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Can Lithium batteries support an AGM installation for Solar Powered Catamaran

Q-Dog said:
You need to be thinking like an EV, not like a house. EV folks build high voltage packs all the time.
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It's not the problem of building a 96V pack (though finding a BMS that is tried and tested may be) it's then charging that from the 48V (or the 230V AC) that will be coming from the panels / inverters / 48V LiFePO4 bank.
 
althemusicwizard said:
I've just found a similar thread to this and a poster called 'pollenface' suggested a similar solution as to the one I've posted here. I've redone the schematic to show switches that could switch the AGM bank between being a 48V bank and a 96V bank. The AGM bank couldn't be charged as well as running, however maybe the solution is to have one AGM bank supplying both motors and the other one being recharged or some combination of this idea depending on the C rate of the AGM bank. Thanks for spotting the 'shorts' guys. Here's the new schematic.
Click to expand...

I think that shows 48V lithium bank and two 96V AGM banks, each consisting of two 48V AGM banks with switch between them.
The lithium bank can switch to parallel with each 48V AGM bank.

When switch in middle separates 96V bank into two 48V banks, I don't think any current can flow to motor.

I think lithium bank is supposed to be able to charge or share current with 48V AGM banks. But can't charge effectively, need it to be higher voltage but regulated current (or voltage.)

Assuming 48V lithium banks are not designed for series use, I think a high current reverse-polarity diode across them (like bypass diode of PV panel) would protect them. That would let you make 96V lithium.

Some form of isolated DC/DC charger could charge multiple 48V AGM banks from 48V lithium bank. An off the shelf method would be inverter fed from lithium, feeding Chargeverter. Inefficiencies of double conversion, but at least it is off the shelf.
 
For anyone who's looked into this problem before (solar boat), I compiled what video history I could find of 'Solarwave 42'. This was the boat that Heike and Micheal Kohler designed and built and now they run Silent Yachts.


In one shot, it shows the nav station and about ten battery bank switches with some of the batteries underneath:

https://flic.kr/p/2pf78HC

They are similar to this product:

https://www.bluesea.com/support/articles/681/Switching_Solutions_for_Multiple_Battery_Banks

I wonder if that is how they solved the problem back then?
 
Hedges said:
I think that shows 48V lithium bank and two 96V AGM banks, each consisting of two 48V AGM banks with switch between them.
The lithium bank can switch to parallel with each 48V AGM bank.

When switch in middle separates 96V bank into two 48V banks, I don't think any current can flow to motor.

I think lithium bank is supposed to be able to charge or share current with 48V AGM banks. But can't charge effectively, need it to be higher voltage but regulated current (or voltage.)

Assuming 48V lithium banks are not designed for series use, I think a high current reverse-polarity diode across them (like bypass diode of PV panel) would protect them. That would let you make 96V lithium.

Some form of isolated DC/DC charger could charge multiple 48V AGM banks from 48V lithium bank. An off the shelf method would be inverter fed from lithium, feeding Chargeverter. Inefficiencies of double conversion, but at least it is off the shelf.
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Thanks for those replies. I'd have to look into diodes etc. as it's above my pay-grade :).......but the combination of separate AGM banks and separate solar inverter for the AGM bank so I could hit it hard when needed, might be a solution.
 
althemusicwizard said:
It's not the problem of building a 96V pack (though finding a BMS that is tried and tested may be) it's then charging that from the 48V (or the 230V AC) that will be coming from the panels / inverters / 48V LiFePO4 bank.
Click to expand...

REC BMS comes in 16s blocks and can be connected up to 128s.
It uses contactors.

How about two contactors, one on battery+, other on battery-
Connects two 48V battery chargers, one from middle to battery+, other from middle to battery-.
(This assumes BMS tolerates cell divergence, as the two 48V sections may not be same voltage. Should be adjustable parameter.)

Use four contactors total. One for each charging source, and one for each end of load. Well, maybe only one needed for load, so three contactors.
Need to isolate load from charging source to prevent excessive reverse-polarity voltage seen by charger.

This would be an all-lithium system, no AGM.
 
Q-Dog said:
www.sigineer.com

96V Inverter Charger 15000 Watt 120/240Vac Pure Sine For Tesla Model 3 Lithium Battery Module

15000 Watt Inverter outputs 15KW Pure sine wave power from 96v to 120/240V or 115/230V. Designed for Tesla Model 3 S Battery Modules.
www.sigineer.com www.sigineer.com
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Thanks for that......it just has to be the other way round. The input is 96V to 230V AC output. Now if it was 230V AC to 96V DC, then it would kind of work direct to the motors from the output of the inverters (paralleled), however you'd only get 10kW from the two inverters so would not be powerful enough as each motor can take a max of 21kW each. Thanks though.
 
