(ET) Battery Charging

["Robert" <euclid delhitel net>]

David,
I'm retired now too (my wife doesn't think so, funny how that works!) I do 
Atmel's AVR's in assembly, sometimes floating point math in BASCOM (which is 
sort of BASIC) or C. Charging algorithms aren't that hard. You basically 
have to figure Bulk, Absorb, Float and Equalize ( you can get the info from 
Trojan) along with the time each phase runs. With some of the chips from 
Linear it's pretty straight forward. You might run into problems with 36 
volts which may be a little high for SMPS buck controllers which makes my 
plan to charge each battery individually a little easier. I'll post the 
circuits and Hex files for those who can programs uC's but right now I'm in 
just finishing a design for my editor so it might not be for a month or so, 
I want to try and design a windmill too this summer but I do expect to get 
to the ET's at some point.
Rob

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Today's Topics:

  1. Re:  DIY Smart Battery Charger (David Roden) (David Erskine)
  2.  Found the E20 speed problem (CZ)
  3.  uC's (Robert)
  4. Re:  Found the E20 speed problem (jlantonucci comcast net)


----------------------------------------------------------------------

Message: 1
Date: Sun, 21 Jun 2015 14:16:31 -0400
From: "David Erskine" <d_erskine att net>
To: <elec-trak cosmos phy tufts edu>
Subject: Re: (ET) DIY Smart Battery Charger (David Roden)
Message-ID: <996671AF0CE3498ABF1CAB4645ABCF26@OLD>
Content-Type: text/plain; charset="iso-8859-1"

David,

Thanks for the prompt and through reply.

I too am not an EE and took to microprocessors only after retiring; and only 
those programmable in Basic. I took to them at first for use in datalogging 
strain gage data [never completed]. The Picaxe especially is inexpensive 
[the 08M2 costs some $4] and has many features [ie. built-in 
analog-to-digital conversion]; as well as an extensive forum. If interested 
smoke out their site.

http://www.picaxeforum.co.uk/

My main reason for trying to get some group design help is twofold:

Design the circuit for the 36-volt battery bank

Come up with the best algorithms using the available logic features of the 
Picaxe/Pbasic.

The Picaxe [-M2] accepts a Vdd voltage ranging from 1.8 to 5.5 volts. Using 
5.0 volts the ADC input has an upper limit of 5 volts. If the battery bank 
upper limit is, say 50 volts then the voltage divider should consist of, 
say, a 10k and a 1k resistor pair. Correct? A pot between them sounds good. 
The other way is to program in a conversion variable.

A thermistor could easily be inputted; but there are linear temperature ICS 
that, I feel, would do a better job. Need the equation however. And need to 
go to a bigger Picaxe IC for additional ADC inputs. The cost difference is a 
dollar or two. See the two US distributors for availability and costs. I 
like the 18M2.

The 'sleeping' time or times [as a function of battery voltage?] is up to 
us. Need a contributor here too. For an initial design should we consider 
the use of the existing on-board charger with a set of good capacity flooded 
lead acid 6-volt golf cart batteries?

The available processing power is well beyond the referenced article 
design.

Charging current: My ET uses a 20-inch length of #6 gauge copper wire to 
sense operating current. But "Sparkfun" offers a 100+ [have to look it up] 
amp current sensor for some $20. Is that worth it? And, again, someone to 
draft the algorithm - thinking Basic.

So, again thanks for your input. I think it would be neat to come up with a 
group design.

Thoughts?

Cheers, David