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Two 4d's - same as one 4d ?

PostPosted: Fri Apr 29, 2011 6:23 am
by dfansler
I have a complete AP charging system, including an EMON II. I replaced the pair of aging 4D batteries last summer. I have been at the boat this week doing the annual bottom job, etc. I noticed that the EMON II indicated I only had 200 AHr of capacity rather than the typical 380 AHr for this system.
So I have done some experimenting.
Step one – I discharged the system at about ~15 A until it reached 50% and then recharged – it charged up to 200 AHr.
Step two – Since the batteries are connected in parallel with a couple of 2/0 AWG jumpers, I disconnected one of the batteries from the system and then again discharged the battery at ~15 A until it reached 50% and then recharged – back up to 200AHr.
Step three – switch batteries in the system and discharged and recharged as before – back to 200AHr.
Ok, sort of strange so I reconnected the batteries together. After a few hours, I measured the voltage of each battery at their terminals with a DVM. There was a slight voltage difference between the two batteries. Thinking that the jumpers may have developed some corrosion resistance, I made new jumpers. The voltage reading at each battery is now identical. So, I discharge the system, with both batteries, recharged it and you would never guess what they recharged too – yeah 200AHr.

So it appears that one 4D is equivalent to two 4Ds –
I would appreciate if someone could clear this mystery for me!
Thanks,
David

Re: Two 4d's - same as one 4d ?

PostPosted: Fri Apr 29, 2011 11:45 am
by Coulomb
Is the Emon set to 380 Capacity?

Did you record total Amp-hours consumed from the last set of batteries and then do a total reset for the new set?

Re: Two 4d's - same as one 4d ?

PostPosted: Fri Apr 29, 2011 12:31 pm
by dfansler
I have not set the EMON - I was under the impression that it would determine the bank capacity thru discharge/reacharge - will do.

I do not recall if I did at total reset or not - I will do so now as I set the AHr.
Thanks,
David