View Full Version : CCA ? Part2 - Reason for more info.
March 10th, 2008, 6:41 PDT
The reason I'm looking for CCA is the manual that came
w/my PROwatt 1750 inverter says to determine the total
CCA rating of my batteries. If the CCA is 650 or less i need
to install an ANL 250 fuse between the batt + term and the
inverter. If total CCA is over 650 i need a different type
of fuse. I plan on adding more batteries later, so therefore
i need to be able to calculate the total CCA to see what size
and type fuse is needed. These fuses can be quite pricey,
so i want to install one that can handle four 6V batts with-
out going to a $50 or more fuse setup.
March 10th, 2008, 7:42 PDT
now that's one that i never heard of before. if it were me i'd pick the smaller of the 2 fuse choices and even at that that would equate to a 3000w draw. inverters are capable of short duration surges, but as the numbers imply it will not consistantly deliver at over 1750w. at 1750w and 12v that is a constant current of 145.83 amps. i wouldn't fuse it at the 150a point even though you could unduly limit the inverter to that, but even allowing for some surges you could get away with a 200a fuse if it is handy or cheaper to use. 12vx200a=2400w surge before it blows. if you do have equipment with large surges exceeding 2400w then go for the 250a fuse. also know that circuit breakers are also a good option to fuses if they are dc rated.
March 10th, 2008, 8:12 PDT
An addition to Neils comments please make sure you use the correct size wiring , the fuse is there to protect the wiring not the inverter. Too high a fuse with insufficient sized wire spells trouble :cry:
March 10th, 2008, 9:28 PDT
OK… I think I see what’s going on here. In short, a 250 A ANL fuse with the right AIC spec should work for you.
The 250 A fuse rating looks OK to me. Assuming full power (1750 W), minimum battery operating voltage (10.0 V), and the low end of Xantrex’ efficiency range spec (85%), the inverter will draw 1750 W / (10 V x 85%) = 206 A from the battery bank. Applying the typical 80% derating factor (or 125% multiplier), the fuse should be rated at 206 A / 80% = 258 A. A fuse rated at 250 A is probably “close enough”.
I suspect that Xantrex’ discussion about CCA specs and fuse AIC is derived from ABYC standards. The basic issue is that the fuse (or circuit breaker) must not only be able to open at its nominal rating, but it must do under extreme current conditions and open wide enough (fuse) or nor suffer internal damage (fuse block or inside of DC breaker) so that the device remains “open”. Blue Seas and Home Power magazine have further discussions on this issue.
See: http://bluesea.com/viewresource/98 (http://bluesea.com/viewresource/98)
and: http://www.homepower.com/article/?file=HP101_pg128_Letters_3 (http://www.homepower.com/article/?file=HP101_pg128_Letters_3)
So, what’s your proposed battery bank’s CCA? I agree that such specs for golf cart batteries appear to be impossible to find. But, we might be able to develop a reasonable cross-reference.
Specifically, the Trojan SCS200 deep cycle battery is rated for 12 V x 115 Ah. Its CCA spec is 620. A pair of these batteries wired in parallel would be rated at 12 V x 230 Ah, with a combined CCA spec of 1240.
A series-pair of Trojan T-105’s are rated for 12 V x 225 Ah – pretty close to the parallel-pair of SCS 200’s described above. So, let’s assume the series-pair of T-105’s would also have a CCA spec of ~1240. Continuing on with this model, a series-parallel combination of four T-105’s (12 V x 450 Ah) might have a CCA spec of ~2480.
The ABYC table in Xantrex’ manual indicates that a fuse (and fuse block) rated at 5000 AIC is required for a battery bank of this specification. Blue Seas’ ANL fuses and fuse block are rated at 6000 AIC, so they should do the trick for you.
See: http://bluesea.com/category/5/22/productline/overview/135 (http://bluesea.com/category/5/22/productline/overview/135)
And: http://bluesea.com/category/5/21/productline/129 (http://bluesea.com/category/5/21/productline/129)
Finally, Nigel’s recommendation to use heavy cable is well founded. The manual recommends 1 AWG cable for runs up to five feet, which is pretty short. 2/0 would probably be a better choice, and the Blue Seas fuse block can handle cable and lugs of that size.
Very good pre-made flexible cables are available here: http://www.solarpanelstore.com/solar-power.wire.html (http://www.solarpanelstore.com/solar-power.wire.html)
Jim / crewzer
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