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Originally Posted by zippy
I thought the rule of thumb was to not go below twelve volts, and below 11.7 the battery is damaged so that it will never recharge to the rated voltage (14.7 ish). That's why batteries boil - the battery can't take 14.7 anymore but the charger/alternator keeps running at that voltage. The energy is converted to heat.
There are replacement alternators that will do 130 amp at idle. With a heavy enough cable and a separator (relay and solinoid) instead of an isolator batteries can be recharged rapidly.
I'm surprised at the money put into generators and solar while the big power producer, the engine, is untouched. Earthroamer's generator-less system has much more to do with the engine power system than the solar system. A couple of horizontal panels don't provide much power. What solar is very good at is "topping up" agm batteries at a gentle current.
It's can be very expensive to build an undersized inexpensive battery system.
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That’s a fairly good rule of thumb but it’s not set in stone mainly because of the different types of batteries out there. What kills an AGM quickly (which most people use as house batteries) is if the battery sits at any resting voltage below 100% for lengthy periods of time. When you run a microwave for a short period of time (like making popcorn
), the voltage drops into the 10volt range because the oven is pulling around 80 amps. The house system voltage will float back up to the batteries resting voltage, usually somewhere in the 12 zone provided the batteries have a large enough amp hour rating and are relatively full. With standard cycling, a lot depends on the type and manufacture quality of the battery. I still try to avoid dropping the voltage down below the mid 11 resting volt range but that’s quite a bit of usage for my system to reach that. I was really upset when the Ford garage let my two brand new 4-D Lifeline AGM batteries drop to a resting voltage of 9.6 volts. That’s considered dead. I called a Lifeline tech and was told that as long as they weren’t sitting at that voltage for over a couple of weeks, virtually nothing would be damaged. I probably lost a few percent of storage, but the batteries are fine. That’s where quality paid off. The same thing has happened to me with Optima batteries and they were wasted. I will never bank together different types/makes of batteries, different aged batteries or connect a new battery to one that can store a lower % of charge unless they are being charged by some type of smart charging system. With the charger off I would want a want to separate them in some way.
Any smart charger is a good investment. If you can add smart charge technology to an alternator, that would be a plus IMO. I installed a 200 amp alternator and it made a huge difference. My batteries are brought back up quickly while driving no matter what’s on in the vehicle. The solar is nice when in camp and I’m running light load devices like a fan that the solar can handle and still supply a positive charge. When my van sits on the driveway and the refrigerator is running, I am always plugged into shore power so it runs off AC but I leave the battery charging up to the solar and keep the inverter/charger off. I drive the van often so the starting batteries are kept up but I wish I had a small panel to keep the starting batteries topped off as well. In all honesty, I probably have too much solar myself considering that I very rarely sit in camp. The alternator is the main charging system on my van, but when I do relax, it's nice to know that I'll be topped off by 10AM even if I'm not in full sun. I now have twin 130W panels on top and a 65 watt portable.
Sportsmobile (AKA Money Pit)
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