Weird motorcycle/RV question.....

[BruceMastiff]

I live in my RV full time. It’s hooked up to shore power and I have a12v deep cell battery hooked up to an inverter/charger in my RV, as most do. Pretty much a stock RV setup. I also have a motorcycle thats parked next to it on a battery tender charger/maintainer plugged into 120AC power.

Question is…..can I just hook up my motorcycle to the RV battery for the winter to keep it topped off and skip the battery tender? Any experience with doing this? Pros and Cons? Thanks.

[Second Chance]

I wouldn't. Two batteries on the same charger should be the same series, capacity and - if possible - age.

Rob

[Hoopy Frood]

Yep, sounds like a bad idea.

[Bungy]

I live in my RV full time. It’s hooked up to shore power and I have a12v deep cell battery hooked up to an inverter/charger in my RV, as most do. Pretty much a stock RV setup. I also have a motorcycle thats parked next to it on a battery tender charger/maintainer plugged into 120AC power.

Question is…..can I just hook up my motorcycle to the RV battery for the winter to keep it topped off and skip the battery tender? Any experience with doing this? Pros and Cons? Thanks.

Why don’t you want to leave it on the battery tender? They do a good job.

[jjbbrewer]

can I just hook up my motorcycle to the RV battery for the winter to keep it topped off and skip the battery tender?

Yeah, like others have sort of implied, these batteries have different internal resistances so, connected in parallel, one will kind of drain the other, rather than the charger equally charging both, which is what you want.

Anyway, battery boilers^H^H^H^H .. I mean tenders are kind of a crappy bandaid IMHO. I have EarthX lithiums on 4 of my bikes and NEVER need to "tend" them. They just start and work even after months of storage.

[Butcher]

I do not see why you can't.

IF the batteries are the same type [AGM/AGM, SLA/SLA, Lithium/Lithium] the voltages should be the same. The one charger would not see two batteries but would see just one voltage. The charger would just attempt to keep the voltage at a certain level [what ever the charger is designed for].

Forget about the charger, if you had two of the same type of batteries and one had a lower voltage than the other, hooked them together, then the batteries would even out over time. The higher voltage battery would drain to the lower voltage until they were the same. Capacity should not matter. The type certainly would.

As of the age, batteries do weaken over time and putting a new and old battery together would cause the newer battery to drain so the voltage would even out. If the old battery is internally shorted, then the new battery would eventually drain to 0V. It would not matter about the capacity. I could see a bad motorcycle battery drain a large battery and I could also see a bad large battery drain a motorcycle battery. I would recommend to replace batteries in pairs. Old and new just seems to be a bad idea all th way around.

I use the term 'new' loosely since new batteries should never be considered good batteries and visa versa. In this case, new would be considered good and old be considered bad/worn.

Those of us that have more than one battery in our RV's are commonly hooked up to one charger [converter] and are constantly drained/charged as a pair. IF the motor cycle battery is the same type and condition [ie age] then I cannot see any difference what so ever.

I think people get caught up in the physical size and it really does not matter. If it does, I sure would like to understand the science behind why it would. I do believe the Off Grid Garage did a test about this. Yes, it dealt with lithium batteries. He did an extreme really small battery vs a larger capacity battery. The smaller battery did not take on the bulk of the charge or load. Both batteries did what they normally would.

https://www.batterytender.com/connec...eries-parallel Question 9

[jjbbrewer]

IF the motor cycle battery is the same type and condition [ie age] then I cannot see any difference what so ever.

They're not. RV batteries are deep cycle, motorcycle batteries starter/cranking types.

Go read here - https://batteryuniversity.com/

[Butcher]

Yes, they are different but the charger would not know that since they voltages are the same.

A deep cycle battery is designed to be cycled and not deliver a lot of amps. A starting battery is designed not to be cycled and will die quickly if they are but they give a lot of amps when needed. Internally, they are designed differently, but the chemistry is the same, therefore the same charging voltage.

Still not satisfied but keep trying. I'm willing to be schooled.

[jjbbrewer]

Yes, they are different but the charger would not know that since they voltages are the same.

It's not about the charger.

Still not satisfied but keep trying. I'm willing to be schooled.

Did you read the articles on the Battery University link I posted?

[Butcher]

I do not have weeks to read that link. It is pretty long. If there is a direct link you would like me to read, I am game.

I am not good with explaining myself so here are a couple videos that does a better job. The second video explains more about larger current chargers but I do not think this is the case.

https://www.youtube.com/watch?v=fQz7vZEYLfY
https://www.youtube.com/watch?v=G7m3...XDT7pQ&index=2

Yes, I do understand this is a LifePo4 type battery and not SLA. If the battery types are the same, their full charge voltages should be the same. The charger is designed to put out a certain voltage and tries to maintain that voltage with current. As long as that voltage is not too high for the battery type, the battery will not be ruined. That is my take on it as long as the batteries are the same chemistry, you will be fine.

Of course, everyone can just learn on their own and find out what works for them. My take on the OP is that it does not matter