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Discussion Starter #1
Hey folks,

I've wanted to ask this question for a while but have felt incredibly stupid
about doing so. An important preface - I'm not an engineer nor an
electrical or electronics expert! My EV is my commuter and not a project or
a hobby.

Ocassionally it happens that you want to charge an individual battery in
your string (specific reason unimportant here). I usually dread doing so
because I feel I have to disconnect the battery cables that connect that
particular battery to the adjoining batteries in the string before doing
so. For example, if I want to charge battery #3, I disconnect the cable
between #2 and #3 and the cable between #3 and #4. One reason I dread doing
this is that, given Roland's and others advice here (which makes good
sense), once I put it back together I have to remember to check the
tightness of the connections for the next few days (and I worry about
forgetting to do so). And, truth be told, I'm also basically pretty lazy.

I'm wondering if it is really necessary for me to disconnect those adjoining
cables? I have a main breaker that I activate while I'm working on the
batteries. This opens entire the 120V circuit. Would it be sufficient to
simply activate the breaker and (without disconnecting anything) hook up my
12V smart charger to the battery in question and start charging? Wouldn't
the open breaker limit the charge circuit to between the positive and
negative terminals of the battery the charger is connected to? Or would I
get some 'spillover' or inteference from the adjoining batteries that are
still connected? Or is this a particularly dangerous and horrible idea?

- Peter Flipsen Jr
http://www..evalbum.com/1974
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Discussion Starter #2
Hello Peter,

You do not have to disconnect the battery from the string while charging it.
I do this about once a month, when I want to bring up the lower battery
voltage up to match the other batteries.

I first charge the pack with the main charger, and then let the batteries
set for awhile. A 6 volt battery at 100% SOC should have a voltage of
6.37V, even letting them set for about 24 hours, they may still read about
6.4V. So put about a mile driving load on them until all of the batteries go
below 6.37V.

It then takes a very short time to charge each battery.

Roland


----- Original Message -----
From: "SLPinfo.org" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, September 17, 2010 8:22 AM
Subject: [EVDL] Really dumb (?) charging question


> Hey folks,
>
> I've wanted to ask this question for a while but have felt incredibly
> stupid
> about doing so. An important preface - I'm not an engineer nor an
> electrical or electronics expert! My EV is my commuter and not a project
> or
> a hobby.
>
> Ocassionally it happens that you want to charge an individual battery in
> your string (specific reason unimportant here). I usually dread doing so
> because I feel I have to disconnect the battery cables that connect that
> particular battery to the adjoining batteries in the string before doing
> so. For example, if I want to charge battery #3, I disconnect the cable
> between #2 and #3 and the cable between #3 and #4. One reason I dread
> doing
> this is that, given Roland's and others advice here (which makes good
> sense), once I put it back together I have to remember to check the
> tightness of the connections for the next few days (and I worry about
> forgetting to do so). And, truth be told, I'm also basically pretty lazy.
>
> I'm wondering if it is really necessary for me to disconnect those
> adjoining
> cables? I have a main breaker that I activate while I'm working on the
> batteries. This opens entire the 120V circuit. Would it be sufficient to
> simply activate the breaker and (without disconnecting anything) hook up
> my
> 12V smart charger to the battery in question and start charging? Wouldn't
> the open breaker limit the charge circuit to between the positive and
> negative terminals of the battery the charger is connected to? Or would I
> get some 'spillover' or inteference from the adjoining batteries that are
> still connected? Or is this a particularly dangerous and horrible idea?
>
> - Peter Flipsen Jr
> http://www..evalbum.com/1974
> -------------- next part --------------
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>

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Discussion Starter #3
SLPinfo.org wrote:

> Ocassionally it happens that you want to charge an individual
> battery in your string (specific reason unimportant here). I
> usually dread doing so because I feel I have to disconnect
> the battery cables that connect that particular battery to
> the adjoining batteries in the string before doing so.

[...]

> I'm wondering if it is really necessary for me to disconnect
> those adjoining cables?

Nope.

If you want to use the 12V smart charger while the big pack voltage charger is running, then you need to ensure that at least one of the two chargers is isolated (i.e. output isolated from the AC line).

It is possible for a smart charger to get confused if you run it while running another charger into the same battery (or battery pack) at the same time, but as long as no more than one of the chargers is unisolated there is no need to disconnect any battery cables.

Hope this helps,

Roger.


Probably not. You need to confirm that your smart 12V charger is isolated (i.e. the output is not directly

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Discussion Starter #4
Was not even considering running the main charger at the same time.

Peter

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Discussion Starter #5
[email protected] wrote:

> Was not even considering running the main charger at the same time.

No problem, just wanted you to understand that while you don't have to disconnect anything to use the small one alone, you do need to be sure about the isolation issue if you ever want to run both.

(Even if you don't plan to, you may forget and plug the other charger in while one is already running.)

Cheers,

Roger.

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Discussion Starter #6
Let's take this a little further.

Is it okay to charge with the pack charger and have the 6 or 12V charger ON at the same time, if it is isolated? Point being, that when the pack charger times out the smaller one would continue. I'm using a Delta-Q for pack,and BatteryMinder 12V's.

Dave

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Discussion Starter #7
Dave McWethy wrote:

> Is it okay to charge with the pack charger and have the 6 or
> 12V charger ON at the same time, if it is isolated? Point
> being, that when the pack charger times out the smaller one
> would continue. I'm using a Delta-Q for pack,and BatteryMinder 12V's.

Your Delta-Q charger is isolated, so you can safely run both it and a 12V charger at the same time. If the 12V charger is isolated, then you can run more than one of them, with or without the Delta-Q running.

I'm not familiar with your specific 12V chargers, but I am familiar with your Delta-Q charger. The Delta-Q is an "intelligent", microprocessor-controlled charger; if you run one or more 12V chargers at the same time, it is likely that their presence will result in the Delta-Q not charging as it was designed to. If your 12V chargers are microprocessor-controlled, then running the Delta-Q at the same time may interfere with their proper operation as well.

I would suggest that you allow the Delta-Q to run to completion on its own, and only run the 12V charger(s) on their own afterwards. Or, run the 12V charger(s) first and the Delta-Q afterwards, depending on your preference. Running multiple chargers at the same time works best when the chargers are "dumb", or when the chargers were designed to be operated together.

Cheers,

Roger.

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