Help me figure out my house battery system...

[Joe917]

Good to see progress. Just so you know, and I am being picky here, those lugs are the wrong size for your battery terminal. The hole in the lug should be the same size as the bolt. At the very least you should add a washer and then a lock washer with a nut or a washer and a nylock. Get rid of the wing nut. You should also hit the heat shrink again as it has not sealed properly. Follow the wire and where it rubs anything tie wrap a chafe guard over it (use a piece of rad hose split lengthwise). Two steps forward one step back, this is the learning process.

 

[HoboJen]

thanks for the tips, Joe! I didn't notice the eyelet size being wrong.. the guy who did it told me he did not like the wingnut and would have preferred a washer and nut but he didn't have a washer. He did give me an extra nut and screwed it onto the negative terminal and told me to keep an eye on the wingnut.

I'll hit the heat shrink again since i have access to a heat gun.

And thanks a lot for the tip about the chafe guard! I had been wondering about that but had no idea what to use. thanks.

I made another appointment with the mechanic on Monday to check out the alternator/battery. Going to take them beer this time.

 

[dwh]

Uh...nothing should be at 2v.

An alternator has a sort of "clutch". It's not mechanical, it's a magnetic field. The voltage regulator turns that field on and off, and that is what causes the alternator to make power or not.

When the alternator is spinning it supplies its own power to "energize the field coil". But when you first turn on the key, and the engine is not running, power has to be supplied from the battery to energize the field coil.

The wire from the battery that feeds the field coil, is ignition switched and usually runs though a light bulb. That is the red alternator warning light on the dash. If the alternator is making power after the engine is started, then no power is being pulled though that light bulb, and the light is not lit.




Your solenoid was connected at the blue circle, and it sounds like they moved the connection to the yellow circle.

Which is fine and should work, but the voltage at the small terminal of the solenoid should be the same as the engine battery voltage with the key on but the engine off [EDIT: actually, sorry, the same or perhaps a bit lower after going through the light bulb), and should be the same (or a bit higher) than the battery with the engine running. (And should of course, be 0v when the key is off.)


Sounds like they probably tapped the right circuit, but likely just got a crappy connection somehow. I doubt that 2v is enough to pull the electromagnet in the solenoid and tie the large terminals together, in which case, the house battery would not be getting tied in, and not getting a charge.

 

[HoboJen]

thanks dwh. I wish I'd noticed if the light was on before I did the battery terminal fix. It was definitely on after the terminal fix but i'm not sure if it was on before that (and after the alternator fix). The power that is running from the starter battery to the back makes me think that the connections on that terminal are fine, and that it's a crappy connection at the alternator... well, more importantly there's only 2 volts flowing back there and that's how it was when i first brought it home, before I did anything else.

this is definitely helpful for when i go back and talk to the mechanic - thanks.

 

[DiploStrat]

I find it mildly surprising that you cannot easily find a key controlled, 12v source under the hood or under the dash. That is what I would recommend. And if you have a solar kit or shore power, then I would not use key control, but would rather go straight to some form of voltage sensing or "intelligent" relay.

And do clean up and fuse all of that wiring; it looks terrible and is not very safe.

Good luck, I fear you have a bit of work ahead of you. The good news is that none of this is very hard and you can build a system that will work very well.

 

[HoboJen]

I find it mildly surprising that you cannot easily find a key controlled, 12v source under the hood or under the dash. That is what I would recommend.

my issue was 1 - I couldn't figure out how to easily get the wire off the alternator - accessing it. and 2 - my mechanic wanted to just switch the spot on the alternator even though i suggested the interior fuse box. I could probably wire this myself, I just don't know all of the technical details... I struggled to find that information... it's like i don't know the right words to google or something.

And if you have a solar kit or shore power, then I would not use key control, but would rather go straight to some form of voltage sensing or "intelligent" relay.

i do have a plug from the inverter/charger. I don't have solar yet, but would like to add it. i don't completely understand what you mean by voltage sensing or intelligent relay, though i feel like i should after all these pages.

And do clean up and fuse all of that wiring; it looks terrible and is not very safe.

Good luck, I fear you have a bit of work ahead of you. The good news is that none of this is very hard and you can build a system that will work very well.

i will. i'm just trying to get a working system to get out of here for a week or two. then i want to do some work on the system after that - like adding fuses, cleaning it up, and hopefully adding solar. i will probably invest in some tools as well... Then onto big winter adventure.

thanks a lot. i am learning, slowly but surely.

 

[DiploStrat]

my issue was 1 - I couldn't figure out how to easily get the wire off the alternator - accessing it. and 2 - my mechanic wanted to just switch the spot on the alternator even though i suggested the interior fuse box. I could probably wire this myself, I just don't know all of the technical details... I struggled to find that information... it's like i don't know the right words to google or something.

