Dual batts again

[stevemc181]

I was concerned about it due the statement on Page 6 of the BB1260 manual. It specifically mentions the negs must be common on the diagram. I'm not sure why, hence querying if this would affect the Shunt I have in place for the Aux battery monitoring.

https://cdn.shopify.com/s/files/1/0658/7343/files/BB1260_Instructions_NEW_f8c2e4e6-c3aa-47aa-83ef-d35a128bb4df.pdf?17185752620085016530

[pajeromack]

For the numbers of times I'd ever need to do this, it's not worth it. I carry large jumper leads with me anyway, so i can just connect up to the rear battery when required.

Fair enough. I'm keen on a push-button option as I'll have it mounted behind some panelling. I haven't done any wiring yet at all yet so I'll probably use a somewhat lower gauge/thicker cable. Won't go overboard as I only intend it to 'boost' the main battery if required or provide extra charge for a winch.

Also noticed that GSL do a DCDC lithium charger NGBC1222 - $262
Even has a bypass option for emergency starting!

http://www.gsl.com.au/battery-chargers-12v-12v.html

[stevemc181]

Fair enough. I'm keen on a push-button option as I'll have it mounted behind some panelling. I haven't done any wiring yet at all yet so I'll probably use a somewhat lower gauge/thicker cable. Won't go overboard as I only intend it to 'boost' the main battery if required or provide extra charge for a winch.

Also noticed that GSL do a DCDC lithium charger NGBC1222 - $262
Even has a bypass option for emergency starting!
http://www.gsl.com.au/battery-chargers-12v-12v.html

The GSL model you would need for LifePo4 is the MCB-1225L, last time I looked at these they were around $450.00. Still only 25 amp though.

[pajeromack]

The GSL model you would need for LifePo4 is the MCB-1225L, last time I looked at these they were around $450.00. Still only 25 amp though.

The NGBC1222 does claim to provide

optimal charge to a variety of lead acid and lithium battery chemistries

http://www.gsl.com.au/tl_files/pdf-automotive-products/NGBC1222.pdf

It doesn't strictly state LiFePO4.

22-25a isn't such a bad restriction, much more than that and you'd be risking your alternator.

[stevemc181]

The NGBC1222 does claim to provide

http://www.gsl.com.au/tl_files/pdf-automotive-products/NGBC1222.pdf

It doesn't strictly state LiFePO4.

22-25a isn't such a bad restriction, much more than that and you'd be risking your alternator.

I'd query them regarding using it with your LifePo4.
There is no risk to your alternator running a higher output DC charger, I was under this impression initially which is why I only went with a Redarc 1225-LV charger (No LifePo4 specific DC-DC chargers when I bought mine) I've since been re-educated
If I change my charger, it will probably be for the Sterling 60amp BB1260 as mentioned by Drivesafe above, or for the Redarc 40 amp LifePo4 charger. On a depleted battery it can take an awfully long drive to fully charge with a 25 amp charger. On my usual short runs to work, the charger can't keep up with the drain from the rear fridge which is permanently on.

It would also pay to check with your battery supplier if your BMS and Battery is suitable for whatever charger you buy.

[pajeromack]

There is no risk to your alternator running a higher output DC charger, I was under this impression initially which is why I only went with a Redarc 1225-LV charger (No LifePo4 specific DC-DC chargers when I bought mine) I've since been re-educated
If I change my charger, it will probably be for the Sterling 60amp BB1260 as mentioned by Drivesafe above, or for the Redarc 40 amp LifePo4 charger. On a depleted battery it can take an awfully long drive to fully charge with a 25 amp charger. On my usual short runs to work, the charger can't keep up with the drain from the rear fridge which is permanently on.

Are you sure on that? 60a is a LOT of power, about half to two thirds the capacity of most alternators. Once you add in the normal running gear, lights, accessories you'll be at or above the max output. Most alternators actually only have a ~60% duty cycle. If you run them flat-chat for too long (i.e. charging a fully discharged lipo etc) apparently you can burn out the windings.

[stevemc181]

Are you sure on that? 60a is a LOT of power, about half to two thirds the capacity of most alternators. Once you add in the normal running gear, lights, accessories you'll be at or above the max output. Most alternators actually only have a ~60% duty cycle. If you run them flat-chat for too long (i.e. charging a fully discharged lipo etc) apparently you can burn out the windings.

I used to think the same thing, but Drivesafe debunked that myth for me.

http://www2.pajeroclub.com.au/forum/showpost.php?p=419167&postcount=71

Drivesafe earns a living from dual battery control systems and associated electronic gear, and has a lot more knowledge than most of us on what is suitable for charging etc. A lot of my earlier thinking has proven incorrect over time, particularly regarding DC charging and alternator output etc. The pros and cons have been done to death in other threads, so I'll leave that side of it alone.

