Engineering question

[dgfreeze]

How much weight is too much per square inch for the floor in my battery compartment? I’m thinking about adding a third battery to be safe with my new stereo system, but if I do that, I’d like to rearrange my current batteries, and add the second one by fabricating a stainless “rack”, and putting the third one above the two on the bottom. My primary concern is putting too much weight on the floor, and causing issues there. It would be braced at the top, but the top brace would not be load bearing, just bracing from sway and wiggle. Here are a few rough sketches of what my mind is thinking. It would allow me to relocate my switches and some other stuff from the walls to this frame, and the frame would be able to double as a built in buss bar.

 

[dgfreeze]

The top tray is several inches offset from the bottom to mimic the curvature of the hull. Here’s a current pic of my battery compartment. I would be rearranging them to be along the side of the hull, as opposed to against the back wall of the compartment.

I’m just not sure how much concentrated weight the fiberglass can handle, and I don’t want to create issues for later that I’ll regret.

 

[Jim_in_Delaware]

It might be simpler to just replace the existing batteries with two lithium batteries.

Jim

 

[FSH 210 Sport]

You could go with lithium house batteries and cut the house battery weight by 55% and get twice the useable power…. Just keep the lead acid start battery

 

[dgfreeze]

Probably should have mentioned, I’ve already got a spare battery, and I hate to see it just sit in a corner. Lithium batteries are awful pricey, but if this pipe dream doesn’t pan out, might consider that route.

 

[GTBRMC]

Another consideration is how much weight do you want to have that far to port side in your boat? Two batteries in my 230 balanced off my weight at the helm (well, almost) but if the Admiral was with me, we got a bit heavy to port side. Three lead acid batteries would make this problem that much worse.

Would not be the end of the world, of course. But absent aftermarket trim tabs, the lack of ability to trim using outdrives makes these boats a bit more sensitive to lateral load imbalances and is one downside to these boats.

PS: There are plenty of jetboaters with 3 or even 4 batteries in that location, so it is doable. However, lifting a battery up & slightly outboard increases the moment arm a bit. I doubt it would be terrible, but it would increase the center of gravity on the port side some.

 

[dgfreeze]

Yep, I considered the extra weight another battery would add, but as of now, I’ve got no listing issues. I’ve got a stern anchor and tool kit in the opposite side that helps offset things, probably at least the weight of one battery.

 

[Judge]

Just some info on the Lithium Battery route...... I did a Lithium Conversion in my motorhome last year so I have a lot of time in R & D when it comes to LiFePO4 batteries.

Charging - Make sure you have a charger capable of charging Lithium batteries. Lithium batteries typically require 14.6V to be fully charged. Depending on the battery the float charge may be 13.6 or 14.6V so you want a configurable charger or one with a Lithium setting.

Stator - I haven't seen the specs on the Yamaha Stator but depending on the size of the LiFePO4, they can cause alternators to overheat and be damaged or shorten their life trying to keep the batteries charged. I have two alternators and a BIM (Battery Isolation Manager) on my motorhome (F-550 chassis) so it is not an issue. Yamaha Twins would mean two stators so it might not be an issue.... but I would try to talk to someone at Yamaha to determine the capabilities and limitations of stator.

Starting - You can use LiFePO4 batteries as a starting batteries in some cases. I am using 170Ah batteries from BIgBattery and I have a Cummins Onan 6000 Diesel Generator that is started by the house batteries. I originally installed three 170Ah batteries for 510Ah total. They fired up the generator with no problem... the starter even seemed to spin faster than it did with the original flooded batteries. The batteries I used provide up 350A for up to 6 seconds.

Temperature - The BMS built into the BigBattery LIFePO4's allow charging between 32F and 130F. Optimal discharge temps are 59F - 95F but you can discharge them safely discharge them below 0F or over 100F but you will shorten their life if you do that regularly.



Lithium is an expensive way to go..... but if you need or want a lot of battery power, it really is the best way to go. I now have five 170Ah batteries in the motorhome and can run one of my two A/C units overnight without running the generator. I can run a convection / microwave oven or any 120V item without any issues.

