Connection length to batteries in parallel

[2TheStreet]

I have two 155 ah dry cell deep cycle AGM batteries connected in parallel in between my two wheel wells inside my cargo van. I would like to add another max 155 ah battery in parallel with my other two batteries (so 3 total 155 ah batteries) but I can only fit another battery on the other side of the wheel well (rear of van) which would leave about a 4 foot gap to connect to the batteries centered between the the wheels, I would most likely have to get 6 foot 2 AWG connector cables to reach the other battery that is connected in parallel to the other battery. My question is, would it be ok to connect another battery with 6 foot 2 AWG cables or would that cause a problem? My batteries are being charged by a Renogy MPPT 40 amp solar charger and 4x 100 watt Renogy bendable solar panels on the roof of my van. Also, if you say that connection would be ok, would it be advisable to connect the positive cable from the solar controller to the first battery and the negative  cable to the last battey's negative terminal, or does it really matter?

 

[ccbreder]

size the wire to carry the amps you are going to draw. probable your inverter will be the factor. Large cables will do the job. don't forget fuses.

 

[Optimistic Paranoid]

size the wire to carry the amps you are going to draw. probable your inverter will be the factor. Large cables will do the job. don't forget fuses.

X2

Whatever size wire you use for your inverter hook up should be the minimum wire size you use to hook in the other battery.

Regards
John

 

[MikeRuth]

My 2 cents, I can't make out the size of your inverter but if your going to have a 6 foot run then that's going to be 12 feet total. I'd suggest you go even larger at 0 AWG. for the small additional cost the system will work better.

Your Charge controller connection to the battery should simply be as close to one of the batteries as possible. If the batteries are in boxes the CC needs to be outside of the box.
Essentialy once all three batteries are connected in parallel it's the same as on larger capacity battery.

 

[2TheStreet]

I think I'm going to just keep it to my two 155 AH batteries with 4 x 100 watt solar panels. I've never dropped below 12.7 volts but I haven't started cooking with my 1300 watt induction burner I just bought. I will have my butane burner for back-up though just in case. I only cook stir fry of quick foods less than 15-20 minutes so I doubt I use too much power, induction cooks quick.
I haven't sued the 600 watt microwave yet either but don't anticipate much use except for a small frozen meal or re-heat left-overs for a couple minutes.
My Dometic CF-18 refrigerator set to half way @ 29 degrees uses very little power believe it or not, I keep it running 24/7.
I just bought a 2000 watt inverter to replace the 1000 watt inverter bought so I can run my 1300 watt induction burner. I won't overload the inverter, one item at a time. We'll see how it goes on my first trip, I can always add a battery later on if I need more capacity. These 100 watt bendable Renogy solar panels pull in very good power, even on overcast days it's still pulling in power here in ohio.

 

[LeeRevell]

You'll find the microwave will use 1,000 watts or more to cook at 600 watts.

 

[SternWake]

Batteries in parallel,  act more like one big battery, the thicker the parallelling cables are.


When the batteries in parallel are distant from each other, the thickness of this cabling becomes more important, than if they are side by side.

Ideal wiring of batteries in parallel places all load and charge on the (-) of one battery, and the load and charge(+) on the most distant battery of those in parallel.

Ideal is not always achievable, but can be negated by occasionally swapping battery locations.

The thinner the cabling, when the batteries are not wired in a balanced manner, the harder it is on one battery or the other, as it works harder.

Check out this video of 3 12v batteries that were right next to each other, but not wired in a balanced manner:



Also when hooking batteries of different ages and condition, the newest battery usually has a higher fully charged resting voltage, and less resistance, and as such it performs more work, and accepts more charging current than the older paralleled  batteries, and then when discharging, will actually feed the older batteries.  As such this newer battery quickly degrades to the level of the older batteries.

Obviously the age difference of the batteries matters.  Adding a new battery to another battery with under 50 cycles on it should not be much of an issue, but a new battery paralleled to a battery with 250 cycles on it is very abusive to the new battery.

So if 3 batteries are distant from each other, the paralleling cable thickness is very important, and the bigger the loads on it, like a 1200 watt induction cooker, the more important those thick cables and the quality of their terminations, become.  Wiring them in a balanced manner with (+) and (-) NOT on the same battery helps greatly.  If this is too inconvenient, I recommend swapping battery locations every so often so one battery is not worked so much harder than the others.  This is also inconvenient.

The difference in ultimate battery longevity can be profound, when paralleled wired in a balanced manner, compared to an unbalanced manner.

I am curious if induction cookers work OK or suffer some performance loss on MSW inverters compared to PSW inverters.  Lots of reports of longer cooking times and shortened lifespans on Microwaves on MSW inverters.

 

[akrvbob]

I'd use a minimum of 2/0 (two-ought) and 4/0 (four-ought) would be better.

I have a similiar system with a 2000 watt inverter and microwave but I have 4 golf carts. I would not use less than 2/0 for the inverter.
Bob

 

[2TheStreet]

Batteries in parallel,  act more like one big battery, the thicker the parallelling cables are.


When the batteries in parallel are distant from each other, the thickness of this cabling becomes more important, than if they are side by side.

Ideal wiring of batteries in parallel places all load and charge on the (-) of one battery, and the load and charge(+) on the most distant battery of those in parallel.

