Low Ah Reading on new battery?

[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 The relay will be wired to break the connection originally made from battery to fuses.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.