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Hugh

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Joined: 26/11/2006
Location: Canada
Posts: 41

Posted: 04:09pm 21 Feb 2007

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Would there be a problem charging like voltage & current charge limits with differnt amp hrs. at the same time.

7ahs with 24ahr
hugh

thnxs allways

WindChopper
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Joined: 08/02/2007
Location: United States
Posts: 15

Posted: 01:03am 22 Feb 2007

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Hi Hugh

A: Yes / No / Maybe

My opinion only .... not carved in stone ....

If we are talking about Float Charging ( Maintaining ) essentially charged batteries and you use isolation, yes you could.

In general you should match batteries when charging or discharging batteries that are series or parallel connected.

If you intend to CHARGE ( as opposed to maintain ) the batteries which may be in various states of discharge I would not do that.

The batteries will have unequal voltage / current demands with the highest capacity and or/lowest state of charge battery dragging down the lower capacity and/or highest state of charge battery until they reach equilibrium.

You could use the isolation diodes and series resistors that I had mentioned to you earlier, but as the current demands go up you begin to need some serious resistors and some serious charger current capacity.

Most mfrs. do not recommend mixing old and new batteries in a pack ( which is really mixing capacities ) or mixing aHr ratings as its hard to control the charge.   In the case of a vehicular dual battery system, implemented without an isolator, the presumption is that the batteries are identical and that they have the same state of charge/discharge.

Having said that .... I have used a higher capacity unregulated supply driving multiple LM317s ( Self Limits at ~1.5A, a nice safe slow charge current ... set to 13.6 vdc float voltage ) to charge multiple battery systems ( each on its own LM317 ).   Each battery does its own thing, until charged.   Not a simple or cheap solution, but a controlled one.

Again .... in my opinion ....

Good luck with your project.

Russ

Hugh

Regular Member

Joined: 26/11/2006
Location: Canada
Posts: 41

Posted: 12:28am 25 Feb 2007

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Sorry it took so long to get back,life in the big city, har har,thanks for the info.
basically charge like batts if at all possible.
Thought I'd save money on another charger. Scottish ya know.What I'm really doing is trying to get enough stuff together to get started in early spring and couldn't pass on a free storage source.

I'm really interested in the mintos wheel and incorporating it into my hot water supply. Any input???????????
Hugh

thnxs allways

WindChopper
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Joined: 08/02/2007
Location: United States
Posts: 15

Posted: 11:37am 25 Feb 2007

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Life ....
Busy ....
what a concept !

Let's see, its now 4:53 am cst and that's when I find the time .... Know it all too well !

Re: Batteries - for what its worth
Once you identify batteries of at least roughly equal capabilities, you can loosen up on the charging / discharging cautions.   Let's assume that you have 6 out of 10 of those 24aHr batteries that all measure ~85% aHr capacity under test.   You could parallel those 6 in a bank fairly safely.

I just do not like mixing low and high rated ( 7 vs 24 ) capacity batteries.    After you charge your new acquisitions, you might want to perform a load test to at least roughly estimate their useful life expectancy.   You could do this with a relatively simple Picaxe08m circuit to discharge them to a specific Volt per cell (1.0 or what ever you feel comfortable with) and then mark them for matching into banks.

This does not need to be "Lab" standard measurement, only "Hugh" standard.   That is, a consistent personnel ref. point rather that "absolute" reference.    Load each fully charged battery with an auto head lamp / tail lamp or whatever load matches their rated capacity and measure time to reach your cutoff voltage.   You then record each with a 3.5 "Hughs" or whatever number.   Then match up the Hugh numbers.   +/- 5-10% probably ok - would not mix 25% with 75% though.   More of a problem with series than parallel connections as in series you will start to damage the lower capacity battery if you over discharge ( you only have the lowest capacity as the limiting factor ).

Re: "mintos wheel"
Not a clue .... did a quick google side trip .... ( could be the reason that I never have enough time to .... ) .... I profess complete ignorance on that one.   I did see a "Mentos" display on TV once though .... You may want to start a new topic on that one here and/or on the Otherpower board.

Re: Sick Humor
I apologize.

Invent the 36 hour day and you solve all our problems.

Good luck with the project.

Russ

Hugh

Regular Member

Joined: 26/11/2006
Location: Canada
Posts: 41

Posted: 12:07pm 25 Feb 2007

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thanks again, on further investigating the Mintos sounds like its a better breath mint than a RE source
Hugh

thnxs allways

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