If I have a junior battery tender for a motorcycle will it work as efficient as the larger style?

It is the smart style so seems the same but why buy a large one too?

They are both 12 volt and a Harley has a big battery.

Just a marketing thing, you got to have one for each so now they sold me two.

** I should note that I don't need both on at the same time.

 

I'm going to assume you're asking about a BATTERY TENDER made by the DELTRAN CORPORATION...and not using the term in the generic sense which is common with past posts.
If you already have a BATTERY TENDER JR. which puts out .75 amps of peak power, then yes it'll work on an automotive battery. You'll have to keep in mind that it will probably take longer (and probably more often in charging mode on a C5/Z06 electronics laden vehicle) to bring the battery up to full charge before it starts the float cycle.
In that regard, it won't be as "efficient" as a BATTERY TENDER PLUS which puts out 1.25 amps of peak power.
From the hundreds (literally) of past discussions about float maintenance chargers, there are many who prefer to use the BATTERY TENDER JR. on their automotive battery for whatever reason (it is typically less expensive than the larger version).

 

Hi, from many past threads and experience, many have determined that a Battery Tender JR doesn't have the proper output to keep an AGM battery such as an Optima Red Top at peak charge, and it especially won't keep a Deep Cycle battery at peak efficiency. For non AGM types it will probably do ok. For AGM types the 1.25 amp output is neccessary. And also the proper programming to handle AGM. I know the company advertises it's good for AGM, and I'm sure some people are using them, but as I said history and a preponderance of anecdotal evidence ,and experience say it is not the one to use for AGM.
Let the battle begin again--Good Luck

 

What has been posted here makes sense to me.

"I see", said the blind man.

 

1.25 amps is too high.

Here is what Optima says on their website:

"QUESTION

Can you trickle charge an OPTIMA? And what type of charger can I use?

ANSWER

Yes and you can use any charger on an OPTIMA as long as the voltage is regulated properly. If your charger will remain on indefinitely, the voltage should be at 13.8 volts maximum with a one amp maximum current."

Here is the complete charging info for an Optima Redtop Battery, from their Website:

OPTIMA RedTop Charging Information
The following charging methods are recommended to insure a long battery life - always use a voltage-regulated charger, with voltage limits set as described below.

RedTop Type: 34 & 34R - 34/78 - 6V - 25 & 35 - 75/25
These batteries are designed for engine starting applications. They are NOT recommended or warranted for use in deep cycle applications.

Recommended charging information:
Alternator:

13.3 to 15.0 volts, no amperage limit.
Battery Charger:

13.8 to 15.0 volts, 10 amps maximum, 6-12 hours approximate.
Rapid Recharge:

Maximum voltage 15.6 volts (regulated), no current limit as long as battery temperature remains below 125°F (51.7°C). Charge until current drops below 1 amp.
Float Charge:

13.2 to 13.8 volts, 1 amp maximum current, time indefinite (at lower voltage).

All limits must be strictly adhered to.
Safety Information:

Always wear safety glasses when working with batteries.
Always use a voltage regulated battery charger with limits set to the above ratings. Overcharging can cause the safety valves to open and battery gasses to escape, resulting in premature failure. These gasses are flammable! You cannot replace water in sealed batteries that have been overcharged. Any battery that becomes very hot or makes a hissing sound while recharging should be disconnected immediately.
Failure to fully charge a battery can result in poor performance and a reduction in capacity.

 

I've used nothing but OPTIMA batteries for several years, even prior to the time the general public was even able to buy them. I knew about the 1.0 amp maximum recommendation and had some concern with the BATTERY TENDER PLUS 1.25 amp output.
I've used only BATTERY TENDER PLUS 1.25 amp float chargers on each of the vehicles that didn't get driven regularly.
I've talked to techs from both DELTRAN CORPORATION and OPTIMA. Both said a 1.25 amp charger is fine on an OPTIMA battery if the battery is healthy.
It'll charge, then go into float, so the amp input is not constant. Neither recommended more than that due to the heat generated internally. Neither recommended using any charger that uses more than that for any sustained time period.
FYI, the highly touted CTEK MULTI US 3300 puts out even more minimum amps...(2-90 is what I recall on that model).

 

Hi you are somewhat misunderstanding the limits for the indefinite,BOLDED, charge situation. What it is saying is that at lower voltage13.2-13.8 the max current for an indefinite time period should be no more than 1amp. The fact that a maintainer puts out more than 1amp does not mean that it is to much, as long as the maintainer has the programming to tamp down the current to a non overheating amount as the battery becomes full charged. Moreover maintainers that do not put out over 1amp will not maintain an Optima at full charge, and especially a deep Cycle Optima. Current and Voltage have a proportinate ratio to each other as to heat generated.
Good Luck