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Offgridshed
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Joined: 06/01/2016
Location: Australia
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Posted: 08:25pm 06 Jan 2016

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Hi guys,

Just joined the forum after years of looking around the site and I'm looking for some advice/opinions.

I have a number of off grid 2v 1000ah batteries. I have one bank set up as a 32v bank and am charging it with an early lighting plant generator.
I've been working for some time now on replacing all the original electro mechanical gear that made it fully automatic (and is missing) with modern components and an Arduino.

I'd like to put some protection in the charge line. I have a solid state relay that the arduino will switch to allow charging and the timing of this is critical as the generator will motor if connected too early (and cook the relay - don't ask how I discovered this

). If working properly there should never be a problem, but I'm thinking some further protection (diode? ) would be wise.

Working voltage is 36v 20a.
Any suggestions?
Cheers
Chris

yahoo2

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Joined: 05/04/2011
Location: Australia
Posts: 1166

Posted: 03:44pm 07 Jan 2016

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I assume from what you have written there is no bypass to a dump load in this setup.

I'm confused, no wait... maybe I'm not...

Offgridshed
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Posted: 05:36pm 07 Jan 2016

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Correct.

yahoo2

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Posted: 08:21pm 07 Jan 2016

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Hmmm, its gunna be tricky. My first go to solution is some lengths of thick soft tie wire and some insulators and a fan and build a cheap dump load. If you dont want to do that Im not sure I can think of a totally foolproof solution.

what voltage and amps is your SSR rated for and how much heat does it punch out. Only reason I am asking is the ones I use for 24volt stuff are only rated to 32v and they would be on the ragged edge even with a big heatsink and fan. Does 36 volts fully charge your batteries? it seems a bit low to me. although its about right for 15 gel cells.

yahoo

I'm confused, no wait... maybe I'm not...

Offgridshed
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Joined: 06/01/2016
Location: Australia
Posts: 7

Posted: 09:45pm 07 Jan 2016

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Yahoo, the ssr was/is rated well above the voltage. The one I cooked was 5-110v dc, 60a, the replacement is 5-60v dc, 40a.
I cooked it because it was switched when the generator wasn't running and it tried to motor through the relay at I'm guessing 100a at least. (My fault)
I don't need to dump any load, I just need to prevent any current flow back from the batteries in the event the relay is accidentally switched without the generator running.

You may be right about the charge voltage. I couldn't remember the charge rate for them. I think it's 2.36v per cell? They're not gel batteries, but big old 70kg lead some things, (I can't remember, but I think not just not standard lead acid, maybe calcium? I can't see a label to check )

The other two 24v banks I have will just get charged manually by me with no automation, so no real problem.

Cheers
Chris

yahoo2

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Posts: 1166

Posted: 03:17am 08 Jan 2016

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OK I thought you was spinning the generator with the relay open. I am surprised that it doesn't have a rectifier or diode already. Just to be clear we are talking about a commutator style DC generator?

Most stuff I work on that is wet lead acid is closer to 2.46 volts/cell to reach the end of absorption

I'm confused, no wait... maybe I'm not...

Offgridshed
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Posted: 01:01pm 08 Jan 2016

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Yahoo, it's a shunt/series wound dc generator. Everything was controlled by two main relays and an electro mechanical governor. This included current sensing, auto starting and stopping, cut out and over charge protection. Everything except the governor is missing from the control box.

I'll see if I can get to a label for more info.

Cheers
Chris

Offgridshed
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Location: Australia
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Posted: 07:23pm 10 Jan 2016

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Does anyone have any diode recommendations?

Downwind

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Joined: 09/09/2009
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Posted: 04:06am 11 Jan 2016

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Where are you located as your profile is blank to your location, I do have some 100+ amp diodes, i just don't recall the actual rating of them.

Then again a small diode with some monitor circuit should do the same as a big protection diode.

Pete.

Sometimes it just works

Offgridshed
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Posted: 12:38pm 11 Jan 2016

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Pete, I'm in Sth Gippsland in Vic.

Offgridshed
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Posted: 10:00pm 13 Jan 2016

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On a side note to this same system..
If a generator is rated at say 25 amps, 40v, and it is running and regulated to say an output of 29v, can you safely draw more amps or is 25 the safest maximum?

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