Split charge relay capable of charging 360Ah Battery Bank?

[Vanlife Bandit UK]

Hi all, I'm looking to add another battery to my van and install a split charge relay. Currently I have 240Ah battery bank (2x 120Ah) + 400W solar in series (4x 100W) with 40A MPPT C/C. I want to add another battery (120Ah) to my set up making it 360Ah battery bank (all same AGM batteries) and add a split charge relay as well.
Question is; is there a split charge relay that will handle charging upto 360Ah battery bank? The ones I've seen charge upto 220Ah.
Another question would be; will my 400W solar + C/C be compatible with charging 360Ah battery bank?
I'm in the UK, it's autumn and the sun isn't great atm. I have quite a few energy hungry items that I want to keep in the van and go off grid as long as possible.
eg:
60W 60L fridge/freezer (wired into 12v battery via fuse box)
Video Editing/gaming PC w/ 2 screens
Laptop
Instant pot
Maxxfan Deluxe
and the usual lights etc.
I don't need the PC or instant pot on all the time but the freezer is on 24/7 and I'm finding the solar is struggling to recharge the energy used each day to where I'm not using the PC nor instant pot.
I have a Genius Noco 10 battery charger installed which is topping me up when parked near mains hook up but that is at max capacity for 240AH battery bank. I'd also need a better (more capable) battery charger if anyone konws of one. It's all expense.
Many thanks,
Si

 

[maki2]

Sounds like you need to get a generator either petrol or propane gas. You will need that alternate power source.

What you can not fix in the UK is how much solar input you will have during 9 months of the year fall, winter and spring. That is very much a climate like the costal Pacific NW in the USA where solar input is also very limited due to the sun being at a low angle in winter as well as having frequent cloudy weather.

If you can tilt your panels and and reposition your vehicle now and again during the day to track the sun’s position that will be a help for gaining as much solar input as possible.

Otherwise head to Southern Europe for the winter months.

 

[frater secessus]

Question is; is there a split charge relay that will handle charging upto 360Ah battery bank? The ones I've seen charge upto 220Ah.

There are larger relays, but that's not really the limitation IMO.

• AGM will typically draw 0.33C at 50% {State Of Charge} at normal alternator voltages. 0.33 x 360Ah = 120A draw from the alternator.
• Conservative continuous use of the alternator is ~1/3rd of rated output while driving, so this would require an alternator rated at 360A. Most aren't. Others are more confident in their alternators and might run them at ~1/2 of rated output while driving. This would require "only" a 240A alternator (still larger than most). There are aftermarket alternators that are designed to make decent current while idling, but they don't come that way from the factory. If your alternator is rated <240A a current-limiting DC-DC charger is warranted. { Tinkerers might consider adding resistance so the bank can't pull as much current. }
• variable-voltage (ie "smart") alternators are more common in Europe than the US. If yours is so equipped it will likely require a different approach.

Another question would be; will my 400W solar + C/C be compatible with charging 360Ah battery bank?

By itself it would be woefully underpaneled.

Reasoning: AGM has a minimum charging rate typically around 0.15C (between 0.1C and 0.2C) to stay healthy. 360Ah x - .15C = 54A. A 40A solar setup obviously cannot provide 54A.

Luckily the alternator can likely do 54A (assuming a rating of 150A or more, using the conservative numbers above).

In practice with alternator+solar best results come from driving when the bank is lowest (usually morning) and letting solar handle the higher-voltage late Absorption and Float stages.

I have a Genius Noco 10 battery charger installed which is topping me up when parked near mains hook up but that is at max capacity for 240AH battery bank. I'd also need a better (more capable) battery charger if anyone konws of one. It's all expense.

Because you have solar that is capable of staged (ie, "smart") charging, the most cost-effective solution may be a "dumb" (single voltage) converter/charger, as is common in RVs/caravans. It might only charge to float voltages, but refer to the alternator+solar section above. I'm seeing basic 60A converter/chargers on Amazon US for ~140USD.


