2nd LiPo Battery for GL39

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Feb 25, 2024
Vessel Make
GL 39 Hybrid
Hello all GL owners. It's great to have this forum and thanks a lot to all those contributors.

We have recently ordered the delivery of a new GL 39 Hybrid to Portoroz Slovenia, due early July 2024. We did consider the offer of a vessel which was almost complete, however some of the options did not suit us. One option the previous purchaser did agree was the factory fitting of a second LiPo battery, I'm presuming effectively giving double the cruising range, say 40 nautical miles.

I understand that a second battery can be retrofitted if at some point it's deemed advantageous, however we're tempted to bite the bullet and spec a second battery from the get go. I s'pose an issue is charging time when at port. Are users familiar with charging time of the LiPo batteries? Can I assume that on any typical day arriving and connecting power at a Mediterranean marina mid-afternoon, with drive batteries low, that both will be fully charged come say 9am the next day?
Not a GL39 owner but your question requires a few specifics to know the answer. First I would think the charging specs should be readily available for a new/newer boat? But if not pretty easy to calculate. You just need to know the amp hour capacity of the battery and the max charging rate of the charger. So if 1,000 AH battery with a 100 AH charger it would take approximately 10 hours. Most LiPo batteries can accept a charge rate up to 1x the capacity but to be more conservative it could be 0.5 x capacity. So a 1000 AH battery could possibly accept a charge rate of 500Ah per hour of charging. That is a pretty large charger!
Here is what I found on the GL website. Based upon this I would guess if it has only 320Ah batteries they could be filled from empty in 3-4 hours of charging. It comes with a Victron 3KV charger which I believe can output about 120 Amps per hour at 12 volt. So divide 320 AH capacity by 120 AH charge rate and you get about 3 hours required charging time. So no problem to top it off overnight.
Sorry here is what GL says:

4 x photovoltaic panels total
1.320 Wp.
Two voltage systems: 12V
and 230V 50Hz
All systems are insulated with
2 main switches + parallel
230Vac panel and fuses
12Vdc panel and fuses
Automatic charger/inverter,
12V / 120A / 2400W / 3000
Shore power pick-up 16A
230Vac sockets in the galley,
saloon, owner’s cabin, guest
cabin and in the washroom.
Battery charge managing
Reverse cycle air conditioning
16.000 BTU (only 220V)
Engine start battery
Service battery bank:
LiFePO4 2 x 160Ah (12.8V)
Steering magnetic compass
with light
LED Navigation lights
Anchor light
Batteries for bow
thruster/anchor windlass
Thanks Ken for the quick response. The 2*160 Ah (320 Ah) batteries are the service batteries. The hybrid drive battery I'm considering doubling up is a 56V 13.3 kWh LiPo battery. The spec states the automatic charger/inverter is 56V / 5000 VA / 70A. Any additional advice welcomed. Kind regards, Gordon
Thanks. So 13,300 kwh/56v is 237.5 Amp hours. If the charger is 70 Amps (@56v) you would divide 237.5Ah by 70 to get about 3.5 hours of charging required.

It is late night and I am doing it mostly in my head but I think it is approximately correct.
Congrats on your new GL!

For what it's worth, we have a 240 Ah 48v (11.5 kWh) battery on our 2010 GL33.

For the life of the boat, thus far, we typically arrive at a marina in the evening, plug in (230v 16Amp shore power) and the battery, if nearly depleted, will typically charge in 8 hours or less from "average-strength" shore power. If shore power is weak (i.e. you can pull only 5 or 6 amps instead of 8), charging could take 10 hours. This is with a Victron MultiPlus 35Amp Charger/Inverter.

I have often lusted after a second battery to extend range on electric. To date, I have not added one. What gives me pause are the following:
- extra space consumed
- extra weight
- likely need for a new or second Victron multi charger
- likely need to hook-in the new battery to the solar system as well
- likely that my power entrance would have to go from 16Amp to 32 Amp, meaning different plug and cable. Or maybe a second 16 Amp entrance would be needed?
- I love having the hybrid system act as UPS (uninterruptible power supply) and I'm not sure how this would need to be re-configured(?) if adding a second battery.

What I'm getting to is that, if I were in your shoes and wanting to maximize my range on electric, I would ABSOLUTELY spec the second battery now so the boat can be delivered from the factory all set up and configured correctly. I would not want to be messing around "experimenting" with LiPo battery setup/config for a DIY add on. Ordering it from the factory will mean the whole setup is under factory warranty and there will be no questions about it should you ever need to make an insurance claim.

Edit: And to more directly answer your original question...
We find that the most we can typically draw for charging from a 16 amp shore power connection without tripping the shore power breaker is 8-10 amps. So what takes me 6-10 hours over night could take twice that with two batteries, unless you can find 32Amp shore power connections in your cruising area. OR...if you have a setup where you can use TWO 16Amp shore power lines to different posts at the marina. Not sure how the factory might deliver such a solution (i.e. one 32A or two 16A?), so you might want to ask in case you have a choice.

Edit2: Electric boat/fast-chargers are starting to pop up here and there. Availability of such chargers would, of course change all my thinking and comments above - but it is my opinion that fast chargers at marinas are not plentiful enough yet to design a system that assumes their existence everywhere you may want to go. Further to that, Lithium-anything batteries prefer slower charging to fast charging. Slower charging, when convenient for you, will extend the life of the battery.
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Thanks guys. Extremely helpful. Based on your responses we'll almost certainly be spec'ing two drive batteries. I'm also a yachtie and therefore never in a hurry to get anywhere, so gentle cruising on battery power from port to port is a real attraction, and I have the diesel for the occasional longer transit, and back up, much the same as how we use our PHEV.
Definitely add battery #2

We own a 2019 Greenline 39 Hybrid. We purchased it as a demo boat that had a long list of options except a second battery. If I were specifying the boat new I would definitely add the second battery, however, for a slightly different reason than extended range. We rarely cruise on electric. We use it to go in an out of marinas, docking. etc. However, we use the battery capacity while on a mooring or at anchor. A single battery will allow you to over night with AC but you’ll need to recharge pretty early the next day. The good news is that if you use the diesel at cruising speeds it will recharge your battery in 1-2 hours from a relative low 40-50% charge. It will likely charge it faster than shore power. (This is only when you are underway.) GL39’s have a single 30AMP shore power connector. Your charging rate will be much lower than that because you also need the buffer for current usage and any spikes that would trip the breaker. Also with two batteries, you’ll be able to stay in a relatively higher state of charge to not stress your batteries. While it isn’t cheap, I would definitely add the second battery.
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Regarding time to charge, check the battery specifications on the recommended charge rate. The LiFePo batteries I have looked at had recommended charge rates of .5C but could charge up to 1C, or maybe higher. I would want the battery charging system to charge at the recommended rate or less.

The recommended charge rate is another limitation on how long it will take to recharge the battery.

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