Best Charge Controller for mixed battery types

SeedFarmer

New Member
Joined
Oct 31, 2021
Messages
18
I am trying to purchase a charge controller for a system that has two different batteries. One is a sealed lead-acid battery and one is a deep cycle Gel battery. When looking at solar charger reviews, it looks like the charger is supposed to be set to the type of battery that you have and there are different settings for a lead-acid battery and a Gel battery. The solar panels total 550 watts, so I am assuming a 60A controller is needed. Advice anyone?
 

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Texas-Mark

Solar Addict
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Aug 4, 2021
Messages
531
I've been running FLA and AGM batteries in parallel for years without issue. I have my charge controller set to 14.4V and they both seem to be happy. I disable any automatic equalization. I check the SG on the FLAs about once a month. For the AGMs I just individually check them with a load tester (sort of a PITA, but not much else you can do regardless of how they are configured).

I know some will say not to mix them, and it will shorten the life, etc. etc. But I'm not going to just toss perfectly good batteries just to have them all the same type. The same goes for different age batteries. I have already posted that I have up to a 4 year difference on my FLAs and they have not "cooked" or otherwise prematurely failed. I am a firm believer in proper battery maintenance being more important than what combination is being used. YMMV of course.
 

SeedFarmer

New Member
Joined
Oct 31, 2021
Messages
18
I've been running FLA and AGM batteries in parallel for years without issue. I have my charge controller set to 14.4V and they both seem to be happy. I disable any automatic equalization. I check the SG on the FLAs about once a month. For the AGMs I just individually check them with a load tester (sort of a PITA, but not much else you can do regardless of how they are configured).

I know some will say not to mix them, and it will shorten the life, etc. etc. But I'm not going to just toss perfectly good batteries just to have them all the same type. The same goes for different age batteries. I have already posted that I have up to a 4 year difference on my FLAs and they have not "cooked" or otherwise prematurely failed. I am a firm believer in proper battery maintenance being more important than what combination is being used. YMMV of course.
Thanks for the reply! These batteries are in central Africa, so my options are very limited. I will work toward getting two batteries of the same type in the future, but in the meantime, can you recommend a controller? This system has three solar panels totaling 550 watts, so I assume I need a 60A controller. Unfortunately, all three solar panels are also different brands, etc. The currently installed controller has no indication of its capacity and so I thought I would replace the controller since I know something is not right with this installation. Since these are both sealed batteries, what maintenance do you recommend on the batteries?
Do not suggest you mixed them together.
 

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mikefitz

Photon Sorcerer
Joined
May 28, 2020
Messages
1,291
there are different settings for a lead-acid battery and a Gel battery. The solar panels total 550 watts,
Use the lead acid settings. Not super ideal but the best you can do with what is available.

The panels are mismatched and in no way will produce the 550 watts. The solar controller is a PWM unit, this type will only allow the panel current into the batteries not the panel power. The 3 panels are, 36volts 5.5 amps,18 volts 8 amps, 24 volts 8 amps. Thus the most you can expect is 5.5 + 8 + 8 = 21.5 amps. The controller is rated at 40 amps. PWM40, the 40 is the rated maximum current.
Assuming the battery is charging at 13.5 volts the power into the batteries is 290 watts.

Replacing the controller with a MPPT type and rewiring the panels, the two smaller ones in series and then in parallel with the large panel, would make more efficient use of the panel power. You wont get the full total power of 550 watts due the the panel reduction in power when it gets hot, expect 450 or so watts. The MPPT solar controller would convert this to 33 amps into the battery.

Lead acid battery life , even if correctly charged and maintained, is reduced under high operating temperatures. From a distance its almost impossible to determine if the two batteries have useful life, as I suspect there is limited or non existent test equipment available. Some idea of battery age would be useful.

Reading your other post is seems you plan to ship more equipment including solar panels. The additional panels may influence the choice of controller.

I am a little confused as to the objective. I understand there is a AC fridge to be powered. Is there any low power lighting also powered from the battery.

An outline of the proposed system, existing and additional equipment to be used, funds available, would be helpful in offering advice.

This article may help,

Mike
 

SeedFarmer

New Member
Joined
Oct 31, 2021
Messages
18
Use the lead acid settings. Not super ideal but the best you can do with what is available.

The panels are mismatched and in no way will produce the 550 watts. The solar controller is a PWM unit, this type will only allow the panel current into the batteries not the panel power. The 3 panels are, 36volts 5.5 amps,18 volts 8 amps, 24 volts 8 amps. Thus the most you can expect is 5.5 + 8 + 8 = 21.5 amps. The controller is rated at 40 amps. PWM40, the 40 is the rated maximum current.
Assuming the battery is charging at 13.5 volts the power into the batteries is 290 watts.

Replacing the controller with a MPPT type and rewiring the panels, the two smaller ones in series and then in parallel with the large panel, would make more efficient use of the panel power. You wont get the full total power of 550 watts due the the panel reduction in power when it gets hot, expect 450 or so watts. The MPPT solar controller would convert this to 33 amps into the battery.

Lead acid battery life , even if correctly charged and maintained, is reduced under high operating temperatures. From a distance its almost impossible to determine if the two batteries have useful life, as I suspect there is limited or non existent test equipment available. Some idea of battery age would be useful.

Reading your other post is seems you plan to ship more equipment including solar panels. The additional panels may influence the choice of controller.

I am a little confused as to the objective. I understand there is a AC fridge to be powered. Is there any low power lighting also powered from the battery.

An outline of the proposed system, existing and additional equipment to be used, funds available, would be helpful in offering advice.

This article may help,

Mike
Thank you for your response! The objective for this system is to run some low voltage lighting in the evening, run an A/C refrigerator during the day, and if possible, add some USB device charging (which is currently only being done by generator in the evenings.) During the daytime there is very little low voltage use on this system. The low voltage lighting is used in the evening when the refrigerator is unplugged from the solar system and is running off a generator for a couple of hours. The refrigerator is not being powered at all during the night. Currently there are about 6 x 12volt x 7 watt light bulbs running directly off the charge controller in the evenings. I am not sure how that works since the sun is down by that time - must be back-feeding from the batteries. The batteries only have the one 1500 watt inverter on it which is running the 220volt 8 amp refrigerator during daylight hours with good sun. I am not an expert my any means, but these videos show the setup and me testing the inverter. I was afraid that the mixed panels would be an issue, but it sounds like I do not need a larger capacity charge controller, but rather a MPPT controller would help? Can you recommend a brand and/or a vendor?

I am fairly certain that the inverter is not working properly as you can see in my test on the below video. I would love to find a 3000 watt 220 volt 50 Hz single phase inverter to replace the current one.

I will not be taking solar panels or batteries from the US, just controllers and inverters. I will have to source the solar panels in Bangui, Central African Republic. Of the three panels currently installed, which one is the best - to obtain additional? Or, what should I look for in a solar panel if we obtain additional ones?

CAR solar system setup

Inverter test
 
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