What configuration is 'better'; 4S=125Ah or 5P4S=125Ah?

[Fish Freak]

For those of you that have test equipment, can you tell me the how's and why for certain configurations? I'm making 125Ah 12v lead replacement lithiums for marine use and leaning towards the configuration manufacturers use like that Ionic just because they know more than I do.

For instance, what configuration is 'better'; using 4 3.2v 125Ah cells in a 4S=125Ah or using 20 3.2v 25Ah cells in a 5P4S=125Ah layout? Which one could deliver higher C output? Does it matter?

Advantages? Cost is similar. Redundancy - if one 25Ah cell dies, the pack will still work. How often do cells die when they're very well maintained and monitored?

Disadvantages? Complexity? Weight of the 20 cells is several lbs heaver than 4 - important to me with a boat application.

Obviously the BMS-wise config would be totally different. On the first pic, 5P4S, would you monitor each of the 20 cells separately or just the 4 parallel banks?

Pics:


or:

 

[Bob B]

@Fish Freak Good to see you on here.

What are you going to be using the battery for? Trolling motor? Starting Battery? etc. This will determine what BMS you want to use.

I would tend to go with the 4 cells just for simplicity of construction and less connections. Hope you get other opinions on this.

 

[Steve_P]

I am thinking of doing what you are doing as far as building a battery for fishing. We look like we fish the same areas. The only thing I have read is that the smaller cells may take shock and vibration better than the larger ones. I recently built a 3p4s battery, for a solar generator, but am still waiting on my BMS. Thinking about building another one for my trolling motor.
I don't think a high C rate would be important for a trolling motor if that is what you are using it for. I recently tested my 12v 55# ipilot and on 10 I ran 31.5 amps. On 7 I ran 22 amps and at 5 I was down to 12 amps. This was using a lead acid battery. By the way Minn Kota only recommends running at 85% or less for extended periods if you use lifepo4 batteries.

 

[Fish Freak]

@Fish Freak Good to see you on here.

What are you going to be using the battery for? Trolling motor? Starting Battery? etc. This will determine what BMS you want to use.

I would tend to go with the 4 cells just for simplicity of construction and less connections. Hope you get other opinions on this.

Hey Bob! There you are! Yes you are right, the BMS will change if it's a crank or trolling motor battery. Cells are plentiful out there but boy am I having a time picking the right bms for a starting battery! I've got my eye on a separate port Daly that claims to handle fairly high amps on the 'charge' ground side, so I'd connect the outboard to that, and all depth finders and accessories to the 'load' side. One of those Sterling alternator protection devices will be a key addition to this setup, I believe.

I'm planning on doing LifePO for both trolling motor AND crank battery and was totally prepared to go with 4 large cells and may still do that, however, when I saw that torn down Ionic, and read all the pretty darn good reviews on bbcforums it was hard to not consider, because for a crank battery, you need that 3 seconds of high amp burst. Maybe 20 small cells can burst higher and quicker than 4 large cells? Maybe spreading out that high crank impact over 20 contact points puts less stress on the cells? Those are the real questions I hope to answer.

You haven't cranked with yours yet have you Bob?

It seems many bms' take 4-5 seconds before they cut you off for over amp-draw, from what I've found, so there's that going for us, hopefully.

Albert

 

[Fish Freak]

I am thinking of doing what you are doing as far as building a battery for fishing. We look like we fish the same areas. The only thing I have read is that the smaller cells may take shock and vibration better than the larger ones. I recently built a 3p4s battery, for a solar generator, but am still waiting on my BMS. Thinking about building another one for my trolling motor.
I don't think a high C rate would be important for a trolling motor if that is what you are using it for. I recently tested my 12v 55# ipilot and on 10 I ran 31.5 amps. On 7 I ran 22 amps and at 5 I was down to 12 amps. This was using a lead acid battery. By the way Minn Kota only recommends running at 85% or less for extended periods if you use lifepo4 batteries.

Hey Steve;

Lol, that's cool, us fishermen are invading a solar DIY forum! Where do you like to fish?

