B2B or not B2B - the more I read the less clear it is

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Okay, I hopefully have an eco tree lithium battery on the way. The 100ah one.

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Current setup is 350w solar with a Votronic MPPT controller and a Victron smart shunt. The rest is standard Hymer build on a 2013 Fiat Chassis.

I currently have 2 100ah Lead Acid batteries installed.

I am happy with the solar that has a lithium setting, I am also happy that the EBL will suffice on a gel setting when I am on mains.

I am also happy that I will probably have enough usable capacity with just the one lithium giving me about 80ah of usable power instead of 100ah with my current setup.

My confusion is about the B2B.

The Hymer puts out a nice 25amps from the alternator charging via the EBL. This plus the solar has served me very well.

Having read all about B2B and lithium, I still remain confused about if I need one or not and which one to go for.

Will the lithium charge properly? Will it be damaged? Will it be £150 wasted on a B2B?

Almost every forum and FAQ say something different so?

What do you think?
 
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If your van has a smart alternator, a B2B charger is likely to be essential. The price is the only downside to a modern B2B, Taking that raw output and delivering an intelligent 4 stage charge to your batteries. Well worth paying for.
 
Can't think I've read anywhere that it doesn't recommend fitting a battery to battery if you install lithium..not to protect the battery but to protect the alternator..
Andy
 
Jim said:
If your van has a smart alternator, a B2B charger is likely to be essential. The price is the only downside to a modern B2B, Taking that raw output and delivering an intelligent 4 stage charge to your batteries. Well worth paying for.
Click to expand...

Thanks Jim, it is an old dumb one and just chucks out a stable 14 volts.

I have no issue spending the money. I have read they are not needed though but others say they are.
 
andy63 said:
Can't think I've read anywhere that it doesn't recommend fitting a battery to battery if you install lithium..not to protect the battery but to protect the alternator..
Andy
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Is that because the resistance doesn’t drop as with lead acid when it is charging?

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Googlebot said:
Is that because the resistance doesn’t drop as with lead acid when it is charging?
Click to expand...
Lithium resistive load would be less than lead acid hence a much higher current capacity on charging..
As far as I know..regardless of smart or dumb one of the main reasons is the lithium can impose an excessive load and at lower revs there isn't sufficient cooling air flow on the alternator..it will overheat.. the charger will limit the current flow to the max of the particular charger..
Jim has already pointed out that you will get a proper staged charge via a battery to battery and not just a constant alternator voltage applied to them..
I'm sure Google will give loads of advice ..I just don't think I've ever read any advice that doesn't recommend a battery to battery if you install lithium..
Certainly there is a train of thought that would suggest that just beefing up the split charge wiring on a normal set up will most probably be as good as installing a battery to battery when you are dealing with lead acid ..
Andy..
 
andy63 said:
Certainly there is a train of thought that would suggest that just beefing up the split charge wiring on a normal set up will most probably be as good as installing a battery to battery when you are dealing with lead acid ..
Andy.
Click to expand...

I wonder if this is where I am getting confused. I haven’t seen anywhere that says you shouldn’t use a B2B with lithium but plenty that do.
 
Googlebot said:
I am also happy that the EBL will suffice on a gel setting when I am on mains.
Click to expand...
I agree. It may undercharge slightly which does no harm to a lithium (unlike lead acid) but you don’t need a full battery when on mains.
Googlebot said:
I am also happy that I will probably have enough usable capacity with just the one lithium giving me about 80ah of usable power instead of 100ah with my current setup.
Click to expand...
I have gone from 2x100Ah lead acid to 1x100Ah lithium without any problems.
Googlebot said:
My confusion is about the B2B.
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If you are going to be off grid a B2B may help. A 14V alternator should achieve a charge of over 90% but if you want a full charge for when you arrive then a B2B will help. You probably have a 50A fuse and wiring from engine battery to EBL so if you get a B2B of less than 50A you should be ok to use the existing connections.
 
