Solar/Battery problem

Jul 23, 2022
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I recently purchased and installed a 340W solar panel kit along with a charge controller and then later a 100Ah lithium battery. I initially tried running it with our 75Ah lead acid battery but got too close to running the battery below 50% both evenings we tested it so went for a 100Ah lithium. I also added a 300W pure sine inverter for the laptop and changed the 10W halogen bulbs for 1.2W LEDs in the lighting at the same time as the battery upgrade.

Fridge and hot water are on gas so it’s the whale water pump, LED lighting and inverter keeping a laptop charged. We’re charging phone, ipad etc via USBs on the charge controller in the morning when we have some solar energy coming through.

I thought the 100Ah lithium would give us a lot more usable energy than the 75Ah lead acid battery, approximately 3 times the amount so comfortably make it through an evening, however the first night I tried the new setup I was back to low battery and battery anxiety by 9pm, the voltage had dropped from 14.5 to 13.0 in the space of 2 hours using 4 1.2W lights and occasional water running for rinsing cups etc.

In the morning we were back up to 13.3, it’s been a fairly cloudy day so wasn’t expecting a quick charge. It’s been up and down 13.9 one time I checked it then back down to 13.5 the next. Running the water seems to make the battery voltage drop pretty quickly.

Totally new to solar so this may be just a bit of anxiety on my part. My fear is that I have a duff battery. My question is does anyone here have a similar experience and also is there an easy, quantifiable way to test battery health?
 
Mar 3, 2022
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I've no experience of lithium batteries.
Our setup is a 115ah lead acid battery hooked up to 2 solar panels, 1 x 100 watt + 1 x 50 watt.
Water pump, lights, radio, TV, phone chargers etc all run off 12 volt.
I take a cheap inverter purely to charge up the battery on my wife's mobility scooter.
This time of year the battery is normally fully charged by 10 AM.
I check with a multi meter and generally shows about 14.2 volts when charging dropping to around 12.8 volts when resting.
 
Sep 29, 2016
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I recently purchased and installed a 340W solar panel kit along with a charge controller and then later a 100Ah lithium battery. I initially tried running it with our 75Ah lead acid battery but got too close to running the battery below 50% both evenings we tested it so went for a 100Ah lithium. I also added a 300W pure sine inverter for the laptop and changed the 10W halogen bulbs for 1.2W LEDs in the lighting at the same time as the battery upgrade.

Fridge and hot water are on gas so it’s the whale water pump, LED lighting and inverter keeping a laptop charged. We’re charging phone, ipad etc via USBs on the charge controller in the morning when we have some solar energy coming through.

I thought the 100Ah lithium would give us a lot more usable energy than the 75Ah lead acid battery, approximately 3 times the amount so comfortably make it through an evening, however the first night I tried the new setup I was back to low battery and battery anxiety by 9pm, the voltage had dropped from 14.5 to 13.0 in the space of 2 hours using 4 1.2W lights and occasional water running for rinsing cups etc.

In the morning we were back up to 13.3, it’s been a fairly cloudy day so wasn’t expecting a quick charge. It’s been up and down 13.9 one time I checked it then back down to 13.5 the next. Running the water seems to make the battery voltage drop pretty quickly.

Totally new to solar so this may be just a bit of anxiety on my part. My fear is that I have a duff battery. My question is does anyone here have a similar experience and also is there an easy, quantifiable way to test battery health?

You should be able to use 80% - 90% of your lithium battery capacity without concerns. In the event of low voltage the battery BMS will prevent the battery from over discharge.

I would avoid using the inverter for your laptop as this wastes energy coverting DC to AC.

Purchase something like this (I paid £29 so shop around) and run your laptop from a 12v DC outlet, run as many appliances as you can via the 12v outlet such as 12v TV.

Your water pump will use very little power, and you can also charge your phones via a 12v outlet.

I assume you have an MPPT controller, MPPT would be most appropriate for your setup.

Set the parameters on your MPPT to the reqirements of your battery (a rather important aspect of maintaining the longevity of your lithium battery), most good MPPT controllers will have the option of bluetooth or wifi connection to your phone from which you can both monitor and adjust settings.

I use bluetooth on my system and it only cost around £20.00.

You may also want to invest in a battery temperature sensor (£6.00) on my EPEVER MPPT setup, very worthwhile.

Assuming your battery is functioning properly then you should have good capacity and very little to cause you concern.
 
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Jul 23, 2022
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Hi, thank you for the reply. I have a solar charge controller that came with the solar panels, it seems quite basic. There is only one button and it displays volts with a simple picture showing the panels, battery and a light bulb which can indicate the charging status.

My caravan laptop is old so won’t run on 12v but I have seen battery packs available that charge on 12v and will charge the laptop so might try one of those, or maybe upgrade to a 12v tv. I hadn’t realised the inverter was going to take as much power as it does. I got the battery back to 14.5v, put the laptop on charge and it dropped down to 13.5v, I honestly thought the 100Ah battery was going to comfortably cope with our needs for more than one day.

Please can you give me some more information on the Bluetooth and temperature sensor?
 

JTQ

May 7, 2005
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Is the solar controller one designed for a Lithium battery, and set up to that mode?
Have you ever charged the battery? You can't get out AHs that are not already there, LA or Lithium technology.
The quoted voltages, unless having been off charge or off load for some time are no real guide to how "full" any battery may be; more an indication of the charge being in process.
Measuring Amps going in would be a lot more valuable to know things are functioning as they ought. The same tool can be used to check how much things drain from the battery. [well those up to 20 Amp loads]

Something like THIS is a very convenient means to measure currents, if you have a standard blade fuse protecting the controller/battery.
 
Jun 16, 2020
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You should be able to use 80% - 90% of your lithium battery capacity without concerns. In the event of low voltage the battery BMS will prevent the battery from over discharge.