Building LifePO4 cells for our trolling motors is really a no-brainer with the low cell prices these days, and forums like this with all the info, it's pretty cool stuff. I'm used to carrying 3 group 27 lead AGM's and one group 31 AGM of the pure lead super heavy batteries and saving nearly 200 lbs off the stern of a bass boat could add a few mph of top speed.

That'd make sense that more smaller cells can take vibration better, because inside the aluminum cases there are soft-sided pouch cells, I believe? Our boats bounce, sometimes hard. The analogy could be made to a women's bra; that smaller bra cups have less of a bounce load then giant bra cups :-D ?!?

You're absolutely right about trolling motor's not getting near the C rate of average LifePO cells. I'm currently using a 36v m/k and it pulls about 54 amps on full tilt. That's no big deal. You're also right about avoiding running less than 85%. I've not used lithium on my trolling motors, however, the times I've smoked my Minn Kota control logic boards, I've been running at 100%, so I stopped doing that and stopped smoking boards . I wonder why the specific warning for LifePO4 cells?

What are your Ah storage/load needs for that solar generator and what BMS have you found?

Albert

 

[Pierre]

I think I will go for 4s. The more connections / junctions the more the chance for a potential fault. Much simpler setup , cheaper to maintain , reduced weight , only one BMS to worry about ( BMS is the weak point in any setup ) The bounce issue - surely in both setups all the cells are strapped together with solid busbars and not flexible wire busbars , so one can almost see it as one solid battery in each case ? Have I missed the point somewhere ?

 

[Steve_P]

Hey Steve;

Lol, that's cool, us fishermen are invading a solar DIY forum! Where do you like to fish?

Building LifePO4 cells for our trolling motors is really a no-brainer with the low cell prices these days, and forums like this with all the info, it's pretty cool stuff. I'm used to carrying 3 group 27 lead AGM's and one group 31 AGM of the pure lead super heavy batteries and saving nearly 200 lbs off the stern of a bass boat could add a few mph of top speed.

That'd make sense that more smaller cells can take vibration better, because inside the aluminum cases there are soft-sided pouch cells, I believe? Our boats bounce, sometimes hard. The analogy could be made to a women's bra; that smaller bra cups have less of a bounce load then giant bra cups :-D ?!?

You're absolutely right about trolling motor's not getting near the C rate of average LifePO cells. I'm currently using a 36v m/k and it pulls about 54 amps on full tilt. That's no big deal. You're also right about avoiding running less than 85%. I've not used lithium on my trolling motors, however, the times I've smoked my Minn Kota control logic boards, I've been running at 100%, so I stopped doing that and stopped smoking boards . I wonder why the specific warning for LifePO4 cells?

What are your Ah storage/load needs for that solar generator and what BMS have you found?

Albert

I mainly fish the River for salmon, stripers and shad but spend a lot of time up at Shasta or Whiskeytown. Also like to fish Eagle Lake and Stampede during the summer. I don't much fish for bass unless I am at Shasta. Keep saying I am going to get better.

My boat is a 17' aluminum so speed is not really an issue but would be nice to kick some of the weight out. By adding the trolling motor and two deep cycle batteries my speed dropped from 41 mph to 38 mph. Another huge advantage to Lifepo4 for me would be the ability to charge at a higher rate. I only plan on using the battery for my trolling motor and downriggers. They are separate from my starting motor and electronics. I rarely use my trolling motor for actual trolling most of the time I use it to steer and push with my kicker.

Just like most everyone else I am still learning. I have a Daly 120 amp BMS ordered for my solar generator but not sure it will ever show up. I have another 100 amp Daly ordered that I may use in the mean time. My battery setup is a 3P4S setup with 50 amp batteries for 150 amp hr. If I get the rest of my parts I will test it. Pretty much just waiting on my BMS and my battery capacity monitor. Not really sure why I am building it other than it is a fun project. Hope to have everything done for some camping/fishing trips soon.

 

[Fish Freak]

I mainly fish the River for salmon, stripers and shad but spend a lot of time up at Shasta or Whiskeytown. Also like to fish Eagle Lake and Stampede during the summer. I don't much fish for bass unless I am at Shasta. Keep saying I am going to get better.