Pausim said:
I agree. It may undercharge slightly which does no harm to a lithium (unlike lead acid) but you don’t need a full battery when on mains.

I have gone from 2x100Ah lead acid to 1x100Ah lithium without any problems.

If you are going to be off grid a B2B may help. A 14V alternator should achieve a charge of over 90% but if you want a full charge for when you arrive then a B2B will help. You probably have a 50A fuse and wiring from engine battery to EBL so if you get a B2B of less than 50A you should be ok to use the existing connections.
Click to expand...
That’s great news! I was hoping for a simple installation. Will post a thread when I do get it sorted.
 
It seems fairly unanimous then that I need a B2B.

I was looking at the Votronic models. I would prefer a 60amp one from Sterling but the specs on the battery say maximum charge of 50 and with the solar on a sunny day, I would probably be nearer 80 amps with a 60 amp B2B.

The Votronic comes with instructions to use existing wiring with the EBL.

Has anyone fitted one and have any tips or hints?
 
Googlebot said:
It seems fairly unanimous then that I need a B2B.

I was looking at the Votronic models. I would prefer a 60amp one from Sterling but the specs on the battery say maximum charge of 50 and with the solar on a sunny day, I would probably be nearer 80 amps with a 60 amp B2B.

The Votronic comes with instructions to use existing wiring with the EBL.

Has anyone fitted one and have any tips or hints?
Click to expand...
I have a Votronic VCC1212-45 and I am very pleased with it. I bought it because it had settings and instructions for connection to an EBL. I have since moved it to my Carthago where it works very well but not having an EBL it was a bit more complicated.

With the EBL in my Hymer I disconnected the engine battery positive connection at the rear and used this as the positive feed to the B2B. I then fed the B2B output into the EBL where I had removed the engine battery connection. Negative and D+ were fairly easy to sort out too.

I set the input limit on the B2B to 49A to make sure the fuse and wiring were not overloaded. I thought this worth doing because an output of 45A at 14.6V might draw more than 50A from the source battery.
 
If you're still in the process of choosing a B2B for Lithium, get one with a temperature sensor function. Lithium batteries don't like being charged at or below 0 degrees C. Many B2Bs, even some with a temperature sensor, will still charge a lithium battery below zero.

The inbuilt battery BMS ought to stop charging below zero, but that's a last-ditch kind of measure in case the charger doesn't know what it is doing.
 
autorouter said:
If you're still in the process of choosing a B2B for Lithium, get one with a temperature sensor function. Lithium batteries don't like being charged at or below 0 degrees C. Many B2Bs, even some with a temperature sensor, will still charge a lithium battery below zero.

The inbuilt battery BMS ought to stop charging below zero, but that's a last-ditch kind of measure in case the charger doesn't know what it is doing.
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I have put a switch on the D+ feed so I can disable it if the battery is too cold. Not had to use it yet but I might if picking the motorhome up from storage in freezing weather. Battery is in a heated compartment so not likely to be a problem for long.
 
Pausim said:
I have put a switch on the D+ feed so I can disable it if the battery is too cold. Not had to use it yet but I might if picking the motorhome up from storage in freezing weather. Battery is in a heated compartment so not likely to be a problem for long.
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I'd double check that switching the D+ does in fact shut off the B2B. Some of them (Sterling for example in 'Mode 2') use the D+ to keep the B2B on when the alternator voltage drops. But if the alternator voltage is high, the B2B still works in voltage-sensitive mode, so it can still be charging the battery, even if the D+ is off

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autorouter said:
I'd double check that switching the D+ does in fact shut off the B2B. Some of them (Sterling for example in 'Mode 2') use the D+ to keep the B2B on when the alternator voltage drops. But if the alternator voltage is high, the B2B still works in voltage-sensitive mode, so it can still be charging the battery, even if the D+ is off
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Thanks, I will check this out.
 
Pausim said:
I have a Votronic VCC1212-45 and I am very pleased with it. I bought it because it had settings and instructions for connection to an EBL. I have since moved it to my Carthago where it works very well but not having an EBL it was a bit more complicated.