I would avoid using the inverter for your laptop as this wastes energy coverting DC to AC.

Purchase something like this (I paid £29 so shop around) and run your laptop from a 12v DC outlet, run as many appliances as you can via the 12v outlet such as 12v TV.

Your water pump will use very little power, and you can also charge your phones via a 12v outlet.

I assume you have an MPPT controller, MPPT would be most appropriate for your setup.

Set the parameters on your MPPT to the reqirements of your battery (a rather important aspect of maintaining the longevity of your lithium battery), most good MPPT controllers will have the option of bluetooth or wifi connection to your phone from which you can both monitor and adjust settings.

I use bluetooth on my system and it only cost around £20.00.

You may also want to invest in a battery temperature sensor (£6.00) on my EPEVER MPPT setup, very worthwhile.

Assuming your battery is functioning properly then you should have good capacity and very little to cause you concern.

Sounds a similar system to mine. I also have the temp sensor but with the WiFi controller, not the BT. I am still to use it seriously off grid.

9B699048-12CE-47AA-9B80-0E7CD062AD49.jpeg


John
 
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Sep 29, 2016
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Hi, thank you for the reply. I have a solar charge controller that came with the solar panels, it seems quite basic. There is only one button and it displays volts with a simple picture showing the panels, battery and a light bulb which can indicate the charging status.

My caravan laptop is old so won’t run on 12v but I have seen battery packs available that charge on 12v and will charge the laptop so might try one of those, or maybe upgrade to a 12v tv. I hadn’t realised the inverter was going to take as much power as it does. I got the battery back to 14.5v, put the laptop on charge and it dropped down to 13.5v, I honestly thought the 100Ah battery was going to comfortably cope with our needs for more than one day.

Please can you give me some more information on the Bluetooth and temperature sensor?

You don't say if you have a caravan or a motorhome.

Most caravans will not have an appropriate onboard charger that is suitable for LifePo4.

If a motorhome, then the battery to battery charger should be of a type suitable for lithium batteries.

An MPPT controller that has options for battery management is essential for your setup. Using solar and the correct type of MPPT with the correct parameters assigned will ensure that your battery is properly maintained and protected to give good life expectancy, anything less and your expensive battery will be neither optimised or long lived.

Similarly, an icorrect type of onboard or BtoB battery charger will be detrimental to the health of your battery.

I can recommend EPEVER as a brand (That is the only one I have used), Victron Energy brand is highly regarded, if rather expensive.

Which ever controller brand you purchase, you should be able to enhance performance with various add-ons sold by the manufacturer.
e.g. battery temeperature sensor, a wi-fi or bluetooth module that will link to phone\laptop giving you live data and the option to change parameters remotely.

A separatey mounted display\control panel is also available for mounting at a convenient location in your vehicle.

I suggest that you look at the various equipment options from manufacturers, I would suggest a 30amp controller for your setup.

Suitable cabling, isolator switch and fusing is essential.

Hoping this helps.
 
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Jul 23, 2022
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You don't say if you have a caravan or a motorhome.

Most caravans will not have an appropriate onboard charger that is suitable for LifePo4.

If a motorhome, then the battery to battery charger should be of a type suitable for lithium batteries.

An MPPT controller that has options for battery management is essential for your setup. Using solar and the correct type of MPPT with the correct parameters assigned will ensure that your battery is properly maintained and protected to give good life expectancy, anything less and your expensive battery will be neither optimised or long lived.

Similarly, an icorrect type of onboard or BtoB battery charger will be detrimental to the health of your battery.

I can recommend EPEVER as a brand (That is the only one I have used), Victron Energy brand is highly regarded, if rather expensive.

Which ever controller brand you purchase, you should be able to enhance performance with various add-ons sold by the manufacturer.
e.g. battery temeperature sensor, a wi-fi or bluetooth module that will link to phone\laptop giving you live data and the option to change parameters remotely.

A separatey mounted display\control panel is also available for mounting at a convenient location in your vehicle.

I suggest that you look at the various equipment options from manufacturers, I would suggest a 30amp controller for your setup.

Suitable cabling, isolator switch and fusing is essential.

Hoping this helps.
That’s really helpful thank you. My charge controller does have a lithium battery mode, which I selected when I installed the new battery. I’ve now ordered a Bluetooth battery monitor.

I took on board the earlier comment about the inverter, I’m drawing a 240V/2A from the 12V battery then the laptop charger steps that down to 19V/4.74A, I think that could be as much as 50A on the 12V battery so it makes sense that it starts draining at an alarming rate when I’m charging the laptop, that is assuming I did understood the calculation properly. I’ve seen 12V laptop adaptors for sale online for around £30 so I’ll see if bypassing the inverter helps.
 
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Jun 16, 2020
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Hi John do you still have this set up and why the on off switches.
I have had to sell the van for health reasons. That was not my original controller. I had a cheap one from Hong Kong. However, the one in the picture is Chinese. The Epever has a good reputation. The extra wifi bit (there is also a Bluetooth option). I think is unnecessary. The screen provides enough settings without the need for further expense.

The switches are there for two reasons. one to disconnect the panels prior to working on the battery. Next to quickly see which panel is performing best.

John
 
Jul 4, 2023
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I have had to sell the van for health reasons. That was not my original controller. I had a cheap one from Hong Kong. However, the one in the picture is Chinese. The Epever has a good reputation. The extra wifi bit (there is also a Bluetooth option). I think is unnecessary. The screen provides enough settings without the need for further expense.

The switches are there for two reasons. one to disconnect the panels prior to working on the battery. Next to quickly see which panel is performing best.

John
Sorry to hear that John. I too struggle, but will carry on for as long as I can. Thanks for clarifying. All the best, Nick
 
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