My boat is a 17' aluminum so speed is not really an issue but would be nice to kick some of the weight out. By adding the trolling motor and two deep cycle batteries my speed dropped from 41 mph to 38 mph. Another huge advantage to Lifepo4 for me would be the ability to charge at a higher rate. I only plan on using the battery for my trolling motor and downriggers. They are separate from my starting motor and electronics. I rarely use my trolling motor for actual trolling most of the time I use it to steer and push with my kicker.

Just like most everyone else I am still learning. I have a Daly 120 amp BMS ordered for my solar generator but not sure it will ever show up. I have another 100 amp Daly ordered that I may use in the mean time. My battery setup is a 3P4S setup with 50 amp batteries for 150 amp hr. If I get the rest of my parts I will test it. Pretty much just waiting on my BMS and my battery capacity monitor. Not really sure why I am building it other than it is a fun project. Hope to have everything done for some camping/fishing trips soon.

I love fishing our Delta, and I often catch striper and salmon. Occasionally I'll go for a shad binge, it's coming up soon here. I feel like Shasta is an old friend I've spent a lot of time on, but I've never fished Whiskeytown, Stampede or Eagle. I know, I'm missing out, and I've got buddies that keep telling me that. On my list.

For me I spend my whole day fishing while on that 36v bow mounted trolling motor, except for a couple minutes of 75+ mph skips to a new spot, so shedding weight is important to performance and saving money DIY is just plain fun. Lol, I don't really go that fast all the time, but light weight batteries make it and higher speeds possible.

Did you find any Daly bms' with bluetooth and iPhone apps? Will you be monitoring all 12 cells or just the 3P whole banks? What kinda case are you putting it in? Shipping right now really sucks, and because of that I may just order the one Steve at Overkill has on Amazon for my t/m batteries, it's got a bluetooth app and he's got them in stock in the US, Florida. My crank batt bms I'll hafta order from Daly, China, I THINK...?

Where do you live in Sac Steve? I'm in Citrus Heights near Roseville, I-80, Cirby vicinity...

 

[Fish Freak]

I think I will go for 4s. The more connections / junctions the more the chance for a potential fault. Much simpler setup , cheaper to maintain , reduced weight , only one BMS to worry about ( BMS is the weak point in any setup ) The bounce issue - surely in both setups all the cells are strapped together with solid busbars and not flexible wire busbars , so one can almost see it as one solid battery in each case ? Have I missed the point somewhere ?

I'm going to agree with you Pierre. Have you got any bms suggestions, good quality ones you think I should check out? I'd like to have a bluetooth app on my iPhone to keep tabs on it AND configure settings. Higher amp capability for an engine starting battery is a key decision basis for me.

 

[Steve_P]

Did you find any Daly bms' with bluetooth and iPhone apps? Will you be monitoring all 12 cells or just the 3P whole banks? What kinda case are you putting it in? Shipping right now really sucks, and because of that I may just order the one Steve at Overkill has on Amazon for my t/m batteries, it's got a bluetooth app and he's got them in stock in the US, Florida. My crank batt bms I'll hafta order from Daly, China, I THINK...?

Where do you live in Sac Steve? I'm in Citrus Heights near Roseville, I-80, Cirby vicinity...

No I just ordered a pretty basic Daly BMS. Problem is I am already 2 months in and not sure it will ever show up. I have another 100 amp one coming locally so I am guessing that will be here first. I am just using a 4s 12v BMS. Like I said this is all new to me. I will probably do and re-do a few things. As far as a case I am building everything in a Stanley tool box. https://www.stanleytools.com/produc...ol-storage/17-gallon-contractor-chest/033026r It is going to be fairly tight but I have room. I have installed fans and hope I have enough room to keep everything cool. I am mainly building this for camping. Once I get my BMS I should be able to get everything finished in a day or so. I will order the one on Amazon if this does not work out. Wish I would of already. Had to send my solar charge controller back because they sent the wrong one but I am sure I will have another before I have the rest of the parts.

I live right next to Elk Grove. I should be out fishing tomorrow but had a bunch of things I need to get done. Headed for Modoc County for a couple weeks Friday so the build will be on hold for a while. This will probably be the first time in years I have not caught a shad. They are slamming them right now. I am mainly a salmon fisherman and pretty much spend every day I have off work during season chasing them.

