Can I keep 2 Bikes on a single Battery Tender?

[Bob_1978]

Since I don't see a splitter cable that would allow this, I am thinking of an alternate solution: running an extension cord between the the two bikes.  Bike A has two (2) direct-to-terminal connections and Bike B has one (1) direct to terminal connections.  Tender would be connected to Bike A, and the second terminal connection would hook up with Bike B.

 

Buying a second Tender isn't an option since I only have one outlet.

 

Has anyone tried this?  I don't want to fry any of the electronics on the bikes - a 2013 RT and 2004 RT, respectively.

 

Thanks for any advice!

[RogerC60]

I've never tried it, but as an electrical engineer and knowing what I do about electricity and how battery chargers work, I would strongly advise against it. It's almost guaranteed that the two batteries will be at different levels of charge, with the result that the battery tender will over charge one of them.

 

Can't you get a small extension cord or outlet strip to plug into your one electrical outlet and turn it into 3 or 6 or whatever?

[Bob_1978]

Thanks Roger.  Yeah I can get an extension cord/power strip and get a second Battery Tender.  But if I recall they recommend a direct plug-in to an AC outlet.  But that sounds less risky for sure.

[Hosstage]

I run my tender on a good (read #12 awg, heavy) extension cord to the second bike. I switch the tender back and forth between bikes weekly during long term storage. I would not run two bikes off of one tender at the same time. Just switch back and forth.

I don't like to leave the tender plugged in uninterrupted for much longer than a couple weeks at a time, I like to unplug for a day or two and just let the battery, and tender, rest for a day or two.

[RogerC60]

1 hour ago, Hosstage said:

I run my tender on a good (read #12 awg, heavy) extension cord to the second bike. I switch the tender back and forth between bikes weekly during long term storage. I would not run two bikes off of one tender at the same time. Just switch back and forth.

I don't like to leave the tender plugged in uninterrupted for much longer than a couple weeks at a time, I like to unplug for a day or two and just let the battery, and tender, rest for a day or two.

 

That's probably the best approach all told. You don't really need to leave the battery on the tender continuously.

[Carlisja]

This

 

https://smile.amazon.com/gp/product/B00KBTQFVS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

 

they have 4 bank versions too and they are smart tenders meaning they are not always pumping juice into the battery.

[dirtrider]

11 hours ago, Bob_1978 said:

Since I don't see a splitter cable that would allow this, I am thinking of an alternate solution: running an extension cord between the the two bikes.  Bike A has two (2) direct-to-terminal connections and Bike B has one (1) direct to terminal connections.  Tender would be connected to Bike A, and the second terminal connection would hook up with Bike B.

 

Buying a second Tender isn't an option since I only have one outlet.

 

Has anyone tried this?  I don't want to fry any of the electronics on the bikes - a 2013 RT and 2004 RT, respectively.

 

Thanks for any advice!

Morning Bob_1978

 

Can you charge 2 batteries with one charger? Yes, do you want to do that, NO.

 

Some police motorcycles, some tractors, etc do use one alternator to keep 2 or even 4 batteries charged but there are limitations such as matching batteries, switching relays, etc. For long term battery maintenance type charging it won't work properly.

 

Go into about any BMW motorcycle dealer a few years ago & you will probably see multiple motorcycles being hooked to a single battery charger/tender. BUT, those were special multi-battery chargers with multiple charging connections.  

 

For what you want to do it won't work properly so you will probably over charge one of the batteries & undercharge the other. 

 

If you are going to be around the motorcycles all winter then  you can use one charger for multiple motorcycles by using a central charger then running separate charging leads to each motorcycle, then just plug your charger into each of the charging leads in turn every few weeks. (if your motorcycles use different battery types then be darn sure to change the settings on your battery charger to match the battery being charged) 

 

Personally I use a single charger for multiple motorcycles & other pieces of equipment   (usually about 4 vehicles per charger) BUT, I disconnect the battery's from the vehicle so there is no parasitic  drain.   

