lithium ion battery charging

[georgeo]

I am looking for some design help for my sailboat. The boat has an electric motor with a lithium ion battery pack. For the last few seasons my battery charging has been strictly shore power but would like to add a little bit of solar power to help extend my cruising range.

I am not looking for free advice, but rather to find someone experienced who can spend a few hours and charge me for the design help. If you are interested let me know with a reply and the best way to connect with you.

Here are the details:

Midnite Solar Classic 150-  already purchased and installed in the electrical cabinet, but never used
Wires from future solar panel mounting location on the boat have been run to the Classic 150
Battery pack:  (20) CALB 180AH LiFePO4 cells in series-  nominal voltage 20 x 3.2 = 64V
when on shore power we charge at about 70 to 71 volts at 15 amps
Battery Management System (BMS)-  Orion
The Orion BMS uses Canbus to control the shore power charger. It also has other communication and control ports.

So the above is all existing, installed and in use (except the Classic 150 has not been used).

I have room for maybe two rigid solar panels in series. I would prefer a single panel but understand I cannot get a single panel with sufficient voltage to charge my batteries. And no one makes a boost controller in this range that I know of.
I don't really need a lot of charging. I am happy with the shore power, but if I could get 500 watt-hours in a day I would replace what the boat uses for house loads.  For all requirements, house loads and motoring, I typically use 1400 watt hours in a day. This gives me the capability to cruise maybe 6 to 7 days without any recharge. So with a decent solar setup I'd like to get a few more days endurance.

The sailboat is on Lake Superior- not your prime solar harvesting area!

Of great importance is the ability of the BMS to shut down charging based on individual cell voltage.It does this with my shore power charging and I must also be able to stop solar charging via a BMS signal. Also, when I am not at the boat I shut everything down- no loads, no shore power and no solar. I simply don't trust unattended high energy in this situation and it really is not at all an inconvenience. I simply plan my charging time when I am at the boat.

Specifically, what I need is:
what solar panels to buy
how to configure the Classic 150
how to tie in the Orion BMS
and, to find out if maybe my thinking is all wrong here or I am missing some key item.
Possibly, I could fight my way through this myself, but I really don't want to bang my head against the wall when perhaps someone experienced can do the design correctly the first time.

Thanks!

George O.

[Westbranch]

Welcome George,  first question, why and how are you using the power from those 64V batteries?

Next, you need ~ 18A, 10% of battery rate,  input for a good charge rate for the batteries  if they were FLA....

As LiFePo4 batteries can apparently work well within the range of 20% to 80% SoC, without harm,   you should compare that with the experienced loads you list in order to determine how much PV input you need, minimum, optimum and maximum.    It's a matter of what you need, want  and what you can live with in a pinch, like days of autonomy, the norm is 3 .

hope this helps.

[ClassicCrazy]

There are some lithium users who advocate bottom balancing lithium batteries. You drain them out just about empty, then only fill them up to about 80% and use the ending amps with the whiz bang to terminate the absorb charge at the correct point. So you never get to the top voltage area where you have to worry about going over voltage. Since you already have the BMS system then you would have extra protection in case something messed up happened. 
Do a search on the forums here for lithium batteries and you will find some good discussions.

You can dump a lot of power into the lithium pack compared to lead acid  so get as much solar as you can manage . I don't feel qualified to advise on marine setups but I guess if you aren't dealing with salt water it isn't too much different than regular setup.  There is a Midnite String calculator where you can plug in some numbers from solar panels to get an idea of what you will need. 
http://www.midnitesolar.com/sizingTool/displaySizing.php
I am not familiar with  panels on the market with a high enough voltage so that two in series would be enough to charge your 60v battery pack.
Vic was just discussing battery voltage needed for batteries in this thread
http://kb1uas.com/mnsforum/index.php?topic=3438.new#new

Larry

[tecnodave]

Georgeo,

Most solar panel are 60 cell "grid tie" types and you would need 3 in series to get high enough voltage but there are panels available that have a higher cell count and have higher voltage in the one panel.

I just bought a pallet of 96 cell panels that are about 52 volts at MPP , I've seen 128 and 144 cell panels as well.

Just throwing this out there.......it would be easier on a moving vessel to use the higher voltage panels as fewer in series would be needed to get the needed voltage

Dave

[georgeo]

Thanks for the replies here.
Technodave- I would be very interested in knowing the specifics on the 96 cell panels you bought and also where you have seen 128 and 144 cell panels. I simply haven't been able to find any, but being totally new to solar I suppose I don't know where to look.

Westbranch- my batteries are for propulsion power for my electric motor and also house loads (lights, radio, fridge). The motor uses the full voltage; I have DC-DC converters to 12V and 24V for the house loads. All my power comes from the batteries and the solar panels are simply to put a little energy into the battery pack in order to extend my range a bit between AC shore power charging.

ClassicCrazy- I will do some research on this forum regarding lithium charging.

George

[CDN-VT]

Im with T-dave & high cells panel & sailboat is the WORST boat , I have one , with a 2 shade trees ..

Now without major math , solar over shore power , solar might increase 20mins / day or take 2 days to charge 100% under sail
off shore ..

Boats are a Major pain in where to mount & not get blown away . walked on , no shadows , & an area to mount .
Im 76 feet & still a pain .

VT