House Batteries Only Charging To 12.7 v

[Doug Patton]

I have a 07 Signature with 4 AGM house batteries, 2 lead acid chassis batteries and a new 2800 pure sine wave Magnum inverter. I am not charging the chassis batteries from shore or gen. My house batteries never charge above 12.7 or 12.8 thus the Big Boy never gets enough voltage to join the two battery banks to charge the chassis batteries. Would be interested in trouble shooting ideas. All connections seem to be tight and good. All four Lifeline AGM batteries are about 6 months old and the two chassis batteries are about 4 months old. House batteries maintain the 12.7 / 12.8 charge but never charge above that voltage. The batteries have been equalized this past week. Where do I go next?

[jlturner]

Mine was doing the same thing. I called Magnum. They suggested I change the BTS. (Battery Temp. Sensor).

After replacement batteries stay at 13.8/13.9


Sent from my iPhone using iRV2 - RV Forum

[YC1]

You can unplug the battery sensor cable and run without it for a test.

[Mike Canter]

12.6-12.7 is a 100% charge on a 12 volt battery. Just so there is no confusion here if your BIRD charging system took the chassis batteries up to 13.2 volts and then disconnected the charger from them then the chassis batteries would read 12.7 volts. The fact that they read 12.7 volts means that all is working correctly, if not they they would read a lower voltage. The best way to see what the chassis and house batteries are truly charged to is to disconnect shore power and no generator then let everything sit for about thirty minutes then read the battery voltage. You may want to do this at night so the solar panels are not raising the battery voltage.

[dpinvidic]

Another attempt to clear any confusion.
A battery that is fully charged and sitting on a table will read 12.7v if it has been sitting and has no loads on it.

Now if you attach a battery charger to it, you you should read about 13.8V because the charger is applying a "Float Charge". This float charge is enough to keep the batter fully charged, but not cause any electrolyte to boil off.

The Big Boy solenoid should NOT get energized unless the inverter is supplying the 13.8V float voltage. You don't want to connect the chassis and house batteries together unless the controller sees that there is a voltage high enough to indicate it is charging.

So if you are expecting to have your chassis batteries recieve a charge, you need to see the 13.8V on the house batteries....

Regards,

Dan

[Mike Canter]

The BIRD and the BIG BOY switch from charging the house batteries to additionally charging the chassis batteries when the house batteries reach 13.2 volts on these motor homes. When the combined batteries reach 13.2 volts again the Big Boy switches off charging the chassis batteries

[twinboat]

Are we missing the point that the House batteries never go above 12.7 volts, with the charger on.

This has nothing to do with BIRD, IRD, BIG BOY or any other combiner.

Unplug the temp. sensor and check the voltage.

[Mike Canter]

No the point is that when the voltage was measured at 12.7 volts the status of the Big Boy was unknown. If it is 12.7 volts with the Big Boy open then all is normal. If the batteries always read 12.7 then most likely all is ok and that is why I asked him to measure the voltage with everything disconnected so one gets the true battery voltage and not the charger voltage.

[Golden Gopher]

How long can you run unplugged?

What is the downside?

[Scottybdivin]

Originally Posted by Doug Patton

I have a 07 Signature with 4 AGM house batteries, 2 lead acid chassis batteries and a new 2800 pure sine wave Magnum inverter. I am not charging the chassis batteries from shore or gen. My house batteries never charge above 12.7 or 12.8 thus the Big Boy never gets enough voltage to join the two battery banks to charge the chassis batteries. Would be interested in trouble shooting ideas. All connections seem to be tight and good. All four Lifeline AGM batteries are about 6 months old and the two chassis batteries are about 4 months old. House batteries maintain the 12.7 / 12.8 charge but never charge above that voltage. The batteries have been equalized this past week. Where do I go next?

Doug, I just went through exactly the same thing. My chassis batteries were not getting charged because the voltage was too low for the BIRD to activate the solenoid. Both Magnum and a few folks here confirmed this. You can simply unplug the BTS from the inverter and it will begin charging correctly. That will give you time to sort out the BTS issue.

[twinboat]

Originally Posted by Golden Gopher

How long can you run unplugged?

What is the downside?

The downside is cronicly undercharged batteries.

Lifeline states,

For a battery at room temperature, it can be considered fully charged with the charging current falls below 0.5A per 100Ah of rated capacity. The open circuit voltage (after at least 4 hours of rest) will be 2.17 volts per cell or higher (13.0 volts for a 12-volt battery), regardless of the battery temperature.

12.7 volts is not 100% charged and a killer of AGM batteries.

You will never get to 13 volts pushing 12.7 into them.

[dpinvidic]

So it sounds like his inverter is programmed wrong, or broken.

I did not think the temp sensor came into play during float charge.....need to read up onthis.

Dan

[Scottybdivin]

Originally Posted by dpinvidic

So it sounds like his inverter is programmed wrong, or broken.

I did not think the temp sensor came into play during float charge.....need to read up onthis.

Dan

As described by a Magnum technician. If the BTS is busted (like mine), it will sense an open circuit and the charger thinks it is boiling the batteries. It then reduces the charge to 12.7V. As soon as I unplugged the BTS, the charger immediated went to ABSORB at 14.4V, then later reduced to FLOAT at 13.3V.

[Doug Patton]

BTS is new. I tried unplugging it and still do not get the required 13.2 v to the Big Boy on either side.
Thanks
Doug