Battery Charge Parameters

[HappyCampers]

Hi All, I'm hoping someone will be able to help with our MT50 Charge Controller and the correct charge parameters.
My partner and I are travelling around the UK in our Camper van and have recently upgraded the single 95AH battery to two 120AH batteries (NUMAX XV35MF 120AH, connected in parallel), The MT50 remote controller from what I've worked out only allows me to change the parameters if I select 'USER' in the battery type section. Unsure on what would be a safe selection for the remaining parameters on these type of batteries... Any help would be appreciated as I'm having no such luck receiving the info from the battery manufacturer.

- Over Volt. Disc.
- Charge limit
- Over Volt. Rec.
- Equal. Charge
- Boost Charge
- Float Charge
- Boost Rec.
- Low Volt. Rect.
- Under Volt Rect.
- Under Volt Warn.
- Low Volt. Disc
- Discharge Limit
- Equalise time
- Boost time

 

[sunshine_eggo]

Hi All, I'm hoping someone will be able to help with our MT50 Charge Controller and the correct charge parameters.

MT50 is a control unit. I presume you have an Epever MPPT?

My partner and I are travelling around the UK in our Camper van and have recently upgraded the single 95AH battery to two 120AH batteries (NUMAX XV35MF 120AH, connected in parallel), The MT50 remote controller from what I've worked out only allows me to change the parameters if I select 'USER' in the battery type section. Unsure on what would be a safe selection for the remaining parameters on these type of batteries... Any help would be appreciated as I'm having no such luck receiving the info from the battery manufacturer.

- Over Volt. Disc.
- Charge limit
- Over Volt. Rec.
- Low Volt. Rect.
- Under Volt Rect.
- Under Volt Warn.
- Low Volt. Disc
- Discharge Limit

all of the above have to do with the load port on the MPPT, and should only be modified if you have a specific reason to do so.

- Equal. Charge
- Boost Charge
- Float Charge
- Boost Rec.
- Equalise time
- Boost time

The above have to do with charging the batteries.

Given that you have no meaningful manufacturer information aside from identifying these as "sealed lead acid" batteries, there is no benefit to specifying anything but the "Sealed" option in the MPPT as the defaults are sensible for a "sealed lead acid" battery.

Do you have at least 300W of solar and a 30A MPPT charge controller?

 

[RussNM]

Thought these were lifepo4 hence the user defined... my bad. Are these lead acid batteries?

 

[HappyCampers]

Thanks for getting back to us so quickly.
Regarding the Solar Panel - Yes, I believe so, it's approx 2m x 1m if that gives any indication. The gear was installed prior to us purchasing the van.
The MT50 remote meter is connected to a 30A EPEVER TRIRON3210N MPPT Solar Charge Controller. We also have an Orion-Tr Smart Charger for the DC to DC charge.
I guess I'm just confirming the current parameters are correct for this type of set up, and if not what should I change them to?
The existing parameters are as follows...

- Batt. Type: Sealed
- Batt. AH: 240AH
- Temp Comp. Coeff: -3mv/C/2V
- Rated Voltage: 12V
- Over Volt. Disc.: 16V
- Charge limit: 15V
- Over Volt. Rec.: 15V
- Equal. Charge: 14.6V
- Boost Charge: 14.4V
- Float Charge: 13.8V
- Boost Rec.: 13.2V
- Low Volt. Rect.: 12.6V
- Under Volt Rect.: 12.2V
- Under Volt Warn.: 12V
- Low Volt. Disc.: 11.1V
- Discharge Limit: 10.6V
- Equalise time: 120min
- Boost time: 120min

When the car is turned on (first thing in the morning), the MT50 controller was showing the around 14.7V. Is this too high?

Thanks again for your help!

 

[HappyCampers]

Thought these were lifepo4 hence the user defined... my bad. Are these lead acid batteries?

Yes, I believe so. They are NUMAX XV35MF, so I selected "Sealed" type on the MT50 remote meter.

 

[HappyCampers]

Thanks for getting back to us so quickly.
Regarding the Solar Panel - Yes, I believe so, it's approx 2m x 1m if that gives any indication. The gear was installed prior to us purchasing the van.
The MT50 remote meter is connected to a 30A EPEVER TRIRON3210N MPPT Solar Charge Controller. We also have an Orion-Tr Smart Charger for the DC to DC charge.
I guess I'm just confirming the current parameters are correct for this type of set up, and if not what should I change them to?
The existing parameters are as follows...

- Batt. Type: Sealed
- Batt. AH: 240AH
- Temp Comp. Coeff: -3mv/C/2V
- Rated Voltage: 12V
- Over Volt. Disc.: 16V
- Charge limit: 15V
- Over Volt. Rec.: 15V
- Equal. Charge: 14.6V
- Boost Charge: 14.4V
- Float Charge: 13.8V
- Boost Rec.: 13.2V
- Low Volt. Rect.: 12.6V
- Under Volt Rect.: 12.2V
- Under Volt Warn.: 12V
- Low Volt. Disc.: 11.1V
- Discharge Limit: 10.6V
- Equalise time: 120min
- Boost time: 120min

When the car is turned on (first thing in the morning), the MT50 controller was showing the around 14.7V. Is this too high?