{edited to inject missing words}

 

[tx2sturgis]

Bandit, welcome to the forum!

And when you find yourself in a hole, STOP digging.

Your 400 watts of panels are probably only able to produce (on average) 100-200 watts throughout part of a normal day, and this will go even lower as the season changes to winter.

Using lots of power and ramping up usage with a 2 screen PC and instapot and laptop and other items is not going to be resolved with just adding another battery.

You need to increase power PRODUCTION. Or you need to reduce power consumption. Simple as that.

Either more solar input (more panels, moving and tilted toward the winter sun) or daily access to shore power, or a couple of hours of small genset operation every morning. Or, as frater pointed out, vehicle alternator charging, if you are already driving for several hours each day.

Or...cut power to all non-critical loads as the afternoon becomes evening and the evening twilight is telling your batteries 'good night!'

 

[Vanlife Bandit UK]

Many thanks for all your replies, they have been very helpful.
I don't run all these electrical items all the time obviously, only when needed and with an eye on the amount of time I use the PC for eg. I also currently have access to mains power.
What I think I'm going to try is a DC to DC 30Amp Victron battery charger from the alternator. It will work with the set up I currently have and allow an extra 120Ah battery upgrade later if I feel the dual energy production is capable of fully charging them all. I'll check out that converter/charger and see how it all fits together.
At the end of the day, I want to be off grid for as long as possible. It's been a huge learning curve but I've got this far so far

Many thanks,
Si

 

[jonyjoe303]

How many amps are you getting from your solar panels? with my 365 watt panel I get up to 12 amps in winter when the sun is out, you should be getting something similar or higher with your 400 watts.
Measure the voltage at the battery terminals, you should be getting the batteries up to 14.4 volts with the solar. IF your not getting that you have voltage drop, you might have to compensate by raising the bulk voltage higher. If the batteries arent reaching 14.4 volts, they are being undercharged and won't give you good performance.
On my system I have a 365 watt panel charging 532ah of lithium batteries. I only run a fridge, laptop , swampcooler and even in winter thats all I need to keep the battery bank fully charge to 100 percent every day, I never used the alternator on my system.
400 watts of solar should be plenty as long as the battery is being fully charged every day. Thats my recommendation before you buy a split relay is to check the voltage at the battery terminals, make sure they are reaching 14.4 volts (or even higher for some agm's).
Depending on how much AH's your freezer is using per day, you can get a rough idea if the solar panels can keep up with it. On my system the fridge uses about 20 ah's a day in winter, my panels produce about 80ah's so they easily keep up with it plus my other devices I use. And since during the day the fridge is running off the panels you just need to account for the off solar hours.
The alternator will only fast charge the battery to about 80 percent then the amps start to taper off, you will still need the solar to fully charge to 100 percent, thats why its important the controller can get the terminals to 14.4 volts.

 

[Vanlife Bandit UK]

How many amps are you getting from your solar panels? with my 365 watt panel I get up to 12 amps in winter when the sun is out, you should be getting something similar or higher with your 400 watts.
Measure the voltage at the battery terminals, you should be getting the batteries up to 14.4 volts with the solar. IF your not getting that you have voltage drop, you might have to compensate by raising the bulk voltage higher. If the batteries arent reaching 14.4 volts, they are being undercharged and won't give you good performance.
On my system I have a 365 watt panel charging 532ah of lithium batteries. I only run a fridge, laptop , swampcooler and even in winter thats all I need to keep the battery bank fully charge to 100 percent every day, I never used the alternator on my system.
400 watts of solar should be plenty as long as the battery is being fully charged every day. Thats my recommendation before you buy a split relay is to check the voltage at the battery terminals, make sure they are reaching 14.4 volts (or even higher for some agm's).
Depending on how much AH's your freezer is using per day, you can get a rough idea if the solar panels can keep up with it. On my system the fridge uses about 20 ah's a day in winter, my panels produce about 80ah's so they easily keep up with it plus my other devices I use. And since during the day the fridge is running off the panels you just need to account for the off solar hours.
The alternator will only fast charge the battery to about 80 percent then the amps start to taper off, you will still need the solar to fully charge to 100 percent, thats why its important the controller can get the terminals to 14.4 volts.