Build 96 volt bank. Use 96 volt mppt to charge from solar and 96 volt inverters to provide house AC loads. Propulsion is 96 volt direct from batteries.
 
rhino said:
Have you also done calculations on how big of battery you'd need for that large of motor let alone two of them? Have you seen https://www.youtube.com/c/TheDigitalMermaid/videos ? She is converting her yacht to electric motor from diesel but will be using much smaller single motor and will have quite big battery bank.
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Hers is a sailboat isn't it? This is a power cat. She won't have a 60-90kWh battery bank on her yacht will she?
 
Thanks for the replies. The lack of 96V stuff and the fact that it IS 96V stuff, has made me decide that as far as electric is concerned, I'm sticking with 48V. The 48V stuff in the UK has come down in price to make this feasible and I haven't got the kind of budget that 'yacht owners' have. It will remain to be seen if the 48V motors will be able to drive the cat at hull speed (8 knots). If so, all well and good. As the petrol tanks have already been installed, a couple of smaller petrol outboards (20-30HP) might make sense as redundancy.
 
althemusicwizard said:
Thanks for the replies. The lack of 96V stuff and the fact that it IS 96V stuff, has made me decide that as far as electric is concerned, I'm sticking with 48V. The 48V stuff in the UK has come down in price to make this feasible and I haven't got the kind of budget that 'yacht owners' have. It will remain to be seen if the 48V motors will be able to drive the cat at hull speed (8 knots). If so, all well and good. As the petrol tanks have already been installed, a couple of smaller petrol outboards (20-30HP) might make sense as redundancy.
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I've just come across a brand new outboard from E-Propulsion, the X-40D. I've no idea how much it's going to cost, but it's almost like it was made for my cat. Back to the drawing board as it's 96V. I'm going to take a look at the EV forums and find outhow to build a 96V bank and how to charge it.
 
althemusicwizard said:
Thanks for those replies guys. I'm finding 96V stuff in the UK is non-existent. I've installed a 48V home system using solar inverters and it's been extremely successful. I do have a lead-acid bank. The need for 50HP motors is because the cat is 40ft, with a 20ft beam. It will weigh in around 4-5tonnes (depending on batteries, panels and motors......that lot alone could be 1.5tonnes). I'd like to be able to cruise at 6-8knots. The use of AGM batteries is really as a buffer between the 48V LiFePO4 bank. All the companies have battery solutions but they're probably at least twice the price of sourcing a solution myself.
Click to expand...

a few 300A 32S BMS in parallel

Tanfon 96v mppt
 
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pollenface said:
a few 300A 32S BMS in parallel

Tanfon 96v mppt
Click to expand...
Thanks for that link. I'll have to find out how much the E-Propulsion X40 are going to cost and work from there. Their own G-Series batteries are
rated at a maximum charge / discharge of 100A, therefore to run the 40kW motor at peak you'd need four batteries in parallel, I think. Most BMS for lithium batteries can usually handle at least 100A can't they?
I just Googled and found this company who seem to offer bespoke solutions:

www.ctsbattery.com

Quality E Scooter Battery Pack, Solar Battery Storage System factory, E Scooter Battery Pack manufacturer, Solar Battery Storage System from China

China leading provider of E Scooter Battery Pack and Solar Battery Storage System, Hunan CTS Technology Co,.ltd is Solar Battery Storage System factory.
www.ctsbattery.com

Lots to think about.
 
I'm planning a 96v setup for my boat too. So interesting discussion.

Looking at other eboat conversations, the tend to need very little power at displacement speeds, and that's hull dependant. After that power requirements are exponential.

Good displacement hulls are long and thin (higher displacement speeds), so a cat is likely to be the perfect choice!

My boat isn't a cat, it does 5 knots with 5hp and 8 knots at 40hp. That last 3 knots really uses a stack of energy. So electrification for me is displacement mode, max 6 knots, and a 10kw motor, running at around 5kw, is my goal.

I'd be surprised if you need any more than 10kw in each pontoon to hit your displacement speed. Thoughts?

See Candela C-8 for a high speed eboat!
 
I have thought about that as well.

I use a Batrium BMS in my MotorHome and like it. I believe you can make a 96v or 144v battery with that bms.

If at all possible drop the Elco motor down to a 48v model. It will make life better (and cheaper).
 
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