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Battery tender

When I worked at advance auto many moons ago we had that exact brand tender but it had like 10 plug in points for additional pigtails. That way each battery got the respective amperage.

Im sure you know this but every battery to piggy back onto a single battery charger is going to reduce the amperage it puts into each battery. So if its 10 amps with 2 batteries hooked up each battery will draw 5 amps. 3 batteries will be 3.33 amps and so on effectively reducing the charge strength.

At least if Im referencing my electrical properties correctly.
 
When I used to run a motorcycle shop back in the day, we used to sell a lot of the battery tender jr's, they were cheap and worked great on bikes quads etc. One of my customers asked the exact question you did, after some research and some testing, we determined that at least the "jr" model won't successfully do 2 batteries.

They do make other models for multiple batteries http://www.amazon.com/Battery-Tende...t-Management/dp/B000NCOKV0/ref=pd_sim_auto_15. Here's and example of a 2 bank model.
 
Stomis said:
When I worked at advance auto many moons ago we had that exact brand tender but it had like 10 plug in points for additional pigtails. That way each battery got the respective amperage.

Im sure you know this but every battery to piggy back onto a single battery charger is going to reduce the amperage it puts into each battery. So if its 10 amps with 2 batteries hooked up each battery will draw 5 amps. 3 batteries will be 3.33 amps and so on effectively reducing the charge strength.

At least if Im referencing my electrical properties correctly.
Click to expand...

I am not very familiar with the tenders. Just concerned the processor circuitry in them can handle it. None of the product descriptions that I have read really say much about it.

Yep, aware of the amps being cut in half.
 
jt512 said:
When I used to run a motorcycle shop back in the day, we used to sell a lot of the battery tender jr's, they were cheap and worked great on bikes quads etc. One of my customers asked the exact question you did, after some research and some testing, we determined that at least the "jr" model won't successfully do 2 batteries.

They do make other models for multiple batteries http://www.amazon.com/Battery-Tende...t-Management/dp/B000NCOKV0/ref=pd_sim_auto_15. Here's and example of a 2 bank model.
Click to expand...

Looked at that one to and then the question became, do the batteries then need to be disconnected from one another? Still researching that one to.
 
cybrfire said:
Looked at that one to and then the question became, do the batteries then need to be disconnected from one another? Still researching that one to.
Click to expand...

Hmm, like in a dual battery setup ........ I'm not sure......never really thought about it.
 
Go to their website and download one of the manuals for the one you are thinking about.
I have a couple, and the manual that came with them show them handling more than one battery and the ways to do it.
I use them for relatively short term charging.
Such as keeping the battery up on the pontoon boat that gets used about every other weekend, and if one of the cars is not going to be run for a while.

For long term use, I do it differently. I'm sure they would do fine for that also, but for things like my big genset, I use a marine dual battery maintainer/charger.
This model.
http://www.amazon.com/Marinco-Intel...F8&qid=1341457307&sr=8-1&keywords=GUEST+16202

I can leave it hooked up to my batteries for years with no problems. The nice part about this model, is that the two outputs are totally isolated. I have them hooked to my two batteries even though they are hooked together in 24volt series.

The positive lead of one half the charger is hooked to the negative lead of the other half, and it does not care.
Both batteries get charged and maintained separately.
 
Ah, finally found this.


series9.gif

Figure 9: Two Batteries in Parallel, One Charger
Batteries connected in series strings can also be recharged by a single charger having the same nominal charging voltage output as the nominal battery pack voltage. In Figure 8, a single 24-volt charger is connected to a 24-volt battery pack.

In Figure 9 we see a pair of 12-volt batteries connected in parallel. This 12-volt battery pack is connected to a single 12-volt charger. Note the blue wire designated W1. The purpose of this wire is to balance the voltage drop evenly across both batteries and each wire during charging. This is not critical for lower current chargers, but when you start to get into the 10 amp and above range, the voltage differential can be significant. The blue wire W1 must be connected to the opposite end of the battery pack as the black wire at the top of the battery pack.

When batteries are connected in parallel, only use one charger. Do not connect a charger to each battery, unless you break the electrical connection between the batteries. The reason is that the chargers will very likely complete one or more their charging subroutines (charge modes or stages) at different times. That means that each charger would be trying to bring the battery pack to a different voltage level. Depending on how the chargers are configured to prevent a reverse polarity connection, the charger with the lower voltage output could possibly draw current from the charger with the higher voltage output, or even from the battery pack that it is trying to charge. If the chargers' reverse polarity protection mechanism includes a solid state, unidirectional, voltage controlled, current switch (like a diode), then this is not a big problem.
 
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