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Old 19-12-2012, 13:15   #766
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Ummm, the last time I checked, NMEA 2000 was CAN bus based, and it seems to be in quite widespread use on boats ;-) Volvo Penta seem to be providing CAN interfaces on their engines...

In the context of this thread, some smart chargers already have CAN bus interface too.
Would be very useful for setting up with Vitron/Mastervolt chargers controllers/battery monitors.
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Old 19-12-2012, 15:39   #767
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

And the $3450 does include the BMS, a system that provides alarms and controls during charging and discharging and balances the individual cells during charging. The BMS output is CAN bus based because the BMS was developed for electric vehicles. And, yes, NMEA is CAN bus based but with attitude.
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Old 19-12-2012, 17:27   #768
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

And a BMS handling a 700+Ah battery needs to be able to open an LVD contactor possibly carrying 1000A or more---without burning up. No small feat.

A full BMS would be overkill for my much smaller 160Ah RV battery, but I'll still want an LVD. Even 100A contactors are pretty darn pricey. So I'm looking into what is called a Shunt Trip circuit breaker. These are like ordinary circuit breakers, except they have an additional pair of small terminals for the "shunt". Briefly apply 12V to these terminals, and the breaker will act as if it were tripped---opening the circuit until it is manually reset.
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Old 19-12-2012, 18:48   #769
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Quote:
Originally Posted by diugo
And a BMS handling a 700+Ah battery needs to be able to open an LVD contactor possibly carrying 1000A or more---without burning up. No small feat.

A full BMS would be overkill for my much smaller 160Ah RV battery, but I'll still want an LVD. Even 100A contactors are pretty darn pricey. So I'm looking into what is called a Shunt Trip circuit breaker. These are like ordinary circuit breakers, except they have an additional pair of small terminals for the "shunt". Briefly apply 12V to these terminals, and the breaker will act as if it were tripped---opening the circuit until it is manually reset.
Have you got devices carrying 1000A. !! Or are you mixing up interrupt capacity. Surely you have fuses for large over currents ??

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Old 19-12-2012, 19:01   #770
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Have you got devices carrying 1000A. !! Or are you mixing up interrupt capacity. Surely you have fuses for large over currents ??
I'm just saying that most LFPs are rated to carry 3C, which is 2100A of continuous current for a 700Ah battery. That may be a mindboggling current for RVs and maybe for most boats, but electric vehicles apparently have been known to demand it from time to time.

So the contactor or breaker connected to the BMS should be able to disconnect that amount of a current under a low voltage condition. Otherwise the BMS would not be doing its job, IMHO.
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Old 19-12-2012, 19:51   #771
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Maybe if your drag racing those EVs like the White zombie. The largest controller for us "roll your own" EVs is the Zilla 2K, 2000 amp at 300 volts. 600,000 watts or 800 hp.
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Old 19-12-2012, 22:14   #772
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Actually the Tyco EV500 contactor has these properties:

Quote:
Very high power sealed contactor
Hydrogen dielectric for power switching high
current loads
Excellent for safety disconnect and transfer
switch applications
Ideal for circuit protection control
Hermetically "super-sealed" environment
uniquely protects contacts and all moving
parts; can operate in harsh environments
600-1000A continuous carry, dependent on
temperature and conductors used
3,300 A interrupt, 1,000 A make, @320 Vdc
12 and 24 volt coil control options. Call
factory for custom options
360 kW power switch capable
200oC hot power terminals capable
Bi-directional power switching
Auxiliary contacts optional
Built-in dual power coil economizer
8W holding typical
Versatile power, voltage, and current
operating range 320-1800Vdc
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Old 19-12-2012, 22:17   #773
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

...and the 3C or 5C spec for LFP batteries is generally for <15 seconds duration. Hardly the operating region that we should be designing for, IMHO.
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Old 19-12-2012, 23:37   #774
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A li-ion or li-phosphate battery requires a different charging pattern than a lead acid battery even if the nominal voltage is the same.

Use a lead acid designed charger on a li ion battery and you will likely cause heavy damage to the battery and maybe to your boat.
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Old 20-12-2012, 01:07   #775
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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...and the 3C or 5C spec for LFP batteries is generally for <15 seconds duration. Hardly the operating region that we should be designing for, IMHO.
Exactly! I would design to the maximum capacity of the input sources and the consumers. The 3C spec is then useful to set a minimum safe battery bank size. A reasonably useful battery bank will be much larger than that anyway.

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Use a lead acid designed charger on a li ion battery and you will likely cause heavy damage to the battery and maybe to your boat.
I don't think anyone here is planning to install lithium cobalt batteries on a boat, which would be damaged by a lead acid battery charger. I don't believe that charging lithium phosphate batteries with a suitably voltage configured lead acid battery charger would cause any serious damage, though it might be sub-optimal.
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Old 20-12-2012, 07:03   #776
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I guess you need to ask yourself, under what conditions would an LVD most likely need to be employed---light load, or heavy load?

The EV500 will open under 2000 amperes---once---and in that sense, it may be good enough; better to sacrifice a $100 contactor than the battery bank. But 8 watts is a lot of wasted power: nearly six kiliowatt hours a month.
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Old 20-12-2012, 07:07   #777
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

The breaker only needs to be rated for the max expected power of the load, not the source, Thats the job of a fuse. Other wise the breakers in my house would be about 10 mega amps!

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Old 20-12-2012, 07:32   #778
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

#776
Quote:
The EV500 will open under 2000 amperes---once---and in that sense, it may be good enough; better to sacrifice a $100 contactor than the battery bank.
I see no normal electrical load on a <100' vessel, house or propulsion, that would require 2,000ADC (24kW @ 12VDC; 48kW @ 24VDC; etc.)

Quote:
But 8 watts is a lot of wasted power: nearly six kiliowatt hours a month.
Under normal operating conditions, the LVD contactor is protecting a very expensive battery bank from a LVE and will be triggered only if the operator has ignored the warnings that the BMS has been providing announcing the pending arrival at the dreaded discharge "knee" . Therefore, as a designer, I do not view the 8W as "wasted power" but simply another design parameter that must be accounted for in the overall system design approach.

#777
Dave-In fact the overcurrent protection device (OCPD), fuse or circuit breaker, has an ampere interrupt capacity (AIC) rating that is based on the short circuit current of the source.

The AIC is the maximum current that can be:
> interrupted by a circuit breaker that will leave the circuit breaker functional or
> interrupted by a fuse with the fuse and fuse holder remaining physically intact; i.e., not blown to bits!

With the increasing size of house batteries (1,000Ahr is no longer a large house bank!), the re-emergance of electric propulsion, and the very high short circuit capacity of AGM and LFP batteries, providing well thought out ABYC Standards and finding reasonably priced OCPD with a suitable AIC are very real issues.
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Old 20-12-2012, 07:41   #779
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Under normal operating conditions, the LVD contactor is protecting a very expensive battery bank... Therefore, as a designer, I do not view the 8W as "wasted power" but simply another design parameter that must be accounted for in the overall system design approach.
It is wasted power, because a shunt trip circuit breaker draws zero power in comparison.
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Old 20-12-2012, 07:45   #780
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

OK. Your opinion; my opinion.
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