Question from someone very new to GMCs. My PO installed two batteries in series for the house. They are 6V. What is the advantage of this configuration compared to a single 12V battery?
House Batteries
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Two 6v batteries in series behave like one big 12v battery. On the other hand, if you have two 12v batteries and one of them goes bad, it will make the charger overcharge the other one, potentially causing a catastrophic failure.
Thanks @Christo! Sorry if this question seems very simple, but why not just use one 12V battery? Are the 2 batteries for redundancy, so that if one fails you can continue using the other?
The two 6 volt batteris in series give 12volts total but more capacity than only one 12v battery. ....so if the 6v is 250cca putting 2 in series give you 500cca for 12v (generalisation of course)
No worries. You could certainly run a single 12v battery depending on how much house capacity you need. If you'll always be hooked up to power at campgrounds it might be sufficient. But if you need greater capacity for boondocking, two 6v batteries is the best way to get there.
The extra capacity is more about run time than amperage delivered, though I'm sure there is also a correlation to current supply.
In general, the more lead you have, the more capacity you have. 6v batteries have three cells, each producing a bit over 2v a piece. A 12v battery will have roughly the same physical footprint as a 6v. However, there needs to be 6 cells in the 12v battery, thus reducing the amount of lead per cell. It's further reduced by the need for spacers between the cells to isolate them from one another.
That means your 6v battery will have roughly double the amp-hour capacity of the 12v. So... Two 6V batteries, wired in series, will give you double the capacity of a single 12v. I'd have to do some more digging, but I think it's actually more than double, which is why it's preferable to use to 2 6v batteries in series instead of two 12v batteries in parallel. I'll post more info tomorrow. I have some reference material at work.
When you series 6 volt batteries the amperage remains the same, although you increase your ultimate power. A typical 6 volt battery we use are sourced from the the golf cart industry. Normal amperage is typically about 220 AH (amp hours) at 6 volts and this will still be 220 AH's at 12 volts but these batteries are designed for deep slow discharges where a nominal 12 volt battery will have smaller plates to accomplish fast discharge rates better suited for starting assignments. Even the so called deep cycle 12 volt batteries are a compromise and really won't perform like a true deep cycle 2 or 6 volt battery.
Battery science isn't really the black magic it once was but it takes a bit of research to dig through all the fog out there.
Battery science isn't really the black magic it once was but it takes a bit of research to dig through all the fog out there.
Thanks for the explanation, guys! There's quite the learning curve to climb, so I really appreciate your help and taking the time to explain these concepts.
Next question - battery maintenance. The dates on the two house batteries are from 2016 and they seem to hold charge pretty well. There's no leakage, corrosion on the connectors, or anything like that either. When should I consider replacing the batteries? Should it be done on a schedule (every five years, etc...)? Also, do you need to add water to them or anything like that? I haven't pulled out the tray to see if there are even ports for water, but figured I would ask. The coach is in storage, so unfortunately I don't know the battery models. They're golf cart batteries from Costco and I think they're the ones other folks have mentioned on threads in the other GMC forum.
Next question - battery maintenance. The dates on the two house batteries are from 2016 and they seem to hold charge pretty well. There's no leakage, corrosion on the connectors, or anything like that either. When should I consider replacing the batteries? Should it be done on a schedule (every five years, etc...)? Also, do you need to add water to them or anything like that? I haven't pulled out the tray to see if there are even ports for water, but figured I would ask. The coach is in storage, so unfortunately I don't know the battery models. They're golf cart batteries from Costco and I think they're the ones other folks have mentioned on threads in the other GMC forum.
Jamie,
Answering questions is why some of us are here. If we don't feel like answering questions, we won't show up. Remember too, any question you have may also be a question that another has, but has not yet figured out how to make enough sense of it to ask.
Now, about water in batteries.
Check them regularly and fill to the split ring with - In this order:
True distilled water
Drain water from a dehumidifier
Grocery store deionized water
Notice tap water is not on the list. Use it only as a last resort.
If your converter is still the OE (Triad - Gray) Buzzbox, do not leave the coach connected to shore power. It will damage the bank
I have forgotten who the supplier was to Costco, but they should be good for 6 to 10 seasons with care. Do not bother replacing them until you are sure the capacity has gotten to be less.
Matt
Answering questions is why some of us are here. If we don't feel like answering questions, we won't show up. Remember too, any question you have may also be a question that another has, but has not yet figured out how to make enough sense of it to ask.
Now, about water in batteries.
Check them regularly and fill to the split ring with - In this order:
True distilled water
Drain water from a dehumidifier
Grocery store deionized water
Notice tap water is not on the list. Use it only as a last resort.
If your converter is still the OE (Triad - Gray) Buzzbox, do not leave the coach connected to shore power. It will damage the bank
I have forgotten who the supplier was to Costco, but they should be good for 6 to 10 seasons with care. Do not bother replacing them until you are sure the capacity has gotten to be less.
Matt
