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House Batteries Boiling – Suspect Battery Charger Wiring

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cbsura

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Jun 7, 2004
27
Bavaria 32 Branford, CT
Last year I purchased a 2005 Bavaria 32 with DC switch panel 201 and distribution panel 205. There are two group 4D house batteries (240 AH total) and a group 47 starting battery (all wet cells). The battery charger is an SBC 250 Advanced Plus from Quick Italy (and the switch is set for wet cells).
The starting battery is fine but the house batteries are overcharging (gassing/boiling). The PO replaced the batteries in 2008. This seems like a premature failure to me and leads me to suspect the original wiring is flawed. The charger has 3 DC outputs (master, slave A & slave B) and one common ground return. Rather than going direct to any batteries, master and ground are wired to the distribution panel 205. Slave A goes to the starting battery, and slave B is not connected. It seems like their intention was to allow the battery charger to run 12V equipment like the fridge when on shore power so as not to drain the house batteries. For those familiar with panel 201, the bottom right yellow LED (“hauptschalter” is “main switch”) illuminates when either the battery switch or battery charger is turned on. The green LED directly above and to the left (above the graphic of a battery) illuminates when the battery charger is on.
The down side of this arrangement is that when the main battery switch is on the charger never drops to float and the house batteries overcharge. When the main battery switch is off the house batteries do not charge at all and the charger displays flashing LED errors. I think I should run a new master line direct to house battery 1. I am also wondering whether I should wire slave B to house battery 2, or perhaps instead connect slave B to the existing wire going to the distribution panel? In other words, is it more advantageous to charge each house battery individually or together as a single bank? Or will the direct connection to the distribution panel do more to preserve battery life when the fridge runs 24/7? Thank you in advance for your suggestions!
 

robgs

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May 24, 2004
26
Bavaria Vision 40 Rock Hall MD
Your house batteries may be failing even though they seem fairly new. In your setup your 2 house 4D's should be treated as a single bank and connected to the master output of the charger. This connection can be made either directly to the +ve post on the battery bank or at the panel if it is connected to the battery bank +ve with heavy gauge cable. Either the slave 1 or 2 outlet can be used to charge the engine battery but be aware that the charger controls its output to all terminals based on the needs of the master connection only. There is a risk that the engine battery can be overcharged if the house bank is in constant use and under constant charge.

The quick charger should control bulk/absorbtion/float staging based on what load it senses from the system. It will not drop to the float stage (around 13.5 V) if there is more than 8 amps load from the battery bank or from other loads through the panel. You can check this by disconnecting batteries from the charger (-ve terminal) and seeing if it goes to float voltage under no load.

I recently had battery boiling probems with 5 yr old batteries, tested the charger, etc. and replaced the batteries. no overheating/boiling at all now.
 

cbsura

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Jun 7, 2004
27
Bavaria 32 Branford, CT
Thanks for the suggestions. I will take your advice and connect the master output to the house bank side of the battery switch. Given that it will probably cook the starting battery now, I guess it's time for me to start searching for a new multibank charger that senses the state of each bank separately, along with a battery temperature sensor and remote monitor. And maybe even a reconditioning cycle... It would cost about the same as a new set of house batteries!
 
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