On Nov 8, 2023, at 16:22, john via groups.io <oak_box=yahoo.com@groups.io> wrote:



I don't have a LOT of experience with this, but am now running my electric dinghy with two separate 48V ebike batteries.

I like keeping them separate so that if one gets accidentally discharged (or any other failure), I still have a second battery to get home on.

On Wednesday, November 8, 2023 at 01:59:35 PM CST, Myles Twete <matwete@comcast.net> wrote:

Thought: Dangerous for the switch unless it's a break-before-make or other exclusive-or arrangement.

 

Why: You've been running for hours on one string, then decide to switch to the other.  If you thought that you'd just use a standard marine battery combiner switch, you could accidentally switch to "ALL" position, which would then put both strings in parallel thru the switch, quickly shorting it and possibly melting the housing.  Might also have a problem with that type of switch switching between each string.

 

With Lithium-Ion there's something to be said for having separate strings---ability to switch and get a higher pack voltage again for a time giving higher power/speed than if the strings were paralleled and slowly going down together.  But really, a slowly dropping voltage is better than one that drops much faster due to not paralleling.  Not as much of a big deal with LiFePo, but still, I'd tend to think paralleling is better.

 

Just a thought.

-MT

 

From: electricboats@groups.io [mailto:electricboats@groups.io] On Behalf Of ChristopherH via groups.io
Sent: Wednesday, November 8, 2023 11:49 AM
To: electricboats@groups.io
Subject: Re: [electricboats] Parallel LiFePO4 Packs

 

Bobkart,

Thanks for the reply. Actually I'm proposing to have 2 independent 16 cell strings with the ability to parallel them at the 48V level with switches, not at the cell level. Thoughts on that?

 

Chris 

Sent from myPhone

On Nov 8, 2023, at 14:40, bobkart <couch45@msn.com> wrote:



Connecting two 230Ah cells together in parallel (sixteen times) would allow you to treat the 32 cells as one large 16S 48V x 460Ah battery

BMS, load, charger, capacity monitoring would be none-the-wiser.

 

One concern of that configuration that wouldn't otherwise come up is if one cell in a two-cell pair were to fail.

If the failure is a short, it would bring the other cell with it.

 

---

From: electricboats@groups.io <electricboats@groups.io> on behalf of ChristopherH via groups.io <clh5_98=yahoo.com@groups.io>

Sent: Wednesday, November 8, 2023 10:34 AM
To: electricboats@groups.io <electricboats@groups.io>
Subject: [electricboats] Parallel LiFePO4 Packs

 

Hi Group,
My Morgan Out Island 41 is ready for new batteries. I'm ready to embrace LiFePO4. When I originally converted to electric I built and glassed in 2 battery boxes to hold 2 banks of 8 (16 batteries) golf cart batteries. I always run with both banks in parallel, but have the ability to run on just 1 and this has worked well. Unfortunately this size battery box doesn't make efficient use of most individual LiFePO4 cells. I would however be able to use 32 X 230Ah EVE cells in 1 battery box, leaving the other box for some other purpose. My questions: I'd like to be able to run the 2 X 16S strings in parallel. Is this possible with LiFePO4? Is it safe to do this? Any precautions? Would I have 2 separate BMS units? How about capacity monitoring for the 2 banks in parallel? I have a Victron 48V/5KVA Victron Quattro charger inverter. 
Thanks in advance for any assistance/suggestions.

Regards,
Chris Hudson

Sent from myPhone

Re: [electricboats] sevcon controlled electric drive does not rotate

Hey everyone, thanks so much for your feedback!
On my motor what I'm assuming is the board is located as part of a fully encapsulated unit that flush fits in the back and attached with the 3 cross head screws…?
I'm going to have a crack at testing it this weekend…
Btw, picture of installation attached…


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