[PSUBS-MAILIST] Battery Question

Mon Jun 20 08:26:15 EDT 2016

James,I like option two for the reason you mention. My first thought is to have a battery bank switch but this eliminates the need for that, unless you want to isolate one bank for get home safety.Hank 

    On Monday, June 20, 2016 5:20 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?

ThanksJames 

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! balanceby 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.  AGM12v55ah On the sheet it gives charging instruction.  Float 2.25 - 2.30 VPC @ 25deg CCycling 2.35 @ 25deg CMax 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. Iwill have to ! chargethem as a bank through the 24v output terminals. I will add the spec sheet of the batteries.  Hope it gets through.
Any advice appreciated.   RegardsJames  
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