Note: this section is likely not appropriate for newbies; if the ideas are implemented incorrectly it could result in battery murder and disappointment.

Running slimmer-than-normal battery reserves saves space, money, and weight. Here we discuss some ideas about reducing calculated reserves. For purposes of illustration, we will assume the vandweller's daily power requirements are 100Ah, and that they are using lead chemistry batteries.

Loads that can be powered from solar will not come from the battery. If 2/3rd of the laods are serviced this way it leaves only 33Ah that is needed overnight.

Days of reserve calculations usually assume poor solar harvest == zero solar harvest. In reality this is almost always incorrect; some solar power is harvested even under dark overcast or rainy conditions.

In normal full overcast I see yields 20% of usual. In dark full overcast, as when storming, I see yields 5-10% of usual. – secessus

A fractional reserve might be a half- or quarter day of battery reserve. This takes into account the (reduced) contributions from your solar, alternator, etc. It may also require going into voluntary power-rationing mode when solar output is very low.

In areas with abundant and consistent insolation like the desert southwest, you may be able to run with no reserves at all, just enough make it through the night.

making more power

• Overpaneling (having extra panels) is a key technique
• addimg alternator or other forms of additional charging.

using less power

• Time-shifting loads to periods of excess power will help keep the solar fully-utilized and bank fully charged until the sun goes down.
• finding and disabling parasitic loads