With proper care and use they can last 10 years (meaning you would have replaced lead acid batteries 2 or even 3 times by then). And as mentioned you can cut the weight by 40 - 50% as well.

 

[dgfreeze]

Good information, and I’ll certainly be researching these concerns if I get serious about lithium.

 

[FSH 210 Sport]

Just some info on the Lithium Battery route...... I did a Lithium Conversion in my motorhome last year so I have a lot of time in R & D when it comes to LiFePO4 batteries.

Charging - Make sure you have a charger capable of charging Lithium batteries. Lithium batteries typically require 14.6V to be fully charged. Depending on the battery the float charge may be 13.6 or 14.6V so you want a configurable charger or one with a Lithium setting.

Stator - I haven't seen the specs on the Yamaha Stator but depending on the size of the LiFePO4, they can cause alternators to overheat and be damaged or shorten their life trying to keep the batteries charged. I have two alternators and a BIM (Battery Isolation Manager) on my motorhome (F-550 chassis) so it is not an issue. Yamaha Twins would mean two stators so it might not be an issue.... but I would try to talk to someone at Yamaha to determine the capabilities and limitations of stator.

Starting - You can use LiFePO4 batteries as a starting batteries in some cases. I am using 170Ah batteries from BIgBattery and I have a Cummins Onan 6000 Diesel Generator that is started by the house batteries. I originally installed three 170Ah batteries for 510Ah total. They fired up the generator with no problem... the starter even seemed to spin faster than it did with the original flooded batteries. The batteries I used provide up 350A for up to 6 seconds.

Temperature - The BMS built into the BigBattery LIFePO4's allow charging between 32F and 130F. Optimal discharge temps are 59F - 95F but you can discharge them safely discharge them below 0F or over 100F but you will shorten their life if you do that regularly.



Lithium is an expensive way to go..... but if you need or want a lot of battery power, it really is the best way to go. I now have five 170Ah batteries in the motorhome and can run one of my two A/C units overnight without running the generator. I can run a convection / microwave oven or any 120V item without any issues.

With proper care and use they can last 10 years (meaning you would have replaced lead acid batteries 2 or even 3 times by then). And as mentioned you can cut the weight by 40 - 50% as well.

Two cents…

The stator is not an issue with the PMG / permanent magnet generators we have in our boats, as they are always at full output. Excess voltage is shunted to ground. These alternators in our boats differ from your F-550 alternators in that your trucks alternators vary the magnetic flux or field strength to regulate their output.

Charging can be done with any charger that has an AGM setting on it. While not perfect it will work.

Life; The life of LiFePO batteries is determined by cycles, a cycle being every time you apply a charge, on the low end is 3500 cycles. That means if you charged them every day they’d last 10 years. If you only cycle them 180 times a year that puts their life out to 20 years. The high end of the cycles is 12,000 for a LiFePO battery as long as you don’t abuse them.

 

[dgfreeze]

I think I'll be all but scrapping this double decker battery stacker idea. I still like the space saving aspect of it, but my concerns about the weight of a second battery stacked on top of the bottoms ones just doesn't make me feel good about it. If my two battery setup is lacking, I think all you guys preaching lithium are probably right. Thanks to all you guys who chimed in and talked me off my ledge.

 

[adrianp89]

I've seen 100ah lithiums get down to $300 on Amazon. Getting close to pulling the trigger. Hoping I can catch one at $250 during black friday.

 

[Judge]

Two cents…

The stator is not an issue with the PMG / permanent magnet generators we have in our boats, as they are always at full output. Excess voltage is shunted to ground. These alternators in our boats differ from your F-550 alternators in that your trucks alternators vary the magnetic flux or field strength to regulate their output.

Charging can be done with any charger that has an AGM setting on it. While not perfect it will work.