 

[Bob B]

Hey Bob! There you are! Yes you are right, the BMS will change if it's a crank or trolling motor battery. Cells are plentiful out there but boy am I having a time picking the right bms for a starting battery! I've got my eye on a separate port Daly that claims to handle fairly high amps on the 'charge' ground side, so I'd connect the outboard to that, and all depth finders and accessories to the 'load' side. One of those Sterling alternator protection devices will be a key addition to this setup, I believe.

I'm planning on doing LifePO for both trolling motor AND crank battery and was totally prepared to go with 4 large cells and may still do that, however, when I saw that torn down Ionic, and read all the pretty darn good reviews on bbcforums it was hard to not consider, because for a crank battery, you need that 3 seconds of high amp burst. Maybe 20 small cells can burst higher and quicker than 4 large cells? Maybe spreading out that high crank impact over 20 contact points puts less stress on the cells? Those are the real questions I hope to answer.

You haven't cranked with yours yet have you Bob?

It seems many bms' take 4-5 seconds before they cut you off for over amp-draw, from what I've found, so there's that going for us, hopefully.

Albert2

The battery I am building is for my RV .... I bought a pre-built one with the Bluetooth interface for my electronics on the boat. That was my first excursion into buying direct from China. I have not tried either battery as a starting battery. I have been researching the possibility of using LTO cells for a starting battery. There are a lot of guys with the audio systems that you can hear from about 5 miles away using the LTO's for starting and for the audio. The charge and discharge range is so large for the LTO's that you can connect it up without even using a BMS. Most of them are just using a heavy duty cell balancer. You can buy a 6 pack of 40AH for around $360. I think the 40 AH will do 400 amps, and if you have a seperate battery for accessories and electronics, you don't need that many AH for the starting battery. These batteries have so many cycles they will last as long as we will ..... if the specs are correct. (This is all research .... not sure if i am going to try to use them or not.) @Craig is a member on here who sells LTO's on Ebay .... and is offering a discount for forum members who want to buy from him without going thru Ebay.

I guess it depends on how big your motor is and how many amps it draws when cranking if you want to go with the LeFePo. The BMS will have to handle pretty large current loads to be used as a starting battery. It would be interesting to know what Ionic uses in their 125A version.

For my RV, I am using the chargery BMS. It doesn't pass current thru the BMS ... it controls the charge and load via external relays. As a boat starting battery, independent control isn't necessary. The relays that Chargery sells are not real great, but there is a thread with guys testing SSR relays instead of a contact type relay.

Lot of things to think about ....

 

[Forbisher]

For me I spend my whole day fishing while on that 36v bow mounted trolling motor, except for a couple minutes of 75+ mph skips to a new spot, so shedding weight is important to performance and saving money DIY is just plain fun. Lol, I don't really go that fast all the time, but light weight batteries make it and higher speeds possible.

Wow, what kind of boat and set up to go 75 mph?

 

[Pierre]

I'm going to agree with you Pierre. Have you got any bms suggestions, good quality ones you think I should check out? I'd like to have a bluetooth app on my iPhone to keep tabs on it AND configure settings. Higher amp capability for an engine starting battery is a key decision basis for me.

Hi FF , the one that Overkill sells is the same one that I have been playing with and reviewed. It has the features you are looking for e.g. the bluetooth app etc. For your cranking battery I would use the same one but switch the output through a SSR or heavy duty marine relay. This way you can monitor both on your iPhone.a Heavy duty Daly ( 200 amp continuous ) will set you back about $200 + .
Another one that Will seems to like is the Electrodacus but I have no experience with this one.

 

[Fish Freak]

The battery I am building is for my RV .... I bought a pre-built one with the Bluetooth interface for my electronics on the boat. That was my first excursion into buying direct from China. I have not tried either battery as a starting battery. I have been researching the possibility of using LTO cells for a starting battery. There are a lot of guys with the audio systems that you can hear from about 5 miles away using the LTO's for starting and for the audio. The charge and discharge range is so large for the LTO's that you can connect it up without even using a BMS. Most of them are just using a heavy duty cell balancer. You can buy a 6 pack of 40AH for around $360. I think the 40 AH will do 400 amps, and if you have a seperate battery for accessories and electronics, you don't need that many AH for the starting battery. These batteries have so many cycles they will last as long as we will ..... if the specs are correct. (This is all research .... not sure if i am going to try to use them or not.) @Craig is a member on here who sells LTO's on Ebay .... and is offering a discount for forum members who want to buy from him without going thru Ebay.

