House Battery Testers - Page 2

mikestead · 12-21-2007, 08:25 AM

All good advice, Scatter. Thanks for the chart. I still need to find an inline inverter for our 550W microwave. Haven't seen a cheap inline inverter with that much capacity. So there shouldn't be any microwaving on this trip. Don't have a TV but thought a small efficient 12v would be nice. I think this SMB has the concealed antenna option, because there is coaxial cable running up the corner of the penthouse, disappearing into the top of the penthouse.

Mike

**daveb** · 12-22-2007, 04:04 PM

Scatter, not to disagree but the latest info I got on AGM batteries was you should keep them fully charged as much as possible. I know on my bass boat it was best to let wet cell batteries discharge to a lower state before recharging, but the new rule with AGM's are to charge whenever possible. The new boats charge the trolling batteries whenever the motor is running. Is there something I am missing? Thanks ...Dave B

scatter · 12-23-2007, 10:12 AM

Not at all Dave - I agree. I'm not sure what part of my post indicated otherwise. However, if one is boondocking for a few days sans solar or generator, it won't hurt to use the AGM down to 75-80% of it's rated capacity. That's what they're for. But, batteries are rated for only so many cycles. You'd have to check with the manufacturer on what theirs is and to what level, but you will get many more cycles if each one is only draging the battery down say 15-20% then if you bring it down 40-60%. If ones overnight usage continuously really sucks a battery down, they will have to accept the fact that the battery won't last as long, or add another battery so the total capacity is greater. That way where you used to use 40% you will now only draw down 20%. But, you're buying two batteries instead of one and have to find a place to store it and lug around the extra weight.
I'm not an expert on this. I've had some experiance with solar and designed, built and maintained several systems for folks in Baja, but I only "know" what I read and what I've experienced.
Personally, I have one AGM in my rig and have solar panels on the roof. If I don't come close to filling the batteries everyday, I run the engine for awhile. My 2 cents (more like 6 cents) worth.

Jeffrey · 12-23-2007, 02:29 PM

That chart seems reasonable, but why then do my batteries top off at 14 volts when charged from my 2 panels?

scatter · 12-23-2007, 06:14 PM

That's the voltage your charger controller is set at. Pretty common setting. If you set the controller at 12.7 volts it would take forever to reach a full charge. Same as the alternator in your rig. It is set up to charge your starting battery at somewhere around 14.5 volts. If you check your batteries after they have been sitting an hour or so with nothing coming in or out, you should see a reading of around 12.7
Things were a lot simpler when there were no batteries in a vehicle and there was just a crank on the front. And, NO I'm not that old

....but getting there

philrod · 12-23-2007, 07:39 PM

Scatter, how many panels do you have? I have 1 panel & 1 AGM and my boondocking this winter has led me to think another panel might be a good idea. I got the impression from Fresno that 2 panels=2 batteries, but don't see why that would be. I would think the the controller could handle 2 panels & 1 AGM. i may wait until i get in some warm-weather boon-docking before i decide.

Philrod

'07 E350 V10 RB50

scatter · 12-24-2007, 10:18 AM

Philrod - I have three of the Solara panels at around 65 watts each and one AGM. My only power useage is the small Norcold fridge, lights in the evening, water pump, and occasional playing of some sounds. The most I've ever drawn down my AGM overnight is 35 amp-hours and the panels have no trouble replenishing that on the average day where we camp. [this is where a meter like the Xantrax XBM really pays off. Not cheap, but it's like a fuel gauge and tells you how many amp-hours you have taken out of your battery and you can check the meter during the day and watch the battery fill up

- pretty cool]

There are lots of tables and forums out there that try and tell you what you will need in the way of batteries and panels to provide power to your home or rig. But basicly, your battery is like a fuel tank and the solar panels are like a filling station. If you need to use a lot of power before you get a chance to charge, you need more batteries. If your battery(s) doesn't fill up on the "average" day of sunlight, you need more panels. It's pretty expensive (in panels and batteries) to cover yourself for the worst case senario, so for that occasional trip of worse then usual weather, run your engine to help fill up the AGM.
I agree, that one panel might be a little shy, but it depends on what the output of your panel is. It's not the number of panels that count, but the watt output of the system. Your only concern on the number of panels (other then a place to put 'em) is the size of your controller. You don't want the output of your panels to be more then your controller can handle. I would think that most folks with an electric fridge would want at least 100 watts of panels. Just my feelings.

stiggs · 12-31-2007, 12:15 AM

Bought one at Autozone 12 bucks or so has a digital read out and Green Yellow and Red for the quick glance, works well in general sorta way.

Johnny