Topic: will my "battery tender" maintain more than one battery?

[gregk]

With about 6 batteries sitting on my work bench waiting for spring, I wondered if the battery tender would work if I hooked them all up positive to positive and ground to ground and then connected the tender up?  seems to me when I was a kid working at a gas station, they guys in the back would do this. 

Greg

[TwoTired]

What are the specs for the tender you wish to use?

Are all the batteries the same age and have exactly the same (matched) peak voltage level?

Do you care if some of the batteries are damaged and have a shorter life?


Usually the answer to your basic question is, no.

Cheers.

[nickjtc]

FWIW I've ganged three batteries together on a Battery Tender, after fully charging each one separately, all through a winter. Whether their individual 'lives' were affected I don't know, but one of them was five years old and still going strong when I sold the bike.

[MCRider]

With about 6 batteries sitting on my work bench waiting for spring, I wondered if the battery tender would work if I hooked them all up positive to positive and ground to ground and then connected the tender up?  seems to me when I was a kid working at a gas station, they guys in the back would do this. 

Greg

According to Battery Tender FAQ- Yes, with some minor caveats.
http://batterytender.com/faqs.php/#14

More here: http://batterytender.com/faqs.php

[mystic_1]

One of these would be more ideal:




mystic_1

[TwoTired]

With about 6 batteries sitting on my work bench waiting for spring, I wondered if the battery tender would work if I hooked them all up positive to positive and ground to ground and then connected the tender up?  seems to me when I was a kid working at a gas station, they guys in the back would do this. 

Greg

According to Battery Tender FAQ- Yes, with some minor caveats.
http://batterytender.com/faqs.php/#14

More here: http://batterytender.com/faqs.php

From your link...
"Our recommendation is that you not charge batteries in parallel, again assuming that the batteries are 100% discharged. If the batteries are only partially discharged, then it is probably OK to charge them in parallel."

I guess we just seek the answers we are looking for?

There are technical reasons why you shouldn't.  You can get away with doing so sometimes.  You can also screw up a battery (or two) sometimes.  Further, not all "tenders" are built the same and operate in the same way, regardless of their brand name.

Without the specs on the charger he wishes to use, there is absolutely no way to determine if it can maintain or even charge six - 12V flooded cell batteries connected in parallel.  If the charger presents less energy than required to overcome the batteries internal resistance, the batteries will slowly discharge.

Do all the batteries have the same electrolyte concentration?  Do they all have exactly the same plates area in every cell?  Do they all have exactly the same voltage level when at full charge?  Will the interconnect wiring and connections contribute any resistance to the offered charge?  Will the charger be connected to the middle of the assembled battery bank or at the end?  Will the far battery receive the same voltage as the one nearest to the charger?  Are you expecting full unattended battery maintaining?  Or, will you check the battery's individual status weekly or monthly for individual cell state of charge? 

There are reasons to simply not wire these batteries in parallel, even aside from the charging issue, as naturally stronger batteries will be fatigued, by giving their higher charge level to the weaker ones.  The weaker ones will be overcharged and the stronger ones will be undercharged.  A single monitoring device cannot detect an individual battery in a parallel wired bank.

Can it be done?  Sure.  Is there a 100% guarantee of success? No.  Is there a 100% guarantee of failure?  No.  Is it recommended?  No. 
However, if you are diligent about monitoring cell status, and rearrange your bank component placement periodically, and your charger can overcome the bank's total internal resistance with a significant margin, then it can be done.
Additionally, if you are a lucky SOB and feel you can beat the odds, then go for it!

Cheers,

[gregk]

There seems to be alot of yes and no claims in the manufacturers web site concerning charging multiple batteries.  I was only looking at getting away from changing the charger from one to the next.  In view of the possibility of ruining my batteries, I think that I will take the time to peroidically change the charger from one to the next and know full well that the batteries will be there in the spring.

Thanks for the help

Greg