[PSUBS-MAILIST] Battery Question

[Alec Smyth via Personal_Submersibles]

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
>>
>>
>>
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