Charging EI backup battery ?

[Alan Carroll]

Originally Posted by DanH

Previously mentioned I was looking at some very inexpensive voltage monitor boards. Ordered two kinds, and I've been playing a bit on the bench tonight. This one seems to be the ticket:

http://www.tomtop.com/modules-219/p-e1021.html

Costs a whopping $4.59. Voltage readout matches my trusty Fluke. Easy to set upper and lower limits in 0.1V increments. Closes an on-the-board relay if voltage reaches either limit, and sets off a buzzer. It will watch voltage on the #2 ignition's battery bus all the time.

Very nice (and the price is certainly right!)

[Alan Carroll]

Originally Posted by DanH

I was poking around on the EarthX website last night. Turns out they recommend using a diode between the main battery and a small backup battery, to drop some voltage on purpose, and thus limit charge current. The graphs don't make much sense to me, but here, read for yourself:

http://earthxbatteries.com/dual-bus-...battery-design

Dan,

I had missed this; thanks for posting. The graphs are indeed a bit cryptic because of the unexplained time axis.

It would be really interesting to see someone do side-by-side testing of equivalent Odyssey and EarthX batteries through their respective charge-discharge cycles (preferably done by a knowledgeable 3rd party).

[Frank from Quebec]

This voltage monitoring light is a very compact way of doing it too.

http://www.ebay.com/itm/12v-LED-Batt...BS2H1r&vxp=mtr

[gmcjetpilot]

This is an interesting thread. I went down the same paths...

• Diode to isolate your E-bus battery
  
• DC to DC charger is interesting, one way to go.
  
• Aux battery protection device like the Chinese made ones ($3 to $6) for under/over volt protection with relay. I bought two different ones, one with volt display and push button setting and one with high precision pots... Both have 10A relay and can be NC or NO. **
  
• Stand alone High-Low volt indicator light is cool mentioned in this thread. Most Eng monitors have warning for low volt. My ND small alternator drives a no output light as well.

** The Boat industry is all over redundant reliable electrical systems, with industrial strength by companies like Blue Sea.... Boats run banks of main and aux batteries. It is critical to protect the Aux batteries from draining. To be mid ocean and not be able to start your engine(s) is bad news. As was said they are well made but heavy in weight.

[rv6ejguy]

The CPI2 has a dedicated backup battery charging circuit built in so you don't need to worry about doing this externally.

[gmcjetpilot]

Originally Posted by rv6ejguy

The CPI2 has a dedicated backup battery charging circuit built in so you don't need to worry about doing this externally.

Thanks Ross. I just got up to speed on your CPI2... I am standing by to see that progress. My plan was two CPI's and do the OV protection myself, but depending on price I think I'll switch to the CPI2.

BTW What is the Max/Min operating voltage for the CPI or CPI2.

[rv6ejguy]

The CPU will operate down to about 7.5V and we've tested to 18V. There are upper and lower voltage thresholds set in the CPI2 software for different battery chemistries.

[Larry DeCamp]

The Chinese boards Dan found sound great. I have a simple switch to isolate the second ignition buss from diode supply And a blue sea volt meter on the panel. First step on startup is check voltage on the little battery with master OFF. Not elegant, but simple and effective.

[lr172]

Originally Posted by gmcjetpilot

This is an interesting thread. I went down the same paths...

• Diode to isolate your E-bus battery
  
• DC to DC charger is interesting, one way to go.
  
• Aux battery protection device like the Chinese made ones ($3 to $6) for under/over volt protection with relay. I bought two different ones, one with volt display and push button setting and one with high precision pots... Both have 10A relay and can be NC or NO. **
  
• Stand alone High-Low volt indicator light is cool mentioned in this thread. Most Eng monitors have warning for low volt. My ND small alternator drives a no output light as well.

** The Boat industry is all over redundant reliable electrical systems, with industrial strength by companies like Blue Sea.... Boats run banks of main and aux batteries. It is critical to protect the Aux batteries from draining. To be mid ocean and not be able to start your engine(s) is bad news. As was said they are well made but heavy in weight.

I am setting up a 2 batt system (PC680's) in the 10, with the second batt running a b/u bus. I am putting a 20A diode from the main bus to the b/u batt, but also have a second contactor to put batt 2 on the main bus. The plan is that any significant discharged state on batt #2 will require me to remember to have the #2 contactor closed before the alternator starts charging or my diode will blow. The second contactor also lets me use both batt's for starting, if necessary.

Larry

[Walt]

Originally Posted by lr172

I am setting up a 2 batt system (PC680's) in the 10, with the second batt running a b/u bus. I am putting a 20A diode from the main bus to the b/u batt, but also have a second contactor to put batt 2 on the main bus. The plan is that any significant discharged state on batt #2 will require me to remember to have the #2 contactor closed before the alternator starts charging or my diode will blow. The second contactor also lets me use both batt's for starting, if necessary.

Larry

Sounds like you need to rethink that "plan", or have plenty of spare diodes on hand