[Bru9]

Some sources say Lifep04 can handle heat up to 60 degrees C without any issues with longevity. Would one under the bonnet be a bad idea given the cost of such batteries?

What are the max safe discharge rates compared to lead? I'm confused by this C rate? it seems way to high compared to lead which is usually capacity/20.

[stevemc181]

Some sources say Lifep04 can handle heat up to 60 degrees C without any issues with longevity. Would one under the bonnet be a bad idea given the cost of such batteries?

What are the max safe discharge rates compared to lead? I'm confused by this C rate? it seems way to high compared to lead which is usually capacity/20.

I would think under bonnet temps would get far higher than 60°C at times, There are a few exceptions but generally heat and batteries don't mix well together and for longevity reasons it is best to mount the LifePo4 elsewhere. My LifePo4 battery is only recommended at a max 50°C working temp.


The LifePo4 generally have much higher discharge rates and depth of discharge capacitys than any lead battery. Various battery management systems that the different manufacturers use may also limit the discharge rate. Mine is no problem at a 240amp continuos discharge rate, which far exceeds anything I'll need to draw from it. Short bursts of 800 Amps are no problem. This is one of the reasons I chose this particular battery, as I have no problem using it for a jump start if required. This is not the same for all Lifepo4’s and their various BMS will have different recommended discharge rates.

A few of the benefits of going LifePo4.
High charge and discharge rate
Low weight
Fast recharge to 100%, no absorption stage or float stage required.
Low self discharge when left sitting doing nothing
Lifespan is much longer than lead at a deeper depth of discharge, 80-85% DOD is not a problem
Much higher useable battery capacity (Stays above 13volts until around 90% DOD) It is best to measure amps in and out so you know the state of charge of the battery, volts alone isn't a good indicator with these batteries.
Everything in this battery is recyclable

Some disadvantages:
Higher initial cost
One overcharge or over discharge can kill it, this is why a BMS (Battery Management System) is important when using LifePo4, I also have an additional LV/HV shutoff in case the BMS fails to do its job. The BMS will also balance the cells by bleeding voltage from one cell to another if it detects an issue or shut off the battery if a cell goes out of range, this is rare but can happen and needs to be protected against.

[Bru9]

I would think under bonnet temps would get far higher than 60°C at times, There are a few exceptions but generally heat and batteries don't mix well together and for longevity reasons it is best to mount the LifePo4 elsewhere. My LifePo4 battery is only recommended at a max 50°C working temp.


The LifePo4 generally have much higher discharge rates and depth of discharge capacitys than any lead battery. Various battery management systems that the different manufacturers use may also limit the discharge rate. Mine is no problem at a 240amp continuos discharge rate, which far exceeds anything I'll need to draw from it. Short bursts of 800 Amps are no problem. This is one of the reasons I chose this particular battery, as I have no problem using it for a jump start if required. This is not the same for all Lifepo4’s and their various BMS will have different recommended discharge rates.

A few of the benefits of going LifePo4.
High charge and discharge rate
Low weight
Fast recharge to 100%, no absorption stage or float stage required.
Low self discharge when left sitting doing nothing
Lifespan is much longer than lead at a deeper depth of discharge, 80-85% DOD is not a problem
Much higher useable battery capacity (Stays above 13volts until around 90% DOD) It is best to measure amps in and out so you know the state of charge of the battery, volts alone isn't a good indicator with these batteries.
Everything in this battery is recyclable

Some disadvantages:
Higher initial cost
One overcharge or over discharge can kill it, this is why a BMS (Battery Management System) is important when using LifePo4, I also have an additional LV/HV shutoff in case the BMS fails to do its job. The BMS will also balance the cells by bleeding voltage from one cell to another if it detects an issue or shut off the battery if a cell goes out of range, this is rare but can happen and needs to be protected against.

Thanks for your reply. They are amazing i will get one setup eventually in back somewhere.. Discharge rate is truly amazing, lead is stone age.

[insect_eater]

I've had a look at the Sterling Model BB1260, is this the one you referred to? Looks like a good bit of gear, thanks for the heads up on this unit, I'll add it to my shortlist for sure.

steve/drivesafe - I've also been looking at the Sterling BB1260 and wonder whether it works with smart/variable alternators? It turns on only above 13.6V, whereas the new redarc and GSL/Ironman switch on at 12V so that they work even when the smart alternator is running at lower volts. The BB1260 does have an override mode (3) that turns it on at 11.5V, but warns of flat main batteries.....

It'll obviously kick in after start up - is that what you'd rely on, or am I misunderstanding something?

[drivesafe]

Hi insect_eater, give Ian at RV Powerstream a call on 02 6554 4444.

Ian is the importer of Sterling gear and can give you all the advice you need.

He not only imports the gear, he specialises in designing power supply systems for caravans and camper trailers, motor homes and luxury yachts, and specialised remote area power supplies.

[insect_eater]

Thanks drivesafe, will do.