Lithium Batteries (for the rest of us)

[SVI]

Originally Posted by Hyprdrv

Charlie,
I'll be running a 144V system at a 80A peak and probably 100Ahr, hoping to get 200Ahr batteries if the price works out. That should give me around 2 hours of run time on bats alone at 6/7 knots.

How do you plan to charge these?
You need to plan the emergency motoring at full load for some time (strong wind / current etc.), so you need to charge at 144V at 80A. That's 11.5kw, very few chargers can do that. You go with a DC generator?

[Hyprdrv]

I have 3 means to charge the batteries.
1. Regen from the props. Yes this is a small charge at around 2 to 3 amps (total, 2 E-motors on my cat) while sailing at speeds around 8 knots. More if I'm going faster but over a long cruise it adds up.
2. Shore power, I have a BRUSA charger, 240V to 144V.
3. I have a 16 KW genset that can send up to 80A to the batteries or run the E-motors using partial load from the genset and part to the batteries.
The hard part is figuring out how to protect the bats from overcharging. My genset has veriable output so I could say set the genset to output 168V and then reduce the output once the batteries are close to 95%.
48x3.5v= 168V

Steve in Solomons MD

[hellosailor]

Maine-
I suspect no one put AGMs to the task the same way, because we all believed AGM was "just" an improvement in the existing technology, not something based on a totally new chemistry. Kinda like finding a zebra in your horse barn: You'd give it hay and oats and never suspect it might be carnivorous, would you? You'd just wonder, who painted the pony.

Steve-
If you want to protect the batteries from overcharge, couldn't you use a high voltage alarm and set that to trip a relay, which in turn would "adjust" your generator down to lower output? Rashly assuming you could switch something (resistor?) to make that adjustment.

[goboatingnow]

AGM was "just" an improvement in the existing technology

This is what the marketeers thought AGM could be used to do , sell a particular form of LA technology into markerts that hahdnt used them as "improved" technology

AGM isnt improved, its just "different:

so its not a zebra came along, more, you trying to put a race horse behind a plough and wondering why he just dropped dead, given the massive money you paid for him

dave

[hellosailor]

" put a race horse behind a plough "
Oh you city slickers. The horse goes in front of the plow, not behind it. No wonder your horse don't work! <VBG>

[goboatingnow]

Originally Posted by hellosailor

" put a race horse behind a plough "
Oh you city slickers. The horse goes in front of the plow, not behind it. No wonder your horse don't work! <VBG>

My bad, and im a country boy that actually learnt to plough with a horse at 10.

My dad would be turning in his grave sheesh.....


Dave

[I.Grind]

Originally Posted by goboatingnow

trying to put a race horse behind a plough and wondering why he just dropped dead, given the massive money you paid for him dave

Awesome analogy, but I think that belongs in the jokes forum. I almost hurt myself laughing!

[Hyprdrv]

Hellosailor,
That's the plan somewhat but I'm not familiar with setting up relays.
That's also the beauty of LiFePo4's, I can just shut the Genset off when the bats get to 95%. Since the Genset, by the way I didn't mention that the output on the genset is rectified to 144V DC, can split the service between the bats, E-motors, and the house bank (144V to 12V charger) once the output on the genset shows 0-5A output I just shut it off if I'm not running the motors so I wouldn't want it to just shut off automatically. A relay to the feed of the batteries would drop it off line. The Genset supply doesn't go through a charger but directly to the batteries so if the motors where running they could still get a feed of 80A. The relay would be the way to go I just have to figure out how to install it.

I'm running a pack of 12 Northstar Agm's at this point which has lasted me 8 years. They are still going strong but I have seen a decrease in range off batteries alone over the last year. Not a whole lot but the sag is what is really noticeable. I think the biggest advantage to AGM's was the no maintenance side to them. Just check the capacity 2 or 3 times a year, clean the terminals and go.

Steve in Solomons MD

[ardoin]

Anyone using LiFePOs for a starting bank? Since I'm replacing the house bank, it is an opportunity to change out the starting bank as well.

[Maine Sail]

Originally Posted by ardoin

Anyone using LiFePOs for a starting bank? Since I'm replacing the house bank, it is an opportunity to change out the starting bank as well.

I use my LiFePO4 as an "everything" bank, it does it all... I have a single group 31 AGM as an emergency / reserve battery.

[ardoin]

I'm looking to simplify the boat. I have a relay charger that connect the banks based on sensed voltage. (it is a BlueSea ACR) and I don't want it to cause problems. At the same time adding another bank with HV and LV relays will complicate things. It is all a tradeoff. Do you think that 200Ah will be okay for a starting bank? Going to one bank for all would be good, but how have you hooked up your alternate source for emergencies?

[campr]

Originally Posted by Maine Sail

I use my LiFePO4 as an "everything" bank, it does it all... I have a single group 31 AGM as an emergency / reserve battery.

Wait... Everything, even starting?

[familycruisers]

Originally Posted by campr

Wait... Everything, even starting?

A starter is fractional c load for these.
I've also had no problems charging them with my standard 50 amp alternator that outputs in the 13.75 range. Had to test that with this never ending nor'easter spinning over us. No sun for a week and a day...

[Maine Sail]

Originally Posted by campr

Wait... Everything, even starting?

Yes everything. Same as I have been doing with lead acid banks for over 25 years, except the LiFePO4 does not even know the engine started and the LA's sag a bit in voltage.....

With a properly sized healthy house bank, LA or LifePO4, starting an AUX engine, even at 50% DOD for LA, and 80% DOD for LiFePO4 is a non issue.

[hellosailor]

Maine, you really shouldn't let folks know about that. Next thing you know, the kids will be begging to learn MATH and Ohm's Law and all that real scary stuff. And, you know, once they figure out it is basic math and not magic...there you go, the whole priesthood becomes unemployed and they're ALL going to come looking for you.

Really. You know?