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Is it viable to charge a 72V lithium bank with Genasun Boost mppts? On a Catamaran.

flatwater

flatwater

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Joined
Oct 26, 2024
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6
Location
san francisco california
I was set on 48VDC for my catamaran electric conversion. But RPMs needed and amperage getting too high (BMS and genset) have gotten me back looking at 72V (and 96V).

For a boat, I have a fair bit of space on the roof. 20' wide and 12' long. (boat is 30' wide and 55' long)
I can keep building off the back a bit as well.

Its a sailboat.
So the sails and boom and angles of course will be shading.

I would like to get away with a 72V bank.
Has anyone done this without needing to put too many panels in series?
are the Genasun controllers really that effective? Hard to commit to a product from just one company in case they stop making them.

Thank you all.
 
I am aware of the higher base voltage panels out there. Thanks to this Forum!

ttps://www.solarreviews.com/manufacturers/sunpower/solar-panels/sunpo19768spre20435com

and the FirstSolar 75V panels.

I would prefer to use more standard panels that are replaceable and easier to buy. On my last boat I used the very pricey (1200 each) panels from Solara.

SOLARA Power M Series Marine Walk-On Panels - e Marine Systems

SOLARA Power M Series Marine Walk-On Panels offer highest performance with top quality. The attractive black and elegant marine walk-on panels are extremely flat shape with high stability.
www.emarineinc.com www.emarineinc.com
These crapped out in a few years and were doing diddly. (traces jumped on the back and bubbled on the face, no warranty viable with the cust service run around) So I would like to use BASIC panels.

The nominal voltage seems to be 48V for most panels these days yes?
 
flatwater said:
The nominal voltage seems to be 48V for most panels these days yes?
Click to expand...
Generally 30-40 Vmp. So yeah, you are screwed like all of us to use panels in series or boost MPPT.
yabert

Thread 'High voltage solar panel (60-70Vmp)'

Hi

I'm looking to charge a 16S LFP battery on a sailboat.
As shade can be important, I would like to have four 400-500W panel in parallel to one or two Victron MPPT.
The ideal situation is to have each of the solar panel with an output Vmp around 60-65V.
I only find 54 cells panel (around 31Vmp) or 66 cells (around 35Vmp) or 72 cells (around 41Vmp).
Is there 110-120 cells solar panels with a Vmp around 60-65V?
Thanks
O

Thread 'how to do solar on a sailboat that has limited space and shading issues @48vnom'

I wish to put PV on my sail boat. My Boat/inverter system is 48v (Victron). Because space is very limited on a sail boat I can only manage a total of 4 panels with possibly 2 extra down each side mounted vertically - so if did that it would be 8 panels in total - (but not sure if that is a good idea or not to side mount like that - some do it, others say avoid it).

The issue is I dont want to run the string in series due to shading issues (boom/mast/rigging wires/sails when under way). Parallel is not much use to me in this scenario as I need to get the voltage at least 5v above battery...
 
flatwater said:
amperage getting too high (BMS and genset) have gotten me back looking at 72V (and 96V).
Click to expand...
If you go away from 48V stuff, that can be challenging to find ''regular'' component like inverter, MPPT, DC/DC, etc.
In my case, I plan to go on the edge of regular 48V component with a battery around 60V.
Some 48V component can be use up to 66V or 67V... after it's an entire different category.
 
INNteresting workup on the 60V battery. I like that. Is that to provide a buffer for voltage drop or to increase your available rpms? Or to decrease amps a bit? Or all 3?
 
flatwater said:
a buffer for voltage drop or to increase your available rpms? Or to decrease amps a bit? Or all 3?
Click to expand...
In my case, I don't expect any voltage drop when pulling 10-20 kW from a 140-160 kWh battery ;)
It's mainly for rpm and amps. There is 25% gain from 48V to 60V.
Most available motors have limited continuous amps in the area of 100-200A and it's why I will go 60V.

Sadly, the perfect motor who run 500A continuous at 48V while outputting 1000 rpm don't exist (or not easily accessible).
Almost every motor available are higher voltage, higher rpm and lower amps 😐
 
Last edited:
I routinely use the genasun boost chargers.

The maximum battery bank voltage that they can feed is nominal 48 volt. ( so charging up to ~ 56 - 58 volts )

They are designed for situations where the input voltage is usually below 40 volts, but can occasionally go higher for moderate amounts of time.

I mount them on a piece of aluminum to help spread any heat, even though that is not required in their spec, and it helps with longevity.

Under those conditions, they work very well.
 