With the EBL in my Hymer I disconnected the engine battery positive connection at the rear and used this as the positive feed to the B2B. I then fed the B2B output into the EBL where I had removed the engine battery connection. Negative and D+ were fairly easy to sort out too.

I set the input limit on the B2B to 49A to make sure the fuse and wiring were not overloaded. I thought this worth doing because an output of 45A at 14.6V might draw more than 50A from the source battery.
Click to expand...

Can I ask where you got the negative and d+ from?

I am thinking of going for the 30 amp model as it’s £120 cheaper and I don’t think I will need the full 50 amps.

Thanks for the tips, the battery is in a heated part of the motorhome so I am not too worried about it being cold.

That said, what about the solar? Will that damage it being on charge below freezing?
 
Googlebot said:
Can I ask where you got the negative and d+ from?

I am thinking of going for the 30 amp model as it’s £120 cheaper and I don’t think I will need the full 50 amps.

Thanks for the tips, the battery is in a heated part of the motorhome so I am not too worried about it being cold.

That said, what about the solar? Will that damage it being on charge below freezing?
Click to expand...
For the negative I drilled through the floor into the battery compartment and connected it to the shunt of my battery monitor, if no shunt then direct to the battery would do. I can’t remember exactly where I picked up the D+ but I probably joined it to one of the wires from the EBL.
 
Pausim said:
For the negative I drilled through the floor into the battery compartment and connected it to the shunt of my battery monitor, if no shunt then direct to the battery would do. I can’t remember exactly where I picked up the D+ but I probably joined it to one of the wires from the EBL.
Click to expand...

Great stuff, will have look then. I was hoping to use the negative at the EBL as the run to the battery compartment is a pain!
 
Googlebot said:
Great stuff, will have look then. I was hoping to use the negative at the EBL as the run to the battery compartment is a pain!
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A chunky junction box on the negative should do. I found I needed one on the positive because of wire length to the B2B.

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Pausim said:
A chunky junction box on the negative should do. I found I needed one on the positive because of wire length to the B2B.
Click to expand...

That would be perfect as I can keep everything under the passenger seat and leave room for a second lithium if I ever need one.
 
Googlebot said:
That said, what about the solar? Will that damage it being on charge below freezing?
Click to expand...
I 've been searching numerous threads for the answer. Found the question, whats the answer?
Anybody use a heater to warm up the batery. Does a 12v version exist of a brewers belt used to heat a mash tun.
I know that last idea is off the wall.
 
Any method of charging, including solar, will harm a lithium battery if it's zero degrees C or lower. It's preferable that each charging device has a temperature sensor, and is smart enough to cut off when zero or lower.

Most batteries have a Battery Management System (BMS), either built-in or external, that will cut off charge if below zero. This should be regarded as a last-ditch measure, in case the charger control software fails.

I believe some batteries/chargers have heater pads underneath, and the charge controller diverts charging power to the heater pads until the temperature is above zero. Some batteries even have the heater pads built-in.

Since lithium batteries do not give off gas like lead-acids, it is common to bring the batteries inside the habitation area, or at least inside the 'thermal envelope' in a winterised motorhome.

Some systems like Victron have a temperature sensor on one device, and send the data by Bluetooth or data wires to other charging devices. They make a stick-on temperature sensor that sends temperature and voltage data by Bluetooth.
 
Lenny HB said:
If you fit the optional temperature sensor on your Votronic regulator it will prevent charging below zero on the Lithium setting.
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I have indeed got two Lenny.

Not cheap but cheaper than a new lithium battery.

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Thanks for answers, got a votronics charger as well, answers slowly coming together.
I was thinking a arduino controlled relay.
 
the1andonly said:
Thanks for answers, got a votronics charger as well, answers slowly coming together.
I was thinking a arduino controlled relay.
Click to expand...

I am using the EBL that’s already there.

This is the sensor I got for the Votronic.

Votronic, MPPT Duo Digital charge controller with accessories Amazon product ASIN B00C6602BI
 

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