Life; The life of LiFePO batteries is determined by cycles, a cycle being every time you apply a charge, on the low end is 3500 cycles. That means if you charged them every day they’d last 10 years. If you only cycle them 180 times a year that puts their life out to 20 years. The high end of the cycles is 12,000 for a LiFePO battery as long as you don’t abuse them.

Thanks for the stator info on our boats. I'm used to stators on my BRP snowmobile engines and they do have some limitations.

Fair points on the LiFePO4's..... but you do want to watch using an AGM charger because the Adsorption, Bulk and Float charging phases aren't applicable to most LiFePO4's.

Some chargers will put Adsorption Phases at 15V, which is too high and cause the BMS to shut down charging. You just want to check then specs for the AGM charging profiles to make sure it won't cause issues for a particular LiFePO4.

The BigBattery LiFePo4 batteries I use have an upper charge limit of 14.7V. If the voltage gets higher the BMS shuts down the battery to prevent damage to the cells.

 

[Judge]

I think I'll be all but scrapping this double decker battery stacker idea. I still like the space saving aspect of it, but my concerns about the weight of a second battery stacked on top of the bottoms ones just doesn't make me feel good about it. If my two battery setup is lacking, I think all you guys preaching lithium are probably right. Thanks to all you guys who chimed in and talked me off my ledge.

I think that is a smart move. I'd personally be worried about choppy water and flexing causing issues over times.

If you really want to cut weight and add capacity, Lithium would be worth considering.

 

[BlkGS]

Personally, I would.just make your battery cradle a bit stronger and.roll with marine batteries.

I'm not gonna go on record saying I'm a chemist, but this video gives something to think about.

https://www.reddit.com/r/interestingasfuck/comments/v1pooo

 

[dgfreeze]

Personally, I would.just make your battery cradle a bit stronger and.roll with marine batteries.

I'm not gonna go on record saying I'm a chemist, but this video gives something to think about.

https://www.reddit.com/r/interestingasfuck/comments/v1pooo

Yeah, I’ve seen what a small phone battery does when exposed to water, it’s no joke, and something to be aware of. That said, there’s a series of unfortunate events that would have to take place for it to become an issue.

 

[FSH 210 Sport]

Personally, I would.just make your battery cradle a bit stronger and.roll with marine batteries.

I'm not gonna go on record saying I'm a chemist, but this video gives something to think about.

https://www.reddit.com/r/interestingasfuck/comments/v1pooo

Bad information is worse than no information, you really should do your home work before posting such “inflammatory“ statements.

https://ecopowerit.com/blogs/news/safety-of-using-lithium-iron-phosphate-lfp-as-an-energy-storage-cell

There is a huge difference between Lithium iron disulfide, which is what is in the energizer battery and Lithium iron phosphate, chemistry is the key.

 

[dgfreeze]

Bad information is worse than no information, you really should do your home work before posting such “inflammatory“ statements.

https://ecopowerit.com/blogs/news/safety-of-using-lithium-iron-phosphate-lfp-as-an-energy-storage-cell

View attachment 189899



View attachment 189900

There is a huge difference between Lithium iron disulfide, which is what is in the energizer battery and Lithium iron phosphate, chemistry is the key.

Does this apply to all the automotive style lithium batteries? If so, that’s very comforting.

 

[HangOutdoors]

LiFePO4 batteries are Lithium Iron Phosphate, they are very safe. Arguably better the Lead... Lithium Ion and other types of Lithium Batteries are the ones that will explode. I would only use a LiFePO4 in a boat
Lithium Iron Phosphate Vs. Lithium-Ion: Differences and Advantages (epectec.com)

 

[FSH 210 Sport]

Does this apply to all the automotive style lithium batteries? If so, that’s very comforting.

As long as they are LiFePO4 chemistry it does. Early on in my research I investigated the fires that were associated with lithium batteries and leaned that the LiFePO4 were essentially immune to the fire and explosion issues. It took me a very long time to come around to Li ion batteries in my dirt bikes because of the cold weather operating issues as well as the high failure rates of the early Li ion batteries.