 

A disconnected battery can go months without re-charging in cool or cold weather & some vehicles with disconnected AGM type batteries can go all winter storage with only one mid-winter top-off.  On some of my older equipment with large older lead-acid  battery's I usually hook those up every month or so. 

 

If you search around enough you can probably find some electronic controls that allow charging multi (same type) battery's from one charging source (will keep them matched).  Probably find those in off-grid living searching but the cost to buy & rig up something like that would be well above just buying a second charger/maintainer. 

 

If you are clever you could even make your own single battery charger into an automatic  2 battery charging control using a lamp timer and a double-throw relay with the relay being ON  charging one battery & the relay being OFF then charging the other battery. 

 

 

[Selden]

4 hours ago, Carlisja said:

This

 

https://smile.amazon.com/gp/product/B00KBTQFVS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

 

they have 4 bank versions too and they are smart tenders meaning they are not always pumping juice into the battery.

 

I do not see the benefit of this approach, unless one is charging multiple batteries on a bench. I could buy two Battery Tenders for less than the $126.89 (2) $224.90 (4) asking prices. Even better, with two separate battery tenders, the bikes don't have to be parked near each other.

[dirtrider]

28 minutes ago, Selden said:

 

I do not see the benefit of this approach, unless one is charging multiple batteries on a bench. I could buy two Battery Tenders for less than the $126.89 (2) $224.90 (4) asking prices. Even better, with two separate battery tenders, the bikes don't have to be parked near each other.

Morning Selden 

 

I agree, not only is that a lot of money but according to what is stated on that charger it automatically applies a desulfation cycle if the battery is low. A quick check shows that desulfation cycle could apply up to 20 volts pulsed to the battery during that cycle. 

 

BMW specifically cautions against exceeding 15 volts  during charging if the battery is still connected to the vehicles electrical system to avoid possible system damage. 

 

Now the battery itself will act as a capacitor & smooth the 20v pulses out but if the battery posts see 20v then so does the vehicles expensive electrical/electronics systems. 

 

It probably won't bother his older 2004 but could exceed the BMW voltage recommendations on Bob's 2013.

------------------------------------------------------------------------------------------------------------

"The OptiMate's unique automatic desulfation mode works like this: Once the OptiMate determines that the battery is sulfated it applies a voltage of up to about 20v at a controlled low current for a maximum period of two hours, to recover the battery to the extent that it can again accept a charge using the more normal"

[Bob_1978]

Thanks to all who replied.  I live in Seattle so am able to ride both bikes every couple of weeks throughout the winter.  That, plus moving the charger from one bike to the other every week, sounds like the best solution.

[Michaelr11]

16 hours ago, Bob_1978 said:

Buying a second Tender isn't an option since I only have one outlet.

 

Go to the hardware store or hardware section of your favorite home store.  They will have a plug in that goes into one electrical outlet and will provide two or three outlets.  Two smart chargers will not overload it.  Or even easier.  Buy a electrical outlet strip with its own on-off switch.  Plug the strip into the one outlet and two chargers into the strip.  Turn on the strip and both chargers will start.  When both bikes are charged up, turn the strip off.

[Carlisja]

3 hours ago, dirtrider said:

Morning Selden 

 

I agree, not only is that a lot of money but according to what is stated on that charger it automatically applies a desulfation cycle if the battery is low. A quick check shows that desulfation cycle could apply up to 20 volts pulsed to the battery during that cycle. 

 

BMW specifically cautions against exceeding 15 volts  during charging if the battery is still connected to the vehicles electrical system to avoid possible system damage. 

 

Now the battery itself will act as a capacitor & smooth the 20v pulses out but if the battery posts see 20v then so does the vehicles expensive electrical/electronics systems. 

 

It probably won't bother his older 2004 but could exceed the BMW voltage recommendations on Bob's 2013.

