Low Ah Reading on new battery?

[Scotsman]

TJ,
He indicated he has the 20A PWM.

Thank you - I've had my questions answered adequately by others - safe travels

 

[Scotsman]

While everything is new I would suggest a battery monitor. A battery monitor keeps track of what goes into the battery and what comes out. These monitors can cost from $20.00 up. Most controllers don't do this job for two reasons. one you likely have more than one way to charge the battery. two, the power out of the battery does not come through the controller. Most monitors use a shunt for power into the battery and a shunt for the lead coming out of the battery. Honestly there is no other way to maintain a log of power state of the battery. Hope this helps.

Thanks so much Kevin,

This really answers my questions and helps a great deal - as do hyour other helpful answers. I'll get that monitor before I ruin my system...

 

[Scotsman]

I missed that; thanks Steve. Just wanted to get a look at the manual and specs on the unit to see it anything else jumped out at me. I think you have it correct that what he’s seeing is input from the solar panel. While this charge controller is a very useful device, I can’t see how it could calculate and display the aH available in the battery. As I see it, it simply manages the charging circuit by passing available power from the solar panel to the battery.

TJ

Thanks TJ - I think I have it all figured out now. I wish the manual would explain this to newbies like me - what the readings actually tell you. The answers I got from Renogy were cut-and-paste auto responses that told me to check my wiring etc...

 

[Kevin D Pem]

Thanks so much Kevin,

This really answers my questions and helps a great deal - as do hyour other helpful answers. I'll get that monitor before I ruin my system...

To be honest I don't have a battery monitor. I believe large enough system does not require monitoring. If you only use an inverter or use the load connectors on the solar controller to limit the draw down of the battery you can't hurt the battery because it will not discharge below 50%. Note that the load terminals only supply 10A so a relay would need to be controlled by those terminals. I can help with a diagram to accomplish that if you need.

 

[Scotsman]

To be honest I don't have a battery monitor. I believe large enough system does not require monitoring. If you only use an inverter or use the load connectors on the solar controller to limit the draw down of the battery you can't hurt the battery because it will not discharge below 50%. Note that the load terminals only supply 10A so a relay would need to be controlled by those terminals. I can help with a diagram to accomplish that if you need.

Just when I thought I was getting everything understood...what a revelation that the battery (I presume) load terminals deliver only 10A - never has that come up before and it confuses me as to why a battery charger, for example, can deliver more than 10A if the terminals won't accept it? My system doesn't have an inverter - it has a converter only - for charging the battery when plugged into shore power (I presume) and for powering the AC outlets in the camper (Of which there are a staggering 7 duplexes in a sleeping space of 13'!) when hooked-up. This is 12V camping otherwise - which is fine because we never use hook-up camping but sometimes charge the battery from shore power at home. I don't understand what a relay is - were we talking about this? Is the monitor we're discussing also a 'relay'?

 

[Kevin D Pem]

In more detail:

most solar controllers have terminals with the following configuration.

Panel Battery Load
+ - + - + -

You can use The load terminals to limit how far down the battery can be drained to protect the battery. The problem is the load terminals can only supply 10 A. If you want to protect the battery with larger loads than 10 A this can be done using a relay. To be clear, you don't need to use this circuit, the idea is to keep the battery safe from going below 50%. The following circuit will work to allow larger than 10 A from the controllers load circuit:

+_____________ ____________Battery +
|| |
Load Coil \ Relay contact
| n.o. contact
-_____________| |_____________ Load RV system +


In all honesty I would prefer a solid state relay for this or a FET but that may be hard to find locally. Horn or head light relays can be found off shelf at any auto store They are limited to 40 A but that should be large enough to supply power to pump and lights, I don't know the demand of the furnace, and that is my largest concern when battery draw down is concerned. Most full time users get rid of furnace and use a radiant propane heater for this reason.

Side note:
Wyo... At the moment I am in Burns, OR. I am thinking of making my way home on the US191 Past Flaming gorge. You are in beautiful territory, I say that with envy as I was born and raised in the state.

 

[Kevin D Pem]

Damn!! the system didn't leave spaces in, guess I will have to make up a drawing.

To Protect the battery the battery plus wire feeding the fuse box will feed the relay contact as battery plus, this is the "com" connection.

The NO connection will feed the fuses of the RV. The relay will be wired to break the connection originally made from battery to fuses.

the converter must still be wired to the battery without disruption or it will not charge the battery.

When you boondock this system will save many batteries, but when connected to the grid it will do nothing.

 

[Scotsman]

In more detail:

most solar controllers have terminals with the following configuration.

Panel Battery Load
+ - + - + -

You can use The load terminals to limit how far down the battery can be drained to protect the battery. The problem is the load terminals can only supply 10 A. If you want to protect the battery with larger loads than 10 A this can be done using a relay. To be clear, you don't need to use this circuit, the idea is to keep the battery safe from going below 50%. The following circuit will work to allow larger than 10 A from the controllers load circuit:

+_____________ ____________Battery +
|| |
Load Coil \ Relay contact
| n.o. contact
-_____________| |_____________ Load RV system +


In all honesty I would prefer a solid state relay for this or a FET but that may be hard to find locally. Horn or head light relays can be found off shelf at any auto store They are limited to 40 A but that should be large enough to supply power to pump and lights, I don't know the demand of the furnace, and that is my largest concern when battery draw down is concerned. Most full time users get rid of furnace and use a radiant propane heater for this reason.

Side note:
Wyo... At the moment I am in Burns, OR. I am thinking of making my way home on the US191 Past Flaming gorge. You are in beautiful territory, I say that with envy as I was born and raised in the state.

OK thanks for all that - is there a radiant propane heater, or type, that you can recommend - and are these designed to fit into the same place as the furnace and be safe in a cabinet mounting? The interior is 7' x 13' - so no room for something free-standing on the floor, for example. I believe the largest draw we have is the furnace fan - but being such a tiny trailer, and we being such hardy mountain people, equipped with warm clothes and bedding - it's used only very briefly - a few minutes at a time. I'll have to find out the actual draw on that fan motor. The only other draw we have is the fridge control panel and a few LED lights which we rarely use as we have headlamps and all sorts of independent solar lights / candles etc. Yes - you're right - we're privileged to live and play in the Rockies - our camper takes us to Mexico or Canada somewhere along the Rocky Mountain chain.

 

[Bob K4TAX]

Thinking on this a little more - yes, I get it now - your explanation of 1 - 2 Amp-hours does make more sense - so no need to go over that again. That's very useful information.
I also meant to add that I try not to draw batteries below 80% - which I understand is 11.8V. - Do you think I'm being over-cautious?

The chart I use shows 100% charge at >12.6 volts. 80% charge is 12.4 volts. Then all the way down to 11.8 volts for 30% charge. This is an area where repeated discharge to these levels, less than 11.9 volts or 40%, will shorten battery life.