Originally Posted by eric1514
I have a Travato with 2 group 31 AGM deep cycle batteries mounted underneath like most all Travatos. It came with 1 but I added another. Since I'm stuck at home, except on the weekends where I work at an "essential" retailer, I've been thinking about adding 2 more batteries, same size, same specs to have a project to alleviate the boredom. I know that the 2 new batteries will be "newer" than the other 2 (but I'm not going to worry about that now) and I know about how to wire them together so as to equalize their charging and discharging. What I'm curious about is whether my stock charging equipment will handle the new load.
I have the factory installed PD9245 converter with an owner installed pendant and I have 300 watts of solar on the roof with a MPPT controller. I also have a Trimetric monitor to watch.
It seems to me, all the cables/wires are installed except for the ones interconnecting the batteries. I would leave the positive cable outside but bring all the negative ones inside to hook up to my shunt and the last battery in the chain.
Am I overlooking anything?
Your charger is on the small side at about 10%in amps of battery capacity in amp hours, so it could stretch out your charge times. Some manufacturers like Lifeline are recommending higher charge rates on over 50% discharge cycles, but not others aren't. With a PD charger you are likely limited to a 4 hour total charge time to float, so you probably would need to force it back into boost with the pendant. You have a battery monitor, which is good, as that is how you would determine the need to force the PD stage in and out of absorption to get the batteries full. Be sure all the settings in the monitor get changed for the bank size, especially the bank size and the transition to float amperage.
The more batteries you have in a bank, the more important cable matching gets, IMO. With a 4X parallel bank of 12v batteries you probably would want to consider taking both the positive and negative to common tie points with equal length, or as close as you can get, cables on each from the batteries to the tie point. The positive and negative individual lengths don't need to match, only the total of positive and negative lengths on each battery between the tie points, so a short positive and long negative would be OK if all had the total length. On the negative side, your shunt will take care of it for a tie point.
400+ amp hours of AGM batteries can generate quite hazardous amounts of amps, so you need to be sure every cable and wire, with the possible exception of the battery to tie point cables if they are short and in a safe place, are appropriately fused for their size. This would also apply to any wiring from the alternator to the batteries, and on both ends of that wiring as those batteries will be able to accept way more than you alternator will put out. Some sort of limiting on the alternator charging may be a good idea to save the alternator from excessive, long term, load.
As with all this kind of stuff, be sure you have the load capacity for another close to 150# without overloading or losing ability to carry what you need.