------------------------------------------------------------------------------------------------------------

"The OptiMate's unique automatic desulfation mode works like this: Once the OptiMate determines that the battery is sulfated it applies a voltage of up to about 20v at a controlled low current for a maximum period of two hours, to recover the battery to the extent that it can again accept a charge using the more normal"

 

Ok. I like Optimate.   But there are other tenders that offer multiple heads.  I am no a fan of Battery Tender but https://smile.amazon.com/Battery-Tender-022-0165-DL-WH-12-Volt-Management/dp/B000NCOKV0/ref=sr_1_12_sspa?crid=3JBJL84AZBD42&dchild=1&keywords=2+bank+battery+charger&qid=1607454620&sprefix=bank+battery+charger%2Caps%2C153&sr=8-12-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExWE5NMVk4NlNMWU8mZW5jcnlwdGVkSWQ9QTAzNDUwNTIySVlFSlVZQU80WkFZJmVuY3J5cHRlZEFkSWQ9QTEwMjQxNDgzS0k1R0JTQU9PWFE2JndpZGdldE5hbWU9c3BfbXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

[Lowndes]

Bob,

 

BatteryMINDer has info on charging multiple batteries here, Q/A #9:  https://www.batteryminders.com/faq-1/

 

Q: Can I charge more than one battery at a time with the BatteryMINDer?

        A: Yes, you can charge up to four batteries of similar type and condition with BatteryMINDer models 12106, 12106A 8V, 12117, 12118 and 12151.  You can charge up to six batteries of different types and conditions with BatteryMINDer models 12248, 24041, 36271 and 28252.  See the section on Multi Battery Connections in our Knowledge center for additional information and safety guidelines.    

 

 

Plus:

Q: How long can I leave the BatteryMINDer connected to my battery?

        A: As long as it is plugged in you can leave the BatteryMINDer hooked up to a battery indefinitely.  It will never overcharge or damage your battery. 

 

These chargers have a Desulfation cycle that works.

 

They also have the wiring connectors for multible battery connections:    https://www.batteryminders.com/multiple-battery-connector-210-AY

 

I 'm not affiliated in any way except as a very satisfied customer.  

 

Several models are vailable on Amazon.

[dirtrider]

9 hours ago, Lowndes said:

Bob,

 

BatteryMINDer has info on charging multiple batteries here, Q/A #9:  https://www.batteryminders.com/faq-1/

 

Q: Can I charge more than one battery at a time with the BatteryMINDer?

        A: Yes, you can charge up to four batteries of similar type and condition with BatteryMINDer models 12106, 12106A 8V, 12117, 12118 and 12151.  You can charge up to six batteries of different types and conditions with BatteryMINDer models 12248, 24041, 36271 and 28252.  See the section on Multi Battery Connections in our Knowledge center for additional information and safety guidelines.    

 

 

Plus:

Q: How long can I leave the BatteryMINDer connected to my battery?

        A: As long as it is plugged in you can leave the BatteryMINDer hooked up to a battery indefinitely.  It will never overcharge or damage your battery. 

 

These chargers have a Desulfation cycle that works.

 

They also have the wiring connectors for multible battery connections:    https://www.batteryminders.com/multiple-battery-connector-210-AY

 

I 'm not affiliated in any way except as a very satisfied customer.  

 

Several models are vailable on Amazon.

Morning  Lowndes

 

The BIG kicker on this is: batteries of similar type and condition

 

You can't mismatch battery condition, mismatch battery type, or mismatch battery sulfation levels, even mismatched battery ages can effect this.

 

If you have ever owned an older tractor or piece of equipment that uses multiple-batteries (either series or parallel) you will understand the difficulty in trying to charge the battery's at the same time using one charger. 

 

It can (usually) be made to work OK on back-up battery systems or similar battery arrays IF the batteries are all the same brand, about the same age, same size, same condition. Not so much on mismatched or different condition battery's. 

[RTinNC]

I have been running 2 Battery Tenders off of a heavy duty power strip now for at least 10 years.  Never an issue.  

 

[Bob_1978]

Thanks - I can see how that would work.  But you can' t run a single tender to two batteries via a serial connection or splitter.