Hi there jonyjoe303,
during July I know that the solar was bringing in over 20Amps but I can't remember the exact figures.
I've just been monitoring the solar panels this morning. At 10.30am 400W solar was bringing in 8.6A with battery at 13.4V. Fridge/freezer (60W) has been on all night.
It's a sunny autumn morning here in the UK. Between 10:30am and 12pm the highest solar input was 13.2 Amps and by 12pm the batteries were sitting at 14.4V. The only power draw being the fridge/freezer. The highest I've seen the battery voltage is 14.7V when plugged into the mains. So I would say that voltage drop isn't a problem.
I'll have to look into what the freezer is drawing per day and what the solar is bringing in per day to. I know that the freezer uses 0.5A when cycling on but drops to 0.038A when dormant. It cycles throughout the day/night.
The DC to DC (30A) Victron charger will charge upto 100% apparently, so I may install one of those. If that dual energy production really works then I will probably fit another 120Ah battery to help with staying off grid for longer. I'm sat here in a SWB medium high top Ford Transit so space is a premium. I may take out the 2nd screen (it's a luxury when editing though) Each moniter uses around 0.16A.
I've just noticed though that the extension from my inverter is feeding power to all the devices that are plugged in even if powered off for eg: my monitor was drawing 0.025A and it's not on. So that's a thing to remember: switch off inverter when not in use.
I appreciate your time/effort in writing your reply. I've defo learnt a few things here.

This is the first year being partially in the van during an incomplete (in progress) conversion so this is about ironing out any creases as it were.
Si

 

[frater secessus]

At the end of the day, I want to be off grid for as long as possible

It can be indefinite, as long as loads (including charging) and power generation are balanced. I have been off-grid 1,518 consecutive days in this campervan. Then again I have 2x the solar and no instant pot or gaming PC.

I also currently have access to mains power.

Having mains power is like winning the vanlife lottery. Enjoy!

by 12pm the batteries were sitting at 14.4V

You probably know this, but just in case: reaching absorption voltage doesn't mean lead batteries are charged; it means the long absorption stage has begun. It typically takes a few hours after that point to achieve full charge. ie, acceptance falling to ~2.4A for the existing 240Ah bank.

The DC to DC (30A) Victron charger will charge upto 100% apparently

Given sufficient hours of driving; see above.

If that dual energy production really works then I will probably fit another 120Ah battery to help with staying off grid for longer

Be careful; having more capacity than one can charge fully/regularly will kill lead-chemistry batteries prematurely. It is also considered good practice to not add new batteries to an old bank.

14.4V. The only power draw being the fridge/freezer. The highest I've seen the battery voltage is 14.7V when plugged into the mains. So I would say that voltage drop isn't a problem.

0.3v can be a huge difference when charging batteries. Both chargers should be configured so they make the battery manufacturer's Absorption setpoint voltage at the battery terminals, as @jonyjoe303 has correctly advised.

I'll have to look into what the freezer is drawing per day and what the solar is bringing in per day to. I know that the freezer uses 0.5A when cycling on but drops to 0.038A when dormant. It cycles throughout the day/night.

It may be more useful to think in watts; it gets around the problem of different voltages between AC and DC.

• 0.5A @ 12vdc (freezer is "wired into 12v battery via fuse box") = 6w. IMO that is an impossibly-low number for a freezer when the compressor is cycled on.
• 0.5A on an inverter is a different beast
  • 0.5A @ the 230vac UK mains standard would be 115w.
  • 0.5A @ 120vac (US mains standard) would be the 60w mentioned in the first post.

