Indolent58
New Member
- Joined
- Sep 14, 2020
- Messages
- 34
Since I have learned so much from this forum I thought I would share my approach to upgrading my Sprinter RV's battery bank. When I bought my Winnebago ERA it had two undercarriage mounted 100Ah AGMs and no inverter. Some years ago I added a 300 watt Renogy solar array, a 20 amp MPPT charge controller and a 2000W Kisae-Abso charger/inverter. That worked fine for coffee machine and microwave use while boondocking until the LP refrigerator failed and I replaced it with a 12v Marine refrigerator. With the additional load the system could keep up most of the time but only just, and the AGMs were suffering from deep discharges. Occasionally we didn't have enough power to make coffee in the morning. Lack of coffee is unacceptable so I embarked on this upgrade. I started with the intention of just using drop in 12v replacement LIFEPO4s but learned that the exposed location of the battery holders was just bad news for Lithiums even with temperature protection. That, and the price/kwh of DIY LIFEPO4 banks made me look for ways to build a bank that would live inside the van where temperature extremes can be mitigated. Sprinter RVs have very limited interior space for new stuff and we wanted to minimize lost storage. I built a 16 gauge steel case to fit 8 280ah EVE cells that goes on the side of the rear convertible bed. The cells are managed by two Overkill Solar 4S BMS. The cells are protected from contact with the case by a combination of FR4 and heavy polypropylene sheets. To constrain the cells they are held in place by a steel plate clamped against steel angle brackets and bolts. The system is not as rigid as a threaded rod apparatus would be so the cells can't be as tightly compressed but I expect that it will be sufficient to keep them from moving much if at all. I made cell busbars out of multiple layers of 12 oz copper sheet tinned where they make contact with the cells and fabricated terminal busbars out of tinned copper bar stock, stainless steel bolts and epoxied FR4. The lid of the battery box is FR4 sheet partly for insulation and partly to make sure signals from the BMS bluetooth modules aren't blocked. As part of the project I added a Renogy 60 amp DC-DC charger to manage alternator charging. Haven't had a chance for a real world test yet but I expect that this will more than sufficient for extended boondocking.
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