Lithium battery and B2B - fitting advice

[DavieR]

I am considering swapping out my two old 110Ah lead acid batteries with a 100Ah LiFePO4 battery.

 

I am well read on the general for and against arguments of using Lithium batteries in motorhomes. For our use (all year round off-grid plus winter use in Scotland for a couple of weeks at a time with short daily journeys) I think they will be ideal as Lithium addresses the slow alternator charging of lead acid. Our main power consumption is from our Truma 4e heater, lighting, gadget battery charging, water pump etc. No TV, no fridge or inverter use.

 

I believe our Euro 6 Fiat Ducato 2.3 130 Multijet has a 150amp alternator – definitely non-smart. My plan so far is to fit a Votronic B2B, either the 30amp VCC 1212-30 or the 50amp VCC 1212-50. The choice depends on the capabilities of the alternator.

 

Previously, I upgraded the wiring between the starter and leisure batteries (under front seats) to 16mmsq which is within the B2B specs for 30amp and on the limit for 50amp. Alternator charging bypasses our CBE control box.

 

We also have a 100watt solar panel (which is worth zilch on most winter days) but I do have a Votronic MPPT controller with a LiFePO4 profile.

 

Charging in cold temperatures is a problem with Lithium batteries which is my main worry. However, I'm looking at the Relion RB100-LT battery (LT stands for “Low Temperature”) - https://relionbattery.com/products/lithium/rb100-lt This battery has a Battery Management System (don't they all?) to prevent low temperature charging but it also has heating elements to raise the battery cell temperature to permit safe charging. Basically, an alternator charge of 10amp is directed to the heating elements until a safe temperature is reached.

 

But here is an issue. The Votronic B2Bs must have a battery temperature sensor fitted when using a Lithium profile – this, I guess, would prevent a charge reaching the heating elements in cold temperatures. To get around this I have been advised to use a Gel battery profile. At 14.4v this probably wont get me a full charge but apparently that is a good thing to increase the number of charging cycles.

 

In the depths of winter how stressed is the alternator on a cold start with lights/heater/wipers on and will it cope with a maximum extra draw of 30 or 50amps? I have thought of fitting a switch to isolate the B2B until the engine has warmed up, but I'm not sure of the best way to do that.

 

Is there anything I have not considered, general or technical?

 

Thanks.

 

[spirou]

From Victron, not Votronic, but it should give you some ideas/answers

 

https://www.victronenergy.com/blog/2019/06/18/the-victron-van-install/

[mikefitz]

If the lithium setting is used with the temperature sensor the output voltage is reduced to 12.8 volts for over 50C and less than 0C. Hopefully 12.8v should operate the heater controlled by the bms.

 

Using the gel settings is not ideal due to the long absorbtion time, ( for lithium absorbtion should be of short duration or no absorbtion time at all). Also the charge voltages will be temperature compensated, generally not advised for lithium. Long term float voltages for lithium are recomended to be 13.4 or 13.5 volts.

 

The standard 150 or 180 amp alternator will deliver at least a (spare) 80 amps with a cold engine at tick over revs but for reliability I think 50 amps maximum would be practical. Note the Votronic B to B units are rated on output current so the input current will typically be higher.

 

To control the Votronic operation you could switch 12v to the D+ control input. Once you have selected this mode the voltage sense mode no longer functions, ( unless a master reset), so would need to select or not on each trip.

 

Votronic B to B chargers will operate in parallel so initially you could use the 30 amp unit to gain experience with the system, and have the option of adding a second unit if higher charging currents are needed.

 

Mike

[DavieR]

spirou - 2020-08-14 9:56 PM

 

From Victron, not Votronic, but it should give you some ideas/answers

 

https://www.victronenergy.com/blog/2019/06/18/the-victron-van-install/

 

Thanks spirou. I had seen the Victron video before and its why I'm anxious to know more about my alternator.

 

The Victron schematic is a bit too complicated for me in that the the distribution board is between the starter and leisure batteries. I was looking at the Victron Orion-Tr Smart DC-DC Charger but I'm not sure there is sufficient space for me to fit it allowing for the required spacing.

[DavieR]

Thanks Mike - thats very useful and you have given me much to think about.

 

mikefitz - 2020-08-15 8:41 PM

 

If the lithium setting is used with the temperature sensor the output voltage is reduced to 12.8 volts for over 50C and less than 0C. Hopefully 12.8v should operate the heater controlled by the bms.

I'll ask Relion about that. I do wonder though if I should forget the LT version - it might be simpler and one less variable to consider. The only downside I can see is that we might have to go for a longer drive occasionally.

