[PSUBS-MAILIST] Battery Question

Sun Jun 19 18:56:59 EDT 2016

If you wire two or more batteries together in parallel by connecting all of the + terminals together and all of the - terminals together (hopefully using bus bars or large and short cables), instead of making your power draw or charging connections to the + and - terminals at one end of the battery string (i.e. at a single battery), you should instead, for example, connect to the + terminal of the first battery in the string, and the - terminal of the last one.

Sean

On June 19, 2016 3:53:58 PM MDT, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Hi Sean,
>
>I'm afraid I didn't get the meaning of "cross string." The other
>mitigating
>measures I'm in compliance with, but could you maybe share a little
>diagram
>of what you meant by "cross-string"?
>
>
>Many thanks,
>
>Alec
>
>On Fri, Jun 17, 2016 at 2:03 PM, Sean T. Stevenson via
>Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>> As far as battery interconnections are concerned, in the absence of a
>> battery / cell management module, it is next to impossible to ensure
>that
>> individual battery voltages stay balanced. That said, you can
>minimize the
>> potential for unbalance by making sure that your parallel batteries
>are
>> connected cross-string, instead of to the terminals of one battery in
>the
>> parallel bank. By this, I mean make the positive connection to the
>first
>> battery in the parallel string, and the negative connection to the
>last
>> battery in the string.  As far as the series connections go, there is
>only
>> one way to hook it up, but you can minimize the unbalance by ensuring
>that
>> every battery is of the same type and capacity, and of the same age
>(I.e.
>> replace all batteries simultaneously). Also, try not to tap off of a
>lesser
>> number of batteries if you need a lower voltage for some purpose -
>instead,
>> use a DC-DC converter powered by the entire string.
>>
>> As for charging, see if a recommended charge curve is provided by
>your
>> battery manufacturer, and source an appropriate charger. The specs
>you
>> listed are straightforward: maximum 2.4 Volts per cell (Implying 14.4
>Volts
>> max for a 12V battery) during charge, with nominal charge voltage
>2.35 V
>> per cell (14.1 V on a 12V battery. Once charged, the float voltage
>must
>> drop to 2.25 - 2.3 Volts per cell (13.5V - 13.8V on a 12V battery). 
>For a
>> 24V system, you would double these values.
>>
>> The maximum ripple spec has to do with the quality of the rectifier
>> output. A good quality charger will have circuitry to create more
>pulses
>> per AC cycle and smoothing capacitors on the output side to better
>> approximate a DC output. The ripple is the distance between minimum
>and
>> maximum peak amplitudes on the "DC" output side.
>>
>> Sean
>>
>>
>> On June 17, 2016 4:53:35 AM MDT, James Frankland via
>Personal_Submersibles
>> <personal_submersibles at psubs.org> wrote:
>>>
>>>  Hi All
>>>
>>> Could anyone give me a hand with a battery charging question.  It
>sounds
>>> simple enough but I seem to be getting conflicting advice all over
>the
>>> place.
>>>
>>> How do I charge my battery banks correctly?
>>>
>>> I have just spent a lot of money on a brand new set of batteries and
>I
>>> don't want to charge them incorrectly.
>>>
>>> The batteries are WING ESL 55-12.  AGM
>>> 12v
>>> 55ah
>>>
>>> On the sheet it gives charging instruction.
>>>
>>> Float 2.25 - 2.30 VPC @ 25deg C
>>> Cycling 2.35 @ 25deg C
>>> Max 2.4 VPC Max Ripple 0.05C (A)
>>>
>>> This seems straight forward enough for a single battery, but I have
>them
>>> configured as a bank which seems to be where the issue lies.
>>>
>>> 2 pairs in parallel, then the 2 pairs joined in series to give 24v.
>>>
>>> I will have to ! charge them as a bank through the 24v output
>terminals.
>>>
>>> I will add the spec sheet of the batteries.  Hope it gets through.
>>>
>>> Any advice appreciated.
>>>
>>> Regards
>>> James
>>>
>>>
>>>
>>> ------------------------------
>>>
>>> Personal_Submersibles mailing list
>>> Personal_Submersibles at psubs.org
>>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>>
>>>
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>>
>>
>
>
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