Re: (ET) Elec-trak Digest, Vol 13, Issue 78

["Robert" <euclid delhitel net>]

Hi David,
I imagine that's the execution speed, right? Pics take 4 cycles to execute 
one instruction in assembly. So a 4 Meg clock runs at 1 Meg execution rate. 
That's in assembly, once you start to use higher language programming, 'C', 
BASIC, etc. the speed goes down. An easy way to check is to look at the 
execution speed in your ICE program. With that said, even if you're using 
'C' I doubt you'll  have any problems even at a 10K execution speed.

Also you'll pick up speed if you take less samples, battery charging is not 
that critical. Are you sampling each battery or the bank?

Rob

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Subject: Elec-trak Digest, Vol 13, Issue 78

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Today's Topics:

  1. Re:  DIY Smart Battery Charger (David Erskine)


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Message: 1
Date: Thu, 2 Jul 2015 12:29:20 -0400
From: "David Erskine" <d_erskine att net>
To: <Elec-trak cosmos phy tufts edu>
Subject: Re: (ET) DIY Smart Battery Charger
Message-ID: <ED60F5619D43421692ED36D651E713E4@OLD>
Content-Type: text/plain; charset="iso-8859-1"

Sorry not to have replied sooner.

I did get to talk with friends regarding noise on the mains from an ET 
charger system. I was unaware of such possibility and still don't know how 
to eliminate such. Is there a ready-made filter for this problem?

Regarding Sparkfun product #SEN-09028 90 Amp voltage & current sensor: If 
the Picaxe command "readADC10" is used the 90-amp current is read out as a 
10-bit digital number. Thus the 90 amps are divided into 1024 parts; or 0.09 
amps per division. This seems sufficiently sensitive for a charger system. 
And the breakout board spits out a digital reading of a max voltage of 52 
volts; which also can be divided into 1024 bits. It would seem that this is 
an ideal item for our purpose - except that it reads current in only one 
direction. So for amp-hour tracking this has to be overcome.

One of the many nice features of using a microprocessor is that the 
self-discharge could be handled by periodically checking the 'idle' battery 
voltage and applying a 'booster' shot. After all, I am after the automated 
feature[s] of using a microprocessor. One member of this forum voted for 
'don't bother - just use the existing charger'. But for good battery care 
this, in my estimation, requires manual checking in some manner. I have been 
doing this but would like to have some degree of automation. And the 
existing timer, I feel, is insufficient. If GE had microprocessors 
available, would they have incorporated them in their design. I think so.

Regarding amp-hour tracking sampling speed: Even the inexpensive Picaxe 
operates at some 10,000 commands per second. And there are -X models which 
may be faster. I hope that any algorithm would still be fast enough. They 
offer a datalogging board, which I bought. Will explore sampling rates on 
this. Memory capacity seems to be the limitation.

I welcome any thoughts.

Cheers, David

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