Mix and match batteries.
- Thread starter rALPHBF
- Start date
Don B. Cilly
Energetic energy padawan
Well, it depends what you want to do with them, doesn't it?
If you want to build a high-end, high-energy, teenage-daughter-proof, induction-cooker-capable, self-monitoring, AI-driven system ;·) it's probably not a good idea.
For a low-end, low-energy, common-sense, human-brain-monitored one, it's probably OK.
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If you want to build a high-end, high-energy, teenage-daughter-proof, induction-cooker-capable, self-monitoring, AI-driven system ;·) it's probably not a good idea.
For a low-end, low-energy, common-sense, human-brain-monitored one, it's probably OK.
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Wouldn't they simply be the last to fully charge?
Don B. Cilly
Energetic energy padawan
Yes, they're called Automatic Transfer Switches (ATS). They come in all flavours.
But they tend to belong more to the first category than to the second :·)
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But they tend to belong more to the first category than to the second :·)
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It should not be a problem at all. During charging the two banks will have the voltage increase exactly the same and within limits of the charger. You will see more current going into the larger capacity bank, this is not a problem.
During discharge you will also see the voltage exactly the same and have more current from the larger capacity bank, again this is not a problem.
During rest when not charging and not discharging you could have current from one bank to the other (depending on what your charger is doing, assuming off), over time this could drain one of the banks a bit. This is also something that occurs when you mix new and old batteries, or mix LifePo4 with SLA (Sealed Lead Acid) types. This is only a problem if that current is high enough and over a long enough time that you could loose some of the charge.
I do this and I monitor the power in and out of each bank.
Randy
During discharge you will also see the voltage exactly the same and have more current from the larger capacity bank, again this is not a problem.
During rest when not charging and not discharging you could have current from one bank to the other (depending on what your charger is doing, assuming off), over time this could drain one of the banks a bit. This is also something that occurs when you mix new and old batteries, or mix LifePo4 with SLA (Sealed Lead Acid) types. This is only a problem if that current is high enough and over a long enough time that you could loose some of the charge.
I do this and I monitor the power in and out of each bank.
Randy
Nope - especially with GEL, which is very CV voltage sensitive. (14.1v MAX and temperature compensated) You'll be mixing old and new, and blowing out the vents or bulging in process. This will happen in time as the mismatched capacity cells, the 150's, never really get fully charged and sulfate.
Oh sure, you can attempt this - but in the LONG RUN, this will cost you more as you replace batteries piecemeal, while the cost of lead keeps going up.
Much better to engineer and PLAN a replacement system with the capacity you actually need now.
Oh sure, you can attempt this - but in the LONG RUN, this will cost you more as you replace batteries piecemeal, while the cost of lead keeps going up.
Much better to engineer and PLAN a replacement system with the capacity you actually need now.
So Randy what do you think about substrate's reply
rALPHBF - whatever Randy thinks is fine - ultimately it is up to you.
Without detail, we can only provide off the cuff answers.
What is the exact make / model of your existing battery setup? Did you purchase new or used and at the same time? This will provide clues as to whether you are making the common mistake of not knowing the difference between gel and agm, which have different charging parameters - or if you have been hoodwinked by a salesman right from the start. (salesman tend to push that there is no difference when there in fact is!)
Also clues to your daily load consumption will help determine if you are simply over-taxing / under-charging your existing bank, and the addition of more batteries is just going to cost you more money.
But if you are just fishing to hear what you want to hear, then sure - go for it!
Without detail, we can only provide off the cuff answers.
What is the exact make / model of your existing battery setup? Did you purchase new or used and at the same time? This will provide clues as to whether you are making the common mistake of not knowing the difference between gel and agm, which have different charging parameters - or if you have been hoodwinked by a salesman right from the start. (salesman tend to push that there is no difference when there in fact is!)
Also clues to your daily load consumption will help determine if you are simply over-taxing / under-charging your existing bank, and the addition of more batteries is just going to cost you more money.
But if you are just fishing to hear what you want to hear, then sure - go for it!
I am assuming you will be adding 'gel' type batteries not AGM since your question was about mixing AH not battery type. If this is true then I assume you currently have a charge system designed for gel. Therefore adding a second bank the is gel should be fine.
If your original bank is rather old then the new batteries may be spending some energy supporting the old bank, this is something you will have to live with. The effect is you wont have a capacity equal to the sum of the two bank's AH, it would be less, and leaving them together for long periods could essentially bring your new batteries to the level of the old. You may want to monitor the AH out and the AH in for each bank. That will help to determine if your getting sufficient power from them. Perhaps a good old load test done on your current string to know how far off they are from the 100AH rating.
I wonder what your load is? Is it a short run of high current, or a longer lower current. If a high current then check the battery data sheet. You will see that you won't get the full AH when you have a high current load.
I will have LifePo4 in parallel with an AGM for my camper but I do not charge then together. I separate the battery banks and charge individually. I also would not leave the two connected for long periods. There are several options and various things to watch.
Don't be afraid to ask questions. I don't have all the answers and there are many others here who have good knowledge and experience.
Randy
If your original bank is rather old then the new batteries may be spending some energy supporting the old bank, this is something you will have to live with. The effect is you wont have a capacity equal to the sum of the two bank's AH, it would be less, and leaving them together for long periods could essentially bring your new batteries to the level of the old. You may want to monitor the AH out and the AH in for each bank. That will help to determine if your getting sufficient power from them. Perhaps a good old load test done on your current string to know how far off they are from the 100AH rating.
I wonder what your load is? Is it a short run of high current, or a longer lower current. If a high current then check the battery data sheet. You will see that you won't get the full AH when you have a high current load.
I will have LifePo4 in parallel with an AGM for my camper but I do not charge then together. I separate the battery banks and charge individually. I also would not leave the two connected for long periods. There are several options and various things to watch.
Don't be afraid to ask questions. I don't have all the answers and there are many others here who have good knowledge and experience.
Randy
I love the truth. Not what someone has read or simply believes is true. Red bud seems to speak from personal experience and is doing it now
I am not the kind of guy who seeks confirmation of what I already believe, there is no personal growth in that.
So this is what I have decided to do. I am going to buy 4 more 100ah batteries and install them in parallel with my main battery bank..
It seems like it would just less hassle and I would not be saving that much money, and if necessary I can add a 3rd battery bank.
I only have 550w of PV. That can actually run my whole house and charge the batteries on a sunny day.
I plan on adding 400ah and increasing my PV to 1100w.
I have a 40amp SREN charge controller and a 24v Snat inverter.
My batteries are 4 months old and I will be adding the batteries on May 1st and two more panels shortly after that.
The 150ah batteries would of given me a little extra cushion but it is what it is.
I am not the kind of guy who seeks confirmation of what I already believe, there is no personal growth in that.
So this is what I have decided to do. I am going to buy 4 more 100ah batteries and install them in parallel with my main battery bank..
It seems like it would just less hassle and I would not be saving that much money, and if necessary I can add a 3rd battery bank.
I only have 550w of PV. That can actually run my whole house and charge the batteries on a sunny day.
I plan on adding 400ah and increasing my PV to 1100w.
I have a 40amp SREN charge controller and a 24v Snat inverter.
My batteries are 4 months old and I will be adding the batteries on May 1st and two more panels shortly after that.
The 150ah batteries would of given me a little extra cushion but it is what it is.