 

[frodo2222]

Hi there jonyjoe303,
during July I know that the solar was bringing in over 20Amps but I can't remember the exact figures.
I've just been monitoring the solar panels this morning. At 10.30am 400W solar was bringing in 8.6A with battery at 13.4V. Fridge/freezer (60W) has been on all night.
It's a sunny autumn morning here in the UK. Between 10:30am and 12pm the highest solar input was 13.2 Amps and by 12pm the batteries were sitting at 14.4V. The only power draw being the fridge/freezer. The highest I've seen the battery voltage is 14.7V when plugged into the mains. So I would say that voltage drop isn't a problem.
I'll have to look into what the freezer is drawing per day and what the solar is bringing in per day to. I know that the freezer uses 0.5A when cycling on but drops to 0.038A when dormant. It cycles throughout the day/night.
The DC to DC (30A) Victron charger will charge upto 100% apparently, so I may install one of those. If that dual energy production really works then I will probably fit another 120Ah battery to help with staying off grid for longer. I'm sat here in a SWB medium high top Ford Transit so space is a premium. I may take out the 2nd screen (it's a luxury when editing though) Each moniter uses around 0.16A.
I've just noticed though that the extension from my inverter is feeding power to all the devices that are plugged in even if powered off for eg: my monitor was drawing 0.025A and it's not on. So that's a thing to remember: switch off inverter when not in use.
I appreciate your time/effort in writing your reply. I've defo learnt a few things here.

This is the first year being partially in the van during an incomplete (in progress) conversion so this is about ironing out any creases as it were.
Si

Depend on your inverter the all draw a bit or a lot overnight ...the electrics that do have to be on will have fathom draws even when they are off by putting them on a power strip turning the strip off you will have the inverter on for the freezer but not be drawing any power on stuff that is turned off

 

[jonyjoe303]

The voltage readings you are getting off the solar controller? because 14.4 volts by noon might actually be voltage drop. The controller might be reading 14.4 volts and think the battery is full and reduce amps.
The panels putting out 13.2 amps is good, its what I usually get in winter, so your solar panels are capable of keeping your batteries charged up. You just got to keep the max amps going into your battery all day long. If the battery is switching into float mode too soon its another sign of voltage drop. You need to maintain 14.4 volts for several hours.

Here is a picture of extreme voltage drop when charging my 220ah lifepo4 with an ecoworthy 20 amp mppt.
The LED records the voltage right off the terminals, so its accurate 14.6 volts/15.1 amps. The ecoworthy controller has an LCD screen and its reading 15.5 volts. I had to set the bulk setting to 15.5 volts to get the battery terminals to reach 14.6 volts.

The ecoworthy mppt controller, like all controllers I used, were reading on the high side. At 14.4 volts, the terminals would be less than 14 volts. I even tried using thicker gauge wire but it didnt help, the controller calibration is off. I been using the makeskyblue 60 amp mppt, the voltage was off on that one too, but its the only controller I used that has the ability to calibrate the controller voltage to the battery terminals. Its very accurate once its calibrated.

 

[Vanlife Bandit UK]

Depend on your inverter the all draw a bit or a lot overnight ...the electrics that do have to be on will have fathom draws even when they are off by putting them on a power strip turning the strip off you will have the inverter on for the freezer but not be drawing any power on stuff that is turned off

The freezer is now wired into the 12v battery bank via the fuse box. I will be turning the extension off from now on though

 

[Vanlife Bandit UK]

Having mains power is like winning the vanlife lottery. Enjoy!

Thanks, it's while I'm on the drive finishing off the conversion, but not 24/7.

 

[Vanlife Bandit UK]

You probably know this, but just in case: reaching absorption voltage doesn't mean lead batteries are charged; it means the long absorption stage has begun. It typically takes a few hours after that point to achieve full charge. ie, acceptance falling to ~2.4A for the existing 240Ah bank.