Just cut it and forget it. Really.

In your set up you want the heavy, current carrying wire to run from the positive terminal of your starter battery to one side of your relay and from the other side of your relay to the positive terminal of your relay to the positive terminal of your camper battery. (Both batteries must be well grounded to the vehicle frame to complete the circuit.) Assuming that your alternator was properly connected to the starter battery at the factory, and that the previous owner of the truck didn't muck with it, you don't need to connect any wires to the alternator.

The relay or solenoid is very simple; it is simply a remote control switch to connect the batteries or disconnect them. (In fact, you could replace the relay with a manual switch, as discussed here: http://www.expeditionportal.com/forum/threads/130252-does-anyone-use-a-marine-dual-battery-switch I argue against this only as it is easy to forget to combine or separate your batteries but it does work.) You can read up on how a relay works here: http://www.explainthatstuff.com/howrelayswork.html

What do you want to happen? VERY simple: When the engine is running and the alternator is producing current, you want to connect both batteries to it. When the engine is off, you want to be sure that neither battery can discharge the other. (In small systems, the usual concern is that your camper battery might draw down the starter battery.) This means that you do not want them connected together; you want them "isolated."

If you don't want to use a manual switch to connect and disconnect the batteries, what can you do? You can wire up a simple, ignition key controlled system like this: http://www.expeditionportal.com/for...ke-a-cheap-isolated-dual-battery-setup-for-50 In this case, you replace the manual switch with a relay (a remote controlled switch) and control it with your ignition key. When the key is off or in "start" or "accessory", the relay is open and the batteries are isolated (or disconnected). When the key is in the "run" position, that is, your engine is running and your alternator is producing current, the relay is closed and the batteries are connected. At this point, assuming appropriate wiring size and alternator capacity, ALL of your batteries will charge.

All we are discussing is how to get 12v to the control side of the relay and the best way to do that is with a fused wire from a terminal block under the hood or under the dash.

If you don't want to control the relay with the ignition key, there are various intelligent relays or controllers on the market that connect and disconnect the batteries automatically, based on the voltage they detect, time, and a few other factors.

The biggest arguments in favor of an intelligent controller are:

-- NO interference with the vehicle wiring. (GM, for example, requires a diode on the control wire of a relay. Simple enough, but it could void your warranty if you leave it off.)

-- Bidirectional charging. This is not much of an issue for you as you don't have a solar kit, but it is still very nice. Bidirectional simply means that if either battery is under charge, that charge is shared with both.

So, assuming that you do not have a solar kit, but do have an inverter/charger that you plug in at a campsite or in your garage. With a key controlled relay, you will only charge your camper battery. With an intelligent relay, you will charge both the camper battery and the starter battery. Very nice if you live in the frozen north and leave your camper in the driveway for weeks on end.

Hope this is helpful.

 

[HoboJen]

thanks diplostrat... that info is VERY helpful.

i went to the mechanic this morning, for like 5 minutes, and we discovered a couple of things:
- the voltage on the control wire to the solenoid IS around 14 volts, but that is with the wire disconnected. When the wire is connected to the solenoid, it drops to 2 volts.
- the starter battery is charging fine... he thinks there is something about where he wired it that is causing the battery light to go on. he thinks he can move it to a different spot (he explained and i don't remember) that will fix this problem
- the house still isn't charging.

he thinks that maybe the solenoid is bad? he's going to test it tomorrow for me and move the wire again. If this doesn't work I will cut the damn wire and learn how to wire it into the fuse box. And if the solenoid is bad sounds like i want to get an intelligent relay... i don't know much about what i have now, just that it is not a diode isolator but it was hooked up like one.

 

[Herbie]

- the voltage on the control wire to the solenoid IS around 14 volts, but that is with the wire disconnected. When the wire is connected to the solenoid, it drops to 2 volts.

Normally this tends to indicate that the voltage is sagging under a load. Are you using the control wire to drive the solenoid coil directly?

IIRC, a normal 12V solenoid (like the Cole Hersee 200A unit I use) has a coil resistance of ~18ohm, which means there should only be ~670mA or so flowing through the coil (and thus the wire). If you're pulling the circuit down to 2V then there are two possibilities:

1) There is much more than 670mA flowing.
2) The "source" of that control wire cannot adequately supply 670mA and is just sagging down.