Thanks guys,

the midnite solar classic, it cant boost the lower voltage panels up to a 72vdc bank though right?

also darn, i thought that those genasun units could go up to 72+ for battery bank charging. I really may be in the weeds here if i cant boost around 40vdc string output up to 84vdc for charging
 
How about this?
www.eco-worthy.com

24V/36V/48V/60V/72V Boost 12A MPPT Solar Charge Controller Regulator | ECO-WORTHY

Charging 24V/36V/48V/60V/72V batteries Input Voltage: DC 13-50V Input Power: 450W Working Current: 12A Output Voltage: 24V/36V/48V/60V/72V Battery Type: Lead-acid/Lithium/GEL/Flooded Working Temperature: -20℃~60℃(-4℉~140℉) Size: 134*87*47mm (5.3*3.4*1.8 inch) Weight：375g (0.83 lbs)
www.eco-worthy.com www.eco-worthy.com

Says it can charge a 72v battery. But depending on how many panels you have, you might need to double up these MPPT chargers, because they are limited in wattage.
 
Look on electriccarparts.com website - they have mppt solar charge controllers for 72v, 96v & 144v. And battery chargers for those banks as well.

I have thought about an electric drive boat with elco’s motors - thus 96v or 144v DC…

But first I gotta buy a boat.
 
flatwater said:
I may try that 60V setup myself as well.
Click to expand...
I just start to play with Victron MPPT. There is absolutely no indication anywhere, but I know now they can be adjust up to 69V.
So, 20S LFP can be charge up to 3.45V/cell, who is excellent and then if inverter can take 67-68V at full charge, you can run a 64V nominal battery with regular 48V stuff.
 
yabert said:
I just start to play with Victron MPPT. There is absolutely no indication anywhere, but I know now they can be adjust up to 69V.
So, 20S LFP can be charge up to 3.45V/cell, who is excellent and then if inverter can take 67-68V at full charge, you can run a 64V nominal battery with regular 48V stuff.
Click to expand...
In an all Victron power system (sp. mppt/dc to dc / MPII/Cerbo) is a 60vnom system going to work? The danger is charging cells all the way up to 3.65v - what happens then (20 x 3.65 = 73v) ?

Is an 18s setup a bit safer? ie, still get into the 60ish volts area but not going above 66v (18 x 3.65 = 65.7v / 18 x 3.45 = 62.1v / 18 x 3.0 = 54)

I have had this very thought several times but given up as its pushing the boundaries of safety in terms of volts for the equipment, but if it can be made to work then it is an interesting concept - as you say, getting those volts up gets those amps down.
 
Ohms_Cousin said:
The danger is charging cells all the way up to 3.65v - what happens then (20 x 3.65 = 73v) ?
Click to expand...
Who will charge the cells up to 73V? The charger? It simply have to been correctly programmed.
The MPPT? It simply have to been correctly programmed.
Still overcharging? What is the job of the BMS? It should been able to close the charger/stop the charge.
Anyhow, 18S LFP is a lot safer as you explain.
 
yes the charge source *Should* never charge over 3.45v. However seeing as how Murphy is my next door neighbor and I am an unlucky guy, I wouldnt like to trust that. If and its a very BIG IF, the charger does let the volts go over 3.45 then ..."pop" goes your expensive blue parts.
 
Ohms_Cousin said:
IF, the charger does let the volts go over 3.45 then ..."pop" goes your expensive blue parts.
Click to expand...
Yeap! But it's not like if stuff work at 67V and explode at 70V.
It would be interesting for sure to know the maximal voltage before failure.
Sure 18S LFP is way more secure. Or 16S NMC like I plan to do. So around 58V nominal.
 
yabert said:
Yeap! But it's not like if stuff work at 67V and explode at 70V.
It would be interesting for sure to know the maximal voltage before failure.
Sure 18S LFP is way more secure. Or 16S NMC like I plan to do. So around 58V nominal.
Click to expand...
NMC - brave man or probably more like it, a man with a risk appetite. I would not put NMC in my boat, but each to thier own.
 
yabert said:
Yeap! But it's not like if stuff work at 67V and explode at 70V.
It would be interesting for sure to know the maximal voltage before failure.
Sure 18S LFP is way more secure. Or 16S NMC like I plan to do. So around 58V nominal.
Click to expand...
I am not an electrician, hence here learning as much as I can so I can build *safe* batteries. My understanding is that the equipment can take a solid supply of amps but if voltage goes over its limit of say, 66v, then it instantly blows the equipment. Please correct me if I have understood that wrong - how voltage sensitive are the blue inverters?
 
I guess one possibility is to use solar to charge a lower voltage battery and then either:
- Find a DC - DC boost converter / charger
- Use an inverter on the lower voltage pack - ( 120 vac ) -- ( 120 vac battery charger ) ---- higher voltage pack.

It is a bit brute force but I have seen it done and used it myself in some situations.
 
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