I guess it depends on how big your motor is and how many amps it draws when cranking if you want to go with the LeFePo. The BMS will have to handle pretty large current loads to be used as a starting battery. It would be interesting to know what Ionic uses in their 125A version.

For my RV, I am using the chargery BMS. It doesn't pass current thru the BMS ... it controls the charge and load via external relays. As a boat starting battery, independent control isn't necessary. The relays that Chargery sells are not real great, but there is a thread with guys testing SSR relays instead of a contact type relay.

Lot of things to think about ....

There's lots to think about, and I'm thinkin' that I'm amazed at what a small world it is, because Craig and I have had a few convo's on this, and he's doing a buy soon that may have some of my cells on it. @Craig when are you coming back from Idaho again? From their spec sheet, I'm gonna guess that Ionic is using a plain ol' 100A bms not too unlike the one Overkill is selling. Am I being a little presumptuous? Look at their spec sheet, I'll bet there is no SSR inside that case, I mean, Battleborn doesn't have anything but a 100a bms in that case Will popped open, and I'll bet it could start my outboard or a car engine no problem. Guys on bbsboards have done it. Specs here from Ionic 125A, it's a 'heavy' LifePO4 batt because of the 20 individual 25ah cells:



An LTO bank is just going to be too big for a boat bilge installation. Now if @Craig lets me try it, I think his small 12v LTO bank could be a good booster battery for my experiment... I hear ya about this all being research, I've done nothing but push pencils on this crazy notion. Gotta get my hands on some cells here real soon.

 

[Fish Freak]

Hi FF , the one that Overkill sells is the same one that I have been playing with and reviewed. It has the features you are looking for e.g. the bluetooth app etc. For your cranking battery I would use the same one but switch the output through a SSR or heavy duty marine relay. This way you can monitor both on your iPhone.a Heavy duty Daly ( 200 amp continuous ) will set you back about $200 + .
Another one that Will seems to like is the Electrodacus but I have no experience with this one.

Nice, once I have word that my cells are on the way, I'll pick up a couple of those Overkill bms for my low draw setup. How many batteries can that app monitor? Say if I have 3 setups each with an Overkill bms, can the iPhone app monitor multiple batteries?

I'll do some research on how to work that SSR into my setup. I presume it would put amps straight from the cells and bypass the bms, right? Part of me thinks that paying a few bucks more for the HD Daly might be worth it in the long run? Never heard of the Electrodacus but I'll look it up.

 

[Fish Freak]

Wow, what kind of boat and set up to go 75 mph?

There are lots of fishing boats that go real fast in the 'bass boat' category. They use big V6 two stroke outboard motors, mine's 225 Hp, and the hulls designed such that they lift almost the entire boat out of the water at top speed. They're not small boats, my current setup is 20 ft long, and it does in the upper 70's. There are many bigger ones with more hp but few that are as fast. Hoping that trading the lead-acid batteries for LifePO4 might let me crack 80 mph. We don't routinely run at those speeds, but it's about efficiency. I can go 60 mph across a 20 mile lake in no time, without breaking a sweat.

 

[Pierre]

Nice, once I have word that my cells are on the way, I'll pick up a couple of those Overkill bms for my low draw setup. How many batteries can that app monitor? Say if I have 3 setups each with an Overkill bms, can the iPhone app monitor multiple batteries?

I'll do some research on how to work that SSR into my setup. I presume it would put amps straight from the cells and bypass the bms, right? Part of me thinks that paying a few bucks more for the HD Daly might be worth it in the long run? Never heard of the Electrodacus but I'll look it up.

Have a chat with Overkill about monitoring multiple BMS’s on Bluetooth. I am not sure but I think each one can be assigned a password and that you can monitor selectively.
With the bypass SSR / relay the main load current bypasses the BMS. At the moment I am playing with a tiny $10 BMS controlling an 80 amp load through a bypass relay. See my write up in the section under BMS. Works very well but the BMS has limited protection features. Will post more findings soon.

