Dual Battery Setups! Let's see them! Multiple Batteries Thread!

This is the reason why I went with a 10K and really should have bought a 12K winch.

A 10K winch pulling at 8K uses less amps than a 8K winch pulling at 8K.

 

Indeed. You can use a block and double line pulls to achieve it, too.

Just looked, an M12000 pulling at 8000 lbs draws 312 amps compared to an M8000 at 8000 lbs which draws 435 amps and my XD9000 at 8000 lbs will draw 423 amps.

 

Awesome. I will have to double check the battery. I new it was over 12volts but checked it a couple weeks ago. Still have the warranty so not too worried if it is fubared.

Happy to hear that I won't have to upgrade alternators right away. I feel that all my auxiliaries that I have hooked up to the starter aren't to large. (A few led lights which won't be running all the time if at all) and a winch (again only at certain times). So really it is just the fridge.

Thanks again for the help!

I was thinking the ctek dual250s but for $400 Canadien and another $350-400 for the smartpass to upgrade it just wasn't worth the price. The blue sea isn't a smart charger so I won't get the most optimal charge. However with the solar controller helping as well I think the bang for the buck will be sufficient.

 

Alright I have searched and for the life of me I couldn't find the size of the fuses to run with the ml-acr.

I will be having the second battery in the bed. Using 1/0 gauge for everything. Hoping to use in line fuses do to not having real estate for a breaker. What size fuses should I run?

 

The relay in the ML-ACR can handle 500A according to the specifications.

You size fuses based on the wire size you intend to protect, which with 1/0 wire will be less then 500A. The current carrying rating of wire is based on the diameter, insulation type, temperatures. There's not really one single number.

One rule-of-thumb chart that I think is realistic is this one:
http://www.engineeringtoolbox.com/wire-gauges-d_419.html

It's for a 90 degree C melt temperature for the insulation, 30 degree C ambient temperature and I think based on a 600 second time at that current. So in other words, 200A on a 1/0 ga wire with insulation rated to 90C won't get quite hot enough in 10 minutes to melt through the insulation. Longer than that is unknown.

So you would find a fuse or circuit breaker that opens at greater than 200 amps in 10 minutes or less.

As an example, perhaps the marine fuses that Blue Sea sells, which are actually made by Bussman.

https://www.bluesea.com/products/category/0/42/Marine Rated Battery Fuses

You look at the curves, find the one that meets the current and time requirements.



You read a fuse chart by selecting a fuse size, let's say 100A in this case. That is the rated value. You follow the line for that fuse along the time axis and read up the current axis to see when it will melt. This chart isn't the easiest to see, it's jumbled. But it looks like the 100A is the small dashed line with the round bubbles.

It will carry 100A forever essentially, since 100% rated current isn't even shown. BTW, that's the key point I'd make, that fuses and breakers aren't rated based on protection point but carrying capability. A 100A fuses doesn't open at 100A.

The first point looks to be between 100 and 200 seconds and would be about 125% of rated current, e.g. 125A. At 200% rated current (200A) a 100A it looks like it will melt in 3 seconds. At 300A the 100A fuse will melt at about 0.5 seconds. At 600A the 100A will melt in 0.1 seconds.

This size fuse should protect a 1/0 AWG wire since it's curve shows it will open before the wire would experience potential damage.

 

Yes the ML-ACR, i'm sticking with 2 optima yellow top 27f's. My starting battery is crap, I'll have a new one next week.

 

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Great information. I guess a 100amp fuse is what I will go with.

I guess I wanted to make sure that the size of fuse (100amps) will be sufficient with the blue sea ml acr unit. For instance if I wanted to jump the starting battery would a 100amp fuse be sufficient, or would 100amps be sufficient for the charging demands from the alternator?

Perhaps the wire should be upgraded to make the most of the blue sea unit.

 

Wire size definitely plays a role in the 'jump start' scenario. The correct gauge is dependent on load/demand and also length of run.

IMO, a standard 100 amp fuse or circuit breaker will be insufficient in the jump start scenario. One reason would be the starter can draw way more than 100 amps.

 

That's what I was thinking as well. However most people are using 1/0 gauge so I thought I would be safe there.

i think are starters/alternators are 175 amps....forget though off hand.

