2nd battery in parallel

[Rusty2000]

Hi All,

Anyone fitted a 2nd battery wired in parallel to boost the current available? Might overcome a lot of electrical issues!

Russell

 

[Raven]

I think the issue is where to put it.

 

[scottmastrocinque]

You will gain nothing.

Batteries wired in parallel have their capacities added (amp hours) together but the voltage remains the same.

 

[Brett]

A good battery in good health with clean connections with any Startus Interruptus issues resolved is all I have every needed across three bikes now. In my opinion, that would be a lot of effort for something a bit of attention and maintenance will resolve.

 

[Brian UK]

No benefit at all. You are ultimately limited by the output of the alternator. If you take more out of any battery than you are putting in, it will die eventually.
There is also the danger of one cell going down in one battery which will then discharge the other battery.
The only safe way to connect two batteries is through a split charge relay, then have some load on one and some on the other. Thus they are only connected together when charging. When not charging they are seperated, so any problem would not affect both.

 

[Rusty2000]

I think the issue is where to put it.

I have a topbox, or the panniers.

 

[Raven]

I have a topbox, or the panniers.

You are joking, right?

 

[Brett]

If you are worried about being stranded and need a way to boost I would look at something like this.

NOCO - 500A Lithium Jump Starter - GB20

The GB20 is a portable lithium-ion battery jump starter booster pack that delivers 500-amps for jump starting a car, boat, motorcycle and more.

no.co

 

[Rusty2000]

You are joking, right?

No I am not. As my Stelvio is a 2008 model the wiring is 13 years old. Despite mine and in earlier times, Guzzi dealers, best efforts to clean and lubricate the dozens of electrical connections they will degenerate with moisture, road salt, power washing, etc. As many of them are buried beneath the tank and in the fairing they are neglected. An additional battery will allow sub-standatd connections to pass more current. Simple as.

 

[Rusty2000]

If you are worried about being stranded and need a way to boost I would look at something like this.

NOCO - 500A Lithium Jump Starter - GB20

The GB20 is a portable lithium-ion battery jump starter booster pack that delivers 500-amps for jump starting a car, boat, motorcycle and more.

no.co

Got two different well-known brands, both useless having never worked on any of my 3 bikes and 2 cars tried on. Electrical junk.

 

[Rusty2000]

You will gain nothing.

Batteries wired in parallel have their capacities added (amp hours) together but the voltage remains the same.

But double the current available.

 

[Rusty2000]

A good battery in good health with clean connections with any Startus Interruptus issues resolved is all I have every needed across three bikes now. In my opinion, that would be a lot of effort for something a bit of attention and maintenance will resolve.

Bike is very well maintained but is now 13 years old, has been kept outside under a cover for some years so has suffered from electrical corrosion. The block connected below the headstock was replaced some years ago as it deteriorated into green dust despite having a full dealer service history at the time and only 20k miles on it.

 

[Rusty2000]

No benefit at all. You are ultimately limited by the output of the alternator. If you take more out of any battery than you are putting in, it will die eventually.
There is also the danger of one cell going down in one battery which will then discharge the other battery.
The only safe way to connect two batteries is through a split charge relay, then have some load on one and some on the other. Thus they are only connected together when charging. When not charging they are seperated, so any problem would not affect both.

Noted. The alternator should have enough watts to charge both but the effect I am seeking is additional current. Wouldn't a relay negate this?

 

[Brett]

My opinion would be to repair the bad wiring. That will resolve your issues. Two batteries will give you double the current, but the fusing and corroded wiring will be your limitations. I am certain you could find a used harness and parts online to resolve some of your green dust issues.

 

[Brett]

Got two different well-known brands, both useless having never worked on any of my 3 bikes and 2 cars tried on. Electrical junk.

You and I have had very different experiences, I have a larger version Noco for my diesel vehicles. The only time it couldn’t jump a vehicle was when the battery was so bad it determined there wasn’t one in the circuit. I had to get one as I had at one point two vehicles with parasitic drains and was tired of being stranded.

 

[jr1967]

If your aim is to have a better chance of starting the engine, then for sure a second battery in parallel will result in a smaller voltage drop during a start, so less chance of an under voltage no start condition. For starting purposes I see no need for a 'house battery' isolation relay like you would have in a motorhome.
Other than that two batteries will not do anything for adding more available power to accessories if the alternator is not up to the task of keeping the charge up. It will just keep you going a bit longer.
Perhaps adding an auxilary plug to your battery to use a suggested jump starter pack will be a solution for the odd time the bike doesn't start?

 

[V700Steve]

I set up new Guzzi's that had 2 batteries in the tail under the seat. May have been a Daytona or a Sporty.

 

[Lannis]

My opinion would be to repair the bad wiring. That will resolve your issues. To batteries will give you double the current, but the fusing and corroded wiring will be your limitations. I am certain you could find a used harness and parts online to resolve some of your green dust issues.

I agree. Rusty's wiring already has 200 connectors, some number of which are visibly and functionally already bad. That's only going to get worse with time, current, and heat, and forcing more current through them to try to overcome the resistance of the corrosion is probably going to heat them up to the point where something will melt (just short of blowing a fuse).

Chuck Stottlemeyer has a very nice documentary somewhere where he does regular maintenance every few years (he's an aircraft builder) on one of his older V50s completely covering the electrical system including every connector and connector block. There are probably a lot more connectors on your Stelvio, but the principle is the same.

Lannis

 

[scottmastrocinque]

But double the current available.

No. You are completely incorrect.

Putting two voltage sources in parallel does not increase amperage in the circuit.

Ohm's law ( V=IR ), tells us the only way to increase current is to increase voltage, or decrease resistance. [Reaaranged for amperage (current) it becomes I=V/R. More current is only available by increasing V or reducing R. - Period.]

Putting two voltage sources in parallel doesn't do either of those things.

The current (amps) will remain exactly the same. What changes is the capacity (amp hr).

The voltage will also remain 12V.

 

[Brett]

It will give you double the available current in addition to double the AHr capacity. Your equipment will still only draw what they were designed to draw. You may have a slightly healthier crank, but that would be achieved by a slightly oversized lithium battery equivalent without all the extra junk hung on the bike. If you are hell bent on two batteries, match the batteries - same make model and age (brand new). Be sure the wiring from each is of identical gauge and length. Have the main positive come from one battery then the negative come from the other (I struggle to get my head around how this effects battery draw, but we have done studies at work and have seen the difference).

This conversation is bizarre to me, it would by like having a car with a slow leaking tire and installing a second axle to resolve it.