 

Using the gel settings is not ideal due to the long absorbtion time, ( for lithium absorbtion should be of short duration or no absorbtion time at all). Also the charge voltages will be temperature compensated, generally not advised for lithium. Long term float voltages for lithium are recomended to be 13.4 or 13.5 volts.

Ah, OK. More reading required here. I note that the Votronic 12/12-50 has several LiFePO settings, one of which is for RB Relions.

 

The standard 150 or 180 amp alternator will deliver at least a (spare) 80 amps with a cold engine at tick over revs but for reliability I think 50 amps maximum would be practical. Note the Votronic B to B units are rated on output current so the input current will typically be higher.

This is what I'm looking for! Why is it so hard to find this out? I've scoured the internet looking for it and my dealer wasn't definitive in their answer.

 

To control the Votronic operation you could switch 12v to the D+ control input. Once you have selected this mode the voltage sense mode no longer functions, ( unless a master reset), so would need to select or not on each trip.

MrsR would call that a faff and wouldn't be happy! Its good info though. If the alternator is OK with up to 50amps then I don't think a switch is a concern.

 

Votronic B to B chargers will operate in parallel so initially you could use the 30 amp unit to gain experience with the system, and have the option of adding a second unit if higher charging currents are needed.

Mhmm. I had read that but I'm not so keen. Its another set of wires in an already crowded space and more overall expense - removing the front seats isn't much fun either!. I note that the 1212-50 has an In Limit setting of 68A, 49A, 42A or 33A. With this I can upgrade from 33A at a flick of a switch.

 

I do see Lithium batteries advertised as drop-in replacements. I can overthink things sometimes, but really?

 

[spirou]

DavieR - 2020-08-16 11:04 AM

 

I do see Lithium batteries advertised as drop-in replacements. I can overthink things sometimes, but really?

 

if you consider the size then yes. Everything else... not so much :D

[Travelbob]

" Lithium batteries advertised as drop-in replacements" if you see this advertised, keep well clear of the company/shop, for they don't know what they are talking about, or just con merchants.

[StephDeLux]

Travelbob - 2020-08-18 2:52 AM

 

" Lithium batteries advertised as drop-in replacements" if you see this advertised, keep well clear of the company/shop, for they don't know what they are talking about, or just con merchants.

 

I have a Super-B Epsilon, which is an actual drop-in replacement. It really works. I set the EBL to "Gel" and the B2B to Lithium. The B2B charges it at 57A while driving, eliminating the need for solar.

[Travelbob]

The reason for my reply is you cant just drop a lithium battery in place of lead acid, it is not simple as that.

 

Taking care of the battery will prevent things happerning during use such as Lithium Ion batteries disengaging themselves (by a safety relay).

 

you may have it right, but others may just drop it in, and that will cause problems.

 

Battery monitoring needs to be shunt (Ah counting) based, not voltage based. Some basic battery monitoring products base the battery status fully on voltage measurement. In case of Lithium Ion batteries this will result in unreliable readings, potentially leading to deep discharges. Only shunt-based monitoring devices that incorporate a Lithium Ion battery type setting should be used.

 

i think what is important is an external safety relay (battery disconnect switch) and integrated battery monitoring, Setting this up correctly, including alarms and events through the MasterBus network, results in a safe and intuitive user interface.

 

P.S.

if wild camping, solar is good, saves fuel.

[arthur49]

Travelbob - 2020-08-18 12:06 PM

 

The reason for my reply is you cant just drop a lithium battery in place of lead acid, it is not simple as that.

 

Taking care of the battery will prevent things happerning during use such as Lithium Ion batteries disengaging themselves (by a safety relay).

 

you may have it right, but others may just drop it in, and that will cause problems.

 

Battery monitoring needs to be shunt (Ah counting) based, not voltage based. Some basic battery monitoring products base the battery status fully on voltage measurement. In case of Lithium Ion batteries this will result in unreliable readings, potentially leading to deep discharges. Only shunt-based monitoring devices that incorporate a Lithium Ion battery type setting should be used.

 

i think what is important is an external safety relay (battery disconnect switch) and integrated battery monitoring, Setting this up correctly, including alarms and events through the MasterBus network, results in a safe and intuitive user interface.

 

P.S.

if wild camping, solar is good, saves fuel.

 

Yes.

 

If anyone believes lithium is a straightforward drop in replacement for lead acid I believe problems are on the horizon. This thread for instance includes input from an expert - Nick at VanBotz

 

https://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Lead-v-lithium/53527/

[spirou]

A gel or any other lead charge profile is not the healthiest setting for lithium. Voltage wise possibly, absorption duration unlikely. Nearly all battery manufacturers specify 30min-1h while a gel setting is usually there for several hours. And this is just one of the considerations for a "drop in" to actually be one.