 

Where are you going to place your 2nd battery? How long are the wire runs (in feet) going to be? For the positive side, from the starting battery to the ML-ACR and from the 2nd battery to the ML-ACR? And for the ground side, from battery to battery?

I think the starter will be much higher than that. I think I read that it could be a 300 amp draw.

 

Going to the bed of the truck. 8-10 ft runs. Was going to ground the second battery at the frame but may go back to the engine compartment if need to so possibly 8-10 feet for each.

I have read people have been successful with 200amps with this relay. Even scene this relay wired with no fuses as the runs are short. So really I'm starting to think only my run from the second battery should be fused as it's a long run.

Thanks in advance for your help.

 

1/0 will be adequate for a run to the bed. On my 1st gen, that run was closer to 15 feet though and my 2nd battery is located on the driver's side front corner to make the run to the ML-ACR/starting battery as short as possible.

FWIW, the ML-ACR isn't what needs protecting here. It is rated for 500 amps. Your alternator wont even come close to that and I doubt the starter will either. The purpose of a circuit breaker or a fuse it to protect that cable run.

On my setup I put the CB within 12" of the 2nd battery on the positive cable. Instead of a fuse, I used this circuit breaker for its slow trip features. You'll note the chart BlueSea provides demonstrates that even though the CB is rated at 200 amps, it can withstand higher than that for a short amount of time before tripping. According to the chart this CB can withstand a 400 amp draw for 10 seconds before tripping. I figure, if a jump start scenario requires longer that 10 seconds at one burst, I probably have bigger issues.

 

I ran to the bed with a double cab for an aux fuse box and it ended up being almost 15'. Also good quality large gauge cable can get super expensive super quick, so keep that in mind.

 

$193 Crimp Supply Ultra-Flexible Car Battery/Welding Cable - 1/0 Gauge, (15 Feet Red/15 Feet Black) - and 5 Copper Lugs

Here we go. Running to the bed will cost you almost $70. Just FYI. Cable cost caught me by surprise when I was putting my system together.

 

In the MLACR instructions they advise not using a fuse if you intend to use the system for emergency starts.

 

$124 TEMCo 1/0 Gauge AWG 15 Ft Black + 15 Ft Red Flexible Pure Copper Made in USA Welding Cable Battery Wire - Heavy Duty Solar, Inverter, Car, RV, Truck

https://www.amazon.com/TEMCo-WC0051-Welding-Battery-Copper/dp/B00LIB6ZYK

 

Fair enough. I may have to rethink my fuses. Was hoping to get away with anl fuses as they are cheaper than a breaker but may have to rethink that.

My father in law gets me a decent price on welding cable. Can get 50ft of 1/0 welding cable for a decent price in Canadian dollars. About 10cents to you guys

Got that covered above. Shit adds up quick though.

Great information. I can understand why. Leaves me thinking if I'll ever use. Maybe I'll just by pass it if I have to self boost. Take out the fuse and go about it that way. Rather have the fuse instead of a fire.


Thanks again guys for all the help.

As of right now,
-the ml-acr unit will either be in the engine bay (to not have to extend the switch) or in the bed if absolutely necessary
-fuses will be put in. I will probably go with a 200 amp fuse (will double check the limits of the welding wire and the times) if the wire can handle 200 amps for 10 seconds the fuse should blow before it melts, but I'll drop it down to 150amp fuse to be more on the safe side...
-will make the runs as short as possible to ensure decreased volatage drop, resistance and also money on cable even though I'll have 50ft to play with.
-if needing to self boost I will remove the fuses (if needed-don't even know if they will blow at the moment) can monitor the system and determine if it's safe to do so with sizing of wire (based on what I'm hearing it is but fuses become the issue)
-way to monitor charge.

Missing anything?

 

You'll need a way to monitor that level of charge for each battery. There are many options for this. I am happy wit this one: http://www.ebay.com/itm/12V-LED-dou...cator-car-4WD-camper-/222376401987?rmvSB=true

 

I'm thinking since I have the scan gauge reading out the starting battery, a single digital voltage reader in by the driver seat should be fine? This way I can monitor the two while driving.