Ideal is not always achievable, but can be negated by occasionally swapping battery locations.

The thinner the cabling, when the batteries are not wired in a balanced manner, the harder it is on one battery or the other, as it works harder.

Check out this video of 3 12v batteries that were right next to each other, but not wired in a balanced manner:



Also when hooking batteries of different ages and condition, the newest battery usually has a higher fully charged resting voltage, and less resistance, and as such it performs more work, and accepts more charging current than the older paralleled  batteries, and then when discharging, will actually feed the older batteries.  As such this newer battery quickly degrades to the level of the older batteries.

Obviously the age difference of the batteries matters.  Adding a new battery to another battery with under 50 cycles on it should not be much of an issue, but a new battery paralleled to a battery with 250 cycles on it is very abusive to the new battery.

So if 3 batteries are distant from each other, the paralleling cable thickness is very important, and the bigger the loads on it, like a 1200 watt induction cooker, the more important those thick cables and the quality of their terminations, become.  Wiring them in a balanced manner with (+) and (-) NOT on the same battery helps greatly.  If this is too inconvenient, I recommend swapping battery locations every so often so one battery is not worked so much harder than the others.  This is also inconvenient.

The difference in ultimate battery longevity can be profound, when paralleled wired in a balanced manner, compared to an unbalanced manner.

I am curious if induction cookers work OK or suffer some performance loss on MSW inverters compared to PSW inverters.  Lots of reports of longer cooking times and shortened lifespans on Microwaves on MSW inverters.

Thanks for the info. I've never used anything other than a PSW inverter so i couldn't tell you the difference. I love induction burners and have an induction stock in my house, heats up fast.

 

[2TheStreet]

I'd use a minimum of 2/0 (two-ought) and 4/0 (four-ought) would be better.

I have a similiar system with a 2000 watt inverter and microwave but I have 4 golf carts. I would not use less than 2/0 for the inverter.
Bob

Yeah I have 2 awg connector cables for the inverter. How many amp hours are your running?
I don't know if I should go with another 155 ah battery or not, right now have 310 amp hours with the two 155 ah batteries.

 

[akrvbob]

I don't want to assume anything so if this is something you already know then forgive me, it may help someone who doesn't.

2/0 and 2 are very, very different things. Gauges start at 0 and go up in size and get smaller with the number. 0 is bigger than 2, 2 is bigger than 4, etc until you get to 20 which is tiny.

On the other hand, there are gauges that start at 0 and the cable size gets bigger with the number, they are designated by a /0 and commonly called "ought" meaning 0. 2/0 (2-ought) is much bigger than 0 which is bigger than 2. 4/0 (four-ought) is much bigger than 2/0 (two-ought).

If you are using 2 gauge, then I think you are using a much too small a wire and I would encourage you to use at least 0 and I used 2/0 and I would encourage you to do the same.

It won't cost much more and will provide peace of mind at a very cheap price.
Bob

 

[2TheStreet]

I don't want to assume anything so if this is something you already know then forgive me, it may help someone who doesn't.

2/0 and 2 are very, very different things.  Gauges start at 0 and go up in size and get smaller with the number. 0 is bigger than 2, 2 is bigger than 4, etc until you get to 20 which is tiny.

On the other hand, there are gauges that start at 0 and the cable size gets bigger with the number, they are designated by a /0 and commonly called "ought" meaning 0. 2/0 (2-ought) is much bigger than 0 which is bigger than 2. 4/0 (four-ought) is much bigger than 2/0 (two-ought).

If you are using 2 gauge, then I think you are using a much too small a wire and I would encourage you to use at least 0 and I used 2/0 and I would encourage you to do the same.

It won't cost much more and will provide peace of mind at a very cheap price.
Bob

Hey thanks for the info. I'm just going to keep it to two 155ah batteries, I contacted Renogy to see what the battery requirement is for 4 x 100 watt panels, they said 260 AH so I'm well above that with 310 AH. Also, I live in Ohio and we get a ton of cloudy days and in the winter cloudy days are even more prevalent. If need be, I have a butane burner as a back-up to my 1300 watt induction burner. I'm planning a trip out to the rocky mountains so I'll be able to put everything to the test.

 

[highdesertranger]

well stern said everything I was going to say(much better too). oh one other thing AGM batteries are not dry cells. the are absorbed glass matt(AGM) the acid is in the matt, if you where to open one remove the matt and wring it out the acid would come out as liquid. just saying. highdesertranger

 

[2TheStreet]

well stern said everything I was going to say(much better too).  oh one other thing AGM batteries are not dry cells.  the are absorbed glass matt(AGM)  the acid is in the matt,  if you where to open one remove the matt and wring it out the acid would come out as liquid.  just saying.  highdesertranger

Sealed and I won't be opening any battery. lol  I wish lithium ion batteries were cheaper, I'd have some of those in a heartbeat. Lithium ion batteries can be used to depletion instead of the 60% rate with regular batteries. $3k for a 300 ah battery is steep.

 

[ccbreder]

We are not talking about battery amp hours, but wire size. If you check a few operating manuals you will find a 2000 watt inverter recommends 2/0 gauge cable at 10 feet from the battery bank.