Trying to set a "rebulk voltage"

[yodamota]

So we now have a solid state relay hooked up to the aux function on our outback power charge controller. The aux control is our water heater, it pulls around 800 watts. The issue I am having is the dam thing will stay on until the battery voltage becomes very low. Since there is no "aux" timer. As long as the charge controller is in float, the aux will be on, which means the water heater stay on until we almost have no solar coming in. I wish I could set it to shut off at 5 pm but no such option exist.

Anyways it means every night we go in with low batteries. I haven't found to much info about what to set the rebulk voltage to. It was set to 24.2vdc I just changed it to 24.6vdc. Does anyone have a more educated answer? The default is 24vdc.

 

[sunshine_eggo]

Sounds like you just need to set rebulk to something you're happy with.

Like, what is your battery voltage at 5pm? Set rebulk to 0.1V above that?

A fully charged 24V lead acid will be around 25.2-25.8V after resting for 10-24 hours with no loads or charging. If resting voltage reads that or higher shortly after load is removed, you know you're fully charged.

 

[yodamota]

right now its claiming to be 25.23vdc. granted it hasn't rested.

sounds like there isn't a formula or anything like that to follow

 

[sunshine_eggo]

I'm seeing 25.24V@0A. That's a pretty high state of charge. With no load on it, voltage should rise. If there's a small load on it, and it's sitting at 25.24V, it's still at a high state of charge.

Problem with formulas is they need to have good input to give good output. There's no one size fits all solution as all systems are different with different use profiles.

It seems pretty simple... If you'd like to have it turn off at 5pm or some other time, check your voltage at 5pm, and set that as your re-bulk. Tweak it until it works for you.

 

[yodamota]

thank you for the advice sunshine!

Ill look into that. We start to cook around 5pm in order to use our induction plate with the remaining solar on the panels. As of now we have solar on our west facing panels until 6pmish. I was worried using the induction plate and the water heater was to much. With the induction and the water heater we are closer to 1500-1800 watts.

 

[DIYrich]

How about a timer that controls a relay to disconnect the water heater at 5pm, and reconnect at 5am (or whenever).

 

[yodamota]

Well what i would control is the 12v signal to the relay. Does anyone know of a good timer?

That way if we are not in float the relay will not be energized. despite the timer saying it can be on.

We have gotten some timers from canadian tire which crap out after two years.

 

[2strokeforever]

Sounds like you could use one of these.

Any interest in something like this?

It figures out how much excess solar power you have and will "talk" to anything that will accept a 0-5v signal, or a PWM signal. SSR, VFD, ect. It will throttle your load to use as much power as possible, but back off instantly once something wants the power, turn on the kettle, charge...

diysolarforum.com

 

[yodamota]

my other idea is a manual switch which shuts off the 12v signal to the ssr. I could interupt the signal from the charge controller. Problem is I would want the switch to turn back on manual so incase we forget it on. It will turn itself on.

does such a switch exist?

 

[E. Cho]

In the Outback FM80 user manual, page 26, under Aux info, one of the Aux Menu settings is a Low Voltage Disconnect and says this:

"Low Batt Disconnect—activates/deactivates the AUX load(s) when a user-determined voltage and time levels are reached."

Page 38 explains how to Set it.

It seems like it would do what you want and avoid the ReBulk setting? Have you read this and tried it?

Could you post a link to the relay that you are using / purchased?

Could you use a 120V Smart Plug to also control the water heater On/Off state? I use Lenovo smart plugs with energy monitoring, bought on sale and they have been brilliant. They have a manual button or app user timers and I can also control them via the app from anywhere, as long as my home WiFi is connected to my internet modem. Only had them 18 months though. But there are other more well regarded smart plugs like SonOff, Emporia and Kasa.

 

[yodamota]

In the Outback FM80 user manual, page 26, under Aux info, one of the Aux Menu settings is a Low Voltage Disconnect and says this:

"Low Batt Disconnect—activates/deactivates the AUX load(s) when a user-determined voltage and time levels are reached."

Page 38 explains how to Set it.

It seems like it would do what you want and avoid the ReBulk setting? Have you read this and tried it?

Could you post a link to the relay that you are using / purchased?

Could you use a 120V Smart Plug to also control the water heater On/Off state? I use Lenovo smart plugs with energy monitoring, bought on sale and they have been brilliant. They have a manual button or app user timers and I can also control them via the app from anywhere, as long as my home WiFi is connected to my internet modem. Only had them 18 months though. But there are other more well regarded smart plugs like SonOff, Emporia and Kasa.

So I am not quite sure if I can have two aux setting set up. My understanding is only one functions at a time. However I could be wrong. any chance you know? I have read the manual several times. and always have it open haha!

here is the thread i started to set up the relay https://diysolarforum.com/threads/charge-controller-aux-output-setup.59967/

Ill look into those suggested "smart plugs"

turns out only one can function at a time.

 

[E. Cho]

??? I read that you only wanted to use the relay to control the water heater, so isn't that just one function and so should do what you want either by a voltage set point or a timer? Or I don't understand what you are requiring. Thanks for the thread link.

 

[yodamota]

no the relay is already controlling the water heater. When the batteries are in the float stage. the water heater is on. when the batteries leave the float stage. the relay shuts the water heater off. I was trying figure out the rebulk voltage so that the water heater would shut off around 5pm or so.

Someone suggested a timer to control the relay.