Where are you measuring the control wire voltage, on the solenoid end, I assume?
The other side of the coil is connected to ground, right? Can you measure the resistance of the coil itself?
Can you measure the voltage applied to the "other end" of the control wire. Just in case there's something wrong with the wire itself and you're dumping current into heat along the wire itself due to some problem. (i.e. if you see 14v at one end, and 12v at the other end when connected to the solenoid, then the WIRE is soaking up that current, somehow)

 

[dwh]

Ah yea. I forgot about that. When the voltage regulator turns off power to the alternator's field coil, then wired the way your mechanic did it, the solenoid would be pulling power through the light, which would cause it to light up. Since the voltage regulator actually turns on and off really really fast and frequently, that would make the light seem to come on and stay on.

So there's a good reason to not do it the way the mechanic did it.



When we talk about intelligent relays, or Intelligent Battery Systems (IBS), what we're really talking about is a solenoid like yours, but with a little brain added which decides when to activate the solenoid. Usually they just wait until the engine battery voltage comes up a bit and they tie in the house battery. Some just have a timer and wait a while. Others can sense when voltage rises on either side (say you're charging the house battery from shore power or solar) and ties them.

Here's the simplest:

http://www.powerstream.com/battery-isolator.htm


Here's a fancy one with a remote switch to control how it works (always tie, never tie, tie automatically):

http://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A

 

[DiploStrat]

Step by Step

Testing the solenoid is dead easy.

-- Disconnect the load (heavy) wire from the camper battery to the relay at the relay.

-- Check the voltage at the positive terminal of the starter battery. Should be something like 12.5v with the engine off, 14+v with the engine on.

-- Now eyeball the load (heavy) cable from the positive terminal to the relay. Is it securely fastened at both ends? No breaks in the insulation?

-- Test the voltage at the relay where the cable from the starter battery attaches. Should be almost exactly the same as at the positive terminal of the starter battery.

-- Now check the wire(s) to the control side of the relay. If there is only one, then that is the control wire. If there are two, one is the control and one is the ground. The ground must be securely attached to the frame.

-- Disconnect the control wire from everything and test the voltage on the camper terminal of the relay. It should be 0v.

-- Now connect the control wire from the relay to the positive terminal of the starter battery. There should be an audible "thunk" as the relay closes.

-- Test the voltage at the camper terminal of the relay - it should now be the same same as the voltage at the starter battery side.

==============================================================================================

-- If the relay does not close, it is defective.

-- If the voltage difference between the two load terminals of the relay is more than, say, 0.1v, then I would replace it with a larger one that has less voltage drop.

-- If all goes well, then proceed to test the connection on from the relay to the camper battery.

If your mechanic cannot perform these tests, get a new mechanic.

 

[HoboJen]

thanks guys. I got nowhere with the mechanic. Boo on that. He referred me elsewhere and they wouldn't touch it. And my internet has been down which is where all of my resources are for this stuff.

So this is my interim solution. I disconnected every wire from the solenoid (well i left the ground there). I disconnected the positive wire from the starter battery. It is currently taped up and secured on both ends. The house and starter circuits are 100% separated and the house can only charge by plugging in. I charged my house battery using my inverter/charger, and tomorrow I am out of here for a week or so. I will go sparingly on my electricity usage and fingers crossed that I won't somehow manage to strand myself anyway. I measured the parasitic draw on the starter battery and it's 0.01.

When I get back, I'm going to draw up new plans to clean up this mess and redo a lot of it. I think if I had gotten this working, I would just let it go instead of cleaning it up the way it should be (like with, ya know, fuses). I'm considering moving the battery as well... it's one of those fancy batteries that aren't supposed to leak hydrogen, but I think I read that ALL batteries need to be vented. It's also in a place where I can't just load the van with kayaks.. it needs to be in a spot where there is no risk of everything getting wet if I do that. And I want to move the switch and clean up the wiring that goes from the battery to appliances. And maybe add solar... but I'm going to plan everything out before I do anything, and make sure I have all the tools as well. There's a lot of work to do.

Thanks guys - I have learned so much already. And there is still so much to learn.

 

[HoboJen]

hey guys, quick question...

I found the spot in the fuse box that I want to wire to (power windows). I went to the store and I found something like this: http://www.amazon.com/Pico-0956PT-Blade-Add-A-Circuit-Holder/dp/B001QRSBW0

My question is... is 10 amps enough? Is that good or should I be looking for a different product?

 

[HoboJen]

also, had a wonderful full week away. My battery lasted the full week and didn't drop below 50%... of course I only ran lights at night, sink pump for dishes, and roof fan on low for about 6 hours total. Nothing AC at all. Also had the van parked for 5 days straight and it started right up!

But I am really seeing the need for having the alternator as a charge source... hopefully i'll have this figured out soon.

 

[DiploStrat]

Most relays draw very little power; my Blue Sea model even has something called a "coil economizer," intended to reduce the draw when the relay is closed. Guess about one amp or less. But, you may want to use a heavier wire for the heavier insulation, useful for protecting the wire on runs under the hood, etc.