[PSUBS-MAILIST] Battery Question

Mon Jun 20 08:45:12 EDT 2016

Just to clarify, the drawing shows the contents of ONE battery pod. There
are two such pods, connected with a battery switch so I can use one, the
other, or both.

On Mon, Jun 20, 2016 at 8:43 AM, Alec Smyth <alecsmyth at gmail.com> wrote:

> I was planning to do your #2. Hopefully this is "cross string"?
>
> [image: Inline image 1]
>
> Thanks,
>
> Alec
>
> On Mon, Jun 20, 2016 at 7:19 AM, James Frankland via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>
>> Thanks Guys.  I need to absorb this information.  A lot to read here.
>>
>> I don't really understand the "cross string" thing either.  I will attach
>> this picture of the 2 possible ways of doing it (for my application) and
>> maybe Sean or someone can comment?
>>
>> I currently have the batteries rigged in Config 1, but have been advised
>> (possibly incorrectly) to use config 2.  Apparently this is how most high
>> power UPS systems are configured and allows redundancy if 1 pair fails.
>>
>> Any ideas?
>>
>> Thanks
>> James
>>
>>
>> 
>>
>> On 19 June 2016 at 23:56, Sean T. Stevenson via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>>> 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 un! balance 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
>>>>>>
>>>>>>
>>>>>>
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>>>>>>
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>>>>>>
>>>>>>
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>>>>>
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>>
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