 

[Fish Freak]

Have a chat with Overkill about monitoring multiple BMS’s on Bluetooth. I am not sure but I think each one can be assigned a password and that you can monitor selectively.
With the bypass SSR / relay the main load current bypasses the BMS. At the moment I am playing with a tiny $10 BMS controlling an 80 amp load through a bypass relay. See my write up in the section under BMS. Works very well but the BMS has limited protection features. Will post more findings soon.

That's a great idea Pierre, thanks! Far less expensive!

What do you think of this and how could I make it work (anyone with experience please chime in): if I used a separate port bms with a good bluetooth iPhone app so that I could change charge and load cutoff? Trigger a SSR on the charge port, so that my outboard engine could draw starting amps 300a, 400a+ straight from the battery, but if my alternator overcharged, then the relay would kick off and stop charging? I know of a Sterling alternator protection device that can absorb that shock of cutting alternator lead. Then all my navigation and accessories, less than 40a may be able to connect straight to a load port, which of course cuts only if capacity gets too low? Is there an affordable SSR that can switch 300a, 400a? Can you recommend a good brand?

Would I need a 12v pack larger than 120Ah? Should it be 150Ah or 200Ah to pull 2c from it, for like 3-4 seconds max?

 

[Pierre]

That's a great idea Pierre, thanks! Far less expensive!

What do you think of this and how could I make it work (anyone with experience please chime in): if I used a separate port bms with a good bluetooth iPhone app so that I could change charge and load cutoff? Trigger a SSR on the charge port, so that my outboard engine could draw starting amps 300a, 400a+ straight from the battery, but if my alternator overcharged, then the relay would kick off and stop charging? I know of a Sterling alternator protection device that can absorb that shock of cutting alternator lead. Then all my navigation and accessories, less than 40a may be able to connect straight to a load port, which of course cuts only if capacity gets too low? Is there an affordable SSR that can switch 300a, 400a? Can you recommend a good brand?

Would I need a 12v pack larger than 120Ah? Should it be 150Ah or 200Ah to pull 2c from it, for like 3-4 seconds max?

Hi FF , do you know what the actual cranking amps for your outboard motor are or do you have a way to measure it with a DC 'Peak Hold' clamp meter. I think this accurate information will determine the way forward. Not quite sure what your intention is with the charge port and how that relates to your load current. The charge port protection is a separate issue to the load port. I still have my misgivings about SSR's switching heavy DC loads , specially reactive ( inductive & capacitive ) and the jury is still out until @Steve_S reconvenes said jury. My money is still with heavy duty relay contactors for now.
I have just ordered 2 x 200 amp 12v relays om Amazon ( $13 each ) to experiment with and will report the results.

 

[Steve_S]

Hi FF , do you know what the actual cranking amps for your outboard motor are or do you have a way to measure it with a DC 'Peak Hold' clamp meter. I think this accurate information will determine the way forward. Not quite sure what your intention is with the charge port and how that relates to your load current. The charge port protection is a separate issue to the load port. I still have my misgivings about SSR's switching heavy DC loads , specially reactive ( inductive & capacitive ) and the jury is still out until @Steve_S reconvenes said jury. My money is still with heavy duty relay contactors for now.
I have just ordered 2 x 200 amp 12v relays om Amazon ( $13 each ) to experiment with and will report the results.

Craig is testing SSR's including the Big Lug SSR's. I can't test them in my application as they are uni-directional and not suitable for a common port configuration. They are more than likely fine for a separate port configuration.

I would offer a word of cation on the $13 relay. At that price I highly doubt that it would be a continuous duty HD Contactor. Some people think it is the same as a Starter Relay or other vehicle relay but appearances are deceptive. There are used Gigavac & TE Energy Saver Relays which are rated for continuous duty and being sold for around 45/50 USD on Amazon & EBay. A few members have bought them and are pleased with the result. SSR's for this caliber are not cheap and bi-directional SSR solutions are certainly not going to be cheap either and are a bit of time away from being ready for testing.