Thanks again for your help!

Additional, we have a 2500W Inverter.
Also, there is nothing connected to the load side of the MPPT Charge Controller.

 

[mikefitz]

MT50 controller was showing the around 14.7V. Is this too high?

The settings are OK for sealed lead acid. The Newmax XV35 are not realy intended for frequent deep cycle so don't discharge below around 12.0 volts, or use the inverter at high power for long periods.
14.7 volts under charge is no problem, is this being charged via AC shore power or solar?
Epever calibration is not always accurate. Note cold conditions will cause an increase in charge volts.

 

[sunshine_eggo]

When the car is turned on (first thing in the morning), the MT50 controller was showing the around 14.7V. Is this too high?

Defaults are fine. The 14.7 is likely the DC-DC charger. Worth checking battery voltage with a meter to confirm.

Additional, we have a 2500W Inverter.
Also, there is nothing connected to the load side of the MPPT Charge Controller.

2500/12/.85 = 245A - this requires some BEEFY cable. What cables are connecting your battery to inverter, and what fuse/breaker do you have in place?

The settings are OK for sealed lead acid. The Newmax XV35 are not realy intended for frequent deep cycle so don't discharge below around 12.0 volts, or use the inverter at high power for long periods.

@HappyCampers The 12.0 recommendation is sound, BUT it's VERY conservative. I wouldn't be surprised if the inverter at near max power pulls the batterybelow 12.0V within just a few minutes.

The better solution is to get a battery monitor like a Victron smartshunt that actually tells you the true state of charge and can factor in the Peukert exponent for capacity variance with load, i.e., the 240Ah is for pulling EXACTLY 12A from it. If you pull more than 12A, you get LESS than 240Ah. If you pull less than 12A, you get MORE than 240Ah. The Victron smartshunt takes this into consideration to improve it's calculation of the state of charge.

14.7 volts under charge is no problem, is this being charged via AC shore power or solar?
Epever calibration is not always accurate. Note cold conditions will cause an increase in charge volts.

@HappyCampers this is an important point. Lead acid charge voltage is for 77°F/25°C and changes with temperature - higher in cold, lower in hot. You either need to use temperature compensation, or you need to manually adjust the charge voltage.

 

[HappyCampers]

The settings are OK for sealed lead acid. The Newmax XV35 are not realy intended for frequent deep cycle so don't discharge below around 12.0 volts, or use the inverter at high power for long periods.
14.7 volts under charge is no problem, is this being charged via AC shore power or solar?
Epever calibration is not always accurate. Note cold conditions will cause an increase in charge volts.

Thanks Mike,
I've left only the DC fridge on tonight to see what would happen, though I believe we will drop below 12V with only the fridge running and I'm not sure why as I didn't think this would be considered a large load. (The inverter is OFF) - I'll confirm in the morning and revert.
The inverter is only 'usually switched on for charging laptops etc.
The 14.7 to 15V is from the DC to DC charger when the car is on.
Noted about the cold conditions - thanks. I'll invest in a meter when I can to check.

 

[HappyCampers]

Defaults are fine. The 14.7 is likely the DC-DC charger. Worth checking battery voltage with a meter to confirm.



2500/12/.85 = 245A - this requires some BEEFY cable. What cables are connecting your battery to inverter, and what fuse/breaker do you have in place?



@HappyCampers The 12.0 recommendation is sound, BUT it's VERY conservative. I wouldn't be surprised if the inverter at near max power pulls the batterybelow 12.0V within just a few minutes.

The better solution is to get a battery monitor like a Victron smartshunt that actually tells you the true state of charge and can factor in the Peukert exponent for capacity variance with load, i.e., the 240Ah is for pulling EXACTLY 12A from it. If you pull more than 12A, you get LESS than 240Ah. If you pull less than 12A, you get MORE than 240Ah. The Victron smartshunt takes this into consideration to improve it's calculation of the state of charge.



@HappyCampers this is an important point. Lead acid charge voltage is for 77°F/25°C and changes with temperature - higher in cold, lower in hot. You either need to use temperature compensation, or you need to manually adjust the charge voltage.

Thank you!

I'll invest in a meter and double check, I suspect it'll be handy to have on board regardless.

RE. the Inverter. There's a 50mm cable from the battery to a 250A protection device, then two 16mm cables connected in parallel from the protective device supplying the inverter.

