Reply With QuoteThanks Tim, PM sent
OldBushie
Hi again Mitch, only use the CCA rating of a battery. It is based on a well established standard.Originally Posted by Toxic_Avenger
I guess it all comes down to what amp draw an 'average' starter motor draws? Or if we are wheeling with others, what their starting amperage might be. 600CCA batteries are normal, however their hot cranking amps are much higher.
Also, the CCA of a battery is used by the manufacturer to relate the specific cranking capacity of a battery needed to start their given motor but it is NOT an indication of the amps required to turn the motor over.
You actually need both the minimum amps and the minimum voltage to be able to determine what minimum CCA battery size you need.
The amps will always be a MUCH low rate than the CCA needed to meet those requirements.
I am going to go into this in more detail on one of the other threads, when I get the time. Sorry.
Fossicker
SupporterThanks Tim, PM sent
TopicToaster
SubscriberSo we've worked out that a 50A anderson plug and a 50A automotive circuit breaker would be fine for the OP's purpose of running an air compressor and the occasional jump start, with the anderson plug being a common power connection for a variety of accessories.
similar but different...
I'm working on my dual battery setup.
I've got 2x optima D34M batteries @ 55Ah each. If I were to have a new battery setup as a removable 'deep cycle' setup (think like an ark pack sort of arrangement), what rating anderson plug would be needed to join this battery to the existing hard wired setup?
Are there concerns with inrush current when joining different Ah rated lead acid batteries, or batteries of different states of charge?
I'm also expecting a charging current when this battery is connected and under charge.
Thoughts / opinions? 50A? 175A? Something completely different?
-Mitch
'El Burro' 2012 Defender 90.
I ran a third D34 in my trailer via (an appropriately protected) 50a Anderson plug with no dramas at all.
Fossicker
The fuse on a circuit is used to protect the cable, not the device. So set your fuse or breaker to whatever 16mm2 can handle. 16mm2 can handle over 100 amps AC, not sure about DC.
The air compressor and such have built in circuit protection inside the unit (generally)
RoverLord
umm, not quite.
because we're working in the low voltage world you should fuse at the current you want to be drawing at. This is becasue sometimes due to the low voltage and the significance of the votage drop oversized cables will be used.
fusing a cable capable of handling 100A at 100A is a bad plan if you get something drop into the socket or a chafe through you can easily deliver enough power into a conductive enough "short" to start an electical fire.
Dave
"In a Landrover the other vehicle is your crumple zone."
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TopicToaster
SubscriberSo fusing aside...
Will a 50A anderson plug be sufficient for joining batteries given charging current, normal usage, and any incidental issues when connecting a flat battery to the full bank?
Or should I just be safe with a 120A or 175A plug?
-Mitch
'El Burro' 2012 Defender 90.
A Keeper of the TGO
I can't see why you need go for anything bigger than 50A.
Most of us use the 50A plugs for connecting to camper/caravans.
They are nothing more than a mobile battery pack with lights attached
Fossicker
This is why you derate the cable prior to selecting the breaker or fuse. And a bigger CSA on any cable will ensure more current hense the fuse will blow quicker?
Not arguing but this is the way i have been taught as an electrician
TopicToaster
SubscriberI understand where you're coming from. In layman's terms make sure your fuse blows before the cable melts. Assuming the CSA of the cable is not the limiting factor, fuse blow is relative to the type of fuse being used though- different blow profiles with different fuse designs etc.
I'm not sure though how much current a battery is likely to see in normal operation though... or in a 'worst case scenario'.
By the time my plan is executed, there will be 3 batteries, in parallel, with charging managed by charging relays with low voltage cutout. Loads will be isolated from the starting battery either by being locked out manually, or managed by the charging relay, so average loads are shared amongst the 3 batteries, or 2 at worst. So a 100A draw will be 33A between the 3 batteries, or 50A on each respectively.
Also not sure what output the D90 alternator is these days... but my understanding the alternator generates voltage to charge the batteries, but will not create its full current output unless it is justified by the draw on the system, or is charging a very flat bank of batteries.
PS I'm not an electrician, so don't be surprised if some of this makes no sense, electrically!
-Mitch
'El Burro' 2012 Defender 90.
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