No, I didn't know this although I was vaguely aware of some graph I saw recently but then forgot about. Makes sense. I've noticed though that as soon as the sun goes behind a cloud the amps drop and so does the battery voltage. I think this then explains what you're saying above.

 

[Vanlife Bandit UK]

Be careful; having more capacity than one can charge fully/regularly will kill lead-chemistry batteries prematurely. It is also considered good practice to not add new batteries to an old bank.

My batteries are only 2.5 months old, I'm not sure that they would be considered old atm but I understand.

 

[Vanlife Bandit UK]

0.3v can be a huge difference when charging batteries. Both chargers should be configured so they make the battery manufacturer's Absorption setpoint voltage at the battery terminals, as @jonyjoe303 has correctly advised.

Shortly after I posted yestday the batteries reached 14.7V. They didn't stay there for too long but they got there.

 

[Vanlife Bandit UK]

It may be more useful to think in watts; it gets around the problem of different voltages between AC and DC.

• 0.5A @ 12vdc (freezer is "wired into 12v battery via fuse box") = 6w. IMO that is an impossibly-low number for a freezer when the compressor is cycled on.
• 0.5A on an inverter is a different beast
  • 0.5A @ the 230vac UK mains standard would be 115w.
  • 0.5A @ 120vac (US mains standard) would be the 60w mentioned in the first post.

Yes, the 0.5A was measured when the freezer was plugged into either my inverter or mains can't remember which. I've since wired the freezer into my battery bank via the fuse box. It's an Alpicool T60 (60L), advert says 60W. When I was looking for a fridge/freezer for the van, I was only thinking about the internal capacity plus the external dimensions. The energy draw of the unit for some reason completely eluded my scrutiny - ??? Brain cramp I think.
I like to cook so the capacity was important to be able to freeze etc. But with the UK autumn, solar is diminished and the freezer is on 24/7 it's beginning to stress the whole set up. Summer was fine. I'm just concerned that come winter the solar is gonna be nigh on zero and totally inadequate even for just the freezer, hense wanting to install the DC to DC charger (30A) and an extra 120AH.
Today for example, it's overcast and midday, the 400W solar is drawing in 4.5A, battery is on 13.4V. This morning at 7:45am it was drawing 0.1A at 12.5V.

 

[Vanlife Bandit UK]

The voltage readings you are getting off the solar controller? because 14.4 volts by noon might actually be voltage drop. The controller might be reading 14.4 volts and think the battery is full and reduce amps.
The panels putting out 13.2 amps is good, its what I usually get in winter, so your solar panels are capable of keeping your batteries charged up. You just got to keep the max amps going into your battery all day long. If the battery is switching into float mode too soon its another sign of voltage drop. You need to maintain 14.4 volts for several hours.

Here is a picture of extreme voltage drop when charging my 220ah lifepo4 with an ecoworthy 20 amp mppt.
The LED records the voltage right off the terminals, so its accurate 14.6 volts/15.1 amps. The ecoworthy controller has an LCD screen and its reading 15.5 volts. I had to set the bulk setting to 15.5 volts to get the battery terminals to reach 14.6 volts.

The ecoworthy mppt controller, like all controllers I used, were reading on the high side. At 14.4 volts, the terminals would be less than 14 volts. I even tried using thicker gauge wire but it didnt help, the controller calibration is off. I been using the makeskyblue 60 amp mppt, the voltage was off on that one too, but its the only controller I used that has the ability to calibrate the controller voltage to the battery terminals. Its very accurate once its calibrated.


View attachment 32926

Just after I posted yesterday at noon, the batteries went upto 14.7A. That's the highest I've seen them go. They didn't stay there long though. Here's a pic of the MT50 reading at 12:30pm today (overcast day).
I'm using 40A MPPT Epever Tracer C/C. I can't test the actual battery terminals atm as my multi meter has died, I need a replacement or new batteries.
So, let me try and understand this correctly; voltage drop is when the C/C is reading the batteries at a higher Voltage value than what they actually are. To rectify that, you need to change the bulk settings in the C/C (increase V value) to compensate. Is that correct?