Yes, I don't believe the inverter is the issue as we rarely use it, and when we do we only charge small loads. It'll be interesting to check tomorrow morning as the only device we deliberately left on is the DC fridge to see if we trigger any alarms, as we have had low voltage alarms previously.
The batteries were left to charge today with no load other than the fridge and the sun was out all day. It's 6.30pm now and the MPPT Controller is registering a battery level of 12.9V, 61%.
Am I correct in saying that two 120AH batteries at 61% should be able to solely run a DC fridge overnight with no low voltage issues?

Thanks for the recommendation re. the Victron smartshunt. I'll leave what the van has in place for now until I work things out and have aquired a greater understanding of the current system before making any mods.

 

[Suijkerbuijk]

Here are my setup with a epever
The best thing i have done is replace it for a Victron

WARNING THIS IS FOR LIFEPO4 BATTERY NOT FOR YOURS.

JUST USE THE PRESET FROM EPEVER FOR LEAD BATTERY.
That work just fine for your lead battery u use.

But see attach files

You see float that is 13.8 volts you can set that lower to 13.6volts
I use my float function to balance my cells that is a personal setup i use.

For the bulk time you can set that higher if you like to easy 4 hours .
Its just how long you need do to a full charge on your battery

 

[sunshine_eggo]

Thank you!

I'll invest in a meter and double check, I suspect it'll be handy to have on board regardless.

Yes.

RE. the Inverter. There's a 50mm cable from the battery to a 250A protection device, then two 16mm cables connected in parallel from the protective device supplying the inverter.

Wiring rated to UL1426 or BC5-W2 Boat Cable ABYC and USCG Approved for use on boats should be able to handle about 250A, so that's good.

Yes, I don't believe the inverter is the issue as we rarely use it, and when we do we only charge small loads. It'll be interesting to check tomorrow morning as the only device we deliberately left on is the DC fridge to see if we trigger any alarms, as we have had low voltage alarms previously.
The batteries were left to charge today with no load other than the fridge and the sun was out all day. It's 6.30pm now and the MPPT Controller is registering a battery level of 12.9V, 61%.

Unless 61% is being reported by a current-counting battery monitor, it's a mostly worthless number that has little to no meaning and should be ignored.

Did you witness your battery achieving 14.4V that day?

Am I correct in saying that two 120AH batteries at 61% should be able to solely run a DC fridge overnight with no low voltage issues?

No. First, if 61% is actually a real number, remember that for longevity, you don't want to run SLA batteries below 50%.

DC fridges may use a lot of power or they may not. If the DC fridge is also capable of burning propane for cooling (an absorption fridge), then it will use a huge amount of power. Some are thermo-electric. I have a 0.9 cu-ft cooler that consumes 60W @ 12VDC 0.9 that uses more energy than my 10.1 cu-ft AC fridge.

HOW MUCH ENERGY DOES YOUR DC FRIDGE CONSUME?

Thanks for the recommendation re. the Victron smartshunt. I'll leave what the van has in place for now until I work things out and have aquired a greater understanding of the current system before making any mods.

What does the van have in place? I haven't seen you indicate any battery monitoring whatsoever aside from the "61%". If that's reported by the MPPT, it's worthless.

It comes down to one question... Do you want to know the state of charge of your battery or not?

 

[mikefitz]

NUMAX XV35MF 120AH

More on these batteries, sold by many suppliers in the UK. They are really only suitable for light use , where the RV is mostly on shore power. Independent tests are not outstanding, cyclic use down to 50% capacity, with moderate loads, (20 amps per 100Ah) reported a cycle life of 200 to 250, deep discharged with higher loading gave less than 50 cycles. With a UK cost of £130 to £150 compared to around £200 for a budget 100 A lithium, they don't seem good value.

believe the inverter is the issue as we rarely use it, and when we do we only charge small loads

There are 12v input laptop and phone chargers that connect to the 12v system and are more efficient than using a 2500 watt inverter.

DC fridge on tonight to see what would happen,

If it's the common compressor fridge fitted to Euro RV, then it typicaly will run at 3 to 4 amps with a 30 % duty cycle. If the batteries are fully charged and a discharge to 50% is that aim . Then that's 120 Ah to use. Overnight the fridge will use in 12 hours at the very most 50 Ah, in reality with duty cycle, more like 15Ah or 7% of the battery bank

Controller is registering a battery level of 12.9V, 61%.

At 6.30 pm there may be still a bit of solar, but a voltage of 12.9 on a sealed battery can be considered full. The chart for a rested battery, no load or charge, is a rough guide. Idealy you want to stay in 'green'. The heaver the load the more the battery volts will 'sag', and under charge, the voltage will be elevated.

If you have been getting low battery warnings then I suspect the batteries are not being charged to full.
The area of panels suggest in the region of 400 watts of panel, at this time of the year expect 10 to 15 amps maximum around midday into the system, if you are in the south UK, less further north.
There are many issues that cause under charging, less than ideal install, poor performance from panels, ( especially flexible panels), Epever controller loosing maximum power mode, not enough sun hours to meet load requirements, underestimating time to fully charge lead batteries.