[PSUBS-MAILIST] Battery Question

Mon Jun 20 08:43:02 EDT 2016

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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>>>>> Personal_Submersibles at psubs.org
>>>>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>>>>>
>>>>>
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>>>>
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>
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