 

[Vanlife Bandit UK]

It can be indefinite, as long as loads (including charging) and power generation are balanced. I have been off-grid 1,518 consecutive days in this campervan. Then again I have 2x the solar and no instant pot or gaming PC.

That's impressive I can't add any more solar panels but I can include the DC to DC charger.

 

[jonyjoe303]

So, let me try and understand this correctly; voltage drop is when the C/C is reading the batteries at a higher Voltage value than what they actually are. To rectify that, you need to change the bulk settings in the C/C (increase V value) to compensate. Is that correct?

yes, when you get a multimeter verify the voltage on the terminals. If the MT50 LCD is reading 13.6 volts the battery terminal have to be 13.6 volts also. If the battery terminals are 13.2 volts, then you have a .4 volts voltage drop, you compensate by raising the bulk voltage by .4 volts (from 14.4 volts to 14.8 volts) and just keep checking it at various times, sometimes you have to adjust it several times to get it right. The only correct battery voltage is directly from the terminals with a multimeter or some meter (that is verified to read accurate) the controller MT50 LCD is usually not reading accurately unless verified with a multimeter.

By raising the bulk voltage you increase the amps going into the battery. On my Lifepo4 system (14.6 volts max) at bulk setting of 14.2 volts I get 8 amps, at 14.4 volts I get 10 amps, at 14.6 volts I get 12 amps. I can adjust how far I want the battery to be charged, at 14.2 volts it will never reach full charge but its a good setting when In summer and I don't use too much power. At 14.6 volts I can fast charge the battery and it will usually activate the BMS, I rarely keep it 14.6 volts unless its cloudy and need max amps. I usually have it at 14.4 volts, where it gets the battery up to about 95 percent.

On an AGM lead acid You need it at 14.4 volts to fast charge at all times, they require full charge everytime. Some AGM's might actually need 14.7 volts. I have a fullriver 27ah agm that requires 14.7 volts, charging it at 14.4 volts won't top it off. On the side of the battery it might say the max voltage, if yours say 14.4 to 14.7 volts, go with the max.

 

[Vanlife Bandit UK]

yes, when you get a multimeter verify the voltage on the terminals. If the MT50 LCD is reading 13.6 volts the battery terminal have to be 13.6 volts also. If the battery terminals are 13.2 volts, then you have a .4 volts voltage drop, you compensate by raising the bulk voltage by .4 volts (from 14.4 volts to 14.8 volts) and just keep checking it at various times, sometimes you have to adjust it several times to get it right. The only correct battery voltage is directly from the terminals with a multimeter or some meter (that is verified to read accurate) the controller MT50 LCD is usually not reading accurately unless verified with a multimeter.

By raising the bulk voltage you increase the amps going into the battery. On my Lifepo4 system (14.6 volts max) at bulk setting of 14.2 volts I get 8 amps, at 14.4 volts I get 10 amps, at 14.6 volts I get 12 amps. I can adjust how far I want the battery to be charged, at 14.2 volts it will never reach full charge but its a good setting when In summer and I don't use too much power. At 14.6 volts I can fast charge the battery and it will usually activate the BMS, I rarely keep it 14.6 volts unless its cloudy and need max amps. I usually have it at 14.4 volts, where it gets the battery up to about 95 percent.

On an AGM lead acid You need it at 14.4 volts to fast charge at all times, they require full charge everytime. Some AGM's might actually need 14.7 volts. I have a fullriver 27ah agm that requires 14.7 volts, charging it at 14.4 volts won't top it off. On the side of the battery it might say the max voltage, if yours say 14.4 to 14.7 volts, go with the max.

Many thanks for the info, I didn't have this down at all but now I'm getting it. When I get the multimeter up and running again, I'll let you know what the readings are just for resolution. Thanks again for your help (and everyone else's who have commented on this thread.
Si