Re: [Electric Boats] Chevy volt battery pack in a boat

From a risk mitigation standpoint, a BMS that can isolate the pack through relays/contactors is absolutely essential.
Don't charge the pack when you're not present until you are very sure that everything works ok, and the BMS can cut the charger.
Get a charger like a PFC2500 (or bigger) and talk to the manufacturer about your exact use case. They program the charger with a charge profile customized to your battery pack. If you are nervous about the cells' upper limits, then they can set the charge-full cutoff value to a limit that makes you comfortable.

Talk to some vendors, They are knowledgeable and very helpful, EVEN if you aren't an immediate customer.

You may want to consider a higher end BMS that reports/tracks per-cell voltage, internal resistance etc.
Lithiums are really touchy about their voltage limits. You really don't want to be trying to eek out each last possible amp-hour by charging the cells right up to the high voltage mark.
The voltage rises very quickly in the last couple of percent charge. There is really not a lot of energy under that part of the curve, so don't go chasing after it.
So set your BMS low- and high-voltage cutoffs to conservative values.
When you sail, try to keep the pack above 20% charge.
How many amps can these cells push? These 48V/45ah packs are going to be able to handle the 1C and 2C loads, but if your setup can sink 500A then those cells may be asked to produce it.
A single 45ah pack would be seeing over 10C draw at that point. Are the cells and battery tabs and everything else the electrons move along rated for that much current?
I know you are looking to parallel a couple of packs so that improves things for each pack. The same 500A load would be spread across 4 or more packs, bringing the load down to a more reasonable 125A or about 3C discharge rate on each Chevy Volt pack.


Ok, enough rambling. I am racing tomorrow and am going to bed.

Cheers,


/Jason




On Aug 28, 2015, at 7:57 PM, Anton antonherbert@earthlink.net [electricboats] wrote:

>
>
> Thank you for that Jason, it was useful information for wrapping my head around sizing the pack for my boat.
>
> Can anyone speak to the fire risk of these Chevy volt batteries?
> I believe they are lithium magnesium. (Different from cobalt?) Are these significantly more dangerous then the liFePO? Are there fire extinguishers that would put out such a fire? Could you put them in a fire proof box? (So much for the weight saving!)
>
> Any thoughts on the risks or strategies to mitigate the risks would be helpful.
>
> Thank you!
> Anton
>
>
>
>
>
> On Aug 28, 2015, at 6:13 AM, Jason Taylor jt.yahoo@jtaylor.ca [electricboats] <electricboats@yahoogroups.com> wrote:
>
>>
>>
>> I have a "1 hour" battery pack. That means my 5kw system, in my 4 ton boat has a 5kwh pack. I find it sufficient for club racing and day sailing in my river/lake with a 1kt current. And not much more. You may want to consider a single pack for testing and moving the boat about the marina, but for venturing further than a few (under 5) miles, you'll definitely want to have at least a 4-pack of those batteries.
>>
>> The general consensus for a standard install is 1kw/ton for motor power and about 2kwh/ton for battery storage. So being a 10ton boat, you would want at least a 10kw motor -- the AC35@48V & 500A can develop up to 25Kw so you're good there. But if you want any kind of range, you're going to want at least a 10kwh battery pack (5 of the Chevy Volt packs you mention), but a 20kwh pack may give you a better operational envelope. The Westsail 32 is a heavy displacement, sturdy boat that c an handle some really rough conditions. Your motor seems well-sized to power it. But only 4 Chevy Volt packs may not provide the boat the energy storage capacity it would need to perform under those conditions.
>>
>> I am also interested in learning more about these packs. That seems like a very good price.
>>
>> /Jason
>>
>>
>>
>> On Aug 27, 2015, at 16:31, Anton antonherbert@earthlink.net [electricboats] <electricboats@yahoogroups.com> wrote:
>>
>>>
>>>
>>> I am considering the Chevy volt batteries in my conversion.
>>> The guy in Livermore who is selling them assures me that the water ducts are not for cooling but for heating the battery in cold climates.
>>> $550 for 48v @ 45 amp hour plus $200 for the bms. I am thinking of getting 3 or 4 to start with. My system is the thunderstruck ac35 on a Westsail 32 (full keel 10 ton sailboat)
>>> Any thoughts? Concerns? Advice?
>>> Thank you
>>> Anton Herbert
>>>
>>>
>>>
>>>
>>> On Aug 10, 2015, at 10:48 AM, mark.internet@yahoo.ca [electricboats] <electricboats@yahoogroups.com> wrote:
>>>
>>>>
>>>> Has anyone tried a chevy volt battery pack in a boat.
>>>> They appear to be reasonably priced for the AH's.
>>>> It looks like they have 48 volt and 24Volt modules.
>>>> They are water cooled and maybe one could add a pump and run lake water through them for cooling.
>>>>
>>>> if someone has used one please let us know how it works
>>>>
>>>> Thanks
>>>>
>>>>
>>>>
>